Onasemnogene Abeparvovec: First Global Approval

ABSTRACT Background: Spinal muscular atrophy type 1 (SMA1) is a devastating genetic disease for which gene-replacement therapy may bring substantial survival and quality of life benefits. Objective: This study investigated the cost-effectiveness of onasemnogene abeparvovec (AVXS-101) gene-replacement therapy for SMA1. Study design: A Markov model was used to estimate the incremental cost-effectiveness ratio (ICER), expressed as cost/quality-adjusted life year ($/QALY), of AVXS-101 versus nusinersen over a lifetime. Survival, healthcare costs and QALYs were estimated using natural history data for SMA patients who achieved motor milestones (sitting/walking). Health utility weights were obtained from the CHERISH trial. Setting: USA; commercial payer perspective Participants: SMA1 infants Interventions: AVXS-101 was compared to nusinersen. Main outcome measure: The primary outcome was the ICER. Results: Expected survival (undiscounted) over a lifetime predicted by the model was 37.20 life years for AVXS-101 and 9.68 for nusinersen (discounted QALYs, 15.65 and 5.29, respectively). Using a potential AVXS-101 price range ($2.5-5.0M/treatment), the average lifetime cost/patient was $4.2–6.6M for AVXS-101 and $6.3M for nusinersen. The ICER range was (-$203,072) to $31,379 per QALY gained for AVXS-101 versus nusinersen, indicating that AVXS-101 was cost-effective with prices of ≤$5M. Conclusion: Single-dose AVXS-101 was cost-effective compared to chronic nusinersen for SMA1 patients.

Introduction Infants with spinal muscular atrophy (SMA) type 1 typically face a decline in motor function and a severely shortened life expectancy. Clinical trials for SMA type 1 therapies, onasemnogene abeparvovec (AVXS-101) and nusinersen, demonstrated meaningful improvements in efficacy (e.g., overall survival) but there were no head-to-head clinical trials assessing comparative efficacy. This study estimated the treatment effects of AVXS-101 relative to nusinersen for the treatment of SMA type 1. Methods Overall survival, event-free survival (no death or need to use permanent assisted ventilation), improvement in motor function [increase of ≥ 4 points in Children’s Hospital of Philadelphia Infant Test of Neuromuscular Disorders (CHOP-INTEND) score from baseline], and motor milestone achievements (head control, rolling over, and sitting unassisted) reported in the onasemnogene abeparvovec (AVXS-101-CL-101; NCT02122952) and nusinersen (ENDEAR; NCT02193074) clinical trials were indirectly compared using frequentist and Bayesian approaches. Results Among symptomatic infants with SMA type 1, the number needed to treat (NNT) to prevent one more death with AVXS-101 instead of nusinersen was 6.2 [95% confidence intervals (CI) = 4.1–12.2], and the probability of preventing death was 20% higher for patients treated with AVXS-101 than nusinersen [risk ratio (RR) = 1.2, 95% CI 1.1–1.3]. For event-free survival, the NNT to prevent one more event was 2.6 (95% CI 2.0–3.6) and RR was 1.6 (95% CI 1.4–1.9). For improvement in motor function, NNT was 3.5 (95% CI 2.6–5.3) and RR was 1.4 (95% CI 1.2–1.6). For milestone achievements, the NNTs were 1.4 (95% CI 1.1–1.9), 1.5 (95% CI 1.1–2.5), and 1.2 (95% CI 1.0–1.5); RRs 4.2 (95% CI 2.6–6.7), 7.8 (95% CI 3.6–17.0), and 11.2 (95% CI 5.1–24.5) for head control, rolling over, and sitting unassisted, respectively. Results were similar using the Bayesian approach. Conclusion This indirect comparison (AVXS-101-CL-101 vs. ENDEAR) among symptomatic SMA type 1 infants suggests that AVXS-101 may have an efficacy advantage relative to nusinersen for overall survival, independence from permanent assisted ventilation, motor function, and motor milestones. Funding AveXis.