CYTOGEN CORP
S-3, 1999-07-20
IN VITRO & IN VIVO DIAGNOSTIC SUBSTANCES
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      As filed with the Securities and Exchange Commission on July 19, 1999
                              Registration No. 333-
 ==============================================================================
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549


                                    Form S-3
             REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933
                               CYTOGEN CORPORATION
             (Exact name of registrant as specified in its charter)

                                      2835
                      Delaware (Primary Standard 22-2322400
     (State or other jurisdiction Industrial Classification (I.R.S. Employer
       of incorporation or organization) Code Number) Identification No.)

                          600 College Road East CN 5308
                        Princeton, New Jersey 08540-5308
                                 (609) 750-8200
                        (Address, including zip code and
                    telephone number, including area code, of
                    registrant's principal executive offices)

                           Donald F. Crane, Jr., Esq.
                       Vice President and General Counsel
                               CYTOGEN Corporation
                          600 College Road East CN 5308
                        Princeton, New Jersey 08540-5308
                                 (609) 750-8200
                     (Name, address, including zip code, and
                    telephone number, including area code, of
                               agent for service)

        Approximate date of commencement of proposed sale to the public:
   As soon as practicable after this Registration Statement becomes effective.

     If any of the securities being registered on this Form are to be offered on
a delayed or continuous  basis  pursuant to Rule 415 under the Securities Act of
1933, check the following box: |_|

     If this Form is filed to  register  additional  securities  for an offering
pursuant to Rule 462(b) under the  Securities  Act,  check the following box and
list the Securities Act registration  statement number of the earlier  effective
registration statement for the same offering. |_| ____________

     If this Form is a post  effective  amendment  filed pursuant to Rule 462(c)
under the  Securities  Act,  check the following box and list the Securities Act
registration  statement number of the earlier effective  registration  statement
for  the  same  offering.  |_| ____________

     If this Form is a  post-effective  amendment  filed pursuant to Rule 462(d)
under the  Securities  Act,  check the following box and list the Securities Act
registration  statement number of the earlier effective  registration  statement
for the same  offering.  |_| ____________

     If delivery of the  prospectus is expected to be made pursuant to Rule 434,
please check the following box. |_|

                         CALCULATION OF REGISTRATION FEE

================================================================================
                                              Proposed Maximum
     Title of Each Class of                  Aggregate Offering      Amount of
  Securities To Be  Registered                     Price (1)    Registration Fee
Common Stock ($.01 par value per share)           $5,000,000          $1,390
================================================================================
(1)Estimated solely for the purpose of calculating the registration fee pursuant
to Rule 457(o).  Includes  preferred  stock purchase  rights pursuant to Cytogen
Corporation's Shareholder Rights Agreement.

     The registrant  hereby amends this  Registration  Statement on such date or
dates as may be necessary to delay its effective date until the registrant shall
file a further  amendment  which  specifically  states  that  this  Registration
Statement shall  thereafter  become effective in accordance with Section 8(a) of
the Securities  Act of 1933 or until this  Registration  Statement  shall become
effective on such date as the Commission,  acting pursuant to said Section 8(a),
may determine.

<PAGE>
                   Subject to Completion, dated July 19, 1999

PROSPECTUS
                                     Shares
                               CYTOGEN CORPORATION
                                  Common Stock

         This  prospectus  relates to the sale by CYTOGEN  Corporation  of up to
3,500,000 shares of our common stock. We plan to offer these shares to The State
of Wisconsin Investment Board (the "Principal Offeree").

         Our common  stock is listed on the Nasdaq Stock Market under the symbol
"CYTO."  The last sales  price of our common  stock as reported by the Nasdaq on
July 16, 1999 was $1.813 per share.

         Investing  in  the  common  stock  involves  certain  risks  which  are
described in the "Risk Factors" section beginning on page 6 of this prospectus.

         The  information in this prospectus is not complete and may be changed.
We may not sell these securities until the registration statement filed with the
Securities and Exchange Commission is effective. This prospectus is not an offer
to  sell  these  securities  and it is not  soliciting  an  offer  to buy  these
securities in any state where the offer or sale is not permitted.

         Neither the Securities and Exchange Commission nor any state securities
commission  has approved or disapproved  these  securities or determined if this
prospectus  is truthful or  complete.  Any  representation  to the contrary is a
criminal offense.


- --------------------------------------------------------------------------------
                                            Per Share                Total
- --------------------------------------------------------------------------------
Public offering price.................                               $5,000,000

Underwriting Discount.................

Proceeds to the Company...............
- --------------------------------------------------------------------------------


     CYTOGEN's principal executive offices are located at 600 College Road East,
CN 5308, Princeton, New Jersey 08540-5308, (609) 750-8200.





_________________ ____, 1999

<PAGE>






                                TABLE OF CONTENTS

                                                                           Page
Prospectus Summary......................................................    3
Risk Factors............................................................    6
Price Range of Our Common Stock.........................................   19
Dividend Policy.........................................................   19
Use of Proceeds.........................................................   19
Where You Can Find More Information.....................................   20
Plan of Distribution....................................................   22
Legal Matters...........................................................   24
Experts.................................................................   24

                           --------------------------










     ProstaScint  and OncoScint are registered  trademarks of CYTOGEN.  PIE is a
trademark  of CYTOGEN,  pending  registration.  Quadramet is a trademark of Dow,
licensed to CYTOGEN.


                                       2
<PAGE>



                               PROSPECTUS SUMMARY

     This summary highlights information contained elsewhere in this prospectus.
It is not  complete  and may not  contain  all the  information  that you should
consider  before  investing  in the common  stock.  You  should  read the entire
prospectus carefully, including the "Risk Factors" section.

The Company

     CYTOGEN  Corporation  ("CYTOGEN" or the  "Company") is a  biopharmaceutical
company engaged in the development,  commercialization and marketing of products
to improve  diagnosis and treatment of prostate  disease,  of products for unmet
needs in the broader  urological and oncology markets.  CYTOGEN was incorporated
in Delaware in 1981. Unless the context otherwise indicates, as used herein, the
term "Company" refers to CYTOGEN and its subsidiaries, taken as a whole.

Our Products

     We introduced to the market during 1997 our two principal products, each of
which have been approved by the U.S. Food and Drug Administration ("FDA"):

     -    ProstaScint(R)  (kit for the  preparation  of  Indium  In111  Capromab
          Pendetide).

               ProstaScint  has been approved as a diagnostic  imaging agent for
               prostate  cancer,  the most frequently  diagnosed  malignancy and
               second  leading  cause of  cancer  death in men.

     -   Quadramet(R) Samarium  Sm153  Lexidronam   Injection).

               Quadramet has been approved for the treatment of bone pain due to
               cancers  that  have  spread  to  the  skeleton  and  that  can be
               visualized on a bone scan.

     Our  OncoScint(R)  CR/OV  imaging  agent is also approved and marketed as a
diagnostic imaging agent for colorectal and ovarian cancer.

     We believe  that our  products  represent a  significant  improvement  over
existing   technologies   because  our  products  provide  improved   diagnostic
information  and/or  treatment in a  site-specific  manner with  relatively  low
levels of toxicity.

     We also develop other products and technologies,  both directly and through
subsidiaries, and have engaged in development efforts with other parties.

     Our primary products in development are:

          - Vaccines for  prostate and other  cancers  utilizing  the  Company's
          proprietary  prostate  specific  membrane  technology,  or PSMA,  in a
          collaboration with Progenics Pharmaceuticals, Inc.;

          - Other potential diagnostic and therapeutic applications of PSMA; and

          - A  bioinformatics  platform  designed  to offer a  database  mapping
          interaction  between proteins to be accessed by a computer program for
          use in drug discovery and research.

Research and Development

     Historically,  we have emphasized research and development of a broad array
of potential  products,  based on monoclonal  antibodies and other technologies.
Having identified and commercialized  products which we believe have substantial
potential, we have:

<PAGE>

          -  Conducted  or  sponsored  clinical  studies  to  evaluate  existing
          products  in  additional  indications;

          - Focused  on  development  of  technology  with near term  commercial
          significance; o Reviewed all current research and development programs
          to assess their commercial  potential;  and

          - Recently curtailed basic research  expenditures in order to allocate
          resources toward implementing our business strategy.

Business Strategy

     Our business strategy is directed  primarily toward prostate and urological
diseases and, when opportunities  arise, in the broader field of oncology and in
diagnostics.  We plan to focus our efforts in areas in which we have experience.
Our approach calls for:

          - Devoting our primary  efforts to the  marketing of  ProstaScint  and
          Quadramet to increase revenue and achieve profitability;

          - Expanding  the use of  ProstaScint  and other  products into foreign
          markets;

          - Developing products utilizing our proprietary technology;

          -  Expanding  our current  product  portfolio  through  the  continued
          in-licensing of additional products and related  technologies,  in the
          same manner as Quadramet;

          - Establishing strategic alliances;

          - Acquiring  other companies with related or  complementary  products,
          technologies and/or services.

     We cannot predict,  however,  whether we can accomplish these objectives or
whether  accomplishment of these objectives will lead to new commercially viable
products or  technologies.  In  addition,  our efforts to develop or acquire new
products depend on our available  resources,  our ability to commit resources to
potential  products or strategic  activities  without unduly  impacting  current
operations or financial results,  and whether or not such activities in the near
term would affect the  marketing of our products or the efforts of management to
commercialize the Company successfully.

Restructuring Activities

     During 1998 and early 1999,  we reviewed our assets and business  prospects
to determine  which  projects  demonstrated  adequate  potential for a continued
investment of corporate resources.  As a result of this review, we:

          - Terminated our ALT program.
               Our subsidiary  Cellcor,  Inc.  ("Cellcor")  had been  developing
               Autologous  Lymphocyte  Therapy  ("ALT")  for  the  treatment  of
               metastatic  renal cell  carcinoma  ("mRCC"),  a life  threatening
               kidney cancer for which there are no adequate  therapies.  We had
               planned  to  submit  a  Biologics  License  Application  for ALT.
               Cellcor  completed  pivotal  Phase III clinical  trials of ALT in
               mRCC patients in January 1997. Although we believe the results of
               the trials are  favorable,  ALT was not considered a priority for
               allocation of available resources.  We halted our preparation for
               submission of the Biologics  License  Application  and closed our
               Cellcor facility in September 1998.

          - Sold our interest in Targon Corporation.
               Our review  determined  that the projects  under  development  by
               Targon  Corporation  ("Targon")  were  not  consistent  with  our
               corporate strategies. During August 1998, we sold our interest in
               Targon  to our  partner  in the  venture,  Elan  Corporation  plc

                                       4
<PAGE>
               ("Elan")  for $2 million in cash.  In  addition,  we  received $2
               million from Elan in exchange for a convertible  promissory note.


          - Sold our manufacturing facility.
               We determined  that  outsourcing  manufacturing  of the Company's
               products  would  be  more  economical  and  consistent  with  our
               strategies. During early January, 1999, we sold our manufacturing
               facility to Bard Bio Pharma  L.P., a  subsidiary  of Norwalk,  CT
               based pharmaceutical  company Purdue Pharma L.P. We received $3.9
               million in cash for the assets in the facility,  and the lease to
               the  building.  We also signed an agreement  with Purdue to share
               space in the building to continue to manufacture  our ProstaScint
               and OncoScint  products at the same location.  Employees involved
               in manufacturing  currently remain CYTOGEN employees,  but Purdue
               will pay for their labor costs  except  while they are working on
               our products.

          - Reduced expenses.
               We have  downsized the workforce by eliminating  positions  which
               were no longer critical to our strategic plans and have curtailed
               expenses for basic research.


Recent Developments

     On June 15,  1999,  we  reacquired  the rights  for  immune  therapy to our
prostate specific membrane antigen ("PSMA")  technology by acquiring  Prostagen,
Inc.,  which had sublicensed  PSMA from us for prostate cancer immune therapy in
1996. We also acquired other assets held by Prostagen,  including  approximately
$550,000 in cash, a minority ownership in Northwest Biotherapeutics, Inc., which
is  developing  PSMA for cell  therapy,  and a contract  with  Velos,  Inc.  for
marketing a cancer patient software  management program for hospitals and health
care payors.  In  exchange,  we issued 2.5 million  shares of our common  stock,
valued at $1.00 per share, and will issue up to an additional $4.5 million worth
of our common stock (valued at the time of issuance) if milestones  are achieved
in the PSMA development program.

     On  June  15,  1999,  we  also  entered  a  joint  venture  with  Progenics
Pharmaceuticals,  Inc. to develop PSMA for immune  therapy,  emphasizing  cancer
vaccines  for prostate and  possibly  other  cancers.  The project will be owned
equally by us and Progenics.  Progenics will fund development through the filing
of an  Investigational  New  Drug  Application  with  the  U.S.  Food  and  Drug
Administration.  We believe this first step will last  approximately  two years.
After and if that step is achieved successfully, we and Progenics will share the
costs of clinical trials. We will have exclusive North American marketing rights
on products developed by the venture. We will receive $2 million in payments for
licensing  this  technology  to the venture.  $500,000 has been received and the
balance will be paid in installments  through December 31, 2001. We can not give
any assurance  that this program will result in products  reaching the market or
being successful.

     In June of 1999,  we  reacquired  rights to our  ProstaScint  and OncoScint
products in Canada,  which had been licensed to Faulding (Canada),  Inc. We also
agreed with Berlex Laboratories,  Inc., the North American marketing partner for
our Quadramet product,  that we would market Quadramet in Canada. We did not pay
for either of these  agreements.  OncoScint  and  Quadramet  are approved by the
Canadian Health Care Branch;  ProstaScint is under expedited  review. We believe
these  products may be marketed to major  cancer  centers in Canada and will not
require the same level of resources as for U. S. marketing.  However, we can not
be certain that ProstaScint will be approved in Canada, that these products will
be  reimbursable  under the Canadian  health care  system,  or that they will be
accepted by physicians.



                                       5
<PAGE>

                                  RISK FACTORS


     Prospective  investors in the common stock offered hereby should  carefully
consider  the  following  risk  factors,  in addition  to the other  information
contained  in  this  prospectus.   This  prospectus   contains   forward-looking
statements  which  involve  risks and  uncertainties.  Our actual  results could
differ materially from those anticipated in these forward-looking  statements as
a result of certain  factors,  including  those set forth in the following  risk
factors and elsewhere in this prospectus.

History of Operating Losses and Accumulated Deficit

         We have a history of operating losses as follows:

                                             Operating      Net Profit (Loss) to
                                               Losses       Common Stockholders
         Three months
         ended March 31, 1999              ($ 1,694,000)          $ 1,657,000

         Year Ended December 31, 1998     ($ 15,915,000)        ($ 13,271,000)

         Year Ended December 31, 1997     ($ 31,027,000)        ($ 32,064,000)


     The  operating  losses were due in part to limited  revenues and to various
expenditures, including:

          -  Research and development activities;
          -  Acquiring of complementary products and technologies;
          -  Seeking regulatory approvals for our products;
          -  Preclinical and clinical studies related to our products;
          -  Preparing of submissions to the United States Food and Drug
             Administration;
          -  Developing of sales,  marketing,  manufacturing  and  distribution
             channels;
          -  Developing of internal manufacturing capabilities relating to
             ProstaScint; and
          -  General and administrative expenses.

     We expect to incur operating losses in the future due primarily to:

          -  Continuing product development;
          -  Acquiring, developing and commercializing complementary products
             and technologies; and
          -  Expansion of our sales and marketing activities.

     As of March 31, 1999, we had an accumulated  deficit of approximately  $300
million.

                                       6
<PAGE>

Uncertainty of Profitability

     Our ability to achieve and maintain  profitability is highly dependent upon
the  successful  commercialization  of our  products,  including  Quadramet  and
ProstaScint.  Our  profitability  may also depend on success  with PSMA and with
AxCell  Biosciences.  There  can be no  assurance  that we will  ever be able to
successfully   commercialize   our   products  or  that  we  will  ever  achieve
profitability.

Fluctuating Results of Operations

     Our results of operations  have fluctuated on an annual and quarterly basis
and may  fluctuate  significantly  from period to period in the future,  due to,
among other factors:

          -  Variations in revenue from sales of and royalties from our
             products;
          -  Timing of regulatory approvals and other regulatory announcements
             relating to our products;
          -  Variations in our  marketing,  manufacturing  and  distribution
             channels;
          -  Timing  of  the   acquisition   and  successful   integration  of
             complementary  products and technologies;
          -  Timing of new product announcements and introductions by the
             Company and its competitors, and
          -  Product obsolescence resulting from new product introductions.

     Many of these  factors,  and others  not  listed  above,  are  outside  our
control. Due to one or more of these factors, our results of operations may fall
below the  expectations  of  securities  analysts  and  investors in one or more
future quarters.  If this happens, the market price of our common stock could be
materially and adversely affected.


Need for Additional Capital

     We have incurred  negative cash flows from operations since inception,  and
have  expended,  and will need to  expend,  substantial  funds to  complete  our
planned product development efforts, including:

          -  Acquisition of products and complementary technologies;
          -  Research and development;
          -  Clinical studies and regulatory activities; and
          -  Expansion of our marketing, sales and distribution activities.

In addition to the above requirements, we expect that we will require additional
capital either in the form of debt or equity,  irrespective  of whether and when
we reach profitability, for the following activities:

          -  Working capital;
          -  Acquisitions of additional products and technologies; and
          -  Further product development.

                                       7

<PAGE>
     Our future  capital  requirements  and the adequacy of our available  funds
depend on numerous factors, including:

          -  Successful commercialization of our products;
          -  Acquisition of complementary products and technologies;
          -  Magnitude, scope and results of our product development efforts;
          -  Progress of preclinical studies and clinical trials;
          -  Progress of regulatory affairs activities;
          -  Costs of filing, prosecuting, defending and enforcing patent claims
             and other intellectual property rights;
          -  Competing technological and market developments; and
          -  Expansion of strategic alliances for the sale, marketing and
             distribution of our products.

     We  currently  expect  that our  existing  cash,  together  with  decreased
operating costs, and revenues generated by product sales and royalties,  and the
proceeds from this offering,  will be adequate to fund our operations into 2000.
We can not  give  assurance  that we will  not  consume  our  available  capital
resources before that time. If we experience unanticipated cash requirements, we
may require additional capital to:

          -  Fund operations;
          -  Continue research and development programs;
          -  Continue pre-clinical and clinical testing of potential products;
             or
          -  Commercialize any products that may be developed.

Possible Unavailability of Other Financing

     There can be no assurance we will be able to obtain additional financing on
acceptable  terms,  if at all. We may seek to raise  additional  capital through
public  or  private  offerings  of  equity  or  debt  or  through  collaborative
agreements,  strategic  alliances with corporate partners and others, or through
other  contractual  arrangements with third parties.  We may receive  additional
funds upon the exercise of common stock purchase warrants and stock options, but
there can be no assurance  that any warrants or stock  options will be exercised
or that the amounts  received will be sufficient to meet our capital  needs.  If
adequate  funds are not  available,  we may be required to delay,  further scale
back or eliminate one or more of our development  programs or certain aspects of
our  operations,   or  to  obtain  funds  by  entering  into  arrangements  with
collaborative  partners or others that may  require us to  relinquish  rights to
certain of our products, product candidates,  technologies or potential markets,
that we would otherwise not relinquish. If adequate funds are not available, our
business,  financial  condition and results of operations will be materially and
adversely affected.

Possible Dilution or Requirement to Comply with Covenants

     Additional   equity  financing  may  result  in  substantial   dilution  to
shareholders,  and debt financing may limit our ability to declare dividends, or
may  require us to comply  with  covenants  that would  alter the way we conduct
business.


                                       8
<PAGE>

Dependence on Market Acceptance of ProstaScint and Quadramet for Revenues

     None of our products has a significant history of revenues. ProstaScint and
Quadramet  were  introduced  to the market during the first half of 1997 and are
expected to account for a significant percentage of our product-related revenues
in the foreseeable  future. For the year ended December 31, 1998,  revenues from
ProstaScint  and  Quadramet  accounted  for  over  91%  of our  product  related
revenues.

     Because  these  products  contribute  the  majority  of our  revenues,  our
business,  financial  condition  and  results  of  operations  depend  on  their
acceptance as safe, effective and cost efficient alternatives to other available
treatment and diagnostic protocols by the medical community, including:

          -  health care providers, such as hospitals and physicians
          -  third-party payors, including Medicare, Medicaid, private insurance
             carriers and health maintenance organizations


Market Acceptance of ProstaScint

     ProstaScint is marketed in the United States by the urological  division of
C. R. Bard,  Inc.  ("BARD"),  with CYTOGEN  retaining  co-marketing  rights.  We
believe that efforts to market ProstaScint to physicians and hospitals have been
well  received,  based on  increasing  sales,  statements  by  physicians to our
employees as to the benefits of ProstaScint and  presentations on ProstaScint by
physicians at medical  association  meetings.  However,  training by physicians,
technicians  and other health care  professionals  is required before certain of
our products can be used for diagnosis or therapy.  In order to use ProstaScint,
our  customers,   including  technologists  and  physicians,  must  successfully
complete our Partners in Excellence Program ("PIE(TM)  Program"),  a proprietary
training program designed to promote the correct  acquisition and interpretation
of ProstaScint  images.  This approach is,  therefore,  technique  dependent and
requires a learning  commitment on the part of users.  There can be no assurance
that additional  physicians  will make this commitment or otherwise  accept this
product as part of their treatment practices.

     CYTOGEN has a program  dedicated to providing  information to and resolving
issues with managed care organization  ("MCOs") relating to reimbursement.  BARD
is  obligated  to market  ProstaScint  to MCOs,  but has not yet  implemented  a
significant  program in this area.  Failure to market  ProstaScint to MCOs could
hinder acceptance or reimbursement,  although we cannot quantify what impact, if
any, this marketing effort could have on sales of ProstaScint.

Market Acceptance of Quadramet

     Berlex  Laboratories,  Inc.  ("Berlex") is responsible for the marketing of
Quadramet in the United  States,  including  marketing to MCOs,  by an agreement
entered in October 1998.  Their marketing  efforts began in the first quarter of
1999.  We can not give any  assurance  that Berlex will be able to  successfully
market  Quadramet,  or that this  agreement  will be profitable for the Company.
CYTOGEN recently obtained  marketing rights to Quadramet in Canada,  but has not
yet  implemented  a  selling  program.  We can not give any  assurance  that the
product  can be  marketed  effectively  in  Canada,  or that it will  contribute
significantly to the Company's revenues.

     We have  licensed  the rights to Quadramet  from The Dow  Chemical  Company
("Dow").  Such  rights are  currently  limited to North and Latin  America  with
respect to currently approved  indications.  We also hold a license from Dow for
use of Quadramet in treatment of  refractory  rheumatoid  arthritis in North and
Latin America and in other countries,  including  European  countries and Japan.

                                       9

<PAGE>
There can be no assurance  that  Quadramet will be accepted in the United States
and Canada,  where the product is currently  approved.  We also can not give any
assurance  that  Quadramet  will be accepted  in any markets  outside the United
States and Canada, or approved for additional indications in any locations,  due
to the influence of established  medical practices and other social and economic
factors beyond our control.

     Accordingly,  there can be no assurance that  ProstaScint or Quadramet will
achieve  market  acceptance  on a  timely  basis,  or at  all.  The  failure  of
ProstaScint  or Quadramet  to achieve  market  acceptance  would have a material
adverse  effect on the Company's  business,  financial  condition and results of
operations.

Risks Relating to Potential Additional Cuts in Company Programs

     We are reviewing and prioritizing  programs,  and there can be no assurance
that  we will  not  cut  programs  to  conserve  capital.  After  reviewing  and
prioritizing our business  opportunities,  we have ceased various  developmental
and research programs,  including  submission of a Biologics License Application
for ALT. In  addition,  we have ceased basic  research in our Genetic  Diversity
Library  ("GDL")  program.  Any additional cuts would increase our dependence on
our remaining  programs,  and would  increase the risk from such programs to the
Company as a whole,  which could  materially and adversely affect our chances of
obtaining  profitability.  While  we plan to  allocate  our  resources  to those
programs  with the greatest  potential to  contribute  to a sound  financial and
operating  position,  there can be no assurance  that we will be  successful  in
doing so.

Dependence on our Collaborative Partners

     Our  success   depends  in  significant   part  upon  the  success  of  our
collaborative  partners.  We have entered into the following  agreements for the
sales,  marketing,   distribution  and  manufacture  of  our  products,  product
candidates and technologies:

          -  Sub-license  and marketing  agreement with Berlex relating
             to the  Quadramet  technology  that we have  licensed from
             Dow.  Berlex is  responsible  for  marketing,  selling and
             arranging  manufacturing  and distribution of Quadramet in
             the  United  States,   Canada,  and  Latin  America.  This
             agreement  expires on the later of  December  20,  2014 or
             upon the expiration of the patents covering Quadramet.
          -  Co-promotion   agreement   with  BARD,   granting   BARD's
             Urological   Division  the   exclusive   right  to  market
             ProstaScint to urologists; and
          -  Agreement  for  manufacture  of  Quadramet  by The  DuPont
             Pharmaceuticals Company (formerly the radiopharmaceuticals
             division of the DuPont Merck Company, "DuPont").
          -  A joint venture with Progenics Pharmaceuticals, Inc. for
             the development of PSMA for immunotherapy for prostate and
             other cancers.

Because our  collaborative  partners are  responsible  for certain of our sales,
marketing,  manufacturing  and  distribution  activities,  these  activities are
outside our direct  control.  There can be no assurance  that our partners  will
perform their  obligations  under these  arrangements  with the Company.  In the
event that our  collaborative  partners do not successfully  market and sell our
products, or breach their obligations under the above agreements, the successful
commercialization of Quadramet and ProstaScint would not be achieved or would be
delayed,  and new product  development  could be  inhibited,  which could have a
material  adverse  effect on our  business,  financial  condition and results of
operations.

                                       10
<PAGE>

     There can be no  assurance  that we will be able to maintain  our  existing
collaborative  arrangements;  if they expire or are terminated,  there can be no
assurance that they will be renewed,  or that new arrangements will be available
on acceptable terms, if at all. In addition,  there can be no assurance that any
new arrangements or renewals of existing  arrangements will be successful,  that
the parties to any new or renewed  agreements  will  perform  their  obligations
thereunder, or that any potential collaborators will not compete with us.

     There can also be no assurance  that our existing or future  collaborations
will  lead  to the  development  of  product  candidates  or  technologies  with
commercial  potential,  that we will be able to  obtain  proprietary  rights  or
licenses  for  proprietary  rights for our product  candidates  or  technologies
developed  in  connection  with these  arrangements,  or that we will be able to
ensure the  confidentiality of proprietary  rights and information  developed in
such arrangements or prevent the public disclosure thereof.

Limited Sales, Marketing and Distribution Capabilities

     We have limited internal sales, marketing and distribution capabilities. We
depend on Berlex for the sales,  marketing and  distribution of Quadramet in the
United  States,  and on BARD for the  sale  and  marketing  of  ProstaScint.  In
locations outside the United States, we have not established a selling presence.
If we are unable to establish  and maintain  significant  sales,  marketing  and
distribution  efforts,  either  internally  or through  arrangements  with third
parties,  our business,  financial  condition and results of operations could be
materially adversely effected.

We have limited marketing history for our products:

          -  ProstaScint  was  approved  for  marketing  by the  FDA in
             October 1996, and commercially  launched in February 1997.
             ProstaScint  sales have  experienced  growth since product
             launch.  However,  there  can be no  assurance  that  such
             growth will continue; and

          -  Quadramet was approved for marketing by the FDA in March 1997 and
             launched  by DuPont in June  1997.  Quadramet  sales  during  the
             period  from  initial  launch  were  below the  levels of minimum
             royalty  payments we recorded  under our  agreement  with DuPont.
             Growth  during early months was limited by the need for hospitals
             to  obtain  license  amendments  under  federal  and state law to
             receive and handle this new  radioactive  product.  In  addition,
             initial  marketing  efforts by DuPont were directed  primarily to
             nuclear medicine  physicians who directly  administer the product
             to  patients.  While we believe this  approach  was  necessary to
             generate product  understanding,  marketing to primary caregivers
             for likely  candidates  for treatment with Quadramet is necessary
             for extensive  penetration  into the market.  Berlex  maintains a
             sales force which calls on the physician  oncological  community;
             however,  there is no significant  experience  with sales efforts
             for  Quadramet  and there can be no assurance  that sales efforts
             will be successful.

     The failure of our marketing  efforts to achieve  commercial  success would
have a material adverse effect on our business and results of operations.

Risks Associated with Manufacturing;  Third-Party  Manufacturers'  Dependence on
Single Source Suppliers; Need to Comply with Manufacturing Regulations

     Our products must be manufactured  either internally or through third-party
manufacturers  in  compliance  with  regulatory  requirements  and at acceptable
costs.

                                       11

<PAGE>
     While we believe that our  manufacturing  operations  currently address our
needs for the production of our products, there can be no assurance that we will
be able to continue to  manufacture,  arrange for  manufacture on a commercially
reasonable  basis, or successfully  outsource the manufacturing of our products.
If we are unable to  successfully  manufacture or arrange for the manufacture of
our products and product candidates, there would be a material adverse effect on
our business, financial condition and results of operations.

     Quadramet is  manufactured  by DuPont  pursuant to an  agreement  with both
Berlex and CYTOGEN. Certain components of Quadramet,  particularly  Samarium-153
and EDTMP,  are  provided  to DuPont by outside  suppliers.  Due to  radioactive
decay,  Samarium-153 must be produced on a weekly basis. On one occasion, DuPont
was unable to  manufacture  Quadramet  on a timely basis due to the failure of a
supplier to provide Samarium-153.  If DuPont cannot obtain sufficient quantities
of such components on commercially  reasonable  terms, or in a timely manner, it
would be unable to manufacture  Quadramet on a timely and  cost-effective  basis
which could have a material adverse effect on our business,  financial condition
and results of operations.  Alternative  sources for these components may not be
readily  available.  If  DuPont  were to lose its  sources  of  supply  for such
components,  production of Quadramet  would be  interrupted,  which could have a
material  adverse  effect on our  business,  financial  condition and results of
operations.

     The Company and its third party manufacturers are required to adhere to FDA
regulations setting forth requirements for current Good Manufacturing  Practices
("cGMP") and similar  regulations in other  countries,  which include  extensive
testing, control and documentation  requirements.  Ongoing compliance with cGMP,
labeling and other  applicable  regulatory  requirements  is  monitored  through
periodic  inspections  and market  surveillance  by state and federal  agencies,
including the FDA, and by comparable agencies in other countries. Failure of the
Company and its third-party  manufacturers to comply with applicable regulations
could result in sanctions  being imposed on us,  including  fines,  injunctions,
civil  penalties,  failure of the  government  to grant  premarket  clearance or
premarket  approval of drugs,  delays,  suspension  or  withdrawal of approvals,
seizures  or  recalls  of   products,   operating   restrictions   and  criminal
prosecutions.

Risks Associated with Reimbursement by Third-Party Payors

     Our business,  financial  condition and results of operations will continue
to be affected by the efforts of  governments  and other  third-party  payors to
contain or reduce the costs of  healthcare  through  various  means.  There have
been,  and we expect  that there will  continue  to be, a number of federal  and
state proposals to implement  government control of pricing and profitability of
therapeutic and diagnostic imaging agents such as our products.  In addition, an
emphasis on managed  increases  possible  pressure on pricing of these products.
While we cannot predict whether such legislative or regulatory proposals will be
adopted or the effects  such  proposals  or managed care efforts may have on our
business,  the announcement of such proposals and the adoption of such proposals
or efforts  could  have a material  adverse  effect on our  business,  financial
condition and results of  operations.  Further,  to the extent such proposals or
efforts have a material  adverse effect on other  companies that are prospective
corporate partners for the Company, our ability to establish strategic alliances
may be materially and adversely affected.

     Sales of our products depend in part on the  availability of  reimbursement
to the consumer from  third-party  payors,  including  Medicare,  Medicaid,  and
private health insurance plans.  Third-party payors are increasingly challenging
the prices charged for medical products and services.  There can be no assurance
that our products will be considered  cost-effective  and that  reimbursement to
consumers  will continue to be  available,  or will be sufficient to allow us to
sell  our  products  on a  competitive  basis.  Approval  of  our  products  for

                                       12
<PAGE>
reimbursement  by a third  party  payor  may  depend  on a  number  of  factors,
including the payor's  determination that our products are clinically useful and
cost-effective,  medically  necessary and not  experimental or  investigational.
Reimbursement  is determined by each payor  individually  and in specific cases.
The reimbursement  process can be time consuming and costly. If we cannot secure
adequate third party  reimbursement for our products,  there would be a material
adverse effect on our business, financial condition and results of operations.

Intense Competition in the Biotechnology and Pharmaceutical Industries

     The  biotechnology  and  pharmaceutical  industries  are subject to intense
competition from large  pharmaceutical,  biotechnology  and other companies,  as
well as universities and research institutions.

     Many of these competitors have, compared to us, substantial advantages with
respect to their:

          -  Financial, marketing, sales, manufacturing, distribution and
             technological resources;
          -  Sales and marketing expertise;
          -  Distribution channels;
          -  Experience in establishing third-party reimbursement for their
             products;
          -  Research and development expertise;
          -  Experience in conducting clinical trials;
          -  Experience in regulatory matters;
          -  Manufacturing efficiency; and
          -  Name recognition.

     Due to this intensely  competitive  environment,  there can be no assurance
that we will be able to compete  effectively  against such existing or potential
competitors or that  competition  will not have a material adverse effect on our
business, financial condition and results of operations.

     Quadramet  competes  with other more  traditional  treatments or therapies,
such as:

          -  External beam radiation;
          -  Chemotherapy agents;
          -  Narcotic analgesics; and
          -  Radiopharmaceuticals.

     In addition,  certain of our  competitors  may be in the process of seeking
FDA or  foreign  regulatory  approval  for their  own  products,  which  compete
directly or indirectly with ours.

     We are highly  dependent  upon  proprietary  technology and seek to protect
such technology through a combination of patents, licenses and trade secrets. We
have applied for, obtained and licensed patents for certain  proprietary aspects
of our  technology  and  processes  in the  U.S.  and  other  countries.  We are
particularly  dependent  upon the  enforceability  of our license  with Dow with
respect to  Quadramet.  There can be no  assurance  that our owned and  licensed
patents will prove to be enforceable or that additional  patents will be issued.
Neither can assurance be given that the technologies we use do not infringe upon
the  proprietary  rights  of  others,  although  we are not  aware  of any  such
infringement  or any adverse claim.  Insofar as we rely in part on trade secrets
and unpatented  know-how to maintain our competitive  position,  there can be no
assurance  that  others  will not  independently  develop  similar  or  superior
technologies  or that our trade  secrets and  know-how  will not become known to
others. We could incur  substantial costs in seeking  enforcement of our patents

                                       13
<PAGE>
against  infringement  or  preventing  unauthorized  use of our trade secrets by
others, or in defending patent infringement claims brought against the Company.

     Our  success  depends,  in part,  on our  ability,  and the  ability of our
collaborators or licensors,  to obtain  protection for products and technologies
under United States and foreign patent laws, to preserve  trade secrets,  and to
operate without infringing the proprietary  rights of third parties.  Because of
the substantial  length of time and expense  associated with  development of new
products,  the  biopharmaceutical  industry  places  considerable  importance on
obtaining,  and  maintaining,   patent  and  trade  secret  protection  for  new
technologies, products and processes. We have obtained rights to certain patents
and patent  applications  and may obtain or seek  rights  from third  parties to
additional  patents  and patent  applications.  There can be no  assurance  that
patent  applications  relating to our  products or  technologies  will result in
patents  being  issued,   that  any  issued  patents  will  afford  us  adequate
protection, or that such patents will not be challenged,  invalidated, infringed
or  circumvented.  Furthermore,  there can be no assurance  that others have not
developed,  or will not  develop,  similar  products or  technologies  that will
compete with ours without infringing upon our intellectual property rights.

     Legal standards relating to the scope of claims and the validity of patents
in the  biopharmaceutical  industry are  uncertain  and still  evolving,  and no
assurance can be given as to the degree of protection  that will be afforded any
patents we are issued or license from others. There can be no assurance that, if
challenged  by others in  litigation,  the patents we have been assigned or have
licensed from others will not be found  invalid.  There can be no assurance that
our  activities  would  not  infringe  patents  owned  by  others.  Defense  and
prosecution  of  patent  matters  can  be  expensive  and  time-consuming   and,
regardless  of  whether  the  outcome  is  favorable  to us,  can  result in the
diversion of substantial financial,  management and other resources.  An adverse
outcome could:

          -  Subject us to significant liability to third parties;
          -  Require us to cease any related research and development activities
             and product sales; or
          -  Require us to obtain licenses from third parties.

     No assurance can be given that any licenses required under any such patents
or proprietary  rights would be made available on terms  acceptable to us, if at
all.  Moreover,  the laws of certain  countries may not protect our  proprietary
rights to the same extent as United States law.

     Our success also depends on the skill,  knowledge,  and  experience  of our
scientific and technical  personnel.  To help protect our rights, we require all
employees, consultants, advisors and collaborators to enter into confidentiality
agreements  that require  disclosure,  and in most cases,  assignment  to us, of
their ideas,  developments,  discoveries and  inventions,  and that prohibit the
disclosure of confidential  information to anyone outside the Company. There can
be no assurance, however, that these agreements will provide adequate protection
for our trade secrets, know-how or other proprietary information in the event of
any unauthorized use or disclosure.

Product Development

     Product  development  involves  a high  degree  of  risk.  There  can be no
assurance that the product candidates we develop,  pursue or offer will prove to
be safe and effective,  will receive the necessary  regulatory approvals or will
ultimately  achieve market  acceptance.  These product  candidates  will require
substantial additional investment,  laboratory development, clinical testing and
regulatory approvals prior to their commercialization. There can be no assurance
that we will  not  experience  difficulties  that  could  delay or  prevent  the
successful  development,  introduction and marketing of new products.  If we are


                                       14

<PAGE>
unable to successfully  develop and commercialize  products on a timely basis or
at all, or achieve market acceptance of such products, there could be a material
adverse effect on our business, financial condition and results of operations.

     Before we obtain regulatory approvals for the commercial sale of any of our
products under development,  we must demonstrate through preclinical studies and
clinical  trials that the product is safe and efficacious for use in each target
indication.  The results from preclinical  studies and early clinical trials may
not be predictive of results that will be obtained in large-scale  testing,  and
there can be no assurance  that the our  clinical  trials will  demonstrate  the
safety and efficacy of any  products or will result in  marketable  products.  A
number of companies in the  biotechnology  industry  have  suffered  significant
setbacks in advanced  clinical trials,  even after promising  results in earlier
trials.  In  addition,  there can be no assurance  that product  issues will not
arise following successful clinical trials and FDA approval.

     The rate of  completion  of  clinical  trials  also  depends on the rate of
patient  enrollment.  Patient enrollment depends on many factors,  including the
size of the patient  population,  the nature of the  protocol,  the proximity of
patients to clinical sites and the eligibility criteria for the study. Delays in
planned patient enrollment may result in increased costs and delays, which could
have a material adverse effect on our business,  financial condition and results
of operations.

Government Regulation

     Any products  tested,  manufactured  or  distributed by us or on our behalf
pursuant to FDA  clearances or approvals are subject to pervasive and continuing
regulation  by numerous  regulatory  authorities,  including  primarily the FDA.
Changes in existing  requirements  or adoption of new  requirements  or policies
could adversely affect our ability to comply with regulatory requirements. If we
fail to comply with regulatory  requirements,  there could be a material adverse
effect on our business, financial condition and results of operations. There can
be no  assurance  that we will not be  required  to incur  significant  costs to
comply with laws and regulations in the future or that laws or regulations  will
not have a material  adverse effect upon our business,  financial  condition and
results of operations.

     Numerous  federal,  state  and  local  governmental   authorities  (each  a
"Regulatory  Agency"),  principally  the  FDA,  and  similar  agencies  in other
countries,  regulate the preclinical testing,  clinical trials,  manufacture and
promotion of any  compounds  we or our  collaborative  partners  develop and the
manufacturing  and marketing of any resulting  drugs.  The drug  development and
regulatory  approval  process is lengthy,  expensive,  uncertain  and subject to
delays.

          -   Any compound we or our collaborative partners develop must
              receive  Regulatory  Agency  approval  before  it  may  be
              marketed as a drug in a particular country.
          -   The regulatory process, which includes preclinical testing
              and clinical trials of each compound in order to establish
              its safety and  efficacy,  varies from country to country,
              can take  many  years  and  requires  the  expenditure  of
              substantial resources.
          -   In all  circumstances,  approval of the use of  previously
              unapproved   radioisotopes  in  certain  of  our  products
              requires   approval  of  either  the  Nuclear   Regulatory
              Commission  or equivalent  state  regulatory  agencies.  A
              radioisotope  is an  unstable  form  of an  element  which
              undergoes  radioactive  decay,  thereby emitting radiation
              which  may be used,  for  example,  to  image  or  destroy
              harmful growths or tissue.  There can be no assurance that
              such approvals  will be obtained on a timely basis,  or at
              all.
          -   Data obtained from preclinical and clinical activities are
              susceptible to varying  interpretations which could delay,
              limit or prevent Regulatory Agency approval.

                                       15

<PAGE>
          -   Delays or rejections may be encountered based upon changes
              in  Regulatory  Agency  policy  during  the period of drug
              development and/or the period of review of any application
              for  Regulatory  Agency  approval  for a  compound.  These
              delays  could  adversely   affect  the  marketing  of  any
              products we or our collaborative partners develop,  impose
              costly  procedures  upon  our  activities,   diminish  any
              competitive  advantages we or  collaborative  partners may
              attain  and  adversely   affect  our  ability  to  receive
              royalties.

     There can be no  assurance  that,  even after  such time and  expenditures,
Regulatory  Agency approvals will be obtained for any compounds  developed by or
in collaboration with the Company. Moreover, if Regulatory Agency approval for a
drug is granted,  such approval may entail limitations on the indicated uses for
which it may be  marketed  that could  limit the  potential  market for any such
drug.  Furthermore,  if and when  such  approval  is  obtained,  the  marketing,
manufacture,  labeling, storage and record keeping related to our products would
remain  subject to extensive  regulatory  requirements.  Discovery of previously
unknown problems with a drug, its manufacture, or its manufacturer may result in
restrictions on such drug, manufacture or manufacturer,  including withdrawal of
the drug from the market.  Failure to comply with regulatory  requirements could
result in fines, suspension of regulatory approvals,  operating restrictions and
criminal prosecution.

     The U. S. Food,  Drug and  Cosmetics  Act  requires  that our  products  be
manufactured   in  FDA  registered   facilities   subject  to  inspection.   The
manufacturer  must be in compliance with current good  manufacturing  practices,
or, cGMP, which imposes certain  procedural and documentation  requirements upon
us, and our  manufacturing  partners with respect to  manufacturing  and quality
assurance activities. Noncompliance with cGMP can result in, among other things,
fines, injunctions,  civil penalties,  recalls or seizures of products, total or
partial  suspension of production,  failure of the government to grant premarket
clearance or premarket approval for drugs, withdrawal of marketing approvals and
criminal prosecution. If we or our manufacturing partners were to fail to comply
with the  requirements of cGMP,  there could be a material adverse effect on the
Company's business, financial condition and results of operations.

Attraction and Retention of Key Personnel

     We are highly  dependent on the  principal  members of our  management  and
scientific  staff,  the  loss of whose  services  might  significantly  delay or
prevent the achievement of research,  development or strategic  objectives.  Our
success depends on our ability to retain key employees and to attract additional
qualified employees. Competition for such personnel is intense, and there can be
no assurance that we will be able to retain  existing  personnel and to attract,
assimilate or retain additional highly qualified employees in the future.

     We have an employment  agreement  with our  President  and Chief  Executive
Officer,  H. Joseph  Reiser,  Ph.D.,  which  provides for bonuses and vesting of
options for the purchase of shares of common stock based on continued employment
and on the  achievement  of  performance  objectives  defined  by the  Board  of
Directors. We do not have employment agreements with our other key personnel. If
we are unable to hire and retain  personnel in key  positions,  there could be a
material  adverse  effect on the  Company's  business,  financial  condition and
results of operations.

