<PAGE>   1



   As filed with the Securities and Exchange Commission on September 26, 1997

                                                    REGISTRATION NO. 333 -

================================================================================

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

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

                                    FORM S-8
                             REGISTRATION STATEMENT
                                    UNDER THE
                             SECURITIES ACT OF 1933

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

                           ARIAD PHARMACEUTICALS, INC.
             (Exact name of Registrant as specified in its charter)

              DELAWARE                                          22-3106987
 ---------------------------------                          -------------------
   (State or other jurisdiction                              (I.R.S. Employer
 of incorporation or organization)                          Identification No.)

                              26 LANDSDOWNE STREET
                       CAMBRIDGE, MASSACHUSETTS 02139-4234

                    (Address of Principal Executive Offices)

              1991 STOCK OPTION PLAN FOR EMPLOYEES AND CONSULTANTS

                1994 STOCK OPTION PLAN FOR NON-EMPLOYEE DIRECTORS

                        1997 EMPLOYEE STOCK PURCHASE PLAN
                           (Full titles of the plans)

                                 JAY R. LAMARCHE
              EXECUTIVE VICE PRESIDENT AND CHIEF FINANCIAL OFFICER
                           ARIAD PHARMACEUTICALS, INC.
                              26 LANDSDOWNE STREET
                       CAMBRIDGE, MASSACHUSETTS 02139-4234
                                 (617) 494-0400
    (Name, address, including zip code, and telephone number, including area
                           Code, of agent for service)

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

                         CALCULATION OF REGISTRATION FEE

<TABLE>
<CAPTION>
===============================================================================================================
           Title of                 Amount to be         Proposed            Proposed             Amount of
 securities to be registered        registered(1)         maximum             maximum          registration fee
                                                      offering price         aggregate
                                                       per share(2)      offering price(2)

---------------------------------------------------------------------------------------------------------------
<S>                                  <C>                  <C>               <C>                     <C>
Common Stock,  $.01 par value        3,000,000            $5.28             $15,843,750             $4,802            
===============================================================================================================
</TABLE>


(1)  The number of shares of common stock, par value $.01 per share ("Common
     Stock"), stated above consists of the aggregate number of additional shares
     not previously registered which may be sold upon the exercise of options
     which have been granted and/or may hereafter be granted under the ARIAD
     Pharmaceuticals, Inc. 1991 Stock Option Plan for Employees and Consultants,
     the ARIAD Pharmaceuticals, Inc. 1994 Stock Option Plan for Non-Employee
     Directors, and the ARIAD Pharmaceuticals, Inc. 1997 Stock Purchase Plan
     (the "Plans"). The maximum number of shares, which may be sold upon the
     exercise of such options granted under the Plans, is subject to adjustment
     in accordance with certain anti-dilution and other provisions of the Plans.
     Accordingly, pursuant to Rule 416 under the Securities Act of 1933, as
     amended (the "Securities Act"), this Registration Statement covers, in
     addition to the number of shares stated above, an indeterminate number of
     shares which may be subject to grant or otherwise issuable after the
     operation of any such anti-dilution and other provisions.

(2)  Pursuant to the provisions of Rule 457(h) under the Securities Act, the
     registration fee with respect to all 3,000,000 shares being registered
     hereunder, options for which have not yet been granted and the option price
     of which is therefore unknown, is calculated on the basis of the average of
     the high and low sale prices per share of the Common Stock on The Nasdaq
     Stock Market ("Nasdaq") as of a date (September 23, 1997) within 5 business
     days prior to filing this Registration Statement.

================================================================================


<PAGE>   2



                                EXPLANATORY NOTE


         In accordance with the instructional Note to Part I of Form S-8 as
promulgated by the Securities and Exchange Commission, the information specified
by Part I of Form S-8 has been omitted from this Registration Statement on Form
S-8 for offers of Common Stock pursuant to the Plans.


<PAGE>   3





                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT


ITEM 3.  INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE.

