Apitegromab is a human monoclonal antibody that selectively inhibits myostatin activation to improve muscle function. Its efficacy was evaluated at one year in the Phase III SAPPHIRE trial, which included 188 patients with type II or III SMA who were non-ambulatory, aged 2 to 21 years, and already receiving treatment targeting the SMN protein (Spinraza or Evrysdi). Of these, 128 received apitegromab and 60 received a placebo.
- The trial was conducted in 48 hospitals in nine countries, including France, in Lille, Paris (I-Motion) and Toulouse.
- Participants aged 2 to 12 were randomly assigned to receive 10 or 20 mg/kg of apitegromab or a placebo. Those aged 13 to 21 were randomly assigned to receive 20 mg/kg of apitegromab or a placebo.
- At one year, participants receiving apitegromab showed an improvement in motor function on the HFMSE score (+1.8 points in those aged 2-12 years) compared to those receiving placebo, with an optimal dose of 10 mg/kg to stabilise or improve motor function in patients already receiving treatment for SMN.
- The HFMSE score decreased in patients receiving placebo.
- No serious adverse events were associated with apitegromab.
- After one year of follow-up, the ONYX extension phase took over, recruiting almost all participants (98%), all on apitegromab, to evaluate its long-term effects.