Potential Inadequacy of Product Liability Insurance

     Our business is subject to product liability risks inherent in the testing,
manufacturing  and  marketing of our  products.  There can be no assurance  that
product  liability claims will not be asserted against us, our  collaborators or
licensees. While we currently maintain product liability insurance in amounts we


                                       16

<PAGE>
believe are  adequate,  there can be no  assurance  that such  coverage  will be
adequate to protect us against future product  liability  claims or that product
liability  insurance  will be  available  to us in the  future  on  commercially
reasonable terms, if at all. Furthermore, there can be no assurance that we will
be able to avoid  significant  product  liability claims and adverse  publicity.
Consequently, a product liability claim or other claim with respect to uninsured
or  underinsured  liabilities  could  have  a  material  adverse  effect  on our
business, financial condition and results of operations.

Environmental Regulation

     We are  subject  to a  variety  of  local,  state  and  federal  government
regulations relating to:

          -  Storage;
          -  Discharge;
          -  Handling;
          -  Emission;
          -  Generation;
          -  Manufacture; and
          -  Disposal

of toxic,  infectious or other  hazardous  substances  used to  manufacture  our
products.  If we fail to comply with these  regulations,  we could be subject to
significant  liabilities,  which  could  have a material  adverse  effect on our
business, financial condition and results of operations.

Volatility of Stock Price

     The market  prices  for  securities  of  biotechnology  and  pharmaceutical
companies have historically  been highly volatile,  and the market has from time
to time experienced significant price and volume fluctuations that are unrelated
to the operating  performance of particular  companies.  The market price of our
common stock has fluctuated  over a wide range and may continue to fluctuate for
various reasons,  including,  but not limited to,  announcements  concerning the
Company or our competitors regarding:

          -  Results of clinical trials;
          -  Technological innovations or new commercial products;
          -  Changes in governmental regulation or the status of our regulatory
             approvals or applications;
          -  Changes in earnings;
          -  Changes in health care policies and practices;
          -  Developments or disputes concerning proprietary rights;
          -  Litigation or public concern as to safety of the our potential
             products; and
          -  Changes in general market conditions.


                                       17
<PAGE>

Impact of Anti-takeover Provisions on the Market Price of Common Stock

     We have  adopted  various  anti-takeover  provisions  which may  affect the
market price of the common stock.

     Our Board of Directors has the  authority,  without  further  action by the
holders of common stock, to issue from time to time, up to 5,200,000  additional
shares of  preferred  stock in one or more  classes  or  series,  and to fix the
rights and preferences of such preferred stock. Pursuant to these provisions, we
have implemented a Stockholder Rights Plan by which one preferred stock purchase
right is attached to each share of common  stock,  as a means to deter  coercive
takeover  tactics and to prevent an acquirer from gaining control of the Company
without some mechanism to secure a fair price for all of our  stockholders if an
acquisition was completed. These rights will be exercisable if a person or group
acquires beneficial ownership of 20% or more of our common stock and can be made
exercisable by action of our Board of Directors if a person or group commences a
tender offer which would result in such person or group beneficially  owning 20%
or more of our  common  stock.  Each right  will  entitle  the holder to buy one
one-thousandth  of a share of a new  series  of junior  participating  preferred
stock for $20.  If any person or group  becomes the  beneficial  owner of 20% or
more of CYTOGEN 's common stock (with  certain  limited  exceptions),  then each
right not owned by the 20% stockholder  will entitle its holder to purchase,  at
the right's then current exercise price,  common shares having a market value of
twice the  exercise  price.  In  addition,  if after any person has become a 20%
stockholder,  we  are  involved  in  a  merger  or  other  business  combination
transaction with another person,  each right will entitle its holder (other than
the 20%  stockholder) to purchase,  at the right's then current  exercise price,
common shares of the acquiring  company having a value of twice the right's then
current exercise price.

     We are subject to  provisions of Delaware  corporate law which,  subject to
certain exceptions, will prohibit us from engaging in any "business combination"
with a person who, together with affiliates and associates,  owns 15% or more of
our  common  stock (an  "Interested  Stockholder")  for a period of three  years
following the date that such person became an Interested Stockholder, unless the
business combination is approved in a prescribed manner.

     These  provisions  of the  Stockholder  Rights  Plan,  our  Certificate  of
Incorporation, and of Delaware law may have the effect of delaying, deterring or
preventing  a change in  control of the  Company,  may  discourage  bids for the
common stock at a premium over market price and may adversely  affect the market
price, and the voting and other rights of the holders, of the common stock.


Impact of Shares Eligible for Future Sale on the Market Price of the Common
Stock

     A large number of shares of common stock already  outstanding,  or issuable
upon  exercise of options  and  warrants,  are  eligible  for resale,  which may
adversely affect the market price of the common stock. As of March 31, 1999, the
Company  had  65,112,000  shares  of common  stock  outstanding.  An  additional
7,446,099  shares of common stock are issuable upon the exercise of  outstanding
options  and  warrants  (including  300,000  shares  issuable  upon  exercise of
warrants granted to Kingsbridge and the May Davis Group,  Inc.,  placement agent
for the Equity  Line  Agreement.  Substantially  all of such  shares  subject to
outstanding  options and warrants will,  when issued upon exercise  thereof,  be
available  for  immediate  resale in the public  market  pursuant  to  currently
effective registration  statements under the Securities Act of 1933, as amended,
or pursuant to Rule 701 promulgated thereunder.


                                       18
<PAGE>


                         PRICE RANGE OF OUR COMMON STOCK

         Our common stock is  currently  quoted on the Nasdaq Stock Market under
the symbol  "CYTO." For each quarter since the  beginning of 1996,  the high and
low sale prices for our common stock, as reported by Nasdaq, were as follows:

1996                                                              High      Low
- ----                                                              ----      ---
First Quarter................................................      10      5 1/8
Second Quarter...............................................   9 1/2    5 13/16
Third Quarter................................................       9     5 3/16
Fourth Quarter...............................................   7 1/8     4 7/16

1997
- ----
First Quarter................................................   6 1/2      4 3/4
Second Quarter...............................................  6 5/16    4 11/16
Third Quarter................................................  5 1/16      3 5/8
Fourth Quarter...............................................   4 3/4     1 7/16

1998
- ----
First Quarter................................................  2 7/16      1 1/4
Second Quarter...............................................       2        5/8
Third Quarter................................................  2 9/16        3/4
Fourth Quarter...............................................   1 7/8      11/16

1999
- ----
First Quarter................................................   1 1/2      14/16
Second Quarter...............................................       2        7/8



                                 DIVIDEND POLICY

     We have never paid or declared any cash  dividends on our common stock.  We
currently intend to retain any future earnings for our business and,  therefore,
do not  anticipate  paying cash  dividends  in the  foreseeable  future.  Future
dividends,  if  any,  will  depend  on,  among  other  things,  our  results  of
operations,  capital  requirements,  restrictions in loan agreements and on such
other  factors  as our  Board of  Directors,  in its  discretion,  may  consider
relevant.

                                 USE OF PROCEEDS

     We intend to use  substantially all of the proceeds from the sale of common
stock hereunder for general corporate purposes.


                                       19
<PAGE>

Important Factors Regarding Forward Looking Statements

     Certain   discussions   set  forth  above  regarding  the  development  and
commercialization   of  our  products  and   technologies  are  forward  looking
statements  that are subject to risks and  uncertainties.  The statements  under
this caption are intended to serve as cautionary  statements  within the meaning
of the Private  Securities  Litigation Reform Act of 1995. Certain statements in
this prospectus are forward-looking statements within the meaning of Section 27A
of the Securities Act and Section 21E of the Securities Exchange Act of 1934, as
amended.  The  Company's  actual  results  could  differ  materially  from those
anticipated in such  forward-looking  statements as a result of certain factors,
including those discussed in Risk Factors,  listed below or discussed  elsewhere
in this  prospectus,  and in the  Company's  filings  with  the  Securities  and
Exchange Commission:

     (i) the Company's  ability to continue as a going concern if the Company is
unable  to raise  sufficient  funds  or  generate  sufficient  cash  flows  from
operations to cover the cost of its  operations;  (ii) the Company's  ability to
access the  capital  markets  in the near term and in the  future for  continued
funding of  existing  projects  and for the pursuit of new  projects;  (iii) the
Company's ability to complete its  restructuring  plans timely and in a way that
permits  the  Company to operate  effectively;  (iv) the  ability to attract and
retain  personnel  needed for business  operations and strategic  plans; (v) the
timing and results of clinical studies,  and regulatory  approvals;  (vi) market
acceptance of the Company's products,  including programs designed to facilitate
use of the products,  such as the PIE Program;  (vii) demonstration over time of
the  efficacy  and  safety  of the  Company's  products;  (vii)  the  degree  of
competition from existing or new products;  (ix) the decision by the majority of
public and private insurance  carriers on whether to reimburse  patients for the
Company's products;  (x) the profitability of its products;  (xi) the ability to
attract,  and  the  ultimate  success  of,  strategic  partnering  arrangements,
collaborations, and acquisition candidates; (xii) the ability of the Company and
its partners to identify new products as a result of those  collaborations  that
are capable of achieving FDA approval,  that are cost-effective  alternatives to
existing  products  and that are  ultimately  accepted  by the key  users of the
product;  and  (xiii)  the  success of the  Company  in  establishing  marketing
programs  and in  obtaining  marketing  approvals  in  Canada  and  in  European
countries,  in achieving milestones and achieving sales of products resulting in
royalties;  and  (xiv)  the  ability  to  protect  and  practice  the  Company's
intellectual property, including patents and know-how.

     Any  forward-looking  statements are made as of the date of this prospectus
and the  Company  assumes  no  obligation  to  update  any such  forward-looking
statements or to update the factors  which could cause actual  results to differ
materially from those anticipated in such forward-looking statements.


                       WHERE YOU CAN FIND MORE INFORMATION

     The  Company  has  filed  with  the  Securities  and  Exchange  Commission,
Washington,  D.C.  20549,  a  Registration  Statement  on  Form  S-3  under  the
Securities Act with respect to the shares of common stock offered  hereby.  This
prospectus does not contain all of the information set forth in the Registration
Statement and the exhibits and schedules thereto.  For further  information with
respect to the Company and the common stock offered hereby, reference is made to
the  Registration  Statement  and the exhibits and  schedules  filed  therewith.
Statements  contained in this  prospectus  as to the contents of any contract or
any  other  document  referred  to are  not  necessarily  complete,  and in each
instance  reference is made to the copy of such contract or other document filed
as an exhibit to the Registration Statement, each such statement being qualified
in all respects by such reference.  A copy of the Registration  Statement may be
inspected  without charge at the offices of the  Commission in Washington,  D.C.
20549,  and  copies  of all or any  part of the  Registration  Statement  may be
obtained from the Public Reference Section of the Commission,  Washington,  D.C.
20549 upon the payment of the fees prescribed by the Commission.  The Commission

                                       20
<PAGE>

maintains  a Web site  (http://www.sec.gov)  that  contains  reports,  proxy and
information statements and other information regarding registrants,  such as the
Company,  that  file  electronically  with  the  Commission.  The  Company  also
maintains a Web site (http://www.cytogen.com).


                              Plan of Distribution

     We plan to offer shares of common stock  registered  hereby directly to The
State of Wisconsin  Investment Board at a discount of % from the public offering
price.

     Our common  stock is listed on the  Nasdaq  Stock  Market  under the symbol
"CYTO."

     We will bear all expenses of registering  the common stock  hereunder.

     The terms of any sales of any of the common stock registered hereby will be
set  forth  in a  final  prospectus  filed  with  the  Securities  and  Exchange
Commission.

                 INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE

     The following  documents have been filed with the Commission by the Company
and are  incorporated  herein by  reference in this  Prospectus  and made a part
hereof (i) the Company's  Annual Report on Form 1O-K for the year ended December
31, 1998; (ii) the Company's Quarterly Report on Form 10-Q for the quarter ended
March 31, 1999; and (ii) all documents filed by the Company  pursuant to Section
13(a),  13(c), 14 or 15(d) of the Exchange Act after the date of this Prospectus
and prior to the termination of the offering of the Common Stock shall be deemed
to be  incorporated by reference in this Prospectus and to be a part hereof from
the date of  filing  such  documents.  Any  statement  contained  in a  document
incorporated or deemed to be incorporated by reference herein shall be deemed to
be modified or superseded  for purposes of this  Prospectus to the extent that a
statement  contained  herein or in any other  subsequently  filed document which
also  is or is  deemed  to be  incorporated  by  reference  herein  modifies  or
supersedes such statement.  Any statement so modified or superseded shall not be
deemed,  except as so  modified  or  superseded,  to  constitute  a part of this
Prospectus.  The Company will provide without charge to each person to whom this
Prospectus is delivered, upon the written or oral request of such person, a copy
of any or all of the foregoing documents incorporated herein by reference, other
than  exhibits  to  such  documents   (unless  such  exhibits  are  specifically
incorporated  by reference  into such  documents).  Requests for such  documents
should be  submitted  in  writing to Cytogen  Corporation,  Attention:  Investor
Relations,  600 College Road East,  CN 5308,  Princeton  New Jersey  08540-5308,
Telephone:(609) 750-8224.

                              --------------------

     No person has been  authorized in connection  with the offering made hereby
to give  any  information.  or make any  representation  not  contained  in this
Prospectus and, if given or made, such information or representation must not be
relied upon as having been  authorized by the Company or any other person.  This
Prospectus  does not constitute an offer to sell or solicitation of any offer to
buy any of the  Securities  offered  hereby in any  jurisdiction  in which it is
unlawful  to make such  offer or  solicitation.  Neither  the  delivery  of this
Prospectus nor any sale made hereunder shall,  under any  circumstances,  create
any implication that the information  contained herein is correct as of any date
subsequent to the date hereof


                                       21

<PAGE>
                                 LEGAL MATTERS

     The  validity of the shares of Common Stock  offered  hereby will be passed
upon for the Company by Donald F. Crane, Jr., esq.


                                     EXPERTS

     The audited consolidated financial statements of the Company as of December
31, 1998 and 1997,  and for each of the three years in the period ended December
31, 1998 incorporated by reference in this Prospectus and registration statement
have been  audited by Arthur  Andersen  LLP,  independent  public  accounts,  as
indicated  in their  report with respect  thereto,  and are  included  herein in
reliance upon the authority of said firm as experts in giving said reports.



                                       22

<PAGE>





                                     Shares



                               CYTOGEN CORPORATION


                                  Common Stock



                              --------------------

                                   PROSPECTUS
                              --------------------










                               _________ __, 1999





<PAGE>


                                     Part II

                     INFORMATION NOT REQUIRED IN PROSPECTUS

ITEM 14.  Other Expenses of Issuance and Distribution

     The  following  is an itemized  statement of the  estimated  amounts of all
expenses  payable by the Registrant in connection  with the  registration of the
common stock offered hereby, other than underwriting discounts and commissions:

    Registration Fee-Securities and Exchange Commission................ $  1,955
    Blue Sky fees and expenses.........................................        -
    Accountants' fees and expenses.....................................    5,000
    Legal fees and expenses............................................   10,000
    Printing and engraving expenses....................................        -
    Transfer agent and registrar fees..................................      250
    Miscellaneous......................................................      500
         Total.........................................................  $17,705
                                                                         =======

ITEM 15. Indemnification of Directors and Officers

     Section 145(a) of the General Corporation Law of the State of Delaware (the
"DGCL") provides that a Delaware corporation may indemnify any person who was or
is a party or is  threatened  to be made a party to any  threatened,  pending or
completed action, suit or proceeding, whether civil, criminal, administrative or
investigative  (other than an action by or in the right of the  corporation)  by
reason of the fact that he is or was a director,  officer,  employee or agent of
the  corporation  or is or was  serving at the request of the  corporation  as a
director,  officer,  employee  or agent of another  corporation  or  enterprise,
against expenses,  judgments,  fines and amounts paid in settlement actually and
reasonably incurred by him in connection with such action, suit or proceeding if
he acted in good faith and in a manner he  reasonably  believed  to be in or not
opposed to the best  interests  of the  corporation,  and,  with  respect to any
criminal action or proceeding, had no cause to believe his conduct was unlawful.

     Section  145(b)  of the  DGCL  provides  that a  Delaware  corporation  may
indemnify  any person who was or is a party or is  threatened to be made a party
to any threatened, pending or completed action or suit by or in the right of the
corporation  to procure a judgment  in its favor by reason of the fact that such
person acted in any of the capacities set forth above, against expenses actually
and reasonably  incurred by him in connection  with the defense or settlement of
such  action  or  suit if he  acted  under  similar  standards,  except  that no
indemnification may be made in respect of any claim, issue or matter as to which
such person shall have been adjudged to be liable to the corporation  unless and
only to the extent that the court in which such action or suit was brought shall
determine that despite the adjudication of liability,  such person is fairly and
reasonably  entitled to be  indemnified  for such expenses which the court shall
deem proper.

     Section 145 of the DGCL further  provides  that to the extent a director or
officer of a corporation has been successful in the defense of any action,  suit
or proceeding  referred to in  subsections  (a) and (b) or in the defense of any
claim,  issue, or matter therein,  he shall be indemnified  against any expenses
actually  and  reasonably  incurred  by  him  in  connection   therewith;   that
indemnification  provided for by Section145 shall not be deemed exclusive of any
rights to which the indemnified party may be entitled;  and that the corporation
may purchase  and  maintain  insurance on behalf of a director or officer of the
corporation against any liability asserted against him or incurred by him in any

                                      II-1
<PAGE>
such  capacity  or  arising  out  of his  status  as  such  whether  or not  the
corporation would have the power to indemnify him against such liabilities under
Section 145.

     Section  102(b)(7) of the DGCL provides that a corporation  in its original
certificate  of  incorporation  or an  amendment  thereto  validly  approved  by
stockholders  may eliminate or limit personal  liability of members of its board
of  directors  or  governing  body for breach of a  director's  fiduciary  duty.
However,  no such  provision  may eliminate or limit the liability of a director
for  breaching  his duty of loyalty,  failing to action good faith,  engaging in
intentional  misconduct  or  knowingly  violating  a law,  paying a dividend  or
approving  a stock  repurchase  which was  illegal,  or  obtaining  an  improper
personal benefit.  A provision of this type has no effect on the availability of
equitable  remedies,  such as injunction or rescission,  for breach of fiduciary
duty.  The  Company's  Restated  Certificate  of  Incorporation  contains such a
provision.

     The Company's  Certificate of  Incorporation  and By-Laws  provide that the
Company shall indemnify  officers and directors and, to the extent  permitted by
the Board of Directors,  employees and agents of the Company, to the full extent
permitted  by and in the  manner  permissible  under  the  laws of the  State of
Delaware.  In addition,  the By-Laws  permit the Board of Directors to authorize
the Company to purchase and maintain  insurance  against any liability  asserted
against any director,  officer,  employee or agent of the Company arising out of
his capacity as such.

ITEM 16. Exhibits and Financial Statement Schedules

     (a) Exhibits

3.1      --  Certificate  of  Incorporation  of  the  Registrant,  restated  and
         amended.  Filed as an  exhibit  to Form 10-Q  Quarterly  Report for the
         quarter  ended  June  30,  1996   (Commission  File  No.  0-14879)  and
         incorporated herein by reference.

3.2      -- By-Laws  of the  Registrant,  as  amended.  Filed as an  exhibit to
         Form S-4  Registration  Statement  (No.  33-88612)  and incorporated
         herein by reference.

4.1      -- Specimen  Certificate  for common stock of the Registrant.  Filed as
         an exhibit to Amendment No. 1 to Form S-1  Registration Statement
         (No. 33-5533) and incorporated herein by reference.

5.1      -- Opinion of Donald F. Crane, Jr., esq.  Filed herewith.

10.1     -- Stock Exchange Agreement between the Registrant and Prostagen, Inc.
         Filed herewith.

10.2     -- Limited Liability Company Agreement of PSMA Development Company LLC,
         dated June 15, 1999.  Filed herewith.  Confidential  treatment has been
         requested.  The copy filed as an exhibit omits the information  subject
         to the confidentiality request.

10.3     -- PSMA/PSMP License Agreement by and among Progenics  Pharmaceuticals,
         Inc., Cytogen Corporation,  PSMA Development Company LLC dated June 15,
         1999.  Filed  herewith.   The  copy  filed  as  an  exhibit  omits  the
         information subject to the confidentiality request.

21.1     -- List of Subsidiaries.  Filed as an exhibit to Form 10-K Annual
         Report for the year ended December 31, 1998 (Commission File No.
         0-14879)and incorporated herein by reference.

23.1     -- Consent of Arthur Andersen LLP.  Filed herewith.


                                      II-2

<PAGE>
23.2    -- Consent of counsel as to legal opinion (included in Exhibit 5.1)

24.1     -- Power of Attorney (included on page II-5)


- -----------------



ITEM 17. Undertakings

     The   undersigned   Registrant   hereby   undertakes   to  provide  to  the
underwriters,   at  the  closing   specified  in  the  underwriting   agreement,
certificates in such  denominations  and registered in such names as required by
the underwriters to permit prompt delivery to each purchaser.

     Insofar as indemnification for liabilities arising under the Securities Act
of 1933 may be permitted to directors,  officers and controlling  persons of the
Registrant pursuant to the foregoing  provisions,  or otherwise,  the Registrant
has been advised that in the opinion of the Securities  and Exchange  Commission
such  indemnification  is against  public policy as expressed in the Act and is,
therefore,  unenforceable. In the event that a claim for indemnification against
such  liabilities  (other than the payment by the  Registrant in the  successful
defense of any action, suit or proceeding) is asserted by such director, officer
or controlling  person in connection with the securities being  registered,  the
Registrant  will,  unless in the  opinion  of its  counsel  the  matter has been
settled by controlling precedent,  submit to a court of appropriate jurisdiction
the question  whether such  indemnification  by it is against  public  policy as
expressed  in the Act and will be  governed  by the final  adjudication  of such
issue.

The undersigned  registrant  hereby undertakes that, for purposes of determining
any liability under the Securities Act of 1933, each filing of the  registrant's
annual  report  pursuant  to section  13(a) or section  15(d) of the  Securities
Exchange  Act of 1934 that is  incorporated  by  reference  in the  registration
statement  shall be deemed to be a new  registration  statement  relating to the
securities  offered  therein,  and the offering of such  securities at that time
shall be deemed to be the initial bona fide offering thereof.

The undersigned Registrant hereby undertakes that:

                  (1) For  purposes  of  determining  any  liability  under  the
         Securities  Act of  1933,  the  information  omitted  from  the form of
         prospectus  filed as part of this  registration  statement  in reliance
         upon  Rule  430A and  contained  in a form of  prospectus  filed by the
         Registrant  pursuant  to Rule  424(b)(1)  or (4) or  497(h)  under  the
         Securities  Act  shall  be  deemed  to be  part  of  this  registration
         statement as of the time it was declared effective.

                  (2) For the purpose of  determining  any  liability  under the
         Securities Act of 1933, each  post-effective  amendment that contains a
         form of prospectus shall be deemed to be a new  registration  statement
         relating to the securities  offered  therein,  and the offering of such
         securities  at the time  shall be  deemed to be the  initial  bona fide
         offering thereof.



                                      II-3

<PAGE>


                                   SIGNATURES

     Pursuant to the  requirements of the Securities Act of 1933, the Registrant
has duly caused this  Registration  Statement  to be signed on its behalf by the
undersigned,  thereunto duly authorized, in the City of Princeton,  State of New
Jersey, on July 19,1999.

                                                      CYTOGEN CORPORATION


                                                      By:  /s/ H. Joseph Reiser
                                                         -----------------------
                                                         H. Joseph Reiser
                                                         Chief Executive Officer
                                                          and President



                                POWER OF ATTORNEY

     KNOW ALL MEN BY THESE PRESENTS,  that each person whose  signature  appears
below  constitutes  and appoints H. Joseph Reiser,  Jane M. Maida,  or Donald F.
Crane,  Jr., and each of them, as his or hers true and lawful  attorneys-in-fact
and agents, with full power of substitution and  resubstitution,  for him and in
his  name,  place  and  stead,  in any and all  capacities,  to sign any and all
amendments  (including  post-effective   amendments)  and  supplements  to  this
registration  statement or any prospectus included herein, and to file the same,
with the Commission,  granting unto said  attorneys-in-fact and agents, and each
of them, full power and authority to do and perform each and every act and thing
requisite  and  necessary to be done in  connection  therewith,  as fully to all
intents and  purposes as he might or could do in person,  hereby  ratifying  and
confirming all that said  attorneys-in-fact and agents, or any of them, or their
or his substitute or substitutes,  may lawfully do or cause to be done by virtue
hereof.

     Pursuant to the  requirements  of the  Securities  Act of 1933, as amended,
this Registration Statement has been signed by the following persons on July 19,
1999 in the capacities indicated:



Signature                                 Title                         Date
- ---------                                 -----                         ----
/s/ H. Joseph Reiser             Chief Executive Officer and       July 19, 1999
- -----------------------
    H. Joseph Reiser             President (Principal Executive
                                 Officer and Director)
/s/ Jane M. Maida                Chief Accounting Officer          July 19, 1999
- -----------------
    Jane M. Maida                (Principal Accounting Officer)

/s/ John E. Bagalay, Jr.         Director                          July 19, 1999
- ------------------------
    John E. Bagalay, Jr.

/s/ Ronald J. Brenner            Director                          July 19, 1999
- ---------------------
    Ronald J. Brenner

/s/ Stephen K. Carter            Director                          July 19, 1999
- ---------------------
     Stephen K. Carter

/s/  James A. Grigsby            Chairman                          July 19, 1999
- ---------------------
      James A. Grigsby


                                      II-4
<PAGE>



/s/  Robert F. Hendrickson       Director                          July 19, 1999
- --------------------------
      Robert F. Hendrickson



                                  II-5


                                                   EXHIBIT 5.1

July 19, 1999

Cytogen Corporation
600 College Road East
Princeton, New Jersey 08540

Ladies and Gentlemen:

The undersigned has acted as counsel to Cytogen Corporation, a Delaware
corporation (the "Company"), in connection with the preparation and filing by
the Company of a Registration Statement on Form S-3 (the "Registration
Statement") under the Securities Act of 1933, as amended (the "Act"), for the
registration of up to $5 million in shares of common stock, $.01 par value per
share (the "Common Stock"), of the Company.

I have examined and am familiar with originals or copies, certified or otherwise
identified to our satisfaction, of such documents, corporate records,
certificates of public officials and officers of the Company and such other
instruments as I have deemed necessary or appropriate as a basis for the
opinions expressed below, including the Registration Statement, the Restated
Certificate of Incorporation of the Company and the By-laws of the Company.

Based on the foregoing, I am of the opinion that the Common Stock issuable
under the Registration Statement has been duly authorized and reserved for
issuance and, when duly issued and delivered, will be validly issued, fully paid
and nonassessable.

I hereby consent to the filing of this opinion as Exhibit 5.1 to the
Registration Statement.  In giving such consent, I do not thereby admit
that we come within the category of persons whose consent is required under
Section 7 of the Act or the rules and regulations of the Securities and Exchange
Commission thereunder.

I express no opinion as to the laws of any jurisdiction other than the
general corporate laws of the State of Delaware and the federal law of the
United States of America. The foregoing opinion is rendered as of the date
hereof, and I assume no obligation to update such opinion to reflect any facts
or circumstances which may hereafter come to my attention or any changes in the
law which may hereafter occur.

                                       Very truly yours,



                                       /s/ Donald F. Crane
                                      -------------------------
                                      Donald F. Crane, Jr.




                                                                    Exhibit 10.1

                            STOCK EXCHANGE AGREEMENT




                                      among


                               CYTOGEN CORPORATION


                                       and


                        THE STOCKHOLDERS AND DEBTHOLDERS
                               OF PROSTAGEN, INC.



                            Dated as of June 15, 1999




<PAGE>


                                Table of Contents


ARTICLE I SALE AND PURCHASE OF SHARES.........................................1
     Section 1.1. Closing.....................................................1
     Section 1.2. Deliveries by the Sellers...................................1
     Section 1.3. Deliveries by the Purchaser.................................1
     Section 1.4. Other Closing Matters.......................................2
     Section 1.5. Post Closing Adjustment.....................................2
     Section 1.6. Contingent Payments.........................................4
     Section 1.7. Cancellation................................................5

ARTICLE II REPRESENTATIONS AND WARRANTIES OF THE SELLERS......................5
     Section 2.1. Organization................................................5
     Section 2.2. Capitalization..............................................6
     Section 2.3. Binding Nature of this Agreement............................6
     Section 2.4. Consents and Approvals; No Violations.......................7
     Section 2.5. Financial Statements........................................7
     Section 2.6. Absence of Certain Changes..................................8
     Section 2.7. No Undisclosed Liabilities..................................8
     Section 2.8. Litigation..................................................9
     Section 2.9. No Default..................................................9
     Section 2.10.Permits; Compliance with Applicable Law.....................9
     Section 2.11.Taxes and Tax Returns.......................................9
     Section 2.12.Employee Benefit Plans.....................................13
     Section 2.13.Intellectual Property......................................15
     Section 2.14.Transactions with Affiliates...............................15
     Section 2.15.Contracts..................................................15
     Section 2.16.Labor Relations............................................16
     Section 2.17.Environmental..............................................16
     Section 2.18.Ownership of Assets........................................18
     Section 2.19.Insurance..................................................18
     Section 2.20.Real Property..............................................18
     Section 2.21.Share Ownership............................................19
     Section 2.22.Investment.................................................19
     Section 2.23.Accredited Investor........................................19
     Section 2.24.No Misleading Statements...................................20
     Section 2.25.No Exclusive Manufacturing Rights..........................20

ARTICLE III REPRESENTATIONS AND WARRANTIES OF THE PURCHASER .................20
     Section 3.1. Organization...............................................20
     Section 3.2. Capitalization.............................................20
     Section 3.3. Authority Relative to this Agreement.......................21
     Section 3.4. Consents and Approvals; No Violations......................21
     Section 3.5. SEC Reports; Financial Statements..........................22
     Section 3.6. Absence of Certain Changes.................................22


                                       ii
<PAGE>
ARTICLE IV COVENANTS.........................................................22
     Section 4.1. Further Assurances.........................................23
     Section 4.2. Brokers or Finders.........................................23
     Section 4.3. Performance of Obligations.................................23
     Section 4.4. Tax Covenants..............................................23
     Section 4.5. Employees; Releases........................................23
     Section 4.6. NWB Board..................................................24
     Section 4.7. Lockup.....................................................24

ARTICLE V SURVIVAL; INDEMNIFICATION..........................................24
     Section 5.1. Survival Periods...........................................24
     Section 5.2. Indemnification............................................25
     Section 5.3. Indemnification Amounts....................................25
     Section 5.4. Claims.....................................................26
     Section 5.5. Indemnification with Respect to Taxes......................27
     Section 5.6. Exclusive Remedy...........................................28

ARTICLE VI MISCELLANEOUS.....................................................28
     Section 6.1. Notices....................................................28
     Section 6.2. Headings...................................................29
     Section 6.3. Counterparts...............................................29
     Section 6.4. Entire Agreement; Assignment...............................29
     Section 6.5. Governing Law..............................................29
     Section 6.6. Specific Performance.......................................30
     Section 6.7. Publicity..................................................30
     Section 6.8. Binding Nature; No Third Party Beneficiaries...............30
     Section 6.9. Severability...............................................30
     Section 6.10.Interpretation.............................................30
     Section 6.11.Payment of Expenses........................................30


                                    Exhibits

         Exhibit A:        Allocation
         Exhibit B:        Registration Rights Agreement


                                      iii
<PAGE>

     STOCK  EXCHANGE  AGREEMENT,  dated  as  of  June  15,  1999  among  Cytogen
Corporation, a Delaware corporation (the "Purchaser"),  and the stockholders and
the  holders  of  certain  rights  to  receive  cash  (the  "Debtholders",  and,
collectively,  the "Sellers") of Prostagen,  Inc., a Delaware  corporation  (the
"Company").

     WHEREAS, the Purchaser has agreed to acquire from the stockholders, and the
stockholders have agreed to sell to the Purchaser, all of the outstanding shares
of common  stock,  par value  $0.001 per share,  of the  Company  (the  "Company
Shares"),  and the Debtholders  have agreed to cancel such debt, in each case in
exchange for shares of common  stock,  par value $.01 per share (the  "Purchaser
Shares"), of the Purchaser, on the terms and subject to the conditions set forth
herein.

     NOW, THEREFORE, the parties agree as follows:

                                   ARTICLE I
                           SALE AND PURCHASE OF SHARES

     Section 1.1. Closing. The closing of the transactions  contemplated by this
Agreement (the "Closing") is taking place  simultaneously  with the execution of
this  Agreement,  at the  offices of Dewey  Ballantine  LLP,  1301 Avenue of the
Americas,  New  York,  New  York.  The  date on  which  the  Closing  occurs  is
hereinafter referred to as the "Closing Date."

     Section 1.2. Deliveries by the Sellers.  At the Closing,  the Sellers shall
deliver or cause to be delivered to the Purchaser the following:

     (a) Certificates for all of the outstanding  Company Shares,  duly endorsed
in blank,  or  accompanied  by stock  powers duly  executed  in blank,  with any
necessary stock transfer tax stamps attached or provided for;

     (b) Cancelled  demand  promissory notes held by Max Link, S. Leslie Misrock
and CC Consulting A/S and a release to the Company of the funds held pursuant to
the escrow agreement in favor of Alan Fox;

     (c) a  certificate  of exemption  from  withholding  as provided in Section
1445(b) of the Code (as hereinafter  defined) and Treasury  Regulation  1.1445-2
(the "FIRPTA Certificate"); and

     (d) such other duly executed  documents and  certificates  as the Purchaser
may reasonably request.

     Section 1.3. Deliveries by the Purchaser.

     (a) At the Closing, or as promptly as practicable thereafter, but not later
than three  Nasdaq  trading days after the Closing  Date,  the  Purchaser  shall
deliver or cause to be  delivered  to the Sellers  certificates  representing  a

<PAGE>
number of the  Purchaser  Shares equal to $2 million  divided by the  Conversion
Number. Such Purchaser Shares shall be allocated among the Sellers in accordance
with Exhibit A to this Agreement.

     (i) If the  Purchaser  Market  Value (as defined  below) is greater than or
equal to $1-1/32,  then the  Conversion  Number  shall be the  Purchaser  Market
Value.

     (ii) If the  Purchaser  Market  Value is less than $1-1/32 and greater than
$31/32, then the Conversion Number shall be $1.

     (iii) If the  Purchaser  Market  Value is less than or equal to $31/32  and
greater than $.50,  then the  Conversion  Number shall be the  Purchaser  Market
Value.

     (iv) If the Purchaser  Market Value is less than or equal to $.50, then the
Conversion Number shall be $.50.

     (v) The Purchaser Market Value shall equal the average of the closing price
of the Purchaser Shares, as reported by Nasdaq,  for the ten trading days ending
on the second trading day prior to the Closing Date.

     (b)  Notwithstanding  anything  in this  Section 1.3 to the  contrary,  the
Purchaser shall not be required to deliver any fractional  Purchaser  Shares. In
lieu  thereof,   amounts  delivered  under  this  Section  1.3  to  any  Company
shareholder shall be rounded to the nearest whole share.

     Section 1.4. Other Closing Matters.

     (a) The  management of Purchaser  shall  consider the election of S. Leslie
Misrock and Alan Fox to the Purchaser's Board of Directors.

     (b) At  the  Closing,  the  Purchaser  and  S.  Leslie  Misrock,  Esq.,  as
representative  for  the  Sellers  (the  "Representative"),  shall  execute  the
Registration Rights Agreement in the form of Exhibit B hereto. The Sellers,  and
each of them,  irrevocably appoint the Representative as their  attorney-in-fact
to act for them and in their name in  connection  with all  matters  relating to
this Stock Exchange Agreement and the Registration Rights Agreement.

     Section  1.5.  Post  Closing  Adjustment.  (a) If the Closing Date Cash (as
defined  below) is less than  $550,000,  the Sellers shall pay the difference to
the Purchaser.  If the Closing Date Liabilities (as defined below) are more than
$25,000,  the Sellers  shall pay the  difference to the  Purchaser.  Any payment
shall be  accompanied  by interest  on such amount from the Closing  Date to the
date of payment at a floating rate equal to the publicly announced prime lending
rate of Citibank,  N.A. Any payment by the Sellers  under this Section 1.5 shall
be paid in the Purchaser Shares valued at the Conversion Number.


                                       2
<PAGE>

     (b) As promptly as practicable  following the Closing Date, but in no event
more than 45 days  following the Closing Date,  the Purchaser  shall prepare and
deliver to the  Representative  a  consolidated  balance sheet setting forth the
total assets and total liabilities of the Company and its subsidiaries as of the
Closing Date (the "Closing Date Balance  Sheet"),  in accordance with clause (f)
below.  The  Representative  and his accountants will be entitled to observe the
preparation  of the  Closing  Date  Balance  Sheet  and  shall be  granted  such
information and access as they may reasonably request in connection therewith.

     (c) Unless  within 20 days after its  receipt of the Closing  Date  Balance
Sheet, the Representative  shall deliver to the Purchaser a statement describing
its objections  thereto,  the amounts  determined in accordance  with clause (b)
shall be final and binding for purposes of this Section 1.5.

     (d) If the Representative shall deliver the statement referred to in clause
(c) above, the  Representative  and the Purchaser will use reasonable efforts to
resolve any disputes,  but if a final  resolution is not reached  within 20 days
after the  Representative  has submitted its objections,  any remaining disputes
will be resolved by the Reviewing  Accountants.  The Reviewing Accountants shall
be instructed to resolve any matters in dispute as promptly as practicable.  The
determination  of the  Reviewing  Accountants  will be  final  and  binding  for
purposes of this Section 1.5.

     (e) The  Purchaser,  on the one hand,  and the Sellers,  on the other hand,
shall each pay  one-half of the fees and expenses of the  Reviewing  Accountants
and  shall  cooperate,   including  by  furnishing  any  information  reasonably
requested,  with each other and such  accounting  firm in the  resolution of any
disputes.  The Sellers  shall  satisfy  such  obligation  to pay one-half of the
Reviewing  Accountant's  fees and  expenses  by causing  the  Representative  to
deliver to the  Purchaser a number of Purchaser  Shares  (rounded to the nearest
whole share) equal to the Seller's  portion of such fees and expenses divided by
the Conversion Number.

     (f)  "Closing  Date  Cash"  will be  equal to (i) the  total  cash and cash
equivalents less (ii) the total current  liabilities,  in each case set forth on
the Closing  Date Balance  Sheet  finally  determined  in  accordance  with this
Section 1.5.  "Closing Date Liabilities " will be equal to the total liabilities
(other than current  liabilities)  set forth on the Closing  Date Balance  Sheet
finally determined in accordance with this Section 1.5, plus the total amount of
all other liabilities (other than current liabilities  reflected on such balance
sheet,  and other than contingent  liabilities).  The Closing Date Balance Sheet
shall  be  prepared  in  accordance  with  U.S.  generally  accepted  accounting
principles ("GAAP") applied on a basis consistent with the accounting principles
used in preparation of the audited balance sheets delivered  pursuant to Section
2.5 hereof and in all  respects as if the Closing  Date were the end of a fiscal
year.  The Closing Date  Balance  Sheet need not include any  information  which
would not affect the  calculation  of the Closing  Date Cash or the Closing Date
Liabilities.


                                       3
<PAGE>

     Section 1.6. Contingent Payments.

     (a) The Purchaser shall deliver to the Representative a number of Purchaser
Shares equal to $2 million  divided by the Conversion  Number  (recomputed as of
the date of payment) on the earlier of (x) five days  following  the filing of a
New Drug  Application or Biologic License  Application,  as the case may be, for
dendritic cell therapy by Northwest Biotherapeutics, Inc. ("NWB") or (y) January
1, 2002.

     (b) The Purchaser shall deliver to the Representative a number of Purchaser
Shares equal to $2 million  divided by the Conversion  Number  (recomputed as of
the date of payment) on the earlier of (x) five days following the  demonstrated
efficacy of immunotherapy (vaccine or radioimmunotherapy) at the end of Phase II
clinical  trials,  as  evidenced  solely by  commencement  of Phase III clinical
trials or (y) January 1, 2004.

     (c)  Notwithstanding  the  foregoing,  (1) no  payment  shall be made under
clause (a)(x) of this Section 1.6 unless at the  scheduled  time of such payment
the dendritic  cell therapy  program is  continuing  and (2) no payment shall be
made under clause (a)(y) or of this Section 1.6 unless at the scheduled  time of
such payment the dendritic  cell therapy  program is  continuing  and safety has
been demonstrated in clinical trials.

     (d)  Notwithstanding  the  foregoing,  (1) no  payment  shall be made under
clause (b)(x) of this Section 1.6 unless at the  scheduled  time of such payment
the immunotherapy (vaccine or radioimmunotherapy)  program is continuing and (2)
no payment  shall be made under clause  (b)(y) of this Section 1.6 unless at the
scheduled time of such payment the immunotherapy (vaccine or radioimmunotherapy)
program is continuing and safety has been demonstrated in clinical trials.

     (e) On the date the  payment  contemplated  by Section  1.6(b) is due,  the
Purchaser shall deliver to the Representative a number of Purchaser Shares equal
to  $500,000  divided  by the  Conversion  Number at such time as the  exclusive
manufacturing  right relating to Prostate  Specific  Membrane  Antigen  ("PSMA")
granted to Northwest  Clinicals  LLC ("NWC")  shall have been  cancelled or made
non-exclusive.  Any amount  payable  pursuant to this  Section  1.6(e)  shall be
decreased  by (x) any  amounts  paid,  payable or which  would be payable to any
third party,  including NWC, in connection with any such manufacturing  right or
the  cancellation  thereof and (y) with respect to arrangements  between NWB, on
the one hand, and the Purchaser or the Company, or both, on the other hand, that
are made  with the  approval  of S.  Leslie  Misrock,  such  approval  not to be
unreasonably  withheld,  the excess,  if any,  of the net  present  value of the
royalty  payments  under the  license  agreement  between  the  Company  and the
Purchaser  relating to PSMA over the net present  value of the royalty  payments
under the sublicense relating to such license,  between the Company and NWB (net
present  value to be  calculated  using the  publicly  announced  prime  rate of
Citibank, N.A.).

     (f) On or before the date which is six months  from the Closing  Date,  the
Purchaser  shall pay, as set forth in this Section  1.6(f),  an amount,  if any,
equal to (i) $450,000  divided by the Conversion  Number less (ii) the amount of

                                       4
<PAGE>
Unsettled  Liabilities.  Unsettled  Liabilities  shall  mean any  amounts  paid,
payable or which  would be payable by the Company in respect of the lease on the
Company's office and other space in Allandale,  New Jersey.  In order to prevent
any  double-counting,  amounts  paid by the  Sellers  pursuant  to  Section  1.5
attributable  to the matters  covered by this  Section  1.6(e)  shall reduce the
amount of the Unsettled  Liabilities  on a  dollar-for-dollar  basis.  The first
$60,000 of such payment, if any, shall be paid in cash to S. Leslie Misrock. The
balance,  if any,  of such  payment  shall  be  paid  to the  Representative  in
Purchaser Shares valued at the Conversion Number.

     (g) It is  understood  that  certain  persons  who are not  parties to this
Agreement  will be entitled to payments  under this Section 1.6, as set forth in
Exhibit A. In order to prevent  any  double-counting,  any  payments  under this
Section 1.6 shall be reduced by such payments.

     Section  1.7.  Cancellation.  Effective  as of  immediately  prior  to  the
Closing,  all rights of the  Sellers (or any  affiliates)  under (a) any option,
warrant or right to acquire  any  securities  of the  Company and (b) any notes,
bonds, indentures or other evidences of indebtedness, are hereby cancelled, with
no  further  obligations  of  the  Company,   the  Purchaser  or  any  affiliate
thereunder.

                                   ARTICLE II
                  REPRESENTATIONS AND WARRANTIES OF THE SELLERS

     The  Sellers  severally  and  not  jointly  represent  and  warrant  to the
Purchaser  as  follows,  except as set forth in the  disclosure  schedule  being
delivered by the Sellers to the Purchaser concurrently herewith (the "Disclosure
Schedule"):

     Section 2.1.  Organization.  Each of the Company and its  subsidiaries is a
corporation duly organized, validly existing and in good standing under the laws
of the jurisdiction of its  organization  and has all requisite  corporate power
and authority and all necessary governmental approvals to own, lease and operate
its properties  and assets and to carry on its business as now being  conducted,
except where the failure to be so organized, existing and in good standing or to
have such power, authority, and governmental approvals would not have a Material
Adverse  Effect on the  Company.  As used  herein  with  respect  to an  entity,
"Material  Adverse  Effect"  shall  mean  an  event,  change  or  effect  which,
individually or together with all other events,  changes or effects, has had, or
is  reasonably  likely to have,  a  material  adverse  effect  on the  financial
condition, assets, liabilities, results of operations or business of that entity
and its subsidiaries  taken as a whole. The Company and each of its subsidiaries
is duly  qualified  or  licensed  to do  business  and in good  standing in each
jurisdiction in which the property owned, leased or operated by it or the nature
of the business conducted by it makes such qualification or licensing necessary,
except  where  the  failure  to be so duly  qualified  or  licensed  and in good
standing  would  not in the  aggregate  have a  Material  Adverse  Effect on the
Company.  The Company has delivered to the Purchaser true and complete copies of
its and its  subsidiaries  certificate of incorporation  and bylaws,  or similar
organizational  documents.  Notwithstanding anything herein to the contrary, NWC

                                       5
<PAGE>
shall not be considered a subsidiary of the Company.  S. Leslie Misrock does not
have  knowledge  that  were NWC a  subsidiary  of the  Company,  that any of the
representations  and  warranties  herein,  if made by the Company with regard to
NWC, would be untrue.

