EXHIBIT 10.19

                       CONVERTIBLE NOTE PURCHASE AGREEMENT

                                                              September 16, 1998

Warburg Dillon Read LLC
677 Washington Blvd.
Stamford, CT 06901

Dear Sirs:

     CELGENE  CORPORATION (the "Company") wishes to confirm its arrangement with
you in connection with the issuance to you today, against payment in immediately
available  funds of the purchase price of 100% of the principal  amount thereof,
of a convertible  note in the form attached hereto as Annex I (the  "Convertible
Note") in an aggregate principal amount of $8,750,000 and convertible  initially
into  795,463  fully paid and  non-assessable  shares  (each a  "Share")  of the
Company's Common Stock,  par value $.01 per share (the "Common Stock"),  subject
to adjustment as set forth in the  Convertible  Note. In  consideration  of your
purchase of the  Convertible  Note,  the Company will pay to you, in immediately
available  funds, a fee of 5% of the principal  amount  thereof,  which shall be
netted against the purchase price of the Convertible Note.

     Simultaneously  with the issuance of the Convertible  Note pursuant to this
Agreement,  you  and  the  Company  have  entered  into  a  Registration  Rights
Agreement,  dated as of the date hereof (the "Registration  Rights  Agreement"),
pursuant to which the Company has agreed to register  the Shares  under  certain
circumstances.  All capitalized  terms not defined herein shall have the meaning
ascribed in the Convertible Note.

     1. AGREEMENT TO ISSUE AND ACCEPT. On the basis of the  representations  and
warranties and subject to the terms and conditions set forth herein, the Company
agrees  to  issue  to you,  and you  agree  to  accept  from  the  Company,  the
Convertible Note against payment of the above-specified purchase price therefor,
The closing of the issuance and acceptance of the Convertible  Note against such
payment  shall take place on the date  hereof,  at which time the Company  shall
deliver to you the

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Convertible  Note,  against  delivery by you of a wire  transfer of the purchase
price to the Company's  account at PNC Bank New Jersey Trust, ABA No. 031000053,
benefit   Account   No.   8511074024,   for   further   credit  to  Account  No.
42432012020943,  Celgene Corporation, Attn: Lisa Goldhammer, Telephone No. (732)
220-3112.

     2.  REPRESENTATIONS AND WARRANTIES OF THE COMPANY. The Company hereby makes
the representations and warranties to you set forth on Annex II hereto.

     3.  AGREEMENTS OF PURCHASER. You covenant and agree with the Company that:

          (a) You  will  not  offer,  sell,  assign,  hypothecate  or  otherwise
     transfer  the  Convertible   Note  except  (i)  pursuant  to  an  effective
     registration  statement under the Securities Act of 1933 (the "Act"),  (ii)
     to a person you reasonably  believe to be an "accredited  investor"  within
     the meaning of Rule 501 under the Act,  pursuant to an available  exemption
     under the Act or (iii) in  offshore  transactions  within the  meaning  and
     meeting the requirements of Rule 903 under the Act.

          (b) You  will  not  offer,  sell,  assign,  hypothecate  or  otherwise
     transfer any Shares issued upon conversion of the  Convertible  Note except
     (i) pursuant to an effective  registration statement under the Act; (ii) to
     a person you reasonably  believe to be an "accredited  investor" within the
     meaning of Rule 501 under the Act, pursuant to an available exemption under
     the Act or (iii) in an offshore  transaction within the meaning and meeting
     the requirements of Rule 903 under the Act.

          (c) You are an  "accredited  investor"  within the meaning of Rule 501
     under the Act.

          (d) You will not, in hedging transactions  effected in connection with
     your purchase and holding of the Convertible  Note,  effect sales of Common
     Stock (other than "blocks" of Common Stock, as defined in Rule 10b-18 under
     the  Securities  Exchange Act of 1934) in an amount that  exceeds,  for any
     trading day, 25% of the "trading volume" of the Common Stock (as defined in
     Rule 10b-18).

     4. CONDITIONS.  Your  obligations  under this Agreement shall be subject to
the condition that all  representations  and warranties and other  statements of
the Company herein are true and correct at and as of the closing of the purchase
and sale of the  Convertible  Note,  the  condition  that the Company shall have
performed all of its obligations hereunder theretofore to be performed,  and the
following additional conditions:

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          (a) Counsel for the Company  specified  in Annex III hereto shall have
     furnished to you their respective written opinions,  dated the date of such
     closing, in form and substance satisfactory to you, to the effect set forth
     in Annex III hereto.

          (b) On the date of such closing,  the Company shall have  furnished to
     you such appropriate further information, certificates and documents as you
     may reasonably request.

     5. MISCELLANEOUS.

     (a) This  Agreement  shall be binding upon, and inure solely to the benefit
of, you and the Company and the respective  successors and assigns thereof,  and
no other  person  shall  acquire  or have any  right  under or by virtue of this
Agreement.  No  purchaser  of the  Convertible  Note  from you shall be deemed a
successor or assign by reason merely of such purchase.

