CYTOGEN CORP
S-8 POS, 2000-10-18
IN VITRO & IN VIVO DIAGNOSTIC SUBSTANCES
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    As filed with the Securities and Exchange Commission on October 18, 2000

                                                    Registration No. 333-27673

--------------------------------------------------------------------------------
                       SECURITIES AND EXCHANGE COMMISSION
                              WASHINGTON, DC 20549

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

                        POST-EFFECTIVE AMENDMENT NO. 1 TO
                                    FORM S-8
                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933

                               CYTOGEN CORPORATION
--------------------------------------------------------------------------------
             (Exact Name of Registrant as Specified in Its Charter)

                                    Delaware
--------------------------------------------------------------------------------
         (State or Other Jurisdiction of Incorporation or Organization)

                                   22-2322400
--------------------------------------------------------------------------------
                      (I.R.S. Employer Identification No.)

               600 College Road East CN 5308, Princeton, NJ 08540
--------------------------------------------------------------------------------
              (Address of Principal Executive Offices) (Zip Code)

      Cytogen Corporation 1988 Stock Option Plan for Non-Employee Directors
               Cytogen Corporation 1989 Employee Stock Option Plan
                 Cytogen Corporation 1989 Special Employee Plan
      Cytogen Corporation 1989 Stock Option Policy for Outside Consultants
             Cytogen Corporation 1992 Employee Stock Option Plan II
                   Cytogen Corporation 1995 Stock Option Plan
                Cytogen Corporation Employee Stock Purchase Plan

                                   ----------

                                  Cellcor, Inc.
                             1988 Stock Option Plan
                   1992 Stock Option and Restricted Stock Plan
                            1992 Director Stock Plan
                            1995 Stock Incentive Plan
--------------------------------------------------------------------------------
                            (Full Title of the Plan)

                            Catherine M. Verna, Esq.
                       Vice President and General Counsel
                               Cytogen Corporation
               600 College Road East CN 5308, Princeton, NJ 08540
--------------------------------------------------------------------------------
                     (Name and Address of Agent for Service)

                                 (609) 750-8200
--------------------------------------------------------------------------------
          (Telephone Number, Including Area Code, of Agent For Service)

                                    Copy to:

                               Raymond Thek, Esq.
                   Buchanan Ingersoll Professional Corporation
                              650 College Road East
                               Princeton, NJ 08540
                                 (609) 987-6800

<PAGE>

                                EXPLANATORY NOTE

     The Post-Effective  Amendment No. 1 to Form S-8 and the Prospectus filed by
Cytogen  Corporation (the "Company") relates to the public resale,  from time to
time, of an aggregate of 8,488,960  shares of Common Stock,  $0.01 par value per
share (the "Common Stock"),  by certain  stockholders  identified in the section
entitled "Selling  Stockholders."  Such shares have been or may be acquired upon
the exercise of stock options granted or upon stock  purchases  pursuant to: (i)
300,000 shares of Common Stock issuable pursuant to the Cytogen Corporation 1988
Stock Option Plan for  Non-Employee  Directors,  as amended  (the "1988  Cytogen
Director  Plan");  (ii) 2,100,000  shares of Common Stock  issuable  pursuant to
options previously  granted or to be granted under the Cytogen  Corporation 1989
Employee  Stock Option Plan (the "1989  Cytogen  Employee  Plan");  (iii) 20,500
shares of Common Stock issuable pursuant to options  previously granted or to be
granted under the Cytogen  Corporation  1989 Special Employee Plan (the "Cytogen
Special Employee Plan");  (iv) 100,000 shares of Common Stock issuable  pursuant
to options  previously  granted or to be granted  under the Cytogen  Corporation
1989  Stock  Option  Policy  for  Outside   Consultants  (the  "Cytogen  Outside
Consultant  Plan");  (v) 750,000  shares of Common  Stock  issuable  pursuant to
options previously  granted or to be granted under the Cytogen  Corporation 1992
Employee Stock Option Plan II, as amended (the "Cytogen 1992 Employee Plan II");
(vi) 4,502,635  shares of Common Stock issuable  pursuant to options  previously
granted or to be granted under the Cytogen  Corporation  1995 Stock Option Plan,
as amended (the "1995  Cytogen  Stock Option  Plan");  (vii)  500,000  shares of
Common Stock issuable  pursuant to options  previously  granted or to be granted
under the Cytogen Corporate  Employee Stock Purchase Plan (the "Cytogen Employee
Stock  Purchase  Plan");  and (viii)  215,825  shares of Common  Stock  issuable
pursuant to the Cellcor,  Inc. 1988 Stock Option Plan (the "1988 Cellcor  Option
Plan"),  1992 Stock Option and  Restricted  Stock Plan (the "1992  Cellcor Stock
Option Plan"),  1992 Director Stock Plan (the "1992 Cellcor Director Plan"), and
1995 Stock Incentive Plan (the "1995 Cellcor Incentive Plan").  The 1988 Cytogen
Director  Plan,  1989 Cytogen  Employee  Plan,  Cytogen  Special  Employee Plan,
Cytogen  Outside  Consultant  Plan,  Cytogen 1992 Employee Plan II, 1995 Cytogen
Stock Option Plan,  Cytogen  Employee Stock  Purchase Plan,  1988 Cellcor Option
Plan,  1992 Cellcor  Stock Option Plan,  1992 Cellcor  Director  Plan,  and 1995
Cellcor Incentive Plan are collectively  referred to hereinafter as the "Plans."
The shares issuable  pursuant to the Plans have been registered on the following
Registration Statements:

          o    Form S-8  filed  with  the  Securities  and  Exchange  Commission
               (the  "SEC") on December 8, 1986  registering  700,000  shares of
               Common Stock of the Company,  to be offered  pursuant to the 1989
               Cytogen Employee Plan;

          o    Form  S-8  filed  with  the SEC on  August  18,  1989 registering
               the following Common Stock of the Company:  (i) 100,000 shares to
               be offered  pursuant  to the 1988  Cytogen  Director  Plan;  (ii)
               1,400,000  shares  to be  offered  pursuant  to the 1989  Cytogen
               Employee Plan;

                                      (i)
<PAGE>

          o    and  (iii) 20,500 shares to  be offered pursuant to  the  Cytogen
               Special Employee Plan;

          o    Form S-8 filed  with the SEC on  September  29,  1992 registering
               120,000  shares of Common  Stock of the  Company,  to be  offered
               pursuant to the Cytogen 1992 Employee Plan II;

          o    Form S-8  filed  with  the SEC on  January  12,  1993 registering
               630,000  shares of Common  Stock of the  Company,  to be  offered
               pursuant to the Cytogen 1992 Employee Plan II, as amended;

          o    Form  S-8  filed  with the  SEC  via  EDGAR on  October  10, 1995
               registering  2,402,635 shares of Common Stock of the Company,  to
               be offered pursuant to the 1995 Cytogen Stock Option Plan;

          o    Form  S-8  filed  with the  SEC via  EDGAR on  January  26, 1996,
               registering  606,952 shares of Common Stock of the Company, to be
               offered  pursuant  to the  1988  Cellcor  Option  Plan,  the 1992
               Cellcor Stock Option Plan, the 1992 Cellcor Director Plan and the
               1995 Cellcor Incentive Plan;

          o    Form   S-8  filed  with  the  SEC  via  EDGAR  on  May 29,  1996,
               registering  200,000 shares of Common Stock of the Company, to be
               offered pursuant to the 1988 Cytogen Director Plan;

          o    Form   S-8  filed  with  the   SEC  via  EDGAR  on  May 29, 1996,
               registering  2,100,000 shares of Common Stock of the Company,  to
               be offered pursuant to the 1995 Cytogen Stock Option Plan; and

          o    Form  S-8  filed  with  the  SEC  via  EDGAR  on  May  23,  1997,
               registering  500,000 shares of Common Stock of the Company, to be
               offered pursuant to the Cytogen Employee Stock Purchase Plan.


                                      (ii)
<PAGE>

                                   PROSPECTUS

                  S-3 Reoffer Prospectus dated October 18, 2000

                               CYTOGEN CORPORATION
               600 College Road East, CN 5308, Princeton, NJ 08540


                        Three Hundred Thousand (300,000)
               Shares of Common Stock Issued or Issuable under the
   Cytogen Corporation 1988 Stock Option Plan for Non-Employee Directors, as
                                     amended

                  Two Million One Hundred Thousand (2,100,000)
               Shares of Common Stock Issued or Issuable under the
               Cytogen Corporation 1989 Employee Stock Option Plan

                      Twenty Thousand Five Hundred (20,500)
               Shares of Common Stock Issued or Issuable under the
                 Cytogen Corporation 1989 Special Employee Plan

                         One Hundred Thousand (100,000)
               Shares of Common Stock Issued or Issuable under the
      Cytogen Corporation 1989 Stock Option Policy for Outside Consultants

                     Seven Hundred Fifty Thousand (750,000)
               Shares of Common Stock Issued or Issuable under the
       Cytogen Corporation 1992 Employee Stock Option Plan II, as amended

   Four Million Five Hundred Two Thousand Six Hundred Thirty Five (4,502,635)
               Shares of Common Stock Issued or Issuable under the
             Cytogen Corporation 1995 Stock Option Plan, as amended

                         Five Hundred Thousand (500,000)
               Shares of Common Stock Issued or Issuable under the
                Cytogen Corporation Employee Stock Purchase Plan

        Two Hundred Fifteen Thousand Eight Hundred Twenty Five (215,825)
               Shares of Common Stock Issued or Issuable under the
                      Cellcor, Inc. 1988 Stock Option Plan
            Cellcor, Inc. 1992 Stock Option and Restricted Stock Plan
                     Cellcor, Inc. 1992 Director Stock Plan
                    Cellcore, Inc. 1995 Stock Incentive Plan

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

     This  Prospectus  relates  to the  public  resale,  from  time to time,  of
8,488,960  shares of our Common  Stock (the  "Shares")  by certain  stockholders
identified below in the section entitled "Selling Stockholders." The Shares have
been or may be acquired upon the exercise of stock options granted or upon stock
purchases pursuant to the Plans. Options or Shares may be issued

<PAGE>

under the Plans in  amounts  and to  persons  not  presently  known to us.  Such
information, when known, may be included in an amendment to this Prospectus.

     We will receive no proceeds from the sale by the Selling  Stockholders  (as
defined below) of the Shares covered by this Prospectus.

     We have not entered into any  underwriting  arrangements in connection with
the sale of the Shares.  The Shares may be sold from time to time by the Selling
Stockholders or by permitted  pledgees,  donees,  transferees or other permitted
successors  in interest  and may be made on the Nasdaq  National  Market at such
prices and upon such terms as are then  prevailing  or at prices  related to the
then current market price, or in negotiated transactions.

     Our Common Stock is traded on the Nasdaq  National  Market under the symbol
"CYTO".  On October 6, 2000, the last reported sale price of our Common Stock on
the Nasdaq National Market was $5.938 per share.