     Section  2.2.  Capitalization.  (a) The  authorized  capital  stock  of the
Company consists of 12,000,000  Shares and no preferred  shares.  As of the date
hereof  3,850,000  Shares  are  issued  and  outstanding.  On the  date  hereof,
1,250,000  of such  Shares  are being  contributed  to the  Company.  All of the
outstanding  shares of the Company's capital stock are duly authorized,  validly
issued,  fully paid and non-assessable.  Except as set forth above (i) there are
no shares of capital stock of the Company authorized,  issued or outstanding and
(ii) there are no options, warrants, calls, pre-emptive rights, subscriptions or
other rights, agreements, arrangements or commitments of any character, relating
to  the  issued  or  unissued  capital  stock  of  the  Company  or  any  of its
subsidiaries,  obligating  the  Company  or any of its  subsidiaries  to  issue,
transfer  or sell or cause to be  issued,  transferred  or sold  any  shares  of
capital  stock  of, or other  equity  interest  in,  the  Company  or any of its
subsidiaries or securities  convertible  into or exchangeable for such shares or
equity interests, or obligating the Company or any of its subsidiaries to grant,
extend or enter  into any such  option,  warrant,  call,  subscription  or other
right,  agreement,  arrangement or commitment and (iii) there are no outstanding
obligations of the Company or any of its  subsidiaries to vote or to repurchase,
redeem or otherwise  acquire any shares of capital stock of the Company,  or any
subsidiary  or  affiliate  of the  Company  or to  provide  funds  to  make  any
investment  (in the form of a loan,  capital  contribution  or otherwise) in any
subsidiary or any other entity.  Other than Shares, no securities of the Company
have the right to vote.

     (b) The Company has delivered to the Purchaser true and complete  copies of
all instruments  governing or defining rights under the Shares.  The Company has
delivered a true and complete  list of all holders of securities of the Company.
All such securities were issued in compliance with all applicable law, including
federal and state securities laws.

     (c) All of the outstanding shares of capital stock of each of the Company's
subsidiaries  are owned by the  Company,  directly or  indirectly,  and all such
shares have been validly issued and are fully paid and nonassessable and free of
preemptive rights and are owned by either the Company or one of its subsidiaries
free and clear of all liens, charges,  claims or encumbrances.  The Company owns
___  shares  of common  stock of NWB,  free and  clear of any  liens,  claims or
encumbrances.  The Sellers have delivered to the Purchaser a certificate setting
forth the number of shares of NWB common stock outstanding as of the date hereof
on a fully diluted basis. The Company does not, directly or indirectly, have any
equity or ownership interest in any other business, other than its subsidiaries.

     Section 2.3.  Binding  Nature of this  Agreement.  (a) Such Seller has full
power and authority to execute and deliver this  Agreement and to consummate the
transactions  contemplated  hereby.  This  Agreement  has been duly executed and

                                       6
<PAGE>
delivered by such Seller and is a valid and binding  obligation  of such Seller,
enforceable against such Seller in accordance with its terms.

     (b) The Board of Directors of the Company has taken all necessary action to
approve this Agreement and the transactions  contemplated hereby for purposes of
Section 203 of the  Delaware  General  Corporation  Law and the  certificate  of
incorporation and bylaws of the Company.

     Section 2.4. Consents and Approvals; No Violations.  Neither the execution,
delivery or performance of this Agreement by the Sellers nor the consummation by
the  Sellers  of the  transactions  contemplated  hereby nor  compliance  by the
Sellers or the Company with any of the provisions  hereof will (i) conflict with
or result in any breach of any provision of the certificate of  incorporation or
the bylaws (or similar  organizational  instrument)  of the Company or of any of
its  subsidiaries,  (ii)  require  any filing  with,  or permit,  authorization,
consent or approval of, any court, tribunal, administrative agency or commission
or other  governmental or other regulatory  authority or agency (a "Governmental
Entity") or any other  person or entity,  (iii)  result in a violation or breach
of,  or  constitute  (with or  without  due  notice  or lapse of time or both) a
default (or give rise to any right of  termination,  amendment,  cancellation or
acceleration),  result  in the  termination  of or a  right  of  termination  or
cancellation of,  modification of any benefit under,  accelerate the performance
required  by,  result  in  the  triggering  of any  payment  or  other  material
obligation  pursuant to, result in the creation of any lien,  security interest,
charge or encumbrance  upon any of the material  properties of the Sellers,  the
Company or its subsidiaries under, or result in being declared void, voidable or
without further binding effect any of the terms, conditions or provisions of any
note, bond, mortgage, indenture, lease, license, contract, permit, deed of trust
agreement or other instrument or commitment obligation to which the Sellers, the
Company or any of its  subsidiaries is a party or by which any of them or any of
their  properties  or assets may be bound or affected or (iv) violate any order,
writ, injunction, decree, statute, rule or regulation applicable to the Sellers,
the  Company,  any of its  subsidiaries  or any of their  properties  or assets,
excluding  from the  foregoing  clauses  (ii),  (iii) and (iv) such  violations,
breaches or defaults which would not, in the aggregate,  have a Material Adverse
Effect.

     Section 2.5. Financial  Statements.  Section 2.5 of the Disclosure Schedule
sets forth the consolidated balance sheets,  income statements and statements of
cash flow of the Company and its consolidated  subsidiaries at and for the years
ended December 31, 1997 and 1998 and the three month period ended March 31, 1999
(collectively,   the  "Financial  Statements").   Each  of  the  balance  sheets
(including  the related  notes)  included  in the  Financial  Statements  fairly
presents in all material respects the financial  position of the Company and its
consolidated  subsidiaries  as of the  respective  dates thereof and each of the
statements of income and cash flow (including the related notes) included in the
Financial  Statements  fairly  presents in all material  respects the results of
operations of the Company and its  consolidated  subsidiaries for the respective
periods then ended, except as otherwise noted therein.  The consolidated balance
sheet of the Company and its  consolidated  subsidiaries as of March 31, 1999 is
sometimes  referred  to as the  "Company  Balance  Sheet"  and such  date as the
"Balance Sheet Date." Each of the Financial  Statements has been (i) prepared in

                                       7
<PAGE>
accordance with GAAP consistently applied during the periods involved, except as
otherwise  noted  therein  and (ii)  prepared in  accordance  with the books and
records of the  Company.  The Company  maintains  adequate  books and records in
accordance with GAAP.

     Section 2.6. Absence of Certain Changes.  Since the Balance Sheet Date, (a)
each of the Company and its  subsidiaries has operated in the ordinary and usual
course of business,  (b) there have not occurred any events,  changes or effects
which have had or which could  reasonably  be likely to have a Material  Adverse
Effect,  and,  neither  the Company nor any of its  subsidiaries  has taken,  or
agreed to take, any action to:

     (i)  amend  its  Certificate  of   Incorporation   or  By-laws  or  similar
organizational documents, or alter through merger, liquidation,  reorganization,
restructuring or in any other fashion,  the corporate  structure or ownership of
the Company or any subsidiary;

     (ii) (A) declare,  set aside or pay any dividend or other distribution with
respect to its capital stock, (B) redeem, purchase or otherwise acquire directly
or indirectly any of its  securities,  (C) issue,  sell,  pledge,  dispose of or
encumber any securities (or any rights to acquire such securities) or (D) split,
combine or reclassify its outstanding capital stock;

     (iii)  acquire  or agree to  acquire,  any assets or  securities  either by
purchase, merger or otherwise;

     (iv) transfer,  lease,  license,  sell,  mortgage,  pledge,  dispose of, or
encumber  any  assets or  securities,  or  authorize,  propose  or  announce  an
intention to authorize or propose,  or enter into an agreement  with respect to,
any merger,  consolidation or business  combination or license or sublicense any
Intellectual  Property or otherwise dispose of any Intellectual  Property or any
interest therein;

     (v) modify,  amend or terminate any of its material contracts or engagement
with any third party, or waive, release or assign any material rights or claims,
or modify or amend the terms of any outstanding securities;

     (vi) make (or permit to be made) any Tax  election or settle or  compromise
any liability for taxes; or

     (vii) enter into an agreement,  contract,  commitment or  arrangement to do
any of the  foregoing,  or to  authorize,  recommend,  propose  or  announce  an
intention to do any of the foregoing.

     Section 2.7. No Undisclosed Liabilities.  There are no liabilities,  debts,
obligations  or claims  (absolute,  contingent,  known,  unknown  or  otherwise)
against the Company or its subsidiaries,  except liabilities, debts, obligations
or claims (a)  reflected or reserved in Company  Balance Sheet or (b) which were

                                       8
<PAGE>
incurred  after the Balance Sheet Date in the ordinary  course of business.  For
purposes of this  Agreement,  incurred in the  ordinary  course of business  (or
similar  formulations) shall mean (x) in accordance with the terms of a contract
listed in Section 2.7(x) of the Company Disclosure Schedule or (y) comparable in
nature and  magnitude to those  payments made in the prior year, as evidenced by
the general ledger delivered to the Purchaser prior to the date hereof.

     Section 2.8.  Litigation.  There is no suit, claim,  action,  proceeding or
investigation  pending or, to the best  knowledge  of the Company or any Seller,
threatened  against  the  Company  or any  of its  subsidiaries  that  would  be
reasonably  likely  to have a  Material  Adverse  Effect,  and there is no basis
therefor,  and neither the Company nor any of its subsidiaries is subject to any
outstanding order, writ, injunction or decree that would be reasonably likely to
have a  Material  Adverse  Effect or that  restricts  the  Company or any of its
subsidiaries in any material respect.

     Section 2.9. No Default. There exists no default or violation (and no event
has  occurred  which with notice or lapse of time would  constitute a default or
violation or loss of material  benefits) of any term,  condition or provision of
(i) any note, bond, mortgage,  indenture,  contract, agreement, permit, license,
lease,  purchase  order,  sales  order,   arrangement  or  other  commitment  or
obligation  to which the Company or any  subsidiary is a party or may be subject
or (ii) any order, writ, injunction, decree, statute, treaty, rule or regulation
applicable to the Company or any  subsidiary,  except for violations or defaults
which would not have a Material Adverse Effect.

     Section 2.10. Permits; Compliance with Applicable Law. (a) To the knowledge
of the  Company  or any  Seller,  the  Company  does not  require  any  permits,
licenses,  variances,  exemptions,  orders,  approvals or  authorizations of any
Governmental Entity to conduct the business of the Company and its subsidiaries,
as presently conducted,  in a lawful manner, other than those that it possesses.
All such permits have been legally obtained and maintained and are in full force
and effect.

     (b) To the  knowledge  of the  Company or any Seller,  the  business of the
Company and its  subsidiaries is being and has been conducted in compliance with
all permits, orders, writs, judgments,  injunctions, decrees and settlements and
all applicable laws, ordinances,  codes, rules,  regulations and policies of any
Governmental Entity.

     Section 2.11. Taxes and Tax Returns.

     (a) Definitions:

     "Code" means the Internal  Revenue Code of 1986, as amended.  All citations
to  provisions  of  the  Code,  or  to  the  Treasury  Regulations   promulgated
thereunder, shall include any amendments thereto and any substitute or successor
provisions thereto.

     "Taxes"  means  any  and all  federal,  state,  local  and  foreign  taxes,
assessments and other  governmental  charges,  duties,  impositions,  levies and

                                       9
<PAGE>
liabilities,  including,  without  limitation,  taxes  based upon or measured by
gross receipts,  income, profits, sales, use and occupation, and value added, ad
valorem,   transfer,   gains,  franchise,   withholding,   payroll,   recapture,
employment, excise, unemployment,  insurance, social security, business license,
occupation,  business  organization,  stamp,  environmental  and property taxes,
together with all interest, penalties and additions imposed with respect to such
amounts.  For purposes of this Agreement,  "Taxes" also includes any obligations
under any  agreements  or  arrangements  with any  person  with  respect  to the
liability for, or sharing of, Taxes (including, without limitation,  pursuant to
Treas. Reg. ss. 1.1502-6 or comparable provisions of state, local or foreign Tax
law) and including,  without limitation, any liability for Taxes as a transferee
or successor, by contract or otherwise.

     "Taxable Period" means any taxable year or any other period that is treated
as a taxable year (or other  period,  or portion  thereof,  in the case of a Tax
imposed with respect to such period or portion  thereof,  e.g., a quarter)  with
respect to which any Tax may be imposed under any applicable  statute,  rule, or
regulation.

     "Tax Reserve" shall have the meaning set forth in Section 2.11(c).

     "Tax  Return"  means  any  report,  return,  election,   notice,  estimate,
declaration,  information  statement and other forms and  documents  (including,
without  limitation,  all  schedules,  exhibits and other  attachments  thereto)
relating  to and  filed or  required  to be filed  with a  taxing  authority  in
connection with any Taxes (including, without limitation, estimated Taxes).

     (b) All Tax Returns  required to be filed by or with respect to the Company
or any of its  subsidiaries  for all Taxable Periods have been timely filed. All
such Tax Returns (i) were  prepared in the manner  required by  applicable  law,
(ii) are true,  correct  and  complete  in all  respects,  and (iii)  accurately
reflect the liability for Taxes of the Company and each of its subsidiaries. All
Taxes shown to be payable on such Tax Returns,  and all  assessments of Tax made
against the Company or any of its subsidiaries with respect to such Tax Returns,
have been paid when due. No adjustment  relating to any such Tax Return has been
proposed or threatened  formally or  informally  by any taxing  authority and no
basis exists for any such adjustment.


     (c) The Company and each of its subsidiaries have (i) timely paid or caused
to be paid all Taxes that are or were due,  whether or not shown (or required to
be shown) on a Tax Return and (ii) provided a sufficient reserve for the payment
of all Taxes not yet due and payable  (without regard to deferred Tax assets and
liabilities)  (the "Tax  Reserve") on the Financial  Statements  for the Taxable
Period ended  December 31, 1998 There are no Taxes that would be due if asserted
by a taxing authority,  except with respect to which the Company and each of its
subsidiaries are maintaining adequate reserves.

     (d) The Company and each of its  subsidiaries  have complied (and until the
Closing Date will comply) in all material  respects  with the  provisions of the
Code  relating  to the  withholding  and  payment of Taxes,  including,  without


                                       10
<PAGE>
limitation,  the withholding and reporting requirements under Code sections 1441
through  1464,  3401 through  3406,  and 6041 through  6049,  as well as similar
provisions  under any other  laws,  and have,  within the time and in the manner
prescribed  by law,  withheld  from  employee  wages and paid over to the proper
governmental authorities all amounts required.

     (e) To the knowledge of the Company or any Seller,  none of the Tax Returns
of the  Company  or any of its  subsidiaries  has  been  or is  currently  being
examined by the Internal Revenue Service (the "IRS") or relevant state, local or
foreign taxing authorities. To the knowledge of the Company or any Seller, there
are no examinations or other  administrative  or court  proceedings  relating to
Taxes in  progress or  pending,  nor has the Company or any of its  subsidiaries
received a revenue agent's or similar report asserting a Tax deficiency.

     (f) To the  knowledge of the Company or any Seller,  no material  claim has
ever been made in writing by any taxing authority with respect to the Company or
any  of its  subsidiaries  in a  jurisdiction  where  the  Company  or any  such
subsidiary  does not file Tax Returns that the Company or any such subsidiary is
or may be  subject  to  taxation  by that  jurisdiction.  There are no  security
interests  on any of the assets of the Company or any of its  subsidiaries  that
arose in connection with any failure (or alleged  failure) to pay any Taxes and,
except for liens for real and personal  property  Taxes that are not yet due and
payable,  there are no liens for any Tax upon any asset of the Company or any of
its subsidiaries.

     (g) The Company and each of its  subsidiaries  have made  available (or, in
the case of Tax Returns filed after the date hereof, will make available at such
time and place as  Purchaser  may  request) to  Purchaser  complete and accurate
copies of such Tax Returns, and amendments thereto,  filed by the Company and/or
its  subsidiaries  as Purchaser  may request.  Since the date of the most recent
Financial Statement, neither the Company nor any subsidiary thereof has incurred
any  liability  for Taxes that would  result in a material  decrease  in the net
worth of the Company or any such subsidiary.

     (h)  Neither the Company  nor any of its  subsidiaries  is, or has been,  a
party to any  agreement  relating  to  allocating  or sharing the payment of, or
liability for, Taxes with respect to any Taxable Period.

     (i) Neither the Company nor any of its  subsidiaries  has  distributed  the
stock of any corporation in a transaction satisfying the requirements of Section
355 of the Code since April 16,  1997.  The stock of neither the Company nor any
of its  subsidiaries  has  been  distributed  in a  transaction  satisfying  the
requirements of Section 355 of the Code since April 16, 1997.

     (j) There is no  contract,  agreement,  plan or  arrangement  covering  any
person  that,  individually  or  collectively,  could give rise to, nor will the
consummation of the transactions contemplated hereby obligate the Company or any
of its  subsidiaries  or Purchaser to make, the payment of any amount that would
not be deductible by the Company or any of its subsidiaries by reason of Section
280G of the Code.


                                       11

<PAGE>
     (k)  Neither  the  Company nor any of its  subsidiaries  has  executed  any
outstanding  waivers or comparable  consents  regarding the  application  of the
statute of limitations with respect to any Taxes or Tax Returns. No extension of
time with respect to any date on which a Tax Return was or is to be filed by the
Company or any of its  subsidiaries is in force.  Neither the Company nor any of
its  subsidiaries  has granted a power of attorney to any person with respect to
any Taxable Period.

     (l) All options to acquire stock of the Company or any of its  subsidiaries
granted  under any  stock  option  plan of the  Company  or any such  subsidiary
qualify under  Section  162(m)(4) of the Code as an exception  from  "applicable
employer  remuneration,"  and as such,  no  deduction of the Company or any such
subsidiary  relating to such options  would be  disallowed  by reason of Section
162(m) of the Code.

     (m) The Company is the common  parent of an  affiliated  group  (within the
meaning of Code section  1504(a)) that files a consolidated  U.S. federal income
tax return and includes the  corporations  listed as  "subsidiaries"  in Section
2.2(b) of the Disclosure Schedule.

     (n) Neither the Company nor any of its  subsidiaries  owns an interest in a
partnership or could be treated as a partner in a partnership  for U.S.  federal
income tax purposes.

     (o) Neither the Company nor any of its subsidiaries has been a member of an
(i)  affiliated  group  (within the meaning of Section 1504 of the Code) or (ii)
affiliated, combined,  consolidated,  unitary, or similar group for state, local
or foreign Tax purposes, other than the group of which the Company is the common
parent.

     (p) There are no outstanding options, warrants, securities convertible into
stock, or other contractual obligations that might be treated for federal income
tax  purposes as stock or another  equity  interest in the Company or any of its
subsidiaries.

     (q)  Neither  the  Company  nor any of its  subsidiaries  has  agreed or is
required to include in income any  adjustment  under  either  Section  481(a) or
Section 482 of the Code (or an analogous  provision of state,  local, or foreign
law) by reason of a change in accounting method or otherwise.

     (r) To the  knowledge  of the Company or any Seller,  there are no proposed
reassessments of any property owned by the Company or any of its subsidiaries or
other  proposals  that could increase the amount of any Tax to which the Company
or any of its subsidiaries could be subject.

     (s) Neither the Company nor any of its subsidiaries has any deferred income
reportable  for a period ending after the Closing Date but that is  attributable
to a transaction  (e.g., an installment  sale) occurring in, or resulting from a
change of  accounting  method  for, a period  ending on or prior to the  Closing
Date.


                                       12
<PAGE>
     (t) None of the  indebtedness  of the  Company  or any of its  subsidiaries
constitutes "corporate  acquisition  indebtedness" (as defined in Section 279(b)
of the Code) or other indebtedness with respect to which any interest deductions
may be disallowed under Section 279 of the Code or otherwise.

     (u) Neither the Company nor any of its  subsidiaries has an overall foreign
loss within the meaning of Section 904 of the Code.  Neither the Company nor any
of its subsidiaries has consented to have provisions of Section 341(f)(2) of the
Code applied to it. Neither the Company nor any of its subsidiaries  has, during
the five-year period ending on the Closing Date, been a personal holding company
within the meaning of Section 541 of the Code.

     Section 2.12. Employee Benefit Plans.

     (a)  Section  2.12 of the  Company  Disclosure  Schedule  sets  forth  each
material  pension,   retirement,   profit  sharing,   medical,  dental,  health,
disability, life, death benefit, group insurance,  deferred compensation,  stock
option,  stock purchase,  restricted stock,  bonus or incentive,  severance pay,
employment or  termination,  and other employee  benefit or  compensation  plan,
trust,  arrangement,  contract,  agreement,  policy  or  commitment,  including,
without  limitation,  each "employee benefit plan" as defined in Section 3(3) of
the  Employee  Retirement  Income  Security  Act of 1974,  as amended  ("ERISA")
whether  formal or  informal,  written or oral under which (i) current or former
employees,  directors or  independent  contractors  of the Company or any of its
subsidiaries  participate  or are  entitled  to  participate  by reason of their
relationship  with the  Company  or any of its  subsidiaries,  (ii) to which the
Company or any of its  subsidiaries  is a party or a sponsor thereof or by which
the Company or any of its  subsidiaries is currently bound or (iii) with respect
to which the  Company  or any of its  subsidiaries  has any  obligation  to make
payments or contributions, (the "Benefit Plans").

     (b) Each Benefit Plan has at all times been  operated and  administered  in
compliance in all material respects with its terms, the applicable  requirements
of ERISA and the Code and all other  applicable  laws,  ach Benefit Plan that is
intended to be tax  qualified  under  Section  401(a) of the Code has received a
favorable  determination letter from the IRS stating that it is so qualified and
that any trust  associated  with such Benefit  Plan is tax exempt under  Section
501(a) of the Code, and, to the knowledge of the Company or any Seller, there is
no reason why the  qualified  status of any such  Benefit Plan or trust would be
denied or revoked, whether retroactively or prospectively.

     (c)  No  pending  or,  to  the  knowledge  of the  Company  or any  Seller,
threatened disputes,  lawsuits, claims (other than routine claims for benefits),
investigations,  audits or  complaints  to, or by,  any  person or  governmental
entity have been filed or are pending with  respect to the Benefit  Plans or the
Company or any of its  Subsidiaries  in connection  with any Benefit Plan or the
fiduciaries or administrators  thereof (other than routine claims for benefits).
With  respect to each Benefit  Plan,  there has not  occurred,  and no person or
entity  is  contractually  bound  to  enter  into,  any  nonexempt   "prohibited


                                       13
<PAGE>
transaction"  within the  meaning of Section  4975 of the Code or Section 406 of
ERISA,  nor any  transaction  that would result in a civil penalty being imposed
under  Section  409 or  502(i) of  ERISA,  except  as would not have a  Material
Adverse Effect.

     (d)  Neither  the  Company,  its  Subsidiaries,  nor any trade or  business
(whether or not  incorporated)  which,  together  with the Company or any of its
Subsidiaries, would be deemed a "single employer" under Section 4001(b) of ERISA
(an  "ERISA  Affiliate")  has or at any time  within the  applicable  statute of
limitations  period has had (i) any  liability,  contingent or otherwise,  under
Title IV of ERISA or Section 412 of the Code,  (ii) an  obligation to contribute
to any "multiemployer plan" (as defined in Section 3(37) of ERISA).

     (e) All material contributions or payments made or deemed to have been made
with  respect  to each  Benefit  Plan  that  is a  deferred  compensation  plan,
including any pension  plan,  are  presently,  and have been during the years to
which they relate,  fully deductible pursuant to Section 404 of the Code and are
not  presently,  and have  never been  during  the years to which  they  relate,
subject to any material  excise tax under Section 4972 of the Code. All material
contributions  to and payments  with respect to or under the Benefit  Plans that
are required to be made with respect to periods  ending on or before the Closing
Date have been made or accrued  before the  Closing  Date by the  Company in all
material  respects in accordance with the appropriate plan documents,  financial
statement,  actuarial  report,  collective  bargaining  agreements  or insurance
contracts or arrangements.

     (f) No  Benefit  Plan that is an  "employee  welfare  benefit  plan"  under
Section 3(1) of ERISA (a "Welfare  Plan") is partially or fully funded through a
trust.  No Welfare  Plan  providing  medical or death  benefits  (whether or not
insured)  with respect to current or former  employees of the Company  continues
such coverage or provides such benefits beyond their date of retirement or other
termination  of service  (other than coverage  mandated by Section 601 of ERISA,
the  cost  of  which  is  fully  paid  by  the  former  employee  or  his or her
dependents).

     (g) With respect to each Benefit  Plan,  the Company has made  available to
Purchaser complete and correct copies of the following documents,  to the extent
in each case that such documents  exist or are required by law: (1) current plan
documents,  subsequent  plan  amendments,  or any and all other  documents  that
establish or describe the existence of the plan, trust,  arrangement,  contract,
policy or commitment;  (2) the most recent tax qualified  determination letters,
if any,  received from or  applications  pending with the IRS; and (3) the three
most recent Form 5500 Annual Reports,  including  related  schedules and audited
and  financial   statements  and  opinions  of  independent   certified   public
accountants.

     (h) The execution of, and performance of the transactions  contemplated in,
this  Agreement  will not (either alone or upon the occurrence of any additional
or subsequent events) constitute an event under any plan, policy, arrangement or

                                       14
<PAGE>
agreement  or any trust or loan that will or would  reasonably  be  expected  to
result  in any  material  payment  (whether  of  severance  pay  or  otherwise),
acceleration   of,   forgiveness  of  indebtedness   owing  from,   vesting  of,
distribution of, or increase in or obligation to fund, any benefits with respect
to any current or former employee, director or consultant of the Company.

     Section  2.13.  Intellectual  Property.  Set forth in  Section  2.13 of the
Company  Disclosure  Schedule  is a  list  (the  "Listed  Intellectual  Property
Rights") of certain U.S.  and foreign,  registered  and  unregistered,  patents,
patent   applications,    trademarks,   trade   names,   copyrights,   copyright
registrations,   technology  (including  software),   trade  secrets,  know-how,
inventions,   data,   processes   and   other   intellectual   property   rights
(collectively,  "Intellectual  Property Rights") used by the Company.  No claims
are  pending  or, to the  Company's  or S. Leslie  Misrock's  actual  knowledge,
threatened,  by any person as to the use of any Intellectual  Property Rights or
infringement  of the rights of others by the Company or any  subsidiary  and, to
the actual  knowledge  of the Company or any Seller,  the use by the Company and
its  subsidiaries  of all  Intellectual  Property  Rights and the conduct of the
Company's business does not infringe on the rights of any person and there is no
basis for any such claim.  To the actual  knowledge  of the Company or S. Leslie
Misrock,  no third  person is  infringing  on the Listed  Intellectual  Property
Rights. The Company and its subsidiaries have not taken any action to impair any
Listed  Intellectual  Property  Rights,  including  by  granting  any  licenses,
sublicenses,  liens  or  encumbrances.  The  Company  has not  entered  into any
agreement to indemnify any other person  against any charge of  infringement  of
any third party intellectual property right. All employees,  agents, consultants
or  contractors  who have  contributed  to or  participated  in the  creation or
development of any  Intellectual  Property Rights on behalf of the Company,  its
subsidiaries or any predecessor in interest thereto either:  (i) is a party to a
"work-for-hire"  agreement  under  which the Company  and its  subsidiaries  are
deemed to be the original  owner/author  of all property  rights therein or (ii)
has executed an assignment or any agreement to assign in favor of the Company or
its subsidiaries (or such predecessor in interest,  as applicable) of all right,
title and interest in such material. Listed Intellectual Property Rights include
the NWB License, the NWB/NWC License and the Velos License.

     Section 2.14.  Transactions with Affiliates.  No present or former officer,
director,  stockholder or other affiliate of the Company has (i) any interest in
the  assets,  properties  or rights  used in the  business of the Company or its
subsidiaries  (other than  solely  through the  ownership  of Shares),  (ii) any
contract,  arrangement,  agreement  or  understanding  with the  Company  or its
subsidiaries  (iii)  engaged  in any  transactions  with the  Company  since the
Balance Sheet Date.

     Section 2.15. Contracts.

     (i)  Section  2.15 of the  Disclosure  Schedule  sets forth a complete  and
accurate list of each of the contracts to which the Company or any subsidiary is
a party or is bound.


                                       15
<PAGE>
     (b)  Each  such  contract  or  agreement  is  legal,  valid,   binding  and
enforceable against the Company or its subsidiaries, and to the knowledge of the
Company or any Seller,  against each other party  thereto,  is in full force and
effect and will continue to be so legal, valid, binding, enforceable and in full
force and effect  following the Closing.  Neither the Company or the  applicable
subsidiary,  nor to the knowledge of the Company or any Seller, any other party,
is in breach or default,  and no event has occurred which would constitute (with
or without notice or lapse of time or both) a breach or default (or give rise to
any  right  of  termination,  modification,  cancellation  or  acceleration)  or
modification of benefits under any such contract.

     (c) The Company has delivered or made available for review by the Purchaser
true and complete  copies of each such contract or agreement.  Since the Balance
Sheet Date,  there has been no material  modification,  breach or termination of
any such contract or agreement.

     Section  2.16.  Labor  Relations.  (a) There is no unfair  labor  practice,
charge or complaint or other proceeding pending or, to the best knowledge of the
Company or any Seller, threatened,  against the Company or any subsidiary before
the National Labor Relations Board or any other Governmental Entity.

     (b) There is no labor strike,  slowdown or stoppage pending or, to the best
knowledge of the Company or any Seller,  threatened,  against or  affecting  the
Company or any subsidiary,  nor has there been any such activity within the past
two years.

     (c) There are no pending collective bargaining negotiations relating to the
employees of the Company or any subsidiary.

     (d) (i) there are no agreements with, or pending  petitions for recognition
of, a labor union or  association as the exclusive  bargaining  agent for any or
all of the employees of the Company or any  subsidiary,  (ii) no such  petitions
have been pending  within the past five years and (iii) to the best knowledge of
the  Company  or any  Seller,  there has not been any  general  solicitation  of
representation  cards by any union  seeking to  represent  the  employees of the
Company or any subsidiary as their exclusive bargaining agent at any time within
the past five years.

     Section  2.17.  Environmental.  (a)  Except to the  extent  that any of the
following  would not be reasonably  likely to have a Material  Adverse Effect on
the  Company:  (i) the Company and its  subsidiaries  comply  (which  compliance
includes, without limitation, the possession by the Company and its subsidiaries
of all permits and other  government  authorizations  required under  applicable
Environmental Laws, and compliance with the terms and conditions thereof) and at
all times have  complied  with all  applicable  Environmental  Laws (as  defined
below),  (ii) no Hazardous  Substances  (as defined below) are present at any of
the  properties  currently  owned,  leased,  operated or  otherwise  used by the
Company or its  subsidiaries  (including  soils,  ground water,  surface  water,
buildings or other structures), (iii) no Hazardous Substances have been disposed
on or released or discharged from, onto or under any of the properties currently

                                       16
<PAGE>
owned,  leased,  operated or otherwise  used by the Company or its  subsidiaries
(including soils,  ground water,  surface water,  buildings or other structures)
during the period of  ownership,  lease,  operation or use by the Company or any
subsidiary  or, to the actual  knowledge  of the Company or any  Seller,  at any
other time, (iv) none of the Company or its subsidiaries disposed of or released
or discharged Hazardous Substances from, onto or under or adjacent to any of the
properties  (including soils,  ground water,  surface water,  buildings or other
structures) formerly owned, leased, operated or otherwise used by the Company or
any subsidiary,  and to the actual  knowledge of the Company and any Seller,  no
Hazardous Substances were present at or disposed on or released or discharged by
any  other  person  or  entity  from,  onto or under or  adjacent  to any of the
properties  (including soils,  ground water,  surface water,  buildings or other
structures) formerly owned, leased, operated or otherwise used by the Company or
any subsidiary  during the period of ownership,  lease,  operation or use by the
Company  or any  subsidiary,  (v) none of the  Company or its  subsidiaries  are
subject to any liability or obligation in connection  with Hazardous  Substances
present at any location owned,  leased,  operated or otherwise used by any third
party,  (vi) none of the Company or its subsidiaries or, to the actual knowledge
of the Company or any Seller,  any person or entity  whose  liability  under any
Environmental  Law the  Company  has or may  have  retained  or  assumed  either
contractually or by operation of law, has received any notice,  demand,  letter,
claim  or  request  for  information  alleging  that  any  of the  Company,  its
subsidiaries  or, to the actual  knowledge  of the  Company or any  Seller,  any
person or entity whose liability under any  Environmental Law the Company has or
may have retained or assumed either  contractually or by operation of law, is or
may be in violation of or liable under any Environmental  Law, (vii) none of the
Company or its subsidiaries is subject to any order, decree, injunction or other
directive  of  any  governmental  authority  and  none  of  the  Company  or its
subsidiaries  is subject to any indemnity or other  agreement with any person or
entity relating to Hazardous Substances and (viii) there are no circumstances or
conditions  involving  any of  Company  and its  subsidiaries  or, to the actual
knowledge of the Company or any Seller,  any assets (including real property) or
businesses  previously owned,  leased,  operated or otherwise used by Company or
any  subsidiary  or any assets  (including  real  property) or businesses of any
predecessors of the Company or any subsidiary that would  reasonably be expected
to result in any  damages to the  Company  or any  subsidiary  arising  under or
pursuant to  Environmental  Law or in any  restriction on the ownership,  use or
transfer of any of the assets of the Company or its  subsidiaries  arising under
or pursuant to any Environmental Law.

                                       17
<PAGE>
     (b) As used herein, the term  "Environmental  Law" means any international,
national,  provincial,   regional,  federal,  state,  municipal  or  local  law,
regulation, order, judgement, decree, permit, authorization,  opinion, common or
decisional  law  (including,  without  limitation,  principles of negligence and
strict   liability)   or  agency   requirement   relating  to  the   protection,
investigation or restoration of the environment (including,  without limitation,
natural  resources) or the health or safety of human or other living  organisms,
including,  without  limitation,  the manufacture,  introduction  into commerce,
export, import, handling, use, presence, disposal, release or threatened release
of any  Hazardous  Substance  or  noise  pollution,  odor  pollution,  wetlands,
pollution, or contamination.

     (c) As used  herein,  the term  "Hazardous  Substance"  means any  element,
compound,  substance or other material  (including  any pollutant,  contaminant,
hazardous waste,  hazardous substance,  chemical substance,  or product) that is
listed,  classified or regulated pursuant to any Environmental  Law,  including,
without  limitation,  any petroleum product,  by-product or additive,  asbestos,
presumed  asbestos-containing  material,  asbestos-containing  material, medical
waste,    biological   waste,    chloroflourocarbon,    hydrochloroflourocarbon,
lead-containing  paint  or  plumbing,   polychlorinated  biphenyls,  radioactive
material or radon.

     Section 2.18. Ownership of Assets. The assets, properties and rights of the
Company and its subsidiaries  are held by the Company or its  subsidiaries  free
and clear of any liens,  claims or  encumbrances,  other than  Permitted  Liens.
"Permitted  Liens" means (i) liens for current  taxes not yet due and payable or
(ii) mechanics', carriers', workers' and other similar liens arising or incurred
in the ordinary course of business, which, individually or in the aggregate, are
not  substantial  in  amount,  do not  materially  detract  from the value of or
materially  interfere with the present use of any of the assets subject  thereto
or  materially  impair  the  conduct  of the  business  of the  Company  and its
subsidiaries.

     Section  2.19.  Insurance.  The  insurance  policies of the Company and its
subsidiaries are current, are in full force and effect, all premiums due thereon
have been paid,  and the  Company  and its  subsidiaries  have  complied  in all
material  respects with the provisions of such  policies,  and all such policies
either  specifically  include the Company as a named insured or include  omnibus
named insured  language which generally  includes the Company.  No proceeding is
pending or, to the best knowledge of the Company or any Seller,  threatened,  to
revoke,  cancel or limit such policies and no notice of  cancellation  of any of
such  policies has been received by the Company or any  subsidiary.  Each of the
Company and its  subsidiaries is in compliance with all warranties  contained in
all insurance policies.

     Section 2.20. Real Property.  Each of the Company and its subsidiaries have
good and  marketable  title to, or a valid  leasehold  interest in, all of their
real  properties,  and,  other than the  properties in which they hold leasehold
interests,  own  such  properties  free  and  clear  of all  liens,  claims  and
encumbrances,  other than Permitted  Liens. All real property owned or leased by
the  Company  or any  subsidiary  is set forth on  Section  2.20 of the  Company

                                       18
<PAGE>
Disclosure Schedule. The Company and its subsidiaries are in compliance with the
terms of all  leases to which  they are a party and all such  leases are in full
force and effect.

     Section 2.21.  Share  Ownership.  Such Seller owns the number of Shares set
forth  opposite  such  Seller's  name on Exhibit A, free and clear of all liens,
claims and  encumbrances,  including any restrictions on or sharing of rights to
vote or dispose of such shares. Such Shares are the only equity interests in the
Company or any  subsidiary  beneficially  owned by such Seller.  No other person
beneficially  owns any equity  interest in the Company or any  subsidiary of the
Company or has any right to acquire or vote any such equity interest.

     Section 2.22. Investment. Such Seller is acquiring the Purchaser Shares for
investment and not with a view toward,  or for sale in connection with, any sale
or distribution  thereof.  Such Seller agrees that neither the Purchaser  Shares
nor  any  interest  therein  may  be  offered,   sold,   transferred,   pledged,
hypothecated  or  otherwise  disposed  of except  pursuant  to (i) an  effective
registration  statement  under  the  Securities  Act  and any  applicable  state
securities laws or (ii) an exemption from the  registration  requirements of the
Securities Act and any applicable  state  securities  laws, such exemption to be
evidenced  by  such  documentation  as the  Purchaser  may  reasonably  request,
including an opinion of counsel  (which  counsel and opinion shall be reasonably
satisfactory  to the  Purchaser)  that such  transfer is not in violation of the
Securities Act and any applicable  state laws. The Sellers  understand  that the
certificates  to be issued to the  Sellers  hereunder  will be  subject  to stop
transfer instructions and bear a legend substantially as follows:

     "The security  represented by this  certificate was issued in a transaction
which was not registered under the Securities Act of 1933 or the securities laws
of any state and neither the security  nor any interest  therein may be offered,
sold,  transferred,  pledged,  hypothecated  or  otherwise  disposed  of  except
pursuant to (i) an effective registration statement under the Securities Act and
any applicable  state securities laws or (ii) an exemption from the registration
requirements  of the Securities Act and any applicable  state  securities  laws,
such  exemption  to be  evidenced  by  such  documentation  as  the  issuer  may
reasonably  request,  including an opinion of counsel (which counsel and opinion
shall be  reasonably  satisfactory  to the issuer) that such  transfer is not in
violation of the Securities Act and any applicable state laws."

     Section 2.23. Accredited Investor.  Such Seller is an "accredited investor"
within the meaning of Rule 501 under the  Securities  Act,  provided that in the
case  of the  Seller  identified  in  Section  2.23  of the  Company  Disclosure
Schedule,  such  Seller has such  knowledge  and  experience  in  financial  and
business  matters that he is capable of  evaluating  the merits and risks of the
transactions  contemplated hereby,  including an investment in Purchaser Shares.
Such Seller has been given an adequate  opportunity to investigate the Purchaser
and has been  given  access to all  information  he deems  appropriate.  Without
limiting the  generality of the  foregoing,  such Seller  acknowledges  that the
Purchaser  has  furnished  (or made  available  to) such Seller the  Purchaser's

                                       19
<PAGE>

Annual Report on Form 10-K for the year ended  December 31, 1998 and all filings
under  the  Exchange  Act or  the  Securities  Act  since  such  date,  a  brief
description of the Purchaser  Shares,  any material  changes in the  Purchaser's
affairs not disclosed in such documents and adequate  information  regarding the
Purchaser and the transactions  contemplated  hereby,  in each case a reasonable
time prior to the date hereof.

     Section 2.24. No Misleading Statements.  The representations and warranties
made by the Sellers in or pursuant to this  Agreement  do not include any untrue
statement of a material fact or omit to state any material fact.

     Section  2.25.  No  Exclusive  Manufacturing  Rights.  The  Company has not
granted  exclusive  manufacturing  rights to any person or entity with regard to
any immunotherapy technologies, except for the NWC License.


                                  ARTICLE III
                 REPRESENTATIONS AND WARRANTIES OF THE PURCHASER

     The Purchaser  represents  and warrants as of the date hereof and as of the
Closing  Date to the Sellers as follows,  except as set forth in the  disclosure
schedule being delivered by the Purchaser to the Sellers  concurrently  herewith
(the "Purchaser Disclosure Schedule"):

     Section 3.1. Organization.  Each of the Purchaser and its subsidiaries is a
corporation duly organized, validly existing and in good standing under the laws
of the jurisdiction of its  organization  and has all requisite  corporate power
and authority and all necessary governmental approvals to own, lease and operate
its properties and to carry on its business as now being conducted, except where
the failure to be so  organized,  existing and in good  standing or to have such
power,  authority,  and governmental approvals would not have a Material Adverse
Effect on the  Purchaser.  The  Purchaser and each of its  subsidiaries  is duly
qualified or licensed to do business and in good  standing in each  jurisdiction
in which the  property  owned,  leased or  operated  by it or the  nature of the
business conducted by it makes such qualification or licensing necessary, except
where the failure to be so duly qualified or licensed and in good standing would
not in the aggregate have a Material Adverse Effect on the Purchaser.

     Section  3.2.  Capitalization.  (a) The  authorized  capital  stock  of the
Purchaser  consists  of  89,600,000  Purchaser  Shares and  5,400,000  preferred
shares.  As of May  31,  1999,  65,122,000  Purchaser  Shares  were  issued  and
outstanding  and an  aggregate  of 8,128,464  Shares were  issuable  pursuant to
outstanding  options,  warrants or convertible notes. All the outstanding shares
of the Purchaser's  capital stock are, and all the Purchaser Shares which may be
issued  pursuant to the exercise of  outstanding  options to purchase  Purchaser
Shares will be, when issued in accordance  with the  respective  terms  thereof,
duly authorized,  validly issued,  fully paid and non-assessable.  Except as set
forth above and in the  Purchaser's  filings  with the  Securities  and Exchange
Commission pursuant to the Securities Exchange Act of 1934 (the "Exchange Act"),

                                       20
<PAGE>
(i) there are no shares of capital stock of the Purchaser authorized,  issued or
outstanding and (ii) there are no options,  warrants, calls, pre-emptive rights,
subscriptions  or other rights,  agreements,  arrangements or commitments of any
character,  relating to the issued or unissued capital stock of the Purchaser or
any of its subsidiaries,  obligating the Purchaser or any of its subsidiaries to
issue, transfer or sell or cause to be issued, transferred or sold any shares of
capital  stock of, or other  equity  interest  in, the  Purchaser  or any of its
subsidiaries or securities  convertible  into or exchangeable for such shares or
equity  interests,  or obligating  the Purchaser or any of its  subsidiaries  to
grant,  extend or enter into any such option,  warrant,  call,  subscription  or
other  right,  agreement,  arrangement  or  commitment  and  (iii)  there are no
outstanding  obligations of the Purchaser or any of its  subsidiaries to vote or
to  repurchase,  redeem or otherwise  acquire any shares of capital stock of the
Purchaser,  or any  subsidiary or affiliate of the Purchaser or to provide funds
to  make  any  investment  (in  the  form of a  loan,  capital  contribution  or
otherwise)  in any  subsidiary  or any other  entity.  Other than the  Purchaser
Shares, no securities of the Purchaser have the right to vote. The Purchaser has
delivered to the Company true and complete copies of all  instruments  governing
or defining rights under the Purchaser Shares.

