MaaT Pharma, a clinical-stage biotechnology company pioneering Microbiome Ecosystem Therapies™ (MET) to improve survival outcomes in patients with cancer through immune modulation, today announced the successful completion of the second pre-planned safety interim analysis of its ongoing Phase 2b PHOEBUS trial.
The analysis was conducted by the independent Data Safety Monitoring Board (DSMB), which reviewed unblinded safety data from the trial. Following its review, the DSMB recommended that the study continue without modification, citing no safety concerns or excessive mortality associated with MaaT033.
This positive update marks another major milestone in the clinical development of MaaT033, reinforcing its favorable safety profile and the company’s continued progress toward offering an innovative microbiome-based therapeutic option for patients undergoing Allogeneic Hematopoietic Stem Cell Transplantation (allo-HSCT).
A Major Step Forward for Microbiome-Based Cancer Therapy
The PHOEBUS trial represents the world’s largest randomized controlled clinical study evaluating a microbiome therapy in oncology. Designed as a pivotal Phase 2b trial, PHOEBUS is assessing the efficacy and safety of MaaT033 compared to placebo in patients receiving allo-HSCT for blood cancers.
Allo-HSCT is a life-saving procedure for many patients with hematological malignancies, but the early post-transplant period carries a high risk of non-relapse mortality, often due to infections and immune complications. MaaT033, administered as an oral capsule, aims to restore microbiome balance, thereby enhancing immune function, reducing post-transplant complications, and ultimately improving patient survival.
Positive DSMB Recommendation Reinforces Safety Confidence
During this second safety review, the DSMB evaluated data from 120 enrolled patients, including 60 who received MaaT033. Patients were monitored for 90 days post-transplant, a critical period during which complications and infection risks are most pronounced.
The DSMB concluded that there were no safety concerns and no signs of excess mortality in the MaaT033 treatment group. Consequently, the Board recommended that the study proceed according to plan, affirming confidence in the therapy’s safety profile.
“Our second DSMB review further validates the safety and tolerability of MaaT033,” said Hervé Affagard, Chief Executive Officer and Co-Founder of MaaT Pharma. “This outcome is an important milestone for our program and underscores our commitment to delivering a new therapeutic option for patients undergoing allo-HSCT. Microbiome-based interventions have the potential to reshape how we support immune recovery and reduce complications in hematology-oncology.”
Ongoing Safety Monitoring and Strong Interim Data
In addition to the two scheduled interim analyses, routine safety assessments are performed every six months throughout the PHOEBUS trial. All safety evaluations conducted so far have confirmed a consistent, favorable safety profile for MaaT033, with no indication of significant adverse effects.
The most recent DSMB decision further reinforces the company’s confidence that MaaT033 can be safely integrated into the complex treatment landscape of allo-HSCT patients, where maintaining immune balance is critical.
The next DSMB safety review is expected to take place in the first quarter of 2026, as the trial continues to progress toward full enrollment and completion.
Advancing Enrollment Across Europe
The PHOEBUS trial is actively enrolling patients across France, Germany, Belgium, Spain, the Netherlands, and the United Kingdom. The study plans to recruit a total of 387 participants and will be conducted across up to 60 leading clinical sites in Europe (ClinicalTrials.gov Identifier: NCT05762211).
MaaT Pharma is working closely with investigators and transplant centers to ensure efficient recruitment and rigorous monitoring, with the goal of generating high-quality data that will support regulatory discussions and potential future commercialization.
A Novel Oral Microbiome Therapeutic for a High-Need Population
MaaT033 represents a new generation of microbiome-based therapies designed to modulate the gut ecosystem and enhance immune recovery in immunocompromised patients. Unlike invasive procedures or injectable biologics, MaaT033 is administered orally, making it easy to integrate into post-transplant care.
The therapy is designed to target approximately 6,000 patients annually across the EU5 and U.S. markets, representing a potential €500 million market opportunity. Its oral capsule form enables outpatient administration, supporting continuity of care beyond hospital settings and reducing the burden on healthcare systems.
“Patients undergoing allo-HSCT face immense challenges — not only from their underlying disease but also from the immune and microbial disruptions that follow transplantation,” added Affagard. “With MaaT033, we aim to restore microbial diversity and immune equilibrium, ultimately improving survival and quality of life for these patients.”
The Growing Role of Microbiome Modulation in Oncology
MaaT Pharma is among the few global biotechnology companies advancing Microbiome Ecosystem Therapies™, a novel class of therapeutics designed to restore the full functional diversity of gut microbiota rather than targeting single bacterial strains.
Emerging research underscores the microbiome’s role in immune modulation, response to immunotherapies, and reduction of post-transplant complications. By rebuilding a balanced microbial environment, therapies like MaaT033 could become a key adjunct to modern cancer care.
MaaT Pharma’s pipeline also includes MaaT013, a rectally administered microbiome therapy for acute graft-versus-host disease (aGvHD), and additional candidates aimed at enhancing anti-cancer immune responses. The continued advancement of MaaT033 complements this broader portfolio, positioning the company as a leader in microbiome-driven immuno-oncology.
Looking Ahead
With the DSMB’s positive recommendation, MaaT Pharma remains focused on advancing the PHOEBUS trial toward completion. The company anticipates further data analyses and efficacy readouts in the coming phases, paving the way for potential regulatory submissions.
As microbiome-based therapies gain momentum in oncology and transplant medicine, MaaT Pharma’s continued progress with MaaT033 represents a promising step toward transforming supportive care for patients battling blood cancers and undergoing complex immune-modulating treatments.
About MaaT033
MaaT033, a standardized, donor-derived, high-richness, high-diversity oral Microbiome Ecosystem TherapyTM containing anti-inflammatory ButycoreTM species, is currently being developed as an adjunctive therapy to improve overall survival in patients receiving HSCT and other cellular therapies. It aims to ensure optimal 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).
