MHRA Approves New High Dose Regimen of SPINRAZA™ (nusinersen) for Spinal Muscular Atrophy

• Spinal muscular atrophy (SMA) is a rare, genetic condition that, across all types, affects ~1,600 people in the UK.1 It can cause muscle weakness which gets worse over time, causing movement, breathing and bone problems.2
• The high dose regimen represents an additional dosing option alongside the previously approved 12 mg regimen and has the potential to offer clinicians greater flexibility in managing treatment options for people living with SMA.
• Nusinersen (12 mg) has been available in the UK for almost 7 years3 and as of now, more than 14,000 people have been treated with this therapy worldwide.4

Maidenhead, 14th April 2026 – Biogen today announced that the Medicines and Healthcare Products Regulatory Agency (MHRA) has granted marketing authorisation to the high dose regimen (50/28 mg) of SPINRAZA™ (nusinersen) for the treatment of 5q spinal muscular atrophy (SMA).5 The new high dose regimen comprises of a more rapid loading phase for naïve patients than the existing 12 mg regimen, with two 50 mg loading doses administered 14 days apart, and 28 mg maintenance dose injections every four months thereafter. Individuals transitioning from the 12 mg dose will receive one 50 mg dose in place of their next 12 mg dose, followed by 28 mg maintenance doses every four months thereafter.

SMA is a rare, genetic neuromuscular condition that affects approximately 1,600 infants, children and adults in the UK. Approximately 70 children are born with SMA each year in the UK.6 5q SMA is the most common form of the disease, representing approximately 95% of all SMA cases.7 It is caused by altered copies of a gene that prevent the body from producing enough SMN (Survival of Motor Neuron) protein. This leads to damage of motor neurons in the spinal cord; signals from the brain do not reach the muscles effectively, causing progressive muscle weakness and loss of movement. Although symptoms vary, SMA is distinct because of its specific genetic cause and pattern of progression.8

“The authorisation of the high dose regimen of nusinersen in the UK marks an important milestone for the SMA community,” said Kylie Bromley, General Manager and Managing Director, United Kingdom & Ireland, Biogen. “Since Biogen secured the approval of the first treatment for SMA in the UK, we have worked hand-in-hand with clinicians and patient organisations to improve care and better meet the needs of people living with SMA, their families and caregivers. We remain committed to working collaboratively to support ongoing progress.”

Giles Lomax, CEO at Spinal Muscular Atrophy UK commented: “SMA UK welcomes the MHRA’s approval of the high dose regimen of nusinersen. This decision ensures that people living with SMA continue to have access to treatment options that can adapt to their changing needs. We are encouraged to see continued innovation in SMA care and the meaningful difference it brings to individuals and families affected by the condition.”

Dr Mariacristina Scoto, Consultant in Neuromuscular Translational Research at Great Ormond Street Hospital for Children said: “Making the high dose regimen of nusinersen available is an important step in meeting the diverse needs of the SMA community. This new dosing regimen will give clinicians more choice of treatment options which could support meaningful outcomes for patients in the UK.”

The authorisation is based on data from the three-part, Phase 2/3 DEVOTE study and its ongoing long-term extension, which assessed the high dose regimen of nusinersen in both treatment-naïve individuals and those previously treated with the 12 mg regimen. In the DEVOTE study, reported adverse events were consistent with SMA and the known safety profile of nusinersen. No new safety concerns were observed with continued use of high dose nusinersen in the long-term-extension study. In the DEVOTE study, the most common adverse events that occurred in at least 10% of participants treated with the high dose regimen, and that occurred at least 5% more frequently than the matched sham group, were pneumonia, COVID-19, pneumonia aspiration, and malnutrition.9

The high dose regimen of nusinersen is approved in the United States, the European Union, Switzerland, and Japan. Biogen is working with regulatory authorities around the world to advance the high dose regimen as an additional dosing option for people living with SMA.

References

1 Spinal Muscular Atrophy (SMA), A Brief Summary, SMA: The Numbers – SMAUK. Available at: https://smauk.org.uk/support-information/about-sma/spinal-muscular-atrophy-sma-a-brief-summary/.

2 Spinal muscular atrophy (SMA) – NHS. Available at: https://www.nhs.uk/conditions/spinal-muscular-atrophy-sma/.

3 Nusinersen for treating spinal muscular atrophy – NICE. Available at: https://www.nice.org.uk/guidance/TA588.

4 Based on commercial patients, early access patients, and clinical trial participants through December 31, 2022.

5 Spinraza (nusinersen) Summary of Product Characteristics. April 2026.

6 New NHS treatments helping extend survival for babies with rare muscle-wasting disease – NHS England. Available at: https://www.england.nhs.uk/2023/08/new-nhs-treatments-helping-extend-survival-for-babies-with-rare-muscle-wasting-disease/.

7 Spinal Muscular Atrophy – The Hong Kong Society of Neuromuscular Diseases. Available at: https://hksnmd.org/en/neuromuscular-diseases/spinal-muscular-atrophy/.

8 Spinal Muscular Atrophy (SMA), A Brief Summary, What causes 5q SMA? – SMAUK. Available at: https://smauk.org.uk/support-information/about-sma/spinal-muscular-atrophy-sma-a-brief-summary/.

9 Crawford TO, et al. Exploring Higher Doses of Nusinersen in Spinal Muscular Atrophy: Final Results From Parts B and C of the 3-Part DEVOTE Study. Presented at: World Muscle Society (WMS) Congress; 2024; Prague, Czechia.

10 Based on commercial patients, early access patients, and clinical trial participants through December 31, 2024.

11 Core Data sheet, Version 13, October 2021. SPINRAZA. Biogen Inc, Cambridge, MA.

12 Finkel RS, et al. Final Safety and Efficacy Data From the SHINE Study in Participants With Infantile-Onset and Later-Onset SMA. Presented at: Cure SMA Conference; 2024; Austin, Texas.