<Page>

                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                    FORM 10-Q

/X/              QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d)
                     OF THE SECURITIES EXCHANGE ACT OF 1934

                For the quarterly period ended September 30, 2002

                                       OR

            TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 (d) OF THE
                         SECURITIES EXCHANGE ACT OF 1934

             For the transition period from _________ to _________.

                        Commission File Number: 000-21589

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

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

        4 University Place
        4611 University Drive
        Durham, North Carolina                             27707
 (Address of principal executive offices)                (zip code)

       Registrant's telephone number, including area code: (919) 493-5980

     Indicate by check mark whether the registrant (1) has filed all reports
required to be filed by Section 13 or 15(d) of the Securities Exchange Act of
1934 during the preceding 12 months (or for such shorter period that the
registrant was required to file such reports), and (2) has been subject to such
filing requirements for the past 90 days. Yes /X/ No / /

     Indicate by check mark whether the registrant is an accelerated filer (as
defined in Rule 12b-2 of the Securities Exchange Act of 1934.) Yes /X/  No / /

     As of September 30, 2002, there were 76,903,883 shares of Triangle
Pharmaceuticals, Inc. Common Stock outstanding.

<Page>

                         TRIANGLE PHARMACEUTICALS, INC.

                                TABLE OF CONTENTS

<Table>
<Caption>
                                                                                                      Page No.
                                                                                                      --------
<S>                                                                                                    <C>
Part I.  Financial Information

         Item 1. Financial Statements

                 Condensed Consolidated Balance Sheets -
                   September 30, 2002 (unaudited) and December 31, 2001....................................3

                 Condensed Consolidated Statements of Operations (unaudited) -
                   Three and Nine Months Ended September 30, 2002 and September 30, 2001
                   and Period From Inception (July 12, 1995) Through September 30, 2002....................4

                 Condensed Consolidated Statements of Cash Flows (unaudited) -
                   Nine Months Ended September 30, 2002 and September 30, 2001 and
                   Period From Inception (July 12, 1995) Through September 30, 2002........................5

                 Condensed Consolidated Statements of Stockholders' Equity -
                   Period From Inception (July 12, 1995) Through
                   September 30, 2002 (unaudited)........................................................6-7

                 Notes to Condensed Consolidated Financial Statements (unaudited).......................8-10

         Item 2. Management's Discussion and Analysis of Financial
                   Condition and Results of Operations.................................................11-28

         Item 3. Quantitative and Qualitative Disclosures About Market Risk...............................29

         Item 4. Controls and Procedures..................................................................30

Part II. Other Information

         Item 1. Legal Proceedings........................................................................31

         Item 4. Submission of Matters to a Vote of Security Holders......................................31

         Item 6. Exhibits and Reports on Form 8-K.........................................................32

         Signatures.......................................................................................33

         Certifications................................................................................34-35
</Table>

                                        2
<Page>

                         PART I - FINANCIAL INFORMATION

ITEM 1. FINANCIAL STATEMENTS

                         TRIANGLE PHARMACEUTICALS, INC.
                          (A DEVELOPMENT STAGE COMPANY)
                      CONDENSED CONSOLIDATED BALANCE SHEETS
                    (IN THOUSANDS, EXCEPT PER SHARE AMOUNTS)

<Table>
<Caption>
                                                                            SEPTEMBER 30,       DECEMBER 31,
                                                                                2002                2001
                                                                            -------------       ------------
                                                                             (UNAUDITED)
<S>                                                                         <C>                 <C>
ASSETS

Current assets:
     Cash and cash equivalents ......................................       $      36,696       $     64,994
     Investments ....................................................              25,614             21,280
     Interest and other receivables .................................                 537              1,278
     Prepaid expenses ...............................................                 389                641
                                                                            -------------       ------------
        Total current assets ........................................              63,236             88,193
Property, plant and equipment, net ..................................               3,139              4,091
Investments .........................................................               5,960             21,881
                                                                            -------------       ------------

        Total assets ................................................       $      72,335       $    114,165
                                                                            =============       ============

LIABILITIES AND STOCKHOLDERS' EQUITY

Current liabilities:
     Accounts payable ...............................................       $       6,621       $     14,529
     Debt-current ...................................................               1,352              1,454
     Accrued expenses ...............................................              15,244             13,923
     Deferred revenue ...............................................                  --              4,139
                                                                            -------------       ------------
        Total current liabilities ...................................              23,217             34,045
Debt-noncurrent .....................................................                 778              1,680
Deferred revenue ....................................................               2,000             14,487
                                                                            -------------       ------------
        Total liabilities ...........................................              25,995             50,212
                                                                            -------------       ------------
Commitments and contingencies (See notes 4, 5 and 6) ................                  --                 --
Stockholders' equity:
     Convertible Preferred Stock, $0.001 par value; 10,000 shares
        authorized; 0 shares issued and outstanding .................                  --                 --
     Common Stock, $0.001 par value; 175,000 shares authorized;
        76,904 and 76,829 shares issued and outstanding, respectively                  77                 77
     Additional paid-in capital .....................................             470,807            470,478
     Accumulated deficit during development stage ...................            (424,670)          (406,895)
     Accumulated other comprehensive income .........................                 126                293
                                                                            -------------       ------------
        Total stockholders' equity ..................................              46,340             63,953
                                                                            -------------       ------------

        Total liabilities and stockholders' equity ..................       $      72,335       $    114,165
                                                                            =============       ============
</Table>

   The accompanying notes are an integral part of these condensed consolidated
                              financial statements.

                                        3
<Page>

                         TRIANGLE PHARMACEUTICALS, INC.
                          (A DEVELOPMENT STAGE COMPANY)
                 CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS
                                   (UNAUDITED)
                    (IN THOUSANDS, EXCEPT PER SHARE AMOUNTS)

<Table>
<Caption>
                                                                                                                     PERIOD FROM
                                                                                                                      INCEPTION
                                        THREE MONTHS ENDED SEPTEMBER 30,        NINE MONTHS ENDED SEPTEMBER 30,    (JULY 12, 1995)
                                        --------------------------------        -------------------------------       THROUGH
                                           2002                2001                2002                2001       SEPTEMBER 30, 2002
                                         ---------           ---------           ---------           ---------    ------------------
<S>                                      <C>                 <C>                 <C>                 <C>              <C>
Revenue:
  Collaborative revenue ..............   $  14,556           $   1,271           $  16,625           $   4,760        $  29,714

Operating expenses:
  License fees .......................       1,582                 500               1,800               2,453           28,363
  Development ........................      12,168              15,477              38,939              58,115          379,563
  Purchased research and development..          --                 320                  --                 320           18,178
  Selling, general and administrative        2,328               1,602               5,342               6,561           62,745
  Restructuring ......................          --               2,342                  --               2,342            2,342
                                         ---------           ---------           ---------           ---------        ---------
    Total operating expenses .........      16,078              20,241              46,081              69,791          491,191
                                         ---------           ---------           ---------           ---------        ---------
Loss from operations .................      (1,522)            (18,970)            (29,456)            (65,031)        (461,477)
Gain (loss) on investments, net ......          11                   9                  16                  76           (1,344)
Interest income, net .................         456                 764               1,665               2,737           28,151
Other income .........................          --                  --              10,000                  --           10,000
                                         ---------           ---------           ---------           ---------        ---------

Net loss .............................   $  (1,055)          $ (18,197)          $ (17,775)          $ (62,218)       $(424,670)
                                         =========           =========           =========           =========        =========

Basic and diluted net loss per common
  share ..............................   $   (0.01)          $   (0.35)          $   (0.23)          $   (1.32)
                                         =========           =========           =========           =========
Shares used in computing basic and
  diluted net loss per common share...      76,876              52,366              76,856              47,036
                                         =========           =========           =========           =========
</Table>

   The accompanying notes are an integral part of these condensed consolidated
                              financial statements.

                                        4
<Page>

                         TRIANGLE PHARMACEUTICALS, INC.
                          (A DEVELOPMENT STAGE COMPANY)
                 CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS
                                   (UNAUDITED)
                                 (IN THOUSANDS)

<Table>
<Caption>
                                                                                                        PERIOD FROM
                                                                                                         INCEPTION
                                                                  NINE MONTHS ENDED SEPTEMBER 30,     (JULY 12, 1995)
                                                                  -------------------------------         THROUGH
                                                                      2002              2001         SEPTEMBER 30, 2002
                                                                    ---------         ---------      ------------------
<S>                                                                 <C>               <C>                <C>
Cash flows from operating activities:
Net loss ...................................................        $ (17,775)        $ (62,218)         $(424,670)
Adjustments to reconcile net loss to net
  cash used by operating activities:
  Depreciation and amortization ............................            1,110             1,467              7,437
  (Gain) loss from disposal of property, plant and equipment              (10)              260                154
  (Gain) loss on investments ...............................              (16)              (76)             1,344
  Purchased research and development .......................               --               320             18,178
  Stock-based compensation .................................               80               183              2,150
  Change in assets and liabilities:
    Receivables ............................................              741               792               (537)
    Prepaid expenses .......................................              252              (124)              (389)
    Accounts payable .......................................           (7,908)           (3,453)             6,621
    Accrued expenses .......................................            1,321             3,650             15,244
    Deferred revenue .......................................          (16,626)           (4,760)             2,000
                                                                    ---------         ---------          ---------
Net cash used by operating activities ......................          (38,831)          (63,959)          (372,468)
                                                                    ---------         ---------          ---------
Cash flows from investing activities:
  Purchase of investments ..................................          (11,992)          (19,184)          (358,262)
  Proceeds from sale and maturity of investments ...........           23,428            39,186            325,470
  Proceeds from sale of property, plant and equipment ......               77                 7                751
  Purchase of property, plant and equipment ................             (225)             (456)           (11,304)
  Acquisition of Avid Corporation, net of cash acquired ....               --                --             (3,053)
                                                                    ---------         ---------          ---------
Net cash provided (used) by investing activities ...........           11,288            19,553            (46,398)
                                                                    ---------         ---------          ---------
Cash flows from financing activities:
  Sale of stock, net of related issuance costs .............              147            78,557            452,307
  Sale of options under salary investment option
    grant program ..........................................               75                57                457
  Proceeds from stock options/warrants exercised ...........               27               288                934
  Proceeds from notes payable ..............................               --                --              3,793
  Proceeds from equipment financing ........................              169                --                523
  Principal payments on capital lease obligations
    and notes payable ......................................           (1,173)               (7)            (2,452)
                                                                    ---------         ---------          ---------
Net cash (used) provided by financing activities ...........             (755)           78,895            455,562
                                                                    ---------         ---------          ---------
Net (decrease) increase in cash and cash equivalents .......          (28,298)           34,489             36,696
Cash and cash equivalents at beginning of period ...........           64,994            14,055                 --
                                                                    ---------         ---------          ---------
Cash and cash equivalents at end of period .................        $  36,696         $  48,544          $  36,696
                                                                    =========         =========          =========
</Table>


   The accompanying notes are an integral part of these condensed consolidated
                              financial statements.

                                        5
<Page>

                         TRIANGLE PHARMACEUTICALS, INC.
                          (A DEVELOPMENT STAGE COMPANY)
            CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY
                                 (IN THOUSANDS)