     (b) The Purchaser  Shares to be issued  pursuant to Section 1.3 hereof have
been duly  authorized  and, upon  issuance in accordance  with the terms hereof,
shall be validly issued, fully paid and nonassessable.

     Section 3.3. Authority  Relative to this Agreement.  The Purchaser has full
corporate  power and  authority  to execute and deliver  this  Agreement  and to
consummate the transactions  contemplated  hereby. The execution and delivery by
the Purchaser of this Agreement,  and the consummation by it of the transactions
contemplated  hereby,  have been  duly and  validly  authorized  by its Board of
Directors  and no  other  corporate  action  on the  part  of the  Purchaser  is
necessary  to authorize  the  execution  and  delivery by the  Purchaser of this
Agreement and the  consummation by it of the transactions  contemplated  hereby.
This  Agreement  has been duly  executed and delivered by the Purchaser and is a
valid and binding obligation of the Purchaser, enforceable against the Purchaser
in accordance with its terms.

     Section 3.4. Consents and Approvals; No Violations.  Neither the execution,
delivery or performance of this Agreement by the Purchaser nor the  consummation
by the Purchaser of the transactions  contemplated  hereby nor compliance by the
Purchaser with any of the provisions  hereof will (i) conflict with or result in
any breach of any provision of the  certificate of  incorporation  or the bylaws
(or  similar  organizational  instrument)  of  the  Purchaser  or of  any of its
subsidiaries, (ii) require any filing with, or permit, authorization, consent or
approval of, any Governmental Entity or any other person or entity, (iii) result
in a violation or breach of, or constitute  (with or without due notice or lapse
of time or both) a default (or give rise to any right of termination, amendment,
cancellation  or  acceleration),  result  in the  termination  of or a right  of
termination or cancellation  of,  modification of any benefit under,  accelerate
the  performance  required by, result in the  triggering of any payment or other
material  obligation  pursuant to, result in the creation of any lien,  security
interest,  charge or  encumbrance  upon any of the  material  properties  of the
Purchaser or its subsidiaries  under, or result in being declared void, voidable

                                       21
<PAGE>
or without further binding effect any of the terms,  conditions or provisions of
any note, bond, mortgage,  indenture,  lease, license, contract, permit, deed of
trust  agreement  or other  instrument  or  commitment  obligation  to which the
Purchaser or any of its  subsidiaries  is a party or by which any of them or any
of their  properties  or assets may be bound or  affected  or (iv)  violate  any
order, writ, injunction,  decree,  statute, rule or regulation applicable to the
Purchaser,  any  of its  subsidiaries  or any of  their  properties  or  assets,
excluding  from the  foregoing  clauses  (ii),  (iii) and (iv) such  violations,
breaches or defaults which would not, in the aggregate,  have a Material Adverse
Effect on the Purchaser.

     Section 3.5. SEC Reports; Financial Statements.

     (a) The  Purchaser  has filed with the SEC all forms,  reports,  schedules,
statements and other documents  required to be filed by it since January 1, 1996
(collectively,  the "Purchaser SEC  Documents").  As of the date of filing,  the
Purchaser SEC  Documents  (a) do not contain any untrue  statement of a material
fact or omit to state a material fact required to be stated therein or necessary
in order to make the statements  therein,  in light of the  circumstances  under
which they were made, not  misleading and (b) complied in all material  respects
with the applicable  requirements of the Exchange Act and the Securities Act, as
the case may be, and the applicable rules and regulations of the SEC thereunder.

     (b) Each of the balance sheets  (including  the related notes)  included in
the  Purchaser  SEC  Documents  fairly  presents in all  material  respects  the
financial position of the Purchaser and its consolidated  subsidiaries as of the
respective  dates  thereof  and each of the  statements  of income and cash flow
(including  the related  notes)  included in the Purchaser SEC Documents  fairly
presents in all material respects the results of operations of the Purchaser and
its consolidated  subsidiaries for the respective periods then ended,  except as
otherwise noted therein. The audited consolidated balance sheet of the Purchaser
and its consolidated  subsidiaries as of December 31, 1998 is sometimes referred
to as the  "Purchaser  Balance Sheet" and such date as the "Balance Sheet Date."
Each  of the  Purchaser  financial  statements  included  in the  Purchaser  SEC
Documents has been (i) prepared in  accordance  with GAAP  consistently  applied
during the periods  involved,  except as otherwise noted therein or in the notes
thereto  and (ii)  prepared  in  accordance  with the books and  records  of the
Purchaser.

     Section 3.6. Absence of Certain Changes.  Since the Balance Sheet Date, (a)
each of the  Purchaser  and its  subsidiaries  has  operated in the ordinary and
usual course of business and (b) there have not occurred any events,  changes or
effects  which  have had or  which  could  reasonably  likely  to  have,  in the
aggregate, a Material Adverse Effect on the Purchaser.


                                       22
<PAGE>
                                   ARTICLE IV
                                    COVENANTS

     Section  4.1.  Further  Assurances.  From time to time  after the  Closing,
without  additional  consideration,  each of the  parties  hereto  will (or,  if
appropriate,  cause their  affiliates  to)  promptly  execute  and deliver  such
further  instruments  and take such  other  action as may be  necessary  to make
effective the transactions contemplated by this Agreement.

     Section 4.2. Brokers or Finders. Each party hereto represents, as to itself
and its affiliates that no agent, broker,  investment banker,  financial advisor
or other firm or person is or will be entitled to any  broker's or finder's  fee
or  any  other  commission  or  similar  fee  in  connection  with  any  of  the
transactions contemplated by this Agreement, other than Gerard Klauer Mattison &
Co., Inc. in the case of the Sellers.

     Section  4.3.  Performance  of  Obligations.  The  Sellers  shall cause the
Company to timely perform its obligations under this Agreement.

     Section 4.4. Tax Covenants.

     (a) All transfer,  documentary,  sales,  use,  registration  and other such
Taxes  (including,  without  limitation,  all applicable real estate transfer or
gains Taxes and stock transfer Taxes), any penalties,  interest and additions to
Tax and fees incurred in  connection  with this  Agreement and the  transactions
contemplated  hereby shall be paid by the Sellers.  Each party to this Agreement
shall cooperate in the timely making of all filings,  returns, reports and forms
as may be required in connection therewith.

     (b) All contracts,  agreements,  or intercompany  accounting  systems under
which the Company or any of its  subsidiaries may at any time have an obligation
to share the  payment of any  portion of a Tax (or any  amount  calculated  with
reference  to any  portion of a Tax)  shall be  terminated  with  respect to the
Company and each such  subsidiary  as of the Closing  Date,  and the Company and
each such subsidiary shall thereafter be released from any liability thereunder.

     (c) If any Seller  receives  any written  notice from any taxing  authority
proposing  any  adjustment  to any Tax  relating  to the  Company  or any of its
subsidiaries,  the  Seller  shall  give  prompt  written  notice  thereof to the
Purchaser and the Company,  which notice shall  describe in detail each proposed
adjustment.

     Section 4.5. Employees; Releases.

     (a) The Company has terminated all of its employees,  agents,  consultants,
independent contractors, and satisfied all of its liabilities and obligations to
such  employees,  agents,  consultants,  independent  contractors,  prior to the
Closing  including,  any liability  related to  outstanding  options to purchase
Company Shares, any severance or change in control payments or any contributions
that are or will be required to be made to any Benefit Plan in  accordance  with
the terms of such plan for the plan year in which the Closing  Date  occurs,  or
any prior plan year.

                                       23

<PAGE>
     (b) Each Seller hereby releases,  effective as of the Closing,  the Company
(and its subsidiaries, affiliates, officers, directors and other employees) from
all  liabilities  and  obligations  it  may  owe  such  Sellers,  including  any
liabilities and obligations  based on any facts or circumstances  existing on or
prior  to the  Closing.  Each  Seller  represents  that  it  has no  outstanding
indemnity  claim  against  the Company and knows of no basis for any such claim.
The Company hereby releases,  effective as of the Closing,  each Seller from all
liabilities  and  obligations it may owe the Company,  including any liabilities
and obligations based on any facts or circumstances  existing on or prior to the
Closing.  Each Seller  represents that it knows of no liability or obligation it
may owe the  Company,  other than as set forth in Section  4.5(y) of the Company
Disclosure  Schedule.  Nothing in this Section 4.5 shall  decrease or impair any
liability  any Seller may have to the  Purchaser and no Seller shall be entitled
to  indemnification  or other  payment from the Company in respect of any matter
for which the Purchaser may be entitled to indemnification hereunder.

     (c)  The  Company  has  provided  any  required  notice  under  the  Worker
Adjustment and Retraining Notification Act, as amended (the "WARN Act"), and any
similar state statute, and to otherwise comply with any such statute with repect
to any "plant closing" or "mass layoff" (as defined in the WARN Act), or similar
event  affecting  employees  of the  Company  and  occurring  on or prior to the
Closing Date.  The Sellers shall  indemnify and hold harmless the Purchaser with
respect to any liability  under the WARN Act or similar statute arising from the
actions of the Company on or prior to the Closing Date.

     Section 4.6. NWB Board. The Sellers shall use their reasonable best efforts
to cause H. Joseph Reiser, PhD. to be appointed to the Board of Directors of NWB
as promptly as practicable.

     Section 4.7.  Lockup.  No Purchaser  Shares or any interest  therein may be
offered, sold,  transferred,  pledged,  hypothecated or otherwise disposed of by
(a)  Messrs.  Misrock  and Fox  prior to one  year  from  the  Closing  Date and
thereafter only pursuant to the Purchaser's policy regarding trading by officers
and directors or (b) any other Seller prior to one year from the Closing Date.

                                   ARTICLE V
                            SURVIVAL; INDEMNIFICATION

     Section 5.1. Survival Periods.  (a) All  representations  and warranties of
the  parties  contained  in  this  Agreement,  the  Disclosure  Schedule  or any
certificate  delivered in  connection  herewith  shall  survive  until the first
anniversary  of the Closing Date,  and, if notice of a claim is provided by such
date,  shall  survive until the final  resolution  thereof,  provided,  that the
representations and warranties  contained in Section 2.21 [share ownership] (the
"Listed  Representations")  shall survive the Closing  without  limitation,  and
provided further,  that the representations and warranties  contained in Section
2.11 shall survive until 90 days after the expiration of the applicable  statute
of  limitations  for the  assessment  of Taxes,  including all  extensions.  All

                                       24
<PAGE>
covenants and agreements  hereunder shall survive without limit (unless by their
terms they are to survive for a shorter period).

     (b)  For  purposes  of  this  Agreement,  a  party's   representations  and
warranties shall be deemed to include such party's  Disclosure  Schedule and all
other  documents  or  certificates  delivered  by or on behalf of such  party in
connection with this Agreement.  None of the Closing,  any party's waiver of any
condition to Closing or any party's knowledge of any breach prior to the Closing
shall constitute a waiver of any rights such party may have hereunder.

     Section  5.2.  Indemnification.  Subject  to the other  provisions  of this
Article V, from and after the Closing:

     (a) The Sellers  shall  indemnify  and hold  harmless  the  Purchaser,  its
affiliates  and  the  Purchaser's  and  its  affiliates   employees,   officers,
directors,  agents  and  other  representatives  from and  against  any costs or
expenses  (including  reasonable  attorneys',  experts' and consultants'  fees),
judgments,   fines,   penalties,   losses,   claims,   liabilities  and  damages
(collectively,  "Damages") that are the result of, arise out of or relate to (i)
any breach of any  representation or warranty or failure to perform any covenant
made by or on behalf of the Company or the Sellers under this Agreement and (ii)
any liability or obligation  that is the result of, arises out of or relates to,
any fact or  circumstance  existing at or prior to the Closing Date,  other than
liabilities or obligations  disclosed to the Purchaser prior to the date hereof.
To the extent any Seller  makes a  representation,  warranty  or  covenant as to
himself,  such indemnity  obligation will be allocated to such Seller. All other
indemnity  obligations  shall  be  allocated  among  the  Sellers  pro  rata  in
accordance  with their receipt of Purchaser  shares as set forth on the attached
Exhibit A. In the absence of manifest error, any  determination by the Purchaser
as to such allocations shall be final and binding.

     (b) The  Purchaser  shall  indemnify and hold harmless the Sellers from and
against any Damages that are the result of, arise out of or relate to any breach
of any representation or warranty or the failure to perform any covenant made by
or on behalf of the Purchaser under this Agreement.

     (c) The persons to whom  indemnification is provided hereunder are referred
to herein as the "Indemnified Parties" and the persons providing indemnification
are referred to as the "Indemnifying Parties."

     Section 5.3.  Indemnification Amounts. (a) Notwithstanding any provision to
the contrary contained in this Agreement,  the Sellers shall not be obligated to
indemnify  the  Purchaser  for Damages  pursuant to this Article V to the extent
they are the result of any breach of any  representation  or warranty made by or
on behalf of the Company or the Sellers  (other than Damages  resulting from the
breach  of any of the  Listed  Representations,  as to which  there  shall be no
limitation) unless and until the dollar amount of all Damages shall equal in the
aggregate  $5,000,  in which case the Sellers will be obligated to indemnify the

                                       25
<PAGE>
Purchaser  for the total  amount of Damages  including  any amounts  which would
otherwise  not be  required  to be  paid  by  reason  of  this  Section  5.3(a).
Notwithstanding  any provision to the contrary contained in this Agreement,  the
Sellers' indemnity  obligations  hereunder shall be limited to the return of the
Purchaser Shares received by such Sellers,  valued at the prices contemplated by
Article I hereof (on a  first-in-first-out  basis). For purposes of this Article
V, all materiality,  Material Adverse Effect and similar  qualifications  in any
representation, warranty, covenant or other provision hereof shall be ignored.

     (b)  Notwithstanding  any  provision  to the  contrary  contained  in  this
Agreement, the Purchaser shall not be obligated to indemnify the Sellers for any
Damages  pursuant  to this  Article V to the  extent  they are the result of any
breach of any  representation or warranty made by or on behalf of the Purchaser,
unless  and  until the  dollar  amount of all such  Damages  shall  equal in the
aggregate $5,000, in which case the Purchaser will be obligated to indemnify the
Sellers  for the total  amount of Damages  including  any  amounts  which  would
otherwise  not be  required  to be  paid  by  reason  of  this  Section  5.3(b).
Notwithstanding  any provision to the contrary contained in this Agreement,  the
Purchaser  shall not be obligated to indemnify the Sellers for Damages  pursuant
to this Article V in an amount exceeding the consideration paid or to be paid by
the Purchaser pursuant to Article I hereof, valued at the prices contemplated by
Article I hereof (on a first-in-first-out basis).

     Section  5.4.  Claims.   (a)  If  an  Indemnified  Party  intends  to  seek
indemnification  pursuant  to this  Article  V,  such  Indemnified  Party  shall
promptly notify the Indemnifying Party in writing of such claim. The Indemnified
Party will provide the Indemnifying  Party with prompt notice of any third party
claim in respect of which  indemnification  is  sought.  The  failure to provide
either such notice will not affect any rights hereunder except to the extent the
Indemnifying Party is materially prejudiced thereby.

     (b) If such claim involves a claim by a third party against the Indemnified
Party, the Indemnifying  Party may, within ten days after receipt of such notice
and upon notice to the  Indemnified  Party,  assume,  through counsel of its own
choosing and at its own expense,  the  settlement  or defense  thereof,  and the
Indemnified  Party shall  cooperate with it in connection  therewith,  provided,
that the Indemnified Party may participate in such settlement or defense through
counsel  chosen by it.  If the  Indemnified  Party  reasonably  determines  that
representation  by the  Indemnifying  Party's  counsel of both the  Indemnifying
Party and the  Indemnified  Party may present  such  counsel  with a conflict of
interest, then the Indemnifying Party shall pay the reasonable fees and expenses
of the Indemnified Party's counsel. Notwithstanding anything in this Section 5.4
to the  contrary,  the  Indemnifying  Party may not,  without the consent of the
Indemnified  Party,  settle or compromise  any action or consent to the entry of
any  judgment,  such  consent not to be  unreasonably  withheld.  So long as the
Indemnifying  Party is contesting any such claim in good faith,  the Indemnified
Party shall not pay or settle any such claim  without the  Indemnifying  Party's
consent, such consent not to be unreasonably withheld. If the Indemnifying Party
is not contesting such claim in good faith  (including if it does not notify the
Indemnified  Party of its assumption of the defense of such claim within the ten

                                       26
<PAGE>
day period set forth above), then the Indemnified Party may conduct and control,
through  counsel of its own  choosing  and at the  expense  of the  Indemnifying
Party,  the  settlement or defense  thereof,  and the  Indemnifying  Party shall
cooperate with it in connection therewith.  The failure of the Indemnified Party
to  participate  in,  conduct or control  such  defense  shall not  relieve  the
Indemnifying Party of any obligation it may have hereunder.

     Section 5.5. Indemnification with Respect to Taxes.

     (a)  Notwithstanding  any other  provision  in this  Article V, the Sellers
shall indemnify, defend and hold harmless the Purchaser and, after the Effective
Time, the Company and each of its subsidiaries,  and their respective  officers,
directors,    employees,    affiliates,    controlling   persons,   agents   and
representatives,  and their  respective  successors  and assigns  (each,  a "Tax
Indemnitee") from and against,  and shall reimburse each Tax Indemnitee for, any
and  all  Taxes  (including,   without   limitation,   reasonable   expenses  of
investigation  and reasonable  attorneys' and accountants'  fees and expenses in
connection with any action, suit or proceeding) actually incurred or suffered at
any  time  by any  Tax  Indemnitee  arising  out of or  attributable  to (i) any
misrepresentation,   inaccuracy  or  breach  of  any  representation,  warranty,
covenant,  agreement  or  promise  related  to Taxes by the  Sellers  and/or the
Company  and/or any of its  subsidiaries  contained in this Agreement (or in any
certificate,  document,  list or  schedule  delivered  to the  Purchaser  by the
Sellers or the Company or any of its subsidiaries  hereunder),  (ii) any and all
unpaid Taxes for any Taxable Period ending on or before the Closing Date, except
to the extent  that such Taxes are  specifically  set forth in the  reserve  for
Taxes accrued on the Financial Statements for the period ended December 31, 1998
(iii) any and all unpaid Taxes, whether determined on a separate,  consolidated,
combined,  group or unitary  basis,  including  any  penalties  and  interest in
respect  thereof,  of the  Company or any of its  subsidiaries  (A)  pursuant to
Treas. Reg.  ss.1.1502-6 or any comparable provision of state, local, or foreign
law with respect to any Taxable Period beginning before the Closing Date and (B)
pursuant to any guaranty,  indemnification,  Tax sharing,  or similar  agreement
made on or before the Closing Date relating to the sharing of liability  for, or
payment of,  Taxes or (iv) any and all Taxes,  whether  payable  before,  on, or
after the Closing Date,  arising out of or attributable  to the  cancellation of
promissory  notes  obligations  of the Company and/or any waiver of rights by an
employee or option holder of the Company.

     (b) Any Tax or other  amount for which  indemnification  is provided  under
this  Agreement  shall be (i)  increased  to take  account of any Tax  detriment
incurred by any Tax Indemnitee  arising from the receipt or accrual of indemnity
payments  hereunder  (i.e.,  grossed-up  for any Tax  incurred on such  payment,
accrual,  and/or  increase)  and (ii) reduced to take account of any Tax benefit
attributable to the items to which such payments relate.

     (c) The indemnitor and its duly  appointed  representatives  shall have the
sole right to negotiate, resolve, settle, or contest any claim for Tax made by a
taxing  authority with respect to which the indemnitor has agreed to indemnify a
Tax  Indemnitee  under this Section 5.5 and with respect to which the indemnitor
has acknowledged in writing such indemnification obligation;  provided, however,

                                       27
<PAGE>
that the  indemnitor  shall not initiate any claim,  settle any issue,  file any
amended Tax Return,  take or advocate any position or otherwise  take any action
that could adversely affect the Tax Indemnitee or any of its affiliates  without
the  written  consent  of  the  Tax  Indemnitee,  which  consent  shall  not  be
unreasonably  withheld. If the indemnitor does not assume the defense of a claim
for the Tax made by a taxing  authority with respect to which the indemnitor has
indemnified  a Tax  Indemnitee  under this Section 5.5, the Tax  Indemnitee  may
defend the same at the reasonable expense of the indemnitor in such manner as it
may deem  appropriate,  including,  but not limited to,  settling  such audit or
proceeding  with the  consent  of the  indemnitor,  which  consent  shall not be
unreasonably withheld.

     Section 5.6.  Exclusive  Remedy.  Following the Closing,  the provisions of
this Article V shall be the  exclusive  remedy for the matters  covered  hereby,
provided  that nothing  herein shall  relieve any party from any  liability  for
fraud.  Following the Closing, (i) all notices to the Sellers may be made to the
Representative,  (ii)  all  notices  from  the  Sellers  shall  be  made  by the
Representative and (iii) the Representative  shall have the power to act for the
Sellers in all matters related to this Agreement.


                                   ARTICLE VI
                                  MISCELLANEOUS

     Section 6.1. Notices. All notices and other communications  hereunder shall
be in  writing  and shall be deemed  given upon  receipt  by the  parties at the
following  addresses (or at such other address for a party as shall be specified
by like notice):

     (a) if to the Purchaser, to:

                  Cytogen Corporation
                  600 College Road East
                  CN 5308
                  Princeton, New Jersey 08540
                  Attention: Donald F. Crane, Jr.
                  Telecopier: (609) 987-1229

                  with a copy to:

                  Dewey Ballantine LLP
                  1301 Avenue of the Americas
                  New York, New York 10019
                  Attention: Frederick W. Kanner
                  Telecopier: (212) 259-6333



                                       28

<PAGE>

     (b) if to the Sellers to:

                  S. Leslie Misrock, Esq., as Representative
                  1155 Avenue of the Americas
                  New York, New York 10036


                  with a copy to:

                  Proskauer Rose LLP
                  1585 Broadway
                  New York, New York 10036-8299
                  Attention: Edward Brodsky
                  Telecopier: (212) 969-2900



     Section 6.2.  Headings.  The headings  herein are inserted for  convenience
only  and  are  not  intended  to be  part  of  or  to  affect  the  meaning  or
interpretation of this Agreement.

     Section 6.3.  Counterparts.  This  Agreement may be executed in two or more
counterparts, all of which shall be considered one and the same instrument.

     Section 6.4.  Entire  Agreement;  Assignment.  (a) This  Agreement  and the
exhibits and schedules  hereto and the documents and  certificates  delivered in
connection herewith,  and the Confidentiality  Agreement and Registration Rights
Agreement, constitute the entire agreement among the parties hereto with respect
to the subject  matter  hereof,  and  supersedes  all prior and  contemporaneous
agreements  and  understandings,  both written and oral,  among the parties with
respect to the subject matter hereof.

     (b) This Agreement  shall not be assigned by a party hereto by operation of
law or  otherwise;  provided,  that the  Purchaser  may  assign  its  rights and
obligations  hereunder to any wholly owned  subsidiary of the Purchaser,  but no
such assignment shall relieve the Purchaser of its obligations hereunder if such
assignee does not perform such obligations.

     Section 6.5.  Governing Law. This Agreement shall be governed and construed
in  accordance  with the laws of the  State of New York,  without  regard to any
applicable  conflicts  of law  principles.  The  parties  hereto  expressly  and
irrevocably  (i) consent to the exclusive  jurisdiction of the federal and state
courts  sitting in New York,  (ii) agree not to bring any action related to this
Agreement or the transactions  contemplated hereby in any other court (except to
enforce the  judgement  of such  courts),  (iii) agree not to object to venue in
such  courts or to claim  that such  forum is  inconvenient  and (iv) agree that
notice or the service of process in any proceeding  shall be properly  served or

                                       29

<PAGE>

delivered if delivered in the manner  contemplated by Section 6.1 hereof.  Final
judgement by such courts shall be  conclusive  and may be enforced in any manner
permitted by law.

     Section 6.6. Specific Performance.  The parties hereto agree that if any of
the  provisions of this  Agreement  were not performed in accordance  with their
specific terms or were otherwise  breached,  irreparable  damage would occur, no
adequate  remedy at law would exist and damages would be difficult to determine,
and that the parties  shall be entitled  to  specific  performance  of the terms
hereof, in addition to any other remedy at law or equity.

     Section 6.7.  Publicity.  Except as otherwise  required by law or the rules
and regulations of any national securities exchange, no party hereto shall issue
any press  release or otherwise  make any public  statement  with respect to the
transactions  contemplated by this Agreement without prior consultation with the
other parties hereto.

     Section 6.8. Binding Nature; No Third Party  Beneficiaries.  This Agreement
shall be binding  upon and inure  solely to the benefit of each party hereto and
their permitted successors and assigns,  and nothing in this Agreement,  express
or implied,  is intended to or shall confer upon any other person or persons any
rights, benefits or remedies of any nature whatsoever under or by reason of this
Agreement.

     Section 6.9.  Severability.  This Agreement shall be deemed severable;  the
invalidity or  unenforceability of any term or provision of this Agreement shall
not affect the validity or enforceability of this Agreement or of any other term
hereof, which shall remain in full force and effect.

     Section 6.10.  Interpretation.  As used in this Agreement,  (a) "including"
(or similar terms) shall be deemed  followed by "without  limitation"  and shall
not be deemed to be limited to matters of a similar nature to those  enumerated,
(b) "contract"  shall include any note,  bond,  mortgage,  indenture,  contract,
agreement,  permit,  license,  sublicense,  lease,  purchase order, sales order,
arrangement or other commitment,  obligation or understanding,  (c) "subsidiary"
of any person means another person,  an amount of the voting  securities,  other
voting ownership or voting partnership interests of which is sufficient to elect
at least a majority of its Board of  Directors or other  governing  body (or, if
there are no such  voting  interests,  50% or more of the  equity  interests  of
which) is owned  directly or  indirectly  by such first  person,  (d)  "ordinary
course of business" (or similar  terms) shall be deemed  followed by "consistent
with past practice" and (e) "assets" shall include  "rights,"  including  rights
under  contracts.  In  determining  whether  a fact,  event or other  item has a
Material  Adverse  Effect,  such fact,  event or other item shall be  considered
individually and in the aggregate with all other facts, events or other items.

     Section  6.11.  Payment  of  Expenses.  Whether  or  not  the  transactions
contemplated by this Agreement shall be consummated, each party hereto shall pay
its own expenses  incident to preparing for, entering into and carrying out this
Agreement.  The  Sellers  shall  be  responsible  for all of  their  own and the

                                       30
<PAGE>
Company's  expenses  in  connection  with this  Agreement  and the  transactions
contemplated  hereby  (including  the  negotiation  and  investigation  hereof),
including legal, investment banking and accounting fees and expenses.


                                       31
<PAGE>


         IN WITNESS WHEREOF,  the parties hereto have executed this Agreement as
of the date first written above.


                                              CYTOGEN CORPORATION


                                              By: /s/
                                                 ------------------------
                                                 Joseph Reiser, Ph.D.
                                                  President and CEO


                                              SELLERS:

                                              /s/
                                              ---------------------------
                                              S. Leslie Misrock


                                              /s/
                                              ---------------------------
                                              Alan Fox
                                              By: S. Leslie Misrock, as Agent


                                              /s/
                                              ---------------------------
                                              Max Link
                                              By: S. Leslie Misrock, as Agent


                                              CC CONSULTING A/S


                                              By: /s/
                                                 ------------------------
                                              S. Leslie Misrock, as Agent


                                              MISROCK HOLDINGS LP



                                              By: /s/
                                                 ------------------------
                                              S. Leslie Misrock
                                              General Partner




                                       32


                                                                    Exhibit 10.2





                       LIMITED LIABILITY COMPANY AGREEMENT

                                       OF

                          PSMA DEVELOPMENT COMPANY LLC





                               Dated June 15, 1999





<PAGE>


                                TABLE OF CONTENTS


ARTICLE I FORMATION AND NAME:  OFFICE; PURPOSE; TERM..........................1

   1.1. Organization..........................................................1
   1.2. Name of the Company...................................................1
   1.3. Principal Place of Business...........................................1
   1.4. Purpose...............................................................1
   1.5. Company Authority.....................................................2
   1.6. Term..................................................................2
   1.7. Registered Agent......................................................2
   1.8. Members and Initial Contribution......................................2
   1.9. Additional Members....................................................2

ARTICLE II CAPITALIZATION.....................................................2

   2.1. Capital Accounts......................................................2
   2.2. Capital Contributions.................................................3
   2.3. Loans.................................................................6
   2.4. Budget................................................................6

ARTICLE III PROFITS, LOSSES AND DISTRIBUTIONS.................................7

   3.1. Allocation of Profits and Losses......................................7
   3.2. Allocation-Rules......................................................9
   3.3. Tax Allocations: Section 704(c) of the Code...........................9
   3.4. Fiscal Year..........................................................10
   3.5. Partnership for Tax Purposes.........................................10
   3.6. Tax Matters..........................................................10
   3.7. Cash Flow Distributions..............................................11
   3.8. Liquidating Distributions Upon Dissolution...........................11
   3.9. Tax Distributions....................................................11
   3.10. Deficit Capital Account Restoration.................................12
   3.11. Other Distributions.................................................12

ARTICLE IV MANAGEMENT........................................................12

   4.1. Management Committee.................................................12
   4.2. Meetings of Members..................................................18
   4.3. Liability and Indemnification........................................18
   4.4. Duties, Right to Conduct Other Business..............................19
   4.5. Scientific Advisory Board............................................20
   4.6. Research Grants......................................................20

                                       i

<PAGE>

ARTICLE V OFFICERS...........................................................20

   5.1. Designation, Authority and Compensation of Officers..................20
   5.2. Tenure of Officers...................................................20

ARTICLE VI TRANSFER OF INTERESTS, WITHDRAWAL AND TERMINATION OF MEMBERS......20

   6.1. Transfer or Withdrawal Prohibited; Change of Control of a Member.....20
   6.2. Regulatory Matters...................................................22
   6.3. Default; Buyout/Liquidation Option...................................22

ARTICLE VII DISSOLUTION, LIQUIDATION AND TERMINATION OF THE COMPANY..........26

   7.1. Events of Dissolution................................................26
   7.2. Procedure for Winding Up and Dissolution.............................26
   7.3. Termination of Company...............................................26
   7.4. License Grants on Dissolution........................................26

ARTICLE VIII BOOKS, RECORDS, ACCOUNTING AND TAX ELECTIONS....................27

   8.1. Bank Accounts........................................................27
   8.2. Fiscal Year..........................................................27
   8.3. Method of Accounting.................................................27
   8.4. Books and Records....................................................27
   8.5. Tax Information......................................................27

ARTICLE IX MARKETING RIGHTS..................................................28

   9.1. Grant of North American Marketing Rights.............................28
   9.2. Diligence Obligations................................................28
   9.3. Assistance by Progenics; Contingent Grant of Rights..................28
   9.4. Marketing Agreement..................................................29
   9.5. Negotiation Rights...................................................30
   9.6. Marketing Compensation...............................................31
   9.7. Non-Transferability of Rights........................................31
   9.8. Termination of Rights................................................31
   9.9. Retention of Rights..................................................32

ARTICLE X DISPUTE RESOLUTION.................................................32

   10.1. Escalation Procedure................................................32
   10.2. Arbitration.........................................................32
   10.3. Injunctive Relief...................................................34

ARTICLE XI MISCELLANEOUS PROVISIONS..........................................34

   11.1. Assurances..........................................................34
   11.2. Disclaimer of Agency................................................34

                                       ii


<PAGE>

   11.3. Entire Agreement; Amendment.........................................34
   11.4. Notices.............................................................34
   11.5. Counterparts........................................................35
   11.6. Governing Law.......................................................35
   11.7. Binding Effect......................................................35
   11.8. Severability........................................................35
   11.9. Survival of Rights, Duties and Obligations..........................35
   11.10. Captions and Exhibits..............................................35
   11.11. Specific Performance...............................................35
   11.12. Assignability......................................................35
   11.13. Confidentiality....................................................36











                                      iii
<PAGE>



                       LIMITED LIABILITY COMPANY AGREEMENT

                                       OF

                          PSMA DEVELOPMENT COMPANY LLC

                  This Limited Liability Company Agreement (this "Agreement") is
made this 15th day of June, 1999, by and among Progenics Pharmaceuticals,  Inc.,
a  Delaware  corporation   ("Progenics"),   CYTOGEN   Corporation,   a  Delaware
corporation  ("CYTOGEN"),  and PSMA Development  Company LLC, a Delaware limited
liability company (the "Company").

                              EXPLANATORY STATEMENT

                  The parties  have  agreed to organize  and operate the Company
pursuant to the Delaware Limited Liability Company Act (the "Act") in accordance
with the terms and conditions set forth herein.

                  NOW,  THEREFORE,  for good  and  valuable  consideration,  the
parties, intending to be legally bound, agree as follows:

ARTICLE I.........
                    FORMATION AND NAME: OFFICE; PURPOSE; TERM

     1.1.  Organization.  The parties have organized the Company pursuant to the
Act and the provisions of this  Agreement  and, for that purpose,  have caused a
Certificate of Formation (the "Certificate"), in the form attached as Exhibit A,
to be executed and filed as required by the Act.

     1.2. Name of the Company. The name of the Company shall be PSMA Development
Company LLC, and all Company  business must be conducted under that name or such
other name that complies with  applicable  law as the  Management  Committee (as
hereinafter defined) may select from time to time.

     1.3. Principal Place of Business. The Company's principal place of business
shall be c/o  Progenics  Pharmaceuticals,  Inc.,  777 Old Saw Mill  River  Road,
Tarrytown,  New York  10591 or any other  place of  business  as the  Management
Committee may from time to time deem advisable.

     1.4. Purpose. The purposes of the Company are to:

     (i) acquire,  exploit,  control and distribute  all  licensing/sublicensing
rights  regarding  products in the Field, as such term is defined in Section 1.9
of the  PSMA/PSMP  License  Agreement,  dated  the  date  hereof,  by and  among
Progenics, CYTOGEN and the Company (the "PSMA/PSMP License Agreement");

<PAGE>

     (ii)  research,  develop,  manufacture  or have  manufactured,  market  and
promote or have  marketed and promoted and otherwise  commercialize  products in
the Field;

     (iii) raise capital for the foregoing;

     iv)  engage  in any and all  things  necessary,  convenient  or  incidental
thereto; and

     (v)  engage in any other  business  or  activity  lawful  under the Act and
authorized by the Management Committee.

     1.5. Company  Authority.  The Company shall have the power and authority to
take any and all actions necessary, appropriate,  convenient or incidental to or
for the  furtherance  of the purposes  set forth  herein,  including  all of the
powers of a limited liability company under the Act.

     1.6.  Term.  The term of the Company (the "Term")  shall  commence upon the
date the  Certificate  is filed as  required  by the Act and shall be  perpetual
unless terminated as provided in this Agreement.

     1.7.  Registered  Agent.  The name and address in Delaware of the Company's
registered  agent upon whom and at which  process  against  the  Company  can be
served is Corporation Service Company,  1013 Centre Road,  Wilmington,  Delaware
19805,  or such other person or such other  persons as may be  designated by the
Management Committee.

     1.8. Members and Initial Contribution.  The names, taxpayer  identification
numbers and present  mailing  addresses  of the members (the  "Members")  of the
Company  are set forth in  Schedule A attached  hereto.  The  initial  ownership
interest  in the  Company  of each of  Progenics  and  CYTOGEN,  as the  initial
Members,  shall be 50%.  Each Member's  interest in the Company (an  "Interest")
shall at all times be equal to such Member's  Percentage,  as defined in Section
2.2 hereof.  The  Interest of each Member is subject to change from time to time
as provided herein. Each of Progenics and CYTOGEN is admitted as a Member of the
Company  effective  contemporaneously  with the execution by such person of this
Agreement.

     1.9. Additional Members.  Additional persons or entities may be admitted as
Members of the Company  only upon the prior  written  consent or approval of the
Management  Committee,  which may grant or  withhold  admission  in its sole and
absolute discretion.

                                   ARTICLE II
                                 CAPITALIZATION

     2.1.  Capital  Accounts.  (a) An individual  capital  account (the "Capital
Account")  shall be maintained  for each Member in  accordance  with the capital
account  maintenance rules set forth in Treasury  Regulation Section 1.704-1(b).
Without  limiting the generality of the foregoing,  a Member's  Capital  Account
shall be increased by (a) the amount of money  contributed  by the Member to the
Company,


                                       2

<PAGE>

     (b) the fair market value of property (other than Intellectual Property (as
defined below) unless all Members shall agree to assign a value to such property
for  purposes of this  Article II  hereafter  contributed  by such Member to the
Company, net of liabilities secured by such property, and (c) allocations to the
Member of the Company's net income and gains (as  determined  for federal income
tax purposes  but on the basis of the book values of the  Company's  assets).  A
Member's  Capital  Account  shall  be  decreased  by (i)  the  amount  of  money
distributed  to the Member,  (ii) the fair market value of any  property  (other
than any Intellectual Property transferred previously by Progenics or CYTOGEN to
the Company without any value being reflected in the transferor Member's Capital
Account if such property is reconveyed to the transferor Member)  distributed to
the Member, as determined by the distributee  Member and the Company (net of any
liabilities  secured by the property)  after  adjusting  each  Member's  Capital
Account  by such  Member's  share  of the  unrealized  income,  gain,  loss  and
deduction inherent in such property and not previously reflected in such Capital
Account,  as if the property had been sold for its then fair market value on the
date of distribution,  (iii)  expenditures  described,  or treated under Section
704(b) of the Code as described,  in Section  705(a)(2)(B) of the Code, and (iv)
the Member's  share of losses and  deductions.  For purposes of this  Agreement,
"Intellectual  Property"  shall  include  inventions  (patented or  unpatented),
improvements, rights under patents and patent applications, unpublished research
and development information,  formulae,  processes,  expertise,  know-how, trade
secrets and technical data.

     (b) This Section 2.1 and the other provisions of this Agreement relating to
maintenance of Capital Accounts are intended to comply with Treasury  Regulation
Section  1.704-1(b) and shall be interpreted and applied in a manner  consistent
with such Treasury  Regulations.  In the event the  Management  Committee  shall
determine that it is prudent to modify the manner in which the Capital Accounts,
or any debits or credits  thereto,  are  computed  in order to comply  with such
Treasury  Regulations,  the  Management  Committee  may make such  modification;
provided,  however,  that it shall not have an  adverse  effect  on the  amounts
distributable to any Member.

     2.2.   Capital   Contributions.   (a)  Each   Member's   share  of  Capital
Contributions and each Member's  Percentage (each as defined  hereinafter) shall
be set forth on Schedule A, which shall be updated by the  Management  Committee
upon any changes in any Member's share of total Capital  Contributions.  As used
herein,  (i) the term "Capital  Contribution"  shall mean a contribution  to the
capital of the Company  made by a Member  pursuant to this  Agreement,  (ii) the
term  "Percentage"   shall  mean  a  Member's  share  of  the  Adjusted  Capital
Contributions  expressed  as a  percentage  of the  aggregate  Adjusted  Capital
Contributions   of  all   Members;   and  (iii)  the  term   "Adjusted   Capital
Contributions" shall mean a Member's Capital  Contributions as adjusted pursuant
to the terms of this Agreement (but excluding,  for these purposes,  in the case
of  Progenics,  the Progenics  R&D Capital  Contributions  as defined in Section
2.2(d) hereof and the Supplemental  Capital  Contributions as defined in Section
2.2(e) hereof and, in the case of CYTOGEN, any [CONFIDENTIAL  TREATMENT HAS BEEN
REQUESTED] as defined in Section 2.2(e) hereof).

                                       3

<PAGE>

     (b)  Simultaneously  herewith,  the Members are contributing to the Company
cash in the amounts set forth on Schedule A.

     (c) (i) The Management  Committee may from time to time, in connection with
preparing the Budget (as defined hereinafter) or otherwise, call for the Members
to   make   additional   capital    contributions   (the   "Additional   Capital
Contributions"),  in which event the Management  Committee  shall give notice to
each  Member of: (A) the total  amount of the  Additional  Capital  Contribution
being  called;  (B) the  reason the  Additional  Capital  Contribution  is being
called;  (C) each Member's  proportionate  share of the total Additional Capital
Contribution  (determined in accordance  with this Section  2.2(c);  and (D) the
date the Additional  Capital  Contribution is due and payable,  which date shall
not,  without the written consent of the Members,  be less than 30 nor more than
90 calendar days after the notice has been given.  A Member's share of the total
Additional  Capital  Contribution  shall  be equal to the  product  obtained  by
multiplying   the  Member's   Percentage  and  the  total   Additional   Capital
Contribution  required.  A Member's share shall be payable in cash, by certified
check or wire transfer.  No Additional Capital Contribution by any Member may be
made or required  to be made on an in-kind or any other  non-cash  basis  unless
consented to in writing by each of the Members.  Upon payment of the  Additional
Capital  Contributions,  the  Capital  Contributions  of each  Member  shall  be
adjusted.

     (ii) If a Member (the "Non-Contributing  Member") fails to pay when due all
or any portion of any Additional Capital  Contribution  called by the Management
Committee (the amount not contributed  being a "Failed  Contribution"),  and the
other Member (the "Contributing  Member") makes proper and timely payment of its
portion of the Additional Capital  Contribution,  then the following adjustments
shall be made:

     (1) the Adjusted Capital Contributions of the Non-Contributing Member shall
automatically  and  without  further act on the part of any party be adjusted by
reducing  the  amount  of  the   Non-Contributing   Member's   Adjusted  Capital
Contributions  by 10% (the  "Reduction  Amount")  of the  amount  of the  Failed
Contribution  and increasing the amount of the  Contributing  Member's  Adjusted
Capital Contributions by the Reduction Amount; and

     (2) the  Percentages of the Members shall be adjusted to stand in the ratio
of their  respective  Adjusted  Capital  Contributions,  and Schedule A shall be
amended accordingly.

     (iii) If a Non-Contributing Member fails to pay when due all or any portion
of any Additional Capital  Contribution called for by the Management  Committee,
the Management Committee shall give notice (a "Non-Contribution  Notice") within
15 days after the date such Additional  Capital  Contribution is due and payable
to the Contributing  Member,  and the Contributing  Member shall have the option
(but not the obligation) to make an Additional Capital Contribution by reason of
such  default  (a  "Default  Contribution")  to the  Company in an amount not in
excess of the Failed Contribution.  Any Default  Contribution,  if made, must be

                                       4

<PAGE>

funded within 30 calendar days after  delivery of the  Non-Contribution  Notice,
or, if the Management Committee shall fail to give the Non-Contribution  Notice,
within 45 calendar days after the date such Additional  Capital  Contribution is
due and payable.

     (iv) Except as  expressly  stated  herein,  no Member  shall be required to
contribute any additional  capital to the Company,  and no Member shall have any
personal liability for any debt,  obligations,  or liability of the Company. The
rights provided in this Section 2.2(c) shall be the exclusive remedies available
to the Company and any Contributing Member against any  Non-Contributing  Member
for such  Non-Contributing  Member's  failure  to pay  when  due any  Additional
Capital Contribution called for by the Management Committee.

     (d) Progenics shall be required to make additional Capital Contributions to
the Company of up to  [CONFIDENTIAL  TREATMENT  HAS BEEN  REQUESTED] to fund the
Company's  research and development  programs as budgeted in the work plans (the
"Work Plans") described in Section 2 of the Services Agreement,  dated as of the
date  hereof,  between  Progenics,   CYTOGEN  and  the  Company  (the  "Services
Agreement"), subject to the terms and conditions described below. The amounts so
funded are  referred to herein as the  "Progenics  R&D  Capital  Contributions."
[CONFIDENTIAL   TREATMENT  HAS  BEEN   REQUESTED]   The  Progenics  R&D  Capital
Contributions shall be provided and applied when and as needed (as determined in
the  reasonable  discretion of the  Management  Committee) to fund the Company's
research  and  development  programs  through  and  including  the filing by the
Company of an  Investigational  New Drug application with the U.S. Food and Drug
Administration  (the "FDA") with respect to a product under  development  by the
Company (an "IND  Filing").  Progenics  shall not be  obligated  to fund through
Progenics R&D Capital  Contributions,  and  Progenics R&D Capital  Contributions
shall not be applied to fund (i) any clinical development or other activities of
the  Company  with  respect  to a  product  beyond  an IND  Filing  or (ii)  any
administrative or other  non-research and development  functions,  activities or
expenses.  During the period  ending with the  discharge  in full of  Progenics'
funding obligation under this Section 2.2(d),  Progenics shall have the right to
direct the application of the Progenics R&D Capital  Contributions in accordance
with the Work Plans.  Notwithstanding the foregoing, if Progenics ceases to be a
Member in the  Company  before  Progenics  has funded to the Company all amounts
required  pursuant to this Section  2.2(d),  Progenics  shall be relieved of its
funding  obligation  with respect to such portion of the  Progenics  R&D Capital
Contributions not theretofore funded.

