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                                                                    EXHIBIT 10.3

                                 FIRST AMENDMENT
                                       TO
                         TRIANGLE PHARMACEUTICALS, INC.
                          STOCKHOLDER RIGHTS AGREEMENT

     This First Amendment (the "AMENDMENT") to the Triangle Pharmaceuticals,
Inc. Stockholder Rights Agreement (the "AGREEMENT") dated as of June 2, 1999, by
and between Triangle Pharmaceuticals, Inc., a Delaware corporation (the
"COMPANY"), and Abbott Laboratories, an Illinois corporation ("PURCHASER"), is
made and entered into as of the 30th day of July, 2002. Capitalized terms used
herein that are not otherwise defined herein shall have the meanings given them
in the Agreement.

                                    RECITALS

     WHEREAS, in connection with Purchaser's acquisition of certain shares of
Common Stock of the Company in June 1999, the Company and Purchaser entered into
the Agreement to provide Purchaser with certain rights related to the Common
Stock issued to Purchaser and certain other matters, as described therein;

     WHEREAS, the Company and Purchaser now desire to amend and supplement the
Agreement in the manner set forth below;

     WHEREAS, Section 8.1 of the Agreement provides that the Agreement may be
amended by a written agreement of the Company and Purchaser;

     NOW, THEREFORE, in consideration of the above and the mutual covenants
described below, the Company and Purchaser hereby agree to amend the Agreement
as follows:

     1.   Section 1.2 "COMPANY REGISTRATION" is hereby deleted and replaced in
its entirety as follows:

          Section 1.2 REGISTRABLE SECURITIES. "Registrable Securities" include
     such portion of the Shares which have not previously been registered or
     otherwise sold to the public.

     2.   Section 1.3 "UNDERWRITING" shall be deleted in its entirety.

     3.   Section 3.3 "RIGHT OF FIRST REFUSAL" is hereby deleted and replaced in
its entirety as follows:

     3.3  RIGHT OF FIRST REFUSAL.

          In the event Purchaser desires to transfer any or all of its
     Restricted Securities (i) in a private transaction or block sale to a buyer
     who is engaged in business in the pharmaceutical or biotechnology
     industries or, to the knowledge of Purchaser, is acting in concert with or
     on behalf of another party who is engaged in business in either of those

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     industries, (ii) to a buyer who, to the knowledge of Purchaser after
     reasonable inquiry, has filed publicly any notice or form with the SEC of
     its intent to hold or acquire the Company's securities with the purpose of
     changing or influencing control of the Company, which shall include seeking
     representation on the Company's Board of Directors, or (iii) in a block
     trade to a "qualified institutional buyer," as that term is defined in Rule
     144A promulgated under the Securities Act ("QIB"), who is not a buyer under
     (i) or (ii) and which block trade, when combined with the number of the
     Company's securities sold or otherwise transferred by Purchaser within the
     preceding ninety (90) days, exceeds 2.5% of the Company's then outstanding
     Common Stock, Purchaser must deliver a notice in writing to the Company
     ("Notice") by overnight mail stating (A) its bona fide intention to sell or
     transfer such securities, (B) the total number of such Restricted
     Securities to be sold or transferred (including Restricted Securities
     within the Section 5.1 volume limitations that constitute part of the
     proposed sale or transfer), (C) the price, if any, for which Purchaser
     proposes to sell or transfer such Restricted Securities, and (D) the name
     of the proposed purchaser or transferee (except for a Notice provided in
     connection with (iii) above, in which case no proposed buyer need be
     identified). In the event the proposed transfer is partially or completely
     in exchange for assets other than cash, then such assets shall be deemed to
     have a cash value in the amount determined by the Company's Board of
     Directors in its sole good faith opinion, in which case such cash value
     ascertained by the Board, when added to any cash to be exchanged and then
     divided by the number of Restricted Securities to be transferred, shall be
     deemed the price per security set forth in the Notice.

          The Company shall then have an exclusive, irrevocable option (the
     "Company Option"), at any time within ten (10) business days of receipt of
     the Notice, to purchase some or all of the Restricted Securities to which
     the Notice refers at the price per security specified in the Notice (as
     determined above). The Company shall exercise the Company Option by written
     notice signed by an officer of the Company and delivered or mailed to the
     Purchaser (the "Company Settlement Notice"), which notice shall specify the
     time, place and date for settlement of such purchase, such date to be not
     more than three (3) business days after the date of the Company Settlement
     Notice.

