• Shares down as much as 59 percent, most since company's IPO
  • Regulators ask for additional information from clinical trials

Amicus Therapeutics Inc. shares plunged after U.S. regulators asked for more information on its experimental pill for treating Fabry disease, delaying the application for approval and sending shares down.

Shares fell 47 percent to $7.33 at 9:53 a.m. in New York, after earlier dropping as much as 59 percent in the biggest intraday decline since Amicus’s 2007 initial public offering. Before Friday’s drop, the stock had more than doubled in the last year.

The Food and Drug Administration’s request means Amicus, which develops treatments for rare diseases, won’t be able to file for U.S. approval of the medicine by the end of the year, its previous target. The agency asked Amicus to integrate data it had compiled from previous clinical trials on the drug, migalastat, which will take time to complete, the Cranbury, New Jersey-based company said in a statement. It also may need to gather additional information on migalastat’s effect on Fabry disease’s gastrointestinal symptoms.

Fabry is a rare, inherited disease marked by the buildup of fat in the body’s cells. It can cause a host of symptoms ranging from pain to trouble seeing and hearing, and affects 1 in 40,000 to 60,000 males, according to the U.S. National Institutes of Health. It is less common in women.

The company said it won’t be able to set a new timeline for its application until it’s determined the exact path it needs to follow for approval. Migalastat would compete with Fabrazyme, an enzyme-replacement therapy for the condition made by Sanofi.

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