BIIB's sNDA for Higher Dose of SMA Drug Spinraza Gets FDA's CRL

Biogen BIIB announced that the FDA has issued a complete response letter (CRL) to its supplemental new drug application (sNDA) seeking label expansion for a higher dose of its renowned spinal muscular atrophy (SMA) drug Spinraza (nusinersen).

According to the CRL, the FDA requested that an update to the technical information be added to the Chemistry, Manufacturing, and Controls section of the sNDA, without citing any deficiencies related to the clinical data of the high-dose regimen.

The company plans to resubmit the regulatory application swiftly based on readily available information to the FDA authorities. A similar regulatory application seeking approval for a higher dose of Spinraza is also under review in the EU.

More on BIIB's Regulatory Filing for the Higher Dose of Spinraza

The new higher dosing regimen will offer two initial 50 mg doses of Spinraza at gap of 14 days, followed by a 28 mg maintenance dose given every four months. Spinraza’s current regimen requires four loading doses of 12mg administered at an interval of 14 days, followed by a 12 mg maintenance dose every four months.

The new dosing regimen is likely to reduce the dosing frequency compared to the currently approved regimen, offering meaningful clinical benefits for people living with SMA.

Biogen’s regulatory filings are supported by data from the phase II/III DEVOTE study, which achieved its primary endpoint of statistically significant improvement in motor function in infants with SMA treated with a higher dose of Spinraza.

Per management, a higher dose regimen of the drug has the potential to slow neurodegeneration faster through greater reductions in neurofilament as early as day 64 relative to the currently approved dose. It believes that the maintenance of a higher drug dose over time could lead to meaningful clinical benefit in infants with symptomatic SMA.

Though the FDA issued a CRL to the sNDA, regulatory filings seeking approval for a higher dose of Spinraza are under review in the EU and some other countries.

The high-dose regimen of Spinraza was recently approved in Japan.

BIIB's Stock Performance

Shares of Biogen have lost 8.9% so far this year against the industry’s increase of 4.3%.

Rising Competition for BIIB's Spinraza

Discovered and developed jointly by Biogen and Ionis Pharmaceuticals IONS, Spinraza was the first treatment for SMA to be approved in the United States. Biogen and Ionis also market Qalsody, which was approved by the FDA in April 2023, for amyotrophic lateral sclerosis caused by superoxide dismutase 1 mutations.

Importantly, following the approval for the SMA indication, Biogen in-licensed Spinraza’s worldwide rights from IONS and assumed responsibility for its future development and commercialization.

Spinraza faces competition from Novartis’ NVS gene therapy Zolgensma and Roche RHHBY/PTC Therapeutics’ Evrysdi, both of which are approved for the SMA indication.

Competition from both NVS and RHHBY therapies has been negatively impacting Spinraza’s sales in the United States for some time now. Due to increased competitive pressure, sales of the Biogen drug declined 8.5% during the second quarter of 2025.

Biogen expects global Spinraza revenues to be relatively flat in 2025, with revenues in the second half of the year to be lower than the first half due to the unfavorable timing of shipments.

BIIB's Zacks Rank

Biogen currently carries a Zacks Rank #3 (Hold). You can see the complete list of today’s Zacks #1 Rank (Strong Buy) stocks here.

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This article originally published on Zacks Investment Research (zacks.com).

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