<Table>
<Caption>
                                         CONVERTIBLE
                                        PREFERRED STOCK                         COMMON STOCK        ADDITIONAL
                                     ----------------------                 ---------------------    PAID-IN    ACCUMULATED
                                      SHARES       AMOUNT      WARRANTS      SHARES       AMOUNT     CAPITAL      DEFICIT
                                     ---------    ---------    ---------    ---------   ---------   ----------   ----------
<S>                                     <C>       <C>          <C>             <C>      <C>         <C>          <C>
Initial sale of stock ............         933    $       1    $      --        1,175   $       1   $     710    $       --
Additional sale of stock .........       4,249            4           --        1,495           2       3,137            --
Stock-based compensation .........          --           --           --           --          --          12            --
Comprehensive loss:
  Net loss .......................          --           --           --           --          --          --          (967)
                                     ---------    ---------    ---------    ---------   ---------   ---------    ----------
Balance, December 31, 1995 .......       5,182            5           --        2,670           3       3,859          (967)
Sale of stock ....................       3,756            4           --        4,943           5      59,506            --
Stock-based compensation .........          --           --          152          700           1       1,127            --
Stock options exercised ..........          --           --           --          317          --          57            --
Conversion of Preferred to
  Common Stock ...................      (8,938)          (9)          --        8,938           9          --            --
Comprehensive loss:
  Net loss .......................          --           --           --           --          --          --       (10,917)
                                     ---------    ---------    ---------    ---------   ---------   ---------    ----------
Balance, December 31, 1996 .......          --           --          152       17,568          18      64,549       (11,884)
Sale of stock ....................          --           --           --        2,014           2      29,521            --
Acquisition of Avid Corp. ........          --           --           --          400          --       8,117            --
Sale of stock options ............          --           --           --           --          --          70            --
Stock-based compensation .........          --           --          (38)          --          --          --            --
Stock options exercised ..........          --           --           --           13          --           3            --
Comprehensive loss:
  Net loss .......................          --           --           --           --          --          --       (37,668)
                                     ---------    ---------    ---------    ---------   ---------   ---------    ----------
Balance, December 31, 1997 .......          --           --          114       19,995          20     102,260       (49,552)
Sale of stock ....................         170           --           --        8,868           9     116,325            --
Sale of stock options ............          --           --           --           --          --          97            --
Stock-based compensation .........          --           --           --           --          --          --            --
Stock options exercised ..........          --           --           --            8          --           1            --
Comprehensive loss:
  Change in unrealized
   gains/(losses) on investments..          --           --           --           --          --          --            --
  Net loss .......................          --           --           --           --          --          --       (67,271)
                                     ---------    ---------    ---------    ---------   ---------   ---------    ----------
Balance, December 31, 1998 .......         170           --          114       28,871          29     218,683      (116,823)
Sale of stock ....................          --           --           --        6,605           7     116,211            --
Sale of stock options ............          --           --           --           --          --          95            --
Stock-based compensation .........          --           --           --            6          --         101            --
Stock options/warrants exercised..          --           --         (114)         296          --         479            --
Conversion of Preferred to
  Common Stock ...................        (170)          --           --        1,700           2          (2)           --
Purchased in-process research and
  development costs ..............          --           --           --          100          --       1,247            --
Comprehensive loss:
  Reclassification adjustment for
   gains/(losses) in net loss ....          --           --           --           --          --          --            --
  Change in unrealized
   gains/(losses) on investments..          --           --           --           --          --          --            --
  Net loss .......................          --           --           --           --          --          --      (104,621)
                                     ---------    ---------    ---------    ---------   ---------   ---------    ----------
Balance, December 31, 1999 .......          --    $      --    $      --       37,578   $      38   $ 336,814    $ (221,444)
(CONTINUED)
<Caption>
                                                    ACCUMULATED
                                     COMPREHENSIVE     OTHER
                                        INCOME      COMPREHENSIVE    DEFERRED
                                        (LOSS)      INCOME/(LOSS)  COMPENSATION    TOTAL
                                     -------------  -------------  ------------  ---------
<S>                                  <C>            <C>            <C>           <C>
Initial sale of stock ............   $              $          --  $         --  $     712
Additional sale of stock .........                             --            --      3,143
Stock-based compensation .........                             --           (12)        --
Comprehensive loss:
  Net loss .......................            (967)            --            --       (967)
                                     -------------  -------------  ------------  ---------
Balance, December 31, 1995 .......            (967)            --           (12)     2,888
Sale of stock ....................                             --            --     59,515
Stock-based compensation .........                             --          (141)     1,139
Stock options exercised ..........                             --           (26)        31
Conversion of Preferred to
  Common Stock ...................                             --            --         --
Comprehensive loss:
  Net loss .......................         (10,917)            --            --    (10,917)
                                     -------------  -------------  ------------  ---------
Balance, December 31, 1996 .......         (10,917)            --          (179)    52,656
Sale of stock ....................                             --            --     29,523
Acquisition of Avid Corp. ........                             --            --      8,117
Sale of stock options ............                             --            --         70
Stock-based compensation .........                             --            48         10
Stock options exercised ..........                             --             6          9
Comprehensive loss:
  Net loss .......................         (37,668)            --            --    (37,668)
                                     -------------  -------------  ------------  ---------
Balance, December 31, 1997 .......         (37,668)            --          (125)    52,717
Sale of stock ....................                             --            --    116,334
Sale of stock options ............                             --            --         97
Stock-based compensation .........                             --            48         48
Stock options exercised ..........                             --             7          8
Comprehensive loss:
  Change in unrealized
   gains/(losses) on investments..              18             18            --         18
  Net loss .......................         (67,271)            --            --    (67,271)
                                     -------------  -------------  ------------  ---------
Balance, December 31, 1998 .......         (67,253)            18           (70)   101,951
Sale of stock ....................                             --            --    116,218
Sale of stock options ............                             --            --         95
Stock-based compensation .........                             --            58        159
Stock options/warrants exercised..                             --            12        377
Conversion of Preferred to
  Common Stock ...................                             --            --         --
Purchased in-process research and
  development costs ..............                             --            --      1,247
Comprehensive loss:
  Reclassification  adjustment for
   gains/(losses) in net loss ....             (21)           (21)           --        (21)
  Change in unrealized
   gains/(losses) on investments..            (132)          (132)           --       (132)
  Net loss .......................        (104,621)            --            --   (104,621)
                                     -------------  -------------  ------------  ---------
Balance, December 31, 1999 .......   $    (104,774) $        (135) $         --  $ 115,273
(CONTINUED)
</Table>

                                        6
<Page>

                         TRIANGLE PHARMACEUTICALS, INC.
                          (A DEVELOPMENT STAGE COMPANY)
            CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY
                                 (IN THOUSANDS)

<Table>
<Caption>
                                          CONVERTIBLE
                                        PREFERRED STOCK                         COMMON STOCK       ADDITIONAL
                                     ----------------------                 ---------------------    PAID-IN     ACCUMULATED
                                      SHARES       AMOUNT      WARRANTS      SHARES      AMOUNT     CAPITAL        DEFICIT
                                     ---------    ---------    ---------    ---------   ---------  ----------    -----------
<S>                                       <C>     <C>          <C>             <C>      <C>         <C>          <C>
(CONTINUED)
Sale of stock ....................          --    $      --    $      --          326   $       1   $   1,608    $       --
Sale of stock options ............          --           --           --           --          --          52            --
Stock-based compensation .........          --           --           --           --          --         348            --
Stock options/warrants exercised..          --           --           --          225          --         378            --
Purchased in-process research and
  development costs ..............          --           --           --          400          --       5,350            --
Comprehensive loss:
  Reclassification  adjustment for
   gains/(losses) in net loss ....          --           --           --           --          --          --            --
  Change in unrealized
   gains/(losses) on investments..          --           --           --           --          --          --            --
  Net loss .......................          --           --           --           --          --          --      (109,525)
                                     ---------    ---------    ---------    ---------   ---------   ---------    ----------
Balance, December 31, 2000 .......          --           --           --       38,529          39     344,550      (330,969)
Sale of stock ....................         200           --           --       36,058          36     125,070            --
Sale of stock options ............          --           --           --           --          --          68            --
Stock-based compensation .........          --           --           --           --          --         183            --
Stock options/warrants exercised..          --           --           --          142          --         289            --
Purchased in-process research and
  development costs ..............          --           --           --          100          --         320            --
Conversion of Preferred to
  Common Stock ...................        (200)          --           --        2,000           2          (2)           --
Comprehensive loss:
  Reclassification  adjustment for
   gains/(losses) in net loss ....          --           --           --           --          --          --            --
  Change in unrealized
   gains/(losses) on investments..          --           --           --           --          --          --            --
  Net loss .......................          --           --           --           --          --          --       (75,926)
                                     ---------    ---------    ---------    ---------   ---------   ---------    ----------
Balance, December 31, 2001 .......          --           --           --       76,829          77     470,478      (406,895)
(UNAUDITED)
Sale of stock ....................          --           --           --           54          --         147            --
Sale of stock options ............          --           --           --           --          --          75            --
Stock-based compensation .........          --           --           --           --          --          80            --
Stock options/warrants exercised..          --           --           --           21          --          27            --
Comprehensive loss:
  Reclassification  adjustment for
   gains/(losses) in net loss ....          --           --           --           --          --          --            --
  Change in unrealized
   gains/(losses) on investments..          --           --           --           --          --          --            --
  Net loss .......................          --           --           --           --          --          --       (17,775)
                                     ---------    ---------    ---------    ---------   ---------   ---------    ----------
Balance, September 30, 2002.......          --    $      --    $      --       76,904   $      77   $ 470,807    $ (424,670)
                                     =========    =========    =========    =========   =========   =========    ==========

<Caption>
                                                    ACCUMULATED
                                     COMPREHENSIVE     OTHER
                                        INCOME      COMPREHENSIVE    DEFERRED
                                        (LOSS)      INCOME/(LOSS)  COMPENSATION    TOTAL
                                     -------------  -------------  ------------  ---------
<S>                                  <C>            <C>            <C>           <C>
(CONTINUED)
Sale of stock ....................   $              $          --  $         --  $   1,609
Sale of stock options ............                             --            --         52
Stock-based compensation .........                             --            --        348
Stock options/warrants exercised..                             --            --        378
Purchased in-process research and
  development costs ..............                             --            --      5,350
Comprehensive loss:
  Reclassification  adjustment for
   gains/(losses) in net loss ....             133            133            --        133
  Change in unrealized
   gains/(losses) on investments..             163            163            --        163
  Net loss .......................        (109,525)            --            --   (109,525)
                                     -------------  -------------  ------------  ---------
Balance, December 31, 2000 .......        (109,229)           161            --     13,781
Sale of stock ....................                             --            --    125,106
Sale of stock options ............                             --            --         68
Stock-based compensation .........                             --            --        183
Stock options/warrants exercised..                             --            --        289
Purchased in-process research and
  development costs ..............                             --            --        320
Conversion of Preferred to
  Common Stock ...................                             --            --         --
Comprehensive loss:
  Reclassification  adjustment for
   gains/(losses) in net loss ....             (57)           (57)           --        (57)
  Change in unrealized
   gains/(losses) on investments..             189            189            --        189
  Net loss .......................         (75,926)            --            --    (75,926)
                                     -------------  -------------  ------------  ---------
Balance, December 31, 2001 .......         (75,794)           293            --     63,953
(UNAUDITED)
Sale of stock ....................                             --            --        147
Sale of stock options ............                             --            --         75
Stock-based compensation .........                             --            --         80
Stock options/warrants exercised..                             --            --         27
Comprehensive loss:
  Reclassification  adjustment for
   gains/(losses) in net loss ....            (172)          (172)           --       (172)
  Change in unrealized
   gains/(losses) on investments..               5              5            --          5
  Net loss .......................         (17,775)            --            --    (17,775)
                                     -------------  -------------  ------------  ---------
Balance, September 30, 2002.......   $     (17,942) $         126  $         --  $  46,340
                                     =============  =============  ============  =========
</Table>


   The accompanying notes are an integral part of these condensed consolidated
                              financial statements.

                                        7
<Page>

                         TRIANGLE PHARMACEUTICALS, INC.
                          (A DEVELOPMENT STAGE COMPANY)
              NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS
                                   (UNAUDITED)
                    (IN THOUSANDS, EXCEPT PER SHARE AMOUNTS)

1.   BASIS OF PRESENTATION

The accompanying unaudited condensed consolidated financial statements of
Triangle Pharmaceuticals, Inc. and its wholly-owned subsidiaries (the "Company"
or "Triangle") have been prepared in accordance with generally accepted
accounting principles and applicable Securities and Exchange Commission
regulations for interim financial information. Triangle is a development stage
company and has incurred losses and negative cash flows from operations since
its inception. The Company has sufficient liquidity to continue its planned
operations through the second quarter of 2003. Continuation of its operations
beyond that date will require the Company to raise additional capital through
equity or debt financings or from other sources. These financial statements do
not include all of the information and footnotes required by generally accepted
accounting principles for complete financial statements. It is presumed that
users of this interim financial information have read or have access to the
audited financial statements for the preceding fiscal year contained in the
Company's Annual Report on Form 10-K. In the opinion of management, all
adjustments (consisting of normal recurring adjustments) considered necessary
for fair presentation have been included. Operating results for the interim
periods presented are not necessarily indicative of the results that may be
expected for the full year.

     The preparation of financial statements in conformity with generally
accepted accounting principles requires management to make estimates and
assumptions that affect the reported amounts of assets and liabilities and
disclosure of contingent assets and liabilities at the date of the financial
statements and the reported amounts of revenues and expenses during the
reporting period. Actual results could differ from those estimates.

2.   PRINCIPLES OF CONSOLIDATION

     The condensed consolidated financial statements include the accounts of the
Company and its wholly-owned subsidiaries. All significant intercompany accounts
and transactions have been eliminated in consolidation.

3.   NET LOSS PER COMMON SHARE

     Basic net loss per common share is computed using the weighted average
number of shares of Common Stock outstanding during the period. Diluted net loss
per common share is computed using the weighted average number of shares of
common and dilutive potential common shares outstanding during the period.
Potential common shares consist of stock options, warrants and convertible
preferred stock using the treasury stock method and are excluded if their effect
is antidilutive. For the three and nine month periods ended September 30, 2002
and 2001, the weighted average shares outstanding used in the calculation of net
loss per common share do not include potential shares outstanding because they
have the effect of reducing net loss per common share.

4.   LICENSING AGREEMENTS

     As of September 30, 2002, the Company has multiple license agreements for
its portfolio of drug candidates. In the aggregate, these agreements may require
future payments of up to $40,750 contingent upon the achievement of development
milestones, up to $30,000 upon the achievement of sales milestones, and $1,250
of future research and development payments. The Company is also obligated to
issue 250 shares of common stock if development milestones are achieved
regarding compounds for the treatment of hepatitis B obtained in the Avid
Corporation acquisition. Additionally, the Company will pay royalties ranging
from 12% to 23.25% of net sales of each licensed product depending on the net
sales volume for each approved drug candidate. The Company's license agreements
also require minimum royalty payments commencing three years after regulatory
approval of the licensed compound. Milestone payments are typically contingent
on completing phases of clinical trials and receiving registrations for
compounds. Depending on the Company's success and timing in obtaining regulatory
approval, aggregate annual minimum royalties and annual license preservation
fees could range from $75 (if only a single drug candidate is approved for one
indication) to $43,000 (if all drug candidates are approved for all indications)
under the Company's existing license agreements.

