Quince Therapeutics presented safety data from its prior Phase 3 ATTeST clinical trial evaluating EryDex (intra-erythrocyte dexamethasone sodium phosphate) in patients with Ataxia-Telangiectasia (A-T) at the 53rd Child Neurology Society (CNS) Annual Meeting. The analysis focused on treatment-emergent adverse events (TEAEs) observed during the one-year study compared to placebo.
The key objective of the ATTeST trial was to assess the safety and tolerability of EryDex in A-T patients. A-T is a rare, inherited neurodegenerative and immunodeficiency disorder caused by mutations in the ATM gene. There are currently no approved therapeutic treatments in any global market for A-T.
Safety Profile of EryDex
The poster presentation highlighted that EryDex treatment was generally well-tolerated. Most TEAEs were reported as mild to moderate and transient, with similar incidence rates between the EryDex and placebo groups. Notably, side effects commonly associated with chronic steroid use, such as Cushingoid features, hyperglycemia, hirsutism, or hypertension, were not observed in patients treated with EryDex.
Three patients discontinued the study due to adverse events. One patient in the low-dose group experienced a serious adverse event (SAE) of B-cell lymphoma, which was deemed unlikely to be treatment-related. Two patients in the high-dose group had TEAEs of pyrexia and tachycardia (one patient, probably treatment related) and pain and pruritus (one patient, possibly treatment related). There were no TEAEs leading to death.
Ongoing Phase 3 NEAT Trial
Quince Therapeutics is currently enrolling patients in the pivotal Phase 3 NEAT (Neurologic Effects of EryDex on Subjects with A-T) clinical trial. This international, multi-center, randomized, double-blind, placebo-controlled trial is evaluating the neurological effects of EryDex treatment in patients with A-T. The company plans to enroll approximately 86 patients with A-T ages six to nine years old (primary analysis population) and approximately 20 patients with A-T ages 10 years or older.
The Phase 3 NEAT trial is being conducted under a Special Protocol Assessment (SPA) agreement with the U.S. Food and Drug Administration (FDA). Topline results are expected in the fourth quarter of 2025, with potential New Drug Application (NDA) submission to the FDA and a Marketing Authorization Application (MAA) submission to the European Medicines Agency (EMA) in 2026, assuming positive study results. The FDA has granted Fast Track designation for EryDex in A-T, highlighting its potential to address a high unmet medical need.
EryDex Mechanism of Action
The EryDex System is a drug/device combination product comprised of dexamethasone sodium phosphate (DSP) which is encapsulated and administered using a patient’s own red blood cells (autologous erythrocytes). DSP is a corticosteroid well known for its anti-inflammatory properties as well as its dose-limiting toxicity due to adrenal suppression. The EryDex System is designed to provide the efficacy of corticosteroids and to reduce or eliminate the significant adverse effects that accompany chronic use of corticosteroid treatment.
