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Treatment with the gene therapy drug Onasemnogen Abeparvovec was associated with improved standing and the ability to walk independently in pediatric patients with presymptomatic spinal muscular atrophy (SMA) under 2 years of age. from April 17th to 22nd, 2021.
Loss of motor and respiratory function caused by SMN1 deletion or mutation typically occurs in patients with SMA. The presence of SMN2 copies (survival motor neuron 2 gene) can change the severity of the disease. Approximately 85% of patients with 3SMN2 develop symptoms in infancy. These symptoms include the inability to walk independently without help.
In the ongoing Phase 3 open label SPR1NT (ClinicalTrials.gov Identifier NCT03505099), study researchers evaluated a single intravenous infusion of Onase Semnogen Abeparvovec over 24 months in asymptomatic patients with 3 copies of SMN2 who were expected to develop SMA.
The primary outcome was the ability to stand unaided for 3 seconds or more, while the secondary outcome was independent walking. The study researchers also assessed the incidence of adverse events (AEs) and serious AEs (SAEs) related to therapy.
By June 2020, a total of 15 patients were enrolled in Cohort 2 of the study. The mean age of the patients at the last study visit was 15.2 months and the mean follow-up was 14.5 months.
The primary efficacy endpoint of unassisted standing for 3 seconds or more within the normal development window was met in 8 patients (16.9 months). The other 7 patients who did not meet the primary efficacy endpoint were all younger than 16.9 months.
In addition, 6 patients were able to walk independently, a skill that corresponds to normal development (17.6 months). The remaining patients who did not meet this endpoint were all younger than 17.6 months.
All 30 patients in the safety population (2SMN2) [n=14];; 3SMN2 [n=15];; 4SMN2 [n=1]) experienced at least 1 UE during the study. A total of 17 of 30 patients had treatment-related AE, while 7 of 13 had SAE. However, all of the SAEs resolved and were not considered to be associated with study therapy.
The study researchers concluded that treatment with onasemnogen abeparvovec with the achievement of “gross motor milestones similar to [nonSMA]This usually shows peers and shows significant therapeutic benefit. “
Strauss K., Muntoni F., Farrar M. et al. Onasemnogene abeparvovec gene therapy for presymptomatic spinal muscular atrophy (SMA): Update of the SPR1NT study in children with 3 copies of SMN2. Presented at: American Academy of Neurology’s Annual Virtual Meeting 2021; 17.-22. April 2021. Abstract S4.001