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AVXS-101 may result in long-term motor improvements in SMA



– AVXS-101, the Food and Drug Administration–approved therapy for spinal muscular atrophy (SMA), yields rapid, sustained improvements in CHOP INTEND scores, better survival, and motor function improvements at long-term follow-up, according to an analysis presented at the annual meeting of the Child Neurology Society. The results provide a clinical demonstration of continuous expression of the SMN protein, according to the investigators. In addition, AVXS-101 is associated with reduced health care utilization in treated infants, which could decrease costs, lessen the burden on patients and caregivers, and improve quality of life.

SMA1 is a progressive neurologic disease that causes loss of the lower motor neurons in the spinal cord and brainstem. Patients have increasing muscle weakness that leads to death or the need for permanent ventilation by age 2 years. The disease results from mutations in the SMN1 gene. AVXS-101 replaces the missing or nonfunctional SMN1 with a healthy copy of a human SMN gene.

AveXis, the company that developed the therapy, enrolled 12 patients with SMA1 in a phase 1/2a study between December 2014 and December 2015. All participants received one intravenous infusion of AVXS-101. Omar Dabbous, MD, vice president of global health economics, outcomes research, and real world evidence at AveXis in Bannockburn, Ill., and colleagues evaluated participants’ rates of event-free survival (i.e., absence of death or need for permanent ventilation), pulmonary or nutritional interventions, swallowing, hospitalization, and CHOP INTEND scores, as well as therapeutic safety at 2 years.

At study completion, all patients who had received a therapeutic dose had event-free survival. Seven participants did not need daily noninvasive ventilation. Eleven participants had stable or improved swallowing. All of the latter patients fed orally, and six fed exclusively by mouth. Eleven patients spoke.

Participants had a mean of 1.4 respiratory hospitalizations per year. Mean proportion of time participants spent hospitalized was 4.4%. Mean hospitalization rate per year was 2.1, and mean length of hospital stay was 6.7 days. In addition, participants’ CHOP INTEND scores increased from baseline by 9.8 points at 1 month and by 15.4 points at 3 months. Patients who received a therapeutic dose of AVXS-101 have maintained their motor milestones at long-term follow-up, which suggests that treatment effects persist over the long term. Adverse events included elevated serum aminotransferase levels, which were reduced by prednisolone.

Dr. Dabbous is an employee of AveXis, which developed AVXS-101.

SOURCE: Dabbous O et al. CNS 2019. Abstract 199.

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