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Phase 1/2 Study of MZ-1866, an AAV-9 Gene Therapy Delivered by Intracerebroventricular Injection to Participants With Pitt Hopkins Syndrome

Phase 1/2 First-in-Human Study to Evaluate the Safety, Tolerability, and Efficacy of MZ-1866, an AAV-9 Gene Therapy Delivered by Intracerebroventricular Injection to Participants With Pitt Hopkins Syndrome

Who can join

Ages 2 to 25 · All sexes

Inclusion Criteria:

* The participant has a TCF4 gene mutation confirmed as "pathogenic" or "likely pathogenic" by whole exome sequencing, whole genome sequencing, gene panel, single gene testing, or microarray, performed at an accredited laboratory
* Clinical phenotype consistent with Pitt Hopkins Syndrome, in the opinion of the investigator
* The participant, or the participant's parent or legal guardian, is willing to provide access to prior medical records for the collection of demographics and diagnostic and treatment history

Exclusion Criteria:

* A deletion that includes the TCF4 gene that is over 12 Mbp in size
* Another genetic mutation or clinical comorbidity not associated with Pitt Hopkins Syndrome that could potentially confound interpretation of the study data
* A central nervous system structural or vascular abnormality that is a contraindication to the ICV administration procedure, including but not limited to: signs or symptoms of increased intracranial pressure, history of a space-occupying lesion, or presence of a ventricular shunt that would preclude ICV procedures or safety assessments, or increase risk to the participant
* Not able to receive prophylactic corticosteroids due to a medical contraindication or participant has a history of a condition that could worsen with corticosteroid therapy as assessed and determined by the Investigator
* Not able to undergo MRI procedures
* Cannot be anesthetized for the ICV injection

About the study

The goal of this clinical trial is to learn if MZ-1866 is a safe and tolerable treatment for children and adults with Pitt Hopkins Syndrome.

To evaluate the safety of MZ-1866, the following will be evaluated:

* frequency and severity of adverse events * physical exam, laboratory results and electrocardiogram findings

Participants will:

* receive a single dose of MZ-1866 by intracerebroventricular injection * be seen by the study physician and site staff periodically to assess changes to their health status * be periodically evaluated using neurodevelopmental tools

Caregivers will:

* be interviewed periodically about the health status and development of the participant * keep diaries and complete periodic questionnaires regarding participant symptoms

What is being tested

• MZ-1866 (genetic)

Sponsor: Mahzi Therapeutics · Participants: 12 · Started: Dec 19, 2025

Contact the study team

• Emily Radomile · Phone: 1-844-446-2494

Official record on ClinicalTrials.gov — NCT07135050

Locations in the U.S.

From ClinicalTrials.gov, data retrieved Oct 2, 2026. Each study sets its own eligibility; the study team decides who can join.