PRESS RELEASE: Threshold Pharmaceuticals's Lung Cancer Study Does Not Meet Goal

Threshold Pharmaceuticals's Lung Cancer Study Does Not Meet Goal

REDDWOOD CITY, Calif., Oct. 11 -- Threshold Pharmaceuticals, Inc. , today announced that, as part of a planned interim analysis, it would stop enrollment in a Phase 2 clinical trial evaluating the efficacy and safety of glufosfamide in patients with recurrent, sensitive small cell lung cancer.

The clinical trial utilized a two stage design to ensure there would be an adequate response rate to justify complete enrollment. Tumor response was evaluated at baseline and every six weeks using the Response Evaluation Criteria In Solid Tumors (RECIST). The first stage enrolled 21 patients as planned, but only one confirmed partial response was observed. If three or more responses were observed, an additional 29 patients would have been enrolled. Patients currently enrolled in the clinical trial will be given the option to continue in the trial.

"We are disappointed in the study results. While we recognize that response is not a perfect surrogate for survival, the low response rate indicates that glufosfamide is not sufficiently effective as a single agent for patients with small cell lung cancer. We had hoped to develop a better treatment option for patients with this disease, for whom the quality of life and treatment outcomes need improvement," said Barry Selick, Ph.D., chief executive officer of Threshold. "We want to thank the investigators, patients and their families for their participation in the study."

Phase 2 Clinical Trial Design

Approximately 50 patients with extensive recurrent sensitive small cell lung cancer, who had progressed at least 60 days after completing chemotherapy, were planned to enroll in the Phase 2, open-label, clinical trial at various sites in the United States, Ukraine and Russia. All patients were to receive glufosfamide every three weeks for up to six cycles. The study utilized a Simon two-stage design which was designed to stop development if the true response rate was 10% or less and to continue development if the true response rate was 25% or higher.

The primary efficacy endpoint of the trial was objective response rate. The secondary endpoints of the trial evaluated duration of response, progression-free survival, overall survival and various safety and pharmacokinetic parameters. The study also evaluated the effects of glufosfamide on lung cancer symptoms utilizing the Lung Cancer Symptom Scale (LCSS).

About Small Cell Lung Cancer

The National Cancer Institute estimates that 174,470 people were diagnosed with lung cancer in the United States in 2006, and approximately 160,000 people will die each year from the disease. Small cell lung cancer is less common than non-small cell lung cancer. About 15 to 20 percent of all lung cancers are the small cell type. This cancer usually starts in the bronchi near the center of the chest but has often spread outside of the lung by the time of diagnosis. Small cell lung cancer is strongly associated with a history of cigarette smoking.

About Threshold Pharmaceuticals

Threshold is a biotechnology company focused on the discovery and development of small molecule therapeutics for the potential treatment of cancer. By selectively targeting abnormally-proliferating tumor cells, the Company's drug candidates are designed to be potentially more effective and less toxic to healthy tissues than conventional treatments. For additional information, please visit our website (http://www.thresholdpharm.com).

Forward-Looking Statements

Except for statements of historical fact, the statements in this press release are forward-looking statements, including statements regarding Threshold's product candidates, clinical trial progress and results, and potential therapeutic uses and benefits of our product candidates. These statements involve risks and uncertainties that can cause actual results to differ materially from those in such forward-looking statements. Potential risks and uncertainties include, but are not limited to, Threshold's ability to commence, enroll or complete its anticipated clinical trials, the time and expense required to conduct such clinical trials and analyze data, issues arising in the regulatory or manufacturing process and the results of such clinical trials (including product safety issues and efficacy results). Further information regarding these and other risks is included under the heading "Risk Factors" in Threshold's Quarterly Report on Form 10-Q, which was filed with the Securities Exchange Commission on August 7, 2007 and is available from the SEC's website (http://www.sec.gov) and on our website (http://www.thresholdpharm.com) under the heading "Investors." We do not intend to update any forward-looking statement made in this news release.

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