Homology Medicines Announces Upcoming Presentation on Optimized In Vivo Gene Editing Candidate HMI-103 with First Details of Unique Mechanism of Action at ASGCT Annual Meeting

- Multiple Presentations Feature HMI-103 Phase 1 Investigational Therapy for PKU, Including Genome-Wide Integration Assays to Confirm No Off-Target Editing -

- New Data from GTx-mAb Program Support Potential to Target Many

Complement-Related Disorders -

- Presentations Feature the Discovery and Characterization of a Non-Liver-Tropic Capsid and Other Distinct Properties of Homology's Family of 15 Naturally Derived AAVHSCs -

- Symposium to be Held on May 18, 2022 at 7:30 a.m. ET -

BEDFORD, Mass., May 02, 2022 (GLOBE NEWSWIRE) -- Homology Medicines, Inc. (NASDAQ:FIXX), a genetic medicines company, announced today that the first presentation detailing the optimization and mechanism of action of its HMI-103 nuclease-free gene editing candidate for phenylketonuria (PKU) will take place during the American Society for Gene & Cell Therapy (ASGCT) 25th Annual Meeting May 16-19, 2022. The data to be presented, which include a genome-wide assay that detects on- and off-target gene integration, supported the initiation of the pheEDIT trial evaluating HMI-103 for PKU, the first gene editing study for this disease. New information from the Company's GTx-mAb program, including data that further characterize the expression of C5 antibodies from AAVHSCs, will also be shared. Additionally, details on Homology's family of 15 adeno-associated viruses derived from human hematopoietic stem cells (AAVHSCs) will be presented, including one demonstrating low tropism to the liver, and the unique properties that make them amenable to developing treatments for many genetic disorders.

"Homology has focused on scientific and clinical innovation with the translation of our in vivo gene therapy and gene editing platform into one-time product candidates, and we believe that our approach to optimize nuclease-free gene editing to be unveiled at ASGCT is further evidence of our leadership in developing genetic medicines," said Albert Seymour, Ph.D., President and Chief Scientific Officer of Homology Medicines. "Our team designed assays to ensure that we can scan the entire genome to detect on- and off-target events, and the preclinical data we plan to share confirm no evidence of off-target integration or unwanted mutations. Beyond the data backing our clinical programs and pipeline, we will report structural and functional analyses of our AAVHSCs including a novel capsid with low liver tropism, which further support their broad applicability and disease-specific capsid selectivity in developing treatments for other indications."

Homology's ASGCT 2022 presentations include:

In Vivo, Nuclease-Free Gene Editing Candidate HMI-103

Sustained Correction of a Murine Model of Phenylketonuria and Integration into the Genome Following a Single Administration of an AAVHSC15 Phenylalanine Hydroxylase Gene Editing Vector

• Wednesday, May 18 at 5:30 p.m. ET
• Abstract # 1020

Genome-Wide and Directed Integration Assays Identify and Quantify rAAV In Vivo Gene Editing Sites in Mice with Humanized Livers

• Wednesday, May 18 at 5:30 p.m. ET
• Abstract # 164

GTx-mAb Program

Sustained Expression of C5mAb in Presence of Murine and Human FcRn

• Monday, May 16 at 5:30 p.m. ET
• Abstract # 365

AAVHSC Platform

rAAV Vector Breakpoints Determined Using Single-Molecule, Modified Base Sequencing

• Monday, May 16 at 11:00 a.m. ET
• Oral Presentation in Ballroom A

Naturally Occurring Variations at the 501 and 706 Residues on AAVHSC16 Contribute to Reduced Liver Tropism and Slower Serum Clearance

• Tuesday, May 17 at 5:30 p.m. ET
• Abstract # 510

The Structure of the 501 Residue on AAVHSC16 is Imperative to the Functional Binding to Cell Surface Glycans, Which is a Key Step in Successful Transduction

• Tuesday, May 17 at 5:30 p.m. ET
• Abstract # 511

AAVHSC Capsid Selection Strategy

Capsid Selection Strategy for the Development of Gene Therapies Based on Structural and Functional Analyses of a Panel of AAVHSCs

• Monday, May 16 at 5:30 p.m. ET
• Abstract # 164

The abstracts are available on the ASGCT website.

Homology Symposium and Webcast

In conjunction with the ASGCT meeting, Homology will host a symposium on Wednesday, May 18, 2022 at 7:30 a.m. ET, including guest speaker Jerry Vockley, Ph.D., M.D., FACMG, Division Director, Genetic and Genomic Medicine, Professor of Pediatrics and Human Genetics, and Director, Center for Rare Disease Therapy at the University of Pittsburgh, and Lead Principal Investigator for the pheEDIT clinical trial. A webcast will also be accessible on Homology's website in the Investors section, and the replay will be available on the website for 90 days following the presentation.

About Homology Medicines, Inc.

Homology Medicines, Inc. is a clinical-stage genetic medicines company dedicated to transforming the lives of patients suffering from rare diseases by addressing the underlying cause of the disease. The Company's clinical programs include HMI-102, an investigational gene therapy for adults with phenylketonuria (PKU); HMI-103, a gene editing candidate for PKU; and HMI-203, an investigational gene therapy for Hunter syndrome. Additional programs focus on metachromatic leukodystrophy (MLD), paroxysmal nocturnal hemoglobinuria (PNH) and other diseases. Homology's proprietary platform is designed to utilize its family of 15 human hematopoietic stem cell-derived adeno-associated virus (AAVHSCs) vectors to precisely and efficiently deliver genetic medicines in vivo through a gene therapy or nuclease-free gene editing modality, as well as to deliver one-time gene therapy to produce antibodies throughout the body through the GTx-mAb platform. Homology has a management team with a successful track record of discovering, developing and commercializing therapeutics with a focus on rare diseases. Homology believes its initial clinical data and compelling preclinical data, scientific and product development expertise and broad intellectual property position the Company as a leader in genetic medicines. For more information, 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 without limitation statements regarding our expectations surrounding the potential, safety, efficacy, and regulatory and clinical progress of our product candidates; the potential of our gene therapy and gene editing platforms; our position as a leader in the development of genetic medicines; and our participation in upcoming presentations and conferences. 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 impact of the COVID-19 pandemic on our business and operations, including our preclinical studies and clinical trials, and on general economic conditions; 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 or commercialize marketable products; the early stage of our development efforts; potential unforeseen events during clinical trials could cause delays or other adverse consequences; risks relating to the regulatory approval process; interim, topline and preliminary data may change as more patient data become available, and are subject to audit and verification procedures that could result in material changes in the final data; 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, including for the manufacture of materials for our research programs, preclinical and clinical studies; failure to obtain U.S. or international 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; and significant costs incurred as a result of operating as a public company. These and other important factors discussed under the caption "Risk Factors" in our Annual Report on Form 10-K for the year ended December 31, 2021 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.

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and Patient Advocate

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781-301-7277



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