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

     SEE "RISK  FACTORS"  BEGINNING ON PAGE 5 TO READ ABOUT CERTAIN OF THE RISKS
THAT YOU SHOULD CONSIDER BEFORE PURCHASING SHARES OF OUR COMMON STOCK.

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

     NEITHER THE  SECURITIES AND EXCHANGE  COMMISSION  NOR ANY STATE  SECURITIES
COMMISSION  HAS  APPROVED OR  DISAPPROVED  THESE  SECURITIES  OR PASSED UPON THE
ADEQUACY OR ACCURACY OF THIS PROSPECTUS. ANY REPRESENTATION TO THE CONTRARY IS A
CRIMINAL OFFENSE.

                The date of this Prospectus is October 18, 2000.


<PAGE>

                               CYTOGEN CORPORATION

                                TABLE OF CONTENTS
                                -----------------

                                                                           Page
                                                                           ----

About Cytogen Corporation...............................................    3

Risk Factors............................................................    5

Use of Proceeds.........................................................    22

Selling Stockholders....................................................    22

Plan of Distribution....................................................    24

Legal Matters...........................................................    25

Experts.................................................................    25

Information Incorporated by Reference...................................    25

Where You Can Find More Information.....................................    27

Indemnification of Directors and Officers...............................    27

Securities and Exchange Commission Position on Indemnification
  for Securities Act Liabilities........................................    29


                                      -2-
<PAGE>

                            ABOUT CYTOGEN CORPORATION

     Cytogen is an  established  biopharmaceutical  company  with two  principal
lines of business,  oncology and  proteomics.  We are extending our expertise in
antibodies and molecular  recognition  to the  development of new products and a
proteomics-driven  drug discovery  platform.  We have  established a pipeline of
product  candidates  based upon our proprietary  antibody and prostate  specific
membrane antigen,  or PSMA,  technologies.  We are also developing a proprietary
protein  pathway  database  as a drug  discovery  and  development  tool for the
pharmaceutical and biotechnology industries.

     Our cancer  management  franchise is currently  comprised of three marketed
FDA-approved  products:  ProstaScint(R),  used to image the extent and spread of
prostate cancer; OncoScint CR/OV(R),  marketed as a diagnostic imaging agent for
colorectal  and  ovarian  cancer and  Quadramet(R),  marketed  for the relief of
cancer-related  bone pain. We are  extending  our cancer  pipeline by exploiting
PSMA, which we exclusively licensed from Memorial Sloan-Kettering Cancer Center.
PSMA is a unique  antigen highly  expressed in prostate  cancer cells and in the
neovasculature of a variety of other solid tumors,  including  breast,  lung and
colon. We are developing our PSMA technology as part of our approach to offering
a full range of prostate cancer management  products and services throughout the
progression  of  the  disease,   including  gene-based  immunotherapy  vaccines,
antibody-delivered  therapeutic  compounds  and novel  assays for  detection  of
primary  prostate cancer.  We also plan to apply our PSMA technology,  including
therapeutics and in vitro  diagnostics,  toward other types of cancer based upon
our experience in prostate  cancer.  Our in vivo  immunotherapeutic  development
program is being conducted in collaboration with Progenics Pharmaceuticals.

     Proteomics  is the study of the  expression  and  interaction  of proteins.
Genomics is the study and identification of an organism's genetic makeup.  While
genomics provides  important  information  regarding genetic makeup, it does not
directly   provide   information   regarding   protein   functions   or  protein
interactions.  However, genomics data can prove useful in proteomics research as
a source of obtaining  complete protein sequences of ligands we have identified.
Public   availability  of  this  genomics   information   allows  for  effective
integration in our database of public and proprietary information. We recognized
in our past research that the key to  understanding  or developing  the means to
intervene in diseases was primarily based on understanding  protein interactions
rather  than  only  through  the use or study of  genomics.  We  undertook  this
approach on our own initiative and with our own funds.  Our proteomics  program,
under development by our subsidiary,  AxCell Biosciences Corporation, is focused
on the identification of protein interaction and signaling pathways within cells
as relating to disease processes.

     Cytogen  markets  and  sells  ProstaScint  and  OncoScint  through  its own
twenty-five  member  sales and  marketing  organization.  Cytogen has  developed
expertise  in  sales  and   marketing  of  its  products   through   urologists,
oncologists,  radiation  oncologists  and  nuclear  medicine.  Cytogen  has also
developed educational programs that can be accessed through the world wide web.

                                      -3-
<PAGE>

     We  utilize  our  proprietary   proteomics   technology  to  map  selective
protein-protein   interactions   and  to   develop  a   database,   called   the
Inter-Functional  Proteomic  Database,  or IFP  Database,  which  includes  data
relating  to  protein   signaling   pathways   linked  to  a  variety  of  other
bioinformatic  data.  The IFP  Database  is  designed  to  permit  customers  to
integrate existing databases, both public and proprietary,  with our proprietary
data to create a 'virtual  laboratory'  on the computer  desktop of  researchers
involved in drug discovery.  We believe this database has significant  potential
commercial value to the pharmaceutical  and biotechnology  industries as a means
of expediting drug target  identification,  validation,  screen  development and
lead compound  optimization faster and cheaper than with current  methodologies.
These proprietary  technologies are designed to provide a platform from which we
can quickly and  cost-effectively  determine  protein-protein  interactions  and
build pathways of  intracellular  signaling data. Our IFP Database also offers a
consolidated platform to enable statistical and mathematical modeling of complex
protein pathways.

     We are a Delaware corporation.  Our principal executive offices are located
at 600 College Road East CN 5308,  Princeton,  NJ 08540 and our telephone number
at that location is (609) 750-8200.

     All  references  to  "we,"  "us,"  "our,"  "Company"  or  Cytogen  in  this
Prospectus means Cytogen Corporation and its subsidiaries.

                                      -4-
<PAGE>

                                  RISK FACTORS

     INVESTING  IN OUR COMMON STOCK  INVOLVES A HIGH DEGREE OF RISK.  YOU SHOULD
CAREFULLY  CONSIDER THE  FOLLOWING  RISKS  TOGETHER  WITH THE OTHER  INFORMATION
INCLUDED OR  INCORPORATED BY REFERENCE IN THIS PROSPECTUS IN YOUR DECISION AS TO
WHETHER  TO  INVEST  IN OUR  COMMON  STOCK.  IF ANY OF THE  FOLLOWING  RISKS  OR
UNCERTAINTIES  ACTUALLY OCCUR, OUR BUSINESS,  FINANCIAL  CONDITION AND OPERATING
RESULTS COULD BE  SIGNIFICANTLY  AND ADVERSELY  AFFECTED.  IF THAT HAPPENS,  THE
PRICE OF OUR COMMON STOCK COULD DECLINE,  AND YOU COULD LOSE ALL OR PART OF YOUR
INVESTMENT.

WE HAVE A HISTORY OF OPERATING  LOSSES AND AN ACCUMULATED  DEFICIT AND EXPECT TO
INCUR LOSSES IN THE FUTURE.

     We have a history of  operating  losses since our  inception.  We had a net
loss of $4,548,000  during the six months ended June 30, 2000. We had net income
of  $729,000  during the year ended  December  31, 1999 which  included  certain
non-operating  gains.  We had net  losses of  $13,152,000  during the year ended
December 31, 1998 and  $30,712,000  during the year ended  December 31, 1997. We
had an  accumulated  deficit of  $305,831,000  as of June 30, 2000.  In order to
develop and commercialize our technologies,  particularly our proteomics program
and our prostate specific membrane antigen, or PSMA, technology,  and expand our
oncology products, we expect to incur significant increases in our expenses over
the  next  several  years.  As a  result,  we may need to  generate  significant
additional revenue to become profitable.

     Our ability to  generate  and sustain  significant  additional  revenues or
achieve  profitability will depend upon the factors discussed  elsewhere in this
"Risk  Factors"  Section,  as well as  numerous  other  factors  outside  of our
control, including:

     o    development of  competing  products  that  are more  effective or less
          costly then our own;

     o    our  ability  to, develop  and  commercialize  our  own  products  and
          technologies; and

     o    our  ability to achieve increased  sales for our existing products and
          sales for any new products.

     As a  result,  we may  never be able to  generate  or  sustain  significant
additional revenue or achieve profitability.

WE ARE HEAVILY  DEPENDENT ON MARKET  ACCEPTANCE OF PROSTASCINT AND QUADRAMET FOR
NEAR-TERM REVENUES.

     ProstaScint  and  Quadramet  are  expected  to  account  for a  significant
percentage  of our  product-related  revenues  in the near  future.  For the six
months ended June 30, 2000,  revenues

                                      -5-
<PAGE>

from ProstaScint and Quadramet  accounted for  approximately  93% of our product
related revenues.

     Because  these  products  contribute  the  majority of our  product-related
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:

     o    health care providers, such as hospitals and physicians; and

     o    third-party payors,  including  Medicare, Medicaid,  private insurance
          carriers and health maintenance organizations.

     Our customers,  including  technologists and physicians,  must successfully
complete our Partners in  Excellence  Program,  or PIE  Program,  a  proprietary
training program designed to promote the correct  acquisition and interpretation
of  ProstaScint  images.  This  product is  technique  dependent  and requires a
learning  commitment on the part of users.  We cannot assure you that additional
physicians will make this commitment or otherwise accept this product as part of
their treatment practices.

     Berlex Laboratories, Inc. markets Quadramet in the United States through an
agreement that we entered into in October 1998. We cannot assure you that Berlex
will be able to successfully market Quadramet or that this agreement will result
in  significant  revenues  for us.  We  recently  obtained  marketing  rights to
Quadramet in Canada,  but have not yet implemented a selling program.  We cannot
assure you that Quadramet can be marketed effectively in Canada, or that it will
contribute significantly to our revenues.

     We  cannot  assure  you that  Quadramet  will be  approved  for  additional
indications,  due to  uncertainty  as to efficacy or safety for other  purposes,
regulatory  obstacles  and  physician  preferences  for  existing  or  competing
practices.

     Accordingly,  we cannot  assure  you that  ProstaScint  or  Quadramet  will
achieve  market  acceptance  on a timely  basis,  or at all. If  ProstaScint  or
Quadramet  do not  achieve  broader  market  acceptance,  we may  not be able to
generate sufficient revenue to become profitable.

WE HAVE EXPERIENCED 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:

     o    variations in revenue from sales of and royalties from our products;

     o    timing of  regulatory  approvals  and  other regulatory  announcements
          relating to our products;

     o    variations in our marketing, manufacturing and distribution channels;

                                      -6-
<PAGE>

     o    timing  of the acquisition and successful integration of complementary
          products and technologies;

     o    timing  of new product  announcements  and introductions by us and our
          competitors; and

     o    product obsolescence resulting from new product introductions by us or
          our competitors.

     Many of these factors 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 decline.

