Threshold Pharmaceuticals Initiates Phase 2 Clinical Trial Evaluating Glufosfamide In Patients With Platinum-Resistant Ovarian Cancer

Threshold Pharmaceuticals, Inc. (Nasdaq: THLD), today announced that it has initiated patient enrollment for a Phase 2 clinical trial evaluating the dosing, safety and activity of glufosfamide in patients with platinum-resistant ovarian cancer.

"There are very few drugs that will effectively treat platinum-resistant disease," said David S. Alberts, M.D., Director of the Arizona Cancer Center, University of Arizona, and a clinical investigator for the trial. "We are extremely interested in this potential therapy as it may provide an additional treatment option for women with ovarian cancer who are platinum-resistant."

Platinum based therapy is the most widely used chemotherapy to treat ovarian cancer, but some women develop resistance to it. When women develop resistance, it is very difficult to treat and to cure them. The current standards of care in treating platinum-resistant ovarian cancer are a variety of single agent and combination regimens including topotecan, anthracyclines such as doxorubicin, gemcitabine, cyclophosphamide, vinorelbine, hexamethylmelamine, ifosfamide, and etoposide.

Phase 2 Clinical Trial Design

The clinical trial will evaluate two dosing schedules of glufosfamide, a once weekly schedule and the schedule currently utilized in pancreatic cancer trials which is every three weeks. The trial will explore the administration of slightly higher aggregate doses utilizing the weekly schedule as compared to every three week dosing. All patients may receive up to six 21-day cycles. Overall 45 women with ovarian cancer who have previously relapsed after up to four prior chemotherapy regimens including one or two prior platinum-containing regimens and who have demonstrated resistance to their last platinum-containing regimen will be enrolled in the Phase 2, open-label, clinical trial at various sites in the U.S.

In addition to safety, the trial is investigating the efficacy of glufosfamide as determined by response rate, duration of response and progression-free survival based on changes in the serum tumor marker level CA-125 and based on tumor assessments and overall survival.

About Ovarian Cancer

The American Cancer Society estimates that 20,180 women were diagnosed with ovarian cancer in the United States in 2006, and approximately 15,000 women will die each year from the disease. Ovarian cancer is the eighth most common cancer among women, and is the fifth most common cause of cancer death among women. Virtually all newly diagnosed patients undergo surgery, which is typically followed by radiation and chemotherapy. Almost half of all ovarian cancers do not respond at all because of an innate resistance to platinum-based drugs.

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 November 9, 2006 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.

Threshold Pharmaceuticals, Inc.
http://www.thresholdpharm.com