Survival, Motor Function, and Motor Milestones: Comparison of AVXS-101 Relative to Nusinersen for the Treatment of Infants with Spinal Muscular Atrophy Type 1

Adv Ther. 2019 May;36(5):1164-1176. doi: 10.1007/s12325-019-00923-8. Epub 2019 Mar 16.


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.

Keywords: AVXS-101; Indirect treatment comparison; Neuroscience; Nusinersen; Onasemnogene abeparvovec; Spinal muscular atrophy type 1 (SMA type 1).

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bayes Theorem
  • Clinical Trials as Topic
  • Disease-Free Survival
  • Female
  • Genetic Therapy
  • Humans
  • Infant
  • Male
  • Oligonucleotides / therapeutic use*
  • Spinal Muscular Atrophies of Childhood / drug therapy*
  • Survival of Motor Neuron 1 Protein*
  • Treatment Outcome


  • Oligonucleotides
  • SMN1 protein, human
  • Survival of Motor Neuron 1 Protein
  • nusinersen

Associated data

  • figshare/10.6084/m9.figshare.7775933