     (e)  [CONFIDENTIAL  TREATMENT HAS BEEN  REQUESTED]  The parties intend that
such   reduction  in  Progenics'   obligation  to  make  Progenics  R&D  Capital
Contributions shall reduce Progenics R&D Capital  Contributions  applied to fund
development  of  a  vaccine-based  product.  [CONFIDENTIAL  TREATMENT  HAS  BEEN
REQUESTED]

     (f) Progenics  shall be required to make additional  Capital  Contributions
(the  "Supplemental  Capital  Contributions")  to the  Company in the  following
amounts not later than five business days after the dates indicated:

                                       5

<PAGE>

Amount         Date
- ------         ----

$500,000       The date of this Agreement;

$500,000       On the  earlier to occur of (i) the date that is six months after
               the date of this Agreement or December 31, 1999;

$500,000       On the earlier to occur of (i) the date on which the  Management
               Committee  by written resolution identifies a lead compound for
               product development or (ii) December 31, 2000; and

$500,000       On the  earlier  to  occur  of (i)  the  date on  which  the  FDA
               approves an Investigational  New Drug application with respect to
               a Licensed Product(as defined in the PSMA/PSMP License Agreement)
               or (ii) December 31, 2001.

Notwithstanding  the foregoing,  Progenics  shall have no obligation to make any
Supplemental  Capital  Contribution if at the time any such capital contribution
is due Progenics is not a member of the Company.

     (g) No Member shall be paid interest on its Capital  Contributions.  Except
as  otherwise  provided  in this  Agreement,  no Member  shall have the right to
receive any return of or on any Capital Contribution.

     2.3. Loans. The Management Committee may, in its sole discretion, authorize
and cause the  Company to borrow  from any person  (including  a Member) on such
terms  and  subject  to  such  conditions  as  the  Management  Committee  shall
determine.  No Member  shall be  required  to lend  funds to the  Company  or to
guarantee or provide  security or any other form of credit  support with respect
to any such borrowing.

     2.4. Budget.  (a) The Management  Committee shall promptly prepare a budget
for the  Company's  activities  covering  such  time  period  as the  Management
Committee  shall  deem  appropriate.  The  Budget  may  include  provisions  for
Additional  Capital  Contributions  to  made  by  the  Members.  The  Management
Committee  shall meet to review and update the Budget on a semi-annual  basis or
as it may otherwise determine to be appropriate.

     (b) If at any time the  Management  Committee  is  unable  to agree  upon a
proposed  Budget or a proposed update to the Budget (a "Budget  Dispute"),  such
disagreement  will be  resolved  in  accordance  with  the  management  deadlock
provisions  contained in Section 4.1(f) hereof  (provided that if any portion of
the Budget is not in dispute, the provisions of such undisputed portion shall be
implemented  to the extent  practicable).  If a Budget  Dispute is  submitted to
arbitration,  and the arbitrator  determines  that a Member (the  "Uncooperative
Member") acted in bad faith in unreasonably  withholding  approval of a proposed
Budget, the Adjusted Capital  Contributions of the Uncooperative  Member and the
other Member shall  without  further act on the part of any party be adjusted by
reducing the amount of the Uncooperative Member's Adjusted Capital Contributions
by the  greater  of (A)  [CONFIDENTIAL  TREATMENT  HAS  BEEN  REQUESTED]  of the


                                       6
<PAGE>

Uncooperative  Member's pro rata share of any  Additional  Capital  Contribution
required by the  arbitrator  (if the  dispute  involved  an  Additional  Capital
Contribution)  or  (B)  [CONFIDENTIAL  TREATMENT  HAS  BEEN  REQUESTED]  of  the
Uncooperative Member's Adjusted Capital Contributions, and increasing the amount
of the other Member's Adjusted Capital Contributions by such amount.



                                  ARTICLE III
                        PROFITS, LOSSES AND DISTRIBUTIONS

     3.1. Allocation of Profits and Losses. (a) The Company's profits and losses
(as  determined  for federal income tax purposes but as adjusted under the rules
of Treasury Regulation Section  1.704-1(b)(2)(iv)) for each Fiscal Year shall be
allocated  to the Members (i) first,  in such amounts as will adjust the Capital
Account  balances  of each of the  Members to be in the same  proportion  as the
Members'  respective  Percentages  and (ii)  thereafter,  in  proportion  to the
Members respective Percentages.

     (b)  Notwithstanding  Section 3.1(a) hereof,  losses allocated  pursuant to
Section  3.1(a) to any Member for any Fiscal  Year shall not exceed the  maximum
amount of loss that may be allocated to such Member without  causing such Member
to have an Adjusted Capital Account Deficit (as defined  hereinafter) at the end
of such Fiscal Year. Any loss in excess of the limitation in this Section 3.1(b)
shall be specially  allocated  solely to the other Members to the maximum extent
permitted by this Section 3.1(b).  "Adjusted  Capital  Account  Deficit" means a
deficit Capital Account balance after that balance has been adjusted pursuant to
the penultimate  sentences of Treasury  Regulations  Sections  1.704-2(g)(1) and
1.704-2(i)(5).

     (c)   Notwithstanding   Section  3.1(a)  hereof,   the  following   special
allocations  shall be made in the following  order prior to the  application  of
Section 3.1(a) hereof:

     (i) If there is a net decrease in Company minimum gain ("Minimum Gain") (as
such  decrease  is  determined  as provided  in  Treasury  Regulations  Sections
1.704-2(d) and 1.704-2(g))  during any Fiscal Year,  certain items of income and
gain,  including gross income or gain,  shall be allocated to the Members in the
amounts and manner described in Treasury  Regulations Section  1.704-2(f).  This
Section  3.1(c)(i)  is  intended  to comply  with the  minimum  gain  chargeback
requirement  relating to  partnership  non-recourse  liabilities  (as defined in
Treasury Regulations Section 1.704-2(b) and shall be so interpreted

     (ii) If there is a net  decrease in Minimum  Gain  attributable  to partner
non-recourse  debt  (determined   pursuant  to  Treasury   Regulations   Section
1.704-2(i)) during any Fiscal Year, certain items of income and gain,  including
gross income or gain, shall be allocated as quickly as possible to those Members
which had a share of the Minimum Gain  attributable to the partner  non-recourse
debt (such  share to be  determined  pursuant to  Treasury  Regulations  Section


                                       7

<PAGE>

1.704-1(i)(5))  in the amounts  and manner  described  in  Treasury  Regulations
Sections  1.704-2(i) and (j). This Section 3.1(c)(ii) is intended to comply with
the minimum gain chargeback  requirement  relating to partner  non-recourse debt
set  forth  in  Treasury  Regulations  Section  1.704-2(i)(4))  and  shall be so
interpreted.

     (iii) Deductions attributable to obligations with respect to which a Member
bears the  economic  risk of loss  within  the  meaning of  Treasury  Regulation
Section  1.704-2(b)(4) shall be allocated to the Member or Members that bear the
economic  risk of loss for such  debt in  accordance  with the  requirements  of
Treasury  Regulation Section  1.704-2(i)(1).  "Nonrecourse  Deductions" (as such
term is defined in Treasury Regulations  Sections  1.704-2(b)(1) and 1.704-2(c))
of the  Company  shall  be  allocated  to the  Members  in  proportion  to their
Percentages.

     (iv) If one or more of the Members  unexpectedly  receives any  adjustment,
allocation or distribution  described in Treasury  Regulations  Sections 1.704-1
(b)(2)(ii)(d)(4),  (5) or (6),  then items of income and gain shall be specially
allocated to such Members in an amount and manner  sufficient  to eliminate  the
Adjusted  Capital Account Deficit  created by such  adjustments,  allocations or
distributions  as quickly as possible,  provided that an allocation  pursuant to
this Section 3.1(c)(iv) shall be made only if and to the extent that such Member
would have an  Adjusted  Capital  Account  Deficit  after all other  allocations
provided for in this Section 3.1 have been  tentatively  made as if this Section
3.1(c)(iv) were not in this Agreement.  This provision is intended to qualify as
a "qualified income offset" within the meaning of Treasury  Regulations  Section
1.704-1(b)(2)(ii)(d).

     (v) If one or more of the Members has a deficit  Capital Account at the end
of any Fiscal  Year which is in excess of the sum of (i) the amount  such Member
is obligated to contribute  pursuant to any provision of this Agreement and (ii)
the amount  such  Member is deemed to be  obligated  to restore  pursuant to the
penultimate  sentences  of  Treasury  Regulations  Sections   1.704-2(g)(1)  and
1.704-2(i)(5),  each such Member shall be specially  allocated  items of Company
income and gain in the amount of such  excess as quickly as  possible,  provided
that an allocation  pursuant to this Section 3.1(c)(v) shall be made only if and
to the extent that such Member would have a deficit Capital Account in excess of
such sum after all other allocations  provided for in this Section 3.1 have been
made as if Section  3.1(c)(iv) hereof and this Section 3.1(c)(v) were not in the
Agreement.

     (vi) The allocations set forth in Sections 3.1(b) and 3.1(c)(i)-(v)  hereof
(the "Regulatory  Allocations") are intended to comply with certain requirements
of the Treasury Regulations. It is the intent of the Members that, to the extent
possible,   all  Regulatory  Allocations  shall  be  offset  either  with  other
Regulatory  Allocations  or with special  allocations  of other items of Company
income, gain, loss or deduction pursuant to this Section 3.1(c)(vi).  Therefore,
the  Management  Committee  shall make such  offsetting  special  allocations of
Company  income,  gain,  loss and  deduction in whatever  manner they  determine
appropriate,  so that, after such offsetting allocations are made, each Member's
Capital Account balance is, to the extent possible, equal to the Capital Account
balance such Member would have if the  Regulatory  Allocations  were not part of


                                       8
<PAGE>

the Agreement and all Company items were allocated  pursuant to Section  3.1(a).
In exercising its discretion,  the Management  Committee shall take into account
future  Regulatory  Allocations  pursuant to Sections  3.1(c)(i) and (ii) hereof
that,  although not yet made, are likely to offset other Regulatory  Allocations
previously made under Section 3.1(c)(iii) hereof.

     (vii)  If the  Internal  Revenue  Service  reallocates  an item of  income,
deduction or loss to a Member or an affiliate  ("Affiliate") pursuant to Section
482 of the Code or any similar rule or  principle of law (a "Member  Section 482
Allocation"), and the Company has a corresponding correlative item of deduction,
loss or income (as determined  under Section  1.482-1(g) of the Regulations (the
"Company  Correlative  Item"),  such Company Correlative Item shall be specially
allocated to and  reflected in the Capital  Account of the Member that  received
(or  whose  Affiliate  received)  such  Member  Section  482  Allocation,  and a
corresponding  deemed contribution or distribution shall likewise be credited or
debited to the Capital Account of such Member.

     (viii) If the  Internal  Revenue  Service  reallocates  an item of  income,
deduction  or loss to the  Company  pursuant  to Section  482 of the Code or any
similar rule or principle of law (a "Company Section 482  Allocation"),  and any
Member has a  corresponding  correlative  item of deduction,  loss or income (as
determined under Section 1.482-1(g) of the Regulations (the "Member  Correlative
Item")), such Company Section 482 Allocation shall be specially allocated to and
reflected in the Capital Account of the Member that received (or whose Affiliate
received) such Member Correlative Item, and a corresponding  deemed contribution
or distribution  shall likewise be credited or debited to the Capital Account of
such Member.

     (ix) If any  Member is  required  to  contribute  an amount to the  Company
pursuant to the last  sentence of Section 3.9  hereof,  special  allocations  of
gross items of income,  gain, loss and deduction shall be made to the Members to
ensure that after such  contribution  and all liquidating  distributions  to the
Members, each of the Members' Capital Account balances will equal zero.

     3.2. Allocation-Rules.  (a) For purposes of determining the profits, losses
or any other items allocable to any period,  profits,  losses and any such other
items shall be determined on a daily,  monthly or other basis,  as determined by
the Management  Committee using any method that is permissible under Section 706
of the Code and the Treasury Regulations thereunder.

     (b) The Members are aware of the income tax consequences of the allocations
made by this Article III and hereby agree to be bound by the  provisions of this
Article III in reporting  their shares of Company income and loss for income tax
purposes.

     3.3. Tax  Allocations:  Section 704(c) of the Code. (a) In accordance  with
Section  704(c) of the Code and the  Treasury  Regulations  thereunder,  income,
gain, loss and deduction with respect to any property contributed to the capital
of the  Company  or which has been  adjusted  pursuant  to  Treasury  Regulation

                                       9

<PAGE>

Section  1.704-1  (b)(2)(iv)(f)  shall,  solely  for  income  tax  purposes,  be
allocated  among the Members so as to take account of any variation  between the
adjusted  basis of such property to the Company for federal  income tax purposes
and its fair market  value  reflected  in the capital  accounts  initially or on
adjustment, as the case may be.

     (b) Any elections or other  decisions  relating to  allocations  under this
Section  3.3  shall  be made by the  Management  Committee  in any  manner  that
reasonably  reflects the purpose and  intention of this  Agreement.  Allocations
pursuant to this Section 3.3 are solely for purposes of federal, state and local
taxes and shall not affect,  or in any way be taken into  account in  computing,
any  Member's  Capital  Account  or share of  profits,  losses,  other  items or
distributions pursuant to any provision of this Agreement.

     3.4.  Fiscal  Year.  The  Fiscal  Year  of the  Company  for  both  tax and
accounting purposes (the "Fiscal Year") shall be the calendar year.

     3.5.  Partnership  for Tax  Purposes.  The  Members  hereby  agree that the
Company  shall be treated as a  partnership  for tax  purposes  under the United
States federal, state and local income tax laws or other laws, and further agree
not to take any position or to make any election,  in a tax return or otherwise,
inconsistent herewith,

     3.6. Tax Matters.  (a) The tax matters partner ("Tax Matters  Partner") for
purposes  of  Section  623 of the Code  shall  be  Progenics.  Unless  otherwise
required by law, the Tax Matters  Partner (i) shall not take any action pursuant
to this Section 3.6 unless such action has been  consented to by each Member and
(ii) shall  perform  all such  duties and  responsibilities  as directed by each
Member.

     (b) All  elections by the Company for income and franchise tax purposes and
all determinations regarding the book basis, depreciation or amortization of any
Company  assets,  and all other matters  relating to all tax returns  (including
amended returns),  including the  characterization  and allocation of income and
loss,  filed by the  Company,  including  tax audits  and  related  matters  and
controversies,  shall be made and  conducted  by the Tax Matters  Partner at the
expense of the Company,  subject to the approval of each Member. The Tax Matters
Partner shall, at the expense of the Company and subject to the approval of each
Member,  cause to be  prepared  and filed  all tax  returns  (including  amended
returns) required to be filed by the Company;  provided,  however,  that CYTOGEN
shall have the  opportunity to review any and all tax returns in advance of such
filing. In the event of a dispute between the Members concerning the preparation
and filing of the Company's tax returns,  the Members hereby agree to submit the
dispute  to  arbitration  to one of the  major  nationally-recognized  certified
public  accounting  firms,  whose  decision  on the  matter  shall be final  and
binding.

     (c) The Tax Matters  Partner shall be responsible  for all  negotiations on
behalf of the Company with the Internal  Revenue  Service or the  Departments of
the Treasury or Justice or any state or local tax authority  with respect to the
income tax  treatment of Company  items,  and shall provide each Member with the
opportunity,  at the  expense  of  the  Company,  to  participate  in  any  such

                                       10

<PAGE>

negotiations.  The Tax Matters Partner shall not bind any Member to a settlement
agreement unless each Member has given its written consent to such agreement.

     3.7. Cash Flow Distributions.  Cash flow distributions of the Company shall
be made only after  payment of all  liabilities  and expenses of the Company and
establishment of reasonable  reserves.  Such distributions  shall be made to the
Members in accordance  with their  Percentages at such times and in such amounts
as determined by the  Management  Committee in its sole,  exclusive and complete
discretion.

     3.8.  Liquidating  Distributions Upon Dissolution.  Upon dissolution of the
Company, the remaining assets shall be applied as follows:

     (a) First,  to payment of the  liabilities  of the  Company  owing to third
parties  and then to  Members,  as  creditors.  After  payment of any such known
liabilities,  the Management  Committee shall set up such reasonable reserves as
it deems  reasonably  necessary for any contingent or unforeseen  liabilities or
obligations of the Company.  Such reserves  shall be held in a separate  account
for the  purpose of paying any such  contingent  or  unforeseen  liabilities  or
obligations,  and, at the expiration of such period as the Management  Committee
may deem  advisable,  such reserves shall be distributed to the Members or their
assigns in the manner set forth in Section 3.8(b) hereof.

     (b)  Second,  to the  Members  in  accordance  with their  Capital  Account
balances.  If such  distributions  are  insufficient to return to any Member the
full amount of its Capital  Account,  such Member shall have no recourse against
any other Member. If the Management Committee determines that the Company should
distribute any of its assets in kind, such assets shall,  except as set forth in
the following sentence, be distributed on the basis of their fair market values,
as determined by an appropriate  appraisal procedure as set forth or approved by
the  Management  Committee,  and the Capital  Accounts  of the Members  shall be
adjusted  prior to  liquidating  distributions  being  made to  reflect  how any
resulting  gain or loss would have been  allocated  under  Section 3.1 hereof if
such assets had been sold.  In the event of a dispute over the proper  valuation
of the Company's  in-kind  assets,  either Member shall have the right to submit
such dispute to arbitration in accordance with Section 10.2 hereof.  Each Member
shall have the right to require the Company to make the  distributions set forth
in this Section 3.8(b) first with any in-kind assets  contributed by such Member
to the  Company,  but only to the extent  such  distributions  do not exceed the
amount to which  such  Member  is  entitled  pursuant  to this  Section  3.8(b);
provided,  however,  that any and all  Intellectual  Property  transfers  from a
Member to the Company that were transferred without any value being reflected in
the  transferor's  Capital  Account  shall be  reconveyed  to the  transferor in
addition  to, and  without  diminishing,  any other  distributions  to which the
transferor shall be entitled. Upon the Company's dissolution, any and all rights
to other  Intellectual  Property,  developed or acquired by the Company prior to
its  dissolution  (such  Company  developments  and  acquisitions   collectively
referred to as the "Company  Inventions"),  shall be co-owned by  Progenics  and
CYTOGEN.

     3.9. Tax  Distributions.  To the extent that for any Fiscal Year the amount
of net income and gains of the  Company  allocated  to each  Member  exceeds the


                                       11

<PAGE>

amount of losses of the  Company  allocated  to that  Member  for that and prior
Fiscal  Years  reduced  by the  amount of net  income  and gains of the  Company
allocated to the Members for prior Fiscal Years, the Management  Committee shall
use reasonable  efforts to cause the Company to distribute to each Member, as an
advance against the amounts thereafter  distributable to it pursuant to Sections
3.7 and 3.8,  no later than  April 1 of the  following  year,  an amount of cash
equal to (a) the amount  reasonably  calculated by the  Management  Committee to
equal the amount of the  federal,  state and local tax  liability on that excess
(based on the highest  individual or corporate  marginal federal income tax rate
for that year and the  percentage  with  respect  to state and local  income tax
rates for that year that the Management Committee determines appropriate),  less
(b) the aggregate  amount of prior  distributions  by the Company to that Member
for such Fiscal Year. No such distribution shall be made, however, to the extent
that  distributions  are  restricted  under the  terms of any note or  agreement
relating  to  borrowings  by the  Company or to the extent  that the  Management
Committee  determines  that  the  cash is  necessary  for the  operation  of the
business of the Company or for the  establishment  of reasonable  reserves or if
the Company would be rendered insolvent.  The Management Committee shall, to the
extent practical,  make  distributions  under this Section 3.9 annually based on
projections  of income.  If upon the  liquidation  of the Company the  aggregate
amount of  distributions  to any Member pursuant to this Section 3.9 exceeds the
aggregate  amount that would have been  distributed  to that Member  pursuant to
Sections  3.7 and 3.8 hereof (had there been no  distributions  pursuant to this
Section 3.9),  then that Member shall pay to the Company an amount equal to such
excess,  to be distributed  to the other Member in accordance  with Sections 3.7
and 3.8 hereof.

     3.10. Deficit Capital Account  Restoration.  Except as provided in the last
sentence of Section  3.9 hereof,  no Member  shall have any  obligation  to make
Additional Capital  Contributions to the Company in order to restore any deficit
Capital Account  balance upon  liquidation of the Company or liquidation of such
Member's Interest in the Company.

     3.11. Other Distributions.  Except as provided in this Agreement, no Member
shall be  entitled  to receive any  distribution  from the  Company  without the
consent of all other Members.



                                   ARTICLE IV
                                   MANAGEMENT

     4.1. Management Committee.  (a) Except as otherwise reserved to the Members
pursuant to this  Agreement,  the overall  management and control of the Company
shall  be  exercised  by  the  Members  through  a  committee  (the  "Management
Committee").  Except as determined by the Management  Committee pursuant to this
Article IV or  otherwise  pursuant to this  Agreement,  no Member shall have any
right or  authority  to take any action on behalf of the Company with respect to
third parties.

     (b) The Management  Committee  shall consist of four  individuals  (each, a
"Representative")  or  such  other  number  of  individuals  as  the  Management


                                       12

<PAGE>

Committee  may,  from time to time  determine.  Of the  initial  members  of the
Management  Committee,  two shall be  appointed  by  Progenics  and two shall be
appointed by CYTOGEN.  The initial  Representatives of the Management  Committee
are:

                  Progenics:                [CONFIDENTIAL TREATMENT HAS BEEN
                                            REQUESTED]



                  CYTOGEN:                  [CONFIDENTIAL TREATMENT HAS BEEN
                                            REQUESTED]



Each Representative shall hold office until death, resignation or removal at the
pleasure of the Member which appointed such Representative.  If a vacancy occurs
on  the  Management   Committee,   the  Member  which   appointed  the  vacating
Representative shall appoint such Representative's successor.

     (c) Meetings of the Management Committee shall be held on two Business Days
(as defined  herein)  written notice (which may be waived and shall be deemed to
be waived by attendance at the meeting,  unless an individual objects,  prior to
or at the  beginning  of the  meeting,  to holding  the  meeting or  transacting
business  at  the  meeting).  Attendance  may  be in  person  or  by  conference
telephone.  Notwithstanding  the  number of  Representatives  on the  Management
Committee,  each Member's  Representatives  shall be required to vote as a block
("Voting  Block")  on behalf of such  Member.  The  Voting  Block of a  Member's
Representatives as of any given date shall equal such Member's  Percentage as of
such date. The Voting Blocks shall be automatically  adjusted upon any change in
Percentage of any appointing  Member.  Except as set forth in the next sentence,
the Management Committee shall act by vote of the Representative(s) whose Voting
Block constitutes more than  [CONFIDENTIAL  TREATMENT HAS BEEN REQUESTED] of the
aggregate Voting Blocks of all  Representatives,  at a meeting of the Management
Committee duly called and held.

     (i) All Major Decisions (as defined hereinafter) shall be made by a vote of
the  Representative(s)  whose Voting Block  constitutes more than  [CONFIDENTIAL
TREATMENT  HAS  BEEN   REQUESTED]   of  the  aggregate   Voting  Blocks  of  all
Representatives  (a  "Supermajority  Vote").  A "Major Decision" means decisions
concerning  the  merger or  consolidation  of the  Company or the sale of all or
substantially all of the Company's assets.

     (ii)  The  vote of each  Member  shall  be cast by such  Member's  Managing
Representative (as defined  hereinafter).  The Management Committee may also act
by unanimous written consent of the Representatives.  The Representatives  shall
not be  compensated  for  their  services  as such,  but  shall be  entitled  to
indemnification  by the Company in  accordance  with  Section  4.3  hereof.  Any
Deadlock (as defined  hereinafter) of the Management Committee shall be resolved
pursuant to Section 4.1(f) hereof.

                                       13
<PAGE>

     (d) Any  Representative  on the Management  Committee (or alternatively the
Member who appointed such Representative) may appoint another  Representative on
the Management Committee to act for him or her, and the Management Committee may
delegate in writing,  to any of the  Representatives  or to any Member or to any
other agent such  authority  to act on its behalf or on behalf of the Company as
it shall deem appropriate.

     (e) Subject to the other  provisions of this Agreement and the requirements
of applicable law, the Management  Committee  shall have the full,  complete and
exclusive power and discretion to take all action that it considers necessary or
desirable in connection with the management of the Company, and may exercise, on
behalf of the Company,  all of the powers of a limited  liability  company under
the Act including, without limitation, the following powers:

     (i) to enter into contracts or agreements of any kind,  including  selling,
leasing, conveying, licensing, exchanging or otherwise transferring or disposing
of any  Company  property  or  assets,  as well as  contracts  of  guaranty  and
suretyship  with  any  person  including  with  any  Member,  Representative  or
affiliate of either of them without the vote of the Members;

     (ii)  to  determine  the   strategies   and  methods  for   developing  and
commercializing  products and for exploiting the intellectual property rights of
the Company;

     (iii) to establish and  maintain,  or cause to be  maintained,  the Capital
Accounts  of the Members and the books and records of the Company as required by
law and by this Agreement;

     (iv) to appoint such  Officers (as defined  hereinafter)  of the Company as
the Management Committee determines desirable, and such Officers of the Company:

          (1) need not be members or Representatives;

          (2) shall have the powers and duties  delegated  to them by the
Management Committee; and

          (3) shall serve at the pleasure of the Management Committee;.

     (v) to employ and dismiss  attorneys,  accountants,  independent  auditors,
custodians,  brokers and such other  advisers or agents in  connection  with any
matter relating to the business of the Company  (including,  without limitation,
the  Representatives on the Management  Committee or persons or firms affiliated
with them) and to make payment for such  services and other  expenses out of the
funds of the Company;

     (vi) to open, maintain and close bank accounts for the Company;

                                       14
<PAGE>
     (vii) to sign checks of the Company;

     (viii) to admit additional members to the Company;

     (ix) to call meetings of the Members of the Company;

     (x) to declare and make distributions;

     (xi) to permit, require or prohibit withdrawals of capital from and Capital
Contributions to the Company;

     (xii) to hold part of the assets of the Company in cash  without  liability
for  interest  or the  payment  of  expenses  or  the  making  of  distributions
therewith;

     (xiii) to determine the  accounting  period or accounting  periods to which
any  income,  gain,  obligation,  loss,  liability,   deduction  or  expense  is
attributable;

     (xiv) to prepare,  execute and file tax returns or information  returns for
the Company and to make tax elections as they deem  appropriate,  subject to the
provisions of Section 3.6 hereof;

     (xv) to incur indebtedness for any purpose;

     (xvi)  to  make  loans,   including  loans  to  Members,   and  to  provide
indemnification  or  guarantee  the  indebtedness  and  obligations  of  others,
including Members;

     (xvii) to settle, compromise,  assign, pledge, transfer, release, submit to
arbitration,  or stipulate to  judgment,  or consent to do the same,  any claim,
suit, demand or judgment against the Company;

     (xviii) to delegate authority to subcommittees,  Members,  Representatives,
Officers or other  parties to take  actions on behalf of the Company  consistent
with the  terms of this  Agreement  and to  execute  documents  on behalf of the
Company in connection therewith; and

     (xix) to bring,  threaten to bring or prosecute,  on behalf of the Company,
any claim in a judicial proceeding or arbitration forum.

     (f) If, at any time the vote of the  Representatives  required  to  approve
action  with  respect  to a  particular  matter  has  not  been  obtained  after
comprehensive discussion between the Representatives, and such failure to obtain
the  requisite  vote impedes in any material  respect the  Company's  ability to
continue its business (the  "Deadlock"),  the Deadlock  shall first be submitted
(the "Submission") by the Management  Committee (but if the Management Committee
cannot agree on the form or substance of the  Submission,  the Submission may be
made by any  Representative) to the Chief Executive Officer of Progenics and the


                                       15
<PAGE>

Chief Executive Officer of CYTOGEN for review and discussion. Such persons shall
meet as soon as possible after the Submission is given,  and in any event within
ten calendar  days,  and endeavor in good faith to resolve the matter.  If these
officers do not,  within ten calendar  days after they first meet,  or within 20
calendar days after the  Submission is given,  mutually  resolve the Deadlock or
agree on a method of resolving  the Deadlock,  either Member may,  within the 30
calendar  day period  following  such 20  calendar  days after  delivery  of the
Submission,  by written  notice  given to the other  Member  within  such 30 day
period,  cause the Deadlock to be submitted to  arbitration  pursuant to Section
10.2 hereof.

     (g) (i) If submission of a Deadlock to the procedures  described in Section
4.1(f) does not,  within the time periods  specified in Section  4.1(f)  hereof,
result in resolution of the Deadlock,  submission of the Deadlock to arbitration
or  agreement by the Members on an  alternative  dispute  resolution  procedure,
either party may elect to exercise the buy/sell right  contained in this Section
4.1(g) (the  "Buy/Sell  Right").  The Member  electing to exercise  the Buy/Sell
Right  (the  "Offeror")  shall  furnish  in  writing  to the other  Member  (the
"Offeree") the Offeror's irrevocable,  unconditional (except as provided herein)
and  binding  offer  (such  notice  being  referred  to herein as the  "Exercise
Notice") to purchase the Offeree's  Interest or to sell the  Offeror's  Interest
for a cash  purchase  price  determined in  accordance  with Section  4.1(g)(ii)
hereof (the  "Purchase  Price").  The Exercise  Notice shall set forth an amount
expressed in dollars and without  contingencies (the "Valuation"),  which amount
shall be used to calculate,  in accordance with Section  4.1(g)(ii)  hereof, the
Purchase Price.  The Valuation is intended to represent the amount that would be
payable for 100% of the Interests of the Company.  Within 15 calendar days after
the Exercise Notice is given,  the Offeree may give notice to the Offeror of its
irrevocable,  unconditional  (except as provided  herein)  and binding  election
either:

     (1) to  purchase  the entire  Interest of the Offeror for an amount in cash
equal to the Purchase Price; or

     (2) to sell its entire  Interest to the Offeror for an amount in cash equal
to the Purchase Price.

Failure of the Offeree to give  notice of its  decision  within such  applicable
time period shall  constitute  a conclusive  election by the Offeree to sell its
entire Interest pursuant to this Section 4.1(g)(i).

     (ii)  The  Purchase  Price  shall  be  equal  to  the  seller's  Percentage
multiplied by the Valuation.

     (iii) Subject to the provisions of Section 4.1(g)(iv) hereof, a transfer of
Interests  pursuant to this  Section  4.1(g) shall take place at a closing to be
held on a day other than Saturday,  Sunday or any other day on which  commercial
banks  located  in New York,  New York are  authorized  by law to be closed  for
business  ("Business  Day").  Such date shall be  selected by and set forth in a
notice by the  Offeror  given  promptly  after the Offeree  gives  notice of its
election under Section 4.1(g)(i)  hereof,  which date shall be at least ten days
but prior to 20 days  after the  Offeree  gives  notice  of its  election  under
Section 4.1(g)(i), at such location in New York, New York as the Offeror selects

                                       16
<PAGE>

or as otherwise agreed to by the parties.  In such notice, the purchasing Member
shall  additionally  specify  whether the  purchase  will be by the Member,  the
Company, a combination of the Company and the Member,  and/or the designee(s) of
the  Company  and/or the  designee(s)  of the Member (the  "Purchaser").  At the
closing,  the Purchase Price  specified  above shall be paid by the Purchaser by
wire transfer of immediately available federal funds to an account designated by
the selling Member.  The terms of the purchase and sale shall be  unconditional,
except that the selling Member shall represent and warrant to the Purchaser that
its  Interest  in the Company is not  subject to any legal or  equitable  claims
(other than legal or equitable claims to such Interest, if any, of the Purchaser
pursuant  to this  Agreement)  and shall  deliver at the  closing an  instrument
confirming such  representation and warranty.  In addition,  the Purchaser shall
represent  and warrant to the selling  Member that it has the full right,  power
and  authority to  effectuate  the purchase and upon demand shall deliver at the
closing an instrument confirming such representation and warranty. Upon the sale
of a Member's  Interest in the  Company  pursuant to this  Section  4.1(g),  the
selling Member's appointed Representatives shall be deemed to have automatically
resigned from the Management Committee.

     (iv) The  closing  date set forth in Section  4.1(g)(iii)  hereof  shall be
postponed if any required  regulatory filings have not been made or any required
consents or approvals  (regulatory or otherwise)  have not been received by such
closing  date,  but only until such filings have been made or such consents have
been received and, if applicable, until the expiration or earlier termination of
the applicable waiting period under the Hart-Scott-Rodino Antitrust Improvements
Act of 1976, as amended (the "HSR Act").  The Members  hereby agree to use their
reasonable  best  efforts  and to  cooperate  with each other to effect any such
required  regulatory  filings,  including but not limited to, a filing under the
HSR Act, if applicable,  and to obtain any such required  consents or approvals,
in order to close a transfer of Interests pursuant to this Section 4.1(g).

     (v) The consummation of any purchase or sale of Interests  pursuant to this
Section 4.1(g) shall be subject to the satisfaction of the provisions of Section
6.2 hereof.

     (h) Each of Progenics and CYTOGEN shall appoint one managing Representative
(the  "Managing  Representative")  from  the  Representatives.  Every  contract,
agreement,  certificate,  document or other instrument executed by both Managing
Representatives  shall be conclusive  evidence in favor of every person  relying
thereon or claiming  thereunder that, at the time of the delivery  thereof,  (1)
the Company was in  existence,  (2) this  Agreement  had not been  terminated or
canceled or amended in any manner so as to restrict  such  authority  (except as
shown in any  instrument  duly filed  under the Act) and (3) the  execution  and
delivery  thereof was duly  authorized by the Management  Committee.  Any person
dealing  with the  Company or the  Management  Committee  may,  until and unless
subsequently  notified by both Managing  Representatives,  rely on a certificate
signed by both Managing Representatives hereunder:

     (i)  as  to  who  are  the  Representatives  and  Managing  Representatives
hereunder;


                                       17

<PAGE>

     (ii)  as to the  existence  or  nonexistence  of any  fact or  facts  which
constitute  conditions  precedent to acts by the Management  Committee or are in
any other manner germane to the affairs of the Company;

     (iii) as to who is  authorized  to  execute  and  deliver  any  instrument,
contract, agreement, certificate or document for the Company;

     (iv) as to the  authenticity  of any copy of this  Agreement and amendments
thereto; or

     (v) as to any  act or  failure  to act by the  Company  or as to any  other
matter whatsoever involving the Company.

     (i) The  Management  Committee  shall  establish an  Intellectual  Property
subcommittee,  composed of such  members of the  Management  Committee,  or such
other persons, as the Management Committee may determine and with such authority
as may be delegated  thereto.  The  Intellectual  Property  Committee shall have
responsibility for establishing and implementing,  in consultation with counsel,
the Company's strategies for creating and/or maintaining its patent estate.

     4.2. Meetings of Members.  The Members shall meet on such periodic basis as
the Management Committee may determine. Special meetings of the Members, for any
purpose or purposes,  may be called by the Management Committee or by any Member
of the Company.  All meetings shall be held at the Company's  principal place of
business or at any other place  designated  by the  Management  Committee,  and,
unless  otherwise  prohibited  by law, may be  conducted by means of  conference
telephone  or  similar  communication   equipment,  in  the  discretion  of  the
Management  Committee.  Not less than two Business Days before each meeting, the
Management  Committee  shall give  written  notice of the meeting to each Member
entitled to vote at the meeting.  The notice shall state the place,  date,  hour
and purpose of the  meeting.  Notwithstanding  the  foregoing  provisions,  each
Member who is entitled to notice  shall be deemed to have waived  notice if such
Member  attends the  meeting,  unless such  Member  objects,  prior to or at the
beginning of the meeting, to holding the meeting or transacting  business at the
meeting.  At any such meeting of Members,  the presence in person or by proxy of
the Members  holding an  aggregate  of a majority  in  Interests  constitutes  a
quorum.  A member may vote either in person or by written  proxy signed by or on
behalf  of the  Member  or by or on  behalf  of  the  Member's  duly  authorized
attorney-in-fact.

In lieu of holding a meeting,  the Members may vote or otherwise  take action by
the unanimous written consent of the Members.

     4.3.  Liability and  Indemnification.  (a) Except as otherwise  provided by
law, none of the  Representatives,  any Officer or any Member  designated by the
Management Committee to act on its behalf (or any officer, director, employee or
affiliate of any such Member),  in each case acting in such  capacity,  shall be
liable,  responsible  or  accountable in any way for damages or otherwise to the
Company or to any of the Members  for (a) any act or failure to act  pursuant to
this  Agreement  or  otherwise  if (i) such person  acted in good faith and in a



                                       18
<PAGE>

manner it reasonably  believed to be in, or not opposed to, the interests of the
Company,  (ii) the conduct of such person did not constitute  gross  negligence,
fraud, bad faith, intentional misconduct or a knowing violation of law and (iii)
such person did not gain a financial  benefit to which he or she was not legally
entitled,  or (b) any  losses  due to the  negligence  or  unauthorized  acts of
advisers, consultants or other agents of the Company.

     (b)  The  Company   shall   indemnify,   defend  and  hold   harmless  each
Representative,  each Officer and any Member  designated to act on behalf of the
Management Committee (and any officer,  director,  employee and affiliate of any
such Member),  in each case acting in such capacity (an  "Indemnified  Person"),
from and against any claims, losses,  liabilities,  damages,  fines,  penalties,
costs  and  expenses  (including,   without  limitation,   reasonable  fees  and
disbursements  of  counsel  and  other  professionals)  arising  out  of  or  in
connection  with any act or failure to act by an Indemnified  Person pursuant to
this Agreement, or the business and affairs of the Company;  provided,  however,
that an Indemnified Person shall not be entitled to indemnification hereunder if
it is  judicially  determined  that (a) such  Indemnified  Person's  actions  or
omissions to act were (i) made in bad faith,  (ii) constituted gross negligence,
fraud,  intentional  misconduct or a knowing violation of law, or (iii) were the
result of active  and  deliberate  dishonesty,  or (b) such  Indemnified  Person
personally  gained a  financial  benefit  to which  Indemnified  Person  was not
legally entitled.

     4.4.  Duties,  Right to Conduct Other Business.  (a) To the extent that, at
law or in equity, a Member (or any officer, director or employee of such Member)
has duties (including  fiduciary duties) and liabilities relating thereto to the
Company or to the Members, (i) the Member (or any officer,  director or employee
of any Member) acting under this  Agreement or otherwise  shall not be liable to
the Company or to any Member for its good faith  reliance on the  provisions  of
this Agreement, and (ii) such Member's duties and liabilities (or the duties and
liabilities of any officer,  director or employee of any Member) may be expanded
or restricted by the provisions of this Agreement.

     (b) For so long as Progenics and CYTOGEN are Members of the Company and for
a period of three years thereafter  (unless the Company  liquidates  pursuant to
Article VII hereof),  neither Progenics nor CYTOGEN will engage, either directly
or  indirectly,  in  the  research,  development,  manufacturing,  marketing  or
commercialization  of products  in the Field  except for the benefit of the LLC.
Notwithstanding  the foregoing,  this Agreement  shall not preclude or limit, in
any respect, the rights of Progenics and CYTOGEN to engage in activities outside
of the Field,  whether or not such activities are competitive with activities of
the Company,  and neither  Progenics  nor CYTOGEN  shall have any  obligation to
offer such business activities to the Company.

     (c) For so long as Progenics and CYTOGEN are Members of the Company and for
a period of three years thereafter  (unless the Company  liquidates  pursuant to
Article VII hereof),  neither  Progenics nor CYTOGEN shall solicit or induce any
person who is employed by or who is a consultant  to or is otherwise  affiliated
with the Company to terminate his or her employment,  consultancy or affiliation
with the Company. In addition,  for so long as Progenics and CYTOGEN are Members

                                       19

<PAGE>
of the Company and for a period of three years thereafter, neither Progenics nor
CYTOGEN  shall  solicit  or induce any  person  who is  employed  by or who is a
consultant to or otherwise  affiliated with the other Member to terminate his or
her employment, consultancy or affiliation with the other Member.

     4.5.  Scientific   Advisory  Board.  The  Management   Committee  shall  be
authorized to establish a Scientific  Advisory Board (the "SAB").  The SAB shall
be composed of such  scientific or other  personnel as the Management  Committee
deems  advisable  and may include as members  employees and  consultants  of the
Company as well as persons  otherwise  unaffiliated  with the  Company.  The SAB
shall meet at such places and at such times as shall be determined as advisable.
The Management  Committee may authorize  compensation  for members of the SAB in
such amounts and under such terms as the Management Committee may determine.

     4.6. Research Grants.  Neither Progenics nor CYTOGEN shall, so long as such
person is a member of the  Company,  apply to any funding  source for a Research
Grant in the  Field  unless  such  application  is made for the  benefit  of the
Company.

                                   ARTICLE V
                                    OFFICERS

     5.1.  Designation,  Authority and Compensation of Officers.  The Management
Committee may delegate such of its authority as it deems  advisable from time to
time to officers of the Company, including, without limitation, a president, one
or more vice-presidents and/or a secretary/treasurer (an "Officer").  The title,
extent of  authority,  term of office and  compensation  of any Officer shall be
determined by the Management Committee in its sole discretion.

     5.2.  Tenure of  Officers.  The  Officers of the Company  shall hold office
until  their  successors  are chosen and  qualify,  unless a  different  term is
specified by the Management  Committee in appointing  the Officer,  or until the
Officer's  earlier  death,  resignation  or removal.  Any Officer  chosen by the
Management Committee may be removed at any time by the Management Committee,  in
its sole  discretion,  and any vacancy  occurring in any office may be filled by
the  Management  Committee,  in its sole  discretion.  Any Officer may resign by
delivering his or her written  resignation to the Company at its principal place
of  business.  Such  resignation  shall be effective  upon receipt  unless it is
specified to be effective at some other time or upon the happening of some other
event.

                                   ARTICLE VI
          TRANSFER OF INTERESTS, WITHDRAWAL AND TERMINATION OF MEMBERS

     6.1. Transfer or Withdrawal Prohibited;  Change of Control of a Member. (a)
Except as expressly  provided herein, no Member may withdraw from the Company or
sell,  assign,  transfer,  pledge,  hypothecate,  mortgage  or create a security
interest,  directly  or  indirectly  ("Transfer"),  in all or any portion of its


                                       20
<PAGE>

Interest  without the prior written consent of the Management  Committee,  which
consent may be withheld in the sole and absolute  discretion  of the  Management
Committee.  Any  purported  withdrawal  or  Transfer  of an Interest by a Member
without the requisite consent in writing shall be null and void, and the Company
shall be  entitled  to damages as a result of,  and/or  injunctive  relief  with
respect to, any attempts to withdraw or Transfer.

     (b) In the event that the Management  Committee consents to a Transfer of a
Member's  Interest,  such consent shall,  unless expressly stated otherwise,  be
deemed a consent only to the  assignment of such Member's  economic  interest in
profits,  losses  and  distributions  and shall  not be deemed a consent  to the
admission of such  assignee as a member of the Company as a  substitute  for the
assignor,  and such assignee shall not have any of the rights of a member of the
Company, including,  without limitation,  voting rights, unless otherwise stated
in writing by the Management Committee. Except to the extent that the Management
Committee  has  consented  to the  admission  of the assignee as a member in the
Company and/or  consented to the exercise of voting rights by the assignee,  the
assigning  Member  shall  retain  all  voting  rights  in  connection  with  the
transferred Interest.

