Scholar Rock Holding (NASDAQ: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 (NASDAQ:BIIB) Spinraza (nusinersen) and Roche Holdings AG's (OTC: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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