                                        8
<Page>

                         TRIANGLE PHARMACEUTICALS, INC.
                          (A DEVELOPMENT STAGE COMPANY)
              NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS
                                   (UNAUDITED)
                    (IN THOUSANDS, EXCEPT PER SHARE AMOUNTS)

5.   TERMINATION OF ABBOTT ALLIANCE

     On July 30, 2002, the Company terminated its alliance with Abbott
Laboratories ("Abbott"). In connection with this termination, the Company:
reacquired all rights previously granted to Abbott for Coviracil(R) for the
treatment of HIV and hepatitis B, amdoxovir, and clevudine; will no longer be
required to provide Abbott a right of first discussion on all future compounds
developed; will have access to two unsecured lines of credit totaling $42,500,
subject to reduction if the Company receives certain types of non-dilutive
financing or to the extent the Company's aggregate cash and investment balances
exceed $40,000; executed a new manufacturing and supply agreement whereby Abbott
will manufacture Coviracil subject to certain terms and conditions; will forego
rights to all remaining milestone payments and its right to co-promote
Kaletra(R), Abbott's HIV product; and granted a 1% royalty to Abbott on the
first $200,000 of cumulative, worldwide Coviracil sales. In addition, this
termination resulted in all but $2,000 of the then remaining deferred revenue
being recognized as revenue in the Company's third quarter 2002 results,
resignation of Abbott's representative on the board of directors and termination
of Abbott's right to purchase additional Triangle common stock.

6.   CONTINGENCIES

     On May 31, 2002, Emory University ("Emory"), GlaxoSmithKline plc
("GlaxoSmithKline") and Shire Pharmaceuticals Group plc ("Shire") settled patent
disputes involving lamivudine and Coviracil. Under the terms of the settlement,
Emory received an exclusive license from Shire under Shire's patents relating to
Coviracil and methods for its use and manufacture, and Shire and GlaxoSmithKline
received exclusive licenses under Emory's patents relating to lamivudine. Under
the terms of the Company's license agreement with Emory, Triangle automatically
acquired an exclusive sublicense to the Shire patents relating to Coviracil
granted under the terms of the settlement, thereby resolving all previously
pending patent disputes regarding Coviracil.

     On August 30, 2002, the Company resolved its patent disputes involving
amdoxovir with Shire. Under the terms of the settlement, Emory and the
University of Georgia Research Foundation, Inc. ("University of Georgia")
received an exclusive license to Shire's patent rights covering amdoxovir and
methods for its use and manufacture. Under the terms of this license agreement,
Triangle acquired an exclusive sublicense to these rights in exchange for an
obligation to pay Shire an incremental royalty on future amdoxovir sales. Under
the settlement agreement, Emory, University of Georgia and Triangle granted
Shire an exclusive license under their patent rights to BCH-13520 and methods
for its use and manufacture.

7.   RECENT ACCOUNTING PRONOUNCEMENTS

     In July 2001, the Financial Accounting Standards Board ("FASB") issued
Statement of Financial Accounting Standards ("SFAS") No. 141, "BUSINESS
COMBINATIONS" and SFAS No. 142, "GOODWILL AND OTHER INTANGIBLE ASSETS." SFAS No.
141 eliminates the pooling-of-interests method of accounting for business
combinations except for qualifying business combinations that were initiated
prior to July 1, 2001. SFAS No. 142 changes the accounting for goodwill and
indefinite lived intangible assets from an amortization method to an
impairment-only approach.

     In August 2001, the FASB issued SFAS No. 143, "ACCOUNTING FOR ASSET
RETIREMENT OBLIGATIONS." The objectives of SFAS No. 143 are to establish
accounting standards for the recognition and measurement of an asset retirement
obligation and its associated asset retirement cost. The provisions of SFAS No.
143 are effective for fiscal years beginning after June 15, 2002.

     In October 2001, the FASB issued SFAS No. 144, "ACCOUNTING FOR THE
IMPAIRMENT OR DISPOSAL OF LONG-LIVED ASSETS." This statement supersedes SFAS No.
121, "ACCOUNTING FOR THE IMPAIRMENT OF LONG-LIVED ASSETS AND FOR LONG-LIVED
ASSETS TO BE DISPOSED OF" and Accounting Principles Board Opinion No. 30,
"REPORTING THE RESULTS OF OPERATIONS - REPORTING THE EFFECTS OF DISPOSAL OF A
SEGMENT OF BUSINESS, AND EXTRAORDINARY, UNUSUAL AND

                                        9
<Page>

                         TRIANGLE PHARMACEUTICALS, INC.
                          (A DEVELOPMENT STAGE COMPANY)
              NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS
                                   (UNAUDITED)
                    (IN THOUSANDS, EXCEPT PER SHARE AMOUNTS)

INFREQUENTLY OCCURRING EVENTS AND TRANSACTIONS." The provisions of SFAS No. 144
are effective for fiscal years beginning after December 15, 2001.

     In April 2002, the FASB issued SFAS No. 145, "Rescission of SFAS Nos. 4, 44
and 64, Amendment of SFAS No. 13, and Technical Corrections." As the title
implies, SFAS No. 145 rescinds or amends previously issued authoritative
pronouncements to make various technical corrections, clarify meanings, or
describe their applicability under changed conditions. The provisions of SFAS
No. 145 are effective for fiscal years beginning after May 15, 2002.

     In June 2002, the FASB issued SFAS No. 146, "Accounting for Costs
Associated with Exit or Disposal Activities." SFAS No. 146 addresses financial
accounting and reporting for costs associated with exit or disposal activities
and nullifies Emerging Issue Task Force Issue No. 94-3, "Liability Recognition
for Certain Employee Termination Benefits and Other Costs to Exit an Activity
(including Certain Costs Incurred in a Restructuring)." The provisions of SFAS
No. 146 are required to be applied for exit or disposal activities initiated
after December 31, 2002.

     The Company adopted SFAS Nos. 142 and 144 as of January 1, 2002, and
expects to adopt SFAS Nos. 143, 145 and 146 as of January 1, 2003, as required.
Adoption of SFAS Nos. 142 and 144 did not have a significant impact, and the
Company does not expect SFAS Nos. 143, 145 and 146 to have a significant impact,
on its consolidated financial position, results of operations and cash flows.

                                       10
<Page>

ITEM 2. MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS
OF OPERATIONS

     This Quarterly Report on Form 10-Q may contain projections, estimates and
other forward-looking statements that involve a number of risks and
uncertainties, including those discussed below at "--Risk and Uncertainties."
While this outlook represents management's current judgment on the future
direction of the business, risks and uncertainties could cause actual results to
differ materially from any future performance suggested below.

     The following discussion and analysis should be read in conjunction with
"Management's Discussion and Analysis of Financial Condition and Results of
Operations" included in our 2001 Annual Report on Form 10-K as well as with our
condensed consolidated financial statements and notes appearing elsewhere in
this Quarterly Report on Form 10-Q.

OVERVIEW

     Triangle is engaged in the development of new drug candidates primarily for
serious viral diseases. Since our inception on July 12, 1995, our operating
activities have related primarily to developing our drug candidates, raising
working capital, negotiating license and option and other strategic arrangements
for our drug candidates and recruiting personnel. We have not received any
revenues from the sale of products and none of our products will be commercially
available before the year 2003. As of September 30, 2002, our accumulated
deficit was approximately $424.7 million.

     We require substantial working capital to fund the development and
potential commercialization of our drug candidates. We will require significant
expenditures to fund preclinical/toxicology testing, clinical research studies,
drug synthesis and manufacturing, license obligations, development of a sales
and marketing infrastructure and ongoing administrative support before receiving
regulatory approvals for our drug candidates. These approvals may be delayed or
not granted at all. We have been unprofitable since our inception and expect to
incur substantial losses for the next several years. Because of the nature of
our business, we expect that losses will fluctuate from period to period and
that fluctuations may be substantial.

     You should consider the operating and financial risks associated with drug
development activities when evaluating our prospects. To address these risks we
must, among other things, successfully develop and commercialize our drug
candidates, secure and maintain all necessary proprietary rights, respond to a
rapidly changing competitive market, obtain additional financing and continue to
attract, retain and motivate qualified personnel. We cannot assure you that we
will be successful in addressing these risks.

     Our operating expenses are difficult to predict and will depend on several
factors. Development expenses, including expenses for drug synthesis and
manufacturing, preclinical testing and clinical research activities, will depend
on the ongoing requirements of our drug development programs, availability of
capital and direction from regulatory agencies, which are difficult to predict.
Management may in some cases be able to control the timing of development
expenses in part by accelerating or decelerating preclinical testing and
clinical trial activities, but many of these expenditures will occur
irrespective of whether our drug candidates are approved when anticipated or at
all. Additionally, selling, general and administrative expenses may vary
depending on which commercialization strategy is adopted for each drug candidate
and whether or not we enter into collaborations with third parties to
commercialize our products. As a result of these factors, we believe that period
to period comparisons are not necessarily meaningful and you should not rely on
them as an indication of future performance. Due to all of the foregoing
factors, it is possible that our consolidated operating results will be below
the expectations of market analysts and investors. In such event, the prevailing
market price of our common stock could be materially adversely affected.

                                       11
<Page>

RESULTS OF OPERATIONS

THREE MONTHS ENDED SEPTEMBER 30, 2002 AND 2001
----------------------------------------------
COLLABORATIVE REVENUE

     Revenue totaled $14.6 million for the three months ended September 30, 2002
as compared to $1.3 million for the same period in 2001. Revenue is solely
related to the realization of deferred collaborative revenue associated with the
Abbott Laboratories strategic alliance, the Abbott Alliance, which we terminated
on July 30, 2002. Prior to this termination, $31.7 million of non-contingent
research and development payments were being amortized over the projected
development period for our drug candidates under the Abbott Alliance. The
termination of this arrangement resulted in all but $2.0 million of our
remaining deferred revenue being recognized upon termination, as we will no
longer have development obligations to Abbott for any of our drug candidates.
The remaining deferred revenue will be recognized in conjunction with, and to
offset, Coviracil royalty payments to Abbott, which are based upon worldwide
Coviracil sales.

LICENSE FEES

     License fees totaled $1.6 million for the three months ended September 30,
2002 as compared to $500,000 for the same period in 2001. The increase in 2002
license fees, as compared to 2001, is related to the timing and magnitude of
milestone obligations and preservation payments under our license and option
agreements for our portfolio of drug candidates. Future license fees may consist
of milestone payments or preservation payments under our license agreements, the
amount of which could be substantial and the timing of which will depend on a
number of factors that we cannot predict. These factors include, among others,
the success of our drug development programs, the timing of regulatory
submissions, the amount of capital available for allocation to individual drug
candidates in our portfolio, and the extent to which we may in-license or
out-license drug candidates.

DEVELOPMENT EXPENSES

     Development expenses totaled $12.2 million for the three months ended
September 30, 2002 as compared to $15.5 million for the same period in 2001. The
decrease in 2002 development expenses, as compared to 2001, is due primarily to
the discontinuation of certain development projects associated with our
restructuring in August 2001 as well as a significant reduction in patent
litigation related expenses. See "--Litigation and Other Contingencies."

     On September 3, 2002, we submitted a New Drug Application, NDA, to the U.S.
Food and Drug Administration, FDA, for U.S. marketing approval of Coviracil to
treat HIV disease. On November 1, 2002, the FDA notified us that our NDA had
been accepted for standard review. Accordingly, we hope to have our first NDA
approved as early as the third quarter of 2003. We intend to submit a Marketing
Authorisation Application, MAA, in Europe, and to complete our evaluation of
alternative strategies for the commercialization of Coviracil before December
31, 2002. Once approved, these authorizations would allow us to market Coviracil
for the treatment of HIV disease in the United States and the European Union.

     Our future development expenses will depend on the results and magnitude of
our clinical and preclinical/toxicology activities, our targeted future cash
usage, availability of capital to simultaneously fund multiple drug candidate
development programs and requirements imposed by regulatory agencies. In
addition, we occasionally enter into collaborative arrangements with
governmental and other parties to assist in conducting the clinical trials
necessary for the development of our compounds. This practice allows us to
benefit from the experience of the collaborative party in conducting such trials
and to share some of the financial and administrative burden of these trials. To
date, we have entered into collaborative clinical trial arrangements for our
Coviracil, amdoxovir and immunostimulatory sequences, ISS, drug candidates.
Since our development expenses will depend on our clinical and preclinical
activities, development expenses may fluctuate significantly from period to
period. We expect our development costs to increase as more of our development
programs enter into the later stages of clinical development. In addition, if we
in-license or out-license rights to drug candidates our development expenses may
fluctuate significantly from prior periods.

                                       12
<Page>

PURCHASED RESEARCH AND DEVELOPMENT EXPENSE

     There was no purchased research and development expense for the three
months ended September 30, 2002 as compared to $320,000 for the same period in
2001. The 2001 charge relates to the September 2001 issuance of 100,000 shares
of common stock as consideration to the former Avid Corporation shareholders for
their remaining rights relating to mozenavir dimesylate. That issuance satisfied
all current and any future obligations in regards to contingent development
obligations for mozenavir dimesylate to the former Avid Corporation shareholders
and no future purchased research and development expenses are currently
anticipated.

