CELGENE CORP /DE/
S-3, 1999-12-29
COMMERCIAL PHYSICAL & BIOLOGICAL RESEARCH
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                                                                Registration No.

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


                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
     -----------------------------------------------------------------------


                                    FORM S-3
                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933
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                               CELGENE CORPORATION
             (Exact name of Registrant as specified in its charter)
     -----------------------------------------------------------------------



     DELAWARE                               8731                 22-2711928
(State or other jurisdiction of (Primary Standard Industrial  (I.R.S. Employer
incorporation or organization)  Classification Code Number)  Identification No.)

                  7 Powder Horn Drive, Warren, New Jersey 07059
                                 (732) 271-1001
               (Address, including zip code, and telephone number,
        including area code, of Registrant's principal executive offices)
     -----------------------------------------------------------------------


                                 JOHN W. JACKSON
                Chairman of the Board and Chief Executive Officer
                               Celgene Corporation
                  7 Powder Horn Drive, Warren, New Jersey 07059
                                 (732) 271-1001
            (Name, address, including zip code, and telephone number,
                   including area code, of agent for service)
     -----------------------------------------------------------------------

                          Copies of Communications to:
                             Robert A. Cantone, Esq.
                               Proskauer Rose LLP
                  1585 Broadway, New York, New York 10036-8299
                                 (212) 969-3000
     -----------------------------------------------------------------------

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

     If the only  securities  being  registered  on this Form are being  offered
pursuant to dividend or interest  investment  plans,  please check the following
box. |_|

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

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

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

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

                         CALCULATION OF REGISTRATION FEE

<TABLE>
<S>                           <C>           <C>                  <C>                     <C>
                                            Proposed Maximum     Proposed Maximum        Amount of
Title of each class of        Amount to be   Offering Price          Aggregate         registration
Securities To Be Registered   registered      Per Share (1)        Offering Price         fee

Common Stock,                1,707,850 shares   $66.5625         $113,678,765.63       $30,011.19
par value $.01 per share
</TABLE>

1.   Based on the  average  high and low  trading  price on the Nasdaq  National
     Market on  December  23,  1999.  Estimated  pursuant  to Rule 457 under the
     Securities  Act of 1933, as amended,  solely for the purpose of calculating
     the registration fee.
     -----------------------------------------------------------------------

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

<PAGE>

Information   contained  herein  is  subject  to  completion  or  amendment.   A
registration  statement  relating  to these  securities  has been filed with the
Securities  and Exchange  Commission.  These  securities may not be sold nor may
offers to buy be accepted prior to the time the registration  statement  becomes
effective.  This  prospectus  shall  not  constitute  an  offer  to  sell or the
solicitation of an offer to buy nor shall there be any sale of these  securities
in any State in which such offer,  solicitation  or sale would be unlawful prior
to registration or qualification under the securities laws of any such State.

                               CELGENE CORPORATION

                                1,707,850 SHARES

                                  COMMON STOCK
                           (PAR VALUE $0.01 PER SHARE)


These shares of common stock are being sold by the selling  stockholders  listed
beginning on page 11. Celgene Corporation  ("Celgene" or the "Company") will not
receive any proceeds from the sale of these shares.

Celgene's  common stock is traded on the Nasdaq National Market under the symbol
"CELG." The last reported sale price on December 27, 1999 was $67.875 per share.

The common stock may be sold in  transactions  in the Nasdaq  National Market at
market prices then  prevailing,  in negotiated  transactions  or otherwise.  See
"Plan of Distribution."

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

                     This offering involves material risks.
                     See "Risk Factors" beginning on page 4.

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

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

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


                   The date of this Prospectus is December 28, 1999.



                                        1

<PAGE>
                               PROSPECTUS SUMMARY


     You should  read the  following  summary  together  with the more  detailed
information,  including the consolidated  financial  statements and the notes to
the financial  statements and other information,  incorporated by reference into
this prospectus.

                                   THE COMPANY

     We  are  an  independent   biopharmaceutical   company  that  develops  and
commercializes pharmaceutical products for human beings, focusing largely on the
immunology/oncology  market and agrochemicals for crops. The initial therapeutic
focus of our  immunology/oncology  program  is the  development  of:  (i)  small
molecule  pharmaceuticals  that have the potential to selectively regulate Tumor
Necrosis Factor ("TNF"), a protein whose  overproduction has been linked to many
chronic  inflammatory  and  immunological  diseases and (ii) the  development of
anti-angiogenic pharmaceuticals that can inhibit the growth of new blood vessels
in a growing tumor,  making them potentially  valuable  anti-cancer  agents. Our
lead pharmaceutical is THALOMID(R),  our formulation of thalidomide,  which is a
down-regulator of TNF and an anti- angiogenic agent.

     On July  16,  1998,  we  received  approval  from  the  U.S.  Food and Drug
Administration  (the "FDA") for THALOMID for the  treatment of erythema  nodosum
leprosum ("ENL"),  an inflammatory  complication of leprosy.  We are in clinical
development  of THALOMID with the objective of  submitting  additional  New Drug
Applications  ("NDAs")  to allow us to  market  THALOMID  for the  treatment  of
certain  cancers and  conditions  in patients with  Acquired  Immune  Deficiency
Syndrome ("AIDS").

     Working with the FDA, we have developed a comprehensive  education  program
and distribution  system, the "System for Thalidomide  Education and Prescribing
Safety," or the  S.T.E.P.S.(TM)  program,  which is designed to support the safe
and appropriate use of thalidomide because of the drug's capacity to cause birth
defects.  This program has been made a part of the THALOMID  label.  We are also
developing  novel  and  proprietary  thalidomide  analogues,   called  IMiDs(TM)
(Immunomodulatory  Drugs),  as well as a class of proprietary  immunotherapeutic
pharmaceutical  compounds called  SelCIDs(TM)  ("Selective  Cytokine  Inhibitory
Drugs").  These two classes of compounds are orally administered small molecules
that suppress excess TNF  production,  have  anti-angiogenic  properties and are
intended to treat chronic inflammatory diseases, cancer and other disorders.

     Our  chiral  technology  is  based  on  biocatalysis,  which  involves  the
identification  and  manipulation  of enzymes to  perform  specialized  chemical
reactions,  such as the production of chirally pure compounds.  Chirality refers
to the property of many  chemical  compounds  to exist in two or more  different
conformations  that are mirror images of each other.  While one conformation may
have  beneficial  effects,  the other may be  inactive  or  produce  undesirable
effects.  Chirally pure compounds contain only one of these  conformations,  and
thus may have attributes superior to those of the racemic mixture.