         The following documents filed by the Company with the Commission
pursuant to the Exchange Act, are incorporated by reference in this Prospectus:
(a) the Company's Annual Report on Form 10-K for the year ended December 31,
1996; (b) the Company's Quarterly Reports on Form 10-Q for the quarterly periods
ended March 31, 1997 and June 30, 1997; (c) the Company's Proxy Statement for
its annual meeting of stockholders held on June 20, 1997 (other than the
portions thereof identified as not deemed filed with the Commission); and (d)
the description of the Common Stock which is contained in the Company's
registration statement on Form 10 filed with the Commission on June 25, 1993,
including all amendments and reports filed for the purpose of updating such
description. All documents filed by the Company with the Commission pursuant to
Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act after the date of this
Prospectus and prior to the termination of the offering made hereby shall be
deemed to be incorporated by reference in this Prospectus and to be a part
hereof from the date of filing of such documents. Any statement contained in a
document incorporated or deemed to be incorporated by reference shall be deemed
to be modified or superseded to the extent that a statement contained in any
subsequently filed document which also is or is deemed to be incorporated by
reference herein or therein modifies or supersedes such statement. Any statement
so modified or superseded shall not be deemed, except as so modified or
superseded, to constitute a part hereof.

ITEM 4. DESCRIPTION OF SECURITIES.

         Not applicable.

ITEM 5. INTERESTS OF NAMED EXPERTS AND COUNSEL.

         The validity of the issuance of the shares of Common Stock registered
under this Registration Statement has been passed upon for the Company by Mintz,
Levin, Cohn, Ferris, Glovsky and Popeo, P.C. of Boston, Massachusetts. Members
of Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C. own an aggregate of
approximately 201,700 shares of Common Stock of the Company.

ITEM 6. INDEMNIFICATION OF DIRECTORS AND OFFICERS.

         Section 145(a) of the General Corporation Law of the State of Delaware
provides that a Delaware corporation may indemnify any person who was or is a
party or is threatened to be made a party to any threatened, pending or
completed action, suit or proceeding, whether civil, criminal, administrative or
investigative (other than an action by or in the right of the corporation) by
reason of the fact that he is or was a director, officer, employee or agent of
the corporation or is or was serving at the request of the corporation as a
director, officer, employee or agent of another corporation or enterprise,
against expenses, judgments, fines and amounts paid in settlement actually and
reasonably incurred by him in connection with such action, suit or proceeding if
he acted in good faith and in a manner he reasonably believed to be in or not
opposed to the best interests of the corporation, and, with respect to 


                                      II-1


<PAGE>   4

any criminal action or proceeding, had no cause to believe his conduct was
unlawful.

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

         Section 145 further provides that to the extent a director or officer
of a corporation has been successful in the defense of any action, suit or
proceeding referred to in subsections (a) and (b) or in the defense of any
claim, issue or matter therein, he shall be indemnified against expenses
actually and reasonably incurred by him in connection therewith; that
indemnification provided for by Section 145 shall not be deemed exclusive of any
other rights to which the indemnified party may be entitled; and that the
corporation may purchase and maintain insurance on behalf of a director or
officer of the corporation against any liability asserted against him or
incurred by him in any such capacity or arising out of his status as such
whether or not the corporation would have the power to indemnify him against
such liabilities under such Section 145.

         The Certificate of Incorporation, as amended, and By-laws of the
Company provide for indemnification of the Company's directors and officers to
the fullest extent permitted by law. The By-laws also permit the Board of
Directors to authorize the Company to purchase and maintain insurance against
any liability asserted against any director, officer, employee or agent of the
Company arising out of his capacity as such. Insofar as indemnification for
liabilities under the Securities Act may be permitted to directors, officers, or
controlling persons of the Company pursuant to the Company's Certificate of
Incorporation, as amended, its By-laws and the Delaware General Corporation Law,
the Company has been informed that in the opinion of the Commission such
indemnification is against public policy as expressed in such Act and is
therefore unenforceable.

         As permitted by the Delaware General Corporation Law, the Company's
Certificate of Incorporation, as amended, provides that directors of the Company
shall not be personally liable to the Company or its stockholders for monetary
damages for breach of fiduciary duty as a director, except for liability (i) for
any breach of the director's duty of loyalty to the Company or its stockholders,
(ii) for acts or omissions not in good faith or which involve intentional
misconduct or a knowing violation of law, (iii) under Section 174 of the
Delaware General Corporation Law, relating to prohibited dividends or
distributions or the repurchase or redemption of stock or (iv) for any
transaction from which the director derives an improper personal benefit. As a
result of this provision, the Company and its stockholders may be unable to
obtain monetary damages from a director for breach of his or her duty of care.