SELLING, GENERAL AND ADMINISTRATIVE EXPENSES

     Selling, general and administrative expenses totaled $2.3 million for the
three months ended September 30, 2002 as compared to $1.6 million for the same
period in 2001. The increase in 2002 selling, general and administrative
expenses, as compared to 2001, is primarily related to an increase in 2002
salaries and benefits as well as an increase in 2002 professional services,
including legal services. Our selling, general and administrative expenses may
fluctuate from period to period and such fluctuations may be significant. Future
selling, general and administrative expenses will depend on the level and method
of our future development and commercialization activities, the commercial
availability of our products and the commercialization strategy we adopt. We
expect that our selling, general and administrative expenses will increase
significantly in future periods that immediately precede and follow our first
product launch and subsequent launches of other products.

RESTRUCTURING EXPENSE

     There was no restructuring expense for the three months ended September 30,
2002 as compared to $2.3 million for the same period in 2001. In August 2001, we
announced and began a restructuring of our development activities and overall
operations designed to lower our near term monthly cash usage and to focus our
financial and human resources on activities that are expected to have the
highest probability of near term regulatory approval and economic return. The
charges recorded at that time were sufficient to complete the corporate
restructuring.

GAINS (LOSSES) ON INVESTMENTS, NET

     Gains on investments totaled $11,000 for the three months ended September
30, 2002 as compared to $9,000 of gains for the same period in 2001. These gains
represent realized gains on our general investment portfolio.

INTEREST INCOME, NET

     Net interest income totaled $456,000 for the three months ended September
30, 2002 as compared to $764,000 for the same period in 2001. The significant
decrease in 2002 interest income, as compared to 2001, is due to smaller average
investment balances and much lower short-term interest rates in the third
quarter of 2002. Future interest income will depend on our future cash and
investment balances and the return on these investments. See "--Liquidity and
Capital Resources."

NINE MONTHS ENDED SEPTEMBER 30, 2002 AND 2001
---------------------------------------------
COLLABORATIVE REVENUE

     Revenue totaled $16.6 million for the nine months ended September 30, 2002
as compared to $4.8 million for the same period in 2001. Revenue is solely
related to the realization of deferred collaborative revenue associated with the
Abbott Alliance which we terminated on July 30, 2002. Prior to this termination,
$31.7 million of non-contingent research and development payments were being
amortized over the projected development period for our drug candidates under
the Abbott Alliance. The termination of this arrangement resulted in all but
$2.0 million of our remaining deferred revenue being recognized upon
termination, as we will no longer have development obligations to Abbott for any
of our drug candidates. The remaining deferred revenue will be recognized in
conjunction with, and to offset, Coviracil royalty payments to Abbott, which are
based upon worldwide Coviracil sales.

                                       13
<Page>

LICENSE FEES

     License fees totaled $1.8 million for the nine months ended September 30,
2002 as compared to $2.5 million for the same period in 2001. License fees for
2002 and 2001 relate to the recognition of milestone obligations and
preservation fees under our license and option agreements for our portfolio of
drug candidates. The decrease in 2002 license fee expense, as compared to 2001,
is related to the timing and magnitude of milestone obligations and preservation
payments under our license and option agreements for our portfolio of drug
candidates. Future license fees may consist of milestone payments or
preservation payments under our license agreements, the amount of which could be
substantial and the timing of which will depend on a number of factors that we
cannot predict. These factors include, among others, the success of our drug
development programs, the timing of regulatory submissions, the amount of
capital available for allocation to individual drug candidates in our portfolio,
and the extent to which we may in-license or out-license drug candidates.

DEVELOPMENT EXPENSES

     Development expenses totaled $38.9 million for the nine months ended
September 30, 2002 as compared to $58.1 million for the same period in 2001.
Development expenses for 2002 consisted primarily of expenses for clinical
trials, employee compensation, drug synthesis and amounts paid for professional
services. Development expenses for 2001 consisted primarily of expenses for drug
synthesis, clinical trials, employee compensation, and preclinical/toxicology
testing. The substantial decrease in 2002 development expenses, as compared to
2001, is the result of significantly reduced spending on non-core development
programs, other drug candidates, and moderated spending as a result of our
restructuring in August 2001, as well as substantially reduced manufacturing and
patent litigation expenses for Coviracil and amdoxovir. As all of the previously
pending intellectual property disputes associated with Coviracil and amdoxovir
have been resolved, we expect that our future patent litigation costs will
decrease significantly from historical levels. See "--Litigation and Other
Contingencies."

     Development expenses by major project for the nine months ended September
30, 2002 and 2001 are shown below (dollars in thousands).

<Table>
<Caption>
---------------------------------------------------------------------------------------------------------
             COMPOUND                INDICATION      2002 COSTS      %   2001 COSTS  %   DIFFERENCE    %
---------------------------------------------------------------------------------------------------------
<S>                                 <C>               <C>           <C>   <C>       <C>  <C>         <C>
Coviracil                           HIV               $   17,366     45   $ 18,553   32  $  (1,187)   (6)

Amdoxovir                           HIV                      825      2      9,799   17     (8,974)  (92)

Clevudine                           Hepatitis B            1,048      3      2,074    4     (1,026)  (49)

Coviracil                           Hepatitis B            3,490      9      3,152    5        338    11

Immunostimulatory sequences         Hepatitis B              943      2      1,750    3       (807)  (46)
candidate

Other drug candidates                                        506      1      6,283   11     (5,777)  (92)

Indirect (unallocated) development costs                  14,761     38     16,504   28     (1,743)  (11)

Total                                                 $   38,939    100   $ 58,115  100  $ (19,176)  (33)
---------------------------------------------------------------------------------------------------------
</Table>

     Our future development expenses will depend on the results and magnitude of
our clinical and preclinical/toxicology activities, our targeted future cash
usage, availability of capital to simultaneously fund multiple drug candidate
development programs and requirements imposed by regulatory agencies. In
addition, we occasionally enter into collaborative arrangements with
governmental and other parties to assist in conducting the clinical trials
necessary for the development of our compounds. This practice allows us to
benefit from the experience of the collaborative party in conducting such trials
and to share some of the financial and administrative burden of these trials. To
date, we have entered into collaborative clinical trial arrangements for our
Coviracil, amdoxovir and ISS drug candidates. Since our development expenses
will depend on our clinical and preclinical activities, development expenses may
fluctuate significantly from period to period. We expect our development costs
to increase as more of our development programs enter into the later stages of
clinical development. In addition, if we in-license or out-license rights to
drug candidates our development expenses may fluctuate significantly from prior
periods.

                                       14
<Page>

SELLING, GENERAL AND ADMINISTRATIVE EXPENSES

     Selling, general and administrative expenses totaled $5.3 million for the
nine months ended September 30, 2002 as compared to $6.6 million for the same
period in 2001. Selling, general and administrative expenses for 2002 consisted
primarily of employee compensation, amounts paid for outside professional
services, insurance costs and rent expense. Selling, general and administrative
expenses for 2001 consisted primarily of employee compensation, amounts paid for
outside professional services, and rent expense. The decrease in 2002 selling,
general and administrative expenses, as compared to 2001, is primarily related
to decreased 2002 sales and marketing spending for the period. Our selling,
general and administrative expenses may fluctuate from period to period and such
fluctuations may be significant. Future selling, general and administrative
expenses will depend on the level and method of our future development and
commercialization activities, the commercial availability of our products and
the commercialization strategy we adopt. We expect that our selling, general and
administrative expenses will increase significantly in future periods that
immediately precede and follow our first product launch and subsequent launches
of other products.

GAINS (LOSSES) ON INVESTMENTS, NET

     Gains on investments totaled $16,000 for the nine months ended September
30, 2002 as compared to $76,000 of gains for the same period in 2001. These
gains represent realized gains on our general investment portfolio.

INTEREST INCOME, NET

     Net interest income totaled $1.7 million for the nine months ended
September 30, 2002 as compared to $2.7 million for the same period in 2001. The
significant decrease in 2002 interest income, as compared to 2001, is due to
smaller average investment balances in 2002 and much lower short-term interest
rates. Future interest income will depend on our future cash and investment
balances and the return on these investments. See "--Liquidity and Capital
Resources."

OTHER INCOME

     Other income totaled $10.0 million for the nine months ended September 30,
2002, as compared to no income or expense for the same period in 2001. In
January 2002, our then Chief Executive Officer and Chairman of the Board, Dr.
David W. Barry, died unexpectedly. We subsequently received a $10.0 million
payment under a key-man insurance policy.

LIQUIDITY AND CAPITAL RESOURCES

     We have financed our operations since inception (July 12, 1995) through
September 30, 2002 primarily with the net proceeds received from private
placements of equity securities, which have provided aggregate net proceeds of
approximately $353.1 million, from public offerings of common stock, which have
provided aggregate net proceeds of approximately $97.7 million, as well as $31.5
million of net non-contingent research and development reimbursement proceeds
from the Abbott Alliance and receipt of a $10.0 million key-man insurance policy
payment.

     At September 30, 2002, we had net working capital of $40.0 million, a
decrease of approximately $14.1 million from December 31, 2001. The decrease in
working capital is principally due to the use of funds for our normal operating
expenses offset by the receipt of a $10.0 million key-man insurance policy
payment received in March 2002. Our principal sources of liquidity at September
30, 2002 were $36.7 million in cash and cash equivalents, $30.6 million in
investments which are considered "available-for-sale," and $1.0 million of
strategic corporate investments, reflecting a $39.9 million decrease of cash,
cash equivalent and investment balances over those at December 31, 2001.

     Our working capital requirements may fluctuate in future periods depending
on many factors, including the efficiency of manufacturing processes developed
on our behalf by third parties, the cost of drugs supplied by third party
contractors, the magnitude, scope and timing of our drug development programs,
the cost, timing and outcome

                                       15
<Page>

of regulatory reviews and changes in regulatory requirements, costs under the
license agreements relating to our drug candidates, including the costs of
obtaining patent protection for our drug candidates, the timing and terms of
business development activities related to current and new drug candidates, the
rate of technological advances relevant to our operations, the timing, method
and cost of the commercialization of our drug candidates, the level of required
administrative and legal support, the availability of capital to support
multiple drug candidate development programs and the potential expansion of
facility space.

     Amounts payable by us in the future under our existing license and research
agreements are uncertain due to a number of factors, including the progress of
our drug development programs, our ability to obtain regulatory approval to
commercialize drug candidates and the commercial success of approved drugs. As
of September 30, 2002, our existing license and research agreements may require
future cash payments of up to $40.8 million contingent on the achievement of
development milestones, up to $30.0 million on the achievement of sales
milestones, and $1.3 million of future research and development payments. As of
September 30, 2002, we are also obligated to issue 250,000 shares of common
stock if development milestones are achieved regarding compounds for the
treatment of hepatitis B obtained in the Avid Corporation acquisition, although
we are not currently developing these compounds. Additionally, we are obligated
to pay royalties ranging from 12% to 23.25% of net sales of each licensed
product depending on net sales volume of each of our drug candidates. Most of
our license agreements require minimum royalty payments commencing three years
after regulatory approval of the licensed compound. Depending on our success and
timing in obtaining regulatory approval, aggregate annual minimum royalties and
license preservation fees under our existing license agreements could range from
$75,000 if only a single drug candidate is approved for one indication, to $43.0
million if all drug candidates are approved for all indications.

     We believe that our existing cash, cash equivalents and investments will be
adequate to satisfy our anticipated working capital requirements through the
second quarter of 2003. We expect that upon approval of Coviracil for the
treatment of HIV in the United States and Europe, additional liquidity may be
available under the Abbott lines of credit (See "--Termination of the Abbott
Alliance."). In addition, we have an effective shelf registration statement and
may seek additional funding through one or more equity financings. The potential
utilization of all, or a component, of either of these two financing mechanisms
would extend our ability to satisfy our anticipated working capital requirements
beyond the second quarter of 2003. We expect that we will be required to raise
additional capital to fund our future operations through equity or debt
financings or from other sources. Additional funding may not be available on
favorable terms from any of these sources or at all. Our future financing needs
will depend on the results of clinical trials, size of drug candidate portfolio,
timing of regulatory submissions and approvals, business development activities,
commercial potential of our drug candidates and our ability to successfully
commercialize our drug candidates. We may also consider modifying the timing or
scope of our clinical programs, out-licensing one or more of our compounds or
entering into new collaborative arrangements, any of which may impact our
anticipated capital requirements. Our liquidity projections are subject to
several risks including unanticipated cost overruns, the need to expand the
magnitude or scope of existing development programs, the need to change the
number or timing of clinical trials, unanticipated regulatory requirements, the
timing and costs related to the FDA's review and preparation for the commercial
launch of Coviracil, the timing of regulatory approvals and our ability to
access the Abbott lines of credit, our ability to sell common stock under our
shelf registration, and other factors described under the caption "Risk and
Uncertainties" elsewhere in this Form 10-Q.

