Solid Bio's DMD gene therapy graduates from partial FDA hold to full-on clinical hold

stop sign (knerri61/Pixabay)
Solid Bio is waiting on a formal clinical hold letter from the FDA to determine its next steps. (Walter Knerr)

The FDA placed a clinical hold on Solid Biosciences' phase 1/2 trial of SGT-001, its gene therapy for Duchenne muscular dystrophy. Shares were halted for half an hour Wednesday afternoon and closed down 0.5%, but fell 54% in after-hours trading.

The IGNITE-DMD trial is investigating the safety and efficacy of SGT-001 microdystrophin gene transfer in nonambulatory children and adolescents with DMD. The FDA imposed the hold after Solid Bio reported the hospitalization of a patient who was dosed with 5E13 vg/kg of SGT-001 a month ago, the company said.

The patient, the first to be dosed in the trial, was hospitalized "several days" after treatment because lab tests showed a lowered platelet count and decreased red blood cell count, as well as complement activation, a type of immune response. He has been treated and currently has no symptoms, Solid Bio said. 

The FDA classed the event as a "Suspected Unexpected Serious Adverse Reaction" and slapped a hold on the trial. Solid Bio halted enrollment and dosing and is now waiting for an official letter from the agency to help figure out its next steps. 

The news comes six weeks after the Cambridge, Massachusetts-based biotech priced a downsized IPO of $125 million. Solid Bio had planned to price its shares at $18 to $19, but dropped that to $16 after it revealed in an SEC filing the day of its IPO that the same phase 1/2 clinical trial of SGT-001 was put on a partial clinical hold. 

The partial hold affected the higher-dose arm of the trial and so, Solid Bio was allowed to go forward with the lower-dose cohort. The new clinical hold effectively scuttles the program, at least, for now. 

It isn't the holds themselves that are sending alarm bells ringing. Rather, it's the Solid Bio's inclination to keep such news under wraps that is causing concern. Add to that the January departure of one of its key scientific advisers, gene therapy giant James Wilson, due to “emerging concerns about the possible risks of high systemic dosing” of the adeno-associated virus (AAV) vectors used in SGT-001, and you can see why investors are jittery.