1 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: May 8, 2000 Commission File Number: 0-18976 CELTRIX PHARMACEUTICALS, INC. (Exact name of registrant as specified in its charter) DELAWARE 94-3121462 (State or other jurisdiction of (I.R.S. Employer Identification No.) incorporation or organization) 2033 Gateway Place, Suite 600, San Jose, CA 95110 (Address of principal executive offices and zip code) Registrant's Telephone Number: (408) 988-2500 2 ITEM 5. OTHER EVENTS On May 8, 2000, Celtrix Pharmaceuticals, Inc., a Delaware corporation (the "Company") announced Celtrix and Insmed Pharmaceuticals Mail Proxy Statements for Merger. Further details regarding this announcement are contained in the Company's news release dated May 8, 2000, attached as exhibit hereto and incorporated by reference herein. ITEM 7. FINANCIAL STATEMENTS, PRO FORMA FINANCIAL INFORMATION AND EXHIBITS (a) EXHIBITS Exhibit 21 Celtrix Pharmaceuticals, Inc. News Release dated May 8, 2000. 3 SIGNATURES Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized. CELTRIX PHARMACEUTICALS, INC. (Registrant) Date: May 8, 2000 By: /s/ DONALD D. HUFFMAN ------------------------------------------ Donald D. Huffman Vice President, Finance & Administration Chief Financial Officer (Duly authorized principal financial and accounting officer.) 4 CELTRIX PHARMACEUTICALS, INC. INDEX TO EXHIBITS Exhibit Number - -------------- Exhibit 21 Celtrix Pharmaceuticals, Inc. Press Release dated May 8, 2000.