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Sarepta gene therapy win helps to validate broader platform

Shares of Cambridge-based Sarepta rallied nearly 8 percent Monday.
Shares of Cambridge-based Sarepta rallied nearly 8 percent Monday.Ruby Wallau for STAT

Data on Sarepta Therapeutics’s experimental gene therapy for a rare type of muscular dystrophy showed that patients receiving a higher dose of the medicine saw greater benefits than those receiving a lower dose, delivering another early-stage win for the drug developer.

Three patients with limb-girdle muscular dystrophy Type 2E who got the high dose of Sarepta’s SRP-9003 produced greater levels of the protein beta-sarcoglycan. While patients with the progressive and debilitating muscle-wasting disease normally make very little or none of the protein, the three children showed an average protein expression that was 62 percent of normal, topping the 36 percent seen at the lower dose, when using a standard analysis called Western Blot.

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‘‘We see a dose-dependent increase in expression and we see good tolerability across these kids in both the first and second cohort,’’ chief executive Doug Ingram said in an interview.

All three patients in the early-stage study saw an average reduction in the enzyme that the muscle releases when it’s being damaged, known as CK, of 89 percent after 90 days. Ingram called the reduction in enzyme levels ‘‘encouraging.’’ The three patients also showed significant expression of alpha-sarcoglycan, another integral protein.

Shares of Cambridge-based Sarepta rallied nearly 8 percent Monday. RBC Capital Markets analyst Brian Abrahams advised clients to continue buying shares as the results help provide ‘‘clear differentiation’’ of Sarepta’s gene therapy platform compared to peers.

Ingram highlighted that none of the six patients treated saw a decrease in platelet counts that were outside of normal or any signals of complement activation. ‘‘That has been, for other therapies using different vectors, a very significant issue and in fact others have been put on clinical hold as a result of these very serious problems,’’ he said.

While the opportunity in this rare disease is much smaller than the company’s leading program in Duchenne muscular dystrophy, Wall Street will likely be pleased with the update as it further validates Sarepta’s gene therapy platform. Coming into the data, analysts including Mizuho’s Difei Yang were looking for a solid safety profile as well as a clear increase in benefit at the higher dose.

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Sarepta also said three patients who received the lower dose of SRP-9003 had improved function one year after treatment.

The company plans to select the final dose for a registrational trial in the coming months as it continues to discuss trial designs with regulators around the world.

When asked if there was interest in studying a higher dose of the gene therapy, Ingram said ‘‘we’re getting to the top of what one could reasonably expect.’’

The update comes less than a month after underwhelming data from competitor Pfizer’s Duchenne muscular dystrophy gene therapy sent shares of Sarepta to a nine-month high.