The U.S. Food and Drug Administration (FDA) on Tuesday approved dosing in Sarepta Therapeutics Inc.’s Cohort 8 of ENDEAVOR (Study 9001-103).

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The purpose of Cohort 8 is to evaluate the use of an enhanced immunosuppressive regimen as part of treatment with Elevidys (delandistrogene moxeparvovec-rokl) for non-ambulant (patients who cannot walk) individuals with Duchenne muscular dystrophy.

Data from Cohort 8 will be used to determine whether administering sirolimus before and after Elevidys infusion can help reduce acute liver injury (ALI). Sirolimus is an immunosuppressant.

Also Read: Sarepta Faces Investor Skepticism As Duchenne Data Falls Short Of Statistical Significance

This year, the company reported three fatalities linked to acute liver failure in individuals who received either Elevidys or an investigational gene therapy using the same AAVrh74 platform. One of these deaths occurred during a clinical trial for limb girdle muscular dystrophy.

The cohort will enroll approximately 25 participants in the U.S. who are unable to walk.

The immunosuppression regimen will include 14 days of peri-infusion sirolimus dosing (before Elevidys administration) and will continue for 12 weeks after Elevidys administration.

Primary endpoints include the incidence of ALI and Elevidys-dystrophin expression at 12 weeks.

Elevidys is the only approved gene therapy for Duchenne.

Study SRP-9001-103, also known as ENDEAVOR, is an open-label, Phase 1b study assessing the expression and safety of Elevidys in multiple cohorts of male patients with Duchenne.

The study has enrolled 55 participants across seven cohorts, and has dosed younger ambulatory individuals aged 2-7 at the time of treatment, older ambulant individuals, and non-ambulant individuals.

The primary endpoint in ENDEAVOR is the change from baseline in the quantity of Elevidys micro-dystrophin protein expression measured by western blot at 12 weeks.

Secondary outcome measures include change from baseline in micro-dystrophin expression measured by percent dystrophin-positive fibers at 12 weeks.

On Monday, Sarepta Therapeutics ( SRPT ) shared progress in the Phase 1/2 multiple ascending dose (MAD) clinical study of SRP-1003 (formerly ARO-DM1), an investigational small-interfering RNA (siRNA) therapeutic for type 1 myotonic dystrophy (DM1).

Cohorts 1 (1.5 mg/kg) and 2 (3 mg/kg) of the study are complete, and cohort 3 (4.5 mg/kg) is fully enrolled and ongoing.

The milestone triggered a payment of $200 million to Arrowhead Pharmaceuticals, Inc. .

Patients are currently being dosed in cohort 4 (6 mg/kg) with plans to initiate dosing in the final cohort, cohort 5 (12 mg/kg), in early 2026.

SRPT Price Action: Sarepta stock is up 1.90% at $19.27 at publication on Tuesday.

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