About Threshold PharmaceuticalsThreshold 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 as well as the bone marrows of some hematologic malignancies. This approach offers broad potential to treat a variety of cancers. 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 and its potential therapeutic uses and benefits. 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, the ability of Threshold or clinical investigators to enroll patients in clinical trials of TH-302, whether this trial or any others of TH-302 will confirm the results of earlier trials or animal experiments, the time and expense required to conduct such clinical trials and analyze data, whether TH-302 combined with bevacizumab provides anticipated benefits, Threshold’s ability to develop a clinical formulation of TH-302 and secure and adequate supply, issues arising in the regulatory 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.