Early treatment is more clinically effective than the combination therapy of nusinersen and onasemnogene abeparvovec-xioi for patients with spinal muscular atrophy (SMA), according to a new study published in the Journal of Clinical Medicine.

SMA is a neuromuscular disease inherited in an autosomal recessive manner. It is caused by the decreased amounts of SMN protein in the body, and type 1 SMA accounts for the majority of cases at around 55%.

Nusinersen is used to treat SMA, although the approval of other drugs specifically for SMA means that some patients are currently prescribed 2 types of therapies.

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Abeparvovec-xioi is a gene therapy that is only administered once intravenously and often added onto nusinersen for better clinical results. However, the long-term effects of the concurrent administration of both nusinersen and abeparvovec-xioi are still unknown. 

‘In this retrospective observational single center study, we evaluated safety and treatment effects of combining disease-modifying therapies, such as nusinersen and onasemnogene abeparvovec-xioi, in SMA type 1 patients,” Mirea et al wrote. 

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The research team divided the participants into 2 categories, all of them having type 1 SMA. A total of 6 participants received nusinersen first, and then onasemnogene abeparvovec-xioi later. The second group consisted of 6 patients with SMA who only received nusinersen. 

The findings of this study indicated that adding a second therapy can improve ventilation when compared to the control group. The authors discovered that abeparvovec-xioi appears to be more effective than nusinersen in terms of global survival rate, the need for assisted living, and for motor function. 

However, they put forward the idea that early diagnosis is the most important key to SMA treatment success. “Our study showed that when we include the age of the patients when treatment was initiated and other parameters, treatment efficacy depends heavily on the timing of administration,” they wrote.

“Sooner is better—ideally, before symptom-onset, which correlates with very sudden motor regression (in SMA 1 patients), associated with motor neuron loss (more than 80–90%), a subsequent drop in [compound muscle action potential] amplitude and active denervation on electromyography.”

In conclusion, the addition of genetic therapy (such as onasemnogene abeparvovc-xioi) to nusinersen offers limited benefits, and the early diagnosis and treatment of SMA result in better clinical outcomes.


Mirea A, Shelby E-S, Axente M, et al. Combination therapy with nusinersen and onasmogene aberparvovec-xioi in spinal muscular atrophy type IJ Clin Med. Published online November 26, 2021. doi:10.3390/jcm10235540