TERMINATION OF THE ABBOTT ALLIANCE

     On July 30, 2002, we reacquired full product rights, including rights to
all profits, from Abbott for four of our drug development programs in clinical
development. We entered into a series of agreements with Abbott terminating the
Abbott Alliance under which we:

     -    reacquired all rights previously granted to Abbott, which includes the
          rights to all future profits for Coviracil for the treatment of HIV
          and hepatitis B, amdoxovir, and clevudine;
     -    will no longer be required to provide Abbott a right of first
          discussion on all future compounds which we develop;
     -    will have access to two unsecured lines of credit totaling $42.5
          million, subject to certain terms and conditions. Upon approval of
          Coviracil for the treatment of HIV in the United States, Abbott will
          make available to us an unsecured line of credit of $30 million. Upon

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          approval of Coviracil for the treatment of HIV in Europe, Abbott will
          make available to us an unsecured line of credit of $12.5 million. The
          amounts available under the Abbott lines of credit will be reduced if
          we receive certain types of non-dilutive financing from other parties.
          The amounts can also be reduced by the extent our aggregate cash and
          investment balances exceed $40.0 million.
     -    executed a new manufacturing and supply agreement under which Abbott
          will manufacture quantities of Coviracil expected to be sufficient for
          approximately the first year's sales, and Abbott will provide
          manufacturing capabilities through July 31, 2005 at our request.
          Abbott will also provide resources for and facilitate the transfer of
          the Coviracil manufacturing process to a third-party manufacturer.
     -    will forego rights to all remaining milestone payments and our right
          to co-promote Abbott's HIV product, Kaletra(R).
     -    granted a 1% royalty to Abbott on the first $200 million of
          cumulative, worldwide Coviracil sales.

     Termination of the Abbott Alliance resulted in all but $2.0 million of our
remaining deferred revenue being recognized in our third quarter 2002 results as
we no longer have development obligations to Abbott for any of our drug
candidates. In addition, Abbott's representative on our board of directors has
resigned and Abbott's right to purchase additional Triangle common stock has
terminated.

     We are currently exploring strategic opportunities for developing,
commercializing and manufacturing our drug candidates, any of which could have a
material impact on our working capital requirements and on our business as a
whole. These opportunities may include alliances, out-licensing arrangements and
joint ventures. In addition, from time to time we receive indications of
interest from third parties to acquire us. At this time, we have no agreements
or firm commitments to enter into any such arrangements. We will continue to
evaluate opportunities on an ongoing basis.

LITIGATION AND OTHER CONTINGENCIES

     On May 31, 2002, Emory University, GlaxoSmithKline plc and Shire
Pharmaceuticals Group plc settled patent disputes involving lamivudine and
Coviracil. Under the terms of the settlement, Emory received an exclusive
license from Shire under Shire's patents relating to Coviracil and methods for
its use and manufacture, and Shire and GlaxoSmithKline received exclusive
licenses under Emory's patents relating to lamivudine. Under the terms of our
license agreement with Emory, we automatically acquired an exclusive sublicense
to the Shire patents relating to Coviracil granted under the terms of the
settlement, thereby resolving all previously pending patent disputes regarding
Coviracil.

     On August 30, 2002, we resolved our patent disputes involving amdoxovir
with Shire. Under the terms of the settlement, Emory and the University of
Georgia Research Foundation, Inc., University of Georgia, received an exclusive
license to Shire's patent rights covering amdoxovir and methods for its use and
manufacture. Under the terms of this license agreement, Triangle acquired an
exclusive sublicense to these rights in exchange for an obligation to pay Shire
an incremental royalty on future amdoxovir sales. Under the settlement
agreement, Emory, University of Georgia and Triangle granted Shire an exclusive
license under their patent rights to BCH-13520 and methods for its use and
manufacture.

CRITICAL ACCOUNTING POLICIES AND ESTIMATES

     Our condensed consolidated financial statements require us to make
estimates and judgments that affect the reported amounts of assets, liabilities,
revenues, expenses and related disclosure of contingent assets and liabilities.
We evaluate our estimates, judgments and the policies underlying these estimates
on a periodic basis as the situation changes, and regularly discuss financial
events, policies, and issues with members of our audit committee and our
independent accountants. We routinely evaluate our estimates and policies
regarding clinical trial, preclinical/toxicology and manufacturing liabilities;
patent related liabilities; license milestone obligations; revenue recognition;
inventory; intangible assets and deferred tax assets.

                                       17
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     We generally enter into contractual agreements with third-party vendors to
provide clinical, preclinical/toxicology, manufacturing and other services in
the ordinary course of business. Many of these contracts are subject to
milestone based invoicing and the contract could extend over several years. We
record liabilities under these contractual commitments when we determine an
obligation has been incurred, regardless of the timing of the invoice. Patent
related and license milestone liabilities are recorded based upon various
assumptions or events that we believe are the most reasonable in each individual
circumstance, as well as based upon historical experience. License milestone
liabilities and the related expense are recorded when the milestone criterion
achievement or license preservation payment is probable. We have not recognized
any assets for inventory, intangible items or deferred taxes as we have yet to
receive regulatory approval for any of our drug candidates and there is
therefore uncertainty in regards to the expected net realizable value for any
potential asset that could be recorded in regards to these items. We have
recognized collaboration revenue based upon the amortization of non-contingent
reimbursed research and development payments that were received under the Abbott
Alliance. As a result of the termination of the Abbott Alliance, we have
recognized all but $2.0 million of deferred revenue associated with the Abbott
Alliance in our third quarter 2002 results.

     In all cases, actual results may differ from our estimates.

RISK AND UNCERTAINTIES

     IN ADDITION TO THE OTHER INFORMATION IN THIS DOCUMENT, THE FOLLOWING RISKS
AND UNCERTAINTIES SHOULD BE CAREFULLY CONSIDERED IN EVALUATING US AND OUR
BUSINESS.

ALL OF OUR DRUG CANDIDATES ARE IN DEVELOPMENT AND WE MAY NEVER SUCCESSFULLY
COMMERCIALIZE THEM.

     Some of our drug candidates are at an early stage of development and all of
our drug candidates will require expensive and lengthy testing and regulatory
clearances before we may commercialize them. We do not expect any of our drug
candidates to be commercially available before the year 2003. There are many
reasons that we may fail in our efforts to develop or commercialize our drug
candidates, including that:

     -    our drug candidates may be ineffective, toxic or may not receive
          regulatory clearances,
     -    our drug candidates may be too expensive to manufacture or market or
          may not achieve broad market acceptance,
     -    third parties may hold proprietary rights that preclude us from
          developing or marketing our drug candidates, or
     -    third parties may market equivalent or superior products.

     The success of our business depends on our ability to successfully develop
and market our drug candidates.

WE HAVE INCURRED LOSSES SINCE INCEPTION AND MAY NEVER ACHIEVE PROFITABILITY.

     We formed Triangle in July 1995 and have incurred losses since our
inception. At September 30, 2002, our accumulated deficit was $424.7 million.
Our historical costs relate primarily to the acquisition and development of our
drug candidates and selling, general and administrative costs. We have not
generated any revenue from the sale of our drug candidates to date, and do not
expect to do so before the year 2003. In addition, we expect annual losses to
continue over the next several years as a result of our drug development and
commercialization efforts. To become profitable, we must successfully develop
and obtain regulatory approval for our drug candidates and effectively
manufacture, market and sell any products we develop. We may never generate
significant revenue or achieve profitability.

IF WE NEED ADDITIONAL FUNDS AND ARE UNABLE TO RAISE THEM, WE WILL HAVE TO
CURTAIL OR CEASE OPERATIONS.

     Our drug development programs and our efforts to commercialize our drug
candidates require substantial working capital, including expenses for:

                                       18
<Page>

     -    preclinical testing,
     -    chemical synthetic scale-up,
     -    manufacture of drug substance for clinical trials,
     -    toxicology studies,
     -    clinical trials of drug candidates,
     -    sales and marketing,
     -    payments to our licensors, and
     -    potential commercial launch of our drug candidates.

     Our future working capital needs will depend on many factors, including:

     -    the progress, magnitude and success of our drug development programs,
     -    the scope and results of preclinical testing and clinical trials,
     -    the cost, timing and outcome of regulatory submissions and reviews,
     -    the costs under current and future license agreements for our drug
          candidates, including the costs of obtaining and enforcing patent
          protection for our drug candidates,
     -    the costs of acquiring any additional drug candidates,
     -    the out-licensing of existing drug candidates,
     -    the rate of technological advances by us and other companies,
     -    the commercial potential of our drug candidates,
     -    the magnitude of our administrative and legal expenses,
     -    the costs of establishing sales and marketing functions, and
     -    the costs of establishing third party arrangements for manufacturing.

     We have incurred negative cash flow from operations since we incorporated
Triangle and do not expect to generate positive cash flow from our operations
for at least the next several years. We believe that our existing cash, cash
equivalents and investments will be adequate through the second quarter of 2003.
We expect that we will need additional future financings to fund our operations.
We may not be able to obtain adequate financing to fund our operations and any
additional financing we obtain may be on terms that are not favorable to us. Our
ability to access the lines of credit from Abbott is subject to conditions we
may not be able to meet. Any future equity financings could substantially dilute
our stockholders. If adequate funds are not available, we will be required to
delay, reduce or eliminate one or more of our drug development programs or to
enter into new collaborative arrangements on terms that may not be favorable to
us. These collaborative arrangements could result in the transfer of valuable
rights to third parties. In addition, we may acquire technologies and drug
candidates that would increase our working capital requirements.

PROJECTED DEVELOPMENT COSTS ARE DIFFICULT TO ESTIMATE AND MAY CHANGE FREQUENTLY
PRIOR TO REGULATORY APPROVAL.

     While all new compounds require standard regulated phases of testing, the
actual type and scope of testing can vary significantly among different drug
candidates which may result in significant disparities in the total costs
required to complete the respective development programs.

     The number and type of studies that may be required by the FDA for a
particular compound are based on the compound's clinical profile compared to
existing therapies for the targeted patient population. Factors that affect the
costs of a clinical trial include:

     -    the number of patients required to participate in clinical trials to
          demonstrate statistical significance for a drug's safety and efficacy,
     -    the time required to enroll the targeted number of patients in
          clinical trials, which may vary depending on the size and availability
          of the targeted patient population and the perceived benefit to study
          participants, and
     -    the number and type of required laboratory tests supporting clinical
          trials.

                                       19
<Page>

     Other activities required before submitting an NDA include regulatory
preparation for submission, biostatistical analyses, scale-up synthesis, and the
production of a required amount of commercial grade drug product inventory which
meets current Good Manufacturing Practice standards.

     In addition, ongoing development programs and associated costs are subject
to frequent, significant and unpredictable changes due to a number of factors,
including:

     -    data collected in preclinical or clinical studies may prompt
          significant changes or enhancements to an ongoing development program,
     -    the FDA may direct the sponsor to change or enhance its ongoing
          development program based on developments in the testing of similar
          compounds or related compounds,
     -    unexpected regulatory requirements or interim reviews by regulatory
          agencies may cause delays or changes to development programs, and
     -    anticipated manufacturing costs may change significantly due to
          required changes in manufacturing processes or variances from
          anticipated manufacturing process yields.

BECAUSE WE MAY NOT SUCCESSFULLY COMPLETE CLINICAL TRIALS REQUIRED FOR REGULATORY
APPROVAL OF OUR DRUG CANDIDATES, OUR BUSINESS MAY NEVER ACHIEVE PROFITABILITY.

     No regulatory authority has approved any of our drug candidates. To obtain
regulatory approvals needed for the sale of our drug candidates, we must
demonstrate through preclinical testing and clinical trials that each drug
candidate is safe and effective. The clinical trial process is complex and
uncertain and the regulatory environment varies widely from country to country.
Positive results from preclinical testing and early clinical trials do not
ensure positive results in pivotal clinical trials. Many companies in our
industry have suffered significant setbacks in pivotal clinical trials, even
after promising results in earlier trials. Any of our drug candidates may
produce undesirable side effects in humans. These side effects, or side effects
from other drugs in a trial, could cause us or regulatory authorities to
interrupt, delay or halt clinical trials of a drug candidate, or could result in
regulatory authorities refusing to approve the drug candidate for any and all
targeted indications. We, the FDA, or foreign regulatory authorities may suspend
or terminate clinical trials at any time if we or they believe the trial
participants face unacceptable health risks.

     Our clinical development program for amdoxovir was placed on partial
clinical hold by the FDA as a result of concern about possible side effects
called lenticular opacities. The extent to which amdoxovir increased the
occurrence of lenticular opacities in patients receiving amdoxovir, if at all,
is unknown. Patients in clinical studies who are benefiting from amdoxovir may
continue on treatment. New studies involving patients who have failed other
treatments which contained a drug from each currently approved class of anti-HIV
medications and require amdoxovir in their regimens may also proceed. We plan to
initiate two clinical trials to be conducted by the AIDS Clinical Trial Group in
the United States and a third Phase II clinical trial in Europe. The data from
these trials should help us determine several objectives, including if there is
any relationship between lenticular opacities and the use of amdoxovir.
Discussions with the FDA regarding the partial clinical hold are ongoing.

CLINICAL TRIALS MAY TAKE LONGER TO COMPLETE AND COST MORE THAN WE EXPECT, WHICH
WOULD ADVERSELY AFFECT OUR ABILITY TO COMMERCIALIZE DRUG CANDIDATES AND ACHIEVE
PROFITABILITY.

