A drug, tetrathiomolybdate (TM), which mops up copper in the body and that had already failed in a series of previous cancer clinical trials, is getting a second chance. A phase II trial of the drug in women who had been successfully treated for breast cancer but have a high risk of recurrence suggests that it can prevent the growth of new tumors. Yet the promise of this copper depletion strategy appears tarnished not by clinical results but by corporate strategy. The oncologist who led the phase II trial now wants to proceed with a larger, phase III trial of TM. But the rights to treating cancer with TM are held by a Swedish biotech company that is developing the drug instead for Wilson disease, a rare inherited disease of copper accumulation. The company, Wilson Therapeutics, has no immediate plans to test TM in cancer patients, its CEO acknowledges, and for now will not sublicense the drug.