FDA Clears High-Dose Spinraza to Enhance SMA Clinical Outcomes

Editor’s note: this story was originally published on BioPharmInternational.com.

A new high-dose regimen of Spinraza (nusinersen) approved by FDA in March 2026 positions Biogen to extend the commercial and clinical value of a foundational SMA therapy, reinforcing lifecycle management strategies as competition intensifies across gene therapy and RNA-targeted treatment modalities.^1,2

The approval, announced on March 30, 2026, introduces a higher-dose regimen that is designed to increase drug exposure during both loading and maintenance phases. The updated protocol includes two 50 mg loading doses administered 14 days apart, followed by 28 mg maintenance doses every four months. Patients transitioning from the original 12 mg regimen can switch after a single high-dose loading phase while maintaining their established dosing schedule.¹

How does high-dose nusinersen improve clinical outcomes in SMA?

The regulatory decision was based on results from a phase 2/3 study (DEVOTE), which evaluated the higher-dose regimen in both treatment-naïve and previously treated patients. In the pivotal cohort of symptomatic infants, high-dose nusinersen demonstrated statistically significant improvements in motor function compared with a matched untreated group from a previous phase 3 trial (ENDEAR), with a mean difference of 26.19 points as measured by the Children’s Hospital of Philadelphia Infant Test of Neuromuscular Disorders scale.¹

“Optimizing the dose of nusinersen builds on a therapy that we already know can change lives,” said Richard Finkel, MD, director of the Center for Experimental Neurotherapeutics at St. Jude Children’s Research Hospital, in a company press release.¹ “The high dose regimen demonstrated meaningful clinical benefit while maintaining a well characterized safety profile. I believe High Dose Spinraza will play an important role in the future of SMA care.”

The approval builds on more than a decade of clinical and real-world data supporting nusinersen, which was the first disease-modifying therapy approved by FDA for SMA.³ Recent clinical findings have suggested that higher drug exposure may further slow neurodegeneration and improve long-term functional outcomes. Emerging data indicate that increased dosing can enhance SMN protein production, a key therapeutic mechanism, potentially addressing residual disease progression observed in some patients on standard dosing.⁴

What does this approval mean for SMA treatment sequencing strategies?

This development comes amid evolving treatment paradigms in SMA, where clinicians are increasingly focused on sequencing therapies and maximizing long-term benefit. Previous analyses have highlighted that a higher-dose nusinersen approach could play a strategic role in treatment optimization, particularly for patients who may not achieve sustained responses with existing regimens. The ability to intensify dosing without switching modalities may offer a practical alternative in a landscape that includes gene therapies and oral SMN2 splicing modifiers.⁵

“Over the past decade, Biogen has continued to listen, learn, and innovate to help advance care for people living with SMA,” said Priya Singhal, MD, executive vice president and head of Development at Biogen, in the release.¹ “[The] development of the high dose regimen reflects both the strength of that foundation and our … commitment to … optimiz[ing] treatment options.”

What does high-dose nusinersen mean for the SMA market?

High-dose nusinersen has already been approved in the European Union, Switzerland, and Japan, with rollout in the United States expected in the coming weeks, according to Biogen, which continues to work with global regulators to expand access to the updated regimen.

As SMA care evolves, the introduction of this higher-dose regimen underscores a shift toward lifecycle management strategies that extend the value of existing therapies while addressing unmet clinical needs. The approach may ultimately influence how neurologists balance efficacy, safety, and treatment sequencing in a rapidly advancing therapeutic landscape.

References

1. Biogen. FDA approves new high dose regimen of Spinraza (nusinersen) for spinal muscular atrophy. Published March 30, 2026. Accessed March 30, 2026. https://investors.biogen.com/news-releases/news-release-details/fda-approves-new-high-dose-regimen-spinrazar-nusinersen-spinal
2. Singh RN, Seo J, Singh NN. RNA in spinal muscular atrophy: therapeutic implications of targeting. Expert Opin Ther Targets. 2020;24(8):731-743. doi: 10.1080/14728222.2020.1783241 
3. FDA. FDA approves first drug for spinal muscular atrophy. Published Dec. 23, 2016. Accessed March 30, 2026. https://wayback.archive-it.org/7993/20170110185509/http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm534611.htm
4. Finkel, R. S., Crawford, T. O., Mercuri, E. et al. High-dose nusinersen for spinal muscular atrophy: a phase 3 randomized trial. Nat. Med. 2026. doi: 10.1038/s41591-025-04193-6
5. Finkel, R. S.; Ryan, M. M.; Pascual Pascual, S. I.; et al. Scientific Rationale for a Higher Dose of Nusinersen. Ann. Clin. Transl. Neurol.2022;9(6):819–829. doi: 10.1002/acn3.51562