          On or before the third business day after the date of the Company
     Settlement Notice, the Purchaser must deliver to the Company all
     certificates or other related documentation for the securities being
     acquired by the Company which are not already in the Company's custody,
     together with proper assignments in blank of the Restricted Securities with
     signatures properly guaranteed and with such other documents as may be
     required by the Company to provide reasonable assurance that each necessary
     endorsement is genuine and effective, and the Company must thereupon
     deliver to the Purchaser full cash payment for the Restricted Securities
     being acquired, provided that if the terms of payment set forth in the
     Notice were other than cash against delivery, the Company shall pay for
     said securities as described in the Notice. In the event that Company
     notifies Purchaser that it is not interested in the purchase of the
     Restricted Securities or fails to give Purchaser timely notice of its
     interest, Purchaser shall be free to sell or transfer the Restricted
     Securities to any third party, subject to the restrictions in this
     Agreement. Notwithstanding the foregoing, in the event that the Company
     notifies

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     Purchaser that it is not interested in the purchase of Restricted
     Securities subject to a Notice provided in connection with a block trade to
     a QIB under (iii) above or fails to give Purchaser timely notice of its
     interest in such Restricted Securities, Purchaser then shall have sixty
     (60) days to sell the Restricted Securities in a block trade for not less
     than the price specified in the Notice. Any Restricted Securities included
     in the Notice and remaining unsold at the end of such sixty (60) day period
     may not be sold in a block trade to a QIB unless and until such time as
     Purchaser complies again with this section with regard to such further
     sales of such Restricted Securities. The Company may at any time freely
     assign the Company Option to any third party.

     4.   Section 3.4 "MARKET STAND-OFF AGREEMENT" shall be deleted in its
entirety.

     5.   Section 4 "ADDITIONAL PURCHASE RIGHTS" shall be deleted in its
entirety.

     6.   Section 5.1 "TRANSFER RESTRICTION" is hereby deleted and replaced in
its entirety as follows:

          5.1  TRANSFER RESTRICTION.

          (a)  Purchaser hereby agrees that neither it nor any Affiliate shall,
     directly or indirectly sell, offer to sell, contract to sell (including,
     without limitation, any short sale), grant any option to purchase or
     otherwise transfer or dispose of any of the Restricted Securities on the
     open market without the prior written consent of the Company at any time
     when the number of shares of such Restricted Securities to be offered, sold
     or otherwise transferred as described above, combined with the number of
     the Company's securities sold or otherwise transferred by Purchaser within
     the preceding ninety (90) days, exceeds 2.5% of the total number of shares
     of the Common Stock of the Company then outstanding.

          (b)  Purchaser hereby agrees that neither it nor any Affiliate shall,
     directly or indirectly sell, offer to sell, contract to sell (including,
     without limitation, any short sale), grant any option to purchase or
     otherwise transfer or dispose of any of the Restricted Securities in a
     private transaction without the prior written consent of the Company at any
     time when the number of shares of such Restricted Securities to be offered,
     sold or otherwise transferred as described above, combined with the number
     of the Company's securities sold or otherwise transferred by Purchaser
     within the preceding ninety (90) days, exceeds 2.5% of the total number of
     shares of the Common Stock of the Company then outstanding, provided that
     this limitation shall not apply to private transactions in which the buyer
     is a QIB.

          (c)  Purchaser hereby agrees that neither it nor any Affiliate shall,
     directly or indirectly sell, offer to sell, contract to sell (including,
     without limitation, any short sale), grant any option to purchase or
     otherwise transfer or dispose of any of the Restricted Securities in a
     block trade without the prior written consent of the Company at any time
     when the number of shares of such Restricted Securities to be offered, sold
     or otherwise transferred as described above, combined with the number of
     the Company's securities

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     sold or otherwise transferred by Purchaser within the preceding ninety (90)
     days, exceeds 2.5% of the total number of shares of the Common Stock of the
     Company then outstanding, provided that this limitation shall not apply to
     block trades in which the buyer is a QIB.

          (d)  For purposes of subsections (a), (b) and (c) above, in computing
     the percentage of the Company's outstanding securities that Purchaser may
     transfer, all sales and other transfers by Purchaser during that period
     shall be taken into account, whether made pursuant to subsections (a), (b),
     (c) or otherwise. For the avoidance of doubt, if sales are proposed to
     occur under more than one of the foregoing subsections (or an exception to
     one of such subsections) at the same time, all of such proposed sales must
     be included in the calculation of the percentage of the Company's
     outstanding stock represented by such sales together with all other sales
     in the preceding ninety (90) days.

