Dugan

Dugan asked how apitegromab aims to overcome the historical hurdle of previous myostatin inhibitors in FSHD increasing muscle mass without meaningful functional improvement, and what a clinically meaningful functional improvement might entail in the planned Phase II study.

Answer

Akshay Vaishnaw, President of R&D, explained that apitegromab's higher potency and selectivity, combined with a global application strategy (unlike localized injections of prior inhibitors), are expected to yield functional benefits. He confirmed the Phase II study will use quantitative myometric testing to evaluate changes in muscle function.

Dugan inquired how apitegromab aims to overcome the historical hurdle of previous myostatin inhibitors in FSHD increasing muscle mass without meaningful functional improvement, and what a clinically meaningful functional improvement might entail in the planned Phase 2 study.

Answer

Akshay Vaishnaw, President of R&D, Scholar Rock, differentiated apitegromab from less potent/selective prior inhibitors and localized injection strategies. He noted that globally applied strategies like intense physical therapy or anabolic agents have shown increased muscle mass and functional capacity, and the Phase 2 will use lean muscle volume as the primary endpoint with on-site biomonitoring for functional impact.