SUGEN INC
424B4, 1999-08-02
BIOLOGICAL PRODUCTS, (NO DIAGNOSTIC SUBSTANCES)
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                                            Filed Pursuant to Rule 424(b)(4)
                                            Registration Statement No. 333-76969



                                  [SUGEN Logo]




                                   SUGEN, INC.

                                   PROSPECTUS


                        2,461,943 Shares of Common Stock


                     Offered by Certain Selling Stockholders




         Sugen,  Inc. is  registering  for resale up to 2,461,943  shares of its
common  stock for seven selling  stockholders.  We will not receive any proceeds
from the sale of the shares by the selling stockholders.

         Our common  stock is traded on the  Nasdaq  National  Market  under the
symbol  "SUGN." On July 30, 1999,  the last  reported  sale price for our common
stock was $29.6875 per share.



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

                 THIS INVESTMENT INVOLVES A HIGH DEGREE OF RISK.
                     SEE "RISK FACTORS" BEGINNING ON PAGE 5.

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


THE SECURITIES AND EXCHANGE COMMISSION AND STATE SECURITIES  REGULATORS HAVE NOT
APPROVED  OR  DISAPPROVED  OF  THESE  SECURITIES  OR  DETERMINED   WHETHER  THIS
PROSPECTUS  IS TRUTHFUL OR  COMPLETE.  ANY  REPRESENTATION  TO THE CONTRARY IS A
CRIMINAL OFFENSE.

THE  INFORMATION  IN THIS  PROSPECTUS  IS NOT COMPLETE  AND MAY BE CHANGED.  THE
SELLING  STOCKHOLDERS MAY NOT SELL THE SHARES UNTIL THE  REGISTRATION  STATEMENT
FILED WITH THE SECURITIES AND EXCHANGE COMMISSION IS EFFECTIVE.  THIS PROSPECTUS
IS NOT AN OFFER TO SELL THESE  SECURITIES  AND IT IS NOT  SOLICITING AN OFFER TO
BUY THESE SECURITIES IN ANY STATE WHERE THE OFFER OR SALE IS NOT PERMITTED.





                  The date of this prospectus is August 2, 1999



                                       1

<PAGE>

                                TABLE OF CONTENTS

                                                                            Page

Summary......................................................................  3
Risk Factors.................................................................  5
Selling Stockholders......................................................... 12
Plan of Distribution......................................................... 14
Legal Matters................................................................ 14
Experts...................................................................... 14
Where You Can Find More Information.......................................... 15

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

         Our web site address is www.sugen.com. Information contained on our web
site is not a part of this prospectus.

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

         You should rely only on the information  contained in this  prospectus.
We have not  authorized  anyone to provide you with  information  different from
that contained in this prospectus. The selling stockholders are offering to sell
and seeking  offers to buy the shares  only in  jurisdictions  where  offers and
sales are permitted.  The  information  contained in this prospectus is accurate
only as of the date of this prospectus.




                                       2
<PAGE>



                                     SUMMARY

         The  following  information  is  qualified  in its entirety by the more
detailed   information  and  financial   statements,   and  notes  to  financial
statements, appearing elsewhere or incorporated by reference in this prospectus.
This prospectus contains certain  forward-looking  statements within the meaning
of Section 27A of the Securities Act and Section 21E of the Exchange Act. Actual
results  could differ  materially  from those  projected in the  forward-looking
statements  as a result of certain of the risk  factors set forth  elsewhere  in
this prospectus.  Investors should carefully  consider the information set forth
under the heading "Risk Factors."


SUGEN



         SUGEN is a  biopharmaceutical  company  focused  on the  discovery  and
development of small molecule drugs which target  specific  pathways  within and
between  cells,  known as signal  transduction  pathways.  Receptors of chemical
messengers that are embedded in the cell wall or on signalling  molecules within
the cell  regulate  these  signalling  pathways.  These  receptors or signalling
molecules are biochemical  "targets" known as tyrosine  kinases (TKs),  tyrosine
phosphatases  (TPs)  and  serine-threonine  kinases  (STKs).  These  biochemical
targets, which represent three of the largest known families of receptors in the
body, regulate critical cellular functions.  Abnormal signalling of TKs, TPs and
STKs can  result in a  variety  of  chronic  and  acute  pathological  diseases,
including  cancer  and  diabetes,  as  well  as  in  dermatologic,   ophthalmic,
neurologic and immune  disorders.  Kinases and phosphates are molecules that are
needed for normal  signalling to occur between and within cells. We believe that
compounds designed to target certain kinases and phosphatases and inhibit enzyme
activity  or  prevent  the  binding  of  downstream  signalling  molecules  make
attractive  therapeutic  product  candidates.  Drugs  that  regulate  signalling
pathways, potentially stopping the growth of tumor cells (cytostatic drugs), may
be safer and more directed than traditional chemotherapy drugs that "kill" cells
(cytotoxic drugs). Our research and development  efforts in signal  transduction
incorporate the pioneering  accomplishments of our founding scientists, Dr. Axel
Ullrich of Max-Planck-Institut  fur Biochemie and Dr. Joseph Schlessinger of New
York University Medical Center.


         SUGEN is developing new therapeutic  approaches to diseases through its
development of small molecule  inhibitors  that regulate  particular  signalling
pathways.  We currently have three  anti-cancer  drugs in clinical  development,
including novel anti-tumor  cytostatic agents and angiogenesis  inhibitors which
inhibit the formation of new blood vessels that feed tumor cells. In addition to
our current  focus in  oncology,  SUGEN is applying its  technology  platform to
identify  and  validate  novel  targets  for  a  range  of  potential   clinical
applications. Our current drug product candidates include:

         o  SU101, our most advanced cytostatic product candidate,  inhibits the
            signalling  pathway  regulated  by a TK  receptor  for the  chemical
            messenger  secreted by  platelets,  blood  components  required  for
            clotting.  This  receptor  is known as the  platelet-derived  growth
            factor  receptor  or PDGF TK.  SUGEN  and  others  have  shown  that
            imbalances in the  signalling  pathway of PDGF TK are  implicated in
            significant  subsets of certain types of cancers,  including  brain,
            prostate, lung and ovarian. We initiated a Phase III clinical trial,
            which is a study involving a large number of human patients designed
            to  demonstrate   statistically   significant   drug  efficacy,   in
            refractory glioblastoma,  an aggressive type of brain cancer, in the
            first quarter of 1998.  We expect to conduct an interim  analysis by
            the end of 1999. We are also conducting a parallel Phase II clinical
            trial,  which is a study  involving a small number of human patients
            designed to demonstrate non-statistically significant drug efficacy,
            of  SU101  as  single  agent  therapy  for   refractory   anaplastic
            astrocytoma,  another type of malignant  brain  tumor.  In 1997,  we
            initiated a Phase II  clinical  trial of SU101 in  combination  with
            BCNU, the chemotherapy  drug that is part of the standard  treatment
            regimen  in newly  diagnosed  brain  cancer  patients.  We expect to
            complete this study this year. We are also  conducting a pilot study
            of SU101 in combination  with  mitoxantrone,  in  preparation  for a
            pivotal Phase III trial as  combination  therapy in the  early-stage
            treatment  of  prostate  cancer  patients  who have  failed  hormone
            therapy (hormone therapy  currently is the most common treatment for
            prostate  cancer).  We plan to begin this Phase III study later this
            year.  In addition,  we have ongoing  Phase II trials in ovarian and
            non small cell lung  cancers,  that are scheduled to be completed in
            mid 2000. To date, over 400 patients have been treated with SU101 in
            13 SUGEN-sponsored clinical trials.

         o  SU5416,  our lead  angiogenesis  inhibitor,  inhibits  the  receptor
            called  Flk-1/KDR TK. SUGEN  believes  SU5416 can inhibit the growth
            and  spread of  cancer  by  preventing  the  formation  of new blood
            vessels  (angiogenesis)  required  to nourish  the tumor by blocking
            this targeted  receptor.  In September  1997,  we initiated  Phase I
            clinical  testing to demonstrate  drug safety.  To date,  SU5416 has
            shown an excellent  safety profile in over 100 patients with a range
            of solid tumors, including advanced colorectal,  lung and renal cell
            cancers,  and AIDS-related  Kaposi's sarcoma.  In addition,  we have
            observed anecdotal  indications of activity in a number of patients,
            including  prolonged periods of stable disease and some instances of
            tumor shrinkage. After extensive consultation with numerous oncology
            opinion  leaders and the FDA, we announced  plans to accelerate  the
            development  of SU5416  with the  initiation  of Phase III  clinical
            trials  in non  small  cell lung and  colorectal  cancers  and Phase
            II/III  studies in  AIDS-related  Kaposi's  sarcoma in the U.S.  and
            Europe  this  year.  Meanwhile,  we will  be  working  with  certain
            investigators  on  National  Cancer  Institute  sponsored  Phase  II
            studies in other cancer indications.  This strategy may expedite the
            commercialization  of SU5416,  which has the potential to become the
            first  specific  angiogenesis  inhibitor  to reach the U.S.  market.
            However, we cannot predict whether this  commercialization  strategy
            will result in  accelerated  commercialization  of SU5416 or whether
            other angiogenesis inhibitors will receive regulatory approval prior
            to any approval of SU5416.


         o  SU6668,  our third novel  anti-cancer  drug candidate,  combines two
            strategies for blocking tumor growth  through its  angiogenesis  and
            cytostatic  anti-tumor  activity.  It  selectively  blocks  multiple
            targets  involved in the growth and spread of tumors,  including the
            Flk-1/KDR, PDGF and fibroblast growth factor (FGF) receptors. SU6668
            is  currently  in Phase I clinical  trials in Europe and in the U.S.
            using intravenous and oral formulations,  respectively.  SUGEN hopes
            to conclude both studies by the end of the year.

         o  We are also  pursuing  additional  cancer-related  drug  development
            programs,   including   Pan-Her,   Met-TK,   CDK2,  GRB2  and  other
            proprietary  programs,   many  of  which  have  lead  compounds  now
            undergoing pharmacology studies.  However, we cannot predict



                                       3
<PAGE>


            whether lead compounds will emerge in any of these programs in 1999,
            or at all.

         o  We are also applying our drug discovery and development  platform to
            areas  outside   oncology,   including   ophthalmology,   rheumatoid
            arthritis, cardiovascular disease, diabetes and immunology.

