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# FDA ‘Unable to Approve’ Tysabri sBLA
- URL: https://www.fdaweb.com/fda-unable-to-approve-tysabri-sbla/
- Published: 2021-04-29T12:00:00.000Z
- Updated: 2026-09-14T16:57:01.000Z
- Author: David McFarland
- Tags: Drugs, #legacy-id-D5149216

FDA has sent a complete response letter (CRL) to Biogen for its sBLA for a new subcutaneous route of administration of Tysabri (natalizumab) to treat relapsing multiple sclerosis. The company [says](https://investors.biogen.com/news-releases/news-release-details/biogen-provides-regulatory-update-supplemental-biologic-license?ref=fdaweb.com) it is evaluating the CRL and will determine the next steps.