Solid Biosciences recently completed a big IPO despite disclosing, last-minute, that the FDA had partially suspended a clinical test of its gene therapy for Duchenne muscular dystrophy. Less than two months later, the company has reported a new, and more ominous finding: the FDA has halted testing of the treatment, known as SGT-001, altogether.
Cambridge, MA-based Solid (NASDAQ: SLDB) said late this afternoon that the FDA has placed a study called Ignite DMD, an early-stage test of SGT-001, on clinical hold. Solid said the first patient dosed in the study on Feb. 14 was hospitalized “several days” afterwards when lab tests revealed a decrease in platelet and red blood cells followed by “evidence of complement activation,” or the onset of an immune reaction.
Solid said in a statement that the patient “responded well to treatment and is currently asymptomatic.”
“All laboratory parameters have either improved or returned to normal, and he is continuing outpatient assessments per protocol,” the company said.
Nonetheless, the FDA has halted the study and Solid is “awaiting the formal…letter” from the agency to see what it will take to restart testing.
Solid shares plummeted more than 57 percent in after-hours trading on Wednesday.
The news is the second troubling sign for Solid’s gene therapy. The first was delivered in a regulatory filing just hours before the company raised about $125 million in an IPO in late January (shares had climbed nearly 60 percent from their IPO price, to more than $26 apiece, after the offering). At that time, Solid said that testing of SGT-001 had been partially suspended since November. The FDA’s “partial clinical hold,” as it is known, had stopped Solid from administering a high dose of its gene therapy to patients in its early-stage clinical study. The company said it was allowed to continue testing a lower dose—but now testing has been stopped completely.
Days after Solid completed its IPO, gene therapy pioneer James Wilson—who resigned from the company’s scientific advisory board in January—and his colleagues at the University of Pennsylvania published a paper sounding an alarm about the use of gene therapy to treat diseases like Duchenne. Their concerns emerged via animal tests of a potential gene therapy for the rare disease spinal muscular atrophy, but Wilson and colleagues warned that “careful monitoring” is needed in similar settings—that is, when performing a gene therapy procedure by infusing a high dose of adeno-associated viruses (AAV) containing genetic instructions directly into the bloodstream.
Solid is one of a few different companies, along with Sarepta Therapeutics (NASDAQ: SRPT) and Pfizer (NYSE: PFE), that are using this approach for Duchenne. Solid is the only member of the group, however, to report safety problems so far.
“With only a handful of patients having been dosed across all [Duchenne] gene therapy trials, it will take time to work out whether the adverse events are unique to Solid’s program or could potentially be indicative of broader complications associated with AAV-based gene therapies,” wrote RBC Capital Markets analyst Brian Abrahams in a note to investors.