WE MAY NEED TO RAISE ADDITIONAL CAPITAL WHICH MAY NOT BE AVAILABLE.

     We have incurred  negative cash flows from operations since  inception.  We
have  expended,  and will  need to  continue  to  expend,  substantial  funds to
complete our planned product development  efforts,  including our proteomics and
PSMA programs. Our future capital requirements and the adequacy of our available
funds depend on many factors, including:

     o    successful commercialization of our products;

     o    acquisition of complementary products and technologies;

     o    magnitude, scope and results of our product development efforts;

     o    progress of preclinical studies and clinical trials;

     o    progress toward regulatory approval for our products;

     o    costs of filing,  prosecuting, defending  and enforcing  patent claims
          and other intellectual property rights;

     o    competing technological and market developments; and

     o    expansion  of   strategic  alliances  for  the  sale,  marketing   and
          distribution of our products.

     We may raise additional capital through public or private equity offerings,
debt  financings  or  additional   collaborations  and  licensing  arrangements.
Additional  financing  may  not be  available  to us when we  need  it,  or,  if
available,  we may not be able to obtain  financing on terms  favorable to us or
our stockholders.  If we raise additional  capital by issuing equity securities,
the issuance will result in ownership dilution to our stockholders.  If we raise
additional funds through  collaborations and licensing  arrangements,  we may be
required  to  relinquish  rights  to

                                      -7-
<PAGE>

certain  of our  technologies  or product  candidates  or to grant  licenses  on
unfavorable  terms.  If we relinquish  rights or grant  licenses on  unfavorable
terms,  we may not be able to develop  or market  products  in a manner  that is
profitable  to us. If adequate  funds are not  available,  we may not be able to
conduct  research  activities,  preclinical  studies,  clinical  trials or other
activities  relating to the  successful  commercialization  of our products on a
timely  basis,   if  at  all,  with  the  result  that  our  business  could  be
significantly and adversely affected.

OUR  PRODUCTS,   GENERALLY,   ARE  IN  THE  EARLY  STAGES  OF  DEVELOPMENT   AND
COMMERCIALIZATION AND WE MAY NEVER ACHIEVE THE GOALS OF OUR BUSINESS PLAN.

     We began  operations  in 1980 and have been  engaged  primarily in research
directed toward the development,  commercialization and marketing of products to
improve  diagnosis and treatment of cancer and other disease.  In December 1992,
we introduced for commercial use our ONCOSCINT  imaging agent.  In October 1996,
we introduced for commercial use our  ProstaScint  imaging agent. In March 1997,
we introduced  for  commercial  use our  Quadramet  therapeutic  product.  These
products have not yet achieved significant commercial success. In 1998, we began
a  restructuring  of our  company  to focus on the  development  of our PSMA and
proteomics technologies as well as the marketing of these existing products.

     Early last year, we completed our  restructuring.  Our PSMA and  proteomics
technologies are still in the early stages of development. We have only recently
begun to incorporate our proteomics technology into commercialized  products. We
may be unable  to  continue  to  successfully  develop  or  commercialize  these
products and technologies.

     Our business is therefore  subject to the risks inherent in the development
of an early stage biopharmaceutical business enterprise, such as the need:

     o    to obtain sufficient capital to support the expenses of developing our
          technology and commercializing our products;

     o    to ensure that our products are safe and effective;

     o    to obtain regulatory approval for the use and sale of our products;

     o    to  manufacture  our  products  in  sufficient  quantities  and  at  a
          reasonable cost;

     o    to develop a sufficient market for our products; and

     o    to  attract  and  retain qualified  management, sales,  technical  and
          scientific staff.

     The problems frequently encountered using new technologies and operating in
a competitive  environment also may affect our business.  If we fail to properly
address these risks and attain our business  objectives,  our business  could be
significantly and adversely affected.

                                      -8-
<PAGE>

OUR PROTEOMICS PROGRAM IS AT AN EARLY STAGE OF DEVELOPMENT.

     We have developed and intend to continue to develop our proteomics program.
This  technology  involves new approaches to drug research and  development  and
remains commercially unproven. Our technology and development focus is primarily
directed toward offering an  infrastructure  to companies for the development of
drugs  to  treat  a  variety  of  complex  human  diseases.   There  is  limited
understanding  generally  relating to the role of proteins in diseases,  and few
products  based on  protein  interaction  discoveries  have been  developed  and
commercialized.  Even if our proteomics program is successful in identifying and
validating  biological  targets,  there is no certainty that we or our customers
will be able to develop or commercialize products to improve human health.

     Our  technology  program  for  proteomics  is still in the early  stages of
development.  We may not be able to populate our IFP DATABASE  with  information
that is useful to potential  customers in a timely  manner.  Even if we complete
and develop  successfully our proteomics  technology,  the technology may not be
accepted by, or be useful to, our potential customers.

     In addition,  the success of our proteomics technology will depend upon our
ability to use software  tools to generate data that relates  protein  signaling
pathways to a variety of other  bioinformatic data. Because of the complexity of
this  data,  we may not be able to detect  and  remedy  any  design  defects  or
software errors in our existing or future technologies, including databases.

     We may not be  successful  in  addressing  or  mitigating  these  risks and
uncertainties,  and, if we are not,  our  business  could be  significantly  and
adversely affected.

THERE IS A LIMITED MARKET FOR OUR POTENTIAL PROTEOMICS PRODUCTS.

     Due to the  specialized  nature  and  anticipated  cost  of our  proteomics
technology  and  services,  there are a limited  number  of  pharmaceutical  and
biotechnology  companies that are potential customers.  In addition,  demand for
our proteomics technology and services is limited because:

     o    our potential customers may decide to conduct in-house research rather
          than subscribe to our IFP database;

     o    our competitors may offer similar services at competitive prices;

     o    we  may  not be able  to  service  satisfactorily  the  needs  of  our
          potential or actual customers;

     o    others  may   publicly  disclose  or  patent  proprietary  information
          contained  in our  IFP  Database  (including  information  related  to
          protein  signaling  pathways  or target  candidates)  or  relating  to
          prostate antigens or antibodies;

                                      -9-
<PAGE>

     o    technological innovations  may be  discovered that  are more  advanced
          than those used by or available to us; and

     We may not be  successful  in  addressing  or  mitigating  these  risks and
uncertainties,  and, if we are not,  our  business  could be  significantly  and
adversely affected.

OUR  PSMA PRODUCT  DEVELOPMENT PROGRAM  IS NOVEL AND,  CONSEQUENTLY,  INHERENTLY
RISKY.

     We are  subject  to the risks of failure  inherent  in the  development  of
product  candidates  based on new  technologies,  including our PSMA technology.
These risks include the possibility that:

     o    the technologies we use will not be effective;

     o    our product candidates will be unsafe;

     o    our  product candidates will fail  to receive the necessary regulatory
          approvals;

     o    our product candidates will be hard to manufacture on a large scale or
          will be uneconomical to market; and

     o    we  will not successfully  overcome technological challenges presented
          by our potential new products.

     Our objectives  include  developing our PSMA  technology  into novel cancer
therapeutics,   including  a  cancer  vaccine.  To  our  knowledge,   no  cancer
therapeutic  vaccine has been demonstrated  effective or approved for marketing.
Our other research and development  programs involve  similarly novel approaches
to human  therapeutics.  Consequently,  there is no precedent for the successful
commercialization  of therapeutic  products based on our PSMA  technologies.  We
cannot assure you that any products will be successfully developed from our PSMA
technology.  If we fail to develop such products for the reasons set forth above
or for any other  reason,  our business  could be  significantly  and  adversely
affected.

ALL OF OUR POTENTIAL  ONCOLOGY  PRODUCTS WILL BE SUBJECT TO THE RISKS OF FAILURE
INHERENT IN THE  DEVELOPMENT OF DIAGNOSTIC OR THERAPEUTIC  PRODUCTS BASED ON NEW
TECHNOLOGIES.

     Product development for cancer treatment involves a high degree of risk. We
cannot assure you that the product  candidates we develop,  pursue or offer will
prove to be safe and effective, will receive the necessary regulatory approvals,
will not be precluded by proprietary  rights of third parties 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.  We cannot assure you that we will
not  experience   difficulties  that  could  delay  or  prevent  the  successful
development, introduction and marketing of new products.

                                      -10-
<PAGE>

     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.  We
cannot  assure you that 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.
Clinical trials or marketing of any potential diagnostic or therapeutic products
may expose us to liability claims for the use of these diagnostic or therapeutic
products.  We may not be able to  obtain  product  liability  insurance  or,  if
obtained,  sufficient  coverage may not be available  at a reasonable  cost.  In
addition,  as we develop diagnostic or therapeutic products internally,  we will
have to make  significant  investments  in  diagnostic  or  therapeutic  product
development,  marketing, sales and regulatory compliance resources. We will also
have to  establish  or  contract  for the  manufacture  of  products,  including
supplies of drugs used in clinical trials,  under the current Good Manufacturing
Practices  of the FDA. We also cannot  assure you 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 harmful effect on our ability to develop the products in our pipeline. If
we are unable to develop and commercialize products on a timely basis or at all,
our business could be significantly and adversely affected.

COMPETITION IN OUR FIELD IS INTENSE AND LIKELY TO INCREASE.

     We face, and will continue to face, intense competition from one or more of
the following entities:

     o    pharmaceutical companies;

     o    biotechnology companies;

     o    bioinformatics companies;

     o    diagnostic companies;

     o    academic and research institutions; and

     o    government agencies.

     All of our lines of business are subject to  significant  competition  from
organizations  that are pursuing  technologies and products that are the same as
or similar to our technology and

                                      -11-
<PAGE>

products.  Many of the  organizations  competing  with us have  greater  capital
resources,   research  and  development  staffs  and  facilities  and  marketing
capabilities.

     Before we recover  development  expenses for our products and technologies,
the products or technologies  may become  obsolete as a result of  technological
developments  by us or others.  Our products  could also be made obsolete by new
technologies  which are less expensive or more effective.  We may not be able to
make the enhancements to our technology  necessary to compete  successfully with
newly  emerging  technologies  and  failure  to do so  could  significantly  and
adversely affect our business.

WE RELY HEAVILY 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
sale,  marketing,   distribution  and  manufacture  of  our  products,   product
candidates and technologies:

     o    license  from  The  Dow Chemical  Company  relating to  the  Quadramet
          technology;

     o    sub-license and  marketing agreement  with  Berlex  Laboratories, Inc.
          relating to the  Quadramet  technology  which we licensed from The Dow
          Chemical Company;

     o    agreement  for manufacture of Quadramet  by The DuPont Pharmaceuticals
          Company  (formerly  the  radiopharmaceuticals  division  of The DuPont
          Merck Company);

     o    marketing  and  platform  development  agreement  with  Informax, Inc.
          related to our proteomics program;

     o    joint  venture with  Progenics Pharmaceuticals for  the development of
          PSMA for in vivo immunotherapy for prostate and other cancers; and

     o    licensing  agreement with Molecular  Staging for technology to be used
          in  developing  in vitro  diagnostic  tests  using  PSMA and  prostate
          specific antogen, or PSA.

