BACKGROUNDSpinal muscular atrophy is an autosomal recessive neuromuscular disorder that is caused by an insufficient level of survival motor neuron (SMN) protein. Nusinersen is an antisense oligonucleotide drug that modifies pre-messenger RNA splicing of the SMN2 gene and thus promotes increased production of full-length SMN protein. METHODSWe conducted a randomized, double-blind, sham-controlled, phase 3 efficacy and safety trial of nusinersen in infants with spinal muscular atrophy. The primary end points were a motor-milestone response (defined according to results on the Hammersmith Infant Neurological Examination) and event-free survival (time to death or the use of permanent assisted ventilation). Secondary end points included overall survival and subgroup analyses of event-free survival according to disease duration at screening. Only the first primary end point was tested in a prespecified interim analysis. To control the overall type I error rate at 0.05, a hierarchical testing strategy was used for the second primary end point and the secondary end points in the final analysis. RESULTSIn the interim analysis, a significantly higher percentage of infants in the nusinersen group than in the control group had a motor-milestone response (21 of 51 infants [41%] vs. 0 of 27 [0%], P<0.001), and this result prompted early termination of the trial. In the final analysis, a significantly higher percentage of infants in the nusinersen group than in the control group had a motor-milestone response (37 of 73 infants [51%] vs. 0 of 37 [0%]), and the likelihood of event-free survival was higher in the nusinersen group than in the control group (hazard ratio for death or the use of permanent assisted ventilation, 0.53; P = 0.005). The likelihood of overall survival was higher in the nusinersen group than in the control group (hazard ratio for death, 0.37; P = 0.004), and infants with a shorter disease duration at screening were more likely than those with a longer disease duration to benefit from nusinersen. The incidence and severity of adverse events were similar in the two groups. CONCLUSIONSAmong infants with spinal muscular atrophy, those who received nusinersen were more likely to be alive and have improvements in motor function than those in the control group. Early treatment may be necessary to maximize the benefit of the drug. (Funded by Biogen and Ionis Pharmaceuticals; ENDEAR ClinicalTrials.gov number, NCT02193074.)

In patients with SMA1, a single intravenous infusion of adeno-associated viral vector containing DNA coding for SMN resulted in longer survival, superior achievement of motor milestones, and better motor function than in historical cohorts. Further studies are necessary to confirm the safety and efficacy of this gene therapy. (Funded by AveXis and others; ClinicalTrials.gov number, NCT02122952 .).

IMPORTANCE Micro-dystrophin gene transfer shows promise for treating patients with Duchenne muscular dystrophy (DMD) using recombinant adeno-associated virus serotype rh74 (rAAVrh74) and codon-optimized human micro-dystrophin driven by a skeletal and cardiac muscle-specific promoter with enhanced cardiac expression (MHCK7). OBJECTIVE To identify the 1-year safety and tolerability of intravenous rAAVrh74.MHCK7.micro-dystrophin in patients with DMD. DESIGN, SETTING, AND PARTICIPANTS This open-label, phase 1/2a nonrandomized controlled trial was conducted at the Nationwide Children's Hospital in Columbus, Ohio. It began on November 2, 2017, with a planned duration of follow-up of 3 years, ending in March 2021. The first 4 patients who met eligibility criteria were enrolled, consisting of ambulatory male children with DMD without preexisting AAVrh74 antibodies and a stable corticosteroid dose (Ն12 weeks). INTERVENTIONS A single dose of 2.0 × 10 14 vg/kg rAAVrh74.MHCK7.micro-dystrophin was infused through a peripheral limb vein. Daily prednisolone, 1 mg/kg, started 1 day before gene delivery (30-day taper after infusion). MAIN OUTCOMES AND MEASURES Safety was the primary outcome. Secondary outcomes included micro-dystrophin expression by Western blot and immunohistochemistry. Functional outcomes measured by North Star Ambulatory Assessment (NSAA) and serum creatine kinase were exploratory outcomes. RESULTS Four patients were included (mean [SD] age at enrollment, 4.8 [1.0] years). All adverse events (n = 53) were considered mild (33 [62%]) or moderate (20 [38%]), and no serious adverse events occurred. Eighteen adverse events were considered treatment related, the most common of which was vomiting (9 of 18 events [50%]). Three patients had transiently elevated γ-glutamyltransferase, which resolved with corticosteroids. At 12 weeks, immunohistochemistry of gastrocnemius muscle biopsy specimens revealed robust transgene expression in all patients, with a mean of 81.2% of muscle fibers expressing micro-dystrophin with a mean intensity of 96% at the sarcolemma. Western blot showed a mean expression of 74.3% without fat or fibrosis adjustment and 95.8% with adjustment. All patients had confirmed vector transduction and showed functional improvement of NSAA scores and reduced creatine kinase levels (posttreatment vs baseline) that were maintained for 1 year. CONCLUSIONS AND RELEVANCE This trial showed rAAVrh74.MHCK7.micro-dystrophin to be well tolerated and have minimal adverse events; the safe delivery of micro-dystrophin transgene; the robust expression and correct localization of micro-dystrophin protein; and improvements in creatine kinase levels and NSAA scores. These findings suggest that rAAVrh74.MHCK7.micro-dystrophin can provide functional improvement that is greater than that observed under standard of care. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT03375164

