Threshold Pharmaceuticals, Inc. Announces Data Safety Monitoring Board Recommends Glufosfamide Phase 3 Clinical Trial Continue To Completion

REDWOOD CITY, Calif., June 1 /PRNewswire-FirstCall/ -- Threshold Pharmaceuticals, Inc. , today announced that the Independent Data Monitoring Committee (IDMC) recently evaluated the data collected to date from the Company’s ongoing pivotal phase 3 clinical trial of glufosfamide for the second-line treatment of patients with metastatic pancreatic cancer. The IDMC concluded that the trial can continue to completion.

For the planned interim analysis the IDMC could have recommended stopping the trial early if there were major safety concerns in the glufosfamide arm. After reviewing the interim data the IDMC recommended to continue the study to completion.

“This is an important milestone in the development of this novel therapy,” said Alan Colowick, M.D., chief medical officer at Threshold. “We anticipate announcing top-line results at the end of the fourth quarter this year. We are hopeful that, if successful in this trial, glufosfamide will give patients another treatment option against this deadly cancer.”

Phase 3 Study Details

The pivotal Phase 3 trial is a randomized, open-label, multi-center trial designed to evaluate the efficacy and safety of glufosfamide compared with best supportive care (BSC) in patients with metastatic pancreatic cancer previously treated with gemcitabine. Patients in the active therapy arm receive glufosfamide 4500 mg/m2 intravenously on day 1 of each 21-day cycle. Treatment continues for up to 17 cycles until disease progression or unacceptable toxicity occurs.

The primary efficacy endpoint of the trial is overall survival. Secondary endpoints include, but are not limited to, partial and complete response rate, duration of response and progression free survival. Safety endpoints are the incidence and severity of adverse events and changes in laboratory parameters, weight and vital signs. All subjects receive BSC, which can include analgesics, antibiotics, transfusions, therapeutic hematopoietic colony- stimulating factors, erythropoietin and other appropriate supportive measures, and concomitant medications that do not have anti-tumor effects.

The Company continues to expect to have top-line results from the trial at the end of 2006. The Company also expects to have top-line results at the end of the year from a phase 2 clinical trial of glufosfamide plus gemcitabine for the treatment of first-line pancreatic cancer. Furthermore, the Company expects to initiate at least one additional clinical trial in another cancer indication this year.

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 initiate, enroll and complete its anticipated clinical trials, the time and expense required to conduct such clinical trials, issues arising in the regulatory process and the results of such clinical trials (including product safety issues as well as 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 May 15, 2006 and is available from the SEC’s website (www.sec.gov) and on our website (www.thresholdpharm.com) under the heading “Investors.” We undertake no duty to update any forward-looking statement made in this news release.

Contact: Denise T. Powell Sr. Director, Corporate Communications Threshold Pharmaceuticals, Inc. 650-474-8206 dpowell@thresholdpharm.com Carolyn Bumgardner Wang WeissComm Partners, Inc. 415-946-1065 carolyn@weisscommpartners.com

Threshold Pharmaceuticals, Inc.

CONTACT: Denise T. Powell, Sr. Director, Corporate Communications ofThreshold Pharmaceuticals, Inc., +1-650-474-8206, ordpowell@thresholdpharm.com; or Carolyn Bumgardner Wang of WeissCommPartners, Inc., +1-415-946-1065, or carolyn@weisscommpartners.com, forThreshold Pharmaceuticals, Inc.

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