skip to page content

Homology Medicines Presents Long-Term Efficacy Data of a Single Dose of Gene Therapy Development Candidate for Treatment of Phenylketonuria

BEDFORD, Mass., October 18, 2018 – Homology Medicines, Inc. (Nasdaq: FIXX), a genetic medicines company, announced today long-term efficacy data of a single dose of its lead gene therapy candidate for the treatment of phenylketonuria (PKU), an inborn error of metabolism.

The presentation at the European Society of Gene & Cell Therapy (ESGCT) Annual Congress showed sustained reduction of phenylalanine (Phe), the surrogate biomarker for PKU. Homology plans to begin and report initial clinical data from a Phase 1/2 gene therapy trial in adults with PKU in 2019. 

“We are excited to share this long-term data demonstrating that our gene therapy development candidate can address and correct the genetic cause of PKU in a well-established animal disease model,” said Albert Seymour, Ph.D., Chief Scientific Officer of Homology Medicines. “Our approach, which delivers functional copies of the human PAH gene, may offer a one-time potential cure for PKU that would restore the natural biochemical pathway. We look forward to starting our Phase 1/2 trial and sharing initial patient data next year. In preparation for the clinic, GMP manufacturing capabilities are sufficient to support our planned clinical program, and we expect to produce supply for other pipeline programs in our new GMP Phase 1/2 manufacturing facility, which is on track to be completed this year.”

The data presented at ESGCT demonstrate that a single injection of Homology’s gene therapy candidate resulted in sustained reduction of phenylalanine to normal levels for 48 weeks post-treatment in the preclinical disease model. Importantly, levels of tyrosine increased; tyrosine is a natural byproduct of phenylalanine metabolism and is required for the production of neurotransmitters. In addition, coat color changed, which is indicative of melanin production, a byproduct of phenylalanine metabolism.

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 is estimated to affect approximately 15,000 people in the U.S. and 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

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 upcoming events and presentations; advancing our novel gene therapy and gene editing technology platform and pipeline; our expectations surrounding initiation of clinical trials for our PKU gene therapy program; the anticipated timing of completion of our GMP manufacturing facility; our beliefs regarding our manufacturing capabilities; our goal of improving the lives of patients with rare genetic diseases; the anticipated timing of the release of clinical data; beliefs about preclinical data; and 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 build out of our manufacturing facility; 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; unfavorable pricing regulations, third-party reimbursement practices or healthcare reform initiatives; product liability lawsuits; 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 June 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.

Investor Contact:
Theresa McNeely
SVP, Corporate Communications and Patient Advocacy

Media Contact:
Cara Mayfield
Senior Director, Patient Advocacy and Corporate Communications