CRANBURY, NJ ( TheStreet) -- The U.S. Food and Drug Administration refused a request from Amicus Therapeutics (FOLD - Get Report) to amend the statistical plan for a failed phase III study of its experimental Fabry disease drug Amigal. As a result, Amicus is delaying the U.S. approval filing for Amigal until late 2014 or early 2015 -- after data from another phase III study is completed.
Amicus shares fell 22% to $2.50 in early Monday trading.
Last December, Amicus announced disappointing six-month results from a phase III study of Amigal in patients with Fabry disease. Forty-one percent of Amigal patients were counted as responders (meaning they had a 50% decrease in GL3 in their kidneys. By comparison, 28% of placebo patients were responded. The response trend clearly favored Amigal but the difference was not statistically significant.
Amicus met with FDA hoping to convince regulators to allow changes to the study to review Amigal's efficacy based on longer-term (12 months) response rates, as well as in certain subgroups of patients with higher baseline levels of GL3.On Monday, Amicus said FDA agreed to the changes in the study but regulator also insisted that from a regulatory standpoint, the study would still be considered a failure. This prevents Amicus and partner GlaxoSmithKline (GSK - Get Report) from seeking FDA approval until more Amigal data is compiled. The two companies are conducting a second phase III study in which Fabry patients are switched from a currently approved therapy to Amigal. Results from this study are expected in the first half of 2014. Even if the study is positive, Amicus cautioned that a U.S. filing won't be completed until another meeting is held with FDA in the second half of 2014. Twelve-month data from the first phase III study are expected in the fourth quarter of this year. Amicus has enough cash on hand to continue operations into the second half of 2014. -- Reported by Adam Feuerstein in Boston. Follow @AdamFeuerstein