Objective Infantile-onset spinal muscular atrophy (SMA) is the most common genetic cause of infant mortality, typically resulting in death prior to age 2. Clinical trials in this population require an understanding of disease progression and identification of meaningful biomarkers to hasten therapeutic development and predict outcomes. Methods A longitudinal, multi-center, prospective natural history study enrolled 26 SMA infants, and 27 control infants less than six months of age. Recruitment occurred at 14 centers over 21 months within the NINDS-sponsored NeuroNEXT Network. Infant motor function scales (TIMPSI, CHOP-INTEND and AIMS) and putative physiologic and molecular biomarkers were assessed prior to 6 months of age and at 6, 9, 12, 18 and 24-months with progression, correlations between motor function and biomarkers and hazard ratios were analyzed. Results Motor function scores (MFS) and CMAP decreased rapidly in SMA infants, whereas MFS in all healthy infants rapidly increased. Correlations were identified between TIMPSI and CMAP in SMA infants. TIMPSI at first study visit was associated with risk of combined endpoint of death or permanent invasive ventilation in SMA infants. Post hoc analysis of survival to combined endpoint in SMA infants with 2 copies of SMN2 indicated a median age of 8 months at death (95%CI: 6,17). Interpretation These data of SMA and control outcome measures delineates meaningful change in clinical trials in infantile-onset SMA. The power and utility of NeuroNEXT to provide “real world”, prospective natural history data sets to accelerate public and private drug development programs for rare disease is demonstrated.

Background: Spinal muscular atrophy type 1 (SMA1) is the leading genetic cause of infant mortality for which therapies, including AVXS-101 (onasemnogene abeparvovec, Zolgensma ® ) gene replacement therapy, are emerging. Objective: This study evaluated the effectiveness of AVXS-101 in infants with spinal muscular atrophy type 1 (SMA1) compared with a prospective natural history cohort and a cohort of healthy infants. Methods: Twelve SMA1 infants received the proposed therapeutic dose of AVXS-101 (NCT02122952). Where possible, the following outcomes were compared with a natural history cohort of SMA1 infants (n = 16) and healthy infants (n = 27) enrolled in the NeuroNEXT (NN101) study (NCT01736553): event-free survival, CHOP-INTEND scores, motor milestone achievements, compound muscle action potential (CMAP), and adverse events. Results: Baseline characteristics of SMA1 infants in the AVXS-101 and NN101 studies were similar in age and genetic profile. The proportion of AVXS-101-treated infants who survived by 24 months of follow-up was higher compared with the NN101 study (100% vs 38%, respectively). The average baseline CHOP-INTEND score for NN101 SMA1 infants was 20.3, worsening to 5.3 by age 24 months; the average baseline score in AVXS-101-treated infants was 28.2, improving to 56.5 by age 24 months. Infants receiving AVXS-101 achieved motor milestones, such as sitting unassisted and walking. Improvements in CMAP peak area were observed in AVXS-101-treated infants at 6 and 24 months (means of 1.1 and 3.2 mV/s, respectively).