Aug 25, 2026 —
Mahzi Therapeutics has received Rare Pediatric Disease Designation (RPDD) from the U.S. Food and Drug Administration (FDA) for MZ-1866, an investigational gene therapy for Pitt Hopkins syndrome, a rare neurogenetic disorder.
Pitt Hopkins syndrome is caused by deficiency of the TCF4 gene and currently has no approved disease-modifying treatment, leaving care limited to managing symptoms. MZ-1866 is an adeno-associated virus serotype 9 (AAV9) gene replacement therapy designed to address the underlying biology of the disease by delivering functional copies of the TCF4 gene, and is administered as a single dose via intracerebroventricular delivery.
RPDD is granted to therapies intended to treat serious or life-threatening diseases that primarily affect children. Upon approval of a qualifying application, therapies with the designation may be eligible for a priority review voucher. MZ-1866 has previously received Orphan Drug and Fast Track designations from the FDA.
The designation comes as the Phase 1/2 UNITE study passes the halfway mark in enrollment, with 7 of 12 planned participants enrolled and completion expected by the end of the year. The open-label trial is evaluating a single administration of the therapy across sites in the United States and Israel, with safety as the primary objective and developmental, communication, cognitive, and motor endpoints as exploratory measures. MZ-1866 was developed in collaboration with the Muotri Lab and licensed from the University of California San Diego.