     Because  our  collaborative  partners  are  responsible  for certain of our
sales, marketing,  manufacturing and distribution  activities,  these activities
are outside our direct  control.  We cannot  assure you that our  partners  will
perform their  obligations under these agreements with us. In the event that our
collaborative  partners  do not  successfully  market and sell our  products  or
breach  their  obligations  under  our  agreements,  our  products  may  not  be
commercially successful,  any success may be delayed and new product development
could be inhibited with the result that our business could be significantly  and
adversely affected.

                                      -12-
<PAGE>

OUR BUSINESS  COULD BE HARMED IF OUR  COLLABORATIVE  ARRANGEMENTS  EXPIRE OR ARE
TERMINATED EARLY.

     We  cannot  assure  you  that we will be  able  to  maintain  our  existing
collaborative  arrangements.  If they expire or are terminated, we cannot assure
you that they will be  renewed or that new  arrangements  will be  available  on
acceptable  terms,  if at all. In  addition,  we cannot  assure you that any new
arrangements or renewals of existing  arrangements will be successful,  that the
parties to any new or renewed  agreements  will perform  adequately  or that any
former or potential collaborators will not compete with us.

     We cannot assure you 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.

THE  TERMINATION  OF ONE OR MORE LICENSE  AGREEMENTS  THAT ARE  IMPORTANT IN THE
MANUFACTURE  OF OUR CURRENT  PRODUCTS AND NEW PRODUCT  RESEARCH AND  DEVELOPMENT
ACTIVITIES WOULD HARM OUR BUSINESS.

     We are a party to  license  agreements  under  which we have  rights to use
technologies  owned by other companies in the manufacture of our products and in
our  proprietary  research,  development  and  testing  processes.  We  are  the
exclusive  licensee  of  certain  patents  and patent  applications  held by the
University of North Carolina at Chapel Hill covering part of the technology used
in the proteomics program and of certain patents and patent applications held by
the  Memorial  Sloan-Kettering  Institute  covering  PSMA.  We  depend  upon the
enforceability  of our license  with The Dow  Chemical  Company  with respect to
Quadramet. If the licenses were terminated,  we may not be able to find suitable
alternatives to this technology on a timely basis or on reasonable  terms, if at
all. The loss of the right to use these technologies that we have licensed would
significantly and adversely affect our business.

WE HAVE LIMITED SALES, MARKETING AND DISTRIBUTION CAPABILITIES FOR OUR PRODUCTS.

     We have only recently  established a sales force and have limited  internal
sales,  marketing and distribution  capabilities for our products.  We depend on
Berlex Laboratories,  Inc. for the sale, marketing and distribution of Quadramet
in the United  States.  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 may be significantly and
adversely affected.

THERE ARE RISKS ASSOCIATED WITH THE MANUFACTURE OF OUR PRODUCTS.

     If we are to be  successful,  our  products  will  have to be  manufactured
either  internally  or through  third-party  manufacturers  in  compliance  with
regulatory requirements and at costs acceptable to us. We cannot assure you that
we  will  be able  to  continue  to  manufacture,  arrange

                                      -13-
<PAGE>

for manufacture on reasonable terms 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,  we will not be able to
successfully  commercialize  our products and our business may be  significantly
and adversely affected.

     Quadramet is  manufactured  by DuPont  pursuant to an  agreement  with both
Berlex and Cytogen. Some components of Quadramet,  particularly  Samarium153 and
EDTMP, are provided to DuPont by outside  suppliers.  Due to radioactive  decay,
Samarium153 must be produced on a weekly basis.  DuPont obtains its requirements
for Samarium153 from one supplier.  Alternative sources for these components may
not be readily  available.  On one  occasion,  DuPont was unable to  manufacture
Quadramet  on a timely  basis due to the  failure  of its  supplier  to  provide
Samarium153.  If DuPont cannot obtain sufficient quantities of the components on
commercially  reasonable  terms,  or in a timely  manner,  it would be unable to
manufacture  Quadramet  on a timely and  cost-effective  basis and our  business
could be significantly and adversely affected.

     We and our  third-party  manufacturers  are required to adhere to US Food &
Drug  Administration  regulations  setting forth  requirements  for current Good
Manufacturing  Practices,  or 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 are
monitored  through  periodic  inspections  and market  surveillance by state and
federal  agencies,  including  the  FDA,  and by  comparable  agencies  in other
countries.  Failure  of  our  third-party  manufacturers  or us 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 any of which could significantly and adversely affect
our business.

FAILURE OF CONSUMERS TO OBTAIN ADEQUATE  REIMBURSEMENT  FROM THIRD-PARTY  PAYORS
COULD LIMIT MARKET ACCEPTANCE AND AFFECT PRICING OF OUR PRODUCTS.

     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.  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 care
increases  possible  pressure  on  pricing  of these  products.  While we cannot
predict whether these  legislative or regulatory  proposals will be adopted,  or
the effects  these  proposals or managed care efforts may have on our  business,
the  announcement  of these  proposals  and the  adoption of these  proposals or
efforts  could affect our stock price or our  business.  Further,  to the extent
these  proposals or efforts have an adverse  effect on other  companies that are
our prospective corporate partners, our ability to establish necessary strategic
alliances may be harmed.

     Sales of our products depend in part on  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.  We cannot assure you that our products will be
considered  cost-effective  and that reimbursement to consumers will

                                      -14-
<PAGE>

continue to be available, or will be sufficient to allow us to sell our products
on a  competitive  basis.  Approval  of  our  products  for  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.  If we  cannot  secure  adequate  third-party
reimbursement  for  our  products,  our  business  could  be  significantly  and
adversely affected.

IF WE ARE UNABLE TO COMPLY WITH APPLICABLE GOVERNMENTAL REGULATIONS,  WE MAY NOT
BE ABLE TO CONTINUE OUR OPERATIONS.

     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. We
may be slow to adapt, or we may never adapt to changes in existing  requirements
or  adoption  of new  requirements  or  policies.  Our  failure  to comply  with
regulatory  requirements  could  subject  us to  enforcement  action,  including
product seizures, recalls,  withdrawal of clearances or approvals,  restrictions
on or injunctions  against  marketing our products based on our technology,  and
civil and criminal penalties.  We cannot assure you 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  create  an  unsustainable  burden  on our
business.

     Numerous federal, state and local governmental authorities, principally the
FDA,  and  similar  regulatory   agencies  in  other  countries,   regulate  the
preclinical testing, clinical trials, manufacture and promotion of any compounds
or agents 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.

     The regulatory risks we face also include the following:

     o    any compound or agent we or our  collaborative  partners  develop must
          receive regulatory agency approval before it may be marketed as a drug
          in a particular country;

     o    the  regulatory  process,  which  includes  preclinical  testing   and
          clinical  trials of each  compound or agent in order to establish  its
          safety and  efficacy,  varies from  country to country,  can take many
          years and requires the expenditure of substantial resources;

     o    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.

                                      -15-
<PAGE>

          We cannot assure you that such  approvals will be obtained on a timely
          basis, or at all;

     o    data obtained from preclinical and clinical activities are susceptible
          to  varying  interpretations  which  could  delay,  limit  or  prevent
          regulatory agency approval; and

     o    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.  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.

     We cannot assure you that, even after this time and expenditure, regulatory
agency  approvals will be obtained for any compound or agent  developed by or in
collaboration with us. Moreover,  regulatory agency approval for a drug or agent
may entail  limitations  on the  indicated  uses 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 US Food,  Drug and  Cosmetics  Act  requires  (i) that our  products be
manufactured in FDA registered  facilities subject to inspection,  and (ii) that
we  comply  with  cGMP,  which  imposes  certain  procedural  and  documentation
requirements   upon  us  and  our   manufacturing   partners   with  respect  to
manufacturing  and  quality  assurance  activities.  If we or our  manufacturing
partners  do not  comply  with cGMP we may be subject  to  sanctions,  including
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.

WE DEPEND ON ATTRACTING AND RETAINING KEY PERSONNEL.

     We are highly  dependent on the  principal  members of our  management  and
scientific  staff.  The  loss of their  services  might  significantly  delay or
prevent the  achievement  of development  or strategic  objectives.  Our success
depends  on our  ability  to retain  key  employees  and to  attract  additional
qualified employees.  Competition for personnel is intense, and we cannot assure
you that we will be able to retain  existing  personnel  or  attract  and retain
additional highly qualified employees in the future.

                                      -16-
<PAGE>

     We have an  employee  retention  agreement  with our  President  and  Chief
Executive Officer, H. Joseph Reiser,  Ph.D., which provides for vesting of stock
options  for the  purchase  of shares of our  Common  Stock  based on  continued
employment and on the achievement of performance objectives defined by the board
of directors.  We do not have similar  retention  agreements  with our other key
personnel.  If we are unable to hire and retain personnel in key positions,  our
business  could  be  significantly  and  adversely   affected  unless  qualified
replacements can be found.

OUR  BUSINESS  EXPOSES  US TO  POTENTIAL  LIABILITY  CLAIMS  THAT MAY EXCEED OUR
FINANCIAL  RESOURCES,  INCLUDING  OUR  INSURANCE  COVERAGE,  AND MAY LEAD TO THE
CURTAILMENT OR TERMINATION OF OUR OPERATIONS.

     Our business is subject to product liability risks inherent in the testing,
manufacturing  and marketing of our products.  We cannot assure you that product
liability  claims will not be  asserted  against  us, our  collaborators  or our
licensees. While we currently maintain product liability insurance in amounts we
believe are  adequate,  we cannot assure you 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,  we cannot  assure  you that we will be able to
avoid significant  product liability claims and adverse publicity.  If liability
claims  against  us exceed  our  financial  resources  we may have to curtail or
terminate our operations.

OUR BUSINESS INVOLVES ENVIRONMENTAL RISKS THAT MAY RESULT IN LIABILITY FOR US.

     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  liable  for  damages,  penalties  or other  forms of  censure  and our
business could be significantly and adversely affected.

PROTECTION OF OUR INTELLECTUAL PROPERTY IS DIFFICULT TO OBTAIN.

     Our business and  competitive  positions are dependent  upon our ability to
protect our proprietary  technology.  Because of the substantial  length of time
and expense  associated with  development of new products,  we, like the rest of
the biopharmaceutical  industry,  place considerable importance on obtaining and
maintaining  patent and trade secret protection for new  technologies,  products
and  processes.  We  have  filed  patent  applications  for our  technology  for
diagnostic  and  therapeutic  products and the methods for their  production and
use.

