Mahzi Therapeutics

Market position

Mahzi operates in a segment that has attracted limited institutional capital: in 2023 only about 2% of all seed and Series A biotech dollars went to rare disease companies. The company positions itself around disorders with recently identified causative genes and with under-diagnosed patient populations expected to grow as genetic testing expands, and states its UNITE study is the first gene therapy trial for Pitt Hopkins syndrome.

The company writes patients and advocacy organizations into its capitalization table rather than treating them solely as advisors or donors, using Regulation Crowdfunding to let affected families and foundations become shareholders. It treats patient input as design input, employing a clinical outcomes researcher to build disease concept models and setting trial endpoints from what caregivers say matters most rather than assuming clinician-default measures such as seizure reduction.

Technology

AAV9-based gene replacement therapy and antisense oligonucleotide (RNA-based) approaches for monogenic neurodevelopmental disorders. MZ-1866 uses TCF4 isoform B, the longest known and one of the most abundant brain isoforms, in an AAV9 expression cassette under multimer E box regulatory control, delivered by intracerebroventricular administration. Human brain organoid models of Pitt-Hopkins syndrome, which revealed human-specific TCF4-dependent abnormalities and the reversibility of TCF4 mutation effects, underpinned development of the regulated AAV gene therapy. The company also constructs a "disease concept model" for each disorder and runs natural history studies in parallel with clinical development to define endpoints.

Go-to-market

Mahzi partners closely with disease-specific advocacy groups, holding monthly meetings with the communities for its lead indications (SCAR12/WOREE, Pitt-Hopkins, CHD2), and interviews families in depth before writing trial protocols so that parent-prioritized outcomes become measured endpoints. It works with global nonprofits including Global Genes and the Rare Epilepsy Network on workshops aimed at accelerating new therapies, and collaborates with CRO CTI Clinical Trial & Consulting Services and the Pitt Hopkins Research Foundation on clinical development. A Regulation Crowdfunding community round, run by Capital Department, opens equity participation to affected families at a $250 minimum.

Patients with under-diagnosed and under-served rare genetic neurodevelopmental disorders and their families, including those affected by Pitt Hopkins syndrome (TCF4), WWOX-related disorders (WOREE, SCAR12), and CHD2 deficiency; the company works alongside disease advocacy foundations and academic investigators.

Geography

Headquartered in South San Francisco, California. Clinical and research activities extend internationally, with UNITE trial sites planned in the United States, Israel, and Spain, and academic collaborations at UC San Diego, Hebrew University of Jerusalem, and the Weizmann Institute of Science in Rehovot, Israel.

History

Founded by Yael Weiss to advance rare neurodevelopmental disease programs originating in academic labs, the company assembled programs in Pitt Hopkins syndrome (with UCSD), WWOX-related disorders (Hebrew University), and CHD2 deficiency (Weizmann Institute). Weiss was recognized as a 2022 Henri Termeer Fellow. In 2025 the company described an imminent IND filing for its AAV9 TCF4 program; it subsequently announced a collaboration with CTI Clinical Trial & Consulting Services and the Pitt Hopkins Research Foundation, dosed the first patient in the Phase 1/2 UNITE study of MZ-1866, and received FDA Rare Pediatric Disease Designation for MZ-1866, which had previously received Orphan Drug and Fast Track designations.

Risks & controversies

Rare disease biotech financing is constrained, with only about 2% of seed and Series A biotech dollars going to rare disease companies in 2023, and the CEO describes the 2025 fundraising environment as substantially harder than during the pandemic, prompting reliance on non-traditional capital. The lead indications have never been studied in clinical trials, so endpoints and natural history must be established de novo, and target patient populations are small and uncertain in size — estimates for Pitt-Hopkins range from roughly 500 individuals worldwide (Cleveland Clinic) to about 1,500 affected families (Pitt Hopkins Research Foundation).