Biogen Gains FDA Approval for Higher-Dose Nusinersen Following Incremental Efficacy Evidence in SMA

A separate insurance authorization for a single 50-mg loading dose is now the principal operational friction point following Biogen's March 30, 2026 FDA approval of the 28-mg nusinersen (Spinraza) regimen for spinal muscular atrophy, a detail that reimbursement and access teams will need to address before patients can transition to maintenance dosing.

Thomas Crawford, MD, a pediatric neurologist at Johns Hopkins Medicine with more than three decades of SMA experience, provided clinical context in an interview with NeurologyLive®. Crawford noted that the original 12-mg regimen had already demonstrated transformative survival outcomes, which set a high methodological bar for Biogen's dose-escalation program. The 28-mg approval ultimately rested on evidence of incremental efficacy, with safety profiles across both doses remaining broadly comparable, a profile that, in Crawford's assessment, offers no clinical rationale for remaining on the lower dose.

The loading-phase cost differential is the practical sticking point. The new protocol opens with a single 50-mg dose before patients move to 28-mg maintenance; that initial dose carries a higher unit cost and requires a discrete prior authorization, adding a reimbursement step that was absent under the original regimen. For patient access teams and payers, the authorization pathway will need to be established before the protocol can be operationalized at scale.

Crawford's broader landscape assessment is relevant for formulary and treatment-pathway decisions. All three currently approved disease-modifying therapies, nusinersen, onasemnogene abeparvovec-xioi (Zolgensma), and risdiplam (Evrysdi), are, in his view, comparably effective, with treatment selection driven by route of administration and patient tolerability rather than differential efficacy. He also characterized the growing practice of bridging patients with risdiplam ahead of a definitive therapy decision as clinically reasonable, even in the absence of formal study data supporting the approach.

Crawford introduced EVOLVE-SMA, a functional tiered classification system he is developing to track population-level disease burden in the post-DMT era. As newborn screening expands and treated patients survive into milder, longer-term phenotypes, the tool, designed for patient self-reporting, is intended to capture outcomes that existing clinical frameworks were not built to measure.

How payers respond to the 50-mg loading-dose authorization requirement will likely determine the speed at which the 28-mg protocol achieves broad clinical uptake.

Source: CGTLive® / NeurologyLive® via cgtlive.com, May 8, 2026.