     The patent positions of pharmaceutical, biopharmaceutical and biotechnology
companies,  including us, are generally  uncertain and involve complex legal and
factual questions.  Our patent applications may not protect our technologies and
products because, among other things:

     o    there  is no  guarantee  that any of our  pending patent  applications
          will result in issued patents;

                                      -17-
<PAGE>

     o    we  may  develop  additional  proprietary  technologies  that  are not
          patentable;

     o    there   is  no   guarantee  that   any  patents  issued   to  us,  our
          collaborators or our licensors will provide a basis for a commercially
          viable product;

     o    there  is  no  guarantee  that  any  patents  issued   to  us  or  our
          collaborators will provide us with any competitive advantage;

     o    there  is  no  guarantee  that  any  patents  issued   to  us  or  our
          collaborators  will not be challenged,  circumvented or invalidated by
          third parties; and

     o    there is no guarantee that any patents previously issued to  others or
          issued in the future will not have an adverse effect on our ability to
          do business.

     In  addition,  patent law in the  technology  fields in which we operate is
uncertain  and still  evolving,  and we cannot  assure  you as to the  degree of
protection  that will be  afforded  any  patents we are  issued or license  from
others.  Furthermore,  we cannot  assure you that others will not  independently
develop similar or alternative technologies,  duplicate any of our technologies,
or, if  patents  are  issued to us,  design  around  the  patented  technologies
developed by us. In addition,  we could incur substantial costs in litigation if
we are required to defend  ourselves  in patent suits by third  parties or if we
initiate  such suits.  We cannot  assure you that,  if  challenged  by others in
litigation,  the patents we have been issued,  or which we have been assigned or
have licensed from others will not be found  invalid.  We cannot assure you 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,  managerial and other resources.  An adverse
outcome could:

     o    subject us to significant liability to third parties;

     o    require  us to cease  any related research  and development activities
          and product sales; or

     o    require us to obtain licenses from third parties.

     We cannot assure you that any licenses  required under any such third-party
patents or proprietary rights would be made available on commercially reasonable
terms, if at all.  Moreover,  the laws of certain  countries may not protect our
proprietary  rights to the same  extent  as the laws of the  United  States.  We
cannot predict whether our or our competitors'  pending patent applications will
result in the issuance of valid  patents which may  significantly  and adversely
affect our business.

                                      -18-
<PAGE>

WE  CANNOT  BE  CERTAIN  THAT  OUR  SECURITY  MEASURES  PROTECT  OUR  UNPATENTED
PROPRIETARY TECHNOLOGY.

     We also rely upon trade secret  protection for some of our confidential and
proprietary  information that is not subject matter for which patent  protection
is available. 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 Cytogen. We cannot assure you, however, that these
agreements will provide adequate  protection for our trade secrets,  know-how or
other proprietary information or prevent any unauthorized use or disclosure.

WE ARE CURRENTLY SUBJECT TO PATENT LITIGATION.

     We are a defendant  in  litigation  filed  against us in the United  States
Federal  Court  for the  District  of New  Jersey  by M.  David  Goldenberg  and
Immunomedics,  Inc.  This  lawsuit was filed on March 16, 2000.  The  litigation
claims that our ProstaScint  product infringes a patent purportedly owned by Dr.
Goldenburg and licensed to  Immunomedics.  We believe that the purported  patent
sought to be enforced in the litigation has now expired. As a result, the claim,
even  if  successful,  would  not  result  in a bar of  the  continued  sale  of
ProstaScint  or affect any other of our products or technology.  However,  given
the uncertainty  associated with  litigation,  we cannot give any assurance that
the litigation  will not result in a material  expenditure to us or in a loss of
important rights by us.

IF WE MAKE ANY  ACQUISITIONS,  WE WILL  INCUR A  VARIETY  OF COSTS AND MAY NEVER
REALIZE THE ANTICIPATED BENEFITS.

     If appropriate  opportunities  become available,  we may attempt to acquire
businesses,  technologies,  services or products that we believe are a strategic
fit with our business.  We currently  have no  commitments  or  agreements  with
respect to any acquisitions, however, if we do undertake any transaction of this
sort, the process of integrating an acquired  business,  technology,  service or
product may result in operating  difficulties  and  expenditures  and may absorb
significant  management  attention that would otherwise be available for ongoing
development  of our business.  Moreover,  we may never  realize the  anticipated
benefits of any  acquisition.  Future  acquisitions  could result in potentially
dilutive  issuances of equity  securities,  the  incurrence of debt,  contingent
liabilities and  amortization  expenses related to goodwill and other intangible
assets.  These factors  could  adversely  affect our results of  operations  and
financial  condition,  which  could  cause a decline in the market  price of our
Common Stock.

OUR STOCK PRICE HAS BEEN AND MAY CONTINUE TO BE VOLATILE, AND YOUR INVESTMENT IN
OUR STOCK COULD DECLINE IN VALUE.

     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

                                      -19-
<PAGE>

continue  to  fluctuate  for  various  reasons,  including,  but not limited to,
announcements concerning our competitors or us regarding:

     o    results of clinical trials;

     o    technological innovations or new commercial products;

     o    changes  in  governmental regulation or  the status of  our regulatory
          approvals or applications;

     o    changes in earnings;

     o    changes in health care policies and practices;

     o    developments or disputes concerning proprietary rights;

     o    litigation  or  public  concern as  to safety  of  the  our  potential
          products; and

     o    changes in general market conditions.

WE HAVE ADOPTED  VARIOUS  ANTI-TAKEOVER  PROVISIONS  WHICH MAY AFFECT THE MARKET
PRICE OF OUR 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 5,400,000  shares of
preferred  stock in one or more  classes  or  series,  and to fix the rights and
preferences  of the  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 us 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 our junior participating  preferred
stock for $20.  If any person or group  becomes the  beneficial  owner of 20% or
more of our 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.

                                      -20-
<PAGE>

     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 for a period of three years  following the date that the person
came to own 15% or more of our Common Stock 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 us, may  discourage  bids for our 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 our Common Stock.

A LARGE NUMBER OF OUR SHARES ARE  ELIGIBLE  FOR FUTURE SALE WHICH MAY  ADVERSELY
IMPACT THE MARKET PRICE OF OUR 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 October 6, 2000, we
had  76,452,600  shares of Common Stock  outstanding.  An  additional  4,567,566
shares of Common  Stock are  issuable  upon the  exercise of  outstanding  stock
options and warrants.  Substantially  all of such shares  subject to outstanding
options  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 (the "Securities  Act"), as amended,
or pursuant to Rule 701 promulgated thereunder.

     Berlex Laboratories, Inc. exercised its registration rights with respect to
1,000,000 shares of Common Stock and we are contractually  obligated to register
these shares. A registration statement with respect to these shares was filed on
April  11,  2000 and  declared  effective  April  27,  2000.  Such  registration
statement  also covered  86,394 shares of Common Stock  issuable to  consultants
upon exercise of warrants.

     In addition,  on March 28, 2000, we filed with the  Securities and Exchange
Commission a shelf registration  statement on Form S-3 covering six million nine
hundred thousand (6,900,000) shares of our Common Stock.

     Availability of a significant number of additional shares could depress the
price of our Common Stock.

BECAUSE  WE DO NOT  INTEND  TO PAY ANY CASH  DIVIDENDS  ON OUR  SHARES OF COMMON
STOCK,  OUR  STOCKHOLDERS  WILL NOT BE ABLE TO RECEIVE A RETURN ON THEIR  SHARES
UNLESS THEY SELL THEM.

     We have never paid or declared  any cash  dividends  on our Common Stock or
other  securities  and  intend to retain  any future  earnings  to  finance  the
development and expansion of our business.  We do not anticipate paying any cash
dividends  on  our  Common  Stock  in  the  foreseeable  future.  Unless  we pay
dividends, our stockholders will not be able to receive a return on their shares
unless they sell them.

                                      -21-
<PAGE>

                SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

THIS  PROSPECTUS  CONTAINS  FORWARD-LOOKING  STATEMENTS  WITHIN  THE  MEANING OF
SECTION 27A OF THE  SECURITIES  ACT OF 1933 AND  SECTION  21E OF THE  SECURITIES
EXCHANGE ACT OF 1934. SUCH STATEMENTS CAN BE IDENTIFIED BY THE USE OF WORDS SUCH
AS  "MAY,"  "WOULD,"   "COULD,"   "INTEND,"   "PLAN,"   "ESTIMATE,"   "BELIEVE,"
"ANTICIPATE" AND "EXPECT." THESE STATEMENTS DISCUSS FUTURE EXPECTATIONS, CONTAIN
PROJECTIONS OR STATE OTHER "FORWARD-LOOKING"  INFORMATION.  ACTUAL RESULTS COULD
DIFFER  MATERIALLY  FROM  THOSE  EXPRESSED  OR  IMPLIED  IN THE  FORWARD-LOOKING
STATEMENTS AS A RESULT OF THE RISK FACTORS SET FORTH ABOVE AND ELSEWHERE IN THIS
PROSPECTUS  OR FOR OTHER  REASONS.  READERS  ARE  CAUTIONED  NOT TO PLACE  UNDUE
RELIANCE ON THESE FORWARD-LOOKING  STATEMENTS,  WHICH REFLECT MANAGEMENT'S VIEWS
ONLY AS OF THE DATE OF THIS PROSPECTUS.

                                 USE OF PROCEEDS

     We will not receive any of the proceeds from the sale of the Shares covered
by this  Prospectus.  While we will receive sums upon any exercise of options by
the Selling  Stockholders,  we  currently  have no plans for their  application,
other than for general corporate purposes. We cannot assure you that any of such
options will be exercised.

                              SELLING STOCKHOLDERS

     The  individuals  listed below (the  "Selling  Stockholders")  have or will
acquire  the Shares  being  registered  hereunder  pursuant  to the  exercise of
options we previously  granted to them or the purchase of Shares pursuant to the
Plans.  The  Shares  may not be sold or  otherwise  transferred  by the  Selling
Stockholders unless and until the applicable options are exercised in accordance
with their terms.

     The following  table sets forth:  (i) the name and position of each Selling
Stockholder,  whose  name  is  known  as of  the  date  of  the  filing  of  the
registration statement of which this prospectus forms a part, under the Plan who
may sell Common Stock pursuant to this prospectus;  (ii) the number of shares of
Common Stock owned (or subject to option) by each Selling  Stockholder as of the
date of this prospectus; (iii) the number of shares of Common Stock which may be
offered and are being registered for the account of each Selling  Stockholder by
this  prospectus  (all of which  may be  acquired  by the  Selling  Stockholders
pursuant to the  exercise of  options);  and (iv) the amount and  percentage  of
Common  Stock to be owned  by each  such  Selling  Stockholder  if such  Selling
Stockholder  were to sell all of the  shares of  Common  Stock  covered  by this
prospectus.  There can be no assurance that any of the Selling Stockholders will
offer for sale or sell any or all of the Shares offered by them pursuant to this
prospectus.  Options or shares of Common  Stock may be issued under the Plans in
amounts and to persons not  presently  known by us;  when known,  such  persons,
their holdings of Common Stock and certain other  information may be included in
a subsequent version of this prospectus.


