Patients with spinal muscular atrophy (SMA) who respond poorly to nusinersen may respond the most favorably to onasemnogene abeparvovec, according to a new study published in Gene Therapy.

Alternatively, the age of the patient at the time treatment is started may influence his or her response to onasemnogene abeparvovec. These hypotheses must be tested in larger patient populations to assess their plausibility, the authors of the study said.

They derived results from a study that assessed the tolerability and efficacy of onasemnogene abeparvovecin in 9 patients aged 1.7-48 months with SMA type 1 over the course of 3 months. Of these 9 patients, 7 were on stable nusinersen therapy before switching to onasemnogene abeparvovec.

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Researchers monitored the liver function, troponin 1 and creatine levels, platelet counts, and motor function of the patients.

They found that the median baseline Children’s Hospital of Philadelphia Infant Test of Neuromuscular Disorders (CHOP-INTEND) scores of the 7 patients who were on stable nusinersen increased significantly during nusinersen treatment and at 3 months after switching to onasemnogene abeparvovec.

Read more about nusinersen

The researchers also found that 2 patients who responded poorly to nusinersen had the biggest increase in baseline CHOP-INTEND scores at 1 and 3 months following the switch to onasemnogene abeparvovec treatment.

There were no unknown adverse events. The researchers reported that 1 patient had moderate to severe thrombocytopenia a week after onasemnogene abeparvovec administration, however, this was resolved with treatment.

Read more about onasemnogene abeparvovec

Nusinersen is an antisense oligonucleotide that aims to correct exon 7 splicing in the SMN2 gene. It is developed to treat both children and adults with SMA.

Onasemnogene abeparvovec is a gene therapy that uses an adeno-associated virus, serotype 9 vector to deliver a healthy copy of the SMN1 gene to the body. It is indicated for patients with all types of SMA, aged less than 2 years old.


Bitetti I, Lanzara V, Margiotta G, Varone A. Onasemnogene abeparvovec gene replacement therapy for the treatment of spinal muscular atrophy: a real-world observational study. Gene Ther. Published online May 24, 2022. doi:10.1038/s41434-022-00341-6