     (b) Any notice or other  communication  required or  permitted  to be given
hereunder shall be deemed effectively given when personally delivered,  telexed,
transmitted by facsimile or mailed by pre-paid  certified  mail,  return receipt
requested,  or by telephone  when  confirmed in writing by one of the  preceding
methods addressed as follows (as applicable):




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               If to the Company, to:

               Celgene Corporation
               7 Powder Horn Drive
               Warren, NJ 07059

               Attention: John W. Jackson
               Telephone Number: (732) 271-1001
               Facsimile Transmission Number: (732) 805-3931

               with a copy to:

               Proskauer Rose LLP
               1585 Broadway
               New York, NY 10036

               Attention: Robert A. Cantone, Esq.
               Telephone Number: (212) 969-3000
               Facsimile Transmission Number: (212) 969-2900

               If to Warburg Dillon Read LLC, to:

               Warburg Dillon Read LLC
               677 Washington Blvd.
               Stamford, CT 06901

               Attention: General Counsel
                          Capital Markets '
               Telephone Number: (203) 719-3000
               Facsimile Transmission Number: (201) 719-6097

or to such other  address or number and to the attention of such other person as
either party may designate by written notice to the other party. Notice shall be
effective upon actual receipt.

     (c) THIS  AGREEMENT  SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE  WITH
THE LAWS OF THE STATE OF NEW YORK.

     (d) Time shall be of the essence in the performance of this Agreement.

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     (e) This  Agreement may be executed by the parties  hereto in any number of
counterparts,  each of which  shall be  deemed to be an  original,  but all such
respective counterparts shall together constitute one and the same instrument.

                                              Very truly yours,

                                              CELGENE CORPORATION

                                              By:
                                                 -------------------------------
                                                 Name:
                                                 Title:

Accepted as of the date hereof:

WARBURG DILLON READ LLC

By:
   -------------------------------
   Name:
   Title:






                                                                        ANNEX II

                  REPRESENTATIONS AND WARRANTIES OF THE COMPANY

     (a) Each of the  Company's  Annual  Report on Form 10-K for the year  ended
December 31, 1997, and each report filed by the Company pursuant to the Exchange
Act  after the  filing of such  Annual  Report on Form 10-K  (collectively,  the
"Exchange Act Reports")  conforms in all material respects with the requirements
of the Exchange Act and the rules and regulations of the Securities and Exchange
Commission  thereunder;  and no such  document,  when it was  filed  (or,  if an
amendment  with respect to any such document was filed,  when such amendment was
filed),  contained any untrue statement of a material fact or omitted to state a
material fact required to be stated  therein or necessary to make the statements
therein,  in the light of the  circumstances  under  which they were  made,  not
misleading,

     (b) All the  outstanding  shares of capital  stock of the Company have been
duly  authorized and validly issued and are fully paid,  non-assessable  and not
subject to any preemptive or similar rights;  the Shares initially issuable upon
conversion of the  Convertible  Note have been duly and validly  authorized  and
reserved for issuance out of the  Company's  authorized  and unissued  shares of
Common Stock and, when issued and delivered in accordance with the provisions of
the  Convertible  Note  will  be  duly  and  validly  issued,   fully  paid  and
non-assessable and will conform to the description of the Common Stock contained
in the Company's Registration Statement on Form 8-A, File No. 0-16132.

     (c) The  Convertible  Note has been duly  authorized  and,  when issued and
delivered pursuant to this Agreement,  will have been duly executed,  issued and
delivered  and will  constitute a valid and legally  binding  obligation  of the
Company;  and the  Registration  Rights  Agreement has been duly authorized and,
when executed and delivered by the parties thereto,  will constitute a valid and
legally  binding  obligation of the Company,  enforceable in accordance with its
terms, subject, as to enforcement, to bankruptcy, insolvency, reorganization and
other laws of general  applicability  relating to or affecting creditors' rights
and to general equity principles.

     (d)  The  execution,  delivery  and  performance  of  this  Agreement,  the
Registration  Rights  Agreement  and the  Convertible  Note,  compliance  by the
Company  with all  provisions  hereof and  thereof and the  consummation  of the
transactions   contemplated   hereby  and  the  issuance  and  delivery  of  the
Convertible  Note will not  conflict  with or  constitute a breach of any of the
terms or  provisions  of, or a default  under,  the  charter  or  by-laws of the
Company  or any of  its  subsidiaries,  or any  agreement,  indenture  or  other
instrument to which it or any of its  subsidiaries  is a party or by which it or
any of its subsidiaries or their respective  properties are bound, or violate or
conflict with any laws,  administrative  regulations or rulings or court decrees
applicable to the Company, any of its subsidiaries or their respective property;





and, except (i) as required pursuant to the Registration  Rights  Agreement,  or
(ii) for the disclosure  required to be included in the Company's next Quarterly
Report on Form 10-Q, when filed, pursuant to Item 2(c) of Form 10-Q, no consent,
approval,  authorization  or order of or filing or  registration  with, any such
court or governmental agency or body is required for the execution, delivery and
performance  of  this  Agreement,  the  Registration  Rights  Agreement  and the
Convertible  Note  by the  Company  and  the  consummation  of the  transactions
contemplated hereby and thereby.

