MaaT 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 Transplantation

Regulatory News:

MaaT Pharma (EURONEXT: MAAT the "Company"), a clinical-stage biotechnology company and a leader in the development of Microbiome Ecosystem Therapies^TM (MET) dedicated to enhancing survival for patients with cancer, today announced that Florent Malard, MD, PhD, hematology professor at Saint-Antoine Hospital and Sorbonne University, presented the final results from the Phase 3 ARES single-arm pivotal trial evaluating MaaT013 in acute Graft-versus-Host Disease (aGvHD). The presentation took place during the Presidential Plenary Session at the 2026 Annual Meeting of the European Society for Blood and Marrow Transplantation (EBMT) in Madrid, Spain. MaaT013 is currently under review by the European Medicines Agency (EMA) following the submission of a Marketing Authorization Application in June 2025, with a decision expected mid-2026, as previously disclosed.

Professor Malard emphasized that "gastrointestinal acute GvHD remains a profoundly devastating condition, associated with dismal outcomes. The response rates observed in the ARES trial-62% GI-ORR at Day 28, sustained at 47% at Day 56 and 44% at Month 3-together with a 54% one-year overall survival, strongly suggest that this therapeutic approach may provide a clinically meaningful benefit for these patients."

The final efficacy results from the ARES study, previously disclosed in December 2025, are summarized below.

The ARES trial is a single-arm, open label trial evaluating MaaT013 as third-line treatment in 66 adult patients with severe GI-aGvHD refractory to corticosteroids and ruxolitinib across 50 sites in six European countries:

Patient profile:

• 91% (n=60) presented with Grade III-IV aGvHD with GI involvement
• 86% (n=57) were steroid-resistant and 14% (n=9) steroid-dependent; all were refractory to ruxolitinib
• Male: 53%, Female: 47%

Final Efficacy Outcomes:

• GI-ORR at Day 28 occurred in 41/66 patients (62%) and prevalently consisted of complete response (CR) (38%, 25/66 patients), and very good partial response (VGPR) (20%, 13/66 patients).
• All-organ ORR at Day 28 occurred in 42/66 patients (64%) and was similarly driven by high rates of CR (36%, 24/66 patients) and VGPR (18%, 12/66 patients).
• GI-ORR at Day 56 was maintained at 47% (31/ 66 patients) and prevalently consisted of CR (35%, 23/66 patients).
• All-organ ORR at Day 56 was 45% (30/66 patients) and prevalently consisted of CR (35%, 23/66 patients).
• GI-ORR and all-organ ORR at 3 months were both 44% (29/ 66 patients), with a prevalence of CR (36%, 24/66 patients).
• A durable response was observed, with an estimated cumulative incidence of loss of response at 12 months of 20% (95% CI: 9 to 33) for GI. For all-organs, the estimated cumulative incidence of loss of response at 6 months was 26% (95% CI: 14 to 40).
• Overall survival (OS) at 12 months was 54%.
• Median overall survival was not reached, indicating that more than half of the patients were still alive at the end of the study. This suggests a durable survival benefit and reinforces the strong efficacy signal observed in the pivotal ARES study. The median OS of Day 28 responders was not reached, while it was only 54 days for Day 28 non-responders.
• The OS was significantly higher in patients who had a GI response at Day 28 than those who did not respond: 68% vs 28% respectively (p <0.0001) at 1 year, suggesting a strong association between early GI response and improved survival in refractory GI-aGvHD.
• A Data and Safety Monitoring Board (DSMB) provided ongoing safety oversight throughout the study. The final DSMB review conducted in March 2025 reported that "the study results show an acceptable safety profile and a favorable benefit /risk ratio".

The ARES trial results have been submitted to a peer-review leading medical journal for potential publication and will also be presented during an oral presentation by Professor Malard on March 27, 2026, during the annual congress of the French Society of Hematology in Paris.

