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

Core Viewpoint - Biogen's supplemental new drug application (sNDA) for a higher dose of Spinraza received a complete response letter (CRL) from the FDA, requesting updates to the Chemistry, Manufacturing, and Controls section without citing clinical data deficiencies [1][8]. Regulatory Developments - The company plans to resubmit the regulatory application quickly based on readily available information [2]. - A similar application for the higher dose of Spinraza is under review in the EU, while the high-dose regimen has already been approved in Japan [6][5]. Dosing Regimen - The new higher dosing regimen includes two initial 50 mg doses at a 14-day interval, followed by a 28 mg maintenance dose every four months, compared to the current regimen of four loading doses of 12 mg [3][4]. - This new regimen is expected to reduce dosing frequency and provide significant clinical benefits for SMA patients [4]. Clinical Data and Benefits - The regulatory filings are supported by data from the phase II/III DEVOTE study, which showed statistically significant improvement in motor function in infants treated with the higher dose [4]. - Management believes that the higher dose could slow neurodegeneration more effectively, with greater reductions in neurofilament observed as early as day 64 [5]. Competitive Landscape - Spinraza faces competition from Novartis' Zolgensma and Roche/PTC Therapeutics' Evrysdi, both approved for SMA, which has negatively impacted Spinraza's sales [10][11]. - Sales of Spinraza declined by 8.5% in Q2 2025 due to increased competitive pressure, and global revenues are expected to remain flat in 2025 [11]. Stock Performance - Biogen's shares have decreased by 8.9% this year, contrasting with a 4.3% increase in the industry [7].