                                      -22-
<PAGE>

<TABLE>
<CAPTION>

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

                                                              Number of Shares of      Number of
                                                               Common Stock both       Shares of      Number of Shares of
                                                           directly held or subject     Common            Common Stock
                                                              to options prior to     Stock to be          Owned After
     Name                     Position with Cytogen          Offering/Percentage(1)     Offered      Offering/Percentage(2)
---------------------------------------------------------------------------------------------------------------------------
<S>                           <C>                               <C>                     <C>           <C>
H. Joseph Reiser              Chief Executive Officer,          2,505,000/3.3%          150,000       2,355,000/3.1%(3)
                               President and Director
---------------------------------------------------------------------------------------------------------------------------
Lawrence Hoffman              Vice President and Chief             500,000/*            200,000          300,000/*(4)
                               Financial Officer
---------------------------------------------------------------------------------------------------------------------------
Richard Krawiec               Vice President, Investor             50,000/*             50,000               0/*
                               Relations and Corporate
                               Communications
---------------------------------------------------------------------------------------------------------------------------
Nicholas Borys                Vice President, Medical              50,000/*             50,000               0/*
                               Affairs
---------------------------------------------------------------------------------------------------------------------------
Terence Novak                 Vice President, Sales and            95,000/*             95,000               0/*
                               Marketing
---------------------------------------------------------------------------------------------------------------------------
John D. Rodwell               Acting President and Chief         798,200/1.0%           419,500          378,700/*(5)
                               Technical Officer, AxCell
                               BioSciences, a subsidiary
---------------------------------------------------------------------------------------------------------------------------
Catherine M. Verna            Vice President and General           50,000/*             50,000               0/*
                               Counsel
---------------------------------------------------------------------------------------------------------------------------
John E. Bagalay, Jr.          Director                             253,467/*            125,000          128,467/*(6)
---------------------------------------------------------------------------------------------------------------------------
Stephen K. Carter             Director                             43,600/*              8,000           35,600/*(7)
---------------------------------------------------------------------------------------------------------------------------
James A. Grigsby              Director                             233,867/*            70,000           163,867/*(8)
---------------------------------------------------------------------------------------------------------------------------
Robert F. Hendrickson         Director                             90,600/*             29,000           61,600/*(9)
---------------------------------------------------------------------------------------------------------------------------
S. Leslie Misrock             Director                             755,833/*            10,000          745,833/*(10)
---------------------------------------------------------------------------------------------------------------------------

</TABLE>

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

*    Less than one percent.

(1)  Applicable  percentage of ownership is based on 76,452,600 shares of Common
     Stock outstanding on October 6, 2000.

(2)  Assumes  that all  Shares are  sold pursuant  to this  offering and that no
     other  shares of Common  Stock are  acquired  or disposed of by the Selling
     Stockholders prior to the termination of this offering. Because the Selling
     Stockholders  may sell all,  some or none of their Shares or may acquire or
     dispose of other shares of Common Stock,  no reliable  estimate can be made
     of the  aggregate  number of  Shares  that  will be sold  pursuant  to this
     offering or the number or  percentage  of shares of Common  Stock that each
     Selling Stockholder will own upon completion of this offering.

(3)  Includes 2,050,000 shares of Common Stock issuable pursuant to options held
     as of the date hereof and not registered or sold hereunder.

(4)  Includes  300,000 shares of  Common Stock issuable pursuant to options held
     as of the date hereof and not registered or sold hereunder.

(5)  Does not include 100,000 shares of AxCell  Biosciences  Corporation  Common
     Stock,  $0.01 par value per share,  issuable pursuant to options held as of
     the date hereof and not registered or sold hereunder.

(6)  Includes 31,000 shares of Common Stock issuable pursuant to options held as
     of the date hereof and not registered or sold hereunder.

(7)  Includes 31,000 shares of Common Stock issuable pursuant to options held as
     of the date hereof and not registered or sold hereunder.

                                      -23-
<PAGE>

(8)  Includes 61,000 shares of Common Stock issuable pursuant to options held as
     of the date hereof and not registered or sold hereunder.

(9)  Includes 31,000 shares of Common Stock issuable pursuant to options held as
     of the date hereof and not registered or sold hereunder.

(10) Includes 18,333 shares of Common Stock issuable pursuant to options held as
     of the date hereof and not registered or sold hereunder.

                              PLAN OF DISTRIBUTION

     The  Selling  Stockholders  have not  advised us of any  specific  plan for
distribution of the Shares offered hereby, but it is anticipated that the Shares
will be sold  from  time to time by the  Selling  Stockholders  or by  permitted
pledgees,  donees,  transferees or other permitted successors in interest.  Such
sales may be made in any of the following manners:

     o    On  the  Nasdaq  National  Market (or  through the  facilities of  any
          national securities exchange or U.S. inter-dealer  quotation system of
          a registered national securities association,  on which the Shares are
          then listed,  admitted to unlisted trading  privileges or included for
          quotation);

     o    In public or privately negotiated transactions;

     o    In transactions involving principals or brokers;

     o    In a combination of such methods of sale; or

     o    Any other lawful methods.

     Although sales of the Shares are, in general, expected to be made at market
prices  prevailing  at the time of sale,  the  Shares may also be sold at prices
related to such  prevailing  market  prices or at negotiated  prices,  which may
differ considerably.

     When offering the Shares  covered by this  Prospectus,  each of the Selling
Stockholders  and any  broker-dealers  who  sell  the  Shares  for  the  Selling
Stockholders may be "underwriters" within the meaning of the Securities Act, and
any profits  realized by such Selling  Stockholders and the compensation of such
broker-dealers may be underwriting discounts and commissions.

     Sales  through  brokers may be made by any method of trading  authorized by
any stock exchange or market on which the Shares may be listed,  including block
trading in negotiated transactions. Without limiting the foregoing, such brokers
may act as  dealers  by  purchasing  any or all of the  Shares  covered  by this
Prospectus, either as agents for others or as principals for their own accounts,
and reselling such Shares pursuant to this Prospectus.  The Selling Stockholders
may effect such  transactions  directly,  or  indirectly  through  underwriters,
broker-dealers  or agents acting on their behalf. In connection with such sales,
such  broker-dealers  or  agents  may  receive   compensation  in  the  form  of
commissions,  concessions, allowances or discounts, any or all of which might be
in excess of customary amounts.

     Each of the Selling  Stockholders is acting  independently  of us in making
decisions with respect to the timing, manner and size of each sale of Shares. We
have not been advised of any definitive selling  arrangement at the date of this
Prospectus between any Selling Stockholder and any broker-dealer or agent.

                                      -24-
<PAGE>

     To the  extent  required,  the  names  of  any  agents,  broker-dealers  or
underwriters and applicable commissions,  concessions,  allowances or discounts,
and any other required  information  with respect to any particular offer of the
Shares by any of the Selling Stockholders,  will be set forth in a supplement to
this Prospectus.

     The  expenses  of  preparing  and filing  this  Prospectus  and the related
Registration  Statement  with the SEC will be paid entirely by the Company.  The
Shares covered by this  Prospectus  also may qualify to be sold pursuant to Rule
144 under the  Securities  Act,  rather than  pursuant to this  Prospectus.  The
Selling  Stockholders  have been advised that they are subject to the applicable
provisions of the  Securities  Exchange Act of 1934,  as amended (the  "Exchange
Act"), including without limitation, Rule 10b-5 thereunder.

     Neither  the  Company  nor the  Selling  Stockholders  can  estimate at the
present time the amount of commissions  or discounts,  if any, that will be paid
by the Selling Stockholders on account of their sales of the Shares from time to
time.

                                  LEGAL MATTERS

     The  validity of the shares of Common Stock  offered  hereby will be passed
upon for the Company by Buchanan Ingersoll Professional Corporation, 650 College
Road East, Princeton, New Jersey.

                                     EXPERTS

     The  consolidated  financial  statements  incorporated by reference in this
Prospectus  and elsewhere in this  Registration  Statement  have been audited by
Arthur  Andersen  LLP,  independent  public  accountants,  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.

                      INFORMATION INCORPORATED BY REFERENCE

     The SEC allows us to  "incorporate  by reference"  the  information we file
with the SEC, which means that we can disclose  important  information to you by
referring you to those documents.  The information  incorporated by reference is
an important part of this prospectus.  All documents  subsequently  filed by the
Company  pursuant to Sections  13(a),  13(c),  14 and 15(d) of the Exchange Act,
prior to the  filing of a  post-effective  amendment  which  indicates  that all
securities  offered  have been sold or which  deregisters  all  securities  then
remaining  unsold,  shall be deemed to be  incorporated  by reference  into this
Prospectus and to be a part hereof from the date of filing of such documents.

     We  incorporate  by  reference  the  documents  listed below and any future
filings we make with the SEC under Sections  13(a),  13(c),  14, or 15(d) of the
Securities  Exchange Act of 1934 until the filing of a post-effective  amendment
to this Prospectus which indicates that all securities registered have been sold
or which deregisters all securities then remaining unsold:

     o    Our Annual  Report on Form 10-K for the year ended  December  31, 1999
          (File No. 000-14879), filed with the SEC on March 28, 2000;

                                      -25-
<PAGE>

     o    All  other reports filed by Cytogen pursuant to Section 13(a) or 15(d)
          of the Exchange Act since December 31, 1999; and

     o    The description of our Common Stock, $0.01 par value, contained in our
          Registration Statement on Form 8-A (File No. 000-14879) filed pursuant
          to Section 12(g) of the  Securities  Exchange Act of 1934, as amended,
          including any  subsequent  amendments or reports filed for the purpose
          of updating such description.

     We will provide,  without charge, to each person,  including any beneficial
owner, to whom a copy of this prospectus is delivered,  upon the written or oral
request of such person, a copy of any or all of the information  incorporated in
this prospectus by reference but not delivered with the prospectus. The requests
should be made to:

                        Catherine M. Verna, Esq.
                        Cytogen Corporation
                        600 College Road East CN 5308
                        Princeton, New Jersey   08540
                        (609) 750-8200

     You  should  rely only on the  information  incorporated  by  reference  or
provided in this  Prospectus or any  supplement  hereto.  We have not authorized
anyone to  provide  you with  different  information.  Neither  Cytogen  nor the
Selling  Stockholders are making an offer of these securities in any state where
the offer is not permitted.  You should not assume that the  information in this
Prospectus  is  accurate  as of any date other than the date on the front of any
such document.


                                      -26-
<PAGE>

                       WHERE YOU CAN FIND MORE INFORMATION

     We file annual,  quarterly and special reports,  proxy statements and other
information  with the SEC. You may read and copy any document the Company  files
at the SEC's public reference room at 450 Fifth Street, N.W.,  Washington,  D.C.
20549.  Please call the SEC at  1-800-SEC-0330  for further  information  on the
public reference room. Our SEC filings are also available to the public from the
SEC's website at http://www.sec.gov.

