Intrathecal onasemnogene abeparvovec for treatment-experienced patients with spinal muscular atrophy: a phase 3b, open-label trial

Intrathecal onasemnogene abeparvovec (OAV101 IT) may enable a one-time gene transfer therapy, addressing an unmet need across the broader spinal muscular atrophy (SMA) population. STRENGTH ( NCT05386680 ) was a 52-week, phase 3b, single-arm, open-label, multicenter study evaluating OAV101 IT in participants with SMA aged 2 to <18 years who discontinued nusinersen or risdiplam. The primary objective was safety/tolerability. Twenty-seven participants were enrolled (mean (s.d.) age at OAV101 IT, 7.4 (3.35) years; range, 2.4-17.7 years) with prior nusinersen or risdiplam (mean (s.d.) duration of 4.3 (1.07) years; range, 1.86-6.18 years or 3.0 (2.02); range, 0.39-6.28 years). All (n = 27) experienced at least one adverse event (AE), most frequently nasopharyngitis (n = 15, 55.6%), pyrexia (n = 14, 51.9%) and vomiting (n = 13, 48.1%). Thirteen participants (48.1%) experienced treatment-related AEs, most frequently vomiting (n = 6, 22.2%), headache (n = 4, 14.8%) and pyrexia (n = 3, 11.1%). Serious adverse events (SAEs) were reported for four participants (n = 4, 14.8%) (mostly respiratory infection related). No AEs leading to death or study discontinuation were reported. Adverse events of special interest (AESI) reported were in categories of transient thrombocytopenia (n = 8, 29.6%), hepatotoxicity (n = 4, 14.8%) and signs and symptoms that may be suggestive of dorsal root ganglia toxicity (n = 2, 7.4%). The OAV101 IT safety profile was consistent with findings in treatment-naïve patients. Trial registration: ClinicalTrials.gov identifier: NCT05386680 .