Sarepta rebounds on data for limb-girdle muscular dystrophy gene therapy

Shares in Sarepta spiked on positive data for its gene therapy for a form of muscular dystrophy, after suffering a trio of setbacks in the last few months.

The early-stage trial in limb-girdle muscular dystrophy Type 2E (LGMD2E) – a rare form of the muscle-wasting disease – showed that three patients showed improvements in muscle strength and function nine months after a single dose of Sarepta’s SRP-9003 candidate.

Using measures such as 10- and 100-metre walk tests, time to rise and a four-stair climb, the trial showed that patients treated with the gene therapy performed better than “what an age-matched, natural history group would predict,” said Sarepta. They also had significant reductions in creatine kinase, a biomarker for muscle damage.

The three subjects, aged four to 13 years, came from the first cohort in Sarepta’s trial and were assigned a single infusion of SRP-9003 at a preliminary test dose. A second higher dose will now be tested as Sarepta prepares for additional studies of SRP-9003 as well as gene therapies for other forms of LGMD, said the company’s chief executive Doug Ingram.

The phase 1/2a trial is a much-needed bit of good news for Sarepta, which was knocked back in August by the FDA’s rejection of Vyondys 53, a drug for Duchenne muscular dystrophy (DMD) that would have extended the number of patients eligible for treatment with its exon-skipping therapy.

Last week, further pressure was put on the company after a rival exon-skipping therapy from NS Pharma, targeting the same group of DMD patients, was filed for approval in the US with a chance to beat Vyondys 53 to market.

Sarepta already sells one DMD exon-skipping therapy – Exondys 51 (eteplirsen) – in the US after a controversial FDA approval in 2016, but was turned down for approval in Europe.

The new data is an important endorsement for Sarepta’s gene therapy programmes, particularly after a safety scare involving its candidate for DMD earlier this year threatened to undermine some encouraging preliminary data with the therapy. Since then, it has said the single case of rhabdomyolysis in a seven-year-old patient had been submitted “erroneously”.

Analysts at Leerink said the SRP-9003 data is “very encouraging for not only the LGMD2E programme but also the larger platform”, but sounded a note of caution for now given that the trial is small and in a heterogenous disease.

SRP-9003 is designed to deliver a gene coding for native beta-sarcoglycan protein, which is deficient in LGMD.

Shares in Sarepta recovered around 8.5% on Friday to a little over $88, but are still well down on a year-to-date high of more than $156.