     We have filed with the SEC a  Registration  Statement on Form S-8 under the
Securities Act with respect to the Shares offered hereby. This Prospectus, which
constitutes  a part of that  registration  statement,  does not  contain all the
information  contained  in the  registration  statement  and its  exhibits.  For
further  information  with  respect  to  the  Shares,  you  should  consult  the
registration statement and its exhibits. Statements contained in this Prospectus
concerning  the provisions of any documents are  necessarily  summaries of those
documents,  and each  statement is qualified in its entirety by reference to the
copy of the document filed with the SEC. The  registration  statement and any of
its amendments,  including exhibits filed as part of the registration  statement
or an amendment to the registration statement,  are available for inspection and
copying as described above.

                    INDEMNIFICATION OF DIRECTORS AND OFFICERS

     Section  145(a)  of the  Delaware  General  Corporation  Law  (the  "DGCL")
provides  that a Delaware  corporation  may  indemnify  any person who was 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 the person 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,  partnership, joint
venture,  trust or other  enterprise,  against  expenses  (including  attorneys'
fees),  judgments,  fines and amounts paid in settlement actually and reasonably
incurred by the person in connection with such action, suit or proceeding if the
person acted in good faith and in a manner the person 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  reasonable  cause to believe  the
person's 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 the
person 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,  partnership,  joint venture, trust or
other  enterprise,  against  expenses  (including  attorneys' fees) actually and
reasonably  incurred by the person in connection  with the defense or settlement
of such  action  or suit if he or she acted in good  faith  and in a manner  the
person reasonably  believed to be in or not opposed to the best interests of the
corporation and except that no  indemnification  shall 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

                                      -27-
<PAGE>

and only to the  extent  that the Court of  Chancery  or the court in which such
action or suit was brought shall determine upon  application  that,  despite the
adjudication of liability but in view of all of the  circumstances  of the case,
such person is fairly and  reasonably  entitled to indemnity  for such  expenses
which the Court of Chancery or such other court shall deem proper.

     Section  145  further  provides  that to the  extent a  present  or  former
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) of Section
145, or in the defense of any claim, issue or matter therein,  such person shall
be  indemnified  against  expenses  (including  attorneys'  fees)  actually  and
reasonably   incurred  by  such  person  in  connection   therewith;   that  the
indemnification  provided  by Section 145 shall not be deemed  exclusive  of any
other rights to which the indemnified party may be entitled;  and that the scope
of indemnification  extends to directors,  officers,  employees,  or agents of a
constituent  corporation  absorbed  in a  consolidation  or merger  and  persons
serving in that  capacity  at the  request of the  constituent  corporation  for
another.  Section 145 also  empowers  the  corporation  to purchase and maintain
insurance  on behalf of a director  or officer of the  corporation  against  any
liability  asserted  against  him or her or  incurred  by him or her in any such
capacity  or  arising  out of his or her  status  as  such  whether  or not  the
corporation  would  have  the  power  to  indemnify  him  or  her  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 act in 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. Cytogen's restated certificate of incorporation contains such a provision.
Cytogen's  certificate  of  incorporation  and bylaws provide that Cytogen shall
indemnify  officers and directors  and, to the extent  permitted by the board of
directors,  employees and agents of Cytogen, to the full extent permitted by and
in the manner permissible under the laws of the State of Delaware.  In addition,
the bylaws  permit the board of directors  to authorize  Cytogen to purchase and
maintain insurance against any director,  officer,  employee or agent of Cytogen
arising out of his capacity as such.

     At  present,  there is no pending  litigation  or  proceeding  involving  a
director  or  officer of the  Registrant  as to which  indemnification  is being
sought nor is the Registrant aware of any threatened  litigation that may result
in claims for indemnification by any director or officer.

                                      -28-
<PAGE>

                   SECURITIES AND EXCHANGE COMMISSION POSITION
                ON INDEMNIFICATION FOR SECURITIES ACT LIABILITIES

     Insofar as indemnification for liabilities arising under the Securities Act
may be permitted to directors,  officers and controlling  persons of the Company
pursuant to the foregoing provisions, or otherwise, the Company has been advised
that in the opinion of the SEC such  indemnification is against public policy as
expressed in the Securities Act and is, therefore, unenforceable.



                                      -29-
<PAGE>

                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

ITEM 3.   INCORPORATION OF DOCUMENTS BY REFERENCE.

     The SEC allows us to  "incorporate  by reference"  the  information we file
with the SEC, which means that we can disclose  important  information to you by
referring you to those documents.  The information  incorporated by reference is
an important part of this  Prospectus,  and information  that we file later with
the SEC will automatically update and supersede this information. We incorporate
by reference the documents  listed below and any future  filings made by us with
the SEC under Sections  13(a),  13(c), 14 or 15(d) of the Exchange Act until the
filing of a post-effective amendment to this Prospectus which indicates that all
securities  registered  have been sold or which  deregisters all securities then
remaining unsold:

     o    Our  Annual Report  on Form 10-K for  the year ended December 31, 1999
          (Commission File No. 000-14879), filed with the SEC on March 28, 2000;

     o    All  other reports filed by Cytogen pursuant to Section 13(a) or 15(d)
          of the Exchange Act since December 31, 1999; and

     o    The description of our Common Stock, $0.01 par value, contained in our
          Registration  Statement on Form 8-A  (Commission  File No.  000-14879)
          filed  pursuant to Section  12(g) of the  Securities  Exchange  Act of
          1934, as amended, including any subsequent amendments or reports filed
          for the purpose of updating such description.

ITEM 4    DESCRIPTION OF SECURITIES.

     Not Applicable.


ITEM 5.   INTERESTS OF NAMED EXPERTS AND COUNSEL.

     Not Applicable.


                                      -30-
<PAGE>

ITEM 6.   INDEMNIFICATION OF DIRECTORS AND OFFICERS.

     Section  145(a)  of the  DGCL  provides  that a  Delaware  corporation  may
indemnify  any  person  who  was 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 the  person 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,  partnership,  joint venture,  trust or other  enterprise,
against expenses (including attorneys' fees), judgments,  fines and amounts paid
in settlement  actually and reasonably incurred by the person in connection with
such  action,  suit or  proceeding  if the  person  acted in good faith and in a
manner  the  person  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  reasonable  cause  to  believe  the  person's  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 the
person 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,  partnership,  joint venture, trust or
other  enterprise,  against  expenses  (including  attorneys' fees) actually and
reasonably  incurred by the person in connection  with the defense or settlement
of such  action  or suit if he or she acted in good  faith  and in a manner  the
person reasonably  believed to be in or not opposed to the best interests of the
corporation and except that no  indemnification  shall 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 of
Chancery or the court in which such action or suit was brought  shall  determine
upon application that,  despite the adjudication of liability but in view of all
of the circumstances of the case, such person is fairly and reasonably  entitled
to indemnity for such  expenses  which the Court of Chancery or such other court
shall deem proper.

     Section  145  further  provides  that to the  extent a  present  or  former
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) of Section
145, or in the defense of any claim, issue or matter therein,  such person shall
be  indemnified  against  expenses  (including  attorneys'  fees)  actually  and
reasonably   incurred  by  such  person  in  connection   therewith;   that  the
indemnification  provided  by Section 145 shall not be deemed  exclusive  of any
other rights to which the indemnified party may be entitled;  and that the scope
of indemnification  extends to directors,  officers,  employees,  or agents of a
constituent  corporation  absorbed  in a  consolidation  or merger  and  persons
serving in that  capacity  at the  request of the  constituent  corporation  for
another.  Section 145 also  empowers  the  corporation  to purchase and maintain
insurance  on behalf of a director  or officer of the  corporation  against  any
liability  asserted  against  him or her or  incurred  by him or her in any such
capacity  or  arising  out of his or her  status  as  such  whether  or not  the
corporation  would  have  the  power  to  indemnify  him  or  her  against  such
liabilities under Section 145.

                                      -31-
<PAGE>

     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 act in 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. Cytogen's restated certificate of incorporation contains such a provision.
Cytogen's  certificate  of  incorporation  and bylaws provide that Cytogen shall
indemnify  officers and directors  and, to the extent  permitted by the board of
directors,  employees and agents of Cytogen, to the full extent permitted by and
in the manner permissible under the laws of the State of Delaware.  In addition,
the bylaws  permit the board of directors  to authorize  Cytogen to purchase and
maintain insurance against any director,  officer,  employee or agent of Cytogen
arising out of his capacity as such.

     At  present,  there is no pending  litigation  or  proceeding  involving  a
director  or  officer of the  Registrant  as to which  indemnification  is being
sought nor is the Registrant aware of any threatened  litigation that may result
in claims for indemnification by any director or officer.

ITEM 7.   EXEMPTION FROM REGISTRATION CLAIMED.

     The issuance of the Shares being offered by the Form S-3 Reoffer Prospectus
were deemed exempt from  registration  under the Securities Act in reliance upon
either  Section 4(2) of the  Securities  Act as  transactions  not involving any
public  offering  or Rule 701  under the  Securities  Act as  transactions  made
pursuant  to a written  compensatory  plan or  pursuant  to a  written  contract
relating to compensation.

ITEM 8.   EXHIBITS.

     4.1    Cytogen  Corporation   1988  Stock  Option  Plan  for   Non-Employee
            Directors, as  amended.  Filed as exhibits  to Form S-8 Registration
            Statement  (No.  33-30595)  and Form 10-Q  Quarterly  Report for the
            quarter  ended  June 30, 1996  (Commission File  No. 000-14879)  and
            incorporated herein by reference.

     4.2    Cytogen  Corporation  1989  Employee  Stock  Option  Plan.  Filed as
            an exhibit to Form S-8  Registration Statement  (No.  33-30595)  and
            incorporated herein by reference.

     4.3    Cytogen  Corporation 1989 Special Employee Plan. Filed as an exhibit
            to Form S-8 Registration  Statement (No. 33-30595)  and incorporated
            herein by reference.

     4.4    Cytogen   Corporation   1989  Stock  Option   Policy   for   Outside
            Consultants. Filed as an exhibit  to  Amendment  No.  1 to Form  S-1
            Registration Statement (No. 33-

                                      -32-
<PAGE>

            31280) and incorporated herein by reference.

     4.5    Cytogen Corporation 1992  Employee Stock Option Plan II, as amended.
            Filed  as an  exhibit to  Form S-4  Registration  Statement (No. 33-
            88612)  and incorporated herein by  reference.

     4.6    Cytogen Corporation  1995 Stock Option  Plan,  as amended.  Filed as
            exhibits to Form 10-K Annual Report for the year ended  December 31,
            1995 (Commission  File No. 000-14879) and Form 10-Q Quarterly Report
            for the quarter  ended June 30, 1996 (Commission File No. 000-14879)
            and incorporated  herein  by  reference.

     4.7    Cytogen  Corporation  Employee  Stock  Purchase  Plan.  Filed  as an
            exhibit  to  Form S-8  Registration  Statement  (No. 333-27673)  and
            incorporated herein by reference.

