- Sarepta said its gene therapy for a rare genetic disease known as Limb-girdle muscular dystrophy continued to help patients two years after a single treatment, with trial participants sustaining functional gains and producing a protein that protects muscle tissue from damage.
- The data, released at the Muscular Dystrophy Association's scientific meeting Thursday, included an update for three patients given a low dose of the treatment two years ago and three more who are a year removed from receiving a higher dose. The high-dose group also showed functional gains after one year, although SVB Leerink analyst Joseph Schwartz noted that result fell short what was seen in low-dose recipients at the same time point.
- The data, which compared Sarepta's treatment to historical controls, not a placebo, could help reassure investors in Sarepta's broader gene therapy platform after its lead project, the experimental Duchenne muscular dystrophy treatment SRP-9001, missed its main goal in a mid-stage trial in January. Sarepta's shares have lost roughly half their value since.
Sarepta has three marketed products treating Duchenne, plus a beefy pipeline of 39 experimental RNA-based programs and genetic medicines for rare diseases. One towers above them all, however: SRP-9001. Its clinical trial setback in January cut the company's valuation in half as a rival treatment from Pfizer appeared to be taking a lead.
With the path to market looking longer for SRP-9001, other pipeline projects may figure more prominently in Sarepta's outlook, and the data from the follow-up project, known as SRP-9003, may be reassuring to investors.
SRP-9003 treats a type of muscular dystrophy called Limb-girdle that particularly affects the arms and legs. To do so, it helps replenish the deficiency of a protein called beta-sarcoglycan, the lack of which is thought to trigger the disease.
The first three patients in Sarepta's early-stage trial were infused with a low dose of the gene therapy, and after 18 months of treatment had improved their score by 5.7 points on a 20-item test that measures their ability to do such tasks as stand up from a chair or stand briefly on one foot. That improvement was sustained at two years, Sarepta reported Thursday.
In a research note, SVB Leerink's Schwartz wrote that untreated patients would have been expected to decline by 4.6 points over the same time period. Biological measures, such as expression of the beta-sarcoglycan protein, also showed positive signs, although they were short of expression seen in the healthy population.
Three higher-dose patients also showed improvements at one year. Their four-point increase on the functional test was short of the six points seen in the lower-dose group at 12 months, although Schwartz noted that biomarkers indicated the high-dose group may have been less disabled when they received the gene therapy.
The company hasn't seen any new safety signals. One adverse event was reported in an earlier data release, a patient who was dehydrated from vomiting.
Schwartz wrote that the data could set the stage for a study that could be submitted to regulators to support approval. There are no treatments for limb-girdle muscular dystrophy, so a regulatory pathway will need to be discussed with the Food and Drug Administration, as well as a quality assessment of the batch of gene therapy to be used in that trial. That could make the path forward for limb-girdle gene therapy different than the one Sarepta's traversing in Duchenne, where there are at least some marketed drugs for the condition.
The next study should begin this year, Schwartz wrote.