     Clinical trials are lengthy and expensive. They require adequate supplies
of drug substance and sufficient patient enrollment. Patient enrollment is a
function of many factors, including:

     -    the size of the patient population,
     -    the nature of the protocol,
     -    the proximity of patients to clinical sites,
     -    the eligibility criteria for the clinical trial, and
     -    the perceived benefit of participating in a clinical trial.

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<Page>

     Delays in patient enrollment can result in increased costs and longer
development times. Even if we successfully complete clinical trials, we may not
be able to submit any required regulatory submissions in a timely manner and we
may not receive regulatory approval for the drug candidate. In addition, if the
FDA or foreign regulatory authorities require additional clinical trials we
could face increased costs and significant development delays.

     We conduct clinical trials in many countries around the world and are
subject to the risks and uncertainties of doing business internationally.
Disruptions in communication and transportation, changes in governmental
policies, civil unrest and currency exchange rates may affect the time and costs
required to complete clinical trials in other countries.

     Changes in regulatory policy or new regulations could also result in delays
or rejections of our applications for approval of our drug candidates. Drug
candidates designated as "fast track" products by the FDA may not continue to
qualify for expedited review. Even though some of our drug candidates have
received "fast track" designation, the FDA may not approve them at all or any
sooner than other drug candidates that do not qualify for expedited review.

IF WE OR OUR LICENSORS ARE NOT ABLE TO OBTAIN AND MAINTAIN ADEQUATE PATENT
PROTECTION FOR OUR DRUG CANDIDATES, WE MAY BE UNABLE TO COMMERCIALIZE OUR DRUG
CANDIDATES OR PREVENT OTHER COMPANIES FROM USING OUR TECHNOLOGY IN COMPETITIVE
PRODUCTS.

     Our success will depend on our ability and the ability of our licensors to
obtain and maintain patents and proprietary rights for our drug candidates and
to avoid infringing the proprietary rights of others, both in the United States
and in foreign countries. We have no issued patents solely in our own name and
we have a small number of patent applications of our own pending. We have
several patents and patent applications which are jointly owned with other
entities. We have licensed patents, patent applications and other proprietary
rights from third parties for each of our drug candidates. If we breach our
licenses, we may lose rights to important technology and drug candidates.

     Our patent position on some of our drug candidates, like that of many
pharmaceutical companies, is uncertain and involves complex legal and factual
questions for which important legal principles are unresolved. We may not
develop or obtain rights to products or processes that are patentable. Even if
we do obtain patents, they may not adequately protect the technology we own or
have licensed. In addition, others may challenge, seek to invalidate, infringe
or circumvent any patents we own or license. If they do so successfully, rights
we receive under those patents may not provide competitive advantages to us.
Further, the manufacture, use or sale of our products or processes may infringe
the patent rights of others.

     Third parties may file patent applications or receive patents that conflict
with patents or patent applications we own or have licensed, either by claiming
the same methods or compounds or by claiming methods or compounds that could
dominate those owned by or licensed to us. In addition, we may not be aware of
all patents or patent applications that may impact our ability to make, use or
sell any of our drug candidates. For example, United States patent applications
are confidential while pending in the Patent and Trademark Office, and patent
applications filed in foreign countries are often first published six months or
more after filing. Any conflicts resulting from third party patent applications
and patents could significantly reduce the coverage of our patents and limit our
ability to obtain meaningful patent protection. If other companies obtain
patents with conflicting claims, we may be required to obtain licenses to these
patents or to develop or obtain alternative technology. We may not be able to
obtain any license on acceptable terms or at all. Any failure to obtain licenses
could delay or prevent us from pursuing the development or commercialization of
our drug candidates, which would adversely affect our ability to achieve
profitability.

     IMMUNOSTIMULATORY SEQUENCE PRODUCT CANDIDATES

     In March 2000, we entered into a licensing and collaborative agreement with
Dynavax Technologies Corporation to develop immunostimulatory polynucleotide
sequence product candidates for the prevention and/or treatment of serious viral
diseases, which was amended in September 2002. The amendment narrowed the
scope of the license to specific ISS which are combined with hepatitis B
antigen. The

                                       21
<Page>

amendment limits our diligence obligations to development regarding the
treatment of hepatitis B and provides that Dynavax will conduct specific amounts
of research for the development of the technology licensed to us. ISS are
polynucleotides which stimulate the immune system, and could potentially be used
in combination with our small molecule product candidates to increase the body's
ability to defend against hepatitis B infection.

     There are a number of companies which have patent applications and issued
patents, both in the United States and in other countries, that cover ISS and
their uses. Coley Pharmaceuticals, Inc. has filed several patent applications in
this area and has in addition exclusively licensed a number of patent
applications on this subject from the University of Iowa and Isis
Pharmaceuticals, Inc. A number of these patent applications have been issued. A
number of companies have also filed patent applications and have or are expected
to receive patents on a number of polynucleotides and methods for their use and
manufacture. These patents, if granted, could prevent us from making, using or
selling any ISS that is covered by a patent issued to a third party unless we
obtain a license from that party which may not be available on acceptable terms
or at all.

     With respect to any of our drug candidates, litigation, patent opposition
and adversarial proceedings could result in substantial costs to us. We
anticipate that additional litigation and/or proceedings could be initiated to
enforce any patents we own or license, or to determine the scope, validity and
enforceability of our or other parties' proprietary rights and the priority of
an invention. Any of these activities could result in substantial costs and/or
delays to us. The outcome of any of these proceedings may significantly affect
our rights to develop and commercialize drug candidates and technology.

     United States patents carry a presumption of validity and generally can be
invalidated only through clear and convincing evidence. A court or
administrative body may not hold our licensed patents valid or may not find an
alleged infringer to be infringing. Further, the license agreements with Emory,
the University of Georgia and Dynavax provide that each of these licensors is
primarily responsible for any patent prosecution activities, such as litigation,
patent conflict proceeding, patent opposition or other actions, for the
technology licensed to us. These agreements also provide that we generally must
reimburse these licensors for the costs they incur in performing these
activities. Similarly, Yale University and the University of Georgia, the
licensors of clevudine to Bukwang Pharm. Ind. Co., Ltd., are primarily
responsible for patent prosecution activities with respect to clevudine at our
expense. As a result, we generally do not have the ability to institute or
determine the conduct of any patent proceedings unless our licensors elect not
to institute or to abandon the proceedings. If our licensors elect to institute
and prosecute patent proceedings, our rights will depend in part on the manner
in which these licensors conduct the proceedings. In any proceedings they elect
to initiate and maintain, these licensors may not vigorously pursue or defend or
may decide to settle on terms that are unfavorable to us. An adverse outcome of
these proceedings could subject us to significant liabilities to third parties,
require disputed rights to be licensed from third parties or require us to cease
using technology, any of which could adversely affect our business. Moreover,
the mere uncertainty resulting from the initiation and continuation of any
technology related litigation or adversarial proceeding could adversely affect
our business pending resolution of the disputed matters.

BECAUSE WE MAY NOT BE ABLE TO MAINTAIN THE CONFIDENTIALITY OF OUR TRADE SECRETS
AND KNOW-HOW, WE MAY LOSE A COMPETITIVE ADVANTAGE.

     We also rely on unpatented trade secrets and know-how to maintain our
competitive position, which we seek to protect, in part, by confidentiality
agreements with employees, consultants and others. These parties may breach or
terminate these agreements, and we may not have adequate remedies for any
breach. Our trade secrets may also be independently discovered by competitors.
We rely on technologies to which we do not have exclusive rights or which may
not be patentable or proprietary and may be available to competitors. We have
filed applications for, but have not obtained, trademark registrations for
various marks in the United States and other jurisdictions. We have received
U.S. trademark registrations for our corporate name and our corporate name and
logo, as well as the mark Coviracil(R). We have received a Canadian trademark
registration for the mark Coviracil(R). We have also received a registration in
the European Union for our corporate logo. Our application in the European Union
for the mark Coviracil(TM) has been denied by the Office for Harmonization in
the Internal Market; however, we have filed an appeal with this office.
If our appeal is not granted, we will need to adopt a different product
name for emtricitabine in Europe. Several other companies use trade names
that are similar to our name for their businesses. If we are unable to obtain
any licenses or trademark registrations that may be necessary for the use of
our corporate name, we may be required to change our name. Our management
personnel were

                                       22
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previously employed by other pharmaceutical companies. The prior employers of
these individuals may allege violations of trade secrets and other similar
claims relating to their drug development activities for us.

THE COSTS AND TIME REQUIRED TO COMPLY WITH EXTENSIVE GOVERNMENT REGULATIONS
COULD PREVENT OR DELAY THE COMMERCIALIZATION OF OUR DRUG CANDIDATES.

     In addition to preclinical testing, clinical trials and other approval
procedures for human pharmaceutical products, we are subject to numerous
domestic and international regulations covering the development, registration,
and commercialization of pharmaceutical products. These regulations affect:

     -    manufacturing,
     -    safety,
     -    labeling,
     -    storage,
     -    record keeping,
     -    reporting, and
     -    marketing and promotion.

     We must also comply with regulations governing non-clinical and clinical
laboratory practices, safe working conditions, and the use and disposal of
hazardous substances, including radioactive compounds and infectious disease
agents we use in connection with our development work. The requirements vary
widely from country to country and some requirements may vary from state to
state in the United States. We expect the process of obtaining these approvals
and complying with appropriate government regulations to be time consuming and
expensive. Even if our drug candidates receive regulatory approval, we may still
face difficulties in marketing and manufacturing those drug candidates. Any
approval may be contingent on postmarketing studies or other conditions. The
approval of any of our drug candidates may limit the indicated uses of the drug
candidate. A marketed product, its manufacturer and the manufacturer's
facilities are subject to continual review and periodic inspections. The
discovery of previously unknown problems with a product, manufacturer or
facility may result in restrictions on the product or manufacturer, including
withdrawal of the product from the market. The failure to comply with applicable
regulatory requirements can, among other things, result in:

     -    fines,
     -    suspended regulatory approvals,
     -    refusal to approve pending applications,
     -    refusal to permit exports from the United States,
     -    product recalls,
     -    seizure of products,
     -    injunctions,
     -    operating restrictions, and
     -    criminal prosecutions.

     In addition, adverse clinical results by others could negatively impact the
development and approval of our drug candidates. Some of our drug candidates are
intended for use as combination therapy with one or more other drugs, and
adverse safety, effectiveness or regulatory developments in connection with the
other drugs will also have an adverse effect on our business.

INTENSE COMPETITION MAY RENDER OUR DRUG CANDIDATES NONCOMPETITIVE OR OBSOLETE.

     We are engaged in segments of the drug industry that are highly competitive
and rapidly changing. Any of our current drug candidates that we successfully
develop will compete with numerous existing therapies. In addition, many
companies are pursuing novel drugs that target the same diseases we are
targeting. We believe that a significant number of drugs are currently under
development and will become available in the future for the treatment of HIV and
hepatitis B. We anticipate that we will face intense and increasing competition
as new products enter the market and advanced technologies become available. Our
competitors' products may be more effective, or more effectively marketed and
sold, than any of our products. Competitive products may render our

                                       23
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products obsolete or noncompetitive before we can recover the expenses of
developing and commercializing our drug candidates. Furthermore, the development
of a cure or new treatment methods for the diseases we are targeting could
render our drug candidates noncompetitive, obsolete or uneconomical. Many of our
competitors:

     -    have significantly greater financial, technical and human resources
          than we have and may be better equipped to develop, manufacture and
          market products,
     -    have extensive experience in preclinical testing and clinical trials,
          obtaining regulatory approvals and manufacturing and marketing
          pharmaceutical products, and
     -    have products that have been approved or are in late stage development
          and operate large, well-funded research and development programs.

     Smaller companies may also prove to be significant competitors,
particularly through collaborative arrangements with large pharmaceutical and
biotechnology companies. Academic institutions, governmental agencies and other
public and private research organizations are also becoming increasingly aware
of the commercial value of their inventions and are more actively seeking to
commercialize the technology they have developed.

     If we successfully develop and obtain approval for our drug candidates, we
will face competition based on many factors including:

     -    the safety and effectiveness of our products,
     -    the timing and scope of regulatory approvals,
     -    the availability of supply,
     -    marketing and sales capability,
     -    reimbursement coverage,
     -    price, and
     -    patent position.

     Our competitors may develop or commercialize more effective or more
affordable products, or obtain more effective patent protection, than we do.
Accordingly, our competitors may commercialize products more rapidly or
effectively than we do, which could hurt our competitive position.

IF OUR LICENSORS TERMINATE THEIR AGREEMENTS WITH US, WE COULD LOSE OUR RIGHTS TO
OUR DRUG CANDIDATES.

     We have licensed our drug candidates under agreements with our licensors.
These agreements permit our licensors to terminate the agreements in
circumstances such as our failure to achieve development milestones or the
occurrence of an uncured material breach by us. The termination of any of these
agreements would result in the loss of our rights to a drug candidate. On the
termination of most of our license agreements, we are required to return the
licensed technology to our licensors. In addition, most of these agreements
provide that we generally must reimburse our licensors for the costs they incur
in performing any patent prosecution activities such as litigation, patent
conflict, patent opposition or other actions, for the technology licensed to us.
We believe that these costs as well as other costs under our license agreements
will be substantial and may increase significantly during the next several
years. Our inability or failure to pay any of these costs with respect to any
drug candidate could result in the termination of the license agreement for the
drug candidate.

