MaaT Pharma’s Pivotal Phase 3 ARES Trial Results for Xervyteg® (MaaT013) in Steroid- and Ruxolitinib-Refractory GI-aGvHD Selected for Oral Presentation at ASH 2025
MaaT Pharma (EURONEXT: MAAT), a clinical-stage biotechnology company and a leader in the development of Microbiome Ecosystem Therapies™ (MET) dedicated to improving survival in cancer patients through immune modulation, today announced that pivotal results from its Phase 3 ARES trial evaluating Xervyteg® (MaaT013) in patients with gastrointestinal acute Graft-versus-Host Disease (GI-aGvHD) refractory to both steroids and ruxolitinib will be presented in an oral session at the 67th American Society of Hematology (ASH) Annual Meeting and Exposition, taking place December 6–9, 2025, in Orlando, Florida, USA.
This presentation marks the ninth consecutive year MaaT Pharma’s clinical data have been selected for ASH, and the first time the company will present Phase 3 results at a major medical congress.
For the ninth consecutive year, MaaT Pharma is proud to present data at ASH, reaffirming our position as the undisputed leader in microbiotherapy for hematology-oncology,” said Hervé Affagard, CEO and co-founder of MaaT Pharma. “The ARES study demonstrated a clinically meaningful and durable benefit in patients with gastrointestinal aGvHD, further validating our approach and its potential to redefine the standard of care for this high unmet medical need.
Pivotal Phase 3 ARES Trial Overview
The ARES trial met its primary endpoint, with topline results announced in January 2025. At ASH 2025, MaaT Pharma will present detailed findings on secondary endpoints (including GI-ORR at Day 56 and Month 3) and safety data. Final results, including 1-year overall survival, are expected by the end of 2025.
This single-arm, multicenter Phase 3 study enrolled 66 adult patients with GI-aGvHD refractory to steroids and ruxolitinib across 50 European sites in six countries (Austria, Belgium, France, Germany, Italy, and Spain). The majority of participants (91%) presented with severe GI involvement, classified as Grade III (58%) or Grade IV (33%). Among them, 86% were steroid-resistant and 14% steroid-dependent; all were refractory to ruxolitinib.
Key Efficacy Results (Data Cut-off: November 11, 2024)
- GI-Overall Response Rate (GI-ORR) at Day 28: 62% (41/66), including 38% complete responses (CR) and 20% very good partial responses (VGPR)
- Overall Response Rate (all organs) at Day 28: 64% (42/66), with 36% CR and 18% VGPR
- GI-ORR at Day 56: 49% (31/63), with 37% CR
- GI-ORR at 3 months: 44% (27/62), with 36% CR
- Average duration of response: 6.4 months
Survival Benefit
- Estimated 12-month Overall Survival (OS): 54% (median follow-up 140.5 days; median survival not reached)
- OS by Response Status at Day 28:
- Responders: 67%
- Non-responders: 28%
- p < 0.0001
- Median OS: Not reached for responders; 54 days for non-responders
These findings underscore Xervyteg® (MaaT013)’s potential to deliver a significant survival benefit in patients with refractory GI-aGvHD, a population with limited treatment options.
Regulatory Status
Xervyteg® (MaaT013) is currently under review by the European Medicines Agency (EMA) following the submission of a Marketing Authorization Application (MAA) in June 2025. A regulatory decision is anticipated in the second half of 2026.
Oral Presentation Details
Title: MaaT013 for ruxolitinib-refractory acute graft-versus-host disease with gastrointestinal involvement: Results from the ARES Phase III trial
Publication Number: 817
Presenting Author: Prof. Malard, MD, Professor of Hematology, Saint-Antoine Hospital and Sorbonne University; Lead Investigator of the ARES Trial
Session Date: December 8, 2025
Time: 10:30 AM – 10:45 AM
Session Name: 722. Allogeneic Transplantation: Acute and Chronic GVHD and Immune Reconstitution: Clinical and Translational Insights
Room: OCCC – Sunburst Room (W340)
Upcoming Scientific and Investor Conference Participation
- November 5–9, 2025 – 40th SITC Annual Meeting, National Harbor, MD, USA
- November 19–21, 2025 – SFGM-TC Annual Meeting, Geneva, Switzerland
- November 25, 2025 – Investir Day, Paris, France
- December 6–9, 2025 – 67th ASH Annual Meeting, Orlando, FL, USA
About acute Graft-versus-Host Disease
Acute Graft-versus-Host Disease occurs in patients within 100 days of undergoing a stem cell or bone marrow transplant, where the transplanted cells initiate an immune response and attack the transplant recipient’s organs, causing inflammation of the skin, liver and/or gastro-intestinal tract and leading to significant morbidity and mortality. GI involvement is associated with severe complications such as profound diarrhea, abdominal pain, intestinal bleeding, and death. These complications are often life-threatening, with increased mortality risk, due to the challenges of managing severe GI inflammation and the associated risks of infection, malnutrition, and organ failure. The standard first line therapy for treating aGvHD is the use of systemic steroids. If patients do not respond to steroids, they are considered Steroid Resistant (SR) and other agents can be administered. Currently the only agent approved for treating SR aGvHD after failure of steroid treatment is ruxolitinib, which is currently approved for this indication in USA and has received approval from the European Medicines Agency’s Committee for Human Medicinal Products (CHMP) on March 25, 2022.
About Xervyteg® (MaaT013)
MaaT Pharma’s Microbiome Ecosystem Therapies (MET) are designed to leverage a full microbiome ecosystem to restore balance and maximize clinical benefits for patients with severe, treatment-induced dysbiosis in acute diseases. Xervyteg® (MaaT013) is a full-ecosystem, off-the-shelf, standardized, pooled-donors, enema Microbiome Ecosystem TherapyTM for acute, hospital use. It is characterized by a consistently high diversity and richness of microbial species and the presence of ButycoreTM (a group of bacterial species known to produce anti-inflammatory metabolites). Xervyteg® (MaaT013) aims to restore the symbiotic relationship between the patient’s functional gut microbiome and their immune system to correct the responsiveness and tolerance of immune functions and thus reduce steroid-resistant, gastrointestinal (GI)-aGvHD. Xervyteg® (MaaT013) has been granted Orphan Drug Designation by the US Food and Drug Administration (FDA) and the European Medicines Agency (EMA).
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