     We are developing chirally pure versions of commercialized  pharmaceuticals
to develop  products  having  greater  efficacy  and fewer side effects than the
existing  racemic  versions.  Our main  product  is a chirally  pure  version of
dl-methylphenidate  (currently marketed under the trade name Ritalin(R)) for the
treatment of Attention Deficit  Hyperactivity  Disorder ("ADHD"). We completed a
Phase III efficacy  pivotal  trial program in the third quarter of 1999 in which
our chirally pure version demonstrated statistically significant efficacy versus
placebo and longer  duration of action relative to the racemic  version.  A long
term safety trial is expected to be completed  during the first quarter of 2000.
We previously


                                        2

<PAGE>



completed a Phase I/II trial and  announced  that our chirally  pure version had
demonstrated   statistically   significant   efficacy  versus  the  placebo  and
preliminary  indications  of longer  duration of action  relative to the racemic
version.

     We are  working  to produce an array of novel,  highly  potent,  selective,
safe,  orally  administered  drugs  that  have the  potential  to  regulate  the
overproduction of TNF, as well as inhibiting angiogenesis. Overproduction of TNF
has been implicated in symptoms  associated  with certain  chronic  inflammatory
diseases.  Chronic inflammatory and immunological  diseases collectively afflict
millions  of  patients,  and for the most  part are  inadequately  treated  with
existing  therapies.  We are developing two new classes of compounds,  IMiDs and
SelCIDs,  which have been demonstrated in in vitro tests using human cells to be
significantly more active than thalidomide in suppressing TNF production and, in
preclinical tests, have not demonstrated  teratogenicity.  Initially,  the IMiDs
and the SelCIDs are targeted  for use in treating  inflammatory  bowel  disease,
rheumatoid arthritis and oncological applications. Our first SelCID was found to
be well tolerated in two Phase I clinical trials in the United  Kingdom,  and is
in a pilot  study in the United  States to assess  its  potential  for  treating
Crohn's  disease.  The IMiDs have entered a Phase Ia clinical  program to assess
safety and  tolerability.  The United States Patent and Trademark  Office ("U.S.
PTO") has issued  composition  of matter  patents to us  relating  to certain of
these novel IMiDs and SelCIDs.

     Through  our  Celgro(TM)  subsidiary,  we  are  also  applying  our  chiral
technology  to the  production  of  chirally  pure  agrochemicals,  in which the
Company's  biocatalytic  process  can add  significant  value  by  substantially
lowering  manufacturing  costs and  reducing  environmental  impact.  Celgro has
entered  into  agreements  with two leading  agrochemical  companies  to develop
cost-effective processes for the production of chirally pure versions of certain
products  currently  produced by those firms.  Each agreement  provides that the
customer will fund a research and development  program  conducted by us relating
to the customer's  product,  make milestone payments to us if certain benchmarks
are achieved and pay us a royalty if the program leads to commercial sales.

     We have  established a sales and marketing  organization  to  commercialize
THALOMID  and employ  approximately  60 persons in this  capacity.  We intend to
develop and market our own  pharmaceuticals for indications with smaller patient
populations.  We anticipate partnering with larger pharmaceutical companies with
respect to drugs for indications with larger patient populations.  We may create
partnerships  with companies for the  development and  commercialization  of our
chirally pure  pharmaceuticals and agrochemical  products.  We expect that these
arrangements  typically  will  include  milestone  payments,   reimbursement  of
research and development expenses and royalty arrangements.

     We were  incorporated in Delaware in 1986. Our principal  executive offices
are located at 7 Powder Horn Drive,  Warren, New Jersey 07059, and our telephone
and fax numbers are (732) 271-1001 and (732) 805-3931, respectively.





                                        3

<PAGE>
                                  RISK FACTORS


We are  dependent on product  development  and  commercialization  for continued
growth and development.

     Many of our  products  and  processes  are in the  early or  mid-stages  of
development and will require the commitment of substantial resources,  extensive
research,  development,  preclinical  testing,  clinical  trials,  manufacturing
scale-up, and regulatory approval prior to being ready for sale. We have not yet
sold any of our products other than THALOMID. All of the pharmaceutical products
under  development  will require  further  development,  clinical  testing,  and
regulatory  approvals,  and there can be no assurance that  commercially  viable
products will result from these  efforts.  If any of our  products,  if and when
developed and approved,  cannot be  successfully  commercialized,  our operating
results could be materially adversely affected.

     The pharmaceutical  industry is subject to extensive government  regulation
and there is no assurance of regulatory approval.

     The preclinical development, clinical trials, manufacturing, marketing, and
labeling of pharmaceuticals are all subject to extensive  regulation by numerous
governmental  authorities and agencies in the United States and other countries.
There can be no assurance that we will be able to obtain the necessary approvals
required to market our products in any of these markets. The testing, marketing,
and manufacturing of our products will require  regulatory  approval,  including
approval  from the FDA,  and,  in  certain  cases,  from the U.S.  Environmental
Protection Agency (the "EPA"), or governmental authorities outside of the United
States  that  perform  roles  similar  to those  of the FDA and  EPA.  It is not
possible to predict how long the approval processes for any of our products will
take or whether any such approvals ultimately will be granted.  Positive results
in preclinical  testing and/or early phases of clinical studies are no assurance
of success in later phases of the approval  process.  Risks associated with this
process include:

     o    In general, preclinical tests and clinical trials can take many years,
          and require the  expenditure  of substantial  resources,  and the data
          obtained  from these  tests and trials can be  susceptible  to varying
          interpretation   that  could  delay,   limit,  or  prevent  regulatory
          approval.

     o    Delays  or  rejections  may be  encountered  during  any  stage of the
          regulatory  approval process based upon the failure of the clinical or
          other data to demonstrate  compliance with, or upon the failure of the
          product to meet,  the  regulatory  agency's  requirements  for safety,
          efficacy,  and quality or, in the case of a product  seeking an orphan
          drug  indication,  because another designee  received  approval first.
          Further,  those  requirements may become more stringent due to changes
          in regulatory agency policy, or the adoption of new regulations.

     o    Clinical trials may also be delayed due to unanticipated side effects,
          the  inability to locate,  recruit and qualify  sufficient  numbers of
          patients,  lack  of  funding,  the  inability  to  locate  or  recruit
          scientists,  the redesign of clinical trial programs, the inability to
          manufacture or acquire sufficient quantities of the particular product
          candidate  or any  other  components  required  for  clinical  trials,
          changes  in  focus of the  Company's  or our  collaborative  partner's
          development focus, and the disclosure of trial results by competitors.

     o    The scope of any regulatory approval, when obtained, may significantly
          limit the indicated uses for which a product may be marketed.



