Early life safety profiling of gene therapy for spinal muscular atrophy

The present study examines the safety profile of intravenous onasemnogene abeparvovec gene therapy in a real-world setting, both alone or in combination with intrathecal antisense oligonucleotide nusinersen therapy in two cohorts of patients with spinal muscular atrophy (SMA). The first cohort included eight presymptomatic infants treated solely with onasemnogene abeparvovec, while the second cohort comprised six symptomatic infants receiving onasemnogene abeparvovec and nusinersen co-therapy. All patients received the corticosteroid prednisolone coincident with gene therapy. Circulating alanine aminotransferase (ALT) and aspartate transaminase (AST) levels were measured to determine potential hepatoxicity, the primary focus of this study. Elevated ALT and AST levels were observed in one pre-symptomatic and three symptomatic patients post-treatment. However, all values returned to normal levels within 3 months of onasemnogene abeparvovec injection. Nusinersen treatment received previously or coincident with gene therapy did not impact the transient elevation of liver transaminases. This study highlights the importance of early intervention with molecular treatments for SMA and indicates that prior or coincident treatment with nusinersen is unlikely to impact safety of onasemnogene apoparvovec and could theoretically improve clinical outcomes in symptomatic infants or in those with gene therapy delayed beyond the immediate neonatal period.