An FDA advisory panel tomorrow will debate data on using prostate drugs to prevent cancer. The drugs in question are GlaxoSmithKline's ($GSK) Avodart and Merck's ($MRK) Proscar, and each has been tested in men at risk of prostate cancer. Both cut the incidence of low-risk cancers. But the problem is, both appeared to slightly increase the risk of more aggressive tumors.
GSK has asked the agency to approve Avodart specifically to help cut cancer risk. Merck, for its part, has only asked FDA for permission to add data from the Proscar cancer-prevention study to the drug's label. But the advisory committee will take up both drugs; as agency reviewers noted, the new label language on Proscar could be interpreted as an endorsement.
Here's the hard data. GSK's 8,200-patient Reduce trial showed that patients who took Avodart for four years were 23 percent less likely to have a positive biopsy for cancer. But among the Avodart patients, 29 developed high-rate tumors, compared with 19 placebo patients. The difference wasn't statistically significant, but FDA staff reviewers also pointed out that the overall cancer-risk reduction was driven by a reduction in low-risk cancers. Merck's PCPT trial of 19,000 patients found prostate cancer in 803 of the men using Proscar, versus 1,147 men taking placebo, or 18.4 percent and 24.4 percent, respectively.
Even if the FDA approves Avodart for this new use, the impact on sales may not be as large as initially thought, Matrix Corporate Capital analyst Navid Malik told Bloomberg. Before the safety risks emerged, he said, the new indication was expected to add more than $1 billion to annual sales. But now, doctors might think twice before prescribing the drug for the new use. We'll see how the FDA's experts weigh in.