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Homology Medicines Announces FDA Lifted Clinical Hold on pheNIX Gene Therapy Trial for PKU

- Company Increased Risk-Mitigation Strategies, Including a Steroid-Sparing
Immunosuppression Regimen -

BEDFORD, Mass., June 13, 2022 -- Homology Medicines, Inc. (Nasdaq: FIXX), a genetic medicines company, announced today that the U.S. Food and Drug Administration (FDA) lifted the clinical hold previously placed on the pheNIX gene therapy clinical trial with investigational HMI-102 for adults with phenylketonuria (PKU). The FDA noted in its response that Homology satisfactorily addressed all clinical hold issues identified in its letter of March 17, 2022. Homology plans to share the changes to the protocol, which include a new steroid-sparing immunosuppression regimen that incorporates a T-cell inhibitor and a shorter course of steroids, with the clinical trial sites.

“We believe our ability to quickly and successfully respond to the FDA is a testament to our experienced clinical and regulatory teams who also applied key learnings from the gene therapy field and our clinical program to update the pheNIX trial protocol,” said Albert Seymour, Ph.D., President and Chief Scientific Officer of Homology Medicines. “We appreciate the FDA’s active collaboration during this process, and we remain committed to bringing forward potential one-time treatments for people with PKU. Our plan is to provide an update on the program this fall.”

As previously disclosed, the clinical hold on the pheNIX trial pertained to elevated liver function tests observed in the trial, which were all resolved with no hospitalizations required. Homology’s response to the FDA included changes to the protocol intended to enhance risk-mitigation measures and a new immunosuppression regimen with the T-cell inhibitor tacrolimus, which will be used in combination with a reduced duration of prophylactic steroids. The same approach is being used in Homology’s ongoing pheEDIT gene editing trial for PKU and juMPStart gene therapy trial for Hunter syndrome. Similar regimens have been shown to dampen the immune response to AAVs in the clinical setting.

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 the protocol amendments and the additional risk-mitigation measures in place for our pheNIX trial, as discussed above; our plans and timing for the release of additional preclinical and clinical data; our expectations surrounding the potential, safety, and efficacy of our product candidates; the potential of our gene therapy and gene editing platforms; 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 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; securities class action litigation; failure to attract, retain and motivate qualified personnel; the possibility of system failures or security breaches; risks relating to intellectual property; risks associated with international operations, such as political and economic instability, including in light of the conflict between Russia and Ukraine; 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 Quarterly Report on Form 10-Q for the quarter ended March 31, 2022, and our other filings with the Securities and Exchange Commission (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.

Company Contacts:
Theresa McNeely
Chief Communications Officer
and Patient Advocate
tmcneely@homologymedicines.com
781-301-7277

Media Contact:
Cara Mayfield
Vice President, Patient Advocacy
and Corporate Communications
cmayfield@homologymedicines.com
781-691-3510

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