         SUGEN has  collaborated  with a number of entities in its  research and
development  activities  to date.  Our  current  collaborators  include:  Zeneca
Limited,  ASTA Medica  Aktiengesellschaft  of Germany,  Allergan,  Inc.  and its
affiliate,  Vision  Pharmaceuticals,  L.P., Taiho  Pharmaceutical  Ltd., ProChon
Biotech Ltd. and Esteve S.A. of Spain.

         We were  incorporated  in Delaware in 1991.  Our executive  offices are
located at 230 East Grand Avenue, South San Francisco, California 94080, and our
telephone  number is (650) 553-8300.  "SUGEN" is our trademark.  This prospectus
also contains trademarks of other companies.

Recent Developments


         Merger  Announced  with  Pharmacia & Upjohn.  On June 15,  1999,  SUGEN
entered into an Agreement and Plan of Merger with Pharmacia & Upjohn, Inc. Under
the terms of the agreement,  Pharmacia & Upjohn would acquire complete ownership
of SUGEN with each  share of SUGEN  stock  exchanged  for  approximately  $31 of
Pharmacia & Upjohn  stock,  so long as the average  price of  Pharmacia & Upjohn
stock  is  between  $60.16  and  $49.22  at  the  time  of  the  closing  of the
transaction.  In no event would SUGEN  stockholders  receive less than .515 of a
share of  Pharmacia  & Upjohn  common  stock,  nor more  than .630 of a share of
Pharmacia  & Upjohn  stock  for each  share of SUGEN  common  stock.  The  exact
exchange  ratio would be based on the average  price of Pharmacia & Upjohn stock
prior to the closing of the merger.  The transaction is intended to be accounted
for as a pooling  of  interests  and to  qualify  as a  tax-free  exchange.  The
transaction  has  received  the  approval  of the  Boards of  Directors  of both
Pharmacia  &  Upjohn  and  SUGEN  and is  subject  to the  approval  by  SUGEN's
stockholders  and other  customary  closing  conditions,  including  receipt  of
regulatory approvals.  Under certain  circumstances,  if the merger agreement is
terminated,  Pharmacia & Upjohn  would have the right to purchase up to 19.9% of
SUGEN's common stock and would have the right to receive from SUGEN a fee of $17
million and repayment of its  expenses.  Investors  should read SUGEN's  Current
Report on Form 8-K,  filed with the SEC on June 21, 1999,  for more  information
regarding the proposed merger and merger agreement.


         This Offering.  On March 24, 1999, we sold to the selling  stockholders
listed in this  prospectus  $28,000,000  aggregate  principal  amount of our 12%
Senior  Convertible Notes due 2002 (Notes) and warrants to purchase  $21,000,000
aggregate  principal amount of additional 12% Senior  Convertible Notes (Warrant
Notes).  The Notes and Warrant Notes were sold  pursuant to Securities  Purchase
and Exchange  Agreements,  dated as of March 19, 1999.  SUGEN is registering for
resale up to  2,461,943  shares  of  common  stock  underlying  the  convertible
securities  sold to the selling  stockholders  in March 1999.  The shares  being
registered for resale include:

         o        up to 1,365,849  shares that may be issued upon  conversion of
                  the Notes;

         o        up to 1,024,386  shares that may be issued upon  conversion of
                  the Warrant  Notes which are issuable upon exercise of our 12%
                  Senior Convertible Note Purchase Warrants (Warrants);

         o        up to  2,461,943  shares that may be issued  upon  exercise of
                  common stock warrants that we may issue upon redemption of the
                  Notes, Warrants and Warrant Notes (all or some of these shares
                  would be  issued  in lieu of the  same  number  of the  shares
                  indicated above); and


         o        an indeterminate  number of additional shares as may from time
                  to time  become  issuable  upon  conversion  of the  Notes and
                  Warrant Notes,  or upon exercise of the common stock warrants,
                  by reason of stock splits,  stock  dividends and other similar
                  transactions.




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<PAGE>



                                  RISK FACTORS

         This prospectus contains forward-looking  statements.  These statements
relate to  future  events or our  future  clinical  or  product  development  or
financial  performance.   In  some  cases,  you  can  identify   forward-looking
statements  by phrases  such as "may,"  "will,"  "should,"  "expects,"  "plans,"
"anticipates,"  "believes,"  "estimates," "predicts," "potential," or "continue"
or the negative of such terms and other  comparable  phrases.  These  statements
reflect  only our  current  expectations.  Actual  events or results  may differ
materially.  In evaluating these statements,  you should  specifically  consider
various factors, including the risks outlined below. These factors may cause our
actual results to differ materially from any forward-looking  statements. We are
not  undertaking  any  obligation  to  update  any  forward-looking   statements
contained in this prospectus to reflect any future events or developments.

         You should  carefully  consider the following risk factors and warnings
before making an investment decision. The risks described below are not the only
risks we face.  Additional risks that we do not yet know of or that we currently
think are  immaterial  may also impair our  business  operations.  If any of the
events or circumstances  described in the following risks actually  occurs,  our
business,  financial  condition,  or results of  operations  could be materially
adversely  affected.  In such case,  the trading price of our common stock could
decline, and you may lose all or part of your investment.  You should also refer
to the other  information set forth in this prospectus,  including our financial
statements and the related notes.


         The following  risks relate to the  consummation of the proposed merger
with Pharmacia & Upjohn.


SUGEN  stockholders  may receive  less than $31.00  worth of  Pharmacia & Upjohn
common stock for each share of SUGEN common stock.

         Upon consummation of the merger,  each share of SUGEN common stock will
be converted into a fraction of a share of Pharmacia & Upjohn common stock equal
to the  exchange  ratio as set forth in the  merger  agreement.  If the  average
closing  price of  Pharmacia  &  Upjohn  common  stock is equal to or less  than
$49.21875  during the 20 trading day period ending three days prior to the SUGEN
stockholders'  special meeting, you will receive 0.51533 of a share of Pharmacia
& Upjohn  common  stock,  which may be worth less than $31.00 a share,  for each
share of SUGEN common stock.  SUGEN cannot terminate the merger agreement in the
event  such  initial  value is below  $31.00.  The  actual  number  of shares of
Pharmacia & Upjohn  common  stock to be issued to holders of SUGEN  common stock
will not be  determined  until  three  trading  days prior to the SUGEN  special
meeting of stockholders.  The volume weighted average closing price of Pharmacia
& Upjohn common stock for the 20 trading day period may be lower than the market
price as of the date of  execution of the merger  agreement,  the date hereof or
the date on which stockholders vote on the merger.


         The following  risks relate to the operation of SUGEN as an independent
entity  in the  event  the  proposed  merger  with  Pharmacia  &  Upjohn  is not
consummated.


Our  product  candidates  are at an early  stage of  development,  and if we are
unable to successfully develop and commercialize products, we would not generate
revenues.

         To date, none of our product candidates have been  commercialized.  All
of our  product  candidates  are in early  stages of  development,  and our drug
discovery and development  methods are relatively new and untested.  We face the
risks of failure  inherent in  developing  biotechnology  products  based on new
technologies.  To achieve profitable operations on a continuing basis, we, alone
or  with  collaborative  partners,   must  successfully  develop,   manufacture,
introduce  and  market  our  proposed  products.  To  date,  three  of our  drug
candidates  have entered human clinical  testing.  We cannot predict  whether we
will be able to develop any commercial  products.  Products,  if any,  resulting
from our research and  development  programs are not expected to be commercially
available until at least 2001,  even if successfully  developed and proven to be
safe and effective.

If we are unable to raise  additional  funds, we may not be able to continue our
product development efforts, and the future viability of our business will be at
risk.

         Our product development programs are very costly. We expect to continue
to spend substantial  funds for our research,  preclinical and clinical testing,
and operations for the foreseeable future. Our future cash liquidity and capital
requirements will depend on many factors, including:

         o  continued  scientific  progress  of  our  research  and  development
            programs;

         o  our ability to establish collaborations with partners;

         o  progress  of  our   preclinical   and  clinical  trials  of  product
            candidates;

         o  the time and costs of obtaining regulatory clearances;

         o  the costs  involved in obtaining  and  protecting  our  intellectual
            property rights;

         o  competing technological developments;

         o  changes in our existing research and commercialization collaboration
            arrangements; and

         o  costs associated with commercialization of our products.

