ARES phase III: MaaT013 for ruxolitinib-refractory acute GvHD with GI involvement

During the 67th American Society of Hematology (ASH) Annual Meeting and Exposition, December 6–9, 2025, Orlando, US, Florent Malard presented primary results from the phase III ARES trial (NCT04769895) investigating the efficacy and safety of MaaT013 in 66 patients with steroid- or ruxolitinib-refractory acute graft-versus-host disease (aGvHD) with gastrointestinal (GI) involvement. The primary endpoint was GI-aGvHD overall response rate (ORR) at Day 28. Key secondary endpoints included GI-ORR, all-organ ORR, duration of response (DoR), and overall survival (OS). 

Key data: Day 28 GI-ORR was 62% (95% confidence interval [CI], 49–74), significantly higher than the historical control (22%; p < 0.0001). All-organ ORR was 64%, with a complete response (CR) rate of 36%. Median GI-DoR was 6.4 months (95% CI, 4.8–8.0). At Day 56 and Month 3, GI-ORR was 49% and 44%, respectively. Median OS was not reached; survival probability at 12 months was 54%. Treatment-related adverse events (TRAEs) occurred in 29% of patients, including serious adverse events (SAEs) in 9% of patients.

Key learning: MaaT013 induced frequent and deep responses, translating into prolonged survival in patients with steroid- and ruxolitinib-refractory aGvHD, supporting its potential as a microbiome-based therapy for refractory aGvHD treatment.