The US Food and Drug Administration has placed a clinical hold on a Phase 1/2 trial of a gene therapy for adults with phenylketonuria, a genetic disorder caused by the deficiency of an enzyme needed to break down an amino acid in certain foods. The clinical hold was based on findings from a preclinical study showing that six out of seven mice receiving the highest dose of the therapy developed liver tumours. One of the tumours was cancerous. BioMarin Pharmaceutical Inc, the developer, announced the clinical hold on 6 September.