         As of March 31, 1999, we had  approximately  $61.9 million available in
cash and short-term investments,  and we incurred approximately $19.2 million in
development and operating  expenses in the first quarter of fiscal year 1999. We
believe  that  our  existing  capital  resources,  together  with  facility  and
equipment lease lines, the anticipated revenues from current  collaborations and
projected interest income,  will support our current and planned operations into
2000.  However,  we cannot  predict  whether our  assumed  levels of revenue and
expense will prove accurate.


         We may need to raise additional funds if:

         o        our lead product candidates, SU101, SU5416 and SU6668, are not
                  sufficiently safe or effective to be commercialized;

         o        we do not establish future collaborations with partners;

         o        our clinical  trials of SU101,  SU5416 and SU6668 are delayed,
                  are  not   successful  or  are  more  costly  than   currently
                  predicted; or

         o        additional clinical trials are required for product approval.

         We cannot predict whether we will be able to raise  sufficient funds in
the future.  If adequate funds are not  available,  we may be unable to fund our
research and development  efforts,  conduct our clinical trials, or successfully
commercialize and market our product candidates. If we raise additional funds by
issuing equity securities,  our existing stockholders may experience substantial
dilution.  If we raise additional funds through collaborative  arrangements,  we
may be required to give up some  commercialization  rights to our  technologies,
product candidates or products.


We have only a limited operating history,  and we expect to continue to generate
losses.

         We may never achieve a profitable level of operations. To date, we have
engaged  primarily in research and development.  Our development and general and
administrative  expenses have resulted in  substantial  losses.  As of March 31,
1999, we had an accumulated  deficit of approximately  $145.5 million. We expect
our losses to continue at least  through 2001.  We expect  cumulative  losses to
increase  substantially  as our  research  and  development  efforts,  including
preclinical and clinical testing, are expanded. Our ability to become profitable
will depend on our ability to, among other things:


         o        obtain and protect our intellectual property rights;



                                       5
<PAGE>

         o        complete our product development;

         o        obtain product regulatory approvals;

         o        manufacture and market our proposed products; and

         o        achieve market acceptance for our products.



We rely  heavily on  collaborations  for the  discovery,  development,  clinical
testing and  commercialization  of our product  candidates.  Our  dependence  on
collaborators  may delay or impair our ability to generate revenues or adversely
affect our profitability.

         Our  strategy  for  the  discovery,   development,   clinical  testing,
manufacturing and  commercialization  of our proposed products includes entering
into various  collaborations with corporate partners,  licensors,  licensees and
others,  and is dependent upon the subsequent  success of these outside partners
in performing their responsibilities. If our partners are not successful, we may
not be able  to  continue  our  product  development  efforts,  and  the  future
viability of our company will be at risk. Currently, we have collaborations with
the following partners:


         o        Allergan, Inc. and its affiliate Vision Pharmaceuticals, L.P.

         o        ASTA Medica Aktiengesellschaft


         o        Esteve S.A. of Spain


         o        Max-Planck Society

         o        National Cancer Institute

         o        New York University Medical Center

         o        ProChon Biotech Limited

         o        Taiho Pharmaceutical Ltd.

         o        Zeneca Limited


         Our  ability to  develop,  test,  manufacture  and market our  proposed
products  successfully depends  significantly on our partners' performance under
these,  and future,  collaborations.  We cannot control the amount and timing of
resources to be devoted to our collaborations by corporate  partners.  We cannot
be  certain  that our  partners  will  perform  their  obligations  under  these
collaborations  or  that  we will  succeed  in  identifying  lead  compounds  or
developing  commercial products from these or future  collaborations.  We cannot
predict  whether our  partners  or any future  partners  will  pursue  their own
existing or alternative  technologies  in preference to those being developed in
our collaborations.  Generally,  our collaborative  arrangements do not obligate
our  partners to devote a specific  level of funding to research  related to our
potential  products.  Our collaborative  partners are free to select the methods
they use in pursuing  their  research  targets.  We cannot  predict  whether our
collaborative  partners  will  continue  to  conduct  research  related  to  our
potential  products or conduct  research and select research targets in a manner
consistent  with  our  best  interests.  If our  collaborative  partners  do not
continue to conduct  research related to our potential  products,  our business,
financial  condition  and results of operations  could be  materially  adversely
affected.  We also cannot predict whether we will derive any additional  revenue
from such arrangements over and above the contractual payment amounts.

         o        Termination  of  collaborations.  The  termination or material
                  reduction  in the  scope of our  collaborations  could  have a
                  material adverse effect on our business.  Unless extended, our
                  research  collaboration with Allergan expires in October 1999,
                  research funding under our  collaboration  with Zeneca expires
                  in March 2000, and our collaboration  with New York University
                  expires in September 2001. Our  collaboration  with Max-Planck
                  expired in August  1997,  and the  restatement  and renewal of
                  this arrangement is currently under negotiation.  We expect to
                  complete  written  documentation  of  the  renewed,   modified
                  collaboration  that is consistent with the oral  understanding
                  Max-Planck  and  SUGEN  have  been  operating  under  to date.
                  However,  we cannot  predict  whether any of these  agreements
                  will be renewed on favorable  terms, if at all.  Additionally,
                  our   collaborations   may   be   terminated   under   certain
                  circumstances. If any of our partners terminates its agreement
                  or fails to provide  adequate  funding to support our research
                  and  product  development  efforts,  we will  need  to  obtain
                  additional  funding from other sources and will be required to
                  devote   additional   resources  to  the  development  of  our
                  products. We cannot predict whether we would be able to find a
                  suitable  substitute partner in a timely manner, on reasonable
                  terms, or at all. If we fail to find a suitable  partner,  our
                  research,  development or commercialization of certain planned
                  products would be delayed significantly,  which would cause us
                  to incur additional expenditures. In addition,  termination of
                  a  collaboration  may cause us to give up rights to technology
                  or products jointly developed under the collaboration.

         o        Future collaborations.  In addition, we cannot predict whether
                  we  will  be  able  to  negotiate   additional   collaborative
                  arrangements  on  acceptable  terms,  if at all,  or that such
                  future  collaborations will be successful.  To the extent that
                  we choose not to or are unable to establish such arrangements,
                  it would require  substantially  greater  capital to undertake
                  research,  development and marketing of our proposed  products
                  at our own expense. In addition,  we may encounter significant
                  delays in  introducing  our  proposed  products  into  certain
                  markets or find that the  development,  manufacture or sale of
                  our proposed products in such



                                       6
<PAGE>

                  markets  is   adversely   affected  by  the  absence  of  such
                  collaborative agreements. Additionally, if we do not establish
                  such  future  collaborations,  we  may  encounter  significant
                  delays  in  the  development  and   commercialization  of  our
                  proposed  products  which would cause us to incur  substantial
                  additional expenditures.


If we are  unable to  protect  our  intellectual  property,  we may be unable to
prevent other companies from using our technology in competitive products. If we
are unable to operate our  business  without  infringing  intellectual  property
rights of others,  we may be prevented from developing and  commercializing  our
product candidates.

         Our technology will be protected from  unauthorized  use by others only
to the extent that it is covered by valid and enforceable patents or effectively
maintained as trade  secrets.  As a result,  our success  depends in part on our
ability to:


         o        obtain patents;

         o        protect trade secrets;

         o        operate  without  infringing  on  the  proprietary  rights  of
                  others; and

         o        prevent others from infringing on our proprietary rights.

         As of June 14,  1999,  we held  exclusive  rights to at least 60 issued
U.S. patents, exclusive rights to at least 10 U.S. patent applications for which
notices  of  allowances  had been  received,  and had  filed  or held  exclusive
licenses to approximately 110 U.S. patent  applications.  We also hold exclusive
rights to many  corresponding  foreign patent  applications.  Patent matters for
biotechnology  companies,  especially  concerning  cell  receptors  and  the DNA
encoding them, involve complex legal and factual questions, so we cannot predict
the  availability and scope of patent  protection.  We cannot be certain that we
will develop  products  that are  patentable or that patents will issue from our
pending  applications.  In addition,  we cannot  predict  whether our patents or
patents that we license from others will be  enforceable  and afford  protection
against  competitors.  Our  patents or patent  applications,  if issued,  may be
challenged,  invalidated or  circumvented.  Our patent rights may not provide us
with proprietary  protection or competitive  advantages against competitors with
similar  technologies.  Others may independently develop technologies similar to
ours or  independently  duplicate our  technologies.  Due to the extensive  time
required  for  development,  testing  and  regulatory  review  of our  potential
products,  our patents may expire or remain in existence for only a short period
following commercialization. This would reduce or eliminate any advantage of the
patents.


