Solid Biosciences has surged back into the Duchenne muscular dystrophy (DMD) gene therapy race. The biotech reported expectation-busting phase 1 data on its next-generation candidate, sending its stock spiraling upward.
Massachusetts-based Solid’s first attempt at a DMD gene therapy suffered a series of setbacks, with FDA holds, safety signals and other problems culminating in the decision to prioritize its successor in 2022. The biotech provided the first look at whether the switch to SGT-003 may pay off Tuesday with the publication of Day 90 biopsy data on the first three participants in a phase 1/2 trial.
Between 70% and 88% of the participants’ fibers were positive for dystrophin, resulting in a mean result of 78%. Talking at a Barclays investor event last year, Solid CEO Bo Cumbo said 40% dystrophin-positive fibers would “give you enough expression to hit a clinical benefit for these kids” and that he would focus on that data, rather than microdystrophin expression data when deciding whether to advance the asset.
Investors celebrated the ease with which Solid vaulted past the 40% target. Shares in the biotech rose almost 90% in premarket trading to top $7.50. Solid hit that high despite announcing the data alongside a $200 million stock offering that priced its shares at just over $4 a pop.
Mean microdystrophin expression was around 110%, regardless of whether it was assessed using western blotting or mass spectrometry. The mean figure masks variability, with expression levels using mass spectrometry ranging from 53% to 152%. Solid also shared reductions in markers of muscle injury and stress and an 8% mean increase in cardiac function in the two patients with 180 days of follow up.
The biotech has safety data on six patients who are at least 20 days out from receiving the gene therapy. No patients had serious adverse events or suspected unexpected serious adverse reactions. Similarly, Solid saw no evidence of thrombotic microangiopathy, atypical hemolytic uremic syndrome or hemolysis and no cases of hepatic transaminitis.
With the data suggesting SGT-003 may be free from some of the problems of its predecessor, Solid is expanding the study. A seventh participant received the gene therapy yesterday. Solid expects to have dosed at least 10 patients by early in the second quarter and roughly double that figure by the fourth quarter. The expansion will support a planned chat with the FDA about an accelerated approval pathway.