Homology Medicines, Inc. announced that it has nominated an in vivo gene editing development candidate and initiated IND-enabling studies for the treatment of pediatric patients with phenylketonuria (PKU). Homology also completed its internal GMP manufacturing facility with capabilities to support both gene editing and gene therapy programs. In a humanized murine model that has a liver comprised of human and murine hepatocytes, a single intravenous dose of Homology’s gene editing development candidate (HMI-103) targeting the human PAH gene demonstrated efficient editing that resulted in therapeutic levels of human PAH, as measured by edited mRNA expression of greater than ten percent in human hepatocytes. HMI-103 also demonstrated selective editing for human hepatocytes with no editing observed in murine cells in the liver. Homology plans to share details of the data in future scientific presentations and publications. Unlike Homology’s gene therapy program in PKU for adults whose livers are mature, the nuclease-free gene editing technology may offer a permanent correction in rapidly dividing cells of children. This highly efficient and precise in vivo gene editing approach leverages the body’s natural DNA repair process of homologous recombination to insert a functional copy of a gene into the genome. In addition, Homology has established new internal GMP manufacturing capabilities and expects to leverage its recently constructed 25,000 square foot facility and initial bioreactor scale of 500 liters for this gene editing program, as well as other pipeline programs. Homology has developed a scalable serum-free suspension bioreactor cell culture process and an optimized purification process that deliver robust and high-quality AAVHSC vector for both gene therapy and gene editing programs.