         We cannot be  certain  that we were the first to make the  products  or
processes  covered by each of our issued or pending patent  applications or that
we were the first to file patent applications for such products or processes.  A
number of pharmaceutical  companies,  biotechnology companies,  universities and
research  institutions have filed patent applications or received patents in the
field of TKs, TPs and STKs and their related signalling pathways. Our commercial
success will depend, in part, on not infringing our competitors' patents and not
breaching technology licenses we obtain. We have been notified from time to time
of claims that we may be infringing other's  intellectual  property rights. Some
companies  have filed  patent  applications  or been  granted  patents  covering
subject matter  potentially  useful or necessary to us or  conflicting  with our
patents and patent  applications.  Such conflicts could significantly reduce the
scope of our issued or licensed patents. In addition, we may need to license the
right to use  third-party  patents and other  intellectual  property to continue
development  and marketing of our  products.  We may not be able to acquire such
required  licenses  on  acceptable  terms,  if at all.  If we do not obtain such
licenses,  we may need to design around other parties'  patents or we may not be
able to proceed with the development, manufacture or sale of our products.



         o        SU101.  SU101, a compound generally known as leflunomide,  was
                  discovered  more  than 17 years  ago.  In  December  1997,  we
                  received two U.S.  patents  relating to methods of using SU101
                  for  treating  various  diseases,  including  certain  cancers
                  characterized by inappropriate  PDGF-R activity.  We currently
                  own the exclusive  rights to one of the patents.  We have been
                  assigned  exclusive  world-wide rights to the other patent and
                  the corresponding foreign patent applications from all but one
                  party.  We  cannot  predict  whether   negotiations  with  the
                  remaining  party  to  acquire  the  remaining  rights  will be
                  successful.  In addition,  we have filed  several U.S.  patent
                  applications, and corresponding  foreign patent  applications,
                  covering  different  formulations  of SU101  and  their use to
                  treat various diseases.  Currently,  we have received two U.S.
                  patents  relating  to SU101  formulations.  These two  patents
                  cover  the  SU101   formulation   that  we  believe   will  be
                  commercially marketed. While we plan to commercialize SU101 in
                  certain major markets outside the U.S.  through our affiliates
                  or licensees, we cannot predict whether we will receive patent
                  protection outside the U.S.


                           Hoechst AG holds a number of U.S. and foreign patents
                  and has filed U.S. and foreign  patent  applications  covering
                  different compositions and pharmaceutical uses of leflunomide,
                  including  the use of  leflunomide  for  treating  cancer.  We
                  believe our research and  development and clinical trials with
                  SU101 in the U.S. are protected from claims of infringement of
                  the Hoechst U.S.  patents  because such  activities  are being
                  conducted for the development and submission of information to
                  the FDA for regulatory approval.  However,  similar protection
                  may not be  available  outside  the U.S.  Although  we  cannot
                  predict if SU101 will be approved by the FDA for  marketing in
                  the U.S., we believe that some of Hoechst's  U.S.  patents may
                  have  expired by the time  marketing  of SU101 begins and that
                  Hoechst's  other U.S.  patents will either not be infringed by
                  our  making,  using and  selling  of SU101 in the U.S.  or are
                  subject to claims that they are not valid,  thereby permitting
                  us to  produce  and  market  SU101  without  valid  claims  of
                  infringement  of  the  Hoechst  patents.  However,  we  cannot
                  predict whether a court will agree with our beliefs  regarding
                  invalidity and non-infringement of Hoechst's issued patents or
                  that the term of Hoechst's issued patents will be extended. To
                  date,  Hoechst has not initiated legal proceedings  against us
                  concerning  possible patent  infringement.  However, we cannot
                  predict  whether  Hoechst will assert claims against us in the
                  future.  If a court found us to be  infringing  a valid patent
                  issued to Hoechst covering the use of leflunomide for treating
                  cancer,  we would be required to obtain a license from Hoechst
                  to  manufacture or sell SU101 for treating  cancer.  We cannot
                  predict  whether  we  would be able to  reach  agreement  with
                  Hoechst for


                                       7
<PAGE>

                  a license  for SU101  upon  favorable  terms,  if at all.  The
                  assertion of any infringement  claims, even if resolved in our
                  favor, could result in substantial costs and expenses to us.


        o         SU5416.  In August 1998, we received a U.S.  patent  covering,
                  among  other  things,  SU5416  and  methods  of using  SU5416.
                  Currently,   we  have  related  foreign  patent   applications
                  pending, including in Japan and the European community. Except
                  in  Japan,  we  hold  exclusive   worldwide  rights  to  these
                  applications.  If foreign patents are not issued,  the failure
                  to  receive  foreign  patent   protection   could   materially
                  adversely affect our business, financial condition and results
                  of operations.


         o        SU6668.  The  compound  SU6668 is  generically  covered  by an
                  issued U.S. patent.  That is, SU6668 is encompassed by some of
                  the  claims  in the  issued  U.S.  patent,  but  SU6668 is not
                  specifically  recited in the claims. In general,  such generic
                  coverage provides adequate patent protection.  However, it may
                  be advantageous  under certain  circumstances to obtain claims
                  that  specifically  recite SU6668.  For example,  a competitor
                  that  challenges  the  validity  of a  patent  may be  able to
                  invalidate a claim that encompasses many different  compounds,
                  but not a claim that  recites one specific  compound.  We have
                  filed a U.S.  utility  application and  corresponding  foreign
                  patent applications  specifically claiming SU6668. We hold the
                  exclusive  worldwide rights to these  applications,  except in
                  Japan.  We cannot  predict  whether  patents  will issue which
                  specifically  recite  SU6668  or that  the  term  of any  U.S.
                  patents will exceed that of the term of the  outstanding  U.S.
                  patent that generically  covers SU6668. The failure to receive
                  U.S. and foreign patent protection could materially  adversely
                  affect  our  business,  financial  condition  and  results  of
                  operations.

         We may face litigation to defend against claims of infringement, assert
claims of  infringement,  enforce  our  patents,  protect  our trade  secrets or
know-how,  or determine  the scope and validity of others'  proprietary  rights.
Patent  litigation is costly and would divert our attention  and  resources.  In
addition, we may be involved in interference  proceedings declared by the United
States  Patent and  Trademark  Office to  determine  the  priority of our patent
applications  compared to the patent  applications of one or more third parties.
Litigation or interference  proceedings  could have a material adverse effect on
our  business,  financial  condition and results of  operations,  including as a
result of any delay in the marketing of our products due to  litigation  related
to our  intellectual  property.  Additionally,  we could be  unsuccessful in our
efforts to enforce our intellectual property rights or obtain patent protection.
We have received  letters from at least two third parties  indicating  that they
believe we may be practicing  their  proprietary  technology.  We do not believe
that we practice any validly claimed subject matter in which these third parties
possess an ownership  interest.  However,  we cannot  predict  whether the third
parties  will agree with our position or that a court will agree with our belief
regarding invalidity and/or non-infringement.  As set forth above, any resulting
litigation could materially  adversely affect our business,  financial condition
and results of operations.



If we are not  able to  demonstrate  the  safety  and  efficacy  of our  product
candidates in our clinical trials or our clinical  trials are delayed,  we would
not be able to market our  products  in the United  States or abroad on a timely
basis, if at all.

         Clinical  development,   including  preclinical  testing,  is  a  long,
expensive and uncertain process. Any of our clinical trials may not be correctly
designed  to result in data  necessary  to prove the safety and  efficacy of our
product  candidates.  It may take us several years to complete our testing,  and
failure can occur at any stage of testing.  We cannot rely on interim results of
trials to  necessarily  predict their final results,  and acceptable  results in
early trials might not be repeated in later trials. A number of companies in the
pharmaceutical and biotechnology  industries have suffered  significant setbacks
in advanced clinical trials, even after promising results in earlier trials. Any
trial may fail to  produce  results  satisfactory  to the FDA.  Preclinical  and
clinical data can be interpreted in different ways, which could delay,  limit or
prevent regulatory approval. Negative or inconclusive results or adverse medical
events  during a trial  could  cause a trial to be  repeated  or a program to be
terminated.


         The rate of completion of our clinical trials is dependent upon,  among
other  factors,  the  rate of  patient  enrollment.  Patient  enrollment  can be
affected  by the size of the  available  patient  population,  the nature of the
trial  protocol,  the  location  of clinical  sites and the patient  eligibility
criteria  for the study.  Delays in patient  enrollment  may result in increased
costs,  delays or  termination of clinical  trials,  which could have a material
adverse effect on our business. In addition,  because we have a limited clinical
staff, we generally rely on third-party  clinical  investigators  to conduct our
clinical trials,  and as a result, we face certain  additional  delaying factors
outside our control. These factors include:

         o        third-party  investigator failure to perform their contractual
                  obligations;

         o        third-party investigator failure to meet regulatory standards;

         o        inadequately  trained or  insufficient  personnel at the study
                  site; and

         o        delays in approvals from a study site's review board.


         We  cannot  predict  whether  we  will be able  to  submit  a new  drug
application  as  scheduled  if clinical  trials are  completed  or when new drug
applications  will be reviewed  and cleared by the FDA, if at all. For our three
cancer drug candidates  currently in clinical trials,  we cannot be certain that
planned trials will begin on time, and we cannot predict whether clinical trials
will be completed on schedule.  We cannot predict whether any trials will result
in marketable products or that any products will be commercially successful even
if approved for  marketing.  Our product  development  costs will increase if we
have  delays in  testing  or  approvals.  If the  delays  are  significant,  our
business,  financial  condition  and results of  operations  will be  materially
adversely affected.


Clinical  testing may uncover  negative side effects for our product  candidates
which may delay or prevent commercialization of such drug products.

