By Fineline Cube 
Biogen Inc. (NASDAQ: BIIB) announced today that the U.S. Food & Drug Administration (FDA) has issued a Complete Response Letter (CRL) for the company’s supplemental New Drug Application (sNDA) seeking approval of a high‑dose nusinersen regimen for spinal muscular atrophy (SMA). The FDA’s letter specifically requests additional data for the Chemistry, Manufacturing, and Controls (CMC) portion of the new indication.
What the CRL Means for Biogen
- Regulatory Setback, Not a Halt – A CRL is a routine part of the FDA review process and does not preclude eventual approval; it merely signals that the agency requires further information before making a decision.
- Targeted Request – The FDA’s focus on the CMC module indicates that Biogen must provide more detailed data on the manufacturing process, quality control, and stability of the high‑dose formulation.
- Strategic Response – Biogen is expected to submit the requested information promptly, leveraging its existing manufacturing infrastructure for the 12 mg/5 mL SPINRAZA® (nusinersen) product that is already approved in more than 71 countries.
Background on SPINRAZA®
- Global Reach – SPINRAZA®, the first approved treatment for SMA, has been administered to over 14,000 patients worldwide, covering infants, children, and adults.
- Licensing and Development – Biogen holds the worldwide rights to develop, manufacture, and commercialize SPINRAZA from Ionis Pharmaceuticals, Inc. (NASDAQ: IONS).
- High‑Dose Rationale – The proposed high‑dose regimen aims to extend therapeutic benefits to patients with more advanced SMA phenotypes, potentially improving long‑term outcomes.