Solid tumors are often starved of oxygen, as new blood vessel formation typically can't keep pace with rapid cell division. Yet, rather than suffocating cancer tissue, this 'tumor hypoxia' usually renders cancer cells resistant to standard therapies, as oxygen is necessary to fuel the development of DNA strand breaks in radiation therapy and the dearth of blood vessels keeps circulating chemotherapy regimes away. Even with this elemental problem, however, some changes in hypoxic cells could actually result in increased drug sensitivity—a weakness that many drug developers hope to exploit for a next generation of tailored cancer treatments.
Leading the pack of so-called 'bioreductive prodrugs'—agents that become activated only in the oxygen-poor core of solid tumors—is Threshold Pharmaceuticals' TH-302. In a talk presented on 2 April at the American Association for Cancer Research's annual meeting in Chicago, Threshold announced the results of a phase 2 trial involving 214 people with advanced pancreatic cancer. Compared with chemotherapy alone, the addition of TH-302 increased the average progression-free survival time from 3.6 to 5.6 months, the San Francisco–based drugmaker found.
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