     (c) In the event  that at any time  there  occurs a Change of  Control  (as
hereinafter  defined) of a Member,  such Member's  Interest shall  automatically
convert into an economic interest only in the profits,  losses and distributions
of the  Company,  and such Member shall not have any other rights of a member of
the Company,  including,  without  limitation,  voting and marketing rights. For
purposes hereof, a "Change in Control" shall be deemed to have occurred:  (i) on
the sale or other disposition of all or substantially all of the Member's assets
to any  entity,  person or related  group of  persons;  (ii) when there shall be
consummated  any  consolidation,  merger,  reorganization  or similar  corporate
transaction (a "Corporate Transaction") of the Member (A) in which the Member is
not the  continuing or surviving  entity (other than a  consolidation  or merger
with a wholly owned subsidiary of the Member in which all shares of common stock
of such Member  outstanding  immediately prior to the effectiveness  thereof are
changed into or exchanged for the same  consideration)  or (B) pursuant to which
the common  stock of such Member  would be converted  into cash,  securities  or
other  property,  in each case,  other than a  Corporate  Transaction  that is a
Qualifying  Corporate  Transaction (as defined below); (iii) when any person, or
any persons  acting  together  which would  constitute a "group" for purposes of
Section 13(d) of the Securities Exchange Act of 1934, as amended,  together with
any affiliates  thereof,  shall beneficially own (as defined in Rule 13d-3 under
the  Exchange  Act) at least 50% of the total  voting  power of all  classes  of
capital  stock of the Member  entitled  to vote  generally  in the  election  of
directors of the Member  (unless the  "acquisition"  is deemed to have  occurred
indirectly solely as a result of the completion of a Corporate  Transaction that
is not a Change in Control pursuant to clause (ii) above); (iv) when at any time
during any consecutive two-year period, individuals who at the beginning of such
period  constituted the Board of Directors of the Member  (together with any new
directors  whose  election by such Board of  Directors or whose  nomination  for
election by the  stockholders of the Member was approved by a vote of 75% of the
directors  then still in office who were either  directors  at the  beginning of
such period or whose  election or  nomination  for  election was  previously  so
approved)  cease  for any  reason  to  constitute  a  majority  of the  Board of


                                       21
<PAGE>
Directors of the Member then in office;  or (v) when the Member is liquidated or
dissolved  or  adopts  a plan  of  liquidation  or  dissolution.  A  "Qualifying
Corporate  Transaction" shall be any Corporate  Transaction in which the holders
of common stock of the Member  immediately  prior to such Corporate  Transaction
have, directly or indirectly,  at least (i) a majority of the total voting power
of all classes of capital  stock  entitled to vote  generally in the election of
directors of the continuing or surviving entity immediately after such Corporate
Transaction in  substantially  the same  proportion as their ownership of common
stock  before  such  transaction  or (ii) 25% of the total  voting  power of all
classes of capital stock entitled to vote generally in the election of directors
of  the  continuing  or  surviving  entity   immediately  after  such  Corporate
Transaction in  substantially  the same  proportion as their ownership of common
stock before such  transaction  and, in the case of this clause (ii),  the other
Member has given a CIC Approval.  A "CIC  Approval"  shall be given by the other
Member if such  Member  cannot  conclude  in good  faith  and in its  reasonable
judgment after  discussions  with the parties to the Corporate  Transaction that
such Corporate  Transaction and any resulting change in management or leadership
is reasonably  likely to disrupt or delay the  commercialization  of products by
the LLC, or fundamentally  alter the approach,  philosophy or vision of the LLC,
giving due regard to the importance of good-faith  cooperation and collaboration
and  single-mindedness of purpose between CYTOGEN and Progenics which has formed
the basis for the collaboration  initially contemplated by the parties hereto. A
CIC Approval may not be unreasonably  withheld,  and failure of the other Member
to give a CIC Approval may be  contested in  arbitration  pursuant to Article 10
hereof. Notwithstanding the foregoing, a Change of Control shall not include any
transaction  the  purpose  of  which is to  reorganize  the  Member's  corporate
structure,  reincorporate  the Member in another  jurisdiction  or undertake any
other action which does not have the purpose or effect of  materially  affecting
the ownership and/or control of the Member at the time of such transaction.


     6.2. Regulatory  Matters.  Anything in this Article VI or elsewhere in this
Agreement to the contrary notwithstanding,  no assignment, transfer, encumbrance
or other  disposition of all or any part of any Member's  Interest shall be made
or  shall  be  effective  unless  (a)  prior to the  consummation  thereof,  all
assignees and transferees with respect thereto shall have made to the Company in
writing all of the  representations  required by the  Management  Committee,  to
ensure compliance with applicable  securities and other laws and (b) if required
by the  Management  Committee,  the Company is  provided  with an opinion of its
legal counsel,  or other legal counsel  satisfactory  to the Company's  counsel,
stating that (i) such assignment, transfer, encumbrances or other disposition is
exempt from the Securities Act of 1933, as amended, and is permissible under all
other  applicable  federal and state  securities  laws without  registration  or
qualification  of any  security  or any person and (ii) the  transaction  is not
prohibited  under,  and does not conflict with, such other federal or state laws
as the Management Committee may specify.

     6.3. Default;  Buyout/Liquidation  Option. (a) A Member shall be in default
("Defaulting  Member")  under this  Agreement  upon the occurrence of any of the
following events ("Default"):


                                       22
<PAGE>
     (i) the  Bankruptcy (as defined  hereinafter)  or dissolution of the Member
(the Bankruptcy or dissolution of the Member shall hereinafter be referred to as
the  "Dissolution"),  in which event such Member  shall  immediately  notify the
other Member  ("Other  Member") and the Company in writing of the  occurrence of
such Dissolution.

As used herein, the term "Bankruptcy" shall mean:

     (1) A  Member  files  a  voluntary  petition  in  bankruptcy  or  shall  be
adjudicated  a bankrupt or  insolvent,  or shall file any  petition or answer or
consent  seeking any  reorganization,  arrangement,  composition,  readjustment,
liquidation or similar relief for itself under the present or future  applicable
federal,  state or other  statute or law relating to  bankruptcy,  insolvency or
other  relief for  debtors,  or shall seek or  consent  to or  acquiesce  in the
appointment of any trustee,  receiver,  conservator or liquidator of said Member
of all or any  substantial  part of its  properties  or its  Interest  (the term
"acquiesce" as used in this  definition  includes the failure to file a petition
or motion to vacate or discharge any order, judgment or decree);

     (2) A court of competent  jurisdiction enters an order,  judgment or decree
approving  a  petition  filed  against  any  Member  seeking  a  reorganization,
arrangement,  composition,  readjustment,  liquidation,  dissolution  or similar
relief  under the  present or any future  federal  bankruptcy  act, or any other
present or future applicable federal,  state or other statute or law relating to
bankruptcy,  insolvency  or other  relief for  debtors,  and such  Member  shall
acquiesce in the entry of such order, judgment or decree or such order, judgment
or decree  shall remain  unvacated  and unstayed for an aggregate of 60 calendar
days  (whether  or not  consecutive)  from  the date of  entry  thereof,  or any
trustee,  receiver,  conservator  or  liquidator of such Member or of all or any
substantial  part of its properties or its Interest  shall be appointed  without
the consent or acquiescence of such Member,  and such  appointment  shall remain
unvacated  and unstayed for an  aggregate  of 60 calendar  days  (whether or not
consecutive);

     (3) A Member  admits  in  writing  its  inability  to pay its debts as they
mature; or

     (4) A Member  makes an  assignment  for the benefit of  creditors  or takes
other similar action for the protection or benefit of creditors.

     (ii) the Member has breached in any material  respect this  Agreement,  the
PSMA/PSMP License Agreement or the Services Agreement, which breach has not been
cured within 60 calendar days after the  Management  Committee or  non-breaching
Member has given a written notice to the breaching  Member stating that a breach
has occurred  and  identifying  in  reasonable  detail the  relevant  facts with
respect to such breach.

     (iii) on two occasions, an arbitrator determines that a Member has acted in
bad faith in refusing to approve a Budget pursuant to Section 2.4(b).


                                       23

<PAGE>

     (iv) so long as Progenics  and CYTOGEN are the only Members of the Company,
the Member's Percentage falls below [CONFIDENTIAL  TREATMENT HAS BEEN REQUESTED]
("Nonconforming  Percentage"), in which event (provided that at such time as any
Member's  Percentage  shall be reduced to zero,  such Member shall cease to be a
member in the Company) the Management  Committee  shall  immediately  notify all
Members in writing of the Nonconforming  Percentage.  Subsequently,  any further
reduction in such Member's  Percentage shall constitute a separate Default again
giving rise to the options under Section 6.3(b) hereof.

The Management  Committee  shall promptly (but in any event within five Business
Days) give notice (a "Default  Notice") to the Members of any Default under this
Section 6.3(a) of which it becomes aware.  The Other Member shall be entitled to
give the Default  Notice to the  Defaulting  Member on behalf of the  Management
Committee. In any event, failure to provide notice to the Defaulting Member does
not constitute a waiver of the default.

     (b) Upon the occurrence of a Default and the giving of the Default  Notice,
in each case as described in Section  6.3(a)  hereof,  (i) all marketing  rights
held by the  Defaulting  Party  under  Article  IX  hereof,  and all  rights  of
Progenics (if Progenics is the Defaulting  Party) under Section 2.2(d) hereof to
direct the application of the Progenics R&D Capital Contributions and to conduct
the research and development  program  contemplated  by the Services  Agreement,
shall  terminate and (ii) an option to purchase all but not less than all of the
Interest  of the  Defaulting  Member  shall  arise  immediately  in favor of the
Company  and/or the Other Member.  The  determination  as to whether the Company
will  exercise the purchase  option  shall be made by the Other  Member.  If the
purchase option is not exercised  within 45 calendar days from the giving of the
Default  Notice,  the Other Member may, but shall not be required to,  within 90
calendar  days from the giving of the  Default  Notice,  cause the Company to be
dissolved and liquidated pursuant to Article VII hereof.

     (c)  The  purchase  option  arising  under  Section  6.3(b)  hereof  may be
exercised  only by  giving a  written  notice  to the  Defaulting  Member of the
election to exercise such purchase option within the 45 calendar day time period
specified in Section 6.3(b) hereof (the "Exercise Notice").

     (d) If the Company  and/or the Other Member  exercises the purchase  option
arising under Section 6.3(b) hereof,  the purchase  price  determination  of the
Defaulting  Member's  Interest  shall  first  be  submitted  by  the  Management
Committee  to the  Chief  Executive  Officer  of  each  Member  for  review  and
discussion.  Such  persons  shall meet as soon as  possible  after the  Exercise
Notice is given, and in any event within ten calendar days, and endeavor in good
faith to determine  the purchase  price.  If these  officers do not,  within ten
calendar  days after  they  first  meet,  or within 20  calendar  days after the
Exercise  Notice  is  given,  mutually  agree  upon a  purchase  price  for  the
Defaulting  Member's  Interest,  either  Member may,  within the 30 calendar day
period following such 20 calendar days after delivery of the Exercise Notice, by
written  notice given to the other Member  within such 30 day period,  cause the
purchase price determination of the Defaulting Member's Interest to be submitted


                                       24
<PAGE>

to  arbitration  pursuant to Section 10.2  hereof.  In the event such dispute is
submitted  to  arbitration,  the  purchase  price  for the  Defaulting  Member's
Interest shall be calculated by the  arbitrator by multiplying  the total entity
value  of the  Company  (as  determined  by the  arbitrator)  by the  Defaulting
Member's Percentage.  In the event the Company and/or the Other Member exercises
the purchase  option,  the Company  and/or the Other  Member and the  Defaulting
Member  shall be  obligated to  consummate  the  purchase at the purchase  price
determined in the manner described above.

     (e) (i) Subject to the provisions of Section  6.3(e)(ii) hereof, a transfer
of  Interests  pursuant to this  Section 6.3 shall take place at a closing to be
held on a Business Day at least ten calendar  days but prior to 20 calendar days
after  the  determination  of the  purchase  price  of the  Defaulting  Member's
Interest  pursuant to Section 6.3(d)  hereof,  which date shall be determined by
mutual  agreement of the Members,  or if no agreement can be reached,  on a date
unilaterally set by the Company and/or the Other Member, at such location in New
York,  New York as the Company  and/or the Other Member  selects or as otherwise
agreed to by the parties.  In the Exercise Notice,  the Company and/or the Other
Member shall  additionally  specify  whether the  purchase  will be by the Other
Member, the Company,  a combination of the Company and the Other Member,  and/or
the  designee(s) of the Company and/or the  designee(s) of the Other Member (the
"Purchasing  Party(ies)").  At the closing,  the purchase price  specified above
shall be paid by the  Purchasing  Party(ies)  by wire  transfer  of  immediately
available federal funds to an account  designated by the Defaulting  Member. The
term of the purchase and sale shall be unconditional, except that the Defaulting
Member shall be deemed to  represent  and warrant to the  Purchasing  Party(ies)
that its Interest is subject to no legal or equitable  claims  (other than legal
or  equitable  claims to such  Interest,  if any, of the  Purchasing  Party(ies)
pursuant  to this  Agreement)  and shall  deliver at the  closing an  instrument
confirming  such  representation  and  warranty.  In  addition,  the  Purchasing
Party(ies) shall represent and warrant to the Defaulting  Member that it has the
full right, power and authority to effectuate the purchase and upon demand shall
deliver  at  the  closing  an  instrument  confirming  such  representation  and
warranty. Upon the sale of a Member's Interest pursuant to this Section 6.3, the
Member's  appointed  Representatives  shall  be  deemed  to  have  automatically
resigned from the Management Committee.

     (ii) The  closing  date set  forth in  Section  6.3(e)(i)  hereof  shall be
postponed if any required  regulatory filings have not been made or any required
consents or approvals  (regulatory or otherwise)  have not been received by such
closing  date,  but only until such filings have been made or such consents have
been received and, if applicable, until the expiration or earlier termination of
the applicable waiting period under the HSR Act. The Members hereby agree to use
their  reasonable  best efforts and to  cooperate  with each other to effect any
such required regulatory  filings,  including but not limited to, a filing under
the HSR Act,  if  applicable,  and to  obtain  any  such  required  consents  or
approvals,  in order to close a transfer of  Interests  pursuant to this Section
6.3.

     (f) The consummation of any purchase or sale of Interests  pursuant to this
Section 6.3 shall be subject to the  satisfaction  of the  provisions of Section
6.2 hereof.


                                       25
<PAGE>
     (g) A Defaulting Member shall be liable to the Company and the Other Member
for all damages  arising out of a Default and any other  amounts the  Defaulting
Member owes to the Company or Other  Member  pursuant to this  Agreement  or any
other  agreement,  and any such amounts may be offset against any other payments
otherwise due from the Purchasing Party(ies) to the Defaulting Member hereunder.
Exercise or failure to exercise any of the options  pursuant to this Section 6.3
shall not relieve the Defaulting  Member of the  liabilities  arising out of the
Default.

                                  ARTICLE VII
             DISSOLUTION, LIQUIDATION AND TERMINATION OF THE COMPANY

     7.1. Events of  Dissolution.  The Company shall be dissolved and liquidated
upon the first to occur of the following events:

     (a) Upon the unanimous written consent of the Management Committee.

     (b) Upon the termination of the Company's  business as a result of the sale
by the Company of all or substantially all of its business and assets.

     (c) Upon the Other Member's exercise of its right to dissolve and liquidate
the Company under Section 6.3 hereof.

     7.2. Procedure for Winding Up and Dissolution. If the Company is dissolved,
the Management  Committee shall wind up its affairs  pursuant to the appropriate
provisions  of the Act. On winding up of the Company,  the assets of the Company
shall be distributed in accordance with Section 3.8 hereof.

     7.3. Termination of Company. Upon the completion of the liquidation of' the
Company and the distribution of all Company assets,  the Company's affairs shall
terminate and the Management  Committee  shall execute and file a certificate of
cancellation  of the  Company's  Certificate,  as  well  as any  and  all  other
documents required to effect the termination of the Company under the Act.

     7.4. License Grants on Dissolution.  Upon dissolution of the Company,  each
Member (in each case, the "Grantee Member") shall be granted, at its request, by
the other Member (the "Grantor Member") a non-exclusive  license, with the right
to sublicense, for use in the Field to any Intellectual Property rights in which
the Grantor Member has a licensable right ("Grantor  Rights") to the extent that
the development and commercialization of any product or service that includes or
embodies  a  Company  Invention  (including  developing,  making,  having  made,
distributing,  using,  offering for sale,  selling,  having sold,  importing and
exporting such products and services) would in the absence of such non-exclusive
license,  infringe or conflict with such Grantor Rights. Royalties in respect of
such non-exclusive  license shall be payable at cost (calculated as described in
Section 5 of the  PSMA/PSMP  License  Agreement,  and including any milestone or
other  payments  required  to be  paid to any  licensor  of the  Grantor  Member
resulting from the  development or  commercialization  activities of the Grantee
Member  relating  to Company  Inventions).  Such  non-exclusive  licenses  shall
contain  such other  commercially  reasonable,  fair  market  value terms as the
parties shall in good faith agree.


                                       26
<PAGE>

                                  ARTICLE VIII
                  BOOKS, RECORDS, ACCOUNTING AND TAX ELECTIONS

     8.1. Bank  Accounts.  All funds of the Company shall be deposited in a bank
account or accounts opened in the Company's name. The Management Committee shall
determine the  institution or  institutions at which the accounts will be opened
and  maintained,  the types of accounts and the persons who will have  authority
with respect to the accounts and the funds therein.

     8.2.  Fiscal Year.  Pursuant to Section 3.4 hereof,  the Fiscal Year of the
Company for both  accounting and tax purposes shall be the calendar year.

     8.3. Method of Accounting.  The Company's  books (for accounting  purposes)
shall be maintained in accordance with generally accepted accounting principles.
The  determinations of the Management  Committee or the Tax Matters Partner,  as
the case may be, with respect to the treatment of any item or its allocation for
federal, state or local income tax purposes shall be binding upon all Members so
long as that  determination  is not inconsistent  with any express  provision of
this Agreement, provided that any determinations made by the Tax Matters Partner
are subject to the approval of CYTOGEN.

     8.4.  Books and  Records.  The books and  records of the  Company  shall be
maintained at the  Company's  expense under the  supervision  of the  Management
Committee at such office as the Management  Committee shall approve,  and may be
examined and copied there by any Member or its duly  authorized  representatives
at reasonable  times and upon  reasonable  notice.  The Company shall furnish to
each Member,  no later than 30 calendar  days after the end of each of the first
three fiscal  quarters,  quarterly and  year-to-date  statements of income and a
balance sheet as of the end of that  quarter.  The Company shall furnish to each
Member,  no later  than 45  calendar  days  after the end of each  Fiscal  Year,
financial  statements  of the Company with respect to that year  prepared by the
Company's  accountant  and  audited  by  the  accounting  firm  selected  by the
Management  Committee.  The  Company  will seek to  engage  the  services  of an
independent  auditing firm as its independent auditor upon terms satisfactory to
the Company.  The  financial  statements  shall  include a balance  sheet of the
Company as of the end of the Fiscal Year, a statement of operations, a statement
of Members' Interests and a statement of changes in cash flow of the Company for
the year. The Company shall also furnish to each Member copies of any additional
financial  reports  delivered  by the  Company to its  lenders and copies of all
financial reports.

     8.5.  Tax  Information.  Not later than the date of  delivery of the annual
financial  statements  pursuant to Section 8.4 hereof, the Management  Committee
shall cause the Company's  accountants to furnish to each Member any information
required by that Member to complete any income tax return that it is required to
file with respect to the year to which such  financial  statements  relate.  The
Company shall also furnish tax information to the Members on an interim basis to
the extent the Management Committee determines appropriate.


                                       27
<PAGE>

                                   ARTICLE IX
                                MARKETING RIGHTS

     9.1. Grant of North  American  Marketing  Rights.  Subject to the terms and
conditions  described  herein,  the  LLC  hereby  grants  to  CYTOGEN  exclusive
marketing rights with respect to Licensed Products sold in the United States and
Canada (the "North American Territory").  The exercise of such rights by CYTOGEN
is  conditioned  on CYTOGEN's  capability to perform the  marketing,  detailing,
distribution  and  other  promotional  and  selling   activities   (hereinafter,
"marketing  activities")  required  to be  performed  hereunder  and  under  the
Marketing Agreement (as hereinafter defined). Such determination shall take into
consideration  CYTOGEN's  ability to perform the  necessary  sales and marketing
functions  based  upon  an  assessment  of its  existing  sales,  marketing  and
distribution capabilities compared to those of other companies promoting similar
products to similar  market  segments,  as well as such other  factors as may be
reasonably relevant.

     9.2.  Diligence  Obligations.  CYTOGEN shall use diligent efforts to market
Licensed  Products in the North American  Territory  ("Diligent  Efforts").  For
purposes of the  foregoing,  "Diligent  Efforts"  shall mean  carrying  out such
obligation  in a  sustained  manner  consistent  with the  efforts a party would
devote to a product of similar market  potential,  profit potential or strategic
value resulting from its own research  efforts to which such party has exclusive
rights based on conditions  then  prevailing.  Diligent  Efforts  requires:  (i)
developing a strategic plan for product launch and subsequent market penetration
with defined  objectives;  (ii)  establishing  systems and protocols  reasonably
designed to achieve such objectives;  (iii) allocating  appropriate resources to
support such systems and protocol;  (iv) promptly  assigning  responsibility for
executing  all phases of the Marketing  Plan to specific  employees who are held
accountable for discharging their assigned responsibilities;  and (v) monitoring
on an ongoing  basis the  execution  of the  Marketing  Plan and its success and
making such changes as are  warranted by market and/or  operational  conditions.
CYTOGEN shall provide the LLC with access to all relevant records and personnel,
during normal business hours and with reasonable advance notice, under customary
confidentiality  conditions,  for the purpose of determining  the utilization by
CYTOGEN of Diligent Efforts to commercialize Licensed Products.

     9.3. Assistance by Progenics; Contingent Grant of Rights.(a) Subject to the
terms and conditions  described  herein,  Progenics  shall be entitled to assist
CYTOGEN, under the direction of CYTOGEN, in connection with marketing activities
regarding  Licensed  Products in any  territory  (including  the North  American
Territory)  in  which  CYTOGEN  has  been  granted  or is  subsequently  granted
marketing  rights  pursuant  hereto.  The  assistance  by Progenics in marketing
activities  shall be  conditioned  upon  Progenics'  capability  to augment in a
commercially  significant  manner the  marketing  activities  of CYTOGEN (or any
other person then responsible for marketing  Licensed  Products).  The nature of
the assistance in marketing  activities provided by Progenics will be determined
in good faith by Progenics and CYTOGEN,  with the approval of the LLC, from time
to time based on Progenics' capabilities.

                                       28

<PAGE>

     (b) [CONFIDENTIAL TREATMENT HAS BEEN REQUESTED]

     9.4. Marketing Agreement. The LLC, CYTOGEN and Progenics shall negotiate in
good  faith  the  terms  of  a  Product  Marketing   Agreement  (the  "Marketing
Agreement") to be entered into after the completion of Phase II clinical  trials
with respect to any Licensed Product.  The Marketing Agreement shall be based on
the terms set forth in this  Article IX, shall  include,  but not be limited to,
provisions  relating to marketing,  sales,  pricing and distribution of Licensed
Product and shall further define the rights, responsibilities and obligations of
the LLC,  CYTOGEN and Progenics with respect  thereto.  No term of the Marketing
Agreement shall be in conflict with any material term of this Article IX without
the written  agreement of the parties  hereto.  Until the terms of the Marketing
Agreement are agreed upon, such parties acknowledge and agree that the terms set
forth in this  Article  IX are fully  binding  and  enforceable.  The  Marketing
Agreement  shall  include  the  following  terms in  addition to the other terms
described above:

     (a) At least one year in advance of the anticipated  commercial  launch (as
determined in good faith by the LLC) of each Licensed Product in each country in
the North American  Territory,  CYTOGEN shall submit a plan (a "Marketing Plan")
for approval by the LLC for such commercial  launch and the subsequent period of
twelve months plus any subsequent  period prior to the start of a calendar year.
For each calendar year  thereafter,  CYTOGEN shall submit a Marketing  Plan with
respect to, and at least one year prior to, such  calendar  year  describing  in
reasonable  detail the marketing  activities for each such Licensed  Product for
approval  by the LLC.  The LLC's  approval  of any  Marketing  Plan shall not be
unreasonably  withheld.  Each  Marketing  Plan shall include an overall level of
anticipated product detailing,  promotion, marketing and sales efforts regarding
the period covered  thereby,  a resource  commitment on the part of CYTOGEN with
respect  thereto,  market and sales  forecasts and pricing  analysis,  a monthly
budget and,  with respect to  commercial  launch,  an  estimated  launch date of
product  marketing  and promotion  activities.  Each  Marketing  Plan shall also
include the general operating  guidelines and strategies for targeting,  pricing
and discounting Licensed Products to customers,  a detailed budget for marketing
and distribution  activities and a forecast product line contribution  statement
for the applicable calendar year.

     (b)  The LLC  may  from  time to time  review  with  CYTOGEN  such  matters
regarding marketing activities as it reasonably requests. CYTOGEN, Progenics and
the  LLC  agree  to  facilitate  communication  and  cooperation  between  their
respective   organizations  in  order  to  maximize  the  success  of  marketing
activities.

     (c) CYTOGEN shall  develop all written  sales,  promotion  and  advertising
materials  relating to the  commercialization  of Licensed Products in the North
American  Territory.  The general  form and content of such  materials  shall be
subject to annual approval of the LLC and general and specific implementation by
CYTOGEN. Ownership of all names, tradenames, trademarks, service marks and other
designations of Licensed Products (including any related registrations) shall be

                                       29
<PAGE>

vested in the LLC. In any given  country,  any given  Licensed  Product shall be
marketed under only one tradename, except as agreed to by the LLC.

     (d) The LLC shall be responsible for the cost of all advertising, sales and
promotion   materials,   market  research  and  Phase  IV  studies   ("Marketing
Materials")  reasonably  incurred  in  connection  with  a  previously  approved
Marketing Plan. The LLC will at all times own the Marketing Materials.

     (e) The LLC will have  responsibility  for manufacturing  finished packaged
product,  both for sale and for  promotional  samples.  The LLC will  also  have
responsibility for manufacturing clinical supplies for any Phase IV studies. The
LLC will  purchase  and pay for all raw  (active  and  inactive)  materials  and
packaging materials (collectively, "Manufacturing Materials") from third parties
necessary to  manufacture  product.  The LLC will at all times have title to the
Manufacturing  Materials,  work-in-process  product and final  packaged  product
(collectively,  "Inventory")  until sale. The LLC shall have  responsibility for
ensuring that  sufficient  Inventory is available to satisfy sales  requirements
pursuant to customer  orders and for procuring and paying for space to warehouse
Inventory.  The LLC shall  have  custodial  and  managerial  responsibility  for
Inventory.

     (f)  CYTOGEN  shall be  responsible  for  procuring  order  processing  and
distribution services for product. CYTOGEN shall have managerial  responsibility
for order processing, including processing customer orders and billing customers
for shipments in  satisfaction  of their orders,  and for product  distribution,
including shipping product in satisfaction of customer orders.

     (g) The LLC shall be entitled to inspect and audit CYTOGEN's and Progenics'
books and  records  pertaining  to  marketing  activities  relating  to Licensed
Products for legitimate  business  purposes under such terms as may be set forth
in the Marketing Agreement.

     9.5.  Negotiation  Rights.  (a) In the  event  that the LLC  determines  to
license, engage, or otherwise contract with or authorize a person other than the
LLC to engage in marketing  activities with respect to a Licensed Product in any
territory  other than in the North American  Territory,  the LLC shall so notify
CYTOGEN  and  negotiate  in good faith with  CYTOGEN  the terms of an  agreement
regarding marketing activities with respect to any such Licensed Product in such
territory. As a condition to any such negotiations, CYTOGEN shall demonstrate to
the LLC's reasonable  satisfaction CYTOGEN's capability to perform the marketing
activities desired by the LLC in the relevant territory. If CYTOGEN is unable to
satisfy  such  condition,  or if  CYTOGEN  does not  desire  to, or is unable to
negotiate any such agreement, or any such agreement is subsequently  terminated,
the LLC shall so notify  Progenics and negotiate in good faith with  Progenics a
marketing agreement as described above. As a condition to any such negotiations,
Progenics  shall  demonstrate to the LLC's  reasonable  satisfaction  Progenics'
capability  to  perform  the  marketing  activities  desired  by the  LLC in the
relevant  territory.  Any such  determination as to the capability of CYTOGEN or
Progenics shall take into  consideration the relevant party's ability to perform

                                       30

<PAGE>

the  necessary  sales and marketing  functions  based upon an assessment of such
party's  existing sales,  marketing and  distribution  capabilities  compared to
those of other companies  promoting similar products to similar market segments,
as well as such other factors as may be reasonably relevant.

     (b) If CYTOGEN  elects not to  exercise  the  marketing  rights it has been
granted under Section 9.1 hereof, or such rights are terminated pursuant to this
Agreement or the Marketing  Agreement,  then the LLC shall so notify  Progenics,
and Progenics  shall be entitled to assume,  on a prospective  basis,  CYTOGEN's
marketing rights hereunder and under the Marketing Agreement.  As a condition to
any such assumption,  Progenics must demonstrate to the reasonable  satisfaction
of the LLC Progenics' capability to perform the marketing activities required to
be performed  hereunder and under the Marketing  Agreement.  Such  determination
shall take into consideration Progenics' ability to perform the necessary sales,
marketing and  distribution  functions  based upon an assessment of its existing
sales and marketing  capabilities compared to those of other companies promoting
similar  products to similar market  segments,  as well as such other factors as
may be reasonably relevant.  If Progenics assumes such rights, such rights shall
be terminable  under the same  circumstances as such rights were terminable when
held by CYTOGEN.

     9.6.  Marketing  Compensation.  CYTOGEN and Progenics  shall be entitled to
compensation  for  marketing  activities  conducted  pursuant  hereto  or to the
Marketing Agreement [CONFIDENTIAL TREATMENT HAS BEEN REQUESTED]. For purposes of
this Section 9.6,  [CONFIDENTIAL  TREATMENT HAS BEEN  REQUESTED] as the case may
be, as more specifically described in the Marketing Agreement.

     9.7. Non-Transferability of Rights. The product marketing rights granted by
the LLC pursuant to this  Agreement  shall not be  transferable,  licensable  or
otherwise exercisable by any person or entity other than the party to which such
rights have been granted hereby.

     9.8.  Termination of Rights. The rights granted by the LLC to Progenics and
CYTOGEN  in  Section  9.1 and 9.3 hereof  shall be  subject  to  termination  as
follows:

               9.8.1.  Ownership  Change. In the event that either Progenics' or
          CYTOGEN's  Interest  shall  at any  time  be less  than  [CONFIDENTIAL
          TREATMENT HAS BEEN REQUESTED] of all  then-outstanding  Interests (any
          such party  being  referred  to herein as the  "Diluted  Party"),  the
          rights  granted to the  Diluted  Party  pursuant to Section 9.1 or 9.3
          hereof, as the case may be, shall immediately terminate.  In the event
          that the LLC  determines to issue  additional  ownership  interests to
          third-party  investors,  which  issuance  would result in  substantial
          dilution of Progenics's and CYTOGEN's ownership Interests, the parties
          hereto agree to negotiate in good faith the provisions of this Section
          9.8.1 as it  relates  to any  party  that  has not,  prior to any such
          additional issuance of ownership interests, become a Diluted Party.

                                       31

<PAGE>

               9.8.2.  Breach.  In the event that  either  Progenics  or CYTOGEN
          shall breach any of the material  representations or warranties or any
          material terms,  conditions or agreements  contained herein made or to
          be  kept,  observed  and  performed  by it,  then  each of the LLC and
          Progenics  (in the event of a breach by  CYTOGEN)  or CYTOGEN  (in the
          event of a  breach  by  Progenics),  at its sole  option  and  without
          prejudice to any of its other legal or equitable  rights and remedies,
          may, by giving the other  parties  hereto 60 days'  notice in writing,
          identifying with reasonable specificity the breach, and unless (in the
          case of a breach of any term,  condition  or  agreement)  the notified
          party within such 60-day period shall have cured the breach, terminate
          the  rights  granted  to  Progenics  or  CYTOGEN,  as the case may be,
          pursuant to Sections 9.1.

               9.8.3.  Diligence.  The LLC may terminate  the rights  granted to
          CYTOGEN pursuant to Section 9.1 hereof as to any Licensed Product (but
          only as to such Licensed Product) if CYTOGEN  [CONFIDENTIAL  TREATMENT
          HAS BEEN REQUESTED]

     9.9. Retention of Rights. The parties hereto acknowledge and agree that all
marketing  rights not  expressly  granted  by the LLC to  CYTOGEN  or  Progenics
pursuant to this Article IX,  including  without  limitation  product  marketing
rights outside of the North American Territory, are retained by the LLC. The LLC
shall be entitled to retain or dispose of (by license,  sublicense or otherwise)
any such rights in its sole  discretion,  and the proceeds,  if any, of any such
disposition shall inure solely to the LLC.

                                   ARTICLE X
                               DISPUTE RESOLUTION

     10.1. Escalation Procedure. Except as provided in Section 3.6(b) hereof and
except  for any  Deadlock  of the  Management  Committee  which is not  resolved
pursuant to Section  4.1(f) hereof  (including  related  buy/sell  provisions in
Section  4.1(g)  hereof),  all disputes,  controversies,  claims or  differences
between Progenics and CYTOGEN (any such event, a "Dispute")  arising out of this
Agreement,  its interpretation or performance by the Members of their respective
obligations hereunder, including any questions regarding the existence, validity
or termination  hereof,  shall be resolved as described below. The Dispute shall
first be  submitted  (the  "First  Notice of  Dispute")  to the Chief  Executive
Officer of each of the Members for review and  discussion.  Such  persons  shall
meet as soon as possible,  and in any event  within ten calendar  days after the
giving of the First Notice of Dispute, and endeavor in good faith to resolve the
matter.  If these officers do not reach agreement within ten calendar days after
they  meet,  or within 20  calendar  days  after the First  Notice of Dispute is
given,  or  otherwise  agree on another  method of resolving  the  dispute,  the
Dispute shall be resolved pursuant to Section 10.2 hereof.

     10.2.  Arbitration.  (a)  Either  Member  may  make a  demand  for  binding
arbitration  with  respect to any dispute  arising  hereunder by filing with the
other a demand in writing signed by an officer of the Member making such demand.

                                       32
<PAGE>

     (b) The Members may agree on one  arbitrator,  but in the event they cannot
agree,  there shall be three, one named in writing by each of the Members within
ten Business Days after demand for  arbitration is given,  and a third chosen by
the two appointed within ten Business Days after their  appointment.  If the two
arbitrators  appointed by the Members do not appoint a third  arbitrator  within
such period, the American Arbitration  Association ("AAA") in New York, New York
shall be retained to appoint a third  arbitrator  within ten Business Days after
the end of such period.  Should  either  Member refuse or neglect to join in the
appointment of the arbitrator(s) or to furnish the arbitrator(s) with any papers
or information demanded, the arbitrator(s) are empowered to proceed ex parte.

     (c)  Arbitration  shall  take  place in New York,  New York (or such  other
location as may be agreed  between  Progenics  and CYTOGEN) at a single  hearing
before the arbitrator(s) of the matter. The arbitrator(s) shall select such time
and place promptly after his/her (or their) appointment,  provided that the time
scheduled  for the hearing  shall not be later than 20  Business  Days after the
appointment  of the last  arbitrator(s).  The  arbitrator(s)  shall give written
notice  thereof to each Member at least ten  Business  Days prior to the date so
fixed. In the event a panel of three arbitrators is necessitated by the Members'
inability to agree upon a single  arbitrator,  such notice of the time and place
of the  hearing  shall  also  identify  the third  member of the  panel.  At the
hearing,  any relevant evidence may be offered by either Member,  and the formal
rules of evidence applicable to judicial proceedings shall not govern.  Evidence
may be  admitted  or  excluded  in the  discretion  of the  arbitrator(s).  Said
arbitrator(s)  shall hear and determine the matter and such determination may be
based on such factors and  consideration  as the  arbitrator(s)  deems  relevant
and/or appropriate. The arbitrator(s)' authority shall be limited to determining
the issue or question  presented  in each  instance  and shall not extend to any
other  aspect of this  Agreement  or the  parties'  relationship  generally.  In
addition,  the  arbitrator(s)  shall not require the LLC to pursue a  particular
research and development  program unless the general  elements thereof have been
approved  by the  Management  Committee.  The  arbitrator(s)  shall  execute and
acknowledge  a binding  decision  in writing  setting  forth the basis for their
decision in  reasonable  detail and cause a copy thereof to be delivered to each
of the Members within ten Business Days of the hearing date.

     (d) The  determination  of the panel  shall be by  majority  vote with each
arbitrator having a single vote. The decision rendered by the arbitrator (or the
majority,  if more than one) shall be final, and judgment may be entered upon it
in accordance with the applicable law in any court of competent jurisdiction.

     (e)  Prior to the  scheduled  hearing  date,  the  Members  shall  agree on
procedures  to be used in  connection  with the  arbitration.  To the extent the
Members  cannot agree upon  procedures,  the  arbitration  shall be conducted in
accordance with the Commercial  Arbitration  Rules of the AAA under the auspices
of the AAA.

     (f) The costs of such arbitration shall be borne by the Company;  provided,
however,  that if the arbitrator(s)  determines that one of the Members acted in
bad faith in submitting the dispute to  arbitration,  such Member shall bear all
costs and expenses  (including  the costs and  expenses of the other  Member) in
connection with the arbitration proceeding.

                                       33
<PAGE>
     10.3. Injunctive Relief.  Notwithstanding  anything herein to the contrary,
any Member may seek  interim or  provisional  relief in the form of a  temporary
restraining  order,  preliminary  injunction or other interim  equitable  relief
concerning any Dispute in a court of competent jurisdiction;  provided, however,
that, once the selection of the  arbitrator(s)  is complete,  the  continuation,
termination,  amendment or  modification  of the interim or  provisional  relief
shall be determined by the  arbitrator(s)  and, after an arbitration  hearing is
commenced,  the action, suit or proceeding  commenced in such court seeking such
interim or  provisional  relief  shall be dismissed  by the  stipulation  of all
Members. In the event that the Members fail to stipulate to the dismissal of the
action,  the  Members  agree that the  arbitrator(s)  may  submit a  stipulation
dismissing the action.  The  arbitrator(s) may conduct any hearings or order any
discovery  they deem  necessary  to properly  review the interim or  provisional
relief. This Section 10.3 shall be specifically enforceable by each Member.

                                   ARTICLE XI
                            MISCELLANEOUS PROVISIONS

     11.1.  Assurances.  Each Member shall  execute all  certificates  and other
documents and shall do all such filing, recording,  publishing and other acts as
the Management  Committee deems  appropriate to comply with the  requirements of
law for the  formation and operation of the Company and to comply with any laws,
rules and regulations  relating to the acquisition,  operation or holding of the
property of the Company.

     11.2. Disclaimer of Agency. This Agreement does not create any relationship
beyond the scope set forth herein,  and except as otherwise  expressly  provided
herein, this Agreement shall not constitute any Member the legal  representative
or agent of the  other,  nor shall any  Member  have the right or  authority  to
assume,  create  or incur any  liability  or  obligation,  express  or  implied,
against, in the name of or on behalf of any other Member of the Company.

     11.3.  Entire  Agreement;  Amendment.  This  Agreement  contains a complete
statement  of the  arrangements  among the Members  with  respect to the Company
supersedes all prior  agreements and  understandings  among them with respect to
the Company and may not be amended except by unanimous  written agreement of the
Members.

     11.4. Notices. Any notice or other communication under this Agreement shall
be in writing and shall be considered  given when delivered in person or sent by
facsimile  and  acknowledged  by a  responsible  person  at  the  office  of the
recipient,  one day after being sent by a major overnight courier,  or four days
after being mailed by registered mail, return receipt requested,  to the Members
at the addresses set forth below their names on the Schedule A hereto.

                                       34
<PAGE>

     11.5.  Counterparts.  The Members may execute this Agreement in two or more
counterparts,  which shall, in the aggregate, be signed by all the Members. Each
counterpart shall be deemed an original instrument as against any Member who has
signed it.

     11.6.  Governing Law. This Agreement  shall be governed by and construed in
accordance  with the law of the State of Delaware  applicable to agreements made
and to be performed in Delaware.

     11.7. Binding Effect. This Agreement shall be binding on all successors and
assigns of the  Members  and inure to the  benefit of the  respective  permitted
successors  and  assigns of the  Members,  except to the  extent of any  express
contrary provision in this Agreement.

     11.8.  Severability.  If any  provision  of this  Agreement  is  invalid or
unenforceable, the balance of this Agreement shall remain in effect and shall be
enforceable  to the maximum  extent  permitted by law,  and if any  provision is
inapplicable  to any  person  or  circumstance,  it  shall  nevertheless  remain
applicable to all other persons and circumstances.

     11.9.  Survival  of Rights,  Duties and  Obligations.  Termination  of this
Agreement for any cause shall not release either Member from any liability which
at the time of  termination  has already  accrued to the other Member  hereto or
which  thereafter  may accrue in respect  of any act or  omission  prior to such
termination,  nor  shall  any  such  termination  hereof  affect  in any way the
survival of and right,  duty or  obligation  of either Member which is expressly
stated elsewhere in this Agreement to survive termination hereof.

     11.10.  Captions and  Exhibits.  Titles or captions of Sections or Articles
contained in this Agreement are inserted only as a matter of convenience and for
reference  and in no way define,  limit,  extend or  describe  the scope of this
Agreement or the intent of any  provision  hereof.  All  Exhibits and  Schedules
attached  hereto  shall be  considered  a part hereof as though  fully set forth
herein.

     11.11. Specific Performance.  The Members acknowledge that monetary damages
may not be an adequate  remedy for  violations  of this  Agreement  and that any
Member may, in its sole  discretion,  through  arbitration  or  otherwise  under
Article X or, in  circumstances  where Article X hereof is not applicable,  in a
court of competent jurisdiction, apply for specific performance or injunctive or
other  relief as such  arbitrator  or court may deem just and proper in order to
enforce  this  Agreement  or to  prevent  violation  hereof  and,  to the extent
permitted by applicable  law, each Member waives any objection to the imposition
of such relief.

     11.12.  Assignability.  Except as otherwise provided in Section 6.1 hereof,
neither  this  Agreement  nor any  Interest,  including  the  right  to  receive
distributions,  shall be assignable by either Member without the written consent
of the other,  and any attempted  assignment  without such consent shall be null
and void.  This  Agreement  shall be binding upon the  successors  and permitted

                                       35
<PAGE>

assigns of the Members.  Any such successor or permitted assign shall be subject
to the same rights and  obligations  as the original  Member  hereunder.

     11.13.  Confidentiality.  (a) As used in this Section 11.13,  "Confidential
Information"  means all confidential  and proprietary  business,  technical,  or
financial information relating to the matters discussed herein.

     (b) In order to protect the  Confidential  Information of any Member hereto
(in such capacity,  the  "Disclosing  Member") that has become  available to any
other Member hereto (in such  capacity,  the  "Receiving  Member"),  each Member
agrees as follows:

     (i)  Each  Member  agrees  that  it will  make  no use of any  Confidential
Information  except  in  furtherance  of  the  purposes   contemplated  by  this
Agreement.

     (ii) Each Member agrees that it will not, without the prior written consent
of the other Member, disclose to any third party Confidential Information (which
for purposes of this Section  11.13(b)  shall  include the terms or existence of
this Agreement or of the PSMA/PSMP License  Agreement or the Services  Agreement
or other matters relating to the collaboration  contemplated hereby and thereby)
received in its capacity as Receiving  Member so long as such Member is a member
of the Company and for a period of five years thereafter.

     (iii) Notwithstanding the foregoing:

          (1)  Each Member may disclose Confidential Information to those of its
               representatives,  employees  and agents  ("Representatives")  who
               have a need to know such Confidential  Information in relation to
               the matters  discussed  herein and who are under  obligations  of
               confidentiality  and  non-use  consistent  with  those  set forth
               herein. Any unauthorized  disclosure of Confidential  Information
               by a Member's Representatives shall be a breach by such Member of
               this Section 11.13.

          (2)  Disclosure of Confidential Information is permitted to the extent
               that such  disclosure is required  pursuant to  applicable  laws,
               rules or  regulations  or government  requirement or court order,
               provided however, that the Receiving Member shall promptly notify
               the  Disclosing  Member in writing of the existence or imposition
               of  any  such   requirement  or  order  and  cooperate  with  the
               Disclosing  Member in seeking an appropriate  protective order or
               other  reliable  assurance  that  confidential  treatment will be
               accorded the Confidential Information.