         We face  the  risk  that any  drug  candidate  may be toxic or  produce
negative side effects in animals or humans when given in high doses or over long
periods of time.  We cannot  predict  whether  unacceptable  toxicities  or side
effects will occur at any time in any toxicological




                                       8
<PAGE>


study or human clinical trial of our proposed products.  If our products produce
unacceptable  toxicities or side effects in our clinical testing,  we and/or the
FDA  may  interrupt,  limit,  delay  or  stop  the  development  of our  product
candidates.  Even if a product receives  regulatory  clearance,  it may later be
shown to be unsafe or ineffective,  thus limiting the product's use or requiring
its  removal  from the  market.  We cannot  predict  whether  any of our product
candidates will be safe and effective when administered to patients.



Our products have never been manufactured on a commercial scale, and our lack of
manufacturing expertise may impair our ability to generate revenues.

         We  have no  manufacturing  facilities  and  thus  rely on  third-party
manufacturers to produce our compounds for research and development, preclinical
and clinical  purposes.  If we cannot  contract  for a sufficient  supply of our
compounds on acceptable  terms,  or if our  manufacturers  experience  delays or
difficulties,  our preclinical and clinical testing schedule would be delayed. A
delay in our  testing  schedule  would  result in a delay in the  submission  of
products for  regulatory  approval and the  subsequent  commercial  sale of such
products,  which would  materially  adversely  affect our  business.  Also,  any
manufacturer will have to prove both to us and to the FDA that its manufacturing
process complies with government regulations. Our products under development, as
well as many of their  components,  have never been manufactured on a commercial
scale.  It may be  difficult  or  impossible  to  economically  manufacture  our
products on a commercial  scale. We may need to identify and qualify  additional
manufacturers for commercial production.  We cannot be certain that our existing
manufacturers  or any new  manufacturer  will be able to  provide  the  required
quantities of our compounds on reasonable terms, or at all.

We have no sales and marketing  capability,  and our lack of sales and marketing
personnel and expertise may impair our ability to generate revenues.

         We  currently  have very  limited  sales,  marketing  and  distribution
capability.  We intend to rely on relationships with one or more  pharmaceutical
companies with established  distribution systems and sales forces to market some
of our proposed products.  In addition, we expect to market some of our proposed
products  directly.  Thus,  we must develop a marketing and sales force with the
necessary technical expertise.  If we do not establish sufficient in-house sales
and distribution capabilities or establish successful marketing, co-promotion or
licensing  arrangements with third parties,  we will not be able to successfully
market and commercialize our drug products.

If our  products  are not  accepted  by the  health  care  community,  including
physicians,  patients and health care  payors,  we may not be able to market and
commercialize our products, and our profitability may be adversely affected.

         We believe  that our ability to  commercialize  our product  candidates
effectively will depend on the safety,  efficacy and  cost-effectiveness  of our
products and the  availability  of adequate  insurance  reimbursement  for these
products.  The  treatment of cancer with  cytostatic,  as opposed to  cytotoxic,
therapy is a novel  method of  treating  cancer  that may not be accepted by the
health care community.  If cytostatic  cancer treatments are not accepted by the
health  care  community,  our  ability to  generate  revenues  may be  impaired.
Additionally,  even if our approach to the  treatment of cancer with  cytostatic
therapy is proven to be safe and  effective  and is  accepted by the health care
community,  our ability to successfully  commercialize  our products  depends in
part on obtaining  adequate  reimbursement  for product costs from  governmental
authorities  and private  health care  insurers  (including  health  maintenance
organizations).  Government  and  private  third-party  payors are  increasingly
attempting to contain  health care costs by limiting both the extent of coverage
and the  reimbursement  rate for new tests and  treatments.  If  government  and
private  third-party  payors do not  adequately  provide  reimbursement  for our
product  costs,  our products may not be accepted by the health care  community,
and our ability to  generate  revenues  may be  impaired.  Even if our  products
receive the necessary  regulatory and health care reimbursement  approvals,  our
products still may not achieve any significant degree of market acceptance among
physicians,  patients  and health care  payors.  We cannot  predict  whether our
technologies will be accepted rapidly or at all. If our products fail to achieve
market acceptance,  our business,  results of operations and financial condition
would be materially adversely affected.

If we fail to comply with extensive regulations enforced by domestic and foreign
regulatory authorities, the commercialization of our product candidates could be
prevented or delayed.

         Our products under  development  and  anticipated  future  products are
subject to extensive and rigorous  regulation by United States local,  state and
federal  regulatory  authorities and by foreign  regulatory  bodies. The FDA and
other regulatory agencies impose substantial requirements upon the manufacturing
and  marketing of products  such as those being  developed by our company or any
partner. The process of obtaining FDA and other required regulatory approvals is
long,  expensive  and  uncertain,  and delays or failures to receive  regulatory
approvals  may  prevent  us from  commercializing  our  products  and impair our
ability to generate  revenues.  The time  required for  regulatory  approvals is
uncertain and the process  typically  takes a number of years,  depending on the
type, complexity and novelty of the product. We may encounter significant delays
or excessive costs in our efforts to secure necessary approvals or licenses.


         To date, none of our product  candidates have received FDA approval for
commercialization.  The FDA may not approve any of our product  candidates if it
believes that any applicable regulatory criteria are not satisfied.  The FDA may
also require additional  testing for safety and efficacy,  which would delay our
commercialization  of our  product  candidates.  We cannot  predict  whether our
products  will  receive FDA  approval  in a timely  manner,  if at all.  Even if
approvals are obtained,  the  marketing and  manufacturing  of drug products are
subject  to  continuing  FDA  and  other   regulatory   requirements,   such  as
requirements to comply with good manufacturing practices, as defined by the FDA.
The failure to comply with such requirements could result in enforcement action,
which could  adversely  affect us and our business.  Later discovery of problems
with a product,  manufacturer or facility may result in additional  restrictions
on the product or  manufacturer,  including  withdrawal  of the product from the
market.  The government may impose new regulations  which could further delay or
preclude regulatory  approval of our potential  products.  We cannot predict the
impact  of  adverse  governmental  regulation  which  might  arise  from  future
legislative or administrative action.

         We intend to generate  product revenue from sales outside of the United
States.  Distribution  of our  products  outside  the United  States also may be
subject to extensive  government  regulation.  These regulations,  including the
requirements  for  approvals  or  clearance  to market,  the time  required  for
regulatory review and the sanctions imposed for violations,  vary by country. It
is uncertain  whether we will obtain  regulatory  approvals in such countries or
that we will be required to incur  significant costs in obtaining or maintaining
our  foreign  regulatory  approvals.  Failure  to  obtain  necessary  regulatory
approvals  or any other  failure to comply with  regulatory  requirements  could
result in reduced revenue and earnings.


We may not be able to  effectively  compete  against our  current and  potential
competitors.

         We operate in a rapidly  changing field,  and we expect our products to
encounter significant competition. Currently, other products and therapies exist
or are being developed that will compete



                                       9
<PAGE>

with the  products  that we are seeking to develop and market.  We face  intense
competition from large pharmaceutical companies,  including Zeneca, Novartis and
Bayer. We also compete with more established  biotechnology  companies,  such as
Genentech  and  Immuncy,  and even  smaller  companies  that form  collaborative
arrangements  with large  pharmaceutical  and biotechnology  companies,  such as
InCLONE and Entremed. Such competition is expected to increase. Our success will
depend in part on our ability to respond  quickly to medical  and  technological
changes  through the  development  and  introduction  of new  products.  Product
development  is risky and  uncertain,  and we  cannot  predict  whether  we will
develop our products  successfully.  Competitors'  products or technologies  may
make our products obsolete or non-competitive before we are able to generate any
significant  revenue.  Many of our  competitors  or potential  competitors  have
substantially  greater  financial  and  other  resources  than  we  have.  These
competitors,  academic  institutions  and  research  organizations  all may have
greater  experience in  preclinical  testing,  human  clinical  trials and other
regulatory approval procedures. Our ability to compete successfully will depend,
in part, on our ability to:

         o        attract and retain skilled scientific personnel;

         o        develop safe and efficacious products;

         o        obtain patent or other proprietary protection for our products
                  and technologies;

         o        obtain required regulatory approvals for our products;

         o        maintain access to  sufficiently  broad libraries of compounds
                  for screening potential targets;

         o        be early entrants to the market; and

         o        manufacture,  market and sell our products,  independently  or
                  through collaborations.

We cannot predict  whether our  competitors  will develop more effective or more
affordable  products or achieve product patent protection and  commercialization
earlier  than we will.


Failure to attract and retain key employees could adversely  affect our research
and development  efforts,  our ability to conduct clinical trials or our ability
to market and commercialize our product candidates.

         Because  of the  scientific  nature of our  business,  we depend on the
principal members of our management and scientific staff,  including our Science
Advisory Board and Clinical Advisory Board. We do not maintain "key person" life
insurance on any of our officers,  employees or consultants.  Our future success
will  depend  largely  on our  ability  to attract  and  retain  highly  skilled
executive,  scientific and managerial personnel.  Competition for such personnel
is intense.  We cannot  predict  whether we will be successful in attracting and
retaining  such  personnel.  In  July  1998,  we  entered  into  a  compensation
arrangement  with  Stephen  Evans-Freke,  our  Chairman  of the  Board and Chief
Executive Officer, related to Mr. Evans-Freke's commitment to serve as our Chief
Executive  Officer  until at  least  June 30,  1999.  Generally,  we do not have
employment  agreements  with  our  executive  officers  providing  for a term of
service, and we do not have any agreement with Mr. Evans-Freke providing for his
service as Chief Executive  Officer after June 30, 1999. The failure to maintain
our executive,  management and  scientific  staff and to attract  additional key
personnel could materially  adversely affect our business,  financial  condition
and  results of  operations  and may  prevent  us from  achieving  our  business
objectives.  Although we intend to provide incentive compensation to attract and
retain our key personnel, we cannot guarantee these efforts will be successful.

