MaaT013 awaits EMA verdict after 62% GI response rate in ARES trial
The EMA is weighing approval of MaaT Pharma's fecal microbiome therapy for gut GvHD after it failed on no arm to compare against, in patients other treatments had already failed.
Executive Summary
- The EMA is reviewing MaaT013's application for a mechanism with no approved rival in this setting, and the ruling due in the back half of 2026 will decide whether the therapy reaches patients who have run out of options.
- The pivotal trial's response rates held up across multiple time points and paired with a survival split between early responders and non-responders, the kind of durability data regulators look for when a study has no control arm.
- Because ARES enrolled a single arm with no comparator, the case for approval rests on how convincingly the response and survival data stand against the historical course of a disease with no third-line standard of care, not against a head-to-head rival.
- No trial in this indication shares MaaT013's fecal-microbiome mechanism, leaving the field to unrelated antibody and small-molecule programs and making this decision the primary test of whether the approach has a regulatory path at all.
The stake
MaaT Pharma submitted a Marketing Authorization Application to the EMA in June 2025 for MaaT013, an orally-delivered fecal microbiome therapy, as third-line treatment for acute gastrointestinal graft-versus-host disease (a complication of stem cell transplants). A CHMP vote (the EMA's scientific committee) was expected around June 2026, with a final decision guided to the second half of 2026. The target population is adults with severe GI-aGvHD who are refractory to corticosteroids and ruxolitinib, a group with no approved therapy once those two lines fail. MaaTMaaT Pharma Presents the ARES Phase 3 Pivotal Trial Final Data During the Presidential Plenary Session at the 52nd Annual Meeting of the European Society for Bone and Marrow TransplantationMar 23, 2026
What the trial showed
The Phase 3 ARES trial (NCT04769895) enrolled 66 adults with Grade II-IV acute GvHD with GI involvement across 50 sites in France, Spain, Italy, Belgium, Germany, and Austria. It was single-arm and open-label, with no comparator group. GI overall response rate at Day 28 was 62% (41 of 66 patients), driven by complete response in 38% and very good partial response in 20%. The response held at 47% at Day 56 and 44% at three months. One-year overall survival was 54%, and median overall survival was not reached across the full cohort, meaning more than half the patients remained alive at the study's end. NCT04769895+1MaaT013 As Salvage Therapy in Ruxolitinib Refractory GI-aGVHD PatientsNCT04769895MaaT Pharma Presents the ARES Phase 3 Pivotal Trial Final Data During the Presidential Plenary Session at the 52nd Annual Meeting of the European Society for Bone and Marrow TransplantationMar 23, 2026
The Day 28 divide
Hematology professor Florent Malard, MD, PhD, who presented the data at the European Society for Blood and Marrow Transplantation's 2026 Presidential Plenary Session, said the response rates "together with a 54% one-year overall survival, strongly suggest that this therapeutic approach may provide a clinically meaningful benefit for these patients". The trial's own data drew a sharper line than that quote alone conveys: median overall survival was not reached among Day 28 responders, versus 54 days among non-responders, and 12-month survival ran 68% in responders against 28% in non-responders. MaaTMaaT Pharma Presents the ARES Phase 3 Pivotal Trial Final Data During the Presidential Plenary Session at the 52nd Annual Meeting of the European Society for Bone and Marrow TransplantationMar 23, 2026
No direct comparator
Among trials in acute GvHD, none shares MaaT013's gut-microbiota mechanism; the closest analogs by modality are earlier-phase cell-therapy programs testing different targets, including Cellenkos's regulatory T-cell candidate and Cynata's mesenchymal stem cell therapy, none of which have reached Phase 3. The nearest late-stage rivals in the indication, Incyte's axatilimab and Adienne's BEGEDINA, work through CSF1R and CD26 blockade rather than the microbiome, so ARES stands as the only late-stage readout for this specific mechanistic approach to gut GvHD.
Trial timeline
The registry record shows the trial's primary completion date moved twice, from May 2023 to September 2023 in mid-2022, then to November 2024 when enrollment was finalized at 66 patients, down from an earlier target of 75, as the trial's status shifted to Active, not recruiting in October 2024. That enrollment settling and status change accompanied the trial's move from recruiting into its completed-enrollment phase, consistent with a trial that finished patient entry and proceeded to its primary analysis rather than one that stalled. NCT04769895MaaT013 As Salvage Therapy in Ruxolitinib Refractory GI-aGVHD PatientsNCT04769895
This analysis was produced using AI-assisted reporting systems, AppliedXL data, and official public records. These systems undergo editorial review, quality checks, and regular audits by human experts. Errors may still occur, as with any automated system. Always consult the linked primary sources. Read our AI Editorial Policy.