ARES phase III final analysis: MaaT013 as third-line therapy for GI‑aGvHD

During the 52nd Annual Meeting of the European Society for Blood and Marrow Transplantation, March 22–25, 2026, Madrid, ES, Florent Malard presented final results from the phase III ARES trial (NCT04769895), evaluating the pooled allogeneic microbiota therapy MaaT013 in patients with acute graft-versus-host disease (aGvHD) with gastrointestinal involvement (GI‑aGvHD; N = 66). Eligible patients were refractory to corticosteroids and refractory/intolerant to ruxolitinib. The primary endpoint was GI‑overall response rate (GI‑ORR) at Day 28 assessed by an independent review committee (IRC).

Key data: At Day 28, the GI‑ORR was 62.1%, exceeding the pre-established threshold of 22% (p < 0.0001); most patients had complete response (CR; 37.9%) or very good partial response (VGPR; 19.7%), with 4.5% experiencing partial response (PR). The all-organ ORR at Day 28 was 63.6% (CR, 36.4%; VGPR, 18.2%; PR, 9.1%). At a median follow-up of 344.5 days, the median overall survival (OS) was not reached; OS was 54% at 12 months and was higher among Day 28 responders vs non-responders (68% vs 28%). The safety profile was consistent with that expected of the study population. Thirty‑six treatment-related adverse events (TRAEs) were reported in 29% of patients, while serious adverse events (SAEs) occurred in 80% of patients. 

Key learning: MaaT013 demonstrated deep and durable responses, encouraging survival outcomes, and a manageable safety profile in third-line GI‑aGvHD, supporting its consideration as a microbiome-based treatment option in this high-risk population.