                                        4

<PAGE>

     o    Approved drugs and agrochemicals, as well as their manufacturers,  are
          subject to  on-going  review,  and  discovery  of  previously  unknown
          problems  with  these  products  may result in  restrictions  on their
          manufacture, sale or use or in their withdrawal from the market.

Delays in obtaining, or the failure to obtain and maintain,  necessary approvals
from the FDA, EPA, or other  regulatory  agencies for our proprietary  products,
would have a material adverse effect on our business,  financial condition,  and
results of operations.

There is no assurance of market acceptance of our products.

     There  can be no  assurance  that  those  of  our  products  which  receive
regulatory approval,  including THALOMID, or for which no regulatory approval is
required, will achieve market acceptance.  A number of factors render the degree
of market acceptance of our products uncertain, including the extent to which we
can demonstrate such products'  efficacy,  safety, and advantages over competing
products,  as well as the reimbursement  policies of third party payors, such as
government and private  insurance plans. In addition,  there can be no assurance
that our Celgro  subsidiary will be able to negotiate a new licensing  agreement
with any  agrochemical  manufacturer on terms acceptable to us, or at all, or to
reach the  commercialization  stage of the existing  agreements.  Failure of our
products to achieve market  acceptance  would have a material  adverse effect on
our business, financial condition, and results of operations.

We are  subject  to  product  liability  risk  and may  not be  able  to  obtain
insurance.

     We may be subject to product liability or other claims based on allegations
that the use of our  technology  or products  has  resulted in adverse  effects,
whether by participants in our clinical trials or by patients. Thalidomide, when
used by pregnant  women,  has  resulted  in serious  birth  defects.  Therefore,
necessary and strict  precautions  must be taken by physicians  prescribing  the
drug to women with  childbearing  potential,  and there can be no assurance that
such  precautions  will be  observed  in all  cases  or,  if  observed,  will be
effective.  Use of thalidomide has also been associated,  in a limited number of
cases, with other side effects, including nerve damage. Although we have product
liability  insurance  in force that we believe is  appropriate,  there can be no
assurance  that we will be able to obtain  additional  coverage as required,  or
that such  coverage  will be  adequate  to  protect  us in the event  claims are
asserted  against  us.  Our  obligation  to defend  against  or pay any  product
liability  claim may have a material  adverse effect on our business,  financial
condition, and results of operations.

     We may not be able to obtain  patent  coverage  or  otherwise  protect  our
proprietary technology.

     Our  success  will  depend,  in part,  on our ability to obtain and enforce
patents,  protect trade secrets,  obtain  licenses to technology  owned by third
parties  when  necessary,  and  conduct  our  business  without  infringing  the
proprietary  rights of  others.  The  patent  positions  of  pharmaceutical  and
biotechnology  firms,  including us, can be uncertain and involve  complex legal
and factual questions.  In addition, the coverage sought in a patent application
can be significantly  reduced before the patent is issued.  Consequently,  we do
not know whether any of our pending  applications will result in the issuance of
patents or, if any patents are issued,  whether  they will  provide  significant
proprietary  protection  or commercial  advantage,  or will be  circumvented  by
others. We rely upon unpatented  proprietary and trade secret technology that we
try to protect,  in part, by  confidentiality  agreements with our collaborative
partners, employees,  consultants,  outside scientific collaborators,  sponsored
researchers, and other advisors. There can be no assurance that these agreements
provide meaningful  protection or that they will not be breached,  that we would
have  adequate  remedies  for any  such  breach,  or  that  our  trade  secrets,
proprietary know-how, and technological advances will not otherwise become known
to others. In addition, there can be no assurance


                                        5
<PAGE>

that, despite precautions taken by us, others have not and will not obtain
access to our proprietary technology.

We have a history of operating losses, an accumulated deficit and will likely
need to seek additional funding.

     We have sustained  losses in each year since our  incorporation in 1986. We
sustained  a net loss of  approximately  $25.1 and $25.4  million  for the years
ended December 31, 1998 and 1997,  respectively,  and $18.9 million for the nine
months ended September 30, 1999 and had an accumulated  deficit of approximately
$144.6 million at December 31, 1998 and $163.5 million at September 30, 1999. We
expect to make substantial expenditures to further develop our immunotherapeutic
and chiral  products,  and,  based on these  expenditures,  it is probable  that
losses will continue for at least the next 9 months. We are currently utilizing
our cash resources at a rate of approximately  $1.5 million per month. We expect
that our rate of spending  generally will remain high as the result of increased
clinical  trial  costs and  expenses  associated  with the  regulatory  approval
process and commercialization of products now in development. In order to assure
funding  for our future  operations,  we will  likely  seek  additional  capital
resources. There can be no assurance,  assuming we successfully raise additional
funds or enter into a business alliance,  that we will achieve  profitability or
positive cash flow. The cash and marketable securities position at September 30,
1999 was approximately $18.6 million.

The  pharmaceutical   industry  is  highly  competitive  and  subject  to  rapid
technological change.

     The  pharmaceutical  and  agrochemical  businesses  in which we operate are
highly competitive and subject to rapid and profound  technological  change. Our
present and  potential  competitors  include major  chemical and  pharmaceutical
companies,  as well as specialized  biotechnology firms in the United States and
in other countries. Most of these companies have considerably greater financial,
technical,  and marketing resources than we have. We also experience competition
from  universities and other research  institutions  and, in some instances,  we
compete   with  others  in  acquiring   technology   from  such   sources.   The
pharmaceutical and agrochemical  industries have undergone,  and are expected to
continue to undergo,  rapid and significant  technological change, and we expect
competition to intensify as technical advances in each field are made and become
more  widely  known.  There can be no  assurance  that  others  will not develop
products or processes with significant advantages over those that we are seeking
to develop.  Any such  development  could have a material  adverse effect on our
business, financial condition, and results of operations.

We are  dependent on one supplier  for the raw  material  and  encapsulation  of
THALOMID.

     We obtain all of our bulk drug material for THALOMID from a single  source.
In addition, we currently rely on a single manufacturer to encapsulate THALOMID.
Because the FDA requires that all suppliers of pharmaceutical  bulk material and
all manufacturers of  pharmaceuticals  for sale in the United States achieve and
maintain   compliance  with  the  FDA's  current  Good  Manufacturing   Practice
regulations  and guidelines  ("GMP"),  if the operations of the sole supplier or
the sole  encapsulator were to become  unavailable for any reason,  the required
FDA review of the operations of a new supplier or new encapsulator could cause a
delay in the manufacture of THALOMID. Such a delay could have a material adverse
effect on our business, financial condition, and results of operations.



