Sarepta dips on controversial Duchenne hospitalization report

Sarepta’s stock plunged 12% Thursday afternoon on the news that a patient in a study testing its gene therapy for Duchenne muscular dystrophy had been hospitalized for a serious illness—in February. But Sarepta struck back, saying the report was "erroneous" and neither a Sarepta employee nor the study investigator reported the hospitalization to an FDA database.

A 7-year-old child was hospitalized after developing rhabdomyolysis, according to an entry in the FDA Adverse Events Reporting System (FAERS). Rhabdomyolysis is a rare but serious condition stemming from muscle injury that can lead to kidney failure. When muscle is severely damaged, its fibers may break down and leak myoglobin into the bloodstream, where it finds its way to the kidneys. Rhabdomyolysis is often seen in people who have suffered a major injury, but it can also affect athletes who overtrain and develop in response to drugs, the Mayo Clinic says. 

By virtue of having a disease in which muscles weaken and die, patients with muscular dystrophies like Duchenne are at higher risk of developing rhabdomyolysis. But "if this event does turn out to be significant and Sarepta was aware of it, it wouldn't be a great look for the company," Baird analyst Brian Skorney said in a note, as reported by Reuters.

Hours later, Sarepta put out a statement saying the hospitalization report was "erroneously submitted" to the FAERS database, "a post-marketing surveillance database for approved therapies."

"Our investigation to date indicates that this report was not submitted to the FAERs database by a Sarepta employee or the study’s principal investigator," the company said in the statement.

Two weeks after treatment, the child had dark urine and high levels of creatine kinase—two hallmarks of rhabdomyolysis—but no other symptoms, Sarepta said. He was hospitalized for observation and then discharged the next day. As the trial is a one-to-one blinded study, there was no telling whether the patient had received the experimental gene therapy or placebo, the company said.

RELATED: Sarepta slips on U.K. golodirsen study halt but expects to get back on track

Sarepta's statement confirms concerns raised by Cantor Fitzgerald analysts who listed in an earlier note a few points that “give us some caution in over-interpreting this finding in the FAERS data base." The analysts found it “odd” that, according to the database, Sarepta itself had reported the hospitalization but had made no mention of it in its earnings call on Wednesday or during a call it held in March to discuss the data. 

"Even if this reported event did occur in the 9001 trial, we have no way of knowing whether it was a placebo or treated patient. We note that rhabdomyolysis is a known issue in DMD and it would not be surprising to see this in non-treated patients,” the analysts wrote. 

The news follows a similar hiccup for Sarepta’s golodirsen, the follow-up to its first approved Duchenne drug Exondys 51 (eteplirsen). In February last year, the company halted dosing in a U.K. study of golodirsen, dubbed Essence, due to “one serious adverse event that could possibly be related to the investigational drug product,” Sarepta said in an emailed statement. 

A Facebook post from a parent whose child participated in that study illuminated the reason for the hold: “My son was due his biopsy and first dose of 45 skip [in] Essence last week. They have temporarily stopped dosing in the UK … I understand due to rhabdomyolysis side effects,” the parent wrote. 

The company expected to resume dosing once it got the OK from the U.K.’s Medicines and Healthcare products Regulatory Agency, but appeared to be trying to keep the hold under wraps—not a good look, then or now. 

RELATED: Pfizer's DMD gene therapy safety data hand advantage to Sarepta 

In June, Pfizer reported data from a small study of its own DMD gene therapy that raised safety concerns: One of the first six people to receive the treatment was hospitalized with acute renal injury. At the time, analysts talked down Pfizer’s chances of competing with Sarepta, but Thursday’s revelation may just level the playing field.