Mahzi Therapeutics Doses First Patient in Pitt Hopkins Syndrome Gene Therapy Trial

MZ-1866 aims to address underlying disease biology for rare genetic disorder

Published on Feb. 26, 2026

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Mahzi Therapeutics, a clinical-stage biotechnology company, has dosed the first patient in its Phase 1/2 UNITE study evaluating MZ-1866, an investigational gene therapy for the treatment of Pitt Hopkins syndrome. Pitt Hopkins is a rare genetic condition affecting approximately 8,000 people in the United States, resulting from mutations in the TCF4 gene. MZ-1866 is designed to provide functional copies of the TCF4 gene to address the underlying disease biology.

Why it matters

The launch of the first investigational gene therapy trial for Pitt Hopkins syndrome represents a significant milestone for the rare disease community, bringing long-awaited hope for meaningful therapeutic progress. This trial marks a critical step toward transforming the future of care for individuals living with Pitt Hopkins.

The details

The Phase 1/2 UNITE study is a global, multicenter, open-label trial designed to assess the safety, tolerability, and preliminary efficacy of a single administration of MZ-1866 in participants with genetically confirmed Pitt Hopkins syndrome. The study aims to enroll approximately 12 participants across 5 sites in the United States, Israel, and Spain.

  • The first patient was dosed on February 25, 2026.

The players

Mahzi Therapeutics Inc.

A clinical-stage biotechnology company developing precision therapies for neurogenetic disorders.

MZ-1866

An investigational gene therapy for the treatment of Pitt Hopkins syndrome, developed in collaboration with the Muotri Lab at the University of California San Diego.

Pitt Hopkins syndrome

A rare genetic condition affecting approximately 1 in 34,000-41,000 individuals, resulting from mutations in the TCF4 gene and causing a combination of autism, developmental delay, hypotonia, ataxia, apnea/hyperventilation, severe gastrointestinal issues, and, less frequently, epilepsy.

Yael Weiss, M.D., Ph.D.

Chief Executive Officer of Mahzi Therapeutics.

Audrey Davidow

President of the Pitt Hopkins Research Foundation.

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What they’re saying

“Dosing the first patient is a significant achievement for the MZ-1866 program and for Mahzi's evolution as a clinical-stage company. We look forward to advancing this program to address a significant unmet medical need for patients with Pitt Hopkins syndrome and their families.”

— Yael Weiss, M.D., Ph.D., Chief Executive Officer of Mahzi Therapeutics (PRNewswire)

“The launch of the first investigational gene therapy trial for Pitt Hopkins syndrome represents a truly historic milestone for our community. For families who have waited years for meaningful therapeutic progress, this moment reflects countless hours of advocacy, collaboration, and perseverance. This Phase 1/2 trial brings long-held hope closer to reality and marks a critical step toward transforming the future of care for individuals living with Pitt Hopkins.”

— Audrey Davidow, President of the Pitt Hopkins Research Foundation (PRNewswire)

What’s next

The Phase 1/2 UNITE study is designed to evaluate the safety, tolerability, and preliminary efficacy of a single administration of MZ-1866 in participants with genetically confirmed Pitt Hopkins syndrome.

The takeaway

The initiation of the first gene therapy trial for Pitt Hopkins syndrome represents a significant breakthrough for the rare disease community, offering new hope for patients and their families who have long awaited meaningful therapeutic progress. This trial marks an important step towards developing a potential treatment that could address the underlying biology of this debilitating condition.