                                       36
<PAGE>

     (c) The provisions governing  confidentiality and non-use contained in this
Section 11.13 shall not apply to any Confidential Information which:

               (i)  the  Receiving   Member  can  establish  was  known  to  the
                    Receiving  Member prior to disclosure under or in connection
                    with this Agreement by the Disclosing Member;

               (ii) was in the public domain or the subject of public  knowledge
                    at the time of disclosure  under or in connection  with this
                    Agreement;

               (iii)becomes  part of the public  domain or the subject of public
                    knowledge  through  no  breach by or act of  default  of the
                    Receiving Member;

               (iv) is obtained by the Receiving Member from a third party other
                    than in  breach  of a legal  or  contractual  obligation  of
                    confidentiality  owed by such third party to the  Disclosing
                    Member in  respect  thereof,  the  existence  of which  such
                    obligation  was  known  or  should  have  been  known by the
                    Receiving Member; or

               (v)  the  Receiving   Member  can  establish  was   independently
                    developed   by  it   without   reference   to   Confidential
                    Information received.

     (d)  Termination  of  this  Agreement  shall  not  affect  the  obligations
concerning confidentiality and non-use as set forth in this Section 11.13.


                                       37
<PAGE>


                  IN WITNESS  WHEREOF,  the  parties  hereto  have  signed  this
Agreement as of the date first above written.

                         PROGENICS PHARMACEUTICALS, INC.


                         By: /s/  Ronald Prentki
                            Name: Ronald Prentki
                            Title President


                         CYTOGEN CORPORATION


                         By:  /s/ Donald F. Crane, Jr.
                            Name: Donald F. Crane, Jr.
                            Title Vice President General Counsel and
                                  Corporate Secretary


                         PSMA DEVELOPMENT COMPANY LLC


                         By:  /s/ Ronald Prentki
                            Managing Representative


                         By:  /s/  Donald F. Crane, Jr.
                            Managing Representative


                                       38

                                                                    Exhibit 10.3



                           PSMA/PSMP LICENSE AGREEMENT


                               Dated June 15, 1999


                                  by and among

                        PROGENICS PHARMACEUTICALS, INC.,

                               CYTOGEN CORPORATION

                                       and


                          PSMA Development Company LLC


<PAGE>

                                TABLE OF CONTENTS

                                                                        Page

1.     DEFINITIONS.......................................................2

1.1.  Affiliate..........................................................2
1.2.  Commercial Sale....................................................2
1.3.  Contract Period....................................................2
1.4.  CYTOGEN............................................................2
1.5.  CYTOGEN License....................................................2
1.6.  CYTOGEN Technical Information......................................2
1.7.  Effective Date.....................................................3
1.8.  FDA................................................................3
1.9.  Field..............................................................3
1.10.  Field Antibody....................................................3
1.11.  Field Immunogen...................................................3
1.12.  Licensed CYTOGEN Patent...........................................3
1.13.  Licensed CYTOGEN Product..........................................3
1.14.  Licensed Patent...................................................4
1.15.  Licensed Product..................................................4
1.16.  Licensed Progenics Patent.........................................4
1.17.  Licensed Progenics Product........................................4
1.18.  Licensed Technical Information....................................4
1.19.  Licenses..........................................................4
1.20.  LLC...............................................................4
1.21.  LLC Agreement.....................................................4
1.22.  Major Market......................................................4
1.23.  Manufacturing Rights..............................................4
1.24.  MoAb 7E11.........................................................4
1.25.  North American Territory..........................................5
1.26.  NWB...............................................................5
1.27.  NWC...............................................................5
1.28.  NWC Agreement.....................................................5
1.29.  Patent............................................................5
1.30.  Prime License.....................................................5
1.31.  Progenics.........................................................5
1.32.  Progenics License.................................................5
1.33.  Progenics Technical Information...................................5
1.34.  Prostagen.........................................................5
1.35.  Prostagen Agreement...............................................6
1.36.  PSMA..............................................................6
1.37.  PSMP..............................................................6
1.38.  Regulatory Authority..............................................6
1.39.  Services Agreement................................................6
1.40.  SKICR.............................................................6
1.41.  SKICR Agreement...................................................6

                                       i
<PAGE>

1.42.  SKICR License.....................................................6
1.43.  Technical Information.............................................6
1.44.  Territory.........................................................6
1.45     [CONFIDENTIAL TREATMENT HAS BEEN REQUESTED]

2.     REPRESENTATIONS AND WARRANTIES....................................6

2.1.  By Progenics.......................................................6
2.2.  By CYTOGEN.........................................................7

3.     LICENSES.........................................................10

3.1.  Grant by Progenics................................................10
3.2.  Grant by CYTOGEN..................................................10
3.3.  Licensing of Additional Patents and Technical Information.........11
3.4.  Sublicenses.......................................................12
3.5.  Guarantee of Performance of Sublicensee...........................12
3.6.  Cure of Breach by Sublicensee.....................................12
3.7.  [CONFIDENTIAL TREATMENT HAS BEEN REQUESTED]
3.8.  [CONFIDENTIAL TREATMENT HAS BEEN REQUESTED]
3.9.  Reservation of Rights.............................................12
3.10.  No Other Rights..................................................13
3.11.  Competition Not Prohibited.......................................13

4.     CERTAIN COVENANTS................................................13

4.1.  Diligence.........................................................13
4.2.  No Waivers or Grant of Further Rights.............................13
4.3.  Summary Reports...................................................14
4.4.  Breach of SKICR Agreement.........................................14
4.5.  Acquiring Other Rights in the Field...............................14
4.6.  Notices under Prime Licenses......................................14
4.7.  Compliance with Terms of Prime Licenses; Assignment...............14
4.8.  [CONFIDENTIAL TREATMENT HAS BEEN REQUESTED]

5.     ROYALTIES AND OTHER PAYMENTS.....................................15

5.1.  Amounts Payable with Respect to the Progenics License.............15
5.2.  Amounts Payable with Respect to the CYTOGEN License...............15
5.3.  Allocation of Royalties...........................................15

6.     PATENT PROSECUTION AND MAINTENANCE, ETC..........................16

6.1.  Prosecution and Maintenance.......................................16
6.2.  Disclosure Regarding Patent Activities............................16

7.     REPORTS AND ROYALTY PAYMENTS; BOOKS AND RECORDS..................17

7.1.  Reports...........................................................17
7.2.  Royalty Payments..................................................17
7.3.  Calculation of Royalties and Other Payments.......................17
7.4.  Currency Control Restrictions.....................................17
7.5.  Books and Records.................................................17


                                       ii

<PAGE>
8.     TAXATION OF PAYMENTS.............................................18


9.     PRODUCT LIABILITY DISCLAIMERS....................................18

9.1.  Product Liability Disclaimer by Progenics.........................18
9.2.  Product Liability Disclaimer by CYTOGEN...........................18
9.3.  Product Liability Disclaimer by the LLC...........................18

10.    INDEMNIFICATION AND INFRINGEMENT.................................19

10.1.  Indemnification..................................................19
10.2.  Third Party Infringement of Licensed Patent Rights...............19

11.    TERM AND TERMINATION.............................................20

11.1.  Term.............................................................20
11.2.  Termination......................................................20
11.3.  Accrued Rights and Obligations...................................22

12.    EFFECT OF TERMINATION ON SUBLICENSEE.............................22

13.    EXPORT LICENSES..................................................22

14.    MISCELLANEOUS PROVISIONS.........................................22

14.1.  Assignability....................................................22
14.2.  Notices..........................................................22
14.3.  Independent Contractors..........................................23
14.4.  Counterparts.....................................................23
14.5.  Entire Understanding.............................................23
14.6.  Headings.........................................................23
14.7.  No Implied Rights................................................23
14.8.  No Waiver........................................................23
14.9.  Publicity........................................................23
14.10.  Promotion and Advertising.......................................24
14.11.  Arbitration.....................................................24
14.12.  Confidentiality.................................................24
14.13.  No Third Party Beneficiaries............................... ....25
14.14.  Governing Law...................................................25
14.15.  SKICR Agreement.................................................26
14.16.  Limitation on Liability.........................................26

                                      iii


<PAGE>

                           PSMA/PSMP LICENSE AGREEMENT

                  THIS PSMA/PSMP  LICENSE  AGREEMENT,  dated June 15, 1999 (this
"Agreement"),  is made by and among Progenics Pharmaceuticals,  Inc., a Delaware
corporation  having  its  place  of  business  at 777 Old Saw Mill  River  Road,
Tarrytown, NY 10591 ("Progenics"),  CYTOGEN Corporation,  a Delaware corporation
having its place of business at 600 College Road East,  CN 5308,  Princeton,  NJ
08540  ("CYTOGEN"),  and  PSMA  Development  Company  LLC,  a  Delaware  limited
liability  company  having its  principal  place of business at 777 Old Saw Mill
River Road, Tarrytown, NY 10591 (the "LLC").

                  WHEREAS,  CYTOGEN has acquired certain  intellectual  property
rights,  including  patent  rights,  relating  to PSMA and PSMP (as  hereinafter
defined), and may in the future acquire additional intellectual property rights,
including patent rights, relating to therapeutics based on PSMA and/or PSMP;

                  WHEREAS,   Progenics  has  certain   expertise  in  developing
immunotherapeutics based on novel vaccine and antibody technology and may in the
future acquire intellectual property rights,  including patents rights, relating
to immunotherapeutics based on PSMA and/or PSMP;

                  WHEREAS,   Progenics   and   CYTOGEN   wish  to   establish  a
collaboration   to   pursue   the   development   and    commercialization    of
immunotherapeutic  products or services  based on PSMA and/or PSMP and, in order
to implement such collaboration, Progenics and CYTOGEN have caused the LLC to be
organized  and have each  become the owner of 50% of the  outstanding  ownership
interests thereof;

                  WHEREAS,  in  connection  with  the  organization  of the LLC,
Progenics,  CYTOGEN and the LLC have  entered into a limited  liability  company
agreement providing for the management of the LLC and the rights and obligations
of the parties thereto;

                  WHEREAS,   in  furtherance  of  the  collaboration,   each  of
Progenics  and  CYTOGEN  desires  to grant  rights  to the LLC with  respect  to
intellectual  property  rights now owned or  hereafter  acquired by Progenics or
CYTOGEN in the Field (as hereinafter  defined),  and Progenics,  CYTOGEN and the
LLC wish to provide for certain other matters  related to the  collaboration  in
the Field, as set forth below;

                  WHEREAS,  CYTOGEN previously granted to Prostagen Corporation,
a Delaware  corporation  ("Prostagen"),  an exclusive  license to certain rights
related to PSMA  pursuant to a PSMA  Therapeutics  Sublicense  Agreement,  dated
December  9,  1996,  by  and  between  CYTOGEN  and  Prostagen  (the  "Prostagen
Agreement");

                  WHEREAS,  Prostagen  previously granted to Northwest Clinicals
LLC, a Washington limited liability company ("NWC"), an exclusive  sublicense to
produce,  process or otherwise  manufacture and sell PSMA and PSMP pursuant to a
PSMA  Production  Sublicense  Agreement,  dated as of July 16,  1997  (the  "NWC
Agreement");

                  WHEREAS,  prior to the date hereof and in order to  facilitate
the  above-referenced  collaboration  among  the  parties  hereto,  CYTOGEN  has


<PAGE>
acquired 100% of the outstanding equity interests in Prostagen,  and CYTOGEN and
Prostagen have terminated the Prostagen Agreement to the extent of the Field;

                  WHEREAS,  CYTOGEN has agreed with  Progenics  to cause the NWC
Agreement  to be  terminated  and to acquire for the LLC, at no cost to the LLC,
exclusive  manufacturing rights in the Field for PSMA and PSMP, and to indemnify
and hold the LLC harmless for any cost, expense,  damage or liability whatsoever
related  to  CYTOGEN's  inability  to  grant  to the LLC as of the  date  hereof
manufacturing rights in the Field to PSMA and PSMP;

                  WHEREAS,  in order to  pursue  the  research  and  development
programs  contemplated by the above-referenced  collaboration  between Progenics
and CYTOGEN,  simultaneously  with the execution and delivery of this  Agreement
Progenics,  CYTOGEN  and the LLC are  entering  into a Services  Agreement  (the
"Service  Agreement") pursuant to which Progenics is agreeing to perform certain
research and development services.

                   NOW,  THEREFORE,  in consideration of the foregoing  premises
and the mutual covenants contained herein, the parties hereto agree as follows:

     1.  DEFINITIONS.  For the purposes of this Agreement,  the following terms,
whether used in the singular or plural, shall have the following meanings:

     1.1.  Affiliate.  The term "Affiliate" shall mean any person,  corporation,
company, partnership, joint venture and/or firm which controls, is controlled by
or is under  common  control  with, a party.  For  purposes of this  definition,
"control" shall mean (a) in the case of corporate  entities,  direct or indirect
ownership of at least 50% of the stock or participating  shares entitled to vote
for the election of directors,  and (b) in the case of  non-corporate  entities,
direct or indirect  ownership  of at least 50% of the equity  interest  with the
power to direct the management and policies of such non-corporate entity.

     1.2.  Commercial Sale. The term "Commercial Sale" shall mean the commercial
sale of a Licensed  Product to an unrelated third party.  The sale of a Licensed
Product  distributed or used for clinical trials or  experimental  purposes only
shall not be considered a Commercial Sale.

     1.3.  Contract  Period.  The term  "Contract  Period" shall mean the period
beginning on the Effective  Date and ending on the date on which this  Agreement
shall  expire or  terminate  in  accordance  with the  provisions  of Section 11
hereof.

     1.4.  CYTOGEN.  The term "CYTOGEN"  shall have the meaning set forth in the
recitals of this Agreement.

     1.5.  CYTOGEN  License.  The term "CYTOGEN  License" shall mean the license
granted by CYTOGEN to the LLC pursuant to Section 3.2 of this Agreement.

     1.6.   CYTOGEN   Technical   Information.   The  term  "CYTOGEN   Technical
Information"  shall mean Technical  Information  to the extent,  but only to the
extent,  used or useful in the Field in which CYTOGEN has or acquires during the
Contract  Period a  licensable  right;  provided,  however,  that any  Technical
Information  used or  useful  in the  Field in  which  CYTOGEN  currently  has a

                                       2
<PAGE>

licensable right but which is not disclosed on Annex A hereto, and any Technical
Information  used or useful in the Field in which CYTOGEN  acquires a licensable
right  after  the date  hereof,  shall not be  deemed  to be  CYTOGEN  Technical
Information unless and until Progenics shall have expressly consented in writing
pursuant to Section 3.3 hereof.

     1.7.  Effective Date. The term "Effective Date" shall mean the date of this
Agreement, as set forth on the first page hereof.

     1.8. FDA. The term "FDA" shall mean the U.S. Food and Drug Administration.

     1.9. Field. The term "Field" shall mean:

     (a) any and all means of  developing,  making,  having made,  distributing,
using, offering for sale, selling, having sold, importing or exporting any Field
Immunogen  and/or any vaccine  incorporating a Field Immunogen as a therapeutic,
but excluding  vaccines for prostate  cancer that are antigen  presenting  cells
isolated from a patient's blood, bone marrow or spleen and pulsed ex vivo with a
Field Immunogen for return to the patient; and

     (b) any and all means of  developing,  making,  having made,  distributing,
using, offering for sale, selling, having sold, importing or exporting any Field
Antibody as a therapeutic.

     1.10.  Field Antibody.  The term "Field Antibody" shall mean a product that
incorporates a peptide that includes a complementarity  determining region of an
antibody   recognizing  one  or  more  Field  Immunogens,   including,   without
limitation,   antibodies,  antibody  fragments,  antibody  derivatives  such  as
humanized  antibodies and single chain antibodies,  and conjugates of any of the
foregoing, but excluding MoAb 7E11.

     1.11. Field Immunogen.  The term "Field Immunogen" shall mean any immunogen
that derives its immunogenicity  wholly or in significant part from PSMA or PSMP
or mimetopes thereof, or any combination of such immunogens.

     1.12.  Licensed  CYTOGEN Patent.  The term "Licensed  CYTOGEN Patent" shall
mean any Patent in which  CYTOGEN has or acquires  during the Contract  Period a
licensable right, to the extent, but only to the extent, any such Patent is used
or useful in the Field; provided, however, that any Patent used or useful in the
Field in  which  CYTOGEN  currently  has a  licensable  right  but  which is not
disclosed on Annex A hereto, and any Patent used or useful in the Field in which
CYTOGEN acquires a licensable  right after the date hereof,  shall not be deemed
to be a Licensed  CYTOGEN Patent unless and until Progenics shall have expressly
consented in writing pursuant to Section 3.3 hereof.  The term "Licensed CYTOGEN
Patent" shall include the rights  (including  Patent rights)  granted to CYTOGEN
pursuant to the SKICR Agreement and Wright Agreement as well as the other Patent
rights listed on Annex A hereto.

     1.13.  Licensed CYTOGEN Product.  The term "Licensed CYTOGEN Product" shall
mean any  product,  apparatus,  method or service the  manufacture,  use,  sale,
provision or practice of which would, in the absence of a license,  infringe one
or more claims of a Licensed CYTOGEN Patent.


                                       3
<PAGE>

     1.14.  Licensed Patent.  The term "Licensed Patent" shall mean any Licensed
Progenics Patent or Licensed CYTOGEN Patent.

     1.15. Licensed Product. The term "Licensed Product" shall mean any Licensed
Progenics Product or Licensed CYTOGEN Product.

     1.16. Licensed Progenics Patent. The term "Licensed Progenics Patent" shall
mean any Patent in which  Progenics has or acquires during the Contract Period a
licensable right, to the extent, but only to the extent, any such Patent is used
or useful in the Field; provided, however, that any Patent used or useful in the
Field in which  Progenics  currently  has a  licensable  right  but which is not
disclosed on Annex B hereto, and any Patent used or useful in the Field in which
Progenics acquires a licensable right after the date hereof, shall not be deemed
to be a Licensed  Progenics Patent unless and until CYTOGEN shall have expressly
consented in writing pursuant to Section 3.3 hereof.

     1.17.  Licensed  Progenics Product.  The term "Licensed  Progenics Product"
shall mean any product, apparatus, method or service the manufacture, use, sale,
provision  or practice  of which by the LLC would,  in the absence of a license,
infringe one or more claims of a Licensed Progenics Patent.

     1.18.  Licensed  Technical   Information.   The  term  "Licensed  Technical
Information"  shall mean the  Progenics  Technical  Information  and the CYTOGEN
Technical Information.

     1.19.  Licenses.  The term "Licenses" shall mean the Progenics  License and
the CYTOGEN License.

     1.20.  LLC. The term "LLC" shall have the meaning set forth in the recitals
of this Agreement.

     1.21.  LLC  Agreement.  The term "LLC  Agreement"  shall  mean the  Limited
Liability  Company  Agreement,  dated as of even  date  herewith,  by and  among
Progenics, CYTOGEN and the LLC, and any amendments thereto.

     1.22.  Major Market.  The term "Major  Market" shall mean any of the United
States, United Kingdom, France, Germany, Italy, Spain, Japan or Canada.

     1.23.  Manufacturing Rights. The term "Manufacturing Rights" shall have the
meaning set forth in Section 4.8 hereof.

     1.24.  MoAb 7E11. The term "MoAb 7Ell" shall mean that certain  antibody to
PSMA known as MoAb  7E11-C5,  which such  antibody  is claimed in United  States
Patent No  5,162,504,  granted  November  10,  1992,  and  entitled  "Monoclonal
Antibodies to a New Antigenic Marker in Epithelial  Prostatic Cells and Serum of
Prostate Cancer  Patients." The term "MoAb 7E11" includes all subclones  claimed
in such Patent.

                                       4
<PAGE>
     1.25. North American  Territory.  The term "North American Territory" shall
mean the United  States of America and Canada and their  respective  territories
and possessions.

     1.26.  NWB. The term "NWB" shall have the meaning set forth in the recitals
of this Agreement.

     1.27.  NWC. The term "NWC" shall have the meaning set forth in the recitals
of this Agreement.

     1.28. NWC Agreement.  The term "NWC  Agreement"  shall have the meaning set
forth in the recitals of this Agreement.

     1.29.  Patent.  The term "Patent"  shall mean (i) unexpired  letters patent
(including  inventor's  certificates) which have not lapsed or been held invalid
or unenforceable  by a court or  administrative  body of competent  jurisdiction
from  which no appeal can be taken or has been taken  within the  required  time
period,   including,   without   limitation,   any   substitution,    extension,
registration,  confirmation, reissue, reexamination,  renewal or any like filing
thereof, and (ii) pending applications for letters patent that have not been the
subject of a rejection notice from which an appeal cannot be taken or in respect
of which the  applicable  period  of  appeal  has  expired,  including,  without
limitation, any continuation,  division or continuation-in-part  thereof and any
provisional applications.

     1.30.  Prime  License.  The term "Prime  License"  shall mean any  license,
including, without limitation, the SKICR Agreement,  pursuant to which Progenics
or CYTOGEN has acquired, or acquires in the future, intellectual property rights
licensed to the LLC hereunder.

     1.31.  Progenics.  The term "Progenics" shall have the meaning set forth in
the recitals of this Agreement.

     1.32.  Progenics  License.  The term  "Progenics  License"  shall  mean the
license  granted  by  Progenics  to the  LLC  pursuant  to  Section  3.1 of this
Agreement.

     1.33.  Progenics  Technical  Information.  The  term  "Progenics  Technical
Information"  shall mean Technical  Information  to the extent,  but only to the
extent,  used or useful in the Field in which  Progenics has or acquires  during
the Contract Period a licensable right;  provided,  however,  that any Technical
Information  used or  useful  in the Field in which  Progenics  currently  has a
licensable right but which is not disclosed on Annex B hereto, and any Technical
Information used or useful in the Field in which Progenics acquires a licensable
right  after the date  hereof,  shall not be  deemed to be  Progenics  Technical
Information  unless and until CYTOGEN shall have expressly  consented in writing
pursuant to Section 3.3 hereof.

     1.34.  Prostagen.  The term "Prostagen" shall have the meaning set forth in
the recitals of this Agreement.

                                       5
<PAGE>
     1.35.  Prostagen Agreement.  The term "Prostagen  Agreement" shall have the
meaning set forth in the recitals of this Agreement.

     1.36. PSMA. The term "PSMA" shall mean prostate  specific  membrane antigen
as described in Cancer Research,  53:227-230 (1993) and as described in the U.S.
Patent   Application   Serial  Nos.   08/973,337   and   08/394,152,   including
continuations and continuations-in-part,  allelic variations thereof and nucleic
acids encoding the same.

     1.37. PSMP. The term "PSMP" shall mean prostate specific membrane peptides,
which  include any peptide  sequence  appearing  in a PSMA protein and unique to
PSMA proteins, and nucleic acids encoding the same.

     1.38. Regulatory Authority.  The term "Regulatory Authority" shall mean the
applicable governmental authority (which, in the United States, is the FDA) that
is  responsible  for  approval  for  manufacturing,  marketing  or  importing  a
therapeutic agent in a particular country for human use.

     1.39.  Services  Agreement.  The term "Services  Agreement"  shall have the
meaning set forth in the recitals of this Agreement.

     1.40. SKICR. The term "SKICR" shall mean the Sloan-Kettering  Institute for
Cancer Research, a New York membership corporation having its principal place of
business at 1275 York Avenue, New York, New York 10021.

     1.41. SKICR Agreement. The term "SKICR Agreement" shall mean the Option and
License Agreement,  effective July 1, 1993, by and between SKICR and Cytogen, as
amended by amendment no. 1 thereto effective as of November 22, 1993.

     1.42.  SKICR  License.  The term  "SKICR  License"  shall mean the  license
granted to Cytogen pursuant to the SKICR Agreement.

     1.43. Technical  Information.  The term "Technical  Information" shall mean
unpublished  research  and  development   information,   unpatented  inventions,
formulae, processes, know-how, trade secrets and technical data.

     1.44. Territory. The term "Territory" shall mean the entire world.

     1.45. [CONFIDENTIAL TREATMENT HAS BEEN REQUESTED]

     2. REPRESENTATIONS AND WARRANTIES.
        -------------------------------

     2.1. By Progenics. Progenics represents and warrants to CYTOGEN and the LLC
as follows:

     2.1.1.  Due  Organization.  Progenics is a corporation  duly  organized and
validly existing under the laws of the State of Delaware.

                                       6
<PAGE>
     2.1.2. Power to Act.  Progenics has all necessary  corporate power to enter
into and  perform  its  obligations  under  this  Agreement  and has  taken  all
necessary  corporate  action  under  the laws of the State of  Delaware  and its
certificate  of  incorporation  and by-laws to authorize  the  execution of, and
performance of its obligations  under,  this  Agreement.  Progenics has the full
right,  power and authority to grant all of the right, title and interest in the
license granted by Progenics under Section 3 hereof.

     2.1.3.  No Default.  Progenics is not in default under, or in conflict with
respect to, its certificate of incorporation or by-laws or any term or provision
of any  agreement,  mortgage or indenture to which it is a party or by which any
of its  properties  are bound or any statute,  rule,  order,  writ,  injunction,
decree  or  regulation  applicable  to it or  any of its  properties  that  will
preclude the performance of its obligations under this Agreement in any material
respect.

     2.1.4. No Material  Contracts.  Progenics is not subject to any contract or
agreement that will preclude or otherwise  conflict with the  performance of its
obligations under this Agreement in any material respect.

     2.1.5. No Conflicts.  Neither the execution nor delivery of this Agreement,
the consummation of the transactions  herein contemplated nor the fulfillment of
or compliance with the terms and provisions hereof will (i) require the consent,
approval or  authorization  of, or notice,  declaration,  filing or registration
with, any  governmental  or regulatory  authority,  or violate any provisions of
law,  administrative  regulation or court decree applicable to Progenics or (ii)
conflict with, result in a breach of any of the terms,  conditions or provisions
of or constitute a default under the certificate of  incorporation or by-laws of
Progenics or of any  agreement or  instrument to which it is a party or by which
any of its property is bound.

     2.1.6. Execution and Delivery; Enforceability. This Agreement has been duly
executed and delivered and constitutes the legal,  valid and binding  obligation
of  Progenics,  enforceable  against  it in  accordance  with the terms  hereof,
subject, as to enforcement,  to bankruptcy,  fraudulent conveyance,  insolvency,
reorganization,  moratorium  and other laws relating to or affecting  creditors'
rights generally and by general equitable principles.

     2.1.7. Patents in the Field. To Progenics's  knowledge,  on the date hereof
Progenics  does not have a licensable  right to any Patent used or useful in the
Field except as disclosed on Annex B hereto.

     2.2. By CYTOGEN.  CYTOGEN  represents and warrants to Progenics and the LLC
as follows:

     2.2.1.  Due  Organization.  CYTOGEN is a  corporation  duly  organized  and
validly existing under the laws of the State of Delaware.

     2.2.2.  Power To Act.  CYTOGEN has all necessary  corporate  power to enter
into and  perform  its  obligations  under  this  Agreement  and has  taken  all
necessary  corporate  action  under  the laws of the State of  Delaware  and its
certificate  of  incorporation  and by-laws to authorize  the  execution of, and
performance  of its  obligations  under,  this  Agreement.  CYTOGEN has the full
right,  power and authority to grant all of the right, title and interest in the
licenses granted,  or contingent  licenses that may be granted, by CYTOGEN under
Section 3 hereof.

                                       7
<PAGE>

     2.2.3.  No Default.  CYTOGEN is not in default  under,  or in conflict with
respect to, its certificate of incorporation or by-laws or any term or provision
of any  agreement,  mortgage or indenture to which it is a party or by which any
of its  properties  are bound or any statute,  rule,  order,  writ,  injunction,
decree  or  regulation  applicable  to it or  any of its  properties  that  will
preclude the performance of its obligations under this Agreement in any material
respect.

     2.2.4.  No Material  Contracts.  CYTOGEN is not subject to any  contract or
agreement that will preclude or otherwise  conflict with the  performance of its
obligations under this Agreement in any material respect.

     2.2.5. No Conflicts.  Neither the execution nor delivery of this Agreement,
the consummation of the transactions  herein contemplated nor the fulfillment of
or compliance with the terms and provisions hereof will (i) require the consent,
approval or  authorization  of, or notice,  declaration,  filing or registration
with, any  governmental  or regulatory  authority,  or violate any provisions of
law,  administrative  regulation  or court decree  applicable to CYTOGEN or (ii)
conflict with, result in a breach of any of the terms,  conditions or provisions
of or constitute a default under the certificate of  incorporation or by-laws of
CYTOGEN or of any agreement or instrument to which it is a party or by which any
of its property is bound.

     2.2.6. Execution and Delivery; Enforceability. This Agreement has been duly
executed and delivered and constitutes the legal,  valid and binding  obligation
of CYTOGEN, enforceable against it in accordance with the terms hereof, subject,
as  to   enforcement,   to  bankruptcy,   fraudulent   conveyance,   insolvency,
reorganization,  moratorium  and other laws relating to or affecting  creditors'
rights generally and by general equitable principles.

     2.2.7. SKICR and Wright Agreements. (a) Attached as Exhibit 1 is a true and
complete  copy of the SKICR  Agreement  and  attached as Exhibit 2 is a true and
complete copy of the [CONFIDENTIAL  TREATMENT HAS BEEN REQUESTED] Agreement.  No
provision  of the  SKICR  Agreement  or the  [CONFIDENTIAL  TREATMENT  HAS  BEEN
REQUESTED]  Agreement  has been amended,  modified or waived.  All of the rights
granted  under the SKICR  Agreement  and the  [CONFIDENTIAL  TREATMENT  HAS BEEN
REQUESTED]  Agreement  to CYTOGEN are valid and  enforceable,  and neither  this
Agreement nor the LLC Agreement  contravene any provision of such  agreements or
give rise to a termination  right  thereunder.  The option  described in Section
III.A.  of the SKICR  Agreement  was duly and validly  exercised by CYTOGEN in a
timely manner,  the license issue fee described in Section  III.B.  of the SKICR
Agreement  was paid by CYTOGEN in  accordance  with such section and the license
described  in Section  III.C.  of the SKICR  Agreement  was  thereupon  duly and
validly issued.

     (b) To CYTOGEN's knowledge:  (i) the representations and warranties made by
SKICR in the SKICR Agreement were true in all material  respects when made; (ii)
there  has   occurred  no  act  or  failure  to  act  that  would   render  such
representations  untrue in any  material  respect  if made on and as of the date
hereof;  and (iii)  there  exists no breach or  anticipatory  breach by SKICR or
[CONFIDENTIAL  TREATMENT HAS BEEN REQUESTED] of any of its material  obligations
under the SKICR  Agreement or the  [CONFIDENTIAL  TREATMENT HAS BEEN  REQUESTED]
Agreement,  respectively.  Each of the  SKICR  Agreement  and the  [CONFIDENTIAL
TREATMENT HAS BEEN REQUESTED] Agreement is in full force and effect, and CYTOGEN
has complied in all material  respects with its  obligations  thereunder.  There

                                       8
<PAGE>

does not exist any default by CYTOGEN under such agreements  that,  after notice
or the lapse of time or both,  would  constitute a material  event of default or
give rise to a right of  termination  thereunder.  CYTOGEN has neither given nor
received any notice of termination or breach under such agreements. In the event
of any  misrepresentation  or  breach  of  warranty  by SKICR  under  the  SKICR
Agreement, CYTOGEN will cooperate with all reasonable requests of the Management
Committee  of the LLC  regarding  the  assertion of any claim or cause of action
against SKICR for such misrepresentation or breach of warranty;  provided,  that
the LLC shall bear any and all costs,  expenses,  liabilities  or obligations of
CYTOGEN in connection therewith or arising therefrom.

     2.2.8. No Litigation,  Claims or Conflicts.  (a) There is no action,  suit,
claim or  proceeding  pending or  threatened  against  CYTOGEN or, to  CYTOGEN'S
knowledge,  SKICR or [CONFIDENTIAL  TREATMENT HAS BEEN REQUESTED]with respect to
any of the Licensed CYTOGEN Patents or CYTOGEN Technical Information,  either at
law or in  equity,  before  any court or  administrative  agency  or before  any
governmental department,  commission,  board, bureau, agency or instrumentality,
whether United States or foreign, relating to validity, infringement,  ownership
or  otherwise,  and  neither  CYTOGEN  nor,  to  CYTOGEN's  knowledge,  SKICR or
[CONFIDENTIAL  TREATMENT  HAS BEEN  REQUESTED]  has received any notice that any
person  may bring  such a claim,  and  CYTOGEN  has no belief  that any basis or
grounds exists for any such actions, suits or claims.

     (b) [CONFIDENTIAL TREATMENT HAS BEEN REQUESTED]

     (c) There are no  proceedings  or claims  pending in which  CYTOGEN  or, to
CYTOGEN's  knowledge,  SKICR or  [CONFIDENTIAL  TREATMENT  HAS  BEEN  REQUESTED]
alleges that any person is infringing upon, or otherwise  violating,  any of the
Licensed  CYTOGEN  Patents  or  CYTOGEN  Technical  Information,   nor  are  any
proceedings  threatened  by  CYTOGEN  or,  to  CYTOGEN's  knowledge,   SKICR  or
[CONFIDENTIAL  TREATMENT  HAS BEEN  REQUESTED]  alleging  any such  violation or
infringement.

     2.2.9.  Subsisting Rights. The Licensed CYTOGEN Patents in existence on the
Effective  Date are in full force and effect,  have been  maintained to date and
are not invalid or  unenforceable,  in whole or in part. No act has been done or
omitted to be done which had or could have the effect of impairing or dedicating
to the public,  or  entitling  any U.S. or foreign  government  authority or any
other  person to  cancel,  forfeit,  modify  or  consider  abandoned  any of the
Licensed  CYTOGEN  Patents,  or give any person any rights with respect thereto.
All of  CYTOGEN's  rights  under  the  SKICR  Agreement  and  the  [CONFIDENTIAL
TREATMENT HAS BEEN REQUESTED]  Agreement,  and CYTOGEN's ownership rights in the
Patents listed in paragraph 2 of Annex A hereof, are valid, enforceable and free
of defects.

     2.2.10.  No Prior  Transfer.  (a) CYTOGEN has not  previously  sublicensed,
assigned,  transferred,  conveyed or otherwise  encumbered its right,  title and
interest in any of the Licensed CYTOGEN Patents or CYTOGEN Technical Information
other than pursuant to the Prostagen Agreement.  A true and complete copy of the
NWC Agreement is attached hereto as Exhibit 2.

     (b) The  Prostagen  Agreement  has been  terminated  in its  entirety  with
respect to the Field, and except for the Manufacturing  Rights, no rights in the

                                       9
<PAGE>
Field remain  outstanding  under the  Prostagen  Agreement and all rights in the
Field to Patents and Technical  Information  granted  thereunder (other than the
Manufacturing Rights) have been reacquired by CYTOGEN.

     2.2.11. Exclusive Owner, etc. CYTOGEN is the sole and exclusive licensee of
the rights licensed to CYTOGEN under the SKICR  Agreement and the  [CONFIDENTIAL
TREATMENT HAS BEEN REQUESTED]  Agreement and of the rights to the Patents listed
in  paragraph 2 of Annex A hereof,  all of which are owned free and clear of any
liens,  charges and  encumbrances,  and no other  person,  corporation  or other
private or  governmental  entity or  subdivision  thereof  has or shall have any
claims  of  ownership  whatsoever  with  respect  to such  rights.  There are no
judgments or settlements against or owed by CYTOGEN relating to such rights.

     2.2.12.  Confidentiality;  Effective  Waivers.  (a) Neither CYTOGEN nor, to
CYTOGEN's  knowledge,  SKICR or [CONFIDENTIAL  TREATMENT HAS BEEN REQUESTED] has
divulged,  furnished  to or made  accessible  to any  person  any trade  secrets
included  in the  Licensed  CYTOGEN  Patents  or CYTOGEN  Technical  Information
without prior thereto having obtained an agreement of confidentiality  from such
person.

     (b) CYTOGEN and, to CYTOGEN's knowledge,  SKICR and [CONFIDENTIAL TREATMENT
HAS BEEN REQUESTED]  have obtained from all individuals who  participated in any
respect in the  invention  or  authorship  of any  Licensed  CYTOGEN  Patents or
CYTOGEN Technical Information (as employees, consultants or otherwise) effective
waivers of any and all ownership  rights of such  individuals in such rights and
assignments to CYTOGEN, SKICR or [CONFIDENTIAL TREATMENT HAS BEEN REQUESTED], as
applicable, all rights with respect thereto.

     2.2.13. Patent Prosecution Disclosure. CYTOGEN has disclosed to the LLC all
of the prosecution files of all of the patents and patent applications  licensed
to the LLC by CYTOGEN hereunder.

     2.2.14.  Patents in the Field. To CYTOGEN's  knowledge,  on the date hereof
CYTOGEN  does not have a  licensable  right to any Patent  used or useful in the
Field except as disclosed on Annex A hereto.

     3. LICENSES.
        ---------

     3.1.  Grant by  Progenics.  Subject  to the  terms  and  conditions  herein
contained,  Progenics  hereby  grants to the LLC, to the extent (but only to the
extent) of the Field,  the exclusive  (even as to  Progenics)  right and license
throughout the Territory under the Licensed  Progenics Patents and the Progenics
Technical Information to develop,  make, have made,  distribute,  use, offer for
sale, sell, have sold, import or export Licensed Progenics Products.

     3.2.  Grant  by  CYTOGEN.  Subject  to  the  terms  and  conditions  herein
contained,  CYTOGEN  hereby  grants to the LLC,  to the extent  (but only to the
extent) of the Field,  the  exclusive  (even as to  CYTOGEN)  right and  license
throughout  the  Territory  under the Licensed  CYTOGEN  Patents and the CYTOGEN
Technical Information to develop,  make, have made,  distribute,  use, offer for
sale,  sell, have sold,  import or export Licensed CYTOGEN  Products;  provided,
however,  that until such time as the NWC  Agreement is terminated in accordance

                                       10
<PAGE>

with  Section 4.8 hereof,  the license  granted by CYTOGEN  hereunder to make or
have made  Licensed  CYTOGEN  Products is subject to the  manufacturing  license
granted to NWC pursuant to the NWC Agreement.

     3.2.1. Limited Right to MoAb 7E11. To enable the LLC, Affiliates of the LLC
and third party  sublicensees to utilize MoAb 7E11 solely in connection with the
development,  manufacturing,  testing and/or conducting quality control tests on
Licensed  Products,  CYTOGEN hereby grants to the LLC the right to use MoAb 7E11
solely for such purposes.

     3.2.2.  Antibody  Requirements.  CYTOGEN agrees to sell to the LLC its MoAb
7E11 needs at a purchase price not to exceed CYTOGEN's actual and direct costs.

     3.2.3.  Contingent  License.  In the event that CYTOGEN is unable to supply
the LLC with its requirements of MoAb 7E11,  CYTOGEN shall, upon written request
by the LLC,  provide  to the LLC,  at the  LLC's  cost,  a  viable  sample  of a
hybridoma  capable  of  producing  MoAb  7El1,  and  license  to  the  LLC  on a
non-exclusive,  royalty-free basis the right to use the hybridoma and to produce
and use MoAb 7E11 for the purposes set forth in Section 3.2.1 hereof.

     3.3.  Licensing of  Additional  Patents and Technical  Information.  (a) If
Progenics or CYTOGEN (in either case, the "Non-Offering  Party")  identifies any
Patent or Technical  Information  used or useful in the Field in which the other
party (the  "Offering  Party") has a licensable  right that has not  theretofore
been  licensed to the LLC by the  Offering  Party,  the  Non-Offering  Party may
request  the  Offering  Party to offer  to  license  such  Patent  or  Technical
Information to the LLC pursuant to the terms of this Agreement. Any such request
shall be in writing and shall reference the rights requested to be licensed.  If
so  requested,  the Offering  Party shall make such an offer in writing,  and in
connection  therewith shall disclose to the Non-Offering Party the nature of the
Patent or Technical  Information  and the terms on which the Offering Party owns
or  licenses  such  Patent  or  Technical  Information,  and if such  Patent  or
Technical  Information is licensed,  shall provide to the Non-Offering  Party an
accurate and complete copy of the relevant license agreement. The Offering Party
shall offer to make to the LLC and the Non-Offering  Party, with respect to such
Patent or Technical Information, the representations and warranties set forth in
Annex D  hereto,  subject  to such  exceptions  as  shall be  identified  by the
Offering  Party.


     (b) If after the date hereof Progenics or CYTOGEN (in either case, also the
"Offering  Party")  acquires  a  licensable  right in any  Patent  or  Technical
Information  used or useful in the Field,  the  Offering  Party  shall  promptly
thereafter  offer in writing to license such Patent or Technical  Information to
the LLC pursuant to the terms of this  Agreement.  In  connection  with any such
offer,  the  Offering  Party  shall  disclose  to the  other  party  (also,  the
"Non-Offering  Party") the nature of the Patent or Technical Information and the
terms on which the  Offering  Party owns or licenses  such  Patent or  Technical
Information,  and if such Patent or Technical  Information  is  licensed,  shall
provide to the Non-Offering  Party an accurate and complete copy of the relevant
license  agreement.  In addition,  the Offering Party shall offer to make to the
LLC and the  Non-Offering  Party,  with  respect  to such  Patent  or  Technical
Information,  the  representations  and  warranties set forth in Annex C hereto,
subject to such exceptions as shall be identified by such party.


                                       11
<PAGE>
     (c) If a license grant offer is made pursuant to Section  3.3(a) or Section
3.3(b) hereof,  the Non-Offering  Party shall have 30 calendar days to determine
whether  to cause the LLC to  accept  such  offer.  Such  offer  shall be deemed
accepted  by the LLC if the  Non-Offering  Party  delivers a written  acceptance
notice to the Offering Party within such 30-day period (which shall be deemed to
be the written  consent  contemplated by Section 1.6, 1.12, 1.16 or 1.33 hereof,
as the case may  be).  Upon the  delivery  of such  acceptance  notice,  (i) any
Patents or Technical  Information subject to the offer shall thereupon be deemed
to  be  Licensed  Progenics  Patents  (under  Section  1.16  hereof),  Progenics
Technical  Information  (under Section 1.33 hereof),  Licensed  CYTOGEN  Patents
(under Section 1.12 hereof) or CYTOGEN Technical  Information (under Section 1.6
hereof), as the case may be, and (ii) the Offering Party shall be deemed to have
made the  representations  and  warranties  referred to in  Sections  3.3(a) and
3.3(b)  hereof,  subject to the  exceptions  identified by the Offering Party as
described in such sections.

     3.4. Sublicenses.  The LLC shall have the right to grant sublicenses of the
rights granted  hereunder,  provided that: (i) each such  sublicensee  agrees in
writing to keep books and  records  and permit  Progenics  and CYTOGEN to review
such books and records pursuant to the relevant  provisions,  and to comply with
all terms of this  Agreement  expressly  applicable to a sublicensee of the LLC;
and (ii)  within 15 days of  granting  any such  sublicense  the LLC shall  give
written notice of such grant to Progenics and CYTOGEN and provide  Progenics and
CYTOGEN with a copy of such  sublicense.  No consent or approval of Progenics or
CYTOGEN shall be required in connection with the granting of such sublicenses.

     3.5.   Guarantee   of   Performance   of   Sublicensee.   The  LLC   hereby
unconditionally  guarantees to Progenics and CYTOGEN the  performance  of any of
its sublicensees' financial obligations hereunder, including making all payments
due, and making all reports required,  under this Agreement to be made by reason
of sales of Licensed  Products by its sublicensees and their compliance with all
applicable  terms of this  Agreement.  In any such  sublicense,  the sublicensee
shall agree that in the event of a breach by the  sublicensee  in the observance
of any  applicable  terms  of  this  Agreement,  Progenics  and/or  CYTOGEN,  as
applicable,  shall be entitled to proceed  either  against such  sublicensee  or
directly  against the LLC, as  Progenics  and/or  CYTOGEN,  as  applicable,  may
determine in their respective sole discretion, to enforce this Agreement.

     3.6.  Cure of Breach by  Sublicensee.  Upon  notification  to Progenics and
CYTOGEN  by the  LLC of  the  grant  by the  LLC of any  sublicense  under  this
Agreement, Progenics and CYTOGEN shall become obligated to notify in writing any
such  sublicensee  of any  breach  by the  LLC  hereunder,  or of any  purported
termination  by  CYTOGEN  or  Progenics,  with  such  notice  to be sent to such
sublicensee (at the address  specified by the LLC) at the same time as notice is
sent to the LLC. In the event that the LLC breaches this Agreement, which breach
remains  uncured  through the  expiration  of any  applicable  cure period,  any
sublicensee of the LLC hereunder  shall have the right,  but not the obligation,
during a period of 45 days after the expiration of the aforesaid cure period, to
cure such breach in its own name, and, upon curing such breach, such sublicensee
shall have the right to be substituted for the LLC as a direct sublicensee under
the  Licenses  to the  exclusion  of,  and on the same  terms as, the LLC to the
extent of the  sublicense.  A provision to the effect of the foregoing  shall be
included in any sublicense granted hereunder.

