Threshold Pharmaceuticals, Inc. Completes Enrollment In A Phase 2 Study For The Treatment Of Benign Prostatic Hyperplasia

REDWOOD CITY, Calif., March 20 /PRNewswire-FirstCall/ -- Threshold Pharmaceuticals, Inc. , today announced that the Company has completed enrollment in the Phase 2 study evaluating TH-070 for the potential treatment of benign prostatic hyperplasia (BPH). The Phase 2 study, being conducted in the United States, is investigating the dose response of TH-070 in patients with BPH.

“We are pleased to have reached this milestone. We anticipate that we will have top line results around the beginning of the fourth quarter this year,” said Alan Colowick, M.D., chief medical officer at Threshold. “We look forward to the continued development of TH-070 and to the potential benefit that TH-070 may provide to men suffering from the symptoms of BPH.”

The Phase 2 trial is a randomized, placebo controlled, double-blinded study in men with symptomatic BPH. Patients participate in the study for up to four and a half months. After a two-week placebo run-in period, patients will be randomized to receive placebo or one of four doses of TH-070 (5mg, 25mg, 50mg, 150mg) daily for 28 days, and will be followed off of therapy for an additional three months. The primary objective of this study is to investigate the dose-response relationship of TH-070 with respect to symptomatic improvement and to evaluate safety.

The Company is also conducting a Phase 3 randomized, placebo-controlled, double-blinded study in men with symptomatic BPH. Enrollment in this trial is expected to be completed in April. These patients will participate in the study for up to four and a half months (2 week placebo run-in, 3 months of treatment and 1 month off of therapy). The primary objective of this study is to evaluate the efficacy of TH-070 compared to placebo as measured by IPSS (International Prostate Symptom Score) in subjects with symptomatic BPH.

Threshold previously announced the results from a Phase 2 single center study conducted in 2004 at the University of Bari, Italy. That trial met its primary endpoint, a mean reduction in prostate volume measured by Trans-Rectal Ultrasound (TRUS) at day 28 compared to baseline (-11.2%, p<0.001), and all other day 28 endpoints. Six months after cessation of treatment, BPH symptoms (as measured by IPSS) in patients remained significantly improved compared to baseline as were maximum urine flow, post-void urine volume, and PSA (Prostate Specific Antigen). Detailed results of the study were published in the quarterly journal of Reviews in Urology in May, 2005.

2006 TH-070 Key Milestones

The Company anticipates the following additional clinical milestones related to TH-070 in 2006:

-- Complete enrollment in the Phase 3 study in BPH in April -- Report results from the Phase 2 and Phase 3 studies in BPH with TH-070 around the beginning of the 4th quarter; and -- Commence three supportive studies with TH-070 About TH-070

TH-070 is thought to disrupt energy metabolism by interfering with glycolysis. Glandular prostate epithelial cells -- cells that overgrow in BPH -- are unique in that they are primarily dependent on glycolysis for energy production. Preclinical data and Phase 2 data thus far indicate that TH-070 may provide rapid symptom improvement, decreased prostate size, increased urine flow rate, and decreased serum PSA, with limited side effects for the treatment of BPH.

About Benign Prostatic Hyperplasia (BPH)

BPH, also known as benign enlargement of the prostate, is the most common urological problem among older men and affects an estimated 18 million men in the United States, 28 million men in five major European countries and 8 million men in Japan. BPH can restrict the flow of urine, resulting in urine retention, which can cause weakening of the bladder wall and the inability to empty the bladder completely. It can also be progressively severe, with the risk of urinary tract infection, kidney and bladder damage, bladder stones and incontinence.

About Threshold Pharmaceuticals, Inc.

Threshold is a biotechnology company focused on the discovery, development and commercialization of mid-late stage small molecule therapeutics for the treatment of benign prostatic hyperplasia (BPH), a disease afflicting tens of millions of men worldwide, and cancer. By selectively targeting tumor or other abnormally-proliferating 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 initiate, enroll and complete its anticipated clinical trials, the time and expense required to conduct such clinical trials, and the results of such clinical trials (including unanticipated 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 November 10, 2005 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 Carolyn Bumgardner Wang Sr. Director, Corporate Communications WeissComm Partners, Inc. Threshold Pharmaceuticals, Inc. 415-946-1065 650-474-8206 carolyn@weisscommpartners.comdpowell@thresholdpharm.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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