     (e) Except as otherwise set forth in the Exchange Act Reports, there are no
material legal or governmental  proceedings  pending to which the Company or any
of its subsidiaries is a party or of which any of their  respective  property is
the subject which, if determined  adversely to the Company or its  subsidiaries,
might have a material  adverse effect on the business,  condition  (financial or
otherwise),  stockholders' equity, properties,  business prospects or results of
operations  of the Company and its  subsidiaries,  taken as a whole (a "Material
Adverse  Effect"),  and,  to  the  best  of the  Company's  knowledge,  no  such
proceedings are threatened or contemplated.

     (f) The Company is not, and the Company covenants that at any time when the
Convertible Note is outstanding it will not be, an open-end  investment company,
unit investment trust or face-amount  certificate company that is or is required
to be registered under Section 8 of the United States Investment  Company Act of
1940, as amended.

     (g) When the  Convertible  Note is issued and  delivered  pursuant  to this
Agreement,  the  Convertible  Note  will not be of the same  class  (within  the
meaning of Rule 144A under the Securities  Act of 1933) as securities  which are
listed on a  national  securities  exchange  registered  under  Section 6 of the
Exchange Act or quoted in a U.S. automated inter-dealer quotation system.

     (h) The Company is, and the Company  covenants  that while the  Convertible
Note is  outstanding  it will  remain,  subject  to  Section  13 or 15(d) of the
Exchange Act.

     (i) Neither the Company nor any person  acting on its behalf has offered or
sold the  Convertible  Note by  means of any  general  solicitation  or  general
advertising within the meaning of Rule 502(c) under the Act.


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                                                                       ANNEX III

                           OPINION OF COMPANY COUNSEL

     (a) The  Company  has been duly  incorporated,  is  validly  existing  as a
corporation in good standing under the laws of its jurisdiction of incorporation
and has the corporate  power and authority  required to carry on its business as
described  in the  Exchange  Act  Reports  and to own,  lease  and  operate  its
properties.

     (b) All the  outstanding  shares of Common Stock have been duly  authorized
and  validly  issued and are fully paid,  non-assessable  and not subject to any
preemptive or similar rights.

     (c) The Shares  initially  issuable upon conversion of the Convertible Note
have  been duly  authorized  and  reserved  for  issuance  and when  issued  and
delivered upon  conversion in accordance  with the provisions of the Convertible
Note,  will have been validly issued and will be fully paid and  non-assessable,
and the  issuance  of such Shares is not  subject to any  preemptive  or similar
rights.

     (d) This Agreement has been duly authorized,  executed and delivered by the
Company.

     (e) The Convertible  Note has been duly  authorized,  executed,  issued and
delivered,  and  constitutes  the valid and legally  binding  obligation  of the
Company  enforceable  in  accordance  with its  terms,  subject  to  bankruptcy,
insolvency, fraudulent transfer, reorganization,  moratorium and similar laws of
general applicability  relating to or affecting creditors' rights and to general
equity principles.

     (f) The Registration  Rights  Agreement has been duly authorized,  executed
and  delivered  by the  Company  and  constitutes  a valid and  legally  binding
agreement of the Company,  enforceable in accordance with its terms,  subject to
bankruptcy,  insolvency,  fraudulent  transfer,  reorganization,  moratorium and
similar laws of general applicability relating to or affecting creditors' rights
and to general  equity  principles;  provided  that such counsel need express no
opinion with respect to Section 6 of such Agreement.

     (g) The  authorized  capital  stock of the  Company,  including  the Common
Stock,  conforms as to legal matters to the description thereof contained in the
Company's Registration Statement on Form 8-A, File No. 0-16132.

     (h) Except (i) as required  pursuant to the Registration  Rights Agreement,
or (ii)  for the  disclosure  required  to be  included  in the  Company's  next
Quarterly  Report on Form 10-Q, when filed,  pursuant to Item 2(c) of Form 10-Q,
no consent, approval,  authorization or order of or filing or registration with,
any court or governmental





agency or body is required for the execution,  delivery and  performance of this
Agreement,  the  Registration  Rights  Agreement and the Convertible Note by the
Company and the consummation of the transactions  contemplated by this Agreement
and thereby,

     (i)  The  execution,  delivery  and  performance  of  this  Agreement,  the
Registration   Rights  Agreement  and  the  Convertible  Note  by  the  Company,
compliance  by the Company  with all the  provisions  hereof and thereof and the
consummation  of the  transactions  contemplated  hereby  and  thereby  will not
conflict with or constitute a breach of any of the terms or provisions  of, or a
default under, the charter or by-laws of the Company or any agreement, indenture
or other  instrument  to which the Company is a party or by which the Company or
its properties are bound,  or violate or conflict with any laws,  administrative
regulations  or  rulings  or court  decrees  applicable  to the  Company  or its
properties  in any case which is  reasonably  likely to have a Material  Adverse
Effect.

     (j) The  Company is not an open-end  investment  company,  unit  investment
trust or face-amount certificate company that is or is required to be registered
under Section 8 of the United States Investment Company Act of 1940, as amended.






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