                                        6

<PAGE>

We are dependent on collaborations and licenses with third parties.

     Our ability to fully commercialize our proprietary  products, if developed,
may depend to some extent upon our ability to enter into joint ventures or other
arrangements  with  established  pharmaceutical  companies  with  the  requisite
experience and financial and other resources to obtain regulatory approval,  and
to manufacture and market such products.  Accordingly,  our success will depend,
in part,  upon the  subsequent  success  of such  third  parties  in  performing
preclinical  testing and clinical  trials,  obtaining the  requisite  regulatory
approvals,  scaling up manufacturing,  successfully commercializing the licensed
product candidates and otherwise  performing their obligations.  There can be no
assurance  that  we will be able to  enter  into  acceptable  collaborative  and
licensing  arrangements on acceptable  terms, if at all, that such  arrangements
will be  successful,  that the parties with which we may establish  arrangements
will perform their obligations, or that potential collaborators will not compete
with us by seeking alternative means of developing therapeutics for the diseases
targeted  by  us.  There  can  be no  assurance  that  our  existing  or  future
arrangements  will lead to the  development  of product  candidates or compounds
with  commercial  potential,  that  we  will  be  able  to  obtain  or  maintain
proprietary  rights or licenses for the  proprietary  rights with respect to any
technology or product candidates or compounds developed in connection with these
arrangements,  or that we will be  able to  ensure  the  confidentiality  of any
proprietary rights and information developed in such arrangements or prevent the
public disclosure thereof.

We have no manufacturing capabilities.

     The  manufacture  of  large  quantities  of  pharmaceuticals  is a  complex
process,  and all  pharmaceutical  manufacturing  facilities  must  comply  with
applicable  regulations  of the FDA. We currently  have no experience in, or our
own  facilities  for,  manufacturing  any  products on a  commercial  scale.  We
currently  obtain bulk drug material for THALOMID from a third-party and utilize
another  manufacturer  to produce  dosage  form  THALOMID.  We intend to utilize
outside  manufacturers  if and when  needed to produce  our other  products on a
commercial scale.  There can be no assurance that such  manufacturers  will meet
our  requirements  for  quality,   quantity,   or  timeliness,   or  that  these
manufacturers   will  achieve  and  maintain   compliance  with  all  applicable
regulations.

We have limited marketing capabilities.

     We have a sales and marketing  organization to commercialize  THALOMID, and
with  respect to certain  other  products,  we may seek a  corporate  partner to
provide  such  services.  Any delay in  developing  these  resources  may have a
material  adverse impact on potential sales. We have contracted with a specialty
distributor to distribute  THALOMID.  Failure of such  specialty  distributor to
properly and  continuously  perform its  obligations  under such agreement could
have a material adverse effect on our business.

Product pricing is uncertain and we are dependent on third-party reimbursement.

     Sales of our pharmaceutical products will depend, in part, on the extent to
which the costs of such  products  will be paid by health  maintenance,  managed
care,  pharmacy  benefit and similar health care  management  organizations,  or
reimbursed by  government  health  administration  authorities,  private  health
coverage  insurers,  and other third party payors.  These health care management
organizations  and third party payors are  increasingly  challenging  the prices
charged for medical  products and services.  Additionally,  the  containment  of
health care costs has become a priority,  and the prices of  pharmaceutical  and
biotechnology drugs have been targeted in this effort. There can be no assurance
that  our  products  will  be  considered   cost   effective  by  payors,   that
reimbursement   will  be  available  or,  if   available,   that  the  level  of
reimbursement  will  be  sufficient  to  allow  us to  sell  our  products  on a
profitable basis.


                                        7

<PAGE>

We are dependent on key personnel for our continued growth and development.

     Our  success  will  depend,  in large  part,  on our ability to continue to
attract  and  retain  highly  skilled   scientific  and  management   personnel.
Competition for such personnel is intense, and there can be no assurance that we
will be able to  attract  and retain  such  persons.  The loss of our  executive
officers or  scientific  personnel,  or our failure to attract and retain  other
highly skilled  personnel would have a material  adverse effect on our business,
financial condition, and results of operations.  We do not maintain key man life
insurance coverage on the lives of any of our officers or key employees.

Environmental and safety hazards are a risk.

     We  use  certain  hazardous  materials  in  our  research  and  development
activities. While we believe we are currently in substantial compliance with the
federal,  state, and local laws and regulations governing such use, there can be
no assurance that accidental  injury or  contamination  will not occur. Any such
accident or contamination could result in substantial  liabilities,  which could
exceed our resources.  Additionally,  there can be no assurance that the cost of
compliance  with  environmental  and  safety  laws and  regulations  will not be
greater than currently expected.

The number of shares of common stock  eligible  for future sale could  adversely
affect the market price of our common stock.

     Future sales of substantial  amounts of common stock could adversely affect
the prevailing  market price of our common stock. As of December 15, 1999, there
were  outstanding  stock options for  approximately  2,409,691  shares of common
stock, of which approximately 1,081,048 were currently exercisable, and warrants
either  outstanding  or issuable  upon demand that are  exercisable  for 557,444
shares of common  stock.  In  addition,  the 9.25%  convertible  note  issued on
September 16, 1998 can be converted to 795,455  shares of common  stock,  the 9%
convertible  notes issued on January 20, 1999 can be converted in the  aggregate
to 833,400 shares of common stock and the 9% convertible notes issued on July 6,
1999 can be converted in the aggregate into 789,450 shares of common stock.  All
shares of common stock  referred to in this paragraph  would be freely  tradable
upon issuance.

We may experience fluctuations in our quarterly operating results.

     We  have  historically   experienced,   and  expect  to  continue  for  the
foreseeable  future to  experience,  significant  fluctuations  in our quarterly
operating results. This fluctuation is due to a number of factors, many of which
are outside our control, including the timing of receipt of certain research and
development  payments.  Future  operating  results will depend on many  factors,
including  demand  for our  products,  regulatory  approvals,  the timing of the
introduction and market acceptance of new products by us or competing companies,
our  ability to control  costs and our  ability  to  attract  and retain  highly
qualified scientific and management  personnel.  Such quarterly  fluctuations in
operating results may result in volatility of our stock price.

