Thiogenesis Announces FDA Clearance of its Investigational New Drug Application ("IND") for a Phase 2a Clinical Trial in Leigh Syndrome Spectrum

San Diego, California--(Newsfile Corp. - June 11, 2025) - Thiogenesis Therapeutics, Corp. (TSXV: TTI) (OTCQX: TTIPF) ('Thiogenesis' or the 'Company') a clinical-stage biotechnology company developing disulfides that drive the production of intracellular cysteine, an amino acid that is a critical precursor to the generation of the master antioxidant glutathione and other important therapeutic compounds, today announced that the U.S. Food and Drug Administration ("FDA") has cleared the Company's Investigational New Drug application ("IND") for TTI-0102, for the treatment of the rare pediatric mitochondrial disease Leigh syndrome spectrum ("LSS"). The Company expects to initiate the Phase 2a clinical trial in the second half of 2025.

As a New Chemical Entity ("NCE") but also a prodrug, TTI-0102 has been cleared to start a Phase 2a clinical trial that was designed, and is to be conducted, in collaboration with Children's Hospital of Philadelphia ("CHOP"), with Zarazuela Zolkipli-Cunningham, MBChB, acting as the primary site for the trial. CHOP is a recognized leader in the field of pediatric mitochondrial medicine.

"The FDA clearance marks a critical milestone for Thiogenesis and underscores the potential of TTI-0102 to address the significant unmet needs in Leigh syndrome spectrum," said Patrice Rioux, MD, Ph.D., Chief Executive Officer of Thiogenesis. "We are honored to collaborate with Zarazuela Zolkipli-Cunningham, MBChB, Marni Falk, MD, and their expert clinical research team at CHOP to advance this promising therapy."

About the Clinical Trial:

The Phase 2a clinical trial in Leigh syndrome spectrum will be conducted in two-stages:

• Stage 1: A randomized, double-blind, placebo-controlled trial enrolling 9 patients, with 6 receiving TTI-0102 and 3 receiving placebo. This stage will evaluate safety, tolerability, efficacy, and pharmacokinetics / pharmacodynamics ("PK/PD") over a 3-month period, in adults and adolescent patients with Leigh syndrome spectrum.

• Stage 2: An open-label extension of the trial, enrolling 6 pediatric patients with Leigh syndrome spectrum, 5 years and older, all being treated with TTI-0102 for 3 months, to further assess safety, tolerability, efficacy, and PK/PD endpoints.

In the event that the trial yields positive results and receives FDA clearance, Thiogenesis intends to advance TTI-0102 to a pivotal Phase 2b/3 clinical trial in pediatric Leigh syndrome spectrum.