FDA staffers say Allos drug benefit unconvincing

U.S. regulatory reviewers on Friday said they were not convinced that Allos Therapeutics Inc.’s experimental therapy benefited patients with tumors that had spread to the brain from the breast, sending Allos shares tumbling as much as 52 percent.

Allos last year said the therapy did not significantly improve upon radiation therapy among all patients tested with brain cancer but helped a sub-group of patients whose brain tumors came from breast cancer that had spread. One FDA reviewer called the latter finding “exploratory,” in part because the sub-group was not specified before the trial started. Reviewers from the U.S. Food And Drug Administration said the company’s claims were “not convincing.” The reviewers’ finding came in documents released on Friday by the U.S. Food and Drug Administration ahead of an advisory panel review on Monday. In the 538-patient Phase III clinical trial, Allos compared brain radiation therapy to a combination of radiation and the company’s treatment, called RSR13. According to the FDA documents, the median survival among patients on the combination treatment was 5.3 months compared with 4.5 months on the radiation. But the margin was slightly wider for patients whose brain tumors had spread from the breast, 5.9 months versus 4.5 months. However, neither difference was statistically significant. FDA reviewers in analyzing the results cited a section of the government guidelines about using sub-groups to declare a clinical trial successful. “These analyses are not intended to ‘salvage’ an otherwise non-supportive study but may suggest hypotheses worth examining in other studies or be helpful in refining labeling information, patient selection, dose selection, etc,” the reviewers said in the documents, quoting the regulations. The main statistical reviewer that prepared and reviewed documents for the FDA panel on the Allos treatment concluded that the benefit observed among the subgroup could be attributable to other factors. “The evidence of drug efficacy needs to be much stronger to be convincing,” the reviewer wrote. FDA advisory panels include experts in the therapeutic area for which the treatment at issue is intended, and the agency usually takes the advice of its panels. Shares of Allos were off $1.97, or 42.5 percent, to $2.67 in morning Nasdaq trading after falling to $2.21. (Source: Reuters Health News: Oncolink: May 2004)