Shares of Amicus Therapeutics fell as much as 22 percent Monday after the company announced that it will delay seeking regulatory approval in the US for its experimental Fabry disease drug Amigal (migalastat), which it is co-developing with GlaxoSmithKline, until the second half of 2014. Following discussions with the FDA, the drugmaker determined that approval would be more likely if it awaited 24-month data from a Phase III study and the findings of an additional late-stage trial.
Last December, Amicus announced that in a late-stage study, 41 percent of patients given Amigal had a response at six months, as defined by a 50-percent or greater reduction in interstitial capillary globotriaosylceramide (GL-3), compared to 28 percent of patients given placebo, a difference that was not considered significant. Amicus met with US regulators to propose several revisions to the study, including examining response rates at 12 months instead of six months, and narrowing the study population to include patients with higher baseline levels of GL-3. The drugmaker said the FDA agreed to the changes in the trial, but also noted that from a regulatory standpoint, the study would still be considered a failure.
US regulators also noted that the data would not facilitate approval and said it would be preferable to await the "entirety" of the results from the two clinical trials. In the second late-stage study, 60 patients receiving enzyme replacement therapy were given Amigal or continued on enzyme replacement therapy. The study is designed to demonstrate that Amigal is non-inferior to enzyme replacement therapy after 18 months and results are expected in the first half of 2014. Twelve-month data from the first Phase III trial are expected in the fourth quarter of this year.
Commenting on the news, CEO John Crowley noted that "we believe that the better regulatory strategy is to obtain all of the Phase III datasets and to combine and integrate these data into one NDA submission." He further noted that "we are essentially trading time for certainty," adding that "looking at all that data that’s going to come, I think it’ll make for a pretty compelling data package if the data keeps trending the way that we’ve seen before." Crowley suggested that the company will meet with the agency in the second half of next year to discuss a potential marketing submission.
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