IF WE ARE NOT ABLE TO SUCCESSFULLY MANUFACTURE OUR DRUG CANDIDATES, OUR BUSINESS
MAY NEVER ACHIEVE PROFITABILITY.

     We do not have any internal manufacturing capacity and we rely on third
party manufacturers for the manufacture of all of our clinical trial and
commercial material. We plan to use our existing relationships and to establish
relationships with additional third party manufacturers for products that we
develop. For instance, Abbott has agreed to manufacture an initial quantity of
Coviracil, assist us in the transfer of the Coviracil manufacturing process to
another third party and provide extended manufacturing capability for Coviracil
upon our request. We will need to enter into other arrangements with third party
manufacturers for future production of products. We may be unable to establish
or maintain relationships with manufacturers on acceptable terms, and
manufacturers may be unable to manufacture products in commercial quantities on
a cost effective basis for all of our products. Our

                                       24
<Page>

dependence on third parties for the manufacture of our products may adversely
affect our profit margins and our ability to develop and commercialize products
on a timely and competitive basis. Further, third party manufacturers may
encounter manufacturing or quality control problems in manufacturing our
products and may be unable to maintain the necessary governmental licenses and
approvals to continue manufacturing our products.

BECAUSE WE NEED TO ESTABLISH OR OBTAIN ADDITIONAL SALES AND MARKETING RESOURCES
AND CAPABILITIES, WE MAY BE UNABLE TO SUCCESSFULLY MARKET, SELL OR DISTRIBUTE
PRODUCTS WE DEVELOP.

     We do not have an established sales force to market and distribute any
products we successfully develop. We will have to develop a sales force and/or
rely on arrangements with third parties for the marketing, distribution and sale
of our products. We may be unable to establish marketing or sales capabilities
sufficient to successfully commercialize our products or to enter into new
arrangements with third parties to perform those activities on favorable terms.
In addition, third parties may have significant control or influence over
important aspects of the commercialization of our drug candidates, including
market identification, marketing methods, pricing, composition of sales force
and promotional activities. We may have limited control over the amount and
timing of resources that a third party devotes to our products and may be unable
to prevent any third party from pursuing alternative products that could result
in the development of products that compete with our products, or their withdraw
of support for our programs. Further, any internal capabilities or third party
arrangements may not be successful. Our business may never achieve profitability
if we fail to establish or maintain a sales force and marketing, sales and
distribution capabilities.

BECAUSE WE DEPEND ON THIRD PARTIES FOR THE DISCOVERY AND DEVELOPMENT OF DRUG
CANDIDATES, WE MAY NOT SUCCESSFULLY ACQUIRE ADDITIONAL DRUG CANDIDATES OR
DEVELOP OUR CURRENT DRUG CANDIDATES.

     We do not currently intend to engage in drug discovery. Our strategy for
obtaining additional drug candidates is to utilize the relationships of our
management team and scientific consultants to identify drug candidates for
in-licensing from companies, universities, research institutions and other
organizations. We may not succeed in acquiring additional drug candidates on
acceptable terms or at all.

     Because we have engaged and intend to continue to engage third party
contract research organizations and other third parties to help us develop our
drug candidates, many important aspects of our drug development programs have
been and will continue to be outside of our direct control. In addition, the
contract research organizations may not perform all of their obligations under
arrangements with us. If the contract research organizations do not perform
clinical trials in a satisfactory manner or breach their obligations to us, the
development and commercialization of any drug candidate may be delayed or
precluded.

BECAUSE WE MAY NOT BE ABLE TO ATTRACT AND RETAIN KEY PERSONNEL AND ADVISORS, WE
MAY NOT SUCCESSFULLY DEVELOP OUR DRUG CANDIDATES OR ACHIEVE OUR OTHER BUSINESS
OBJECTIVES.

     We are highly dependent on our senior management and scientific staff. The
loss of the services of any member of our senior management or scientific staff
may significantly delay or prevent the achievement of product development and
other business objectives. In order to pursue our drug development programs and
marketing plans, we will need to hire additional qualified scientific and
management personnel. Competition for qualified individuals is intense and we
face competition from numerous pharmaceutical and biotechnology companies,
universities and other research institutions. If we are not able to attract and
retain these individuals we may not be able to successfully commercialize our
drug candidates. Under our amended and restated agreement with Chris A. Rallis,
our President and Chief Operating Officer, Mr. Rallis has agreed to remain with
us until December 31, 2002.

HEALTH CARE REFORM MEASURES AND THIRD PARTY REIMBURSEMENT PRACTICES ARE
UNCERTAIN AND MAY DELAY OR PREVENT THE COMMERCIALIZATION OF OUR DRUG CANDIDATES.

     The efforts of governments and third party payors to contain or reduce the
cost of health care will continue to affect the business and financial condition
of drug companies. A number of legislative and regulatory proposals to change
the health care system have been considered in recent years. In addition, an
increasing emphasis on managed care in the United States has and will continue
to increase pressure on drug pricing. Legislative or regulatory proposals or
changes in managed care systems may be adopted that may have a negative effect
on our

                                       25
<Page>

business. The announcement and/or adoption of proposals could have an adverse
effect on our ability to raise capital and earn profits. Sales of prescription
drugs depend significantly on the availability of reimbursement to the consumer
from third party payors, such as government and private insurance plans. These
third party payors frequently require that drug companies give them
predetermined discounts from list prices, and they are increasingly challenging
the prices for medical products and services. Present combination treatment
regimens for the treatment of HIV are expensive and costs may increase as new
combinations are developed. These costs have resulted in limitations in the
reimbursement available from third party payors for the treatment of HIV
infection, and we expect these limitations will continue in the future. Third
party payors may not consider products we may bring to the market cost effective
and may not reimburse the consumer sufficiently to allow us to sell our products
on a profitable basis.

IF OUR DRUG CANDIDATES DO NOT ACHIEVE MARKET ACCEPTANCE, OUR BUSINESS MAY NEVER
ACHIEVE PROFITABILITY.

     Our success will depend on the market acceptance of any products we
develop. The degree of market acceptance will depend on a number of factors,
including:

     -    the receipt and scope of regulatory approvals,
     -    the establishment and demonstration in the medical community of the
          safety and effectiveness of our products and their potential
          advantages over existing treatment methods, and
     -    reimbursement policies of government and third party payors.

     Physicians, patients, payors or the medical community in general may not
accept or utilize any product that we may develop.

WE MAY NOT HAVE ADEQUATE INSURANCE PROTECTION AGAINST PRODUCT LIABILITY.

     Our business exposes us to potential product liability risks that are
inherent in the testing of drug candidates and the manufacturing and marketing
of drug products and we may face product liability claims in the future. We
currently have only limited product liability insurance. We may be unable to
maintain our existing insurance and/or obtain additional insurance in the future
at a reasonable cost or in sufficient amounts to protect against potential
losses. A successful product liability claim or series of claims brought against
us could require us to pay substantial amounts that would decrease our
profitability.

WE MAY INCUR SUBSTANTIAL COSTS RELATED TO OUR USE OF HAZARDOUS MATERIALS.

     We use hazardous materials, chemicals, viruses and various radioactive
compounds in our drug development programs. Although we believe that our
handling and disposing of these materials comply with state and federal
regulations, the risk of accidental contamination or injury still exists. We
could be held liable for any damages or fines that result from any accidental
contamination or injury and the liability could exceed our resources.

OUR CONTROLLING STOCKHOLDERS MAY MAKE DECISIONS YOU DO NOT CONSIDER TO BE IN
YOUR BEST INTEREST.

     As of September 30, 2002, our directors, executive officers and their
affiliates, excluding Warburg Pincus Private Equity VIII, L.P., Warburg Pincus,
owned approximately 11.0% of our outstanding common stock. Warburg Pincus owned
approximately 30.4% of our outstanding common stock. In addition, Abbott owned
approximately 10.3% of our outstanding common stock. For so long as Warburg
Pincus continues to own at least 5,846,222 shares of our common stock and at
least 10% of our outstanding common stock, Warburg Pincus has the right to
participate in any sales of equity securities by Triangle, other than sales in
connection with a registered underwritten offering, a merger or similar
transaction or a stock option or similar plan, in proportion to the percentage
of all outstanding securities of Triangle held by Warburg Pincus at the time of
the transaction. Warburg Pincus has the right to designate two people to serve
as members of our board of directors. As a result, our controlling stockholders
are able to significantly influence all matters requiring stockholder approval,
including the election of directors and the approval of significant corporate
transactions. This concentration of ownership could also delay or prevent a
change in control of Triangle that may be favored by other stockholders.

                                       26
<Page>

THE MARKET PRICE OF OUR STOCK MAY FALL AS A RESULT OF MARKET VOLATILITY AND
FUTURE DEVELOPMENTS IN OUR INDUSTRY.

     The market price of our common stock is likely to be volatile and could
fluctuate widely in response to many factors, including:

     -    announcements of the results of clinical trials by us or our
          competitors,
     -    announcements of the timing of regulatory submissions and/or approvals
          by us or our competitors,
     -    developments with respect to patents or proprietary rights,
     -    announcements of technological innovations by us or our competitors,
     -    announcements of new products or new contracts by us or our
          competitors,
     -    actual or anticipated variations in our operating results, including
          targeted cash usage, due to the level of development expenses and
          other factors,
     -    changes in financial estimates by securities analysts and whether our
          earnings meet or exceed analysts' estimates,
     -    conditions and trends in the pharmaceutical and other industries,
     -    new accounting standards,
     -    general economic, political and market conditions and other factors,
     -    low transaction volume due to high concentrations of ownership, and
     -    the occurrence of any of the risks described in these "Risk and
          Uncertainties."

     In the past, following periods of volatility in the market price of the
securities of companies in our industry, securities class action law suits have
often been brought against those companies. If we face litigation in the future,
it would result in substantial costs and a diversion of management attention and
resources, which would negatively impact our business.

APPROXIMATELY 35,000,000 SHARES OF OUR COMMON STOCK MAY BE SOLD WITHOUT
RESTRICTION AND APPROXIMATELY 35,300,000 SHARES ARE REGISTERED FOR SALE. SALES
OF A LARGE NUMBER OF OUR SHARES MAY CAUSE OUR STOCK PRICE TO FALL EVEN IF OUR
BUSINESS IS DOING WELL.

     If our stockholders sell a substantial number of shares of our common stock
in the public market, the market price of our common stock could decline. As of
September 30, 2002, there were 76,903,883 shares of common stock outstanding, of
which approximately 35,000,000 were immediately eligible for resale in the
public market without restriction. Holders of approximately 41,900,000 shares
have rights to cause us to register their shares for sale to the public. We have
filed registration statements to register the sale of approximately 35,300,000
of these shares.

     Declines in our stock price might harm our ability to issue equity or
secure other types of financing arrangements. The price at which we issue shares
is generally based on the market price of our common stock and a decline in our
stock price would result in our needing to issue a greater number of shares to
raise a given amount of funds or acquire a given amount of goods or services.
For this reason, a decline in our stock price might also result in increased
ownership dilution to our stockholders.

PROVISIONS IN OUR CHARTER DOCUMENTS AND DELAWARE LAW COULD DELAY OR PREVENT A
CHANGE IN MANAGEMENT OR A TAKEOVER ATTEMPT THAT YOU CONSIDER TO BE IN YOUR BEST
INTEREST.

     We have adopted a number of provisions that could deter an acquisition of
Triangle which was not approved by our board of directors. We have adopted a
preferred stock purchase rights plan, commonly referred to as a "poison pill."
The rights plan is intended to deter an attempt to acquire Triangle in a manner
or on terms not approved by the board of directors. The rights plan will not
prevent an acquisition of Triangle which is approved by the board of directors.
Our charter authorizes the board of directors to determine the terms of any
shares of undesignated preferred stock and issue them without stockholder
approval. The issuance of preferred stock may make it more difficult for a third
party to acquire, or may discourage a third party from acquiring, voting control
of Triangle.

                                       27
<Page>

     Provisions in our charter and bylaws, as well as some provisions of
Delaware law could delay or prevent the removal of incumbent directors and could
make more difficult a merger, tender offer or proxy contest involving Triangle,
even if the events could be beneficial to our stockholders. For example, our
bylaws divide the board of directors into three classes of directors with each
class serving a three-year term, stockholders may not call a special meeting,
and vacancies on the board of directors may only be filled by a vote of the
directors then in office. These provisions could also limit the price that
investors might be willing to pay for our common stock.

                                       28
<Page>

ITEM 3. QUANTITATIVE AND QUALITATIVE DISCLOSURES ABOUT MARKET RISK

     Triangle is exposed to various market risks, including changes in foreign
currency exchange rates, investment market value and interest rates. Market risk
is the potential loss arising from adverse changes in market rates and prices,
such as foreign currency exchange and interest rates. We may enter into forward
foreign currency contracts or purchase investments in foreign currencies to
hedge foreign currency commitments. We have, however, established policies and
procedures for market risk assessment and the approval, reporting and monitoring
of derivative financial instrument activities. The following discusses our
exposure to risks related to changes in interest rates, foreign currency
exchange rates and investment market value.

