Benzinga | Oct 18, 2021 08:48AM EDT

Homology Medicines Reports Initiation Of Trial For HMI-203 Gene Therapy Candidate For Adults With Hunter Syndrome

- juMPStart Trial to Evaluate First Systemic Gene Therapy Candidate for Patients with Hunter Syndrome -

BEDFORD, Mass., Oct. 18, 2021 (GLOBE NEWSWIRE) -- Homology Medicines, Inc. (NASDAQ:FIXX), a genetic medicines company, announced today that it has initiated the Phase 1 trial for HMI-203, a one-time, in vivo gene therapy candidate for the treatment of adults with mucopolysaccharidosis type II (MPS II), or Hunter syndrome. The juMPStart trial is an open-label, dose-escalation study evaluating the safety and efficacy of a single intravenous (I.V.) administration of HMI-203. Hunter syndrome is a lysosomal storage disorder caused by mutations in the iduronate 2-sulfatase (IDS) gene leading to absent or deficient I2S enzymatic activity, which causes toxic lysosomal accumulation of glycosaminoglycans (GAGs). There are no treatments currently available that address both the peripheral organ and cognitive manifestations of the disease, and there remains a high unmet medical need for patients despite the availability of enzyme replacement therapy (ERT).

"We are excited to start the Phase 1 trial for HMI-203, our investigational gene therapy for Hunter syndrome, as our team remains dedicated to improving outcomes for the patient community since our prior work developing ERT," said Arthur Tzianabos, Ph.D., President and Chief Executive Officer of Homology Medicines. "With today's milestone, we have also accomplished our goal of having three clinical programs by the end of 2021, with our gene therapy and gene editing clinical trials for PKU and the initiation of the juMPStart trial for Hunter syndrome. We are executing on this and our other programs, and we look forward to our continued collaboration with the MPS II community."

The juMPStart trial is expected to enroll up to 9 male patients ages 18-30 years old who have been diagnosed with Hunter syndrome and are currently receiving ERT. In addition to safety endpoints, the trial plans to measure plasma I2S activity, urinary GAG levels and other peripheral disease manifestations. The Phase 1 dose-escalation portion of the trial is designed to evaluate three doses of HMI-203 to potentially determine the optimal dose(s) for a future trial.

"I am pleased to work with the Homology team, as we both have a long-held and shared commitment to the MPS II community and a focus on bringing forward a one-time gene therapy to address the underlying cause of this disease," said Joseph Muenzer, M.D., Ph.D., Bryson Distinguished Professor in Pediatric Genetics at the University of North Carolina at Chapel Hill. "While weekly intravenous ERT has made a huge difference for the MPS II community, it is very time-consuming and there remains the need to address the brain disease in the severe or neuronopathic form of MPS II. I am optimistic that Homology's gene therapy approach for MPS II could make a significant impact on all aspects of the disease, including the peripheral manifestations, as well as the day-to-day lives of patients and their families, and I look forward to working with the Homology team and all of the investigators in the HMI-203 clinical trial to evaluate this approach."

Albert Seymour, Ph.D., Chief Scientific Officer of Homology Medicines, added, "We are pleased to be transitioning HMI-203 into the clinic for patients, building on the positive preclinical data we presented at scientific conferences, including the upcoming ASHG meeting. These data showed long-term expression of I2S in multiple organs, sustained secretion in the serum, reduced GAGs in all tissues tested as well as the cerebrospinal fluid, and phenotypic correction in the Hunter disease murine model following a one-time administration. We appreciated the insights from the Hunter syndrome community as we designed our clinical program, and we look forward to continuing our work together as we advance juMPStart."

In October 2021, the U.S. Food and Drug Administration (FDA) cleared the Investigational New Drug (IND) application for HMI-203 for the treatment of Hunter syndrome to proceed.