If we are not successful in our attempt to commercialize  our products in Europe
through  European  national  partners,  our ability to generate  revenues may be
impaired and our profitability may be adversely affected.

         Our strategy for the  commercialization  of our product  candidates  in
Europe  includes  entering into agreements with a limited number of distribution
partners  who bring strong local  presence on a  pan-European  scale rather than
with a single  international  pharmaceutical  company. We cannot predict whether
this commercialization strategy will prove to be successful.


         This strategy may require more capital than licensing  European  rights
to  product  candidates.  We cannot  predict  whether  we will be able to obtain
sufficient capital to pursue this strategy.  Our strategy may cause SUGEN Europe
to bear  research and  development  expenses for a longer period of time without
sharing the costs with a corporate partner. Thus, if products are not ultimately
successful,  we may have large research and  development  losses.  We may not be
able  to  establish  arrangements  with  appropriate  partners  in all  relevant
countries on reasonable terms, or at all. Our success will depend  significantly
on our partners' ability and willingness to perform their obligations. We cannot
predict  whether  our  partners  will  perform  their   obligations   under  any
commercialization  arrangements.  Additionally,  contracting with numerous local
partners  instead of one large European partner may be harder to manage and have
higher administrative costs. In addition, our commercialization arrangements may
be effected by the European  Union  requirements  for free trade within  Europe.
Price sensitivities in individual  markets,  including Spain, where SUGEN Europe
recently  entered  into a  distribution  arrangement,  may  impact  the terms of
collaborations  and the pricing of our  products in  individual  markets.  As is
generally the case for trading within the European Union,  the ability of buyers
in countries  throughout the European Union to purchase  products in lower price
markets  may  impact  SUGEN   Europe's   ability  to  enter  into   distribution
arrangements   for   additional   European   markets  and  the  terms  of  these
arrangements.


         Our European operations are subject to the additional risks inherent in
international business activities, including:


         o        the general  economic  conditions in the countries in which we
                  and our affiliates operate;

         o        overlapping tax structures;

         o        unexpected changes in regulatory requirements;


                                       10
<PAGE>

         o        compliance with various foreign laws and regulations;

         o        longer accounts receivable payment cycles in some countries;


         o        import and export licensing requirements;

         o        trade restrictions;

         o        exchange controls; and

         o        changes in tariff and freight rates.


The  market  price of our stock may be highly  volatile  which  could  result in
substantial losses for individual stockholders.

         Our common stock currently  trades on the Nasdaq National  Market.  The
market prices for  securities of emerging  biotechnology  companies like us have
been highly volatile.  Announcements may have a significant impact on the market
price of our common stock. Such announcements may include:


         o        biological or medical discoveries;

         o        technological  innovations or new commercial products by us or
                  our competitors;

         o        developments concerning proprietary rights,  including patents
                  and litigation matters;

         o        regulatory  developments in both the United States and foreign
                  countries;

         o        public concern as to the safety of new technologies;

         o        developments  in our  relationships  with  current  or  future
                  collaborative partners;

         o        general market conditions;

         o        comments  made by  analysts,  including  changes in  analysts'
                  estimates of our financial performance; and

         o        quarterly fluctuations in our revenue and financial results.

         The stock market has from time to time  experienced  extreme  price and
volume  fluctuations,  which have  particularly  affected the market  prices for
emerging  biotechnology  companies,  and which have often been  unrelated to the
operating  performance of such companies.  These broad market  fluctuations  may
adversely  affect the market price of our common stock.  For example,  our stock
price has ranged  from $9.75 to $29.50  over the last two  years.  In  addition,
sales of substantial  amounts of our common stock in the public market following
this  offering  could lower the market price of our common  stock.  In the past,
following  periods of  volatility  in the  market  price of a  company's  stock,
securities  class action  litigation has occurred  against the issuing  company.
Such  litigation   could  result  in  substantial   costs  and  a  diversion  of
management's attention and resources, which could have a material adverse effect
on our revenue and earnings.  Any adverse determination in such litigation could
also subject us to significant liabilities.


We may be liable if our products harm people.

         We face potential liability risks inherent in the testing and marketing
of medical  products.  We may be liable if any of our  products  causes  injury,
illness or death. We have obtained limited product  liability  insurance for our
human  clinical  trials.   However,  such  insurance  is  becoming  increasingly
expensive,  and we  cannot  predict  whether  we will be able to  maintain  such
insurance or obtain insurance covering injury,  illness or death from use of our
products that are  commercialized at a reasonable cost, if at all. Any insurance
we obtain may not provide adequate  coverage against  potential  liabilities.  A
liability  claim,  regardless  of merit or eventual  outcome,  could  materially
adversely affect our business, results of operation and financial condition.

Shares eligible for sale in the public market may affect the market price of our
common stock.

         Substantially  all of the shares of our common  stock are  eligible for
sale in the public  market.  The issuance of shares of our common stock upon the
exercise of stock  options and  warrants,  and the future sale of such shares by
current  stockholders,  could  adversely  affect the market  price of our common
stock. In March 1999, we issued:



         o        12% senior convertible notes which are convertible into common
                  stock

         o        warrants to purchase  12% senior  convertible  notes which are
                  convertible into common stock

         Conversion of the 12% senior convertible notes,  exercise of any common
stock warrants  issued upon  redemption of the 12% senior  convertible  notes or
warrants  to purchase  additional  12% senior  convertible  notes and payment of
interest  on the 12% senior  convertible  notes in shares of common  stock could
adversely affect the market price of our common stock.


                                       11
<PAGE>

                              SELLING STOCKHOLDERS



         The following table sets forth certain  information about the number of
shares  of  our  common  stock   beneficially  owned  by  each  of  the  selling
stockholders named below as of July 15, 1999 and on an as adjusted basis to give
effect to the sale of the shares offered by the selling stockholders. The shares
are being registered to permit public secondary  trading of the shares,  and the
selling  stockholders  may offer the shares for  resale  from time to time.  See
"Plan of Distribution."



         The shares  being  offered  hereby by the selling  stockholders  may be
acquired, from time to time upon:

         o        conversion of the Notes,


         o        conversion of the Warrant Notes, and


         o        exercise of the Common Stock  Warrants that may be issued upon
                  redemption of the Notes, Warrants and Warrant Notes.


         This prospectus covers the resale by the selling  stockholders of up to
2,461,943 shares of our common stock, plus an indeterminate number of additional
shares  of our  common  stock  as may from  time to time  become  issuable  upon
conversion of the Notes and Warrant Notes,  or upon exercise of the Common Stock
Warrants,  by  reason  of  stock  splits,  stock  dividends  and  other  similar
transactions. See "SUGEN-Recent Developments."


         In  accordance  with   registration   rights  granted  to  the  selling
stockholders,  SUGEN  has  filed  with the SEC,  under  the  Securities  Act,  a
Registration  Statement on Form S-3, of which this prospectus forms a part, with
respect  to the resale of the  shares  from time to time on the Nasdaq  National
Market,  in  privately-negotiated  transactions or otherwise,  and has agreed to
prepare and file such amendments and supplements to the  Registration  Statement
as may be  necessary to keep such  Registration  Statement  effective  until the
shares  are no longer  required  to be  registered  for the sale  thereof by the
selling stockholders.

<TABLE>

The shares of common stock covered by this  prospectus  may be offered from time
to time by the selling stockholders named below:

<CAPTION>
                                                                                                    Ownership After
                                                                                                       Offering(1)
                                                      Number of Shares         Number of
                 Names of Selling                      Owned Prior to        Shares Being         Number of
                   Stockholders                        Offering (1)(2)        Offered (3)          Shares      Percent
                   ------------                        ---------------        -----------          ------      -------

<S>                                                       <C>                 <C>                 <C>            <C>
Damson Investment Holdings, Ltd....................        42,796                43,963                --           0%

Delta Opportunity Fund (Institutional), LLC(4).....       231,272               237,577                --           0%

Delta Opportunity Fund, Ltd.(4)....................       799,033               626,302           189,352        1.11%

Fisher Capital Ltd(5)..............................       417,267               428,642                --           0%

Omicron Partners, LP...............................       831,641               780,350            72,000           *%

OTATO Limited Partnership(4).......................       148,610               114,303            37,340           *%

Wingate Capital, Ltd(5)............................       224,682               230,806                --           0%

<FN>
         * less than one percent

         (1)  Percentage  of  beneficial  ownership  is  calculated  assuming  16,976,672  shares of common  stock were
         outstanding  as of July 15, 1999.  Ownership  after this offering  assumes the sale of all shares held by such
         selling  stockholders  offered hereby.  Beneficial ownership is determined in accordance with the rules of the
         Securities  and  Exchange  Commission  and the  footnotes  to this table,  and  generally  includes  voting or
         dispositive  power with respect to securities.  Shares of common stock subject to options or warrants or other
         rights that are currently exercisable or convertible, or exercisable or convertible within 60 days of July 15,
         1999 are deemed  outstanding  for  computing  the  percentage  of the person or entity  holding such option or
         warrant but are not deemed  outstanding for computing the percentage of any other person or entity.  Except as
         indicated in the footnotes to this table and pursuant to applicable  community  property  laws, the persons or
         entities named in the table have sole voting and dispositive  power with respect to all shares of common stock
         beneficially owned.

