On May 24, 2019, the FDA approved the first gene therapy for the treatment of spinal muscular atrophy (SMA), onasemnogene abeparvovec-xioi, which is a recombinant, self-complementary adeno-associated virus serotype 9 (AAV9) containing a transgene encoding the human survival motor neuron (SMN) protein.42,43

Patients can be treated with this therapy if they are younger than 2 years of age and have SMA characterized by bi-allelic mutations in the SMN1 gene.42,44