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Sarepta Touts More Gene Therapy Data, Snaps Up Myonexus For $165M

Xconomy Boston — 

Sarepta Therapeutics (NASDAQ: SRPT) has been steadily building up its gene therapy capabilities for a few years now, and it took two more steps forward on that front this morning. First, it exercised an option to buy gene therapy startup Myonexus Therapeutics for $165 million. And then it disclosed early human results from the first program to come from the deal, a potential treatment for a form of Limb-Girdle Muscular Dystrophy (LGMD), a progressive, deadly genetic disease with no available treatments.

Sarepta first announced a partnership with Myonexus, a spinout of Nationwide Children’s Hospital in Columbus, OH, in May 2018. In the deal, Sarepta paid Myonexus $60 million for the exclusive option to buy the company and its five experimental gene therapy programs—each for different forms of LGMD—upon getting a look at early human data.

The deal marked the continuation of a concerted effort by Sarepta—long known as an RNA drug developer—to become a leader in the field of gene therapy, which offers the potential for a long-lasting, if not permanent treatment for a genetic disease through a single treatment.

Prior to the Myenoxus deal, Sarepta had already aligned itself with Nationwide on two gene therapy programs for Duchenne muscular dystrophy, another deadly disorder. And since nabbing an option to buy Myonexus, one of those Duchenne treatments has shown promise in human trials, putting Sarepta in the lead of a competitive race to be the first to market with a gene therapy for DMD. The Myonexus gene therapies are part of a plan to expand its reach elsewhere. The company has a total of 13 experimental gene therapies in its portfolio.

Today, Sarepta provided at least an early indication that the Myonexus acquisition has a chance to pay dividends. It disclosed data from the first three patients in a human study of MYO-101, a gene therapy for patients a form of LGMD known as LGMD Type 2E. The gene therapy is meant to boost the production of a protein called beta sarcoglycan (beta-SG) that these patients lack. The hope is boosting beta-SG levels should change the trajectory of the disease, which causes a progressive loss of muscle function and often an early death from heart or lung problems.

To be clear, Sarepta is only reporting results today that roughly two months after treatment, the three patients, so far, are producing more beta-SG and other markers indicative of a potential impact on the disease. It doesn’t know yet how long the effects will last or whether the treatment will help stave off muscle decline. That information should be released at an upcoming medical meeting as the data mature, according to Sarepta spokesperson Tracy Sorrentino.

But the results are nonetheless encouraging. Sarepta had defined success as muscle biopsies showing 20 percent of muscle fibers with beta-SG, which is “where you would expect an improvement in function,” according to Sorrentino. So far, the average for the three patients is 51 percent of normal. Patients so far are producing beta-SG protein levels that are, on average, 36.1 percent of normal. Those patients also had more than average 90 percent decrease in levels of creatine kinase (CK); very high CK levels are indicative of muscle damage.

Sarepta did see liver enzymes spike in two patients—a common side effect of gene therapies, though one that is typically quickly reversed with a course of steroids. One of those liver enzyme increases was deemed serious, but in both cases, enzyme levels returned to normal after additional steroid treatment. Sorrentino says the trial protocol allowed for patients who hadn’t gotten steroids before to be tapered off of steroid treatment longer to control liver enzyme levels.

Taken together, the data “are significantly de-risking for [MYO-101], the remaining LGMD gene therapy assets in development, and [Sarepta’s] emerging gene therapy platform,” wrote RBC Capital Markets analyst Brian Abrahams, in a note to investors on Wednesday.

Shares of Sarepta climbed about 10 percent, to $153.95 apiece, in midday trading.

Sarepta estimates that 200,000 to 300,000 people worldwide have LGMD. The five Myonexus gene therapies target a majority of the cases of LGMD2, which covers some 80 to 90 percent of people with the disease, according to the company. Sarepta now plans to meet with the FDA to determine the next steps for MYO-101 and all of its other LGMD gene therapy programs, Sorrentino says.

Here’s more on Sarepta and its growing gene therapy ambitions.

Frank Vinluan contributed to this report.