     4.8    Cellcor, Inc. 1988 Stock Option Plan.  Filed as an exhibit  to  Form
            S-8 Registration Statement (No. 333-00431)  and  incorporated herein
            by reference.

     4.9    Cellcor, Inc. 1992 Stock Option and Restricted Stock Plan. Filed  as
            an  exhibit  to  Form  S-8 Registration  Statement  (No.  333-00431)
            and incorporated herein by reference.

     4.10   Cellcor, Inc. 1992 Director Stock Plan.  Filed as an exhibit to Form
            S-8 Registration Statement (No. 333-00431)  and incorporated  herein
            by reference.

     4.11   Cellcor, Inc. 1995 Stock Incentive Plan. Filed as an exhibit to Form
            S-8 Registration Statement (No.  333-00431) and incorporated  herein
            by reference.

     5      Opinion of Buchanan Ingersoll Professional Corporation.

     23.1   Consent of Arthur Andersen  LLP.

     23.2   Consent of Buchanan Ingersoll Professional Corporation (contained in
            the opinion filed as Exhibit 5).

     24     Power  of  Attorney  (contained  on  the  signature  page  of   this
            Registration Statement).

ITEM 9.   UNDERTAKINGS.

     a.   Cytogen hereby undertakes:

          (1) To file, during  any  period in  which offers  or sales  are being
     made, a post-effective  amendment to this registration statement to include
     any  material  information  with  respect  to the  plan of distribution not
     previously disclosed in this registration statement or  any material change
     to such information in this registration statement.

                                      -33-
<PAGE>

          (2) That,  for the  purpose of  determining  any  liability  under the
     Securities Act, each such post-effective  amendment 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.

          (3) To  remove  from  registration  by  means  of  a    post-effective
     amendment  any of  the securities being  registered which remain  unsold at
     the termination of the offering.

     b.   The  undersigned  Registrant  hereby  undertakes that, for purposes of
determining  any  liability  under  the  Securities  Act,  each  filing  of  the
Registrant's  annual  report  pursuant to Section  13(a) or Section 15(d) of the
Exchange Act (and, where  applicable,  each filing of an employee benefit plan's
annual  report   pursuant  to  Section  15(d)  of  the  Exchange  Act)  that  is
incorporated by reference in this 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.

     c.   Insofar   as  indemnification   for  liabilities  arising  under   the
Securities,  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
Securities Act and is, therefore,  unenforceable.  In the event that a claim for
indemnification  against  such  liabilities  (other  than  the  payment  by  the
Registrant of expenses  incurred or paid by a director,  officer or  controlling
person of 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  Securities
Act and will be governed by the final adjudication of such issue.


                                      -34-
<PAGE>

                                   SIGNATURES

     Pursuant to the requirements of the Securities Act of 1933, as amended, the
Registrant certifies that it has reasonable grounds to believe that it meets all
of the  requirements  for filing on Form S-8 and has duly caused this  Amendment
No.  1 to  the  Registration  Statement  to be  signed  on  its  behalf  by  the
undersigned,  thereunto duly authorized, in the City of Princeton,  State of New
Jersey, on this 18th day of October, 2000.

                                        CYTOGEN CORPORATION

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

<PAGE>

                                POWER OF ATTORNEY

     KNOW  ALL MEN BY THESE  PRESENTS,  that  each  individual  whose  signature
appears below  constitutes and appoints H. Joseph Reiser and,  Lawrence  Hoffman
and each of them,  his 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) to this Registration Statement, and to file the same
with all exhibits thereto, and all documents in connection  therewith,  with the
Securities and Exchange  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 and  about  the
premises,  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 in the
capacities and on the date indicated.

    Signature                           Title                          Date
    ---------                           -----                          ----

/s/ H. Joseph Reiser      President and Chief Executive Officer  October 9, 2000
--------------------      and Director (Principal Executive and
H. Joseph Reiser          Financial Officer)

/s/ John E. Bagalay       Director                               October 9, 2000
-------------------
John E. Bagalay

/s/ Stephen K. Carter     Director                               October 9, 2000
---------------------
Stephen K. Carter

/s/ James A. Grigsby      Director                               October 9, 2000
--------------------
James A. Grigsby

/s/ S. Leslie Misrock     Director                               October 9, 2000
---------------------
S. Leslie Misrock

/s/ Robert F. Hendrickson Director                               October 9, 2000
-------------------------
Robert F. Hendrickson


<PAGE>

                                  EXHIBIT INDEX

      Exhibit                                     Description
      Number                                      -----------
      ------

        4.1    Cytogen  Corporation  1988  Stock  Option  Plan for  Non-Employee
               Directors, as amended. Filed as exhibits to Form S-8 Registration
               Statement (No.  33-30595) and Form 10-Q Quarterly  Report for the
               quarter  ended June 30, 1996  (Commission File No. 000-14879) and
               incorporated  herein by reference.

        4.2    Cytogen  Corporation 1989 Employee Stock Option Plan. Filed as an
               exhibit to Form S-8  Registration  Statement  (No.  33-30595) and
               incorporated  herein by reference.

        4.3    Cytogen  Corporation  1989  Special  Employee Plan.  Filed  as an
               exhibit to Form S-8  Registration  Statement  (No.  33-30595) and
               incorporated  herein by reference.

        4.4    Cytogen   Corporation  1989  Stock  Option  Policy  for   Outside
               Consultants.  Filed as an exhibit to Amendment  No. 1 to Form S-1
               Registration  Statement (No. 33-31280) and incorporated herein by
               reference.

        4.5    Cytogen  Corporation  1992  Employee  Stock  Option  Plan II,  as
               amended.  Filed  as an exhibit to Form S-4 Registration Statement
               (No. 33-88612) and  incorporated  herein by reference.

        4.6    Cytogen Corporation 1995 Stock Option Plan, as amended. Filed  as
               exhibits to Form 10-K Annual  Report for the year ended  December
               31, 1995 (Commission  File No. 000-14879) and Form 10-Q Quarterly
               Report for the quarter ended June 30, 1996  (Commission  File No.
               000-14879) and incorporated herein by reference.

        4.7    Cytogen  Corporation  Employee  Stock  Purchase Plan. Filed as an
               exhibit to Form S-8  Registration  Statement (No.  333-27673) and
               incorporated  herein by reference.

        4.8    Cellcor, Inc. 1988 Stock Option  Plan.  Filed  as an  exhibit  to
               Form S-8 Registration  Statement (No. 333-00431) and incorporated
               herein by  reference.

        4.9    Cellcor, Inc. 1992 Stock Option and Restricted Stock Plan.  Filed
               as an exhibit to Form S-8 Registration  Statement (No. 333-00431)
               and  incorporated  herein by reference.

        4.10   Cellcor,  Inc. 1992  Director Stock  Plan. Filed as an exhibit to
               Form S-8 Registration Statement (No.  333-00431) and incorporated
               herein by reference.

        4.11   Cellcor,  Inc. 1995 Stock  Incentive Plan. Filed as an exhibit to
               Form  S-8

<PAGE>

               Registration Statement (No. 333-00431) and incorporated herein by
               reference.

        5      Opinion of Buchanan Ingersoll Professional  Corporation.

        23.1   Consent of Arthur  Andersen LLP.

        23.2   Consent of Buchanan Ingersoll Professional Corporation (contained
               in the  opinion  filed  as  Exhibit  5).

        24     Power  of  Attorney  (contained  on  the  signature  page of this
               Registration Statement).



<PAGE>








                                    EXHIBIT 5


<PAGE>

                               Buchanan Ingersoll
                            Professional Corporation
                         (Incorporated in Pennsylvania)
                                    Attorneys
                              650 College Road East
                           Princeton, New Jersey 08540

                                                               October 18, 2000

Cytogen Corporation
600 College Road East CN 5308
Princeton, New Jersey   08540

Gentlemen:

     We have acted as counsel to  Cytogen  Corporation,  a Delaware  corporation
(the   "Company"),   in  connection   with  the  filing  by  the  Company  of  a
Post-Effective  Amendment  No. 1 to a  Registration  Statement  on Form S-8 (the
"Amendment") together with a Reoffer Prospectus (the "Prospectus") which relates
to the public resale,  from time to time, of an aggregate of 8,488,960 shares of
the Company's Common Stock, $0.01 par value per share, which have been or may be
acquired  upon the  exercise of stock  options  granted or upon stock  purchases
pursuant  to:  (i)  the  Company's  1988  Stock  Option  Plan  for  Non-Employee
Directors;  (ii) the  Company's  1989  Employee  Stock  Option  Plan;  (iii) the
Company's  1989 Special  Employee  Plan;  (iv) the  Company's  1989 Stock Option
Policy for Outside  Consultants;  (v) the Company's  1992 Employee  Stock Option
Plan II, as amended;  (vi) the  Company's  1995 Stock Option  Plan,  as amended;
(vii) the  Company's  Employee  Stock  Purchase  Plan;  (viii)  Cellcor,  Inc.'s
("Cellcor")  1988 Stock  Option  Plan;  (ix)  Cellcor's  1992  Stock  Option and
Restricted  Stock  Plan;  (x)  Cellcor's  1992  Director  Stock  Plan;  and (xi)
Cellcor's 1995 Stock Incentive Plan, collectively referred to hereinafter as the
"Plans".  The shares  underlying the Amendment and  Prospectus are  collectively
referred to hereinafter as the "Shares."

     In  connection  with the Amendment  and  Prospectus,  we have examined such
corporate records and documents,  other documents,  and such questions of law as
we have deemed  necessary or  appropriate  for purposes of this opinion.  On the
basis of such examination, it is our opinion that:

     1.   The issuance of the Shares has been duly and validly authorized; and

     2.   The Shares underlying the Plans,  when issued,  delivered  and sold in
          accordance with the terms of the Plans and the stock options, or other
          instruments  authorized  by  the  Plans,  granted  or  to  be  granted
          thereunder, will be legally issued, fully paid and non-assessable.

<PAGE>

     We  hereby  consent  to the  filing  of this  opinion  as  Exhibit 5 to the
Amendment and Prospectus.

                                         Very truly yours,

                                         /s/BUCHANAN INGERSOLL
                                         PROFESSIONAL CORPORATION


                                         /s/ Raymond Thek
                                         ---------------------------------------
                                         By:  Raymond Thek, a member of the firm


<PAGE>

                                  EXHIBIT 23.1


<PAGE>

                    CONSENT OF INDEPENDENT PUBLIC ACCOUNTANTS

As independent  public  accountants,  we hereby consent to the  incorporation by
reference in this  registration  statement of our report dated January 27, 2000,
included in Cytogen Corporation's Form 10-K for the year ended December 31, 1999
and to all references to our Firm included in this registration statement.

                                            Arthur Andersen LLP

Philadelphia, Pennsylvania
October 18, 2000


<PAGE>

                                  EXHIBIT 23.2

                            (contained in Exhibit 5)


<PAGE>

                                   EXHIBIT 24

                         (contained on signatures page)





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