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# FDA Can’t Approve Treosulfan NDA in its Present Form: CRL
- URL: https://www.fdaweb.com/fda-cant-approve-treosulfan-nda-in-its-present-form-crl/
- Published: 2021-08-04T12:00:00.000Z
- Updated: 2026-09-14T17:09:16.000Z
- Author: David McFarland
- Tags: Drugs, #legacy-id-D5149866

An FDA complete response letter to Medexus Pharma and its medac licensor says the agency can’t approve their NDA for treosulfan in its present form. The NDA was submitted for treosulfan in combination with fludarabine as a preparative regimen for allogeneic hematopoietic stem cell transplantation. The FDA letter provided recommendations specific to additional clinical/statistical data and analyses about the primary and secondary endpoints of the completed pivotal Phase 3 study, the companies [say](https://www.globenewswire.com/news-release/2021/08/03/2273600/0/en/Complete-Response-Letter-Received-from-FDA-for-Treosulfan.html?ref=fdaweb.com).

Company officials expressed surprise at receiving the FDA letter given treosulfan’s approval by Health Canada and the European Medicines Agency and support for it in scientific publications. They pledged to work closely with FDA to understand and address the agency's comments.