Long-Term Safety and Efficacy of Apitegromab in Patients with Type 2 and Type 3 Spinal Muscular Atrophy Who Completed Previous Investigational Trials of Apitegromab

This Phase 3 extension trial (Study SRK-015-004 [ONYX]) is being conducted in ambulatory and nonambulatory patients with Type 2 and Type 3 (i.e., later-onset) SMA who completed an investigational trial of apitegromab as a monotherapy or used with an approved survival motor neuron (SMN)-targeted therapy (i.e., nusinersen [Spinraza(RegisteredTM)] or risdiplam [Evrysdi(RegisteredTM)]). The 2 feeder trials for ONYX are: 1. Study SRK-015-002 (TOPAZ) * Phase 2 Active Treatment Study to Evaluate the Efficacy and Safety of SRK-015 in Patients with Later-onset Spinal Muscular Atrophy * (NCT03921528). 2. Study SRK-015-003 (SAPPHIRE) * Phase 3, Double-Blind, Placebo-Controlled Trial to Evaluate the Efficacy and Safety of Apitegromab (SRK-015) in Patients with Later-Onset Spinal Muscular Atrophy Receiving Background Nusinersen or Risdiplam Therapy * (NCT05156320). The primary purpose of ONYX is to collect long-term safety data for patients who completed TOPAZ or SAPPHIRE. This trial will also allow patients who were receiving placebo during SAPPHIRE to receive apitegromab, thereby increasing the size of the safety database. Furthermore, this trial will allow for collection of long-term efficacy data for apitegromab.