Our stock price has experienced substantial volatility.

     There has been  significant  volatility  in the market  prices for publicly
traded shares of biopharmaceuticals  companies,  including ours. There can be no
assurance  that the price of our common  stock will remain at or exceed  current
levels. Factors such as announcements of technical or product developments by us
or our competitors,  market  conditions for specialty  pharmaceutical  stocks in
general,


                                        8

<PAGE>

governmental regulation,  healthcare legislation, public announcements regarding
medical  advances in the treatment of the disease  states that we are targeting,
or patent or  proprietary  rights  developments  may have a significant  adverse
impact on the market price of our common stock.

Our  shareholder  rights plan and  certain  charter  and by-law  provisions  may
dissuade a potential acquiror.

     Our board of directors has adopted a  shareholder  rights plan (the "Rights
Plan"),  the  purpose of which is to protect  stockholders  against  unsolicited
attempts  to acquire  control of us that do not offer a fair price to all of our
stockholders.  The  Rights  Plan is not  intended  to  prevent,  and  should not
prevent,  an offer to  acquire  Celgene  at a price and on terms that are in the
best interests of all stockholders,  or a negotiated transaction to sell Celgene
for a  purchase  price  determined  by  our  board  of  directors  to be in  our
stockholders'  best interests,  nor should it have a material  adverse effect on
the ability of a person or group to obtain  representation  on or control of the
board of directors  through a proxy  contest.  Nonetheless,  the Rights Plan may
have the effect of dissuading a potential  acquirer from making an offer for all
the  outstanding  shares of Common Stock at a price that represents a premium to
the then current trading price.

     Moreover,  our board of directors has the authority to issue,  at any time,
without further stockholder approval, up to 5,000,000 shares of preferred stock,
and to determine the price, rights, privileges, and preferences of those shares.
Such issuance  could  adversely  affect the holders of common  stock,  and could
discourage  a third party from  acquiring a majority of our  outstanding  voting
stock.

     Additionally,  our board of directors has adopted certain amendments to our
by-laws  intended to strengthen  the board's  position in the event of a hostile
takeover attempt. The by-law provisions provide:

     o    Only persons who are nominated in accordance  with the  procedures set
          forth in the by-laws  shall be eligible  for  election as directors of
          Celgene, except as may be otherwise provided in the by-laws.

     o    Only  business  brought  before  the  annual  meeting  by the board of
          directors or by a  stockholder  who complies with the  procedures  set
          forth  in the  by-laws  may be  transacted  at an  annual  meeting  of
          stockholders.

     o    Only the chairman of the board, if any, the chief  executive  officer,
          the president,  the secretary, or a majority of the board of directors
          may call special meetings of our stockholders.

     o    A  procedure  for the board of  directors  is  established  to fix the
          record  date  whenever   stockholder  action  by  written  consent  is
          undertaken.

     o    A vote of holders of  two-thirds of the  outstanding  shares of Common
          Stock is required to amend certain by-law provisions.

Furthermore, Celgene is subject to the provisions of Section 203 of the Delaware
General Corporation Law, an anti-takeover law. In general, the statute prohibits
a publicly held Delaware  corporation from engaging in a "business  combination"
with an "interested  stockholder"  for a period of three years after the date of
the transaction in which the person became an interested stockholder, unless the
business combination is approved in a prescribed manner. For purposes of Section
203, a "business combination" includes a merger, asset sale or other transaction
resulting  in  a  financial  benefit  to  the  interested  stockholder,  and  an
"interested   stockholder"  is  a  person  who,  together  with  affiliates  and
associates,  owns (or  within  three  years  prior,  did own) 15% or more of the
corporation's voting stock.


                                        9

<PAGE>

We have not paid and do not intend to pay dividends on our common stock.

     We have never declared or paid cash  dividends on our common stock,  and do
not anticipate doing so in the foreseeable future.

The failure of  governmental  agencies and our vendors and  customers to be Year
2000 compliant could cause a material disruption in our business.

     Beginning in the Year 2000, the date fields coded in some software products
and  computer  systems  will  need to  accept  four  digit  entries  in order to
distinguish  21st century dates from 20th century  dates and, as a result,  many
companies'  software and computer systems may need to be upgraded or replaced in
order to comply with such "Year 2000" requirements.

     Systems that do not properly  recognize  such  information  could  generate
erroneous data or cause a system to fail. Significant  uncertainty exists in the
software  industry   concerning  the  potential  effects  associated  with  such
compliance issues.

     Our Chief Information  Officer, in conjunction with outside consultants has
assessed our systems with regard to Year 2000 compliance and the  implementation
for Year  2000  compliant  systems  is  completed.  All  hardware  and  software
applications  are Year 2000  compliant.  We have spent less than $1.0 million on
the systems upgrades. We use outside vendors to produce,  encapsulate,  package,
process orders,  invoice and maintain accounts  receivable records for THALOMID.
We have received  certifications from such vendors that the systems utilized are
or will be Year 2000  compliant  before the end of 1999.  Based on current plans
and efforts to date, we expect that there will be no material  adverse effect on
operations.  There  can be no  assurance,  however,  that all  problems  will be
foreseen  and  corrected,  that Year 2000  problems  at the  Company's  vendors,
customers, and at governmental agencies will not adversely affect us, or that no
material  disruption  of our  business  will  occur  as a  result  of Year  2000
problems.  Accordingly,  we have  developed  contingency  plans to  address  the
possible occurrence of Year 2000 problems.

     The statements  contained in the foregoing  Year 2000 readiness  disclosure
are subject to certain  protection under the Year 2000 Information and Readiness
Disclosure Act.



                                       10

<PAGE>

                              SELLING STOCKHOLDERS

     The following  table sets forth certain  information  regarding the sale by
the selling  stockholders of 1,707,850  shares of common stock in this offering.
Except as otherwise noted, each person named below has an address in care of our
principal executive offices.

     Except for Dr. Gilla Kaplan,  who is currently serving as a Director,  none
of the selling  stockholders  has held any  position or office or had a material
relationship  with Celgene or any of its affiliates  within the past three years
other than as a result of the ownership of Celgene's common stock and other than
as holder of the 9%  convertible  notes due January 20, 2004 and June 30,  2004.
The address of John Hancock Mutual Life Insurance Company, John Hancock Variable
Life Insurance Company,  Hancock Mezzanine Partners L.P., Signature 1A (Caymon),
Ltd. and  Signature 3 Limited is 200  Clarendon  Street,  Boston,  Massachusetts
02117.  The  address of each other of the  Selling  Stockholders  is c/o Celgene
Corporation, 7 Powder Horn Drive, Warren, New Jersey 07059.

