– Data Demonstrates Highly Efficient and Selective In Vivo Gene Editing in a Humanized Murine Model –

– New Internal GMP Manufacturing Capability to Support Gene Therapy and Gene Editing Programs –

BEDFORD, Mass., Jan. 07, 2019 (GLOBE NEWSWIRE) — Homology Medicines, Inc. (Nasdaq: FIXX), a genetic medicines company, announced today 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.

“Starting IND-enabling studies with an in vivo, nuclease-free gene editing candidate is an important milestone for Homology and achieves a key 2018 corporate goal,” said Albert Seymour, Ph.D., Chief Scientific Officer of Homology Medicines. “Our dual platform has enabled us to progress specific genetic medicine programs for PKU that may address two distinct patient populations who require different therapeutic approaches based on human biology, with gene therapy for adults and gene editing for children. We look forward to continuing to move these one-time potentially curative treatments forward as rapidly as possible.”

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.

About Phenylketonuria (PKU)
PKU is a rare, inherited inborn error of metabolism caused by a mutation in the PAH gene. The current standard of care is a highly restrictive diet, but it is not always effective. If left untreated, PKU can result in progressive and severe neurological impairment. PKU affects approximately 15,000 people in the U.S., and an estimated 300 newborns are diagnosed each year. There are currently no treatments available that address the genetic defect in PKU.

About Homology Medicines, Inc.
Homology Medicines, Inc. is a genetic medicines company dedicated to transforming the lives of patients suffering from rare genetic diseases with significant unmet medical needs by curing the underlying cause of the disease. Homology’s proprietary platform is designed to utilize its human hematopoietic stem cell-derived adeno-associated virus vectors (AAVHSCs) to precisely and efficiently deliver genetic medicines in vivo either through a gene therapy or nuclease-free gene editing modality across a broad range of genetic disorders. Homology has a management team with a successful track record of discovering, developing and commercializing therapeutics with a particular focus on rare diseases, and intellectual property covering its suite of 15 AAVHSCs. Homology believes that its compelling preclinical data, scientific expertise, product development strategy, manufacturing capabilities and intellectual property position it as a leader in the development of genetic medicines. For more information, please visit www.homologymedicines.com.

Forward-Looking Statements
This press release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. All statements contained in this press release that do not relate to matters of historical fact should be considered forward-looking statements, including statements regarding plans to share preclinical data in future scientific presentations and publications; the potential and advancement of our novel gene therapy and gene editing technology platform and pipeline, and timing thereof; our beliefs regarding our manufacturing capabilities and ability to accommodate both gene therapy and gene editing pipeline programs; our goal of improving the lives of patients with rare genetic diseases; and beliefs about our position as a leader in the development of genetic medicines. These statements are neither promises nor guarantees, but involve known and unknown risks, uncertainties and other important factors that may cause our actual results, performance or achievements to be materially different from any future results, performance or achievements expressed or implied by the forward-looking statements, including, but not limited to, the following: the fact that we have and expect to continue to incur significant losses; our need for additional funding, which may not be available; failure to identify additional product candidates and develop marketable products; the early stage of our development efforts; our failure or the failure of our collaborators to successfully develop and commercialize drug candidates; potential unforeseen events during clinical trials could cause delays or other adverse consequences; risks relating to the regulatory approval process; our product candidates may cause serious adverse side effects; inability to maintain our collaborations, or the failure of these collaborations; our reliance on third parties; the inability to obtain orphan drug exclusivity; failure to obtain international marketing approval; failure to obtain U.S. marketing approval; ongoing regulatory obligations; effects of significant competition; failure to attract, retain and motivate qualified personnel; the possibility of system failures or security breaches; risks relating to intellectual property; the price of our common stock may be volatile; significant costs as a result of operating as a public company; and any securities class action litigation. These and other important factors discussed under the caption “Risk Factors” in our Quarterly Report on Form 10-Q for the quarter ended September 30, 2018 and our other filings with the SEC could cause actual results to differ materially from those indicated by the forward-looking statements made in this press release. Any such forward-looking statements represent management’s estimates as of the date of this press release. While we may elect to update such forward-looking statements at some point in the future, we disclaim any obligation to do so, even if subsequent events cause our views to change.