Positive Interim Data from Study of Gene Therapy for Spinal Muscular Atrophy Type 1 Released

AveXis presented a positive interim analysis of data from its ongoing Phase 1 trial of AVXS-101 for the treatment of spinal muscular atrophy (SMA) type 1. The presentation, by Jerry Mendell, MD, director of the Center for Gene Therapy at The Research Institute at Nationwide Children’s Hospital, was given at the recent 19^th Annual Meeting of the American Society of Gene & Cell Therapy in Washington, D.C.

The clinical trial enrolled 15 patients, diagnosed before 6 months of age, with two copies of the SMN2 backup gene. Primary outcomes were defined as safety and tolerability, and a secondary outcome measures was efficacy, defined as time from birth to an “event,” either death or the need for at least 16 hours a day of ventilation support for 14 consecutive days.  Exploratory outcome measures included motor function testing, assessed by several motor milestone surveys and tests, including the Children’s Hospital of Philadelphia Infant Test of Neuromuscular Disorders (CHOP-INTEND) developed to measure motor skills in people with SMA type 1. Patients were divided in two cohorts: three, ages 6 to 7 months at time of dosing, received a low dose of 6.7 X 10^13 vg/kg (cohort 1), while the remaining 12, ages 1 to 8 months at time of dosing, received 2.0 X 10^14 vg/kg (cohort 2).

Based on the analysis, AVXS-101 continues to demonstrate a favorable safety and tolerability profile. No patients, whether in the low- or recommended therapeutic-dose cohorts, had an “event.” Moreover, mean motor function score continued to increase, and two babies achieved what is considered to be normal motor function. Mean increases of 8.7 points and 19.2 points in CHOP-INTEND scores were observed in cohort 1 and cohort 2, respectively. Nine out of 12 (75%) and 7 out of 12 (58%) patients in cohort 2 achieved CHOP-INTEND scores of at least 40 points or 50 points, respectively.

“Given the rapid and devastating disease course of SMA Type 1, it is very encouraging to see that all patients in both dosing cohorts have remained event free, and all patients have demonstrated sustained improvements above baseline in motor function since receiving AVXS-101,” Dr. Mendell said in a news release. “Additionally, new data presented today appear to indicate that AVXS-101 may have a positive impact on both the pulmonary and nutritional support of patients in the trial suffering from SMA Type 1, which may be impacting the overall survival benefit.”

AVXS-101 is a proprietary gene therapy candidate of a one-time, intravenous treatment for SMA type 1, and, according to the company, is the only clinical-stage gene therapy in development for SMA.