ITEM 7. EXEMPTION FROM REGISTRATION CLAIMED.

         Not applicable.



                                      II-2
<PAGE>   5


ITEM 8. EXHIBITS.


  4.1             Form of Warrant Agreement (with Form of Warrant). (1)
  4.2             Rights Agreement, dated as of December 15, 1994, between the
                  Company and State Street Bank and Trust Company, which
                  includes the Certificate of Designations in respect of the
                  Series A Preferred Stock, as Exhibit A, the Form of Right
                  Certificate as Exhibit B and the Summary of Rights to Purchase
                  Series A Preferred Stock as Exhibit C. Pursuant to the Rights
                  Agreement, Right Certificates will not be mailed until after
                  the Separation Date (as defined therein). (2)
  4.3             Amendment, dated as of April 24, 1995, to Rights Agreement,
                  dated as of December 15, 1994, between ARIAD Pharmaceuticals,
                  Inc. and State Street Bank and Trust Company. (3)
  4.4             Stock Purchase Agreement, dated as of April 24, 1995, between
                  ARIAD Pharmaceuticals, Inc. and Biotech Target S.A. (4)
  5.1             Opinion of Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C.
                  as to the legality of shares being registered. (5)
  23.1            Consent of Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C.
                  (included in opinion of counsel filed as Exhibit 5.1). (5)
  23.2            Consent of Deloitte & Touche LLP. (5) 
  24.1            Power of Attorney

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

(1)     Incorporated by reference to registration statement on Form S-1 of the
        Company (No. 33-76414) filed with the Securities and Exchange Commission
        on March 11, 1994.

(2)     Incorporated by reference to Form 8-K of the Company filed with the
        Securities and Exchange Commission on December 21, 1994.

(3)     Incorporated by reference to Form 8-K of the Company filed with the
        Securities and Exchange Commission on May 15, 1995.

(4)     Incorporated by reference to Form 10-K of the Company for the fiscal
        year ended December 31, 1995 and filed with the Securities and Exchange
        Commission on March 15, 1996.

(5)     Filed herewith.

     ITEM 9.  UNDERTAKINGS.

     (a)  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 of 1933;

              (ii)  To reflect in the prospectus any facts or events arising
                    after the effective date of the 



                                      II-3

<PAGE>   6

                    Registration Statement (or the most recent post-effective
                    amendment thereof) which, individually or in the aggregate,
                    represents 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.

              (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 paragraphs
                    (a)(1)(i) and (a)(1)(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
                    those paragraphs is contained in periodic reports filed by
                    the Registrant pursuant to Section 13 or Section 15(d) of
                    the Securities Exchange Act of 1934 that are incorporated by
                    reference in this Registration Statement.

       (2) That, for the purpose of determining any liability under the
           Securities Act of 1933, 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 bonafide offering thereof.

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

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

     (c)  Insofar as indemnification for liabilities arising under the
          Securities Act of 1933 may be permitted to directors, officers and
          controlling persons of the Registrant pursuant to the foregoing
          provisions, or otherwise, the Registrant has been advised that in the
          opinion of the Securities and Exchange Commission such indemnification
          is against public policy as expressed in the Act and is, therefore,
          unenforceable. In the event that a claim for indemnification against
          such liabilities (other than the payment by the Registrant 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 Act and will be
          governed by the final adjudication of such issue.



                                      II-4
<PAGE>   7





                                   SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, the Registrant has
duly caused this registration statement to be signed on its behalf by the
undersigned, thereunto duly authorized, in the City of Cambridge and
Commonwealth of Massachusetts on the 26th of September, 1997.


                            ARIAD PHARMACEUTICALS, INC.

                            By: /s/ Jay R. LaMarche
                                ------------------------------------------------
                            Executive Vice President and Chief Financial Officer




                                      II-5
<PAGE>   8


                                POWER OF ATTORNEY

    The registrant and each person whose signature appears below constitutes and
appoints Harvey J. Berger, M.D. and Jay R. LaMarche and each of them singly,
his, her or its true and lawful attorneys-in-fact and agents, with full power of
substitution and resubstitution, for him, her or it and in his, her or its name,
place and stead, in any and all capacities, to sign and file (i) any and all
amendments (including post-effective amendments) to this registration statement,
with all exhibits thereto, and other documents in connection therewith, and (ii)
a registration statement, and any and all amendments thereto, relating to the
offering covered hereby filed pursuant to Rule 462(b) under the Securities Act
of 1933, 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 or necessary to be done in
and about the premises, as fully to all intents and purposes as he, she, or 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 hereof.