<TABLE>
<S>                               <C>              <C>       <C>            <C>    <C>    <C>
                                     Shares                                Shares
                                  Beneficially               Number of   Beneficially
                                   Owned Prior                 Shares     Owned After
       Selling Stockholder         to Offering      %(1)      Offered      Offering         %(1)
John Hancock Mutual Life           777,199          45.       777,199        0               *
Insurance Company(2)                                 5
John Hancock Variable Life          26,901           1.6       26,901        0               *
Insurance Company(3)
Signature 1A (Cayman), Ltd.         27,780           1.6       27,780        0               *
(Nominee: Barrett & Co.)(4)
Signature 3 Limited                111,120           6.5      111,120        0               *
(Nominee: Hare & Co.)(5)
Hancock Mezzanine Partners (6)     679,850          39.8      679,850        0               *
Rockefeller University (7)          26,666           1.6       26,666        0               *
Dr. Gilla Kaplan (8)                 5,333            *         5,333        0               *
Dr. Elizabeth Sampaio (9)            2,667            *         2,667        0               *
Dr. Stephen J. Oliver (10)           2,667            *         2,667        0               *
Dr. Patrick A.J. Haslett (11)        2,667            *         2,667        0               *
Celgene Corporation 401(k)          45,000           2.6       45,000        0               *
Plan(12)
</TABLE>

- --------------------
*    Represents less than 1% of the outstanding shares of common stock.

(1)  Applicable  percentages  of  ownership  are based on  17,583,116  shares of
     common stock  outstanding  on December 22, 1999 adjusted as required by the
     rules  promulgated by the Securities and Exchange  Commission  (SEC).  This
     table is  based  upon  information  supplied  by  officers,  directors  and
     principal  stockholders  and  Schedules 13D and 35G (if any) filed with the
     SEC.  Any  security  that any person  named  above has the right to acquire
     within 60 days is deemed to be outstanding for purposes of


                                       11

<PAGE>

     calculating the percentage  ownership of such person,  but is not deemed to
     be outstanding for purposes of calculating the ownership  percentage of any
     other person.

(2)  Represents  777,199  shares of common stock  issuable  upon  conversion  of
     Celgene Convertible Notes due January 20, 2004 and June 30, 2004.

(3)  Represents  26,901  shares of common  stock  issuable  upon  conversion  of
     Celgene Convertible Notes due January 20, 2004 and June 30, 2004.

(4)  Represents  27,780  shares of common  stock  issuable  upon  conversion  of
     Celgene Convertible Notes due January 20, 2004.

(5)  Represents  111,120  shares of common stock  issuable  upon  conversion  of
     Celgene Convertible Notes due January 20, 2004.

(6)  Represents  679,850  shares of common stock  issuable  upon  conversion  of
     Celgene Convertible Notes due January 20, 2004 and June 30, 2004.

(7)  Represents  shares  issuable  upon  exercise of option to  purchase  26,666
     shares of Celgene common stock.

(8)  Represents shares issuable upon exercise of option to purchase 5,333 shares
     of Celgene common stock.

(9)  Represents shares issuable upon exercise of option to purchase 2,667 shares
     of Celgene common stock.

(10) Represents shares issuable upon exercise of option to purchase 2,667 shares
     of Celgene common stock.

(11) Represents shares issuable upon exercise of option to purchase 2,667 shares
     of Celgene common stock.

(12) Represents  45,000 shares of Celgene common stock granted by Celgene to the
     Celgene  Corporation 401(k) Plan (the "Plan") for sale from time-to-time by
     the trustees of the Plan on behalf of certain  employees  of Celgene  whose
     participation in the Plan has terminated.


                              PLAN OF DISTRIBUTION

     The common stock  covered by this  prospectus  may be offered and sold from
time  to  time  by the  selling  stockholders,  including  in one or more of the
following transactions:

     o   on the Nasdaq National Market;

     o   in transactions other than the Nasdaq National Market;

     o   in connection with short sales;

     o   by pledge to secure debts and other obligations;



                                       12

<PAGE>

     o    in connection with the writing of options, in hedge transactions,  and
          in   settlement   of   other    transactions    in   standardized   or
          over-the-counter options;

     o    in a combination of any of the above transactions; or

     o    pursuant to Rule 144,  assuming the  availability of an exemption from
          registration.

     The selling  stockholders may sell their shares at market prices prevailing
at the  time of  sale,  at  prices  related  to  prevailing  market  prices,  at
negotiated prices, or at fixed prices.

     Broker-dealers  that are used to sell shares will either receive  discounts
or commissions from the selling  stockholders,  or will receive commissions from
the purchasers for whom they acted as agents.

     The  sale of  common  stock  by the  selling  stockholders  is  subject  to
compliance by the selling  stockholders  with certain  contractual  restrictions
with Celgene,  including certain restrictions contained in a registration rights
agreement  between  Celgene  and  the  selling  stockholders.  There  can  be no
assurance  that the  selling  stockholders  will  sell all or any of the  common
stock.

     Celgene has agreed to keep this  prospectus  effective until the earlier of
(i)  June  30,  2001,  the  second  anniversary  of the  date  on  which  the 9%
convertible notes were initially issued (ii) the date on which all of the shares
of common stock registered hereby have been sold and (iii) the date on which all
of the shares of common stock registered  hereby may be immediately sold without
registration  or other legal  restriction.  Celgene intends to deregister any of
the common  stock not sold by the  selling  stockholders  immediately  after the
latest  date it is  required to keep this  prospectus  effective  for any of the
selling stockholders.

     Celgene   and  the   selling   stockholders   have   agreed  to   customary
indemnification  obligations with respect to the sale of the common stock by use
of this prospectus.

                                  LEGAL MATTERS

     Proskauer Rose LLP, New York, NY has passed on the validity of the shares.

                                     EXPERTS

     The consolidated financial statements of Celgene Corporation and subsidiary
as of December  31, 1998 and 1997,  and for each of the years in the  three-year
period ended December 31, 1998, have been  incorporated by reference  herein and
in the  registration  statement  in  reliance  upon  the  report  of  KPMG  LLP,
independent certified public accountants, incorporated by reference herein, upon
the authority of said firm as experts in accounting and auditing.