         (2)  Represents  (i) the number of shares of common stock  issuable  upon  conversion of the Notes and Warrant
         Notes with respect to the face value of the Notes and Warrant Notes, and certain 12% Senior  Convertible Notes
         due 2001 (Exchange Notes) and 12% Senior  Convertible Note Purchase Warrants  (Exchange  Warrants) issued upon
         exchange of SUGEN's 5% Senior Custom Convertible Notes based upon certain conversion  provisions of the Notes,
         Warrant Notes,  Exchange Notes and Exchange Warrants,  (ii) the number of shares of common stock issuable upon
         exercise  of common  stock  warrants  issued in  September  1997,  (iii) the number of shares of common  stock
         issuable upon exercise of common stock warrants that may be issued upon redemption of the Notes,  Warrants and
         Warrant Notes,  (all or some of which would be issued in lieu of the same number of shares  referred to in the
         preceding clause (i)) and (iv) all other shares of common stock  beneficially  owned as of July 15, 1999.

         (3)  Represents  (i) the number of shares of common stock  issuable  upon  conversion of the Notes and Warrant
         Notes, based upon certain  conversion  provisions of the Notes and Warrant Notes and (ii) the number of shares
         of common stock issuable upon exercise of the common stock warrants that may be issued upon  redemption of the
         Notes,  Warrants and Warrant  Notes (all or some of which would be issued in lieu of the same number of shares
         referred to in the preceding clause (i)). The Notes and Warrant Notes provide that upon conversion, the number
         of shares  issuable is the quotient  obtained by dividing the  conversion  price into the sum of the principal
         amount converted plus accrued and unpaid interest on such principal to the date of conversion. For purposes of
         such formula,  the component for accrued and unpaid  interest will vary based on the date of  conversion.  The
         amount shown assumes the maximum  amount of such  component  would be equal to three months'  interest,  which
         would be the case if the Company does not default on any interest payment.



                                                           12
<PAGE>


         (4) Delta Opportunity Fund (Institutional), LLC, a Delaware limited liability company ("Delta Institutional"),
         Delta Opportunity Fund, Ltd., a British Virgin Islands corporation ("Delta"), and OTATO Limited Partnership, a
         Grand Cayman limited  partnership  ("OTATO"),  together with certain other persons,  have filed a Schedule 13G
         relating to their beneficial  ownership of common stock of SUGEN.  Based on the information  contained in such
         Schedule  13G,  such other  persons  beneficially  owned  shares of SUGEN  common stock as of July 15, 1999 as
         follows:  Diaz & Altschul Group, LLC, a New York limited liability company ("D&A Group"),  beneficially  owned
         1,142,465 shares constituting  approximately 6.3%, Diaz & Altschul Advisors, LLC, a New York limited liability
         company ("D&A  Advisors"),  beneficially  owned 1,072,465  shares  constituting  approximately  5.94%,  Diaz &
         Altschul  Management,  a Delaware limited liability  company ("D&A  Management"),  beneficially  owned 234,789
         shares  constituting  approximately  1.36%,  ACI/DA  Investors I, LLC, a Delaware  limited  liability  company
         ("ACI/DA"),  beneficially owned 25,200 shares constituting  approximately  0.01%, and Overbrook Fund I, LLC, a
         New York limited  liability  company  ("Overbrook")  beneficially  owned 3,000  shares.  Each of Delta,  Delta
         Institutional  and OTATO  disclaimed  beneficial  ownership of the shares of SUGEN  common  stock  reported as
         beneficially owned by such other persons in the Schedule 13G.

         D&A Advisors serves as investment  advisor to Delta and Delta  Institutional  and serves as trading advisor to
         ACI/DA and  Overbrook  with respect to the shares of common stock stated as  beneficially  owned by ACI/DA and
         Overbrook.  By reason of such  relationship,  D&A Advisors may be deemed to share  dispositive  power over the
         shares of Common  Stock  owned by Delta,  Delta  Institutional,  ACI/DA and  Overbrook.  The amount  stated as
         beneficially  owned by D&A  Advisors  includes  the  amounts  listed as  beneficially  owned by  Delta,  Delta
         Institutional,  ACI/DA and Overbrook.  D&A Advisors  disclaims  beneficial  ownership of such shares of common
         stock.

         D&A Management serves as investment manager to and managing member of Delta  Institutional.  By reason of such
         relationship,  D&A Management may be deemed to share  dispositive power over the shares of common stock listed
         as  beneficially  owned by Delta  Institutional.  The amount stated as  beneficially  owned by D&A  Management
         includes the amount stated as beneficially owned by Delta  Institutional.  D&A Management disclaims beneficial
         ownership of such shares of common stock.

         D&A Group is the parent company of D&A Advisors and D&A  Management.  By reason of its control of D&A Advisors
         and D&A Management,  D&A Group may be deemed to share dispositive power over the shares of common stock stated
         as beneficially owned by D&A Advisors and D&A Management. The amount listed as beneficially owned by D&A Group
         includes the amounts stated as  beneficially  owned by D&A Advisors and D&A  Management.  D&A Group  disclaims
         beneficial ownership of such shares of common stock.

         All shares of common stock listed as beneficially owned by the reporting persons are shares which such persons
         have the right to acquire upon conversion of the Notes,  the Warrant Notes,  the Exchange Notes and 12% Senior
         Convertible  Notes that may be issued upon  exercise of the  Exchange  Warrants  and upon  exercise of SUGEN's
         Common Stock Purchase Warrants ("Warrants").

         (5) Citadel Limited  Partnership is the managing general partner of NP Partners and the trading manager of each
         of Olympus  Securities,  Ltd.,  Fisher  Capital Ltd. and Wingate  Capital Ltd.  (the  "Citadel  Entities")  and
         consequently  has voting control and investment  discretion over securities held by the Citadel  Entities.  The
         ownership for each of Fisher Capital Ltd. and Wingate  Capital Ltd. does not include the ownership  information
         for the other  Citadel  Entities.  Citadel  Limited  Partnership  and each of the  Citadel  Entities  disclaims
         beneficial  ownership of the securities  held by the other Citadel  Entities.  As of July 15, 1999, NP Partners
         held Notes in the aggregate  principal amount of $2,191,009 plus accrued and unpaid interest  (convertible into
         107,377 shares of common stock), Warrant Notes to acquire $1,643,257 principal amount of Notes, and warrants to
         acquire 32,400 shares of common stock. As of July 15, 1999, Olympus Securities Ltd. held Notes in the aggregate
         principal  amount of $2,685,550  plus accrued and unpaid  interest  (convertible  into 131,613 shares of common
         stock), Warrant Notes to acquire $2,014,163 principal amount of Notes, and warrants to acquire 39,600 shares of
         common stock.

</FN>
</TABLE>



                                                           13
<PAGE>


                              PLAN OF DISTRIBUTION


         SUGEN will receive no proceeds from this offering.  We are  registering
the shares pursuant to registration rights granted to the selling  stockholders.
We will pay certain  expenses in connection with the  registration of the shares
and  will  indemnify  the  selling  stockholders  against  certain  liabilities,
including liabilities under the Securities Act.

         The shares offered hereby may be sold by the selling stockholders or by
pledgees,  donees, transferees or other successors in interest that receive such
shares as a gift,  partnership  distribution or other non-sale related transfer.
The shares may be sold from time to time in  transactions on the Nasdaq National
Market,  in  the  over-the-counter  market,  in  negotiated  transactions,  or a
combination  of such methods of sale,  at fixed prices which may be changed,  at
market prices  prevailing  at the time of sale, at prices  related to prevailing
market prices or at negotiated prices. The selling  stockholders may effect such
transactions by selling the shares to or through broker-dealers, including block
trades in which  brokers or dealers will attempt to sell the shares as agent but
may position and resell the block as principal to facilitate the transaction, or
in one or more underwritten offerings on a firm commitment or best effort basis.
Sales of  selling  stockholders'  shares may also be made  pursuant  to Rule 144
under the Securities Act, where applicable.


         To the extent required under the Securities  Act, the aggregate  amount
of selling stockholders' shares being offered and the terms of the offering, the
names of any such agents,  brokers,  dealers or underwriters  and any applicable
commission  with  respect  to a  particular  offer  will  be  set  forth  in  an
accompanying prospectus supplement. Any underwriters, dealers, brokers or agents
participating in the distribution of the shares may receive  compensation in the
form of underwriting discounts, concessions,  commissions or fees from a selling
stockholder and/or purchasers of selling stockholders' shares, for whom they may
act (which  compensation as to a particular  broker-dealer might be in excess of
customary commissions).