          Pursuant to the requirements of the Securities Act of 1933, this
registration statement has been signed below by the following persons and in the
capacities indicated on the 26th of September, 1997.

<TABLE>
<CAPTION>
         Signature                                Title                          Date
         ---------                                -----                          ----

  <S>                            <C>                                             <C>    
  /s/ Harvey J. Berger           Chairman of the Board of Directors, President   September 26,1997
  ----------------------------   and Chief Executive Officer
  Harvey J. Berger, M.D.         
  
  /s/ Edgar Haber                Vice Chairman of the Board of Directors         September 26,1997
  ----------------------------
  Edgar Haber, M.D.

  /s/ Jay R. LaMarche            Executive Vice President, Chief Financial       September 26,1997
  ----------------------------   Officer, Treasurer and Director (Principal
  Jay R. LaMarche                Financial and Accounting Officer)

  /s/ Joan S. Brugge             Director                                        September 26,1997
  ----------------------------
  Joan S. Brugge, Ph.D.

  /s/ Vaughn D. Bryson           Director                                        September 26,1997
  ----------------------------
  Vaughn D. Bryson

  /s/ Philip Felig               Director                                        September 26,1997
  ----------------------------
  Philip Felig, M.D.

  /s/ John M. Deutch             Director                                        September 26,1997
  ----------------------------
  John M. Deutch, Ph.D.

  /s/ Peter T. Joseph            Director                                        September 26,1997
  ---------------------------- 
  Peter T. Joseph

  /s/ Joel S. Marcus             Director                                        September 26,1997
  ----------------------------
  Joel S. Marcus

  /s/ Sandford D. Smith          Director                                        September 26,1997
  ----------------------------
  Sandford D. Smith

  /s/ Raymond S. Troubh          Director                                        September 26,1997
  ---------------------------- 
  Raymond S. Troubh
</TABLE>





                                      II-6
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1

   As filed with the Securities and Exchange Commission on September 26, 1997

                                                    REGISTRATION NO. 333 -

================================================================================

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

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

                                    FORM S-8
                             REGISTRATION STATEMENT
                                    UNDER THE
                             SECURITIES ACT OF 1933

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

                           ARIAD PHARMACEUTICALS, INC.
             (Exact name of Registrant as specified in its charter)

              DELAWARE                                          22-3106987
 ---------------------------------                          -------------------
   (State or other jurisdiction                              (I.R.S. Employer
 of incorporation or organization)                          Identification No.)

                              26 LANDSDOWNE STREET
                       CAMBRIDGE, MASSACHUSETTS 02139-4234

                    (Address of Principal Executive Offices)

              1991 STOCK OPTION PLAN FOR EMPLOYEES AND CONSULTANTS

                1994 STOCK OPTION PLAN FOR NON-EMPLOYEE DIRECTORS

                        1997 EMPLOYEE STOCK PURCHASE PLAN
                           (Full titles of the plans)

                                 JAY R. LAMARCHE
              EXECUTIVE VICE PRESIDENT AND CHIEF FINANCIAL OFFICER
                           ARIAD PHARMACEUTICALS, INC.
                              26 LANDSDOWNE STREET
                       CAMBRIDGE, MASSACHUSETTS 02139-4234
                                 (617) 494-0400
    (Name, address, including zip code, and telephone number, including area
                           Code, of agent for service)

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

                         CALCULATION OF REGISTRATION FEE
===============================================================================================================
           Title of                 Amount to be         Proposed            Proposed             Amount of
 securities to be registered        registered(1)         maximum             maximum          registration fee
                                                      offering price         aggregate
                                                       per share(2)      offering price(2)