                       WHERE YOU CAN FIND MORE INFORMATION

     Celgene  files  reports  with  the  SEC on a  regular  basis  that  contain
financial  information  and  results  of  operations.  You may  read or copy any
document that Celgene files with the SEC at the SEC's Public  Reference  Room at
450 Fifth Street, N.W.,  Washington,  D.C. 20549 and 7 World Trade Center, Suite
1300,  New York,  New York 10048.  You may obtain  information  about the Public
Reference  Room by  calling  the SEC for  more  information  at  1-800-SEC-0330.
Celgene's   SEC   filings  are  also   available   at  the  SEC's  web  site  at
http://www.sec.gov.

                                       13

<PAGE>

                           INCORPORATION BY REFERENCE

     The SEC allows us to  "incorporate  by reference"  the  information we file
with them,  which means that we can  disclose  important  information  to you by
referring you to those documents.  The information  incorporated by reference is
considered to be part of this  prospectus,  and  information  that we file later
with the SEC will  automatically  update  and  supersede  this  information.  We
incorporate by reference the documents  listed below and any future filings that
we will  make  with the SEC  under  Sections  13(a),  13(c),  14 or 15(d) of the
Securities Exchange Act of 1934.

     1.   Annual Report on Form 10K for the fiscal year ended December 31, 1998,
          as amended by an  Amendment  on Form 10-K/A and an  Amendment  on Form
          10-K/A-2.

     2.   Quarterly  Report on Form 10-Q for the fiscal  quarter ended March 31,
          1999.

     3.   Quarterly  Report on Form 10-Q for the fiscal  quarter  ended June 30,
          1999.

     4.   Quarterly  Report on Form 10-Q for the fiscal quarter ended  September
          30, 1999.

     5.   The  description  of the  common  stock set forth in the  registration
          statement on Form 8-A, File No.  0-16132,  including any amendments or
          reports filed for the purpose of updating such description.

     You may  request  a copy of  these  filings,  at no  cost,  by  writing  or
telephoning our Secretary at the following address:

         Celgene Corporation
         7 Powder Horn Drive
         Warren, NJ 07059
         (732) 271-1001

     This prospectus is part of a registration  statement we filed with the SEC.
You should  rely only on the  information  or  representations  provided in this
prospectus. We have authorized no one to provide you with different information.
We are not making an offer of these  securities  in any state where the offer is
not permitted.  You should not assume that the information in this prospectus is
accurate as of any date other than the date on the front of the document.


                                       14

<PAGE>

                                     PART II

                     INFORMATION NOT REQUIRED IN PROSPECTUS


Item 14.  Other Expenses of Issuance and Distribution.

     An estimate (other than the SEC registration  fee) of the fees and expenses
of issuance and  distribution  (other than  discounts  and  commissions)  of the
Common  Stock  offered  hereby (all of which will be paid by the  Company) is as
follows:


     SEC registration fee...................................  $30,011.19
     NASDAQ National Market listing fee.....................   17,500.00

     Legal fees and expenses................................   10,000.00
     Accounting fees and expenses...........................    5,000.00
     Miscellaneous expenses.................................     ----

         Total.........................................      $ 62,511.19


Item 15.          Indemnification of Directors and Officers.

     The  General  Corporation  Law of the State of  Delaware  ("DGCL")  permits
Celgene and its  stockholders  to limit  directors'  exposure to  liability  for
certain breaches of the directors' fiduciary duty, either in a suit on behalf of
Celgene or in an action by stockholders of Celgene.

     The Certificate of Incorporation of Celgene (the "Charter")  eliminates the
liability of directors to stockholders  or Celgene for monetary  damages arising
out of the directors'  breach of their  fiduciary duty of care. The Charter also
authorizes  Celgene  to  indemnify  its  directors,   officers,   incorporators,
employees,  and agents  with  respect to certain  costs,  expenses,  and amounts
incurred in connection with an action, suit, or proceeding by reason of the fact
that such person was serving as a director, officer, incorporator,  employee, or
agent of Celgene. In addition, the Charter permits Celgene to provide additional
indemnification  rights to its officers and directors  and to indemnify  them to
the  greatest  extent  possible  under  the  DGCL.   Celgene  has  entered  into
indemnification  agreements  with each of its officers and directors and intends
to enter into  indemnification  agreements  with each of its future officers and
directors.  Pursuant to such indemnification  agreements,  Celgene has agreed to
indemnify  its officers and directors  against  certain  liabilities,  including
liabilities arising out of the offering made by this Registration Statement.

     Celgene  maintains a standard  form of officers' and  directors'  liability
insurance  policy  which  provides  coverage to the  officers  and  directors of
Celgene for certain  liabilities,  including certain liabilities which may arise
out of this Registration Statement.


                                      II-1

<PAGE>


Item 16.  Exhibits.

The exhibits listed in the Exhibit Index as filed as part of this Registration
Statement.

(a)  Exhibits

Exhibit
Number    Description
- ------   -------------
5.1--  Opinion of Proskauer Rose LLP.

23.1-- Consent of KPMG LLP.

23.2-- Consent of Proskauer Rose LLP (incorporated by reference to Exhibit 5.1).

24.1-- Power of Attorney (included in Signature Page).


Item 17.  Undertakings.

The undersigned Registrant hereby undertakes:

(1)  To file,  during  any  period in which  offers or sales are being  made,  a
     post-effective amendment to this Registration Statement: (i) to include any
     prospectus  required by Section  10(a)(3) of the  Securities  Act;  (ii) to
     reflect in the  prospectus  any facts or events arising after the effective
     date of the  Registration  Statement  (or the  most  recent  post-effective
     amendment  thereof) which,  individually  or in the aggregate,  represent a
     fundamental  change  in the  information  set  forth  in  the  Registration
     Statement.  Notwithstanding  the  foregoing,  any  increase  or decrease in
     volume of  securities  offered  (if the total  dollar  value of  securities
     offered would not exceed that which was  registered) and any deviation from
     the  low or  high  end of  the  estimated  maximum  offering  range  may be
     reflected in the form of prospectus  filed with the Commission  pursuant to
     Rule 424(b) (Section 230.424(b) of this chapter) if, in the aggregate,  the
     changes  in volume  and price  represent  no more than a 20%  change in the
     maximum  aggregate   offering  price  set  forth  in  the  "Calculation  of
     Registration Fee" table in the effective registration statement;  and (iii)
     to  include  any  material   information   with  respect  to  the  plan  of
     distribution not previously disclosed in the Registration  Statement or any
     material  change  to  such  information  in  the  Registration   Statement;
     provided,  however,  that  (i) and (ii) do not  apply  if the  Registration
     Statement  is on Form S-3 or Form S-8, and the  information  required to be
     included in a  post-effective  amendment  by (i) and (ii) is  contained  in
     periodic  reports  filed  with  or  furnished  to  the  Commission  by  the
     Registrant pursuant to Section 13 or Section 15(d) of the Exchange Act that
     are incorporated by reference in the Registration Statement.