In addition to the oral presentation, MaaT Pharma presents three poster communications, during the EBMT Congress:

PHOEBUS

• Title: MaaT033 for Gut Microbiota Optimization To Improve Survival after Allogeneic HCT: the Phoebus Trial
• Abstract number: A093
• Session: Transplant and Cellular Therapies Clinical
• Session Date/Time: Monday, March 23, 2026 18:00 19:00 CET
• Location: VELAZQUEZ
• Presenter: Prof. Malard, MD, PhD, hematology professor at Saint-Antoine Hospital and Sorbonne University and PHOEBUS Trial lead investigator

CHRONOS

• Title: Key results from CHRONOS, a multicenter retrospective cohort study describing real-world outcomes in third-line acute gastrointestinal GvHD
• Abstract number: B005
• Session: Graft-versus-Host Disease Clinical
• Session Date/Time: Tuesday, March 24, 2026 18:00 19:00
• Location: VELAZQUEZ
• Presenter: Johannes Clausen, MD, hematologist at Ordensklinikum Linz Elisabethinen, Hematology Department, Linz, Austria

THRASSA

• Title: THRASSA, a Multicenter Open-label Study Evaluating the Safety, Tolerability and Efficacy of MaaT013 in Ruxolitinib-Refractory or Intolerant Paediatric/Adolescent Participants with Gastrointestinal Acute Graft-versus-Host Disease
• Abstract number: P222
• Session: Paediatrics Clinical
• Session Date/Time: Sunday, March 22, 08:30 18:00 CET
• Location: e-Poster area
• Presenter: Marion Bruelle, Clinical Scientist at MaaT Pharma

About MaaT Pharma

MaaT Pharma is a leading, late-stage clinical company focused on developing innovative gut microbiome-driven therapies to modulate the immune system and enhance cancer patient survival. Supported by a talented team committed to making a difference for patients worldwide, the Company was founded in 2014 and is based in Lyon, France. As a pioneer, MaaT Pharma is leading the way in bringing the first microbiome-driven immunomodulator in oncology. Using its proprietary pooling and co-cultivation technologies, MaaT Pharma develops high diversity, standardized drug candidates, aimed at extending life of cancer patients. MaaT Pharma has been listed on Euronext Paris (ticker: MAAT) since 2021.

About MaaT013 (Xervyteg)

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. MaaT013 (brand name Xervyteg) is currently under regulatory review by the relevant authorities and has not yet received marketing authorization. MaaT013 is a full-ecosystem, off-the-shelf, standardized, pooled-donors, enema Microbiome Ecosystem Therapy^TM for acute, hospital use. It is characterized by a consistently high diversity and richness of microbial species and the presence of Butycore^TM (a group of bacterial species known to produce anti-inflammatory metabolites). 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. MaaT013 has been granted Orphan Drug Designation by the US Food and Drug Administration (FDA) and the European Medicines Agency (EMA).

About MaaT033

MaaT033, a standardized, donor-derived, high-richness, high-diversity oral Microbiome Ecosystem Therapy^TM containing anti-inflammatory Butycore^TM species, is currently being developed as an adjunctive therapy seeking to improve overall survival in patients receiving HSCT and other cellular therapies. Its aim is to seek to optimize microbiota function and to address a larger patient population in a chronic setting. MaaT033 has been granted Orphan Drug Designation by the European Medicines Agency (EMA).

Forward-looking Statements

All statements other than statements of historical fact included in this press release about future events are subject to (i) change without notice and (ii) factors beyond the Company's control. These statements may include, without limitation, any statements preceded by, followed by, or including words such as "target," "believe," "expect," "aim", "intend," "may," "anticipate," "estimate," "plan," "project," "will," "can have," "likely," "should," "would," "could" and other words and terms of similar meaning or the negative thereof. Forward-looking statements are subject to inherent risks and uncertainties beyond the Company's control that could cause the Company's actual results or performance to be materially different from the expected results or performance expressed or implied by such forward-looking statements.

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