<Page> UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported) AUGUST 13, 2002 TRIANGLE PHARMACEUTICALS, INC. (Exact name of registrant as specified in its charter) <Table> DELAWARE 000-21589 56-1930728 (State or other jurisdiction (Commission (IRS Employer of incorporation) File Number) Identification No.) 4 UNIVERSITY PLACE, 4611 UNIVERSITY DRIVE, DURHAM, NORTH CAROLINA 27707 (Address of principal executive offices) (Zip Code) </Table> Registrant's telephone number, including area code (919) 493-5980 (Former name or former address, if changed since last report) <Page> Item 7. Financial Statements and Exhibits. (c) Exhibits. The following document is incorporated by reference to this Report: 99.1 Officer Certifications dated August 13, 2002 pursuant to the Sarbanes-Oxley Act of 2002. Item 9. Regulation FD Disclosure. In accordance with General Instruction B.2. of Form 8-K, the following information shall not be deemed "filed" for purposes of Section 18 of the Securities Exchange Act of 1934, as amended, nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933, as amended. On August 13, 2002, the President and Chief Operating Officer and the Treasurer of Triangle Pharmaceuticals, Inc. submitted to the Securities and Exchange Commission certifications pursuant to the Sarbanes-Oxley Act of 2002 in connection with the Form 10-Q of Triangle Pharmaceuticals, Inc. for the period ended June 30, 2002. Copies of these certifications are attached hereto as Exhibit 99.1 SIGNATURES Pursuant to the requirements of the Securities Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized. Triangle Pharmaceuticals, Inc. ------------------------------ (Registrant) August 13, 2002 /s/ Chris A. Rallis --------------- ------------------------------ Date (Signature) Name: Chris A. Rallis Title: President & Chief Operating Officer