About TH-302 and PazopanibTH-302 is a novel small molecule hypoxia-targeted prodrug studied in over 500 patients to date with promising Phase 1/2 data against multiple tumor types both as monotherapy and in 4 different chemotherapy combinations. Threshold is currently evaluating TH-302 in a Phase 2 controlled clinical trial in patients with advanced pancreatic cancer and plans to initiate a pivotal Phase 3 trial in patients with soft tissue sarcoma in 2011 under a Special Protocol Assessment agreement with the FDA. Pazopanib (marketed by GlaxoSmithKline as Votrient ®) is a multi-targeted anti-angiogenic tyrosine kinase inhibitor that blocks tumor growth and inhibits angiogenesis. It is currently approved in the United States for the treatment of patients with advanced renal cell carcinoma. About Threshold Pharmaceuticals Threshold is a biotechnology company focused on the discovery and development of drugs targeting Tumor Hypoxia, the low oxygen condition found in microenvironments of most solid tumors. This approach 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 anticancer drugs. For additional information, please visit our website ( 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 TH-302, its mechanism of action, its potential therapeutic uses and benefits and upcoming clinical trials. 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, whether TH-302 in humans will act as anticipated based on preclinical studies, whether future clinical trials will confirm the results of earlier trials based on small numbers of patients or confirm the earlier results from the same trials, the time and expense required to conduct such clinical trials and analyze data, Threshold's ability to complete its clinical trials, issues arising in the regulatory or manufacturing process and any unanticipated or increased side-effects observed in patients receiving TH-302. 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 12, 2011 and is available from the SEC's website ( www.sec.gov) and on our website ( www.thresholdpharm.com) under the heading "Investors." We do not intend to update any forward-looking statement made in this news release.