INTEREST RATE SENSITIVITY

     We are subject to interest rate risk on our investment portfolio. We
maintain an investment portfolio consisting primarily of high quality money
market instruments, and government and corporate bonds. Our portfolio has a
current average maturity of less than 12 months. We attempt to mitigate default
risk by investing in high credit quality securities and by monitoring the credit
rating of investment issuers. Our investment portfolio includes only marketable
securities with active secondary or resale markets to help ensure portfolio
liquidity and we have implemented guidelines limiting the duration of
investments. These available-for-sale securities are subject to interest rate
risk and will decrease in value if market interest rates increase. If market
rates were to increase by 10 percent from levels at September 30, 2002, we
expect that the fair value of our investment portfolio would decline by an
immaterial aggregate amount primarily due to the relatively short maturity of
the portfolio. At September 30, 2002, our portfolio consisted of approximately
$25.6 million of investments maturing within one year and approximately $5.0
million of investments maturing after one year but within 30 months.
Additionally, we generally have the ability to hold our fixed income investments
to maturity and therefore do not expect that our consolidated operating results,
financial position or cash flows will be affected by a significant amount due to
a sudden change in interest rates.

FOREIGN CURRENCY EXCHANGE RISK

     The majority of our transactions occur in U.S. dollars and we do not have
significant subsidiaries or investments in foreign countries. Therefore, we are
not subject to significant foreign currency exchange risk. We have, however,
established policies and procedures for market risk assessment, including a
foreign currency-hedging program. The goal of our hedging program is to
establish fixed exchange rates on firm foreign currency cash outflows and to
minimize the impact to us of foreign currency fluctuations. These policies
specifically provide for the hedging of firm commitments and prohibit the
holding of derivative instruments for speculative or trading purposes. At
September 30, 2002, we had no forward foreign currency contracts, but had
investments in foreign currencies totaling approximately $265,000 used to hedge
foreign currency commitments. The purchase and the holding of foreign currencies
are governed by established corporate policies and procedures and are entered
into when management determines this methodology to be in our best interests.
These investments are subject to both foreign currency risk and interest rate
risk. The hypothetical loss associated with a 10 percent devaluation of these
foreign currencies would not materially affect our consolidated operating
results, financial position or cash flow.

STRATEGIC INVESTMENT RISK

     In addition to our normal investment portfolio, we have a strategic
investment in Dynavax valued at $1.0 million. This investment represents
unregistered preferred stock and is subject to higher investment risk than our
normal investment portfolio due to the lack of an active resale market for the
investment.

                                       29
<Page>

ITEM 4. CONTROLS AND PROCEDURES

     Based on our most recent evaluation, which was completed within 90 days of
the filing of this Form 10-Q, Triangle's Chief Executive Officer and Chief
Financial Officer believe our disclosure controls and procedures (as defined in
Rules 13a-14 and 15d-14 of the Securities Exchange Act of 1934, as amended) are
effective. There have been no significant changes in internal controls or in
other factors that could significantly affect these controls subsequent to the
date of the most recent evaluation of our internal controls, including any
corrective actions with regard to significant deficiencies and material
weaknesses.

                                       30
<Page>

                           PART II - OTHER INFORMATION

ITEM 1. LEGAL PROCEEDINGS

     On May 31, 2002, Emory, GlaxoSmithKline and Shire settled patent disputes
involving lamivudine and Coviracil. Under the terms of the settlement, Emory
received an exclusive license from Shire under Shire's patents relating to
Coviracil and methods for its use and manufacture, and Shire and GlaxoSmithKline
received exclusive licenses under Emory's patents relating to lamivudine. Under
the terms of our license agreement with Emory, we automatically acquired an
exclusive sublicense to the Shire patents relating to Coviracil granted under
the terms of the settlement, thereby resolving all previously pending patent
disputes regarding Coviracil.

     On August 30, 2002, we resolved our patent disputes involving amdoxovir
with Shire. Under the terms of the settlement, Emory and the University of
Georgia received an exclusive license to Shire's patent rights covering
amdoxovir and methods for its use and manufacture. Under the terms of this
license agreement, Triangle acquired an exclusive sublicense to these rights in
exchange for an obligation to pay Shire an incremental royalty on future
amdoxovir sales. Under the settlement agreement, Emory, University of Georgia
and Triangle granted Shire an exclusive license under their patent rights to
BCH-13520 and methods for its use and manufacture.

ITEM 4. SUBMISSION OF MATTERS TO A VOTE OF SECURITY HOLDERS

a.   A Special Meeting of the Stockholders of Triangle Pharmaceuticals, Inc.,
     the Meeting, was held on September 20, 2002. The holders of 58,764,742 of
     the 76,861,837 shares of our common stock outstanding on the record date
     were present at the Meeting in person or by proxy.

b.   At the Meeting, a proposal to approve an amendment to the 1996 Stock
     Incentive Plan was approved. The proposal included amendments to our 1996
     Stock Incentive Plan (i) increasing the number of shares of common stock
     authorized for issuance under the plan by 3,000,000 shares and (ii)
     increasing the number of options, stock appreciation rights and stock
     issuances which may be granted to any one person in the aggregate per
     calendar year to 1,500,000. The number of votes cast for, against and to
     abstain on the proposal are indicated below:

<Table>
<Caption>
        FOR                AGAINST            ABSTENTIONS
     ----------           ---------           -----------
     <S>                  <C>                   <C>
     48,714,898           9,968,496             81,348
</Table>

                                       31
<Page>

ITEM 6.  EXHIBITS AND REPORTS ON FORM 8-K

a.   Exhibits

     +10.1  Amended and Restated License Agreement between Dynavax Technologies
Corporation and Triangle Pharmaceuticals, Inc. dated September 25, 2002.

     +10.2  Second Amendment to License Agreement among Emory University,
University of Georgia Research Foundation, Inc. and Triangle Pharmaceuticals,
Inc. dated August 30, 2002.

b.   Reports on Form 8-K

     On July 31, 2002, we filed a current report on Form 8-K announcing the
reacquisition of product rights from Abbott Laboratories and the results from
our Phase III trial (FTC-301) for Coviracil (emtricitabine) for the treatment of
HIV disease.

     On August 6, 2002, we filed a current report on Form 8-K announcing the
appointment of Daniel G. Welch as Chairman and Chief Executive Officer.

     On August 13, 2002, we filed a current report on Form 8-K announcing our
second quarter financial results.

     On August 13, 2002, we furnished a current report on Form 8-K pursuant to
Regulation FD announcing our CEO/CFO certifications pursuant to the
Sarbanes-Oxley Act. This report shall not be deemed to be incorporated by
reference into this Form 10-Q or filed hereunder for purposes of liability under
the Securities Exchange Act of 1934.

     On August 28, 2002, we filed a current report on Form 8-K disclosing the
execution of a Stock Voting Agreement.

     On September 19, 2002, we filed a current report on Form 8-K disclosing the
execution of a Third Amendment to License Agreement with Bukwang Pharm. Co. Ltd,
a Termination Agreement with Abbott Laboratories, a Supply and Manufacturing
Agreement with Abbott Laboratories and a Settlement and Exclusive License
Agreement with Shire Biochem Inc., Shire Pharmaceuticals Group plc, Emory
University and the University of Georgia Research Foundation, Inc.

     On September 23, 2002, we filed a current report on Form 8-K disclosing the
execution of an Amended and Restated Employment Agreement with Chris A. Rallis
and the execution of a Third Amendment to Triangle Pharmaceuticals, Inc. 1996
Incentive Plan.

     On September 24, 2002, we filed a current report on Form 8-K announcing the
submission of an NDA for Coviracil for the treatment of HIV disease.

+         Certain confidential portions of this Exhibit were omitted by means of
          marking such portions with an asterisk (the "Mark"). This Exhibit has
          been filed separately with the Secretary of the SEC without the Mark
          pursuant to the Company's Application Requesting Confidential
          Treatment under Rule 24b-2 under the Securities Exchange Act of 1934.

                                       32
<Page>

                         TRIANGLE PHARMACEUTICALS, INC.
                                   SIGNATURES

     Pursuant to the requirements of the Securities Exchange Act of 1934, the
Registrant has duly caused this Quarterly Report on Form 10-Q to be signed on
its behalf by the undersigned, thereunto duly authorized.

                                    TRIANGLE PHARMACEUTICALS, INC.

Date: November 8, 2002                     By: /s/ Daniel G. Welch
                                               ------------------------------
                                           Daniel G. Welch
                                           Chairman and Chief Executive Officer


                                    TRIANGLE PHARMACEUTICALS, INC.


Date: November 8, 2002                     By: /s/ Robert F. Amundsen, Jr.
                                               -----------------------------
                                           Robert F. Amundsen, Jr.
                                           Executive Vice President and
                                           Chief Financial Officer

                                       33
<Page>

                                 CERTIFICATIONS

I, Daniel G. Welch certify that:

1.   I have reviewed this quarterly report on Form 10-Q of Triangle
     Pharmaceuticals, Inc.;

2.   Based on my knowledge, this quarterly report does not contain any untrue
     statement of a material fact or omit to state a material fact necessary to
     make the statements made, in light of the circumstances under which such
     statements were made, not misleading with respect to the period covered by
     this quarterly report;

3.   Based on my knowledge, the financial statements, and other financial
     information included in this quarterly report, fairly present in all
     material respects the financial condition, results of operations and cash
     flows of the registrant as of, and for, the periods presented in this
     quarterly report;

4.   The registrant's other certifying officers and I are responsible for
     establishing and maintaining disclosure controls and procedures (as defined
     in Exchange Act Rules 13a-14 and 15d-14) for the registrant and we have:

     a.   designed such disclosure controls and procedures to ensure that
          material information relating to the registrant, including its
          consolidated subsidiaries, is made known to us by others within those
          entities, particularly during the period in which this quarterly
          report is being prepared;

     b.   evaluated the effectiveness of the registrant's disclosure controls
          and procedures as of a date within 90 days prior to the filing date of
          this quarterly report (the "Evaluation Date"); and

     c.   presented in this quarterly report our conclusions about the
          effectiveness of the disclosure controls and procedures based on our
          evaluation as of the Evaluation Date;

5.   The registrant's other certifying officers and I have disclosed, based on
     our most recent evaluation, to the registrant's auditors and the audit
     committee of registrant's board of directors:

     a.   all significant deficiencies in the design or operation of internal
          controls which could adversely affect the registrant's ability to
          record, process, summarize and report financial data and have
          identified for the registrant's auditors any material weaknesses in
          internal controls; and

     b.   any fraud, whether or not material, that involves management or other
          employees who have a significant role in the registrant's internal
          controls; and

6.   The registrant's other certifying officers and I have indicated in this
     quarterly report whether or not there were significant changes in internal
     controls or in other factors that could significantly affect internal
     controls subsequent to the date of our most recent evaluation, including
     any corrective actions with regard to significant deficiencies and material
     weaknesses.

Date: November 8, 2002


                                           /s/ Daniel G. Welch
                                           ------------------------------
                                           Daniel G. Welch
                                           Chairman of the Board and
                                           Chief Executive Officer

                                       34
<Page>

I, Robert F. Amundsen, Jr., certify that:

1.   I have reviewed this quarterly report on Form 10-Q of Triangle
     Pharmaceuticals, Inc.;

2.   Based on my knowledge, this quarterly report does not contain any untrue
     statement of a material fact or omit to state a material fact necessary to
     make the statements made, in light of the circumstances under which such
     statements were made, not misleading with respect to the period covered by
     this quarterly report;

3.   Based on my knowledge, the financial statements, and other financial
     information included in this quarterly report, fairly present in all
     material respects the financial condition, results of operations and cash
     flows of the registrant as of, and for, the periods presented in this
     quarterly report;

4.   The registrant's other certifying officers and I are responsible for
     establishing and maintaining disclosure controls and procedures (as defined
     in Exchange Act Rules 13a-14 and 15d-14) for the registrant and we have:

     a.   designed such disclosure controls and procedures to ensure that
          material information relating to the registrant, including its
          consolidated subsidiaries, is made known to us by others within those
          entities, particularly during the period in which this quarterly
          report is being prepared;

     b.   evaluated the effectiveness of the registrant's disclosure controls
          and procedures as of a date within 90 days prior to the filing date of
          this quarterly report (the "Evaluation Date"); and

     c.   presented in this quarterly report our conclusions about the
          effectiveness of the disclosure controls and procedures based on our
          evaluation as of the Evaluation Date;

5.   The registrant's other certifying officers and I have disclosed, based on
     our most recent evaluation, to the registrant's auditors and the audit
     committee of registrant's board of directors:

     a.   all significant deficiencies in the design or operation of internal
          controls which could adversely affect the registrant's ability to
          record, process, summarize and report financial data and have
          identified for the registrant's auditors any material weaknesses in
          internal controls; and

     b.   any fraud, whether or not material, that involves management or other
          employees who have a significant role in the registrant's internal
          controls; and

6.   The registrant's other certifying officers and I have indicated in this
     quarterly report whether or not there were significant changes in internal
     controls or in other factors that could significantly affect internal
     controls subsequent to the date of our most recent evaluation, including
     any corrective actions with regard to significant deficiencies and material
     weaknesses.

Date: November 8, 2002


                                           /s/ Robert F. Amundsen, Jr.
                                           --------------------------------
                                           Robert F. Amundsen, Jr.
                                           Executive Vice President and
                                           Chief Financial Officer

                                       35