Threshold Files Registration Statement for Follow-On Offering

Market Wire, September, 2005

Threshold Pharmaceuticals, Inc. (NASDAQ: THLD) today announced that it has filed a registration statement with the Securities and Exchange Commission covering a proposed offering of 6,250,000 shares of its common stock. The Company and selling stockholders intend to grant the underwriters the option to purchase, within 30 days from the date of the prospectus, up to an additional 937,500 shares of common stock to cover over-allotments, if any. Morgan Stanley will act as sole-bookrunning manager, and CIBC World Markets Corp. and Lazard Capital Markets will act as co-managers of the offering.

The offering will be made only by means of a prospectus. When available, copies of the preliminary prospectus relating to the offering may be obtained from Morgan Stanley by email at prospectus@morganstanley.com, by fax at 212-761-0211 and from the Prospectus Department at Morgan Stanley (1585 Broadway, New York, New York 10036, 212-761-6775).

A registration statement relating to these securities has been filed with the Securities and Exchange Commission, but has not yet become effective. These securities may not be sold nor may offers to buy be accepted prior to the time the registration statement becomes effective. This press release shall not constitute an offer to sell or the solicitation of an offer to buy, nor shall there be any sale of these securities in any state in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such state.

About Threshold Pharmaceuticals

Threshold is a biotechnology company focused on the discovery, development and commercialization of small molecule therapeutics based on Metabolic Targeting, an approach that targets fundamental differences in energy metabolism between normal and certain diseased cells. Threshold is building a pipeline of drug candidates that are designed to selectively target tumor cells and abnormally proliferating cells so that the drugs are efficacious and less toxic to healthy tissues than conventional drugs. Threshold's initial clinical focus is the treatment of benign prostatic hyperplasia, or BPH, a disease characterized by overgrowth of the prostate, and the treatment of cancer. For additional information, please visit http://www.thresholdpharm.com.

Media Contact Information: Kim Paone Access Communications 917-522-3528 Email Contact Investor Contact Information Denise Powell Threshold Pharmaceuticals 650-474-8206 Email Contact