          (e)  In order to enforce the foregoing covenant, the Company may
     impose legends and/or stop-transfer instructions with respect to the
     Restricted Securities held by Purchaser (and the Restricted Securities of
     every other person subject to the foregoing restriction). Upon the written
     request of Purchaser prior to taking any action that would exceed the
     limits described above, the Company in its sole discretion may consent in
     writing to waive this covenant with respect to proposed transactions
     described in the request, provided that the Company shall continue to have
     a right of first refusal as provided in Section 3.3 hereof, if applicable,
     with regard to any transactions covered by such request. This right of
     first refusal shall apply to all shares of Restricted Securities covered by
     such request, even if some of such shares are within the volume limitations
     described in this section. The Company's consent to waive the restrictions
     of this covenant with regard to a particular transaction shall not
     constitute a waiver of this covenant with regard to any other transaction
     or proposed transaction.

     7.   Subsection (a) of Section 5.2 "STANDSTILL PROVISIONS" shall be deleted
and replaced in its entirety as follows:

          (a)  Commencing as of the Effective Date and through June 30, 2005
     (the "Standstill Period"), Purchaser (including all Affiliates) shall not
     acquire "Beneficial Ownership" (as hereinafter defined) of any additional
     shares of Common Stock of the Company, any securities convertible into or
     exchangeable for Common Stock, or any other right to acquire Common Stock
     except by way of stock dividends or other distributions or offerings made
     available to holders of Common Stock generally, from the Company or any
     other person or entity, if after giving effect to such acquisition of
     additional shares, the total Beneficial Ownership of Purchaser (together
     with all of its Affiliates) shall be fifteen percent (15%) or greater (the
     "Beneficial Ownership Limitation") of the Company's total Common Stock from
     time to time outstanding without the prior written consent of the Company,
     which consent may be withheld in its sole discretion; PROVIDED, HOWEVER,
     that in no event shall the Company's sale or issuance to Purchaser of
     Restricted Securities constitute a violation of this Section 5.2.

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     8.   Subsection (c) of Section 5.4 "DEFINITIONS" shall be amended by adding
the following proviso at the end: "; provided, however, that "Restricted
Securities" as used in Sections 3.3 and 5.1 herein shall mean all securities of
the Company, of any type or designation."

     9.   Section 6.2 "CONTINUING RIGHTS" shall be deleted in its entirety, and
Purchaser agrees that the Purchaser Representative currently serving on the
Company's Board of Directors shall resign upon execution of this Agreement, such
resignation to take effect immediately.

     10.  Section 7.1 "RIGHTS AGREEMENT" shall be deleted in its entirety.

     11.  Section 8.6 "NOTICES" shall be amended to read as follows in respect
of the Company:

          If to the Company:

                  Triangle Pharmaceuticals, Inc.
                  4 University Place
                  4611 University Drive
                  Durham, North Carolina 27707
                  Telephone: 919-493-5980
                  Facsimile: 919-493-5925
                  Attention: Chief Operating Officer
                             General Counsel

          Copy to:

                  Smith, Anderson, Blount, Dorsett, Mitchell & Jernigan, LLP
                  2500 First Union Capitol Center
                  Raleigh, North Carolina 27601
                  Telephone: 919-821-1220
                  Facsimile: 919-821-6800
                  Attention: Gerald F. Roach, Esq.

     12.  The first paragraph of Exhibit B shall be amended by adding the
following clause at the end of the last sentence of that paragraph: "or (iii) in
connection with a private placement by Purchaser made in compliance with all
applicable rules and regulations of the SEC currently in effect."

     13.  Except as specifically amended by this Amendment, the terms and
conditions of the Agreement shall remain unimpaired, unaffected, and unchanged
in every particular as set forth in the Agreement.

     13.  This Amendment may be executed in counterparts, each of which shall be
deemed an original, but all such counterparts shall together constitute one and
the same instrument. Any counterpart hereof may be delivered via telecopier,
such counterpart to have the same effect as an original counterpart hereof.

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     14.  This Agreement shall be governed in all respects by and construed in
accordance with the substantive of the State of Delaware without regard to
conflicts of laws principles.

                                    * * * * *

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       [SIGNATURE PAGE TO FIRST AMENDMENT TO STOCKHOLDER RIGHTS AGREEMENT]

     IN WITNESS WHEREOF, the Company and Purchaser have caused this Amendment to
be executed as of the date first above written by their duly authorized
representatives.


                               TRIANGLE PHARMACEUTICALS, INC.


                               By:  /s/  Chris A. Rallis
                                  ----------------------------------------------
                                  Name:  Chris A. Rallis
                                  Title: President & Chief Operating Officer


                               ABBOTT LABORATORIES


                               By:  /s/ Jeffrey M. Leiden
                                  ---------------------------------------------
                                  Name:  Jeffrey M. Leiden, MD, Ph.D.
                                  Title: President & Chief Operating Officer
                                         Pharmaceutical Products Group

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