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

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

                                      II-2

<PAGE>


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

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


                                      II-3

<PAGE>

                        SIGNATURES AND POWER OF ATTORNEY


     KNOW ALL MEN BY THESE PRESENTS,  that each person or entity whose signature
appears below constitutes and appoints John W. Jackson,  Sol J. Barer and Robert
J. Hugin,  and each of them, its true and lawful  attorneys-in-fact  and agents,
with full  power of  substitution  and  resubstitution,  for it and in its name,
place and stead,  in any and all  capacities,  to sign any and all amendments to
this Registration  Statement on Form S-3 and to file the same, with all exhibits
thereto,  and other documents in connection  therewith,  with the Securities and
Exchange Commission,  granting unto said  attorneys-in-fact and agents, and each
of them, full power and authority to do and perform each and every act and thing
requisite  and  necessary to be done, as fully to all intents and purposes as it
might or could do in  person,  hereby  ratifying  and  confirming  all that said
attorneys-in-fact  and  agents  or any of them,  or their or his  substitute  or
substitutes may lawfully do or cause to be done by virtue thereof.

     Pursuant to the  requirements of the Securities Act of 1933, the Registrant
certifies  that it has  reasonable  grounds to believe  that it meets all of the
requirements  for  filing  on Form S-3 and has  duly  caused  this  Registration
Statement  to be  signed  on its  behalf  by  the  undersigned,  thereunto  duly
authorized, in the city of Warren, State of New Jersey on December 28, 1999.

                                           CELGENE CORPORATION


                                           By:      /s/ John W. Jackson
                                                    ---------------------
                                                    John W. Jackson
                                                    Chairman of the Board
                                                    and Chief Executive Officer


Pursuant to the requirements of the Securities Act, this Registration  Statement
has been signed  below by the  persons  whose  signatures  appear  below,  which
persons have signed such Registration Statement in the capacities indicated:



Signature                             Title                         Date
- ---------                             -----                         ----
/s/ John W. Jackson              Chairman of the             December 28, 1999
- --------------------------       Board and Chief
John W. Jackson                  Executive Officer
                                 (Principal Executive
                                 Officer)

/s/ Sol J. Barer, Ph.D.          Director                    December 28, 1999
- --------------------------
Sol J. Barer, Ph.D.

/s/ Robert Hugin                 Chief Financial Officer     December 28, 1999
- --------------------------       (Principal Accounting and
Robert J. Hugin                  Financial Officer)

/s/ Jack L. Bowman               Director                    December 28, 1999
- --------------------------
Jack L. Bowman



                                      II-4

<PAGE>

                                 Director                    December 28, 1999
- --------------------------
Frank T. Cary

/s/ Gilla Kaplan, Ph.D.          Director                    December 28, 1999
- --------------------------
Gilla Kaplan, Ph.D.
                                 Director                    December 28, 1999

- --------------------------
Arthur Hull Hayes, Jr., M.D.
                                 Director                    December 28, 1999


- --------------------------
Richard C.E. Morgan
                                 Director                    December 28, 1999
/s/ Walter L. Robb, Ph.D.
- --------------------------
Walter L. Robb, Ph.D.
                                 Director                    December 28, 1999
- --------------------------
Lee J. Schroeder


                                      II-5

<PAGE>

                                INDEX TO EXHIBITS


5.1  -- Opinion of Proskauer Rose LLP.

23.1 -- Consent of KPMG LLP.

23.2 -- Consent of Proskauer Rose LLP (incorporated by reference to Exhibit 5.1)

24.1 -- Power of Attorney (included in Signature Page).


                                      II-6

<PAGE>

EXHIBIT 5.1


                                                              December 28, 1999



Celgene Corporation
7 Powder Horn Drive
Warren, New Jersey  07059

Dear Sirs:

     We are acting as counsel to  Celgene  Corporation,  a Delaware  corporation
(the "Company"),  in connection with the registration statement on Form S-3 with
exhibits thereto (the  "Registration  Statement") filed by the Company under the
Securities Act of 1933, as amended,  and the rules and  regulations  promulgated
thereunder,  relating to the  registration of 1,707,850 shares (the "Shares") of
common stock,  par value $.01 per share,  of the Company.  All of the Shares are
issuable upon the exercise of options (the  "Options")  and the  conversion of a
convertible  note (the  "Convertible  Note") or have been  issued to the Celgene
Corporation 401(k) Plan (the "Plan") and may be offered for sale for the benefit
of the selling stockholders named in the Registration  Statement.  We understand
that the Shares  are to be sold from time to time as  described  in the  section
entitled "Plan of Distribution" in the Registration Statement.

     As  such  counsel,   we  have   participated  in  the  preparation  of  the
Registration  Statement and have reviewed the corporate  minutes relating to the
issuance of the Shares  pursuant to the Plan and have also  examined  and relied
upon  originals  or  copies,   certified  or  otherwise   authenticated  to  our
satisfaction,  of  all  such  corporate  records,  documents,   agreements,  and
instruments relating to the Company, and certificates of public officials and of
representatives of the Company.

     Based upon, and subject to, the foregoing, we are of the opinion,  assuming
no change in the applicable law or pertinent  facts,  that (i) the Shares,  when
issued in accordance with the terms of the Options or the  Convertible  Note, as
the case may be,  will be duly  authorized,  validly  issued,  fully  paid,  and
non-assessable and (ii) the Shares issued to the Celgene Corporation 401(k) Plan
have been duly authorized, validly issued, fully paid and non-assessable.

     We hereby  consent  to the filing of this  opinion  as  Exhibit  5.1 to the
Registration Statement. In giving the foregoing consent, we do not admit that we
are in the category of persons whose consent is required  under Section 7 of the
Securities  Act of  1933,  as  amended,  or the  rules  and  regulations  of the
Securities and Exchange Commission promulgated thereunder.


                                                     Very truly yours,


                                                     /s/ Proskauer Rose LLP


                                      II-7

<PAGE>


EXHIBIT 23.1


CONSENT OF INDEPENDENT AUDITORS


The Board of Directors Celgene Corporation:

We consent to the use of our report incorporated herein by reference and to the
reference to our firm under the heading "EXPERTS" in the prospectus.


                                                    /s/KPMG LLP

Short Hills, New Jersey
December 28, 1999




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