Homology Medicines Recognizes PKU Awareness Month

A Note from Homology President and Chief Executive Officer, Arthur Tzianabos, Ph.D.

May 1, 2018 – Raising awareness of rare diseases is an important part of our work. We believe we have a responsibility to shine a light on the impact rare genetic diseases have on patients and their families. May 1st marks the beginning of Phenylketonuria (PKU) Awareness Month, providing an opportunity to reflect on Homology Medicines’ commitment to bring forward new treatments for this rare disease.

When Homology was founded, one of the first questions we sought to answer was to which diseases we should apply our gene editing and gene therapy platform to treat and potentially cure patients. After years of working in rare disease drug development, we knew we should focus our technology where it would be best suited, and PKU kept rising to the top of the list for a number of reasons: high unmet medical need, thorough understanding of the disease biology and the versatility of our platform to potentially enable therapies designed to address the broader PKU population.

PKU is a rare, inherited inborn error of metabolism caused by a mutation in the PAH gene in the liver. PAH is an enzyme that is normally expressed in the liver and is necessary to metabolize dietary phenylalanine into tyrosine, an amino acid responsible for the production of neurotransmitters. PKU results from mutations in PAH that render its enzymatic activity deficient. PKU is estimated to affect approximately 15,000 people in the U.S. and there are no treatments available that address the genetic defect in PKU. 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.

Homology is developing a potential single administration gene therapy treatment for adult patients with PKU that is designed to deliver functional copies of the PAH gene to the liver. For the pediatric population, we are employing a gene editing approach designed to correct the genetic defect at the DNA level.

Our mission is focused on curing disease and transforming patients’ lives. Drug development takes time, but we will remain committed to supporting the PKU patient community as we work towards a cure.

To learn more about PKU and to access patient resources, visit www.npkua.org.

Sincerely,

Arthur

The above commentary on PKU Awareness Month contains forward-looking statements regarding the anticipated development of our product candidates for PKU, which are subject to a number of risks and uncertainties, including those identified under the caption “Risk Factors” in our filings with the SEC.

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