A single injection of onasemnogene abeparvovec (Zolgensma®) appeared to be safe and effective in a short-term follow-up of children with spinal muscular atrophy (SMA) in South Korea, according to an article published in Brain and Development.

After injection, the patients showed improvements on the Children’s Hospital of Philadelphia Infant Test of Neuromuscular Disorders (CHOP-INTEND), the Hammersmith Infant Neuromuscular Examination (HINE), and the Hammersmith Functional Motor Scale Expanded (HFMSE). One patient required 16 hours of bilevel positive airway pressure (BiPAP) prior to injection and this was able to be reduced to only 8 hours a day during sleep 6 months after treatment.

The 6 children in the study (1 with SMA type 2 and 5 with SMA type 1) received a single intravenous dose of onasemnogene when they were aged between 7 and 24 months. Prior to this injection, all patients were treated with nusinersen (Spinraza®) 4-5 times including loading doses. Nusinersen treatment was ended prior to receiving onasemnogene injections in all but 1 patient, who received 2 more doses after treatment.


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“Considering that only a single dose of intravenous injection is enough to have a clinical effect without any maintenance doses, accumulating evidence of its safety and efficacy suggest that [onasemnogene] could be the medication of choice for SMA patients,” the authors said.

Liver enzymes, including aspartate aminotransferase (AST), alanine aminotransferase (ALT), and gamma-glutamyl transferase (GGT), became elevated in all patients within 2 weeks of receiving onasemnogene. All patients were started on oral prednisolone around the time of treatment (ranging from 2 days before to 1 day after) and continued for at least 2 weeks with weekly or biweekly follow-ups until tapering. Steroid treatment lasted between 6 and 15 weeks with a mean duration of 9.5 weeks.

“It is necessary to establish a more detailed protocol of post-injection steroid treatment considering that the steroid dose or duration might affect the severity of laboratory abnormalities and require adjustment for patients’ age,” the authors said.

Blood work showed a large increase in monocyte levels and a steep decline in platelet counts within a week of treatment. While monocyte levels were increased, overall white blood cell (WBC) and absolute neutrophil counts (ANC) showed a decrease until 2 weeks after treatment when they began to return to normal levels. One patient did continue to have high AST, ALT, and WBC levels after 100 days but that was believed to be due to an infection.

Reference

Lee S, Lee YJ, Kong J, et al. Short-term clinical outcomes of onasemnogene abeparvovec treatment for spinal muscular atrophy. Brain Dev. Published online January 13, 2022. doi:10.1016/j.braindev.2021.12.006