- Solid Biosciences on Wednesday said its gene therapy SGT-001 stimulated production of a key muscle-building protein in patients with Duchenne muscular dystrophy, achieving a level as high as 18% of normal in one patient.
- The data came from two patients in the second dose group of the IGNITE-DMD trial. A third patient in that dose group had an immune response and was admitted a hospital in November, prompting the Food and Drug Administration to impose a hold on the trial.
- Solid reported today that the patient has been discharged from the hospital, and CEO Ilan Ganot said the company is working "with a sense of urgency and purpose" to resolve the hold.
SGT-001 is Solid's one clinical-stage pharmaceutical product, and needs steady progress toward approval to satisfy investors. The ongoing clinical hold — which, when it was announced in November, knocked $376 million off Solid's market value — hasn't helped the biotechs' case.
Wednesday's update didn't do much to restore confidence, either. Shares fell another 14% in morning trading Wednesday, to $4.12 apiece, after the company provided data from muscle biopsies of the two patients who weren't hospitalized in the second dosing group.
This group of patients received 200 trillion vector genome copies per kilogram of body weight, four times the dose of an earlier group of three patients. SGT-001 transfers a shortened version of the dystrophin gene to cells, which aims to stimulate a functional version of the muscle-building protein called microdystrophin.
The biopsy for one patient showed that 10% to 20% of microdystrophin-positive muscle fibers expressed the protein and expression levels were 6% of what would be expected in patients without DMD. In the other patient, the biopsy showed expression in 50% to 70% of microdystrophin-positive fibers, and that expression levels were 18% of non-DMD patients.
By comparison, the average expression level in four patients treated with Sarepta's similarly acting gene therapy SRP-9001 was 74%.
In a conference call with investors this morning, Solid's R&D head Joel Schneider cautioned that dystrophin expression varies in the general population and that it is not clear what level of expression is necessary to achieve near-normal muscle growth and maintenance.
With Sarepta nearing the end of dosing of its current SRP-9001 trial and preparing a trial of its commercial-scale supply next year, it appears to be closing in on FDA submission much more quickly than Solid.
Resolving the clinical hold will help Solid get back on track, but SGT-001 may need more data that reassures investors it can compete with SRP-9001 clinically before its shares can return to pre-hold values.