---------------------------------------------------------------------------------------------------------------
Common Stock,  $.01 par value        3,000,000            $5.28             $15,843,750             $4,802            
===============================================================================================================
(1)  The number of shares of common stock, par value $.01 per share ("Common
     Stock"), stated above consists of the aggregate number of additional shares
     not previously registered which may be sold upon the exercise of options
     which have been granted and/or may hereafter be granted under the ARIAD
     Pharmaceuticals, Inc. 1991 Stock Option Plan for Employees and Consultants,
     the ARIAD Pharmaceuticals, Inc. 1994 Stock Option Plan for Non-Employee
     Directors, and the ARIAD Pharmaceuticals, Inc. 1997 Stock Purchase Plan
     (the "Plans"). The maximum number of shares, which may be sold upon the
     exercise of such options granted under the Plans, is subject to adjustment
     in accordance with certain anti-dilution and other provisions of the Plans.
     Accordingly, pursuant to Rule 416 under the Securities Act of 1933, as
     amended (the "Securities Act"), this Registration Statement covers, in
     addition to the number of shares stated above, an indeterminate number of
     shares which may be subject to grant or otherwise issuable after the
     operation of any such anti-dilution and other provisions.

(2)  Pursuant to the provisions of Rule 457(h) under the Securities Act, the
     registration fee with respect to all 3,000,000 shares being registered
     hereunder, options for which have not yet been granted and the option price
     of which is therefore unknown, is calculated on the basis of the average of
     the high and low sale prices per share of the Common Stock on The Nasdaq
     Stock Market ("Nasdaq") as of a date (September 23, 1997) within 5 business
     days prior to filing this Registration Statement.

================================================================================
2

                                EXPLANATORY NOTE

         In accordance with the instructional Note to Part I of Form S-8 as
promulgated by the Securities and Exchange Commission, the information specified
by Part I of Form S-8 has been omitted from this Registration Statement on Form
S-8 for offers of Common Stock pursuant to the Plans.
3

                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

ITEM 3.  INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE.

         The following documents filed by the Company with the Commission
pursuant to the Exchange Act, are incorporated by reference in this Prospectus:
(a) the Company's Annual Report on Form 10-K for the year ended December 31,
1996; (b) the Company's Quarterly Reports on Form 10-Q for the quarterly periods
ended March 31, 1997 and June 30, 1997; (c) the Company's Proxy Statement for
its annual meeting of stockholders held on June 20, 1997 (other than the
portions thereof identified as not deemed filed with the Commission); and (d)
the description of the Common Stock which is contained in the Company's
registration statement on Form 10 filed with the Commission on June 25, 1993,
including all amendments and reports filed for the purpose of updating such
description. All documents filed by the Company with the Commission pursuant to
Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act after the date of this
Prospectus and prior to the termination of the offering made hereby shall be
deemed to be incorporated by reference in this Prospectus and to be a part
hereof from the date of filing of such documents. Any statement contained in a
document incorporated or deemed to be incorporated by reference shall be deemed
to be modified or superseded to the extent that a statement contained in any
subsequently filed document which also is or is deemed to be incorporated by
reference herein or therein modifies or supersedes such statement. Any statement
so modified or superseded shall not be deemed, except as so modified or
superseded, to constitute a part hereof.

ITEM 4. DESCRIPTION OF SECURITIES.

         Not applicable.

ITEM 5. INTERESTS OF NAMED EXPERTS AND COUNSEL.

         The validity of the issuance of the shares of Common Stock registered
under this Registration Statement has been passed upon for the Company by Mintz,
Levin, Cohn, Ferris, Glovsky and Popeo, P.C. of Boston, Massachusetts. Members
of Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C. own an aggregate of
approximately 201,700 shares of Common Stock of the Company.

ITEM 6. INDEMNIFICATION OF DIRECTORS AND OFFICERS.

         Section 145(a) of the General Corporation Law of the State of Delaware
provides that a Delaware corporation may indemnify any person who was or is a
party or is threatened to be made a party to any threatened, pending or
completed action, suit or proceeding, whether civil, criminal, administrative or
investigative (other than an action by or in the right of the corporation) by
reason of the fact that he is or was a director, officer, employee or agent of
the corporation or is or was serving at the request of the corporation as a
director, officer, employee or agent of another corporation or enterprise,
against expenses, judgments, fines and amounts paid in settlement actually and
reasonably incurred by him in connection with such action, suit or proceeding if
he acted in good faith and in a manner he reasonably believed to be in or not
opposed to the best interests of the corporation, and, with respect to 

                                      II-1
4

any criminal action or proceeding, had no cause to believe his conduct was
unlawful.

