Pharmaceutical company Sirtris announced last month that it had halted the last of its clinical trials of resveratrol, the minor ingredient of red wine that some researchers see as a drug that can extend life, but the co-founders of Sirtris, David Sinclair and Christoph Westphal, retain their confidence in the drug.

Resveratrol has several features that make it unsuitable as a drug, Sirtris CEO George Vlasuk said. These include the fact that it is hard to maintain a consistent level of resveratrol in the bloodstream, it seems to have different effects at different doses, and it is not patentable.