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# BioMarin Hold Extended as FDA Seeks More Data
- URL: https://www.fdaweb.com/biomarin-hold-extended-as-fda-seeks-more-data/
- Published: 2022-02-18T12:00:00.000Z
- Updated: 2026-09-14T17:33:20.000Z
- Author: David McFarland
- Tags: Drugs, #legacy-id-D5151199

FDA has extended a clinical hold on BioMarin Pharmaceutical’s PHEARLESS Phase 1/2 study of BMN 307, an AAV5-human phenylalanine hydroxylase gene therapy being studied in adults with phenylketonuria. The trial has been on hold since 9/2021, and now FDA has requested data from additional non-clinical studies to assess the theoretical oncogenic risk to human study participants, which is expected to take several quarters, according to the company.

At the time of the initial hold, 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) said the clinical hold was based on interim safety findings from a pre-clinical, non-GLP (good laboratory practice) pharmacology study. It further said that BioMarin was pausing further enrollment in the global Phase 1/2 study pending investigation of findings of cancers in some rodents treated with the drug.