Scholar Rock's Muscle Wasting Drug Excels In Pivotal Trial, Plans FDA Submission Next Year

Scholar Rock Holding SRRK stock is trading higher on Monday after the company released topline results from the Phase 3 SAPPHIRE trial of apitegromab in spinal muscular atrophy.

The study achieved its primary endpoint, demonstrating a statistically significant and clinically meaningful improvement for apitegromab versus placebo in motor function in SMA patients on chronic dosing of standard-of-care therapies.

Standard therapies include Biogen Inc‘s BIIB Spinraza (nusinersen) and Roche Holdings AG‘s RHHBY Evrysdi (risdiplam).

In the main efficacy population (ages 2-12), the mean difference in change from baseline in Hammersmith Functional Motor Scale Expanded (HFMSE) was 1.8 points (p=0.0192) for all patients receiving apitegromab 10 mg/kg and 20 mg/kg (n=106) compared to placebo (n=50).

Patients receiving 20 mg/kg of apitegromab (n=53) showed a 1.4-point mean difference compared to placebo (p=0.1149).

The prespecified analysis of the 10 mg/kg dose showed that patients receiving 10 mg/kg of apitegromab (n=53) improved by 2.2 points (nominal p=0.0121) compared to placebo.

Motor function outcomes were meaningful and consistent across the main efficacy population, and the exploratory population ages 13-21 favored apitegromab (n=22) compared to placebo (n=10).

Thirty percent of patients receiving apitegromab had a >3-point improvement in HFMSE compared to 12.5% of patients on placebo.

Patients receiving apitegromab demonstrated early motor function improvement compared to placebo from the first measured time point at 8 weeks, benefit expanded at 52 weeks as measured by HFMSE.

Treatment with apitegromab was well-tolerated across all age groups.

The company plans to submit an FDA and European marketing applications in the first quarter of 2025.

Price Action: SRRK stock is up 320.2% to $31.43 at last check Monday.

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