FDA, Results

Sarepta readies FDA pitch after a small study spotlights 1% dystrophin add for golodirsen in Duchenne MD

After winning an FDA approval for Exondys51 as a new therapy for Duchenne muscular dystrophy without having to actually produce data to prove it worked, Sarepta $SRPT followed up this new morning with a fresh set of data from a small study underscoring the ability of its experimental followup exon-skipping drug golodirsen to trigger added production of dystrophin.

Doug Ingram, Sarepta CEO

The numbers it cites, though, are tiny. Despite that, Sarepta is telling analysts today that it plans to see if the FDA could be willing to give it an accelerated green light.

Principal investigator Francesco Muntoni noted:

All (25) treated boys showed the anticipated exon skipping after treatment and this resulted in a mean increase of dystrophin protein, as measured by Western blot, from 0.095 percent at baseline to 1.019 percent of normal after at least one-year of treatment with golodirsen.

To underscore, that’s a claimed win with slightly more than 1% of normal dystrophin. And it will arrive at the FDA after an internal war was fought over Exondys51, which Janet Woodcock eventually won by shoving aside a lineup of regulators that tried to get in her way.

Some of the analysts found the outcome to be more than a little lean. Noted RBC’s Matthew Eckler:

Today’s release confirms the ability of Sarpeta’s exon-skipping approach to increase dystrophin in the muscles of DMD patients, in our view. However, recall that during FDA review of Exondys 51’s NDA, the agency raised concerns around the clinical benefit of producing small amounts of dystrophin (citing 10% as the threshold for clinical benefit). Indeed, one of the bear cases we hear for SRPT is that the small amount of dystrophin production and lack of a confirmed clinical benefit leave the door open to payor pushbacks and denials. We’d still expect some pushback around the headline “1% dyst. However regardless of the ultimate clinical benefit, we think that with the current data release (and possibility of accelerated approval), investors will start ascribing value to Sarepta’s pipeline, and that shares will better reflect the intrinsic value of the company beyond Exondys 51.

Brian Skorney at Baird likes it. His reasons include:

Recall Sarepta submitted baseline and 48-week treatment dystrophin analyses to the FDA last year from the PROMOVI study, which showed eteplirsen increased dystrophin from 0.16% of normal to 0.44% at week 48, a 0.28% absolute increase. Today’s SRP-4053 results are clearly more impressive, with an increase from 0.095% to 1.019% (p<0.001), almost 3.5x the dystrophin production seen in the PROMOVI patients. Getting across the 1% of normal threshold appears to be an important psychological threshold, as critics have often cited the “fraction of a percent” issue for eteplirsen.

The company is out to prove that its exon-skipping tech does work effectively, but the biotech still has a very long way to go on that score. Nevertheless, with some helpful cheerleading on the sidelines, its stock jumped 15% on the release.


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