         From time to time, one or more of the selling  stockholders may pledge,
hypothecate  or grant a security  interest in some or all of the shares owned by
them, and the pledgees,  secured parties or persons to whom such securities have
been hypothecated  shall, upon foreclosure in the event of default, be deemed to
be selling stockholders  hereunder. In addition, a selling stockholder may, from
time to time, sell short the common stock of SUGEN, and in such instances,  this
prospectus  may be delivered in connection  with such short sales and the shares
offered hereby may be used to cover such short sales.

         From time to time one or more of the selling stockholders may transfer,
pledge,  donate or assign such selling stockholders' shares to lenders or others
and each of such  persons  will be  deemed  to be a  "selling  stockholder"  for
purposes  of  this  prospectus.  The  number  of  selling  stockholders'  shares
beneficially owned by those selling stockholders who so transfer, pledge, donate
or assign selling  stockholders' shares will decrease as and when they take such
actions.  The  plan  of  distribution  for  selling  stockholders'  shares  sold
hereunder  will  otherwise  remain  unchanged,   except  that  the  transferees,
pledgees, donees or other successors will be selling stockholders hereunder.

         A  selling  stockholder  may  enter  into  hedging   transactions  with
broker-dealers  and the  broker-dealers  may engage in short sales of the common
stock in the course of hedging  the  positions  they  assume  with such  selling
stockholder,  including, without limitation, in connection with distributions of
the common stock by such  broker-dealers.  A selling  stockholder may also enter
into option or other transactions with  broker-dealers that involve the delivery
of the common  stock to the  broker-dealers,  who may then  resell or  otherwise
transfer such common stock.  A selling  stockholder  may also loan or pledge the
common stock to a broker-dealer  and the broker-dealer may sell the common stock
so loaned or upon a default may sell or otherwise  transfer  the pledged  common
stock.

         In order to comply  with the  securities  laws of  certain  states,  if
applicable,  the  shares  will  be  sold  in  such  jurisdictions  only  through
registered or licensed  brokers or dealers.  In addition,  in certain states the
shares may not be sold unless they have been registered or qualified for sale in
the applicable  state or an exemption  from the  registration  or  qualification
requirement is available and is complied with.

         The  selling   stockholders  and  any  broker-dealers  or  agents  that
participate with the selling  stockholders in the distribution of the shares may
be deemed to be "underwriters" within the meaning of the Securities Act, and any
commissions  received  by them  and  any  profit  on the  resale  of the  shares
purchased  by them may be deemed to be  underwriting  commissions  or  discounts
under the Securities Act.

         Under  applicable  rules and  regulations  under the Exchange  Act, any
person  engaged in the  distribution  of the shares may not bid for or  purchase
shares of common  stock  during a period  which  commences  one  business day (5
business  days, if SUGEN's  public float is less than $25 million or its average
daily trading volume is less than $100,000) prior to such person's participation
in the  distribution,  subject to exceptions  for certain  passive market making
activities.  In addition  and  without  limiting  the  foregoing,  each  selling
stockholder will be subject to applicable provisions of the Exchange Act and the
rules and regulations thereunder,  including,  without limitation,  Regulation M
which  provisions  may limit  the  timing  of  purchases  and sales of shares of
SUGEN's common stock by such selling stockholder.

         The shares were originally issued to the selling stockholders  pursuant
to an  exemption  from  the  registration  requirements  of the  Securities  Act
provided by Section 4(2) thereof.  SUGEN agreed to register the shares under the
Securities  Act and to  indemnify  and hold the  selling  stockholders  harmless
against  certain  liabilities  under  the  Securities  Act that  could  arise in
connection with the sale by the selling  stockholders  of the shares.  SUGEN has
agreed to pay all  reasonable  fees and expenses  incident to the filing of this
registration statement.

                                  LEGAL MATTERS

         The legality of the  securities  offered hereby will be passed upon for
SUGEN by Cooley Godward LLP, Palo Alto, California.

                                     EXPERTS

         The financial statements of SUGEN appearing in SUGEN's Annual Report on
Form 10-K for the year  ended  December  31,  1998 have been  audited by Ernst &
Young LLP, independent  auditors,  as set forth in their report thereon included
therein and  incorporated  herein by reference.  Such



                                       14
<PAGE>


financial  statements are incorporated herein by reference in reliance upon such
report  given  upon the  authority  of such firm as experts  in  accounting  and
auditing.


                       WHERE YOU CAN FIND MORE INFORMATION

         We file  reports,  proxy  statements  and  other  information  with the
Securities and Exchange  Commission.  You may read and copy any document we file
at the SEC's Public Reference Room at Judiciary  Plaza, 450 Fifth Street,  N.W.,
Room 1024,  Washington,  D.C. 20549 and at the following regional offices of the
SEC: Pacific Regional Office, 5670 Wilshire Boulevard,  11th Floor, Los Angeles,
California 90036-3648;  and San Francisco District Office, 44 Montgomery Street,
Suite 1100, San Francisco,  California  94104.  Copies can also be obtained from
the Public Reference Room of the SEC at 450 Fifth Street, N.W., Washington, D.C.
20549,  upon payment of  prescribed  rates.  You may obtain  information  on the
operation  of the  SEC's  Public  Reference  Room by  calling  the SEC at  (800)
SEC-0300.  Our SEC filings are  available to you on the SEC's  Internet  site at
http://www.sec.gov.  Our common stock is quoted on The Nasdaq  National  Market.
Reports,  proxy statements and other information  concerning us may be inspected
at the National Association of Securities Dealers,  Inc. at 1735 K Street, N.W.,
Washington, D.C. 20006.

         This  prospectus is only part of a  registration  statement on Form S-3
that we have filed with the SEC under the  Securities  Act, and therefore  omits
certain information contained in the registration  statement. We have also filed
exhibits and schedules with the registration  statement that are not included in
this prospectus,  and you should refer to the applicable exhibit or schedule for
a complete  description  of any  statement  referring  to any  contract or other
document.  A copy of the  registration  statement,  including  the  exhibits and
schedules thereto,  may be inspected without charge at the Public Reference Room
of the SEC  described  above,  and copies of such  material may be obtained from
such office upon payment of the fees prescribed by the SEC.

         The  SEC  allows  us to  "incorporate  by  reference"  the  information
contained in documents that we file with them,  which means that we can disclose
important  information  to  you  by  referring  you  to  these  documents.   The
information  incorporated  by  reference  is  considered  to  be  part  of  this
prospectus and later information we file with the SEC will automatically  update
and supercede this information. We incorporate by reference the documents listed
below and any future filings made with the SEC under Sections  13(a),  13(c), 14
or 15(d) of the Exchange  Act. The documents we are  incorporating  by reference
are:


1.       Our Annual Report on Form 10-K for the year ended December 31, 1998, as
         amended (File No. 0-24814);


2.       Our Quarterly Report on Form 10-Q for the quarter ended March 31, 1999,
         as amended (File No. 0-24814);

3.       Our  Definitive   Proxy  Statement  dated  April  22,  1999,  filed  in
         connection  with our 1999  Annual  Meeting  of  Stockholders  (File No.
         0-24814);

4.       Our  Current  Report  on Form 8-K  filed on March  29,  1999  (File No.
         0-24814);

5.       Our  Current  Report  on Form  8-K  filed on June 21,  1999  (File  No.
         0-24814); and

6.       The  description  of our common  stock  contained  in our  Registration
         Statement  on Form 8-A  filed on  September  13,  1994,  including  any
         amendments   or  reports   filed  for  the  purpose  of  updating  such
         description (File No. 0-24814).

         You may request a copy of any of these filings at no cost by writing or
telephoning us at:

                                   SUGEN, Inc.
                              230 East Grand Avenue
                      South San Francisco, California 94080
              Attn: Corporate Communications and Investor Relations
                            Telephone (650) 553-8300



                                       15
<PAGE>

NO  DEALER,  SALESPERSON  OR  OTHER  PERSON  HAS  BEEN  AUTHORIZED  TO GIVE  ANY
INFORMATION OR TO MAKE ANY  REPRESENTATIONS  OTHER THAN THOSE  CONTAINED IN THIS
PROSPECTUS AND, IF GIVEN OR MADE, SUCH INFORMATION OR  REPRESENTATIONS  MUST NOT
BE RELIED UPON AS HAVING BEEN  AUTHORIZED BY THE COMPANY.  THIS  PROSPECTUS DOES
NOT  CONSTITUTE  AN  OFFER TO SELL OR A  SOLICITATION  OF AN OFFER TO BUY TO ANY
PERSON IN ANY JURISDICTION IN WHICH SUCH OFFER OR SOLICITATION WOULD BE UNLAWFUL
OR TO ANY PERSON TO WHOM IT IS UNLAWFUL. NEITHER THE DELIVERY OF THIS PROSPECTUS
NOR ANY OFFER OR SALE MADE HEREUNDER SHALL, UNDER ANY CIRCUMSTANCES,  CREATE ANY
IMPLICATION  THAT THERE HAS BEEN NO CHANGE IN THE AFFAIRS OF THE COMPANY OR THAT
THE  INFORMATION  CONTAINED  HEREIN IS CORRECT AS OF ANY TIME  SUBSEQUENT TO THE
DATE HEREOF.


                        2,461,943 Shares of Common Stock


                                   SUGEN, Inc.

                                   PROSPECTUS



                                  AUGUST 2, 1999




                                       16


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