Sarepta Therapeutics said on Thursday it was informed that an adverse event report was erroneously submitted to the U.S. health regulator regarding an ongoing study of the company's gene therapy for Duchenne muscular dystrophy (DMD).
Shares of the company had plunged as much as 19% earlier after a notice from the FDA showed a patient in the study was reported to have developed a serious illness.
They pared losses to trade down about 7% in late afternoon trading after the company's statement.
Sarepta said its investigation indicated the report was not submitted by its employee or the study's principal investigator.
The drug safety monitoring board has recommended the study to continue after a review, the company said in a statement.
The incident, which occurred in February, involved a seven-year-old boy who developed rhabdomyolysis, a serious condition that can lead to complications such as kidney failure.
The illness was reported in the U.S. Food and Drug Administration adverse events database, which on its own cannot determine whether a drug is the cause of a problem, but can signal potential risks that warrant investigation.
In June, Pfizer, which is racing Sarepta to be first to market with a gene therapy for DMD, reported results from a tiny early study of its experimental treatment.
At the time, Pfizer said two of the six patients in its trial experienced side effects that landed them in the hospital, after which Wall Street analysts declared Sarepta was leading the charge to market.
Sarepta already has one drug to treat some types of DMD on the market.
DMD is a rare, genetic disorder that hampers muscle movement mainly in men, affecting one in every 3,500 to 5,000 males. A lack of dystrophin can cause life-threatening damage to the heart, and over time, death, often at a young age.