More Tysabri, Accelerated Approval Questions

Tysabri received fast approval in November after it was shown to reduce the risk of relapses of multiple sclerosis 66% compared with placebo. When it was used with Avonex, also an MS treatment, the combination cut that rate 54% compared with Avonex alone.

Now, researchers, patients and the agency itself will have to ask whether the potential danger with Tysabri could have been discovered before the drug won accelerated approval. The two cases involve patients who had taken the drug for more than two years, and Tysabri was approved based on about one year of data. If the FDA followed its more typical procedure of waiting for two-year data on multiple- sclerosis drugs, the cases might have surfaced during the review and "they probably would not have approved the drug," says Aaron Miller, chief medical officer at the National Multiple Sclerosis Society...

Douglas Throckmorton, acting deputy director of the FDA's drug center, says that the problem that has surfaced in the patients taking Tysabri is "extremely rare," and "it's hard to imagine we would detect" it in a full approval process. [Except, of course, that this effect was seen in a post marketing study, which would have been a pre-marketing study if Tysabri hadn't received accelerated approval -- Margaret] It is "unlikely that a rare adverse event like this one would be seen" in the typical trials done for a drug approval, and this drug held strong benefits in a terrible disease, he says. Though "the longer you watch people, sometimes you learn things," he says. "I don't think this particular case raises any questions" about the accelerated approval process, he says...