Scholar Rock soars on apitegromab SMA success

Shares of US biotech Scholar Rock (Nasdaq: SRRK) skyrocketed 362% to $34.28 by close of trading yesterday, when it announced positive top-line results from the Phase III SAPPHIRE clinical trial  evaluating the efficacy and safety of apitegromab, an investigational muscle-targeted therapy, in patients with spinal muscular atrophy (SMA).

The study achieved its primary endpoint demonstrating a statistically-significant and clinically-meaningful improvement for apitegromab versus placebo in motor function as measured by the gold standard HFMSE in SMA patients on chronic dosing of standard of care therapies (either nusinersen or risdiplam).

Based upon the similar pharmacological profile of the 20 mg/kg and 10 mg/kg doses of apitegromab, the statistical analysis plan was prespecified to analyze both the combined dose (10 mg/kg and 20 mg/kg) compared to placebo, and 20 mg/kg dose each compared to placebo. Statistical significance is achieved per the prespecified statistical analysis plan (Hochberg multiplicity adjustment) where the p-value (≤0.025) is more rigorous if only one prespecified analysis crosses the statistical significance boundary of ≤ 0.05.