The pheNIX Trial: First-in-Human Gene Therapy Trial for PKU Due to Phenylalanine Hydroxylase (PAH) Deficiency The pheNIX Trial: First-in-Human Gene Therapy Trial for PKU Due to Phenylalanine Hydroxylase (PAH) Deficiency Bodamer O, Burton B, Iles J, et al. ACMG 2021.