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

         Section 145 further provides that to the extent a director or officer
of a corporation has been successful in the defense of any action, suit or
proceeding referred to in subsections (a) and (b) or in the defense of any
claim, issue or matter therein, he shall be indemnified against expenses
actually and reasonably incurred by him in connection therewith; that
indemnification provided for by Section 145 shall not be deemed exclusive of any
other rights to which the indemnified party may be entitled; and that the
corporation may purchase and maintain insurance on behalf of a director or
officer of the corporation against any liability asserted against him or
incurred by him in any such capacity or arising out of his status as such
whether or not the corporation would have the power to indemnify him against
such liabilities under such Section 145.

         The Certificate of Incorporation, as amended, and By-laws of the
Company provide for indemnification of the Company's directors and officers to
the fullest extent permitted by law. The By-laws also permit the Board of
Directors to authorize the Company to purchase and maintain insurance against
any liability asserted against any director, officer, employee or agent of the
Company arising out of his capacity as such. Insofar as indemnification for
liabilities under the Securities Act may be permitted to directors, officers, or
controlling persons of the Company pursuant to the Company's Certificate of
Incorporation, as amended, its By-laws and the Delaware General Corporation Law,
the Company has been informed that in the opinion of the Commission such
indemnification is against public policy as expressed in such Act and is
therefore unenforceable.

         As permitted by the Delaware General Corporation Law, the Company's
Certificate of Incorporation, as amended, provides that directors of the Company
shall not be personally liable to the Company or its stockholders for monetary
damages for breach of fiduciary duty as a director, except for liability (i) for
any breach of the director's duty of loyalty to the Company or its stockholders,
(ii) for acts or omissions not in good faith or which involve intentional
misconduct or a knowing violation of law, (iii) under Section 174 of the
Delaware General Corporation Law, relating to prohibited dividends or
distributions or the repurchase or redemption of stock or (iv) for any
transaction from which the director derives an improper personal benefit. As a
result of this provision, the Company and its stockholders may be unable to
obtain monetary damages from a director for breach of his or her duty of care.

ITEM 7. EXEMPTION FROM REGISTRATION CLAIMED.

         Not applicable.

                                      II-2
5

ITEM 8. EXHIBITS.

  4.1             Form of Warrant Agreement (with Form of Warrant). (1)
  4.2             Rights Agreement, dated as of December 15, 1994, between the
                  Company and State Street Bank and Trust Company, which
                  includes the Certificate of Designations in respect of the
                  Series A Preferred Stock, as Exhibit A, the Form of Right
                  Certificate as Exhibit B and the Summary of Rights to Purchase
                  Series A Preferred Stock as Exhibit C. Pursuant to the Rights
                  Agreement, Right Certificates will not be mailed until after
                  the Separation Date (as defined therein). (2)
  4.3             Amendment, dated as of April 24, 1995, to Rights Agreement,
                  dated as of December 15, 1994, between ARIAD Pharmaceuticals,
                  Inc. and State Street Bank and Trust Company. (3)
  4.4             Stock Purchase Agreement, dated as of April 24, 1995, between
                  ARIAD Pharmaceuticals, Inc. and Biotech Target S.A. (4)
  5.1             Opinion of Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C.
                  as to the legality of shares being registered. (5)
  23.1            Consent of Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C.
                  (included in opinion of counsel filed as Exhibit 5.1). (5)
  23.2            Consent of Deloitte & Touche LLP. (5) 
  24.1            Power of Attorney

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

(1)     Incorporated by reference to registration statement on Form S-1 of the
        Company (No. 33-76414) filed with the Securities and Exchange Commission
        on March 11, 1994.

(2)     Incorporated by reference to Form 8-K of the Company filed with the
        Securities and Exchange Commission on December 21, 1994.

(3)     Incorporated by reference to Form 8-K of the Company filed with the
        Securities and Exchange Commission on May 15, 1995.

(4)     Incorporated by reference to Form 10-K of the Company for the fiscal
        year ended December 31, 1995 and filed with the Securities and Exchange
        Commission on March 15, 1996.

