CEGE Cell Genesys (MM)

As filed with the Securities and Exchange Commission on October 14, 2009

Registration No. 333-29551

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

POST-EFFECTIVE AMENDMENT NO. 1

TO

FORM S-8

REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933

Cell Genesys, Inc.

(Exact Name of Registrant as Specified in Its Charter)

400 Oyster Point Boulevard, Suite 525

South San Francisco, California 94080

(650) 266-3000

(Address of Registrant’s Principal Executive Office) (Zip Code)

Merlin Pharmaceutical Corporation 1993 Stock Option Plan

(Full title of the plan)

Stephen M. Simes

Vice Chairman, President and Chief Executive Officer

BioSante Pharmaceuticals, Inc.

111 Barclay Boulevard

Lincolnshire, Illinois  60069

(847) 478-0500

 (Name and Address, Including Zip Code, and Telephone Number, Including Area Code, of Agent For Service)

Copies requested to:

Amy E. Culbert, Esq.

Oppenheimer Wolff & Donnelly LLP

45 South Seventh Street, Suite 3300

Minneapolis, Minnesota 55402-1509

(612) 607-7287

DEREGISTRATION OF SECURITIES

On June 19, 1997, Cell Genesys, Inc., a Delaware corporation (“Cell Genesys”), filed with the Securities and Exchange Commission a registration statement on Form S-8 (Registration No. 333-29551) (the “Registration Statement”) registering the sale of up to 66,941 shares of common stock, par value $0.001 per share, of Cell Genesys pursuant to the Merlin Pharmaceutical Corporation 1993 Stock Option Plan.

On October 14, 2009, Cell Genesys was merged with and into BioSante Pharmaceuticals, Inc., a Delaware corporation (“BioSante”), with BioSante continuing as the surviving company (the “Merger”). The Merger was effectuated pursuant to the terms of an Agreement and Plan of Merger, dated as of June 29, 2009, by and between Cell Genesys and BioSante.

As a result of the Merger, the offering pursuant to the Registration Statement has been terminated. In accordance with undertakings made by Cell Genesys in the Registration Statement to remove from registration, by means of a post-effective amendment, any of the securities which remain unsold at the termination of the offering, Cell Genesys hereby removes from registration the Cell Genesys common stock registered but unsold under the Registration Statement.

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SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, the registrant certifies that it has reasonable grounds to believe that it meets all of the requirements for filing on Form S-8 and has duly caused this Post-Effective Amendment No. 1 to the Registration Statement on Form S-8 to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Lincolnshire, State of Illinois, on October 14, 2009.

Pursuant to the requirements of the Securities Act of 1933, this Post-Effective Amendment No. 1 to the Registration Statement on Form S-8 has been signed on October 14, 2009, by the following persons in the capacities indicated.

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