     3.7 [CONFIDENTIAL TREATMENT HAS BEEN REQUESTED]


                                       12
<PAGE>
     3.8 [CONFIDENTIAL TREATMENT HAS BEEN REQUESTED]

     3.9.  Reservation of Rights.  Progenics  reserves the right to practice and
use the Progenics Technical Information and to develop,  make, have made and use
Licensed Progenics Products,  and CYTOGEN reserves the right to practice and use
the  CYTOGEN  Technical  Information  and to  develop,  make,  have made and use
Licensed  CYTOGEN  Products,  in each  case  without  cost  and  subject  to the
confidentiality  provisions  of  this  Agreement,  for  non-commercial  internal
research and development purposes.

     3.10. No Other Rights. Except as expressly provided herein, no right, title
or interest is granted (i) by Progenics  under the Licensed  Progenics  Patents,
the Progenics  Technical  Information  or otherwise or (ii) by CYTOGEN under the
Licensed  CYTOGEN  Patents,  the CYTOGEN  Technical  Information  or  otherwise.
Progenics and CYTOGEN  expressly do not grant,  and nothing  contained herein is
intended  to grant,  or shall be  construed  as  granting,  any right,  title or
interest outside of the Field.

     3.11. Competition Not Prohibited.  No license granted under this Agreement,
and no other provision  contained herein,  shall be deemed to prohibit Progenics
or CYTOGEN from  engaging in any activity  outside of the Field,  whether or not
such activity is competitive  with the development or  commercialization  of any
Licensed Product or any other activity of the LLC.

     4. CERTAIN COVENANTS.
        ------------------

     4.1. Diligence.  The LLC shall use reasonable commercial efforts consistent
with its sound business judgment to promptly develop, obtain regulatory approval
for, manufacture, market and sell Licensed Products. In the event that Progenics
and/or CYTOGEN, from time to time during the term of this Agreement, determines,
in the exercise of its or their  reasonable  business  judgment after discussion
with the  LLC,  that  the LLC is not  using  reasonable  commercial  efforts  to
develop, obtain regulatory approval for, manufacture, market and sell a Licensed
Product  within the  United  States and at least one other  Major  Market,  then
Progenics  and/or  CYTOGEN,  as the case may be, shall have the right to request
that the LLC  immediately  undertake  such  efforts.  In the event that any such
request is made by Progenics  and/or CYTOGEN to the LLC, and the LLC,  within 90
days of such request, does not provide Progenics and/or CYTOGEN, as the case may
be,  with  satisfactory  evidence  that  the LLC is  undertaking  such  efforts,
Progenics and/or CYTOGEN,  as the case may be, shall have the right to terminate
the license  granted by such party to the LLC  hereunder.  In the event that the
LLC does not agree with any such determination by Progenics or CYTOGEN,  the LLC
and Progenics  and/or CYTOGEN,  as the case may be, shall resolve such matter in
accordance with Section 14.11 hereof. For purposes of the foregoing, the efforts
of the LLC's Affiliates and sublicensees, and of distributors, clinical research
organizations  and  other  third  parties  acting  on  behalf  of the  LLC,  its
Affiliates  or  sublicensees,  shall be  deemed  to be the  efforts  of the LLC.
Notwithstanding the provisions of this Section 4.1 neither Progenics nor CYTOGEN
shall be entitled to  terminate,  pursuant to this  Section  4.1,  the  licenses
granted  hereunder  if the LLC's  failure  to use  reasonable  best  efforts  to
promptly develop,  obtain regulatory approval for, manufacture,  market and sell
Licensed Products results from such party's actions or omissions in its capacity
as an owner of equity  interest of the LLC or from the actions or  omissions  of
such party's representatives in their capacity as managers of the LLC.

                                       13
<PAGE>

     4.2. No Waivers or Grant of Further  Rights.  Neither  party  hereto  will,
without the prior written consent of the other parties hereto, terminate, amend,
modify or grant any waivers or consents  under any Prime License with respect to
the Field,  or grant any further  rights in the Field except to the LLC, or take
any other action with respect to the Licensed Patents or the Licensed  Technical
Information that could adversely affect the rights granted to the LLC hereunder.

     4.3.  Summary  Reports.  For so  long  as the  LLC is  developing  Licensed
Products,  the LLC shall keep  Progenics and CYTOGEN  informed  through  written
summary reports about the status of the development of Licensed  Products.  Such
reports shall be provided to Progenics and CYTOGEN on an annual basis,  with the
first report due on the first anniversary of the Effective Date.

     4.4.  Breach of SKICR  Agreement.  In the event  that  CYTOGEN  shall be in
breach of or default under any of the material  terms,  conditions or agreements
contained in the SKICR Agreement or the Wright Agreement to be kept, observed or
performed by it, or receives notice of breach or termination of or default under
such agreements, it shall immediately notify the LLC thereof. If CYTOGEN has not
cured  such  breach  or  default   within   [CONFIDENTIAL   TREATMENT  HAS  BEEN
REQUESTED]after  the  effective  date of any notice of  termination  issued with
respect to such  breach or  default,  the LLC shall have the right,  but not the
obligation,  to cure any such  breach or  default  in its own name,  and the LLC
shall have the right to be  substituted  for  CYTOGEN as direct  licensee in the
Field under either such agreement to the exclusion of, and on the same terms as,
CYTOGEN.  If the LLC elects not to cure such  breach or default or fails to cure
such breach or default within [CONFIDENTIAL TREATMENT HAS BEEN REQUESTED] of the
notice, then Progenics shall have the right, but not the obligation, to cure any
such  breach  or  default  in its own  name,  [CONFIDENTIAL  TREATMENT  HAS BEEN
REQUESTED]

     4.5. Acquiring Other Rights in the Field.  Progenics and CYTOGEN agree that
they will not,  without  the prior  written  consent  of the  other,  acquire by
license or  otherwise  intellectual  property  rights in the Field  unless  such
rights include the right to grant a sublicense of such rights to the LLC.

     4.6.  Notices  under Prime  Licenses.  Each of Progenics  and CYTOGEN shall
require each  licensor of any Prime License to which it is or becomes a party to
furnish  copies of all notices and other  communications  required or  permitted
under such Prime  License  (including  without  limitation  notices of breach or
termination) to the LLC and, upon the request of the LLC, to such sublicensee(s)
of the LLC as the LLC shall specify. In addition,  each of Progenics and CYTOGEN
will furnish copies of all notices and  communications  to the LLC and, upon the
request of the LLC, to such sublicensees of the LLC as the LLC shall specify.

     4.7. Compliance with Terms of Prime Licenses; Assignment. Each of Progenics
and CYTOGEN  shall  fulfill each of its  obligations  under any Prime License to
which it is a party. Without limiting the generality of the foregoing, within 30
days of the  execution  of this  Agreement  CYTOGEN  shall  notify  SKICR of the
execution of this Agreement and provide SKICR with the LLC's name and address as


                                       14
<PAGE>

required by Section  III.D.3.  of the SKICR  Agreement.  Neither  Progenics  nor
CYTOGEN  will assign any  interests  under a Prime  License  unless the assignee
expressly  agrees to take  such  interest  subject  to the  interest  of the LLC
hereunder.

     4.8 [CONFIDENTIAL TREATMENT HAS BEEN REQUESTED]

     5. ROYALTIES AND OTHER PAYMENTS. In further consideration for the exclusive
licenses  granted by Progenics and CYTOGEN to the LLC pursuant to the provisions
of Sections 3.1 and 3.2 hereof, the LLC agrees to make the following payments to
Progenics and CYTOGEN as follows:

     5.1. Amounts Payable with Respect to the Progenics  License.  The LLC shall
pay earned royalties to Progenics with respect to any sale of Licensed Progenics
Products.  Such royalties  shall be paid at cost -- i.e., at the minimum royalty
rate(s) required to be paid by Progenics, and at the times any such payments are
due,  under any Prime License.  In addition,  the LLC will pay to Progenics fees
equal in amount to the minimum amount of any license, milestone, minimum royalty
or other fees  required  to be paid by  Progenics  to any third  party under any
Prime  License at the times any such  payments are due. Any license,  milestone,
minimum royalty or other fees (but excluding  earned  royalties)  payable by the
LLC to  Progenics  pursuant to this  Section  5.1 in respect of a Prime  License
shall be  discounted  if  Progenics  has not  sublicensed  to the LLC all of the
intellectual  property rights acquired by Progenics in such Prime License.  Such
discount shall be equal to the  proportionate  economic value, as agreed upon in
good faith by the parties hereto at the time such rights are  sublicensed to the
LLC,  of the  rights  not so  sublicensed  relative  to the  totality  of rights
licensed to Progenics in the Prime License.

     5.2. Amounts Payable with Respect to the CYTOGEN License. The LLC shall pay
earned  royalties  to  CYTOGEN  with  respect  to any sale of  Licensed  CYTOGEN
Products.  Such royalties  shall be paid at cost -- i.e., at the minimum royalty
rate(s)  required to be paid by CYTOGEN,  and at the times any such payments are
due,  under any Prime  License.  In  addition,  the LLC will pay to CYTOGEN fees
equal in amount to the minimum amount of any license, milestone, minimum royalty
or other fees  required to be paid by CYTOGEN to any third party under any Prime
License at the times any such payments are due. Any license, milestone,  minimum
royalty or other fees (but  excluding  earned  royalties)  payable by the LLC to
CYTOGEN  pursuant  to this  Section 5.2 in respect of a Prime  License  shall be
discounted  if CYTOGEN has not  sublicensed  to the LLC all of the  intellectual
property rights  acquired by CYTOGEN in such Prime License.  Such discount shall
be equal to the  proportionate  economic  value, as agreed upon in good faith by
the parties  hereto at the time such rights are  sublicensed  to the LLC, of the
rights not so sublicensed relative to the totality of rights licensed to CYTOGEN
in the Prime License. In particular, the license, milestone,  minimum royalty or
other fees  payable  by the LLC to CYTOGEN  pursuant  to this  Section  5.2 with
respect to amounts due by CYTOGEN to SKICR pursuant to the SKICR Agreement shall
be discounted  by  [CONFIDENTIAL  TREATMENT  HAS BEEN  REQUESTED] to reflect the
value of rights  sublicensed by SKICR to CYTOGEN but not  sublicensed by CYTOGEN
to the LLC.

     5.3. Allocation of Royalties. If (i) any Prime License requires the payment
of  royalties  at a rate  which  varies  with sales  volume and (ii)  CYTOGEN or
Progenics  (as  the  case  may  be as  to  any  particular  Prime  License)  has


                                       15
<PAGE>
sublicensed  rights  under such Prime  License  to one or more  persons  ("Other
Licensees")  in addition to the LLC,  then the royalty  rates  applicable to the
sale of Licensed  Products for purposes of  determining  royalties  payable with
respect  to such  Prime  License  shall be  calculated  by making  an  equitable
allocation (on a notional basis) of net sales by the LLC and the Other Licensees
as to each royalty rate/sales level.

     6. PATENT PROSECUTION AND MAINTENANCE, ETC.
        ----------------------------------------

     6.1.  Prosecution  and  Maintenance.  To  the  fullest  extent  legally  or
contractually  entitled,  each of Progenics and CYTOGEN hereby grants to the LLC
the  exclusive  right to  prepare,  file or  prosecute  any  patent  application
licensed  to the LLC by such  party,  maintain  or extend the term of any issued
Patent  licensed  to the LLC by such party and  defend  against  any  conflicts,
oppositions  or  interferences   involving  third-party  challenges  to  Patents
licensed to the LLC by such party. The cost of such activities shall be borne by
the LLC;  provided,  however,  that if less  than all of the  rights to any such
Patent has been  licensed to the LLC  pursuant  hereto,  the LLC shall bear only
that  portion  of the cost of such  activities  as  reflects  the  proportionate
economic  value,  as agreed  upon in good faith by the  parties  hereto,  of the
rights licensed to the LLC. Progenics and CYTOGEN shall cooperate,  at the LLC's
expense,  with all reasonable requests of the LLC in all such activities.  If at
any  time  the  LLC  determines  not  to  prepare,   file  or  prosecute  patent
applications  licensed to the LLC hereunder,  maintain or extend the term of any
issued  Patent  licensed to the LLC hereunder or defend  against any  conflicts,
oppositions  or  interferences  involving  third-party  challenges to any Patent
licensed  to the LLC  hereunder,  the LLC shall  notify  CYTOGEN (in the case of
Licensed  CYTOGEN  Patents)  or  Progenics  (in the case of  Licensed  Progenics
Patents) of any such  determination  and grant back to CYTOGEN or Progenics,  as
the case may be,  the  right to  conduct  any  such  activity.  If the  right to
prepare,  file or  prosecute  any patent  application  licensed  to the  Company
hereunder,  or to  maintain  or  extend  or to defend  against  any  third-party
conflicts, oppositions or interferences involving any Patent licensed to the LLC
hereunder  cannot be granted to the LLC, the party  licensing  such Patent shall
use  commercially  reasonable  efforts  diligently  to  perform,  or cause to be
performed,  in  consultation  with the LLC,  such  activities.  The cost of such
activities shall be borne by the LLC; provided,  however,  that if less than all
of the rights to any such Patent has been  licensed to the LLC pursuant  hereto,
the LLC shall bear only that portion of the cost of such  activities as reflects
the  proportionate  economic  value, as agreed upon in good faith by the parties
hereto, of the rights licensed to the LLC.

     6.2.  Disclosure  Regarding Patent Activities.  Each party which engages in
patent  activities of the nature  described in section 6.1 hereof shall promptly
provide the other parties hereto with all correspondence  (including any filings
sent or received) and all other  information  concerning such  activities  which
comes into such  party's  possession,  and shall  periodically  update the other
parties hereto on all relevant  information  concerning the actions described in
Section  6.1  hereof.  In  addition  to the  foregoing,  each party  required to
disclose  information  pursuant to this  Section 6.2 shall  provide to the other
parties hereto a reasonable  opportunity to review any materials to be submitted
or filed with any patent or  governmental  authority or in  connection  with any
such  proceeding  and to comment on such materials and will discuss and consider
such comments in good faith.  The parties  hereto  consent to the  disclosure of
such  correspondence  by the  LLC,  at its  discretion,  to any  and  all of its
Affiliates and any  sublicensee,  provided that such Affiliates and sublicensees


                                       16

<PAGE>

shall receive such  correspondence  under a  confidential  disclosure  agreement
reasonably  satisfactory  in form and substance to Progenics or CYTOGEN,  as the
case may be.

     7. REPORTS AND ROYALTY PAYMENTS; BOOKS AND RECORDS.
        ------------------------------------------------

     7.1. Reports. On or before the last day of each February,  May, August, and
November commencing with the first Commercial Sale and thereafter throughout the
Contract  Period,  the LLC shall  furnish  Progenics  and CYTOGEN with a written
report,  signed  by an  authorized  officer  or agent of the  LLC,  showing  all
Commercial Sales with respect to which earned royalties are due Progenics and/or
CYTOGEN hereunder with respect to the quarters ended December 31, March 31, June
30 and September 30, respectively.

     7.2. Royalty Payments. With each such quarterly report, the LLC shall remit
to Progenics  and/or CYTOGEN the total amount of earned  royalties shown thereby
to be due.  All payments  shall be made in lawful funds of the United  States of
America.

     7.3.  Calculation of Royalties and Other  Payments.  In order to permit the
LLC to calculate the amount of royalties and other payments  payable pursuant to
Section  5 hereof,  Progenics  and  CYTOGEN  shall  provide  to the LLC true and
complete copies of all Prime  Licenses.  Progenics and CYTOGEN will also furnish
the LLC with a written report, signed by an authorized officer,  stating product
sales by each of the other  licensees (if any) covered by such Prime License (to
the extent available to, and not subject to legal or contractual restrictions on
disclosure  by,  Progenics or CYTOGEN,  as the case may be), and will make their
respective  personnel  available  to  answer  questions  and  otherwise  provide
information  with  respect to any matters  reasonably  necessary  for the LLC to
calculate amounts due by the LLC to Progenics or CYTOGEN under Section 5 hereof.

     7.4. Currency Control Restrictions.  In the event that the LLC is precluded
from  transferring  royalties due Progenics and/or CYTOGEN hereunder at any time
during the Contract  Period  because the LLC has failed  after due  diligence to
obtain the approval of such transfer from the  appropriate  governmental  agency
responsible for control of currency  exchanges of a particular  country in which
the LLC has sold  Licensed  Products,  then the LLC  agrees (a) to deposit or to
cause the deposit of such  royalties to the account of Progenics or CYTOGEN,  as
the case may be, in a bank in such country designated by the beneficiary of such
deposit;  (b)  to  provide  or to  cause  to be  provided  to  such  beneficiary
documentary  evidence of such deposits;  and (c) to remit or to cause remittance
of such deposits to such beneficiary immediately upon the subsequent approval of
such transfers by such governmental agency. The LLC further agrees that the form
of such  depository  account  shall  permit such  beneficiary  to  withdraw  the
deposited  amounts at will,  but shall permit the LLC to withdraw the  deposited
amounts  solely for the purpose of remitting  such  amounts to such  beneficiary
pursuant to the provisions of this Paragraph 7.4.

     7.5.  Books and  Records.  The LLC  agrees to keep  adequate  and  complete
records showing all Commercial Sales and/or other revenues with respect to which
earned  royalties  and/or  other  payments  are  due  Progenics  and/or  CYTOGEN
hereunder.  Such records shall include all  information  necessary to verify the
total  amount  and  computation  of  earned   royalties  and/or  other  payments
hereunder,  and shall be open to  inspection  by  Progenics  and CYTOGEN  during


                                       17
<PAGE>

reasonable  business hours to the extent necessary to verify the amount thereof.
Such  inspection  by each of Progenics  and CYTOGEN shall be made not more often
than once each calendar year at the request of Progenics  and/or CYTOGEN (unless
good  cause is shown  by  Progenics  or  CYTOGEN  of the need for more  frequent
inspection) by an auditor  appointed by the requesting party and to whom the LLC
has no  reasonable  objection,  provided  that  such  auditor  shall  be under a
confidentiality obligation to the LLC to reveal only that information,  and only
to the requesting  party,  necessary to verify the royalties due  hereunder.  In
addition,  such  inspection  shall be limited  to a period not to extend  beyond
three years after the date of receipt by the  requesting  party of a report from
the LLC  relating to such  records  pursuant  to Section 7.1 hereof.  After such
three-year  period,  any such report and the records  upon which such report was
based  shall be deemed  presumptively  correct.  The  expenses of any such audit
shall be borne by the party  requesting the audit unless the audit  determines a
discrepancy in favor of the requesting party of at least [CONFIDENTIAL TREATMENT
HAS BEEN  REQUESTED],  in which event the audit  expenses  shall be borne by the
LLC.  Notwithstanding  the  foregoing,  either  Progenics or CYTOGEN  shall,  at
reasonable  times and upon  reasonable  notice,  be  granted  access  after such
three-year  period  to such  records  (to the  extent  retained  by the LLC) for
purposes of preparing tax returns and related materials.

     8.  TAXATION OF  PAYMENTS.  Insofar as any earned  royalties  which are due
Progenics or CYTOGEN  hereunder are subject to taxation by any country under the
provisions  of the tax laws of that  country,  then the LLC  agrees to bear such
taxes, and Progenics and CYTOGEN hereby authorize the LLC to withhold such taxes
from the payments which are payable to Progenics and CYTOGEN in accordance  with
this  Agreement if the LLC is either  required to do so under such country's tax
laws or directed to do so by an agency of such  country's  government.  Whenever
the LLC deducts  such tax from any payments  due  Progenics or CYTOGEN,  the LLC
shall furnish  Progenics or CYTOGEN,  as the case may be, with a tax certificate
showing the payment of such tax to the government of such country.  In the event
such taxes are  assessed  against  the LLC by reason of its  failure to withhold
such taxes from any  payments  which have been paid to  Progenics  or CYTOGEN in
accordance with this Agreement,  then Progenics or CYTOGEN,  as the case may be,
agrees  to  reimburse  the LLC for such  tax  assessment  but not for any  fine,
penalty,  fee or interest related to the LLC's failure to withhold,  pay or make
timely payment of such taxes.

     9. PRODUCT LIABILITY DISCLAIMERS.
        ------------------------------

     9.1.  Product  Liability  Disclaimer  by  Progenics.  Progenics  assumes no
responsibility for the manufacture, product specifications, end use or provision
of any Licensed  Products that are  manufactured  or provided by or for, or sold
by,  the  LLC or any  Affiliate  or  third-party  licensee.  All  warranties  in
connection  with  such  Licensed  Products  made or  provided  by the LLC or any
Affiliate or  third-party  licensee  shall not  directly or  impliedly  obligate
Progenics in any manner whatsoever under such warranties or otherwise.

     9.2.  Product   Liability   Disclaimer  by  CYTOGEN.   CYTOGEN  assumes  no
responsibility for the manufacture, product specifications, end-use or provision
of any Licensed  Products that are  manufactured  or provided by or for, or sold
by,  the  LLC or any  Affiliate  or  third-party  licensee.  All  warranties  in
connection  with  such  Licensed  Products  made or  provided  by the LLC or any


                                       18
<PAGE>

Affiliate or  third-party  licensee  shall not  directly or  impliedly  obligate
CYTOGEN in any manner whatsoever under such warranties or otherwise.

     9.3.  Product  Liability   Disclaimer  by  the  LLC.  The  LLC  assumes  no
responsibility  for the  manufacture or product  specifications  of any products
which are manufactured by or for Progenics or CYTOGEN except for the manufacture
or product specifications of materials made by or for the LLC. Any warranties in
connection  with such  products  made by  Progenics  or  CYTOGEN as user of such
products shall not directly or impliedly obligate the LLC.

     10. INDEMNIFICATION AND INFRINGEMENT.
         ---------------------------------

     10.1. Indemnification.

     10.1.1.  By Progenics.  Progenics shall indemnify,  defend and hold CYTOGEN
and  the  LLC,  their  respective  Affiliates  and  any  sublicensee  of the LLC
hereunder  harmless  from and against  any and all claims,  suits or demands for
liability,  damages, losses, costs and expenses,  including the reasonable costs
and expenses of counsel (collectively,  "Losses"), arising out of (i) any breach
of the  representations  and  warranties,  or the failure to perform when and as
required any of the covenants or agreements, made by Progenics in this Agreement
or (ii) any infringement or purported  infringement of third-party  intellectual
property  rights by practicing the Licensed  Progenics  Patents or the Progenics
Technical Information.

     10.1.2. By CYTOGEN. CYTOGEN shall indemnify,  defend and hold Progenics and
the LLC, their  respective  Affiliates and any  sublicensee of the LLC hereunder
harmless  from and against  any and all Losses  arising out of (i) any breach of
the  representations  and  warranties,  or the  failure to  perform  when and as
required any of the covenants or  agreements,  made by CYTOGEN in this Agreement
or (ii) any infringement or purported  infringement of third-party  intellectual
property  rights by  practicing  the  Licensed  CYTOGEN  Patents or the  CYTOGEN
Technical Information.

     10.1.3. By the LLC. The LLC shall indemnify,  defend and hold Progenics and
CYTOGEN their  respective  Affiliates  and any  sublicensee of the LLC hereunder
harmless  from and against  any and all Losses  arising out of (i) any breach of
the  representations  and  warranties,  or the  failure to  perform  when and as
required any of the covenants or  agreements,  made by the LLC in this Agreement
or (ii) any claim by a third party that any Licensed  Product made, used or sold
by or on behalf of the LLC or any sublicense  thereof infringes patent rights of
such  third  party  (except   insofar  as  any  such  claim  gives  rise  to  an
indemnification  obligation  of  Progenics  under  Section  10.1.1  hereof or of
CYTOGEN under Section 10.1.2 hereof.

     10.2.  Third Party  Infringement of Licensed  Patent Rights.  The following
provisions relate to third-party infringement of any of the Licensed Patents:

     10.2.1.  Infringement of Licensed Progenics Patents.  In the event that any
party hereto  becomes aware that any third party is infringing any claims of any
issued patent included within the Licensed Progenics Patents  sublicensed to the
LLC  hereunder,  then such party  shall  immediately  advise  the other  parties
hereto,  and the parties shall consult with each other as to the most  effective
way of proceeding. Under such circumstances:


                                       19
<PAGE>
     (a) the LLC, as the exclusive  licensee of the Licensed  Progenics Patents,
shall have the right,  but not the  obligation,  and  subject to any  applicable
third-party  rights,  to commence and prosecute an action under the  appropriate
Licensed  Progenics  Patents against any such  third-party  infringer,  in which
event  the LLC shall  bear the costs of such  action  and shall be  entitled  to
retain any recovery resulting therefrom;

     (b) if the LLC declines or fails to commence and/or  prosecute such action,
then  Progenics  shall be entitled to commence and prosecute an action under the
appropriate  Licensed Progenics Patents against such third-party  infringer,  in
which event  Progenics shall bear the costs of such action and shall be entitled
to retain any recovery resulting therefrom.

     The  parties  hereto  shall  cooperate  fully  with each  other in any such
proceedings,  including  joining as a necessary  party  (subject to  appropriate
indemnification  arrangements),  shall consult as to litigation  strategies  and
other matters related to any such  proceedings,  and shall,  among other things,
furnish  information  and evidence  when so  requested  by the other,  including
testimony by the requested party,  its agents and employees,  as may be required
by the party commencing and prosecuting such action.

     10.2.2.  Infringement of Licensed  CYTOGEN  Patents.  In the event that any
party  hereto  becomes  aware that any third  party is  infringing  any claim or
claims of any  issued  patent  included  within  the  Licensed  CYTOGEN  Patents
sublicensed to the LLC hereunder,  then such party shall immediately  advise the
other  parties  hereto,  and the parties shall consult with each other as to the
most effective way of proceeding. Under such circumstances:

     (a) the LLC, as the  exclusive  licensee of the Licensed  CYTOGEN  Patents,
shall have the right,  but not the  obligation,  and  subject to any  applicable
third-party  rights,  to commence and prosecute an action under the  appropriate
Licensed CYTOGEN Patents against any such third-party infringer,  in which event
the LLC shall bear the costs of such  action and shall be entitled to retain any
recovery resulting therefrom;

     (b) if the LLC declines or fails to commence and/or  prosecute such action,
then  CYTOGEN  shall be entitled to commence  and  prosecute an action under the
appropriate  Licensed  CYTOGEN Patents against such  third-party  infringer,  in
which event CYTOGEN shall bear the costs of such action and shall be entitled to
retain any recovery resulting therefrom.

     The  parties  hereto  shall  cooperate  fully  with each  other in any such
proceedings, consulting as to litigation strategies and other matters related to
any such proceedings,  and shall,  among other things,  furnish  information and
evidence  when so requested by the other,  including  testimony by the requested
party, its agents and employees,  as may be required by the party commencing and
prosecuting such action.

     11. TERM AND TERMINATION.
         ---------------------

     11.1.  Term.  Unless sooner  terminated in a manner herein  provided,  this
Agreement  shall commence as of the Effective Date and shall  terminate upon the
last to expire or terminate of any  licensable  rights to Patents that have been
licensed by Progenics or CYTOGEN to the LLC hereunder;  provided,  however, that
the  provisions  of Sections 7.1, 7.5, 9, 10, 12 and 14 hereof shall survive any
such termination.


                                       20

<PAGE>

     11.2.  Termination.  This  Agreement may be terminated at any time prior to
the end of the term set forth in Section 11.1 hereof, as follows:

     11.2.1.  For Breach.  In the event any party hereto shall breach any of the
material  representations  or  warranties  or any  material  term,  condition or
agreement contained herein made or to be kept, observed or performed by it, then
any other party hereto may terminate this  Agreement,  at its option and without
prejudice to any of its other legal or equitable rights and remedies,  by giving
the other parties hereto 60 days' notice in writing, identifying with reasonable
specificity the breach,  unless (in the case of a breach of any term,  condition
or agreement)  the notified party within such 60-day period shall have cured the
breach. Notwithstanding the foregoing, if a party hereto has given notice of the
breach of another party hereto, and the breaching party has not cured the breach
within the 60-day period  described above, the third party hereto may (but shall
not be obligated to), upon notice given to the other  non-breaching party hereto
prior to the expiration of such 60-day period, elect to cure such breach. If the
third  party cures such breach  within 30 days of the  expiration  of the 60-day
period described above,  such third party shall be substituted for the breaching
party for all purposes of this  Agreement,  and shall  thereafter be entitled to
all the  rights and  subject  to all the  obligations  of such  breaching  party
hereunder. The breach of the representation contained in Section 2.1.7 or 2.2.14
hereof,  absent fraud,  bad faith or willful  misrepresentation,  shall not give
rise to a termination right under this Section 11.2.1.

     11.2.2.  For Bankruptcy.  (a) In the event (i) a party hereto shall suspend
business,  or shall  file a  voluntary  petition  or any  answer  admitting  the
jurisdiction  of the court and the material  allegations of, or shall consent to
an  involuntary  petition  pursuant  to or  purporting  to be  pursuant  to  any
reorganization  or  insolvency  law  of  any  jurisdiction,  or  shall  make  an
assignment  for the benefit of  creditors,  or shall apply for or consent to the
appointment of a receiver or trustee of a substantial part of its property,  and
(ii) no Affiliate of such party shall undertake to assume its obligations  under
the  provisions  of this  Agreement  within 90 days from the date on which  such
party  becomes so  disabled,  then to the extent  permitted by law either of the
other parties may  thereafter  immediately  terminate  this  Agreement by giving
written notice of termination to the other parties.

     (b) In the event Progenics and/or CYTOGEN,  as the case may be,  terminates
this Agreement  under Section  11.2.2(a) or rejects this  Agreement  pursuant to
Section 365 of the U.S.  Bankruptcy  Code, all rights and licenses granted under
or pursuant to this Agreement by Progenics  and/or CYTOGEN,  as the case may be,
to the LLC are,  and shall  otherwise  be deemed to be, for  purposes of Section
365(n)  of the  U.S.  Bankruptcy  Code,  licenses  of  rights  to  "intellectual
property" as defined  under Section  101(52) of the U.S.  Bankruptcy  Code.  The
parties  agree that the LLC, as a licensee of such rights under this  Agreement,
shall retain and may fully  exercise all of its rights and  elections  under the
U.S.  Bankruptcy  Code.  The parties  further  agree  that,  in the event of the
commencement of a bankruptcy proceeding by or against Progenics or CYTOGEN under
the U.S.  Bankruptcy Code, the LLC shall be entitled to a complete  duplicate of
(or complete access to, as appropriate) any such  intellectual  property and all
embodiments of such  intellectual  property upon written request therefor by the
LLC. Such  intellectual  property and all embodiments  thereof shall be promptly
delivered to the LLC (i) upon any such  commencement of a bankruptcy  proceeding
upon written request  therefor by the LLC, unless  Progenics or CYTOGEN,  as the
case may be,  elects to continue to perform  all of its  obligations  under this
Agreement or (ii) if not delivered  under (i) above,  upon the rejection of this


                                       21
<PAGE>
Agreement  by or on behalf of  Progenics  or  CYTOGEN,  as the case may be, upon
written request therefor by the LLC.  Progenics or CYTOGEN,  as the case may be,
shall not interfere with the rights of the LLC as provided in this Agreement, or
any agreement supplementary hereto, to such intellectual property (including all
such  embodiments  thereof),  including  any  right  of the LLC to  obtain  such
intellectual property (or such embodiment) from any other entity.

     11.2.3.  By Progenics  or the LLC Upon  Termination  of the SKICR  License.
Either  Progenics or the LLC may  terminate  this  Agreement by giving the other
parties  hereto  30 days'  written  notice  upon the  termination  of the  SKICR
License;  provided that,  without  limiting the other rights and remedies of the
parties  hereto,  each of Progenics and CYTOGEN may seek an  appropriate  remedy
against the other if the other is responsible  for the  termination of the SKICR
License.

     11.3.  Accrued Rights and Obligations.  Termination of this Agreement shall
not relieve any party of any rights or  obligations  then  accrued  hereunder or
which by the terms hereof extend beyond the date of such termination.

     12.  EFFECT  OF  TERMINATION  ON  SUBLICENSEE.  Upon  termination  of  this
Agreement by Progenics or CYTOGEN  pursuant to Section  11.2.1 or Section 11.2.2
hereof,  any  third-party  licensee  of the LLC  which has not  breached  in any
material respect its sublicense  related to the Licensed Patents or the Licensed
Technical  Information  shall be entitled  to receive a license to the  Licensed
Patents and the Licensed  Technical  Information  directly  from  Progenics  and
CYTOGEN  granting  rights  substantially  the  same  as  those  granted  in such
sublicense and containing  obligations as a licensee  similar to those set forth
in this Agreement.

     13.  EXPORT  LICENSES.  This  Agreement  is  subject  to  any  restrictions
concerning  the export of  products  or  technical  information  from the United
States which may be imposed by the United States. Accordingly, each party agrees
that it will not  export,  directly or  indirectly,  any  technical  information
acquired  under this  Agreement or any  products  utilizing  any such  technical
information to any country for which the United States  Government or any agency
thereof at the time of export  requires an export license or other  governmental
approval,  without  first  obtaining  the  written  consent  to do so  from  the
Department  of Commerce or other  agency of the United  States  Government  when
required by an applicable statute or regulation.

     14.  MISCELLANEOUS  PROVISIONS.
          --------------------------

     14.1.  Assignability.  Except as expressly  provided  herein,  neither this
Agreement  nor any interest  hereunder  shall be  assignable by any party hereto
without the written consent of the others, and any attempted  assignment without
such  consents  shall be null and void.  Without  the consent of any other party
hereto,  this  Agreement may be assigned by any party hereto to any wholly owned
subsidiary  of such party that agrees in writing with each other party hereto to
be  jointly  and  severally  liable  with the  assigning  party  for the  timely
satisfaction  of all  obligations of the assigning  party  hereunder;  provided,
however,  that no such  assignment  shall  relieve  the  assigning  party of its
obligations  hereunder.  This Agreement shall be binding upon the successors and
permitted  assignees of the parties.  Any such  successor or permitted  assignee
shall be  subject to the same  rights  and  obligations  as the  original  party
hereunder.


                                       22

<PAGE>
     14.2. Notices. All notices and other communications  provided for hereunder
shall be in writing and shall be mailed or delivered to the business  address of
the respective parties aforementioned,  or to such other address or addresses as
either  party shall  designate  in writing to the others.  All such  notices and
communications  shall be considered  given and/or  delivered:  (i) when given if
delivered  in person or sent by  facsimile  and  acknowledged  by a  responsible
person at the office of the recipient;  (ii) one day after being sent by a major
overnight  courier;  or (iii) four days after being mailed by  registered  mail,
return receipt  requested,  at the business address of the respective parties as
specified above. All notices or communications required or permitted to be given
or sent to the LLC shall also be given or sent to  Progenics  (if such notice or
communication  is given or sent by  CYTOGEN)  or to CYTOGEN  (if such  notice or
communication is given or sent by Progenics).

     14.3. Independent Contractors.  No agency,  partnership or joint venture is
hereby established.  None of Progenics,  CYTOGEN or the LLC shall enter into, or
incur, or hold itself out to third parties as having  authority to enter into or
incur on behalf of the other  party any  contractual  obligations,  expenses  or
liabilities whatsoever, except as expressly provided herein.

     14.4.  Counterparts.  This  Agreement  may be  executed  simultaneously  in
multiple  counterparts,  each of which shall be deemed to be an original but all
of which together shall constitute one and the same agreement.

     14.5.  Entire   Understanding.   This  Agreement   constitutes  the  entire
understanding  between the parties  hereto  with  respect to the subject  matter
hereof. No modifications,  extensions, or waiver of any provisions hereof or any
release of any right  hereunder  shall be valid,  unless the same is in writing,
contains  reference  to this  Agreement  and sets forth the plan or intention to
modify same, and is consented to by all parties hereto.

     14.6.  Headings.  The headings in this  Agreement  are intended  solely for
convenience  of reference  and shall be given no effect in the  construction  or
interpretation of this Agreement.

     14.7.  No  Implied  Rights.  Except  as  expressly  provided  for  in  this
Agreement, nothing contained herein shall be construed as conferring any license
or other rights, by implication or estoppel,  under any patent (including design
patent and  utility  model  patent) or patent  application,  or any  copyrights,
trademarks, trade names or trade dress.

     14.8.  No Waiver.  The failure of any party  hereto at any time or times to
require  performance of any provision hereof shall in no manner affect the right
of such party at a later time to enforce the same. No waiver by any party hereto
of  any  condition,  or  of  the  breach  of  any  provision,   term,  covenant,
representation  or warranty  contained in this Agreement,  whether by conduct or
otherwise, in any one or more instances, shall be deemed to be or construed as a
further or continuing waiver of any such condition or of the breach of any other
provision, term, covenant, representation or warranty of this Agreement.

     14.9.  Publicity.  In the  absence of prior  written  approval of the other
parties hereto, no party hereto shall originate any publicity,  news release, or
other public  announcement,  written or oral,  whether to the public  press,  to
stockholders or otherwise,  relating to this Agreement,  to any amendment hereto


                                       23
<PAGE>
or activities hereunder, unless such announcement is required by law to be made.
The  party  making  any such  announcement  shall  give  the  other  parties  an
opportunity to review the announcement before it is made.

     14.10. Promotion and Advertising. Nothing contained in this Agreement shall
be construed as conferring on any party hereto any right to use in  advertising,
publicity  or other  promotional  activities  any  name,  tradename,  trademark,
service mark or other  designation  (including any contraction,  abbreviation or
simulation of any of the foregoing of any other party  hereto);  and, each party
hereto agrees not to use any  designation of any other party in any  promotional
activity  associated with this Agreement,  or with product licensed  thereunder,
without the express written approval of such other party.

     14.11.  Arbitration.  Any  dispute  arising  out  of  or  relating  to  any
provisions of this Agreement  shall be finally settled by arbitration to be held
in New York, New York, under the auspices and the current commercial arbitration
rules of the American Arbitration Association. Arbitration shall be initiated by
delivery of a notice (an "Arbitration  Notice") by any party hereto to the other
parties hereto.  Such arbitration shall be conducted by one arbitrator  mutually
selected and approved by the parties to the dispute.  If within 20 calendar days
after  receipt of the  Arbitration  Notice the parties to the  dispute  have not
agreed on a mutually acceptable arbitrator, the American Arbitration Association
in New York,  New York shall be  retained  to appoint  an  arbitrator  within 30
calendar  days after the receipt of the  Arbitration  Notice.  The  arbitrator's
authority  shall be limited to  determining  the issue or question  presented in
each instance and shall not extend to any other aspect of this  Agreement or the
parties' relationship generally. Judgment upon any award rendered may be entered
in any court having jurisdiction, or application may be made to such court for a
judicial  acceptance of the award and an order of  enforcement,  as the case may
be.

     14.12. Confidentiality.
            ----------------

     14.12.1.  As used in this Section 14.12,  "Confidential  Information" means
confidential  and  proprietary  business,  technical  or  financial  information
relating  to the  collaboration  contemplated  hereby,  including  the  Licensed
Technical   Information,   of  any  other  party   hereto   (the   "Confidential
Information").

     14.12.2.  In order to protect  the  Confidential  Information  of any party
hereto (in such capacity,  the "Disclosing  Party") that has become available to
any other party hereto (in such  capacity,  the "Receiving  Party"),  each party
hereto agrees as follows:

     (a) Each party hereto  agrees that it will make no use of any  Confidential
Information  except  in  furtherance  of  the  purposes   contemplated  by  this
Agreement.

     (b) Each party hereto  agrees that it will not,  without the prior  written
consent of the other parties  hereto,  disclose to any third party  Confidential
Information  (which for purposes of this Section  14.12.2(b)  shall  include the
terms or  existence of this  Agreement  or of the LLC  Agreement or the Services
Agreement or other matters relating to the collaboration contemplated hereby and
thereby)  received  in its  capacity as a Receiving  Party  during the  Contract
Period and for a period of five years thereafter.


                                       24
<PAGE>

     (c) Notwithstanding the foregoing:

               (i)  Each party hereto may disclose  Confidential  Information to
                    those  of  its   representatives,   employees   and   agents
                    ("Representatives")   who   have  a  need   to   know   such
                    Confidential   Information   in   relation  to  the  matters
                    discussed   herein   and  who  are  under   obligations   of
                    confidentiality  and non-use consistent with those set forth
                    herein.   Any   unauthorized   disclosure  of   Confidential
                    Information by a party's  Representatives  shall be a breach
                    by such party of this Section 14.12.

               (ii) Disclosure of  Confidential  Information is permitted to the
                    extent  that  such   disclosure  is  required   pursuant  to
                    applicable   laws,   rules  or   regulations  or  government
                    requirement  or  court  order,  provided  however,  that the
                    Receiving Party shall promptly  notify the Disclosing  Party
                    in  writing  of the  existence  or  imposition  of any  such
                    requirement or order and cooperate with the Disclosing Party
                    in seeking an appropriate protective order or other reliable
                    assurance that  confidential  treatment will be accorded the
                    Confidential Information.

     14.12.3. The provisions governing  confidentiality and non-use contained in
this Section 14.12 shall not apply to any Confidential Information which:

     (a) the Receiving  Party can  establish  was known to the  Receiving  Party
prior to disclosure under or in connection with this Agreement by the Disclosing
Party;

     (b) was in the public domain or the subject of public knowledge at the time
of disclosure under or in connection with this Agreement;

     (c) becomes  part of the public  domain or the subject of public  knowledge
through no breach by or act of default of the Receiving Party;

     (d) is  obtained  by the  Receiving  Party from a third party other than in
breach of a legal or  contractual  obligation  of  confidentiality  owed by such
third party to the Disclosing Party in respect  thereof,  the existence of which
such obligation was known or should have been known by the Receiving Party; or

     (e) the Receiving  Party can establish  was  independently  developed by it
without reference to Confidential Information received.

     14.12.4.  Termination  of this Agreement  shall not affect the  obligations
concerning  confidentiality  and non-use of the Confidential  Information as set
forth in this Section 14.12.

     14.13.  No Third  Party  Beneficiaries.  This  Agreement  is solely for the
benefit of the  parties  hereto and should not be  construed  to confer upon any
other person any remedy,  claim,  liability,  right of  reimbursement,  claim of
action or other right.


                                       25

<PAGE>

     14.14. Governing Law. This Agreement shall be interpreted,  construed,  and
governed in accordance with the laws of the State of New York, without reference
to conflict of laws principles.

     14.15.  SKICR  Agreement.   Pursuant  to  Section  III.D.4.  of  the  SKICR
Agreement,  the parties  hereto  hereby  reference  the SKICR  Agreement and all
rights  which  revert  to SKICR  upon  termination  of the SKICR  Agreement.  In
accordance with Section III.D.8.  of the SKICR  Agreement,  this Agreement shall
automatically be modified or terminated,  in whole or in part, upon any relevant
modification,  in whole or in part, of the SKICR Agreement. Such modification or
termination of this Agreement  shall be consistent with and reflect the relevant
modifications or terminations of the SKICR Agreement.

     14.16. Limitation on Liability. Notwithstanding any other provision in this
Agreement,  the sole remedy for the breach of the  representation  contained  in
Section  2.1.7  or  2.2.14   hereof,   absent   fraud,   bad  faith  or  willful
misrepresentation, is the prompt compliance with Section 3.3 hereof.

                                       26

<PAGE>




                           IN WITNESS  WHEREOF,  the  parties  hereto  have each
caused these presents to be signed by their respective
officers thereunto duly authorized.


                                      PROGENICS PHARMACEUTICALS, INC.



                                      By: /s/  Ronald Prentki
                                         Name: Ronald Prentki
                                         Title: President


                                      CYTOGEN CORPORATION



                                      By: /s/  Donald F. Crane, Jr.
                                         Name: Donald F. Crane, Jr.
                                         Title: Vice President General Counsel
                                                and Corporate Secretary


                                      PSMA DEVELOPMENT COMPANY LLC



                                      By: /s/  Donald F. Crane, Jr.
                                         Name: Donald F. Crane, Jr.
                                         Title: Vice President General Counsel
                                                and Corporate Secretary





                                                           EXHIBIT 23.1




           CONSENT OF INDEPENDENT PUBLIC ACCOUNTANTS


As independent public accountants, we hereby consent to the incorporation
by reference in this S-3 registration statement of our report dated January 29,
1999 included in CYTOGEN Corporation's Form 10-K for the year ended December 31,
1998 and to all references to our Firm included in this registration statement.


                                                       ARTHUR ANDERSEN LLP


Philadelphia, PA
      July 19, 1999



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