MaaT Pharma’s Microbiome Drug Offers Hope in a Desperate Cancer Fight

ORLANDO, FL – December 08, 2025 – In the high-stakes world of biotechnology, true breakthrough moments are rare. But at the 67th American Society of Hematology (ASH) Annual Meeting, French biotech firm MaaT Pharma delivered one, presenting pivotal data that could fundamentally alter the treatment landscape for a devastating complication of cancer therapy.

The company announced that its lead drug candidate, MaaT013 (Xervyteg®), demonstrated a remarkable 54% one-year overall survival rate in patients with an otherwise fatal condition: acute Graft-versus-Host Disease (aGvHD) that has resisted all standard treatments. For a patient population with a historically grim prognosis often measured in months, these results represent more than just a statistical victory; they offer a tangible lifeline and signal the arrival of a powerful new class of medicine: Microbiome Ecosystem Therapies (MET).

This isn't just another incremental improvement. MaaT Pharma is pioneering a new frontier by harnessing the complex ecosystem of the human gut to modulate the immune system. The success of its ARES Phase 3 trial could pave the way for the first-ever approved microbiotherapy in oncology, validating a decade of research and providing a new strategic playbook for tackling complex, immune-driven diseases.

Redefining the Last Line of Defense

To grasp the significance of MaaT Pharma’s achievement, one must first understand the brutal reality of acute Graft-versus-Host Disease. Affecting up to half of all patients who receive life-saving bone marrow or stem cell transplants, aGvHD occurs when the donor's immune cells attack the recipient's body. The gastrointestinal (GI) tract is a primary battleground, leading to severe, uncontrollable symptoms and a high risk of death.

The current treatment ladder is steep and unforgiving. High-dose corticosteroids are the first line of defense, but nearly half of patients become steroid-refractory, meaning the drugs no longer work. The next step is typically ruxolitinib, a potent JAK inhibitor. But for those who fail this second-line therapy, the path forward has been bleak, with historical survival rates plummeting below 25%.

It is this exact population—66 patients across Europe with severe GI-aGvHD refractory to both steroids and ruxolitinib—that MaaT Pharma enrolled in its single-arm ARES trial. These were patients at the end of the road. The results, presented by lead investigator Prof. Florent Malard, were striking. Not only did 62% of patients show a significant gastrointestinal response by Day 28, but the effects were durable. Nearly half of the patients maintained this response at three months.

“These results confirm that MaaT013 (Xervyteg®) offers a durable clinical benefit for patients with GI-aGvHD who have exhausted all currently approved treatment options,” stated Prof. Malard during his presentation. The most compelling statistic is the 54% one-year survival rate. Crucially, the median overall survival was not reached, meaning more than half the patients were still alive at the study's conclusion, a testament to the therapy's lasting impact. For non-responders, the median survival was a mere 54 days.

The Gut as a Drug Factory

How does MaaT013 achieve this? Instead of a single molecule targeting a single pathway, Xervyteg® is a full-ecosystem therapy. It is a standardized, off-the-shelf enema containing a diverse and rich community of microbes derived from rigorously screened, pooled healthy donors. The goal is to restore the patient's gut microbiome, which is often decimated by chemotherapy, radiation, and antibiotics—a state known as dysbiosis.

A healthy microbiome is critical for regulating the immune system. When this ecosystem collapses, the immune system can become dangerously dysregulated, contributing to the inflammatory cascade of aGvHD. By reintroducing a complete, functional microbial community, MaaT013 aims to restore balance and re-educate the patient's immune cells, tamping down the self-destructive attack while preserving the body's ability to fight infection—a key advantage over broad immunosuppressants.

This approach represents a paradigm shift from reductionist pharmacology to holistic, ecosystem-level intervention. The company’s proprietary technology ensures each dose is standardized and characterized by high diversity and the presence of ButycoreTM, a group of bacteria known to produce anti-inflammatory compounds. The strong safety profile, with no new safety signals in this fragile patient population, further bolsters its potential as a viable therapeutic.

Navigating the Regulatory and Commercial Frontier

With compelling clinical data in hand, MaaT Pharma now faces its next major challenge: navigating the path to market. The company submitted its Marketing Authorization Application to the European Medicines Agency (EMA) in June 2025, with a decision expected in mid-2026. If approved, Xervyteg® would not only be the first therapy for third-line aGvHD but also the world's first approved microbiotherapy for an oncology indication.

Being a first-in-class therapy is a double-edged sword. It offers a unique market position with little direct competition in its specific niche, but it also means forging a new regulatory path. Regulators will be scrutinizing the manufacturing, quality control, and consistency of a live biological product, areas where MaaT Pharma has invested heavily to create a standardized, pharmaceutical-grade product. The Orphan Drug Designation granted by both the EMA and the FDA provides significant advantages, including market exclusivity and regulatory support, acknowledging the critical unmet need the therapy addresses.

The commercial landscape for GvHD is evolving, with a market projected to exceed $1.4 billion in 2024. While competitors exist in the broader GvHD space, including second-line treatments and therapies for pediatric patients, MaaT Pharma has carved out a distinct and valuable position in the most refractory adult population. Success here could serve as a powerful validation of its entire MET platform.

Looking ahead, the implications extend far beyond aGvHD. A healthy microbiome is increasingly linked to the efficacy of checkpoint inhibitors, the cornerstone of modern cancer immunotherapy. MaaT Pharma is already exploring this with its next-generation pipeline, positioning the company not just as a GvHD player, but as a central innovator in the future of immuno-oncology. The results from the ARES trial may be the first major tremor signaling a seismic shift in how we approach the intersection of microbiology, immunology, and cancer treatment.