(5)     Filed herewith.

     ITEM 9.  UNDERTAKINGS.

     (a)  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 of 1933;

              (ii)  To reflect in the prospectus any facts or events arising
                    after the effective date of the 

                                      II-3
6

                    Registration Statement (or the most recent post-effective
                    amendment thereof) which, individually or in the aggregate,
                    represents 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.

              (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 paragraphs
                    (a)(1)(i) and (a)(1)(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
                    those paragraphs is contained in periodic reports filed by
                    the Registrant pursuant to Section 13 or Section 15(d) of
                    the Securities Exchange Act of 1934 that are incorporated by
                    reference in this Registration Statement.

       (2) That, for the purpose of determining any liability under the
           Securities Act of 1933, 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 bonafide offering thereof.

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

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

     (c)  Insofar as indemnification for liabilities arising under the
          Securities Act of 1933 may be permitted to directors, officers and
          controlling persons of the Registrant pursuant to the foregoing
          provisions, or otherwise, the Registrant has been advised that in the
          opinion of the Securities and Exchange Commission such indemnification
          is against public policy as expressed in the Act and is, therefore,
          unenforceable. In the event that a claim for indemnification against
          such liabilities (other than the payment by the Registrant 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 Act and will be
          governed by the final adjudication of such issue.

                                      II-4
7

                                   SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, the Registrant has
duly caused this registration statement to be signed on its behalf by the
undersigned, thereunto duly authorized, in the City of Cambridge and
Commonwealth of Massachusetts on the 26th of September, 1997.

                            ARIAD PHARMACEUTICALS, INC.

                            By: /s/ Jay R. LaMarche
                                ------------------------------------------------
                            Executive Vice President and Chief Financial Officer

                                      II-5
8

                                POWER OF ATTORNEY

    The registrant and each person whose signature appears below constitutes and
appoints Harvey J. Berger, M.D. and Jay R. LaMarche and each of them singly,
his, her or its true and lawful attorneys-in-fact and agents, with full power of
substitution and resubstitution, for him, her or it and in his, her or its name,
place and stead, in any and all capacities, to sign and file (i) any and all
amendments (including post-effective amendments) to this registration statement,
with all exhibits thereto, and other documents in connection therewith, and (ii)
a registration statement, and any and all amendments thereto, relating to the
offering covered hereby filed pursuant to Rule 462(b) under the Securities Act
of 1933, 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 or necessary to be done in
and about the premises, as fully to all intents and purposes as he, she, or 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 hereof.

          Pursuant to the requirements of the Securities Act of 1933, this
registration statement has been signed below by the following persons and in the
capacities indicated on the 26th of September, 1997.
Signature                                Title                          Date
         ---------                                -----                          ----
/s/ Harvey J. Berger           Chairman of the Board of Directors, President   September 26,1997
  ----------------------------   and Chief Executive Officer
  Harvey J. Berger, M.D.         
  
  /s/ Edgar Haber                Vice Chairman of the Board of Directors         September 26,1997
  ----------------------------
  Edgar Haber, M.D.

  /s/ Jay R. LaMarche            Executive Vice President, Chief Financial       September 26,1997
  ----------------------------   Officer, Treasurer and Director (Principal
  Jay R. LaMarche                Financial and Accounting Officer)

  /s/ Joan S. Brugge             Director                                        September 26,1997
  ----------------------------
  Joan S. Brugge, Ph.D.

  /s/ Vaughn D. Bryson           Director                                        September 26,1997
  ----------------------------
  Vaughn D. Bryson

  /s/ Philip Felig               Director                                        September 26,1997
  ----------------------------
  Philip Felig, M.D.

  /s/ John M. Deutch             Director                                        September 26,1997
  ----------------------------
  John M. Deutch, Ph.D.

  /s/ Peter T. Joseph            Director                                        September 26,1997
  ---------------------------- 
  Peter T. Joseph

  /s/ Joel S. Marcus             Director                                        September 26,1997
  ----------------------------
  Joel S. Marcus

  /s/ Sandford D. Smith          Director                                        September 26,1997
  ----------------------------
  Sandford D. Smith

  /s/ Raymond S. Troubh          Director                                        September 26,1997
  ---------------------------- 
  Raymond S. Troubh
II-6