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# FDA Clinical Hold on BioMarin Phearless Study
- URL: https://www.fdaweb.com/fda-clinical-hold-on-biomarin-phearless-study/
- Published: 2021-09-07T12:00:00.000Z
- Updated: 2026-09-14T17:13:15.000Z
- Author: David McFarland
- Tags: Drugs, #legacy-id-D5150094

FDA has placed a clinical hold on the BioMarin BMN 307 Phearless Phase 1/2 study evaluating an investigational AAV5-phenylalanine hydroxylase gene therapy in adults with phenylketonuria. A company [statement](https://investors.biomarin.com/2021-09-06-U-S-FDA-Placed-a-Clinical-Hold-on-BMN-307-Phearless-Phase-1-2-Gene-Therapy-Study-in-Adults-with-PKU-Based-on-Interim-Pre-clinical-Study-Findings?ref=fdaweb.com) says the clinical hold was based on interim safety findings from a pre-clinical, non-GLP (good laboratory practice) pharmacology study.

The statement says BioMarin is pausing further enrollment in the global Phase 1/2 study pending investigation of findings of cancers in some rodents treated with the drug.