Spinal muscular atrophy therapy leads to sustained motor function improvement

An investigational, fully human monoclonal antibody developed as a muscle-targeted therapy for spinal muscular atrophy showed sustained motor function improvements at 48 months, according to the manufacturer.

In the phase 2 TOPAZ extension study, Scholar Rock said in a press release that nonambulatory participants aged 2 to 21 years who were given a combination of nusinersen 20 mg/kg and apitegromab saw mean changes from baseline in Hammersmith Functional Motor Scale of 5.3 points (n = 23; 95% CI, 1.5-9.2). The change was 6.4 points (n = 19; 95% CI, 1.8-11) for nonambulatory patients aged 2 to 12 years.

“Apitegromab is being developed as a potential muscle-targeted therapy for the treatment of [spinal muscular atrophy], and Scholar Rock’s lead program is supported by new extension data from our phase 2 TOPAZ study,” Jay Backstrom, CEO of Scholar Rock, told Healio in an email. “It’s encouraging to see positive data from TOPAZ build on apitegromab’s already strong track record, and we hope to continue that with our phase 3 readout.”

Additional data cited in the release show the mean change in the Revised Upper Limb Module was 3.6 points (n = 22; 95% CI, 2-5.3) for patients aged 2 to 21 years and 4.5 (n = 18; 95% CI, 2.7-6.3) for patients 2 to 12 years.

According to the release, more than 90% of patients on combination therapy in the TOPAZ study completed 4 years of apitegromab treatment and were subsequently enrolled into the ONYX study. The ongoing open-label, multicenter extension study is evaluating the long-term safety and efficacy of apitegromab in patients with types 2 and 3 spinal muscular atrophy who completed either the TOPAZ or the phase 3 SAPPHIRE clinical trials.

Scholar Rock said in the release that topline data from SAPPHIRE are expected by the final quarter of 2024.