Investigational Drug Improves Motor Function in Patients With SMA

Apitegromab, an investigational muscle-targeted therapy, improved motor function in patients with spinal muscular atrophy (SMA), late-stage biopharmaceutical company Scholar Rock recently announced.

The finding is from the phase 3 SAPPHIRE clinical trial (NCT05156320), which evaluated the efficacy and safety of apitegromab. The study achieved its primary endpoint by demonstrating a statistically significant and clinically meaningful improvement in motor function, as measured by the Hammersmith Functional Motor Scale Expanded (HFMSE), in patients treated with apitegromab compared with placebo.

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In the main study population, aged 2 to 12 years, the mean difference in change from baseline in HFMSE was 1.8 points for all 106 patients receiving apitegromab 10 mg/kg and 20 mg/kg compared with 50 patients receiving placebo. By dose, patients receiving 20 mg/kg of apitegromab showed a mean difference of 1.4 points compared with placebo, and patients receiving 10 mg/kg of apitegromab showed an improvement of 2.2 points compared with placebo.

Some 30.4% of patients receiving apitegromab experience HFMSE improvement greater than 3 points compared with 12.5% of patients receiving placebo. Patients receiving apitegromab demonstrated motor function improvement over placebo from the first measured time point at 8 weeks.

In an exploratory population of 32 patients aged 13 to 21 years, motor function outcomes also favored apitegromab.

Apitegromab was well-tolerated across all ages. Adverse events did not differ between the 10 mg/kg and the 20 mg/kg doses. No new safety findings were observed. Serious adverse events were consistent with the underlying disease and current standard-of-care treatments. There were no study drug discontinuations due to adverse events.

Following trial completion, 185 of the 188 patients enrolled in the ongoing ONYX open-label expansion study.

“The positive phase 3 SAPPHIRE trial, along with over 4 years of TOPAZ clinical trial data, clearly demonstrate the potentially transformative benefit of apitegromab to drive clinically meaningful improvements in motor function as measured by HFMSE in a broad SMA population, where motor function would normally be expected to generally decline over time,” said Jing Marantz, MD, PhD, chief medical officer at Scholar Rock. 

Scholar Rock plans to submit a Biologics License Application to the US Food and Drug Administration in the first quarter of 2025.

Reference

Scholar Rock reports apitegromab meets primary endpoint in phase 3 SAPPHIRE study in patients with spinal muscular atrophy (SMA). News release. Scholar Rock; October 7, 2024. Accessed October 11, 2024.