UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                              WASHINGTON D.C. 20549


                                   FORM 8-A/A
                                (AMENDMENT NO. 3)

                FOR REGISTRATION OF CERTAIN CLASSES OF SECURITIES
                     PURSUANT TO SECTION 12(B) OR (G) OF THE
                         SECURITIES EXCHANGE ACT OF 1934

                         TRIANGLE PHARMACEUTICALS, INC.
             (Exact name of registrant as specified in its charter)

DELAWARE                                    56-1930728
(State of incorporation or organization)    (I.R.S. Employer Identification No.)

                    4 UNIVERSITY PLACE, 4611 UNIVERSITY DRIVE
                          DURHAM, NORTH CAROLINA 27707
              (Address of principal executive offices and zip code)

Securities to be registered pursuant to Section 12(b) of the Act:

     Title of class     Name of each exchange on which such class is registered
         NONE                                NONE

If this form relates to the registration of a class of securities pursuant to
Section 12(b) of the Exchange Act and is effective pursuant to General
Instruction A.(c), check the following box. |_|

If this form relates to the registration of a class of securities pursuant to
Section 12(g) of the Exchange Act and is effective pursuant to General
Instruction A.(d), check the following box. |X|

Securities Act registration statement file number to which this form relates
(if applicable):  N/A

Securities to be registered pursuant to Section 12(g) of the Act:

    Title of class       Name of each exchange on which such class is registered
   PREFERRED STOCK                 NASDAQ NATIONAL MARKET SYSTEM
   PURCHASE RIGHTS






                 INFORMATION REQUIRED IN REGISTRATION STATEMENT

ITEM 1.  DESCRIPTION OF REGISTRANT'S SECURITIES TO BE REGISTERED.

On February 10, 1999, Triangle Pharmaceuticals, Inc. (the "Company") filed with
the Securities and Exchange Commission a Registration Statement on Form 8-A to
register Rights issuable in accordance with the terms of the Rights Agreement
(the "Original Rights Agreement") dated as of February 1, 1999 between the
Company and American Stock Transfer & Trust Company, as Rights Agent (the
"Rights Agent"). All capitalized terms below and not defined herein have the
meanings given them in the Original Rights Agreement.

On June 2, 1999, the Company entered into a Collaboration Agreement (the
"Collaboration Agreement"), a Supply and Manufacturing Agreement (the "Prior
Manufacturing Agreement), a Co-Promotion Agreement (the "Co-Promotion
Agreement"), a Common Stock Purchase Agreement (the "Stock Purchase Agreement"),
and a Stockholder Rights Agreement (the "Stockholder Agreement," along with the
Collaboration Agreement, Prior Manufacturing Agreement, the Co-Promotion
Agreement and the Stock Purchase Agreement, collectively referred to herein as
the "Alliance Agreements") with Abbott Laboratories, an Illinois corporation
("Abbott").

In connection with the Alliance Agreements, the Board of Directors of the
Company approved an amendment to the Original Rights Agreement (the "First
Amendment") dated as of June 2, 1999 by and between the Company and the Rights
Agent. The First Amendment provided that, among other things, so long as Abbott
held less than certain defined levels of interest in Company stock during
specified time periods, neither Abbott nor its U.S. wholly-owned subsidiaries
will be deemed to be an Acquiring Person, that the Distribution Date will not be
deemed to occur and that the Rights will not separate from the Common Stock of
the Company as a result of entering into the Alliance Agreements or the
consummation of the transactions contemplated thereby.

On or about August 24, 2001, the Company entered into a Purchase Agreement (the
"Warburg Stock Purchase Agreement") with Warburg Pincus Private Equity VIII,
L.P. ("Warburg"), pursuant to which Warburg purchased certain shares of the
Company's Common Stock.

In connection with the Warburg Stock Purchase Agreement, the Board of Directors
of the Company approved an amendment to the Original Rights Agreement (the
"Second Amendment") dated as of August 24, 2001 by and between the Company and
the Rights Agent. The Second Amendment provided that up until such time as
Warburg, together with its Affiliates, becomes the Beneficial Owner of more than
the Permitted Percentage (as such term is defined in the Second Amendment),
Warburg will not be deemed to be an Acquiring Person, the Distribution Date will
not be deemed to occur, and the Rights will not separate from the Common Stock
of the Company as a result of entering into the Warburg Stock Purchase Agreement
or the consummation of the transactions contemplated thereby.

On July 29, 2002, in connection with the termination of certain of the Alliance
Agreements and the amendment of the Stockholder Agreement, the Board of
Directors of the Company approved

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an amendment to the Original Rights Agreement (the "Third Amendment") dated as
of July 30, 2002 (the Original Rights Agreement, as amended by the First
Amendment, the Second Amendment and the Third Amendment is referred to hereafter
as the "Rights Agreement"). The Third Amendment removed all references to Abbott
and its affiliates so that such companies are no longer excluded from the
definition of "Acquiring Person" under the Original Rights Agreement. The Third
Amendment also made other conforming changes to the Original Rights Agreement.

The description and terms of the Rights are set forth in the Rights Agreement.
The Rights Agreement and the related Certificate of Designations for the
Company's Series B Junior Participating Preferred Stock are each attached as an
exhibit to the Registration Statement on Form 8-A filed with the Securities and
Exchange Commission on February 10, 1999 and are each incorporated herein by
reference. The First Amendment is attached as an exhibit to the Registration
Statement on Form 8-A/A (Amendment No. 1) filed with the Securities and Exchange
Commission on June 18, 1999 and is incorporated herein by reference. The Second
Amendment is attached as Exhibit 4.1 to the Current Report on Form 8-K filed
with the Securities and Exchange Commission on August 24, 2001 and is
incorporated herein by reference. The Third Amendment is attached hereto as
Exhibit 1 and is incorporated herein by reference. The foregoing description of
the Rights and the Rights Agreement does not purport to be complete and is
qualified in its entirety by reference to such exhibits.

ITEM 2. EXHIBITS.

EXHIBIT NUMBER       DOCUMENT DESCRIPTION
--------------       ---------------------
1                    Amendment to Rights Agreement dated as of July 30, 2002 by
                     and between Triangle Pharmaceuticals, Inc. and American
                     Stock Transfer & Trust Company, as Rights Agent



              [THE REMAINDER OF THIS PAGE IS PURPOSELY LEFT BLANK]

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                                    SIGNATURE

Pursuant to the requirements of Section 12 of the Securities Exchange Act of
1934, the registrant has duly caused this registration statement to be signed on
its behalf by the undersigned, thereto duly authorized.

                                  TRIANGLE PHARMACEUTICALS, INC.


DATE: July 31, 2002               By:   /s/ CHRIS A. RALLIS
                                        --------------------------------------
                                        Name:  Chris A. Rallis
                                        Title: President and Chief Operating
                                               Officer


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                                  EXHIBIT INDEX

EXHIBIT NUMBER        DOCUMENT DESCRIPTION
--------------        --------------------
1                     Amendment to Rights Agreement dated as of July 30, 2002
                      by and between Triangle Pharmaceuticals, Inc. and American
                      Stock Transfer & Trust Company, as Rights Agent


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