Threshold Updates Glufosfamide Clinical Development Program

Threshold Updates Glufosfamide Clinical Development Program

REDWOOD CITY, Calif., Jan. 18, 2008 (PRIME NEWSWIRE) -- Threshold Pharmaceuticals, Inc. (Nasdaq:THLD) today provided guidance on the clinical development of glufosfamide and announced results from a Phase 2 clinical trial of glufosfamide for the treatment of patients with soft tissue sarcoma and from a Phase 2 clinical trial of glufosfamide for the treatment of patients with platinum-resistant ovarian cancer.

The soft tissue sarcoma trial was completed and provided evidence of clinical activity. The initial analysis of the results supports continued development of the compound for this indication but suggests different dosing regimens would likely be required to improve the therapeutic index. In the ovarian cancer trial, due to a lack of efficacy and enrollment challenges, the Company has decided to stop further enrollment and not pursue further clinical investigation in this indication. In the remaining ongoing clinical trial of glufosfamide, Threshold and its development partner in Japan, MediBIC Co., Ltd, continue to expect to complete an ongoing Phase 1 clinical trial for the treatment of solid tumors in the coming months. The Company entered into an agreement with MediBIC in 2004 to develop glufosfamide in Japan and other Asian countries, and a Phase 1 clinical trial commenced in January 2007.

Additionally, the Company is focused on TH-302, the Company's hypoxia-activated prodrug (HAP). TH-302 is a novel cancer therapeutic specifically activated under the low oxygen conditions typical of solid tumor cancer cells and is currently under investigation in a Phase 1 clinical trial in patients with advanced solid tumors.

"While we are disappointed that single-agent glufosfamide does not appear to be an effective treatment option for women with ovarian cancer, the results from the study of soft tissue sarcoma and our previous results from two studies in pancreatic cancer suggest that glufosfamide is an active chemotherapeutic agent for those indications," said Barry Selick, CEO. "That said, with our recent shift in focus to TH-302 and its underlying pipeline of HAP product candidates, we will be seeking a partner with whom to continue development of glufosfamide in these and potentially other indications."

Soft Tissue Sarcoma Clinical Trial Results

The sarcoma trial evaluated the efficacy and safety of glufosfamide in patients with previously treated, advanced, soft tissue sarcoma. Twenty-two patients with metastatic and/or advanced unresectable soft tissue sarcoma previously treated with one or two prior systemic therapies enrolled in the Phase 2, open-label, clinical trial at various sites in the United States. The primary efficacy endpoint of the trial was the objective response rate. The secondary endpoints of the trial included duration of response, progression-free survival, overall survival and various safety parameters. Tumor response was evaluated at baseline and every six weeks using the Response Evaluation Criteria In Solid Tumors (RECIST). Eight of 18 (44%) evaluable patients demonstrated clinical benefit with a RECIST assessment of stable disease or partial response. The most common severe adverse event was renal failure (5 of 22 patients). Renal toxicity was higher than in other glufosfamide studies but several risk factors were identified.

Ovarian Cancer Clinical Trial Results

The ovarian cancer clinical trial evaluated two dosing schedules of glufosfamide, a once weekly schedule and a schedule that included glufosfamide every three weeks. All patients were eligible to receive up to six 21-day cycles. Seventeen of the planned 45 subjects have been enrolled and received study drug. The primary efficacy endpoint of the trial was CA-125 response and CA-125 progression free survival. The rate of enrollment in the trial has been problematic. After multiple prior chemotherapies including platinum-containing regimens, otherwise eligible patients did not have adequate renal function for enrollment. In addition, only one confirmed CA-125 response and no confirmed tumor responses have been reported.

About Soft Tissue Sarcoma and Ovarian Cancer

Soft tissue sarcoma includes cancers of cartilage, fat, muscle, blood vessels, or other connective or supportive tissue. The American Cancer Society estimated that 9,220 people were diagnosed with a soft tissue sarcoma in the United States in 2007, and approximately 3,560 people died from this disease. Ovarian cancer is the eighth most common cancer among women, and is the fifth most common cause of cancer death among women. The American Cancer Society estimated that 22,430 women were diagnosed with ovarian cancer in the United States in 2007, and approximately 15,280 women died from the disease.

About Threshold Pharmaceuticals

Threshold is a biotechnology company focused on the discovery and development of therapeutics based on Tumor Hypoxia, a powerful scientific platform that offers broad potential to treat most solid tumors. By selectively targeting tumor cells, we are building a pipeline of drugs that hold promise to be more effective and less toxic to healthy tissues than conventional drugs. For additional information, please visit our website (

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 7, 2007 and is available from the SEC's website ( and on our website ( under the heading "Investors." We do not intend to update any forward-looking statement made in this news release.