MaaT Pharma announced that its investigational microbiome therapy MaaT033 has successfully passed a second pre-planned safety interim analysis in the ongoing PHOEBUS Phase 2b trial. The independent Data Safety Monitoring Board (DSMB) reviewed unblinded safety data from 120 enrolled patients, including 60 patients randomized to receive MaaT033, and identified no safety concerns or excessive mortality related to the experimental treatment.
The DSMB's recommendation to continue the study without modifications represents a significant milestone for the French biotechnology company's lead candidate, which is being evaluated as an adjunctive therapy for patients undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT) for blood cancers.
World's Largest Microbiome Trial in Oncology
The PHOEBUS trial stands as the world's largest randomized controlled trial evaluating microbiome therapy in oncology. Designed as a pivotal Phase 2b study, the trial is comparing the efficacy and safety of MaaT033 versus placebo in patients receiving allo-HSCT, a critical treatment for various blood cancers.
"We are pleased to report another positive safety review for MaaT033 with the DSMB's recommendation to continue the trial without modification marking a key milestone in its development," said Hervé Affagard, Chief Executive Officer and co-founder of MaaT Pharma. "We remain fully committed to advancing this Phase 2b trial and to delivering a much-needed therapeutic option for patients fighting blood cancers and undergoing allo-HSCT."
Critical Safety Monitoring in Vulnerable Patient Population
The safety review focused on a particularly vulnerable period for patients, monitoring them for 90 days after allo-HSCT when they face heightened risk of non-relapse mortality. The study protocol includes predefined safety reviews with stopping rules if excess mortality is detected in the experimental group, underscoring the rigorous safety oversight governing the trial.
All routine safety assessments conducted every six months have consistently confirmed MaaT033's favorable safety profile and recommended trial continuation without modifications. These regular reviews support the therapy's integration into the allo-HSCT treatment setting without significant added risk of severe adverse events.
Innovative Microbiome Ecosystem Therapy
MaaT033 is a standardized, donor-derived, high-richness, high-diversity oral Microbiome Ecosystem Therapy containing anti-inflammatory ButyCore species. The therapy is designed to ensure optimal microbiota function and improve overall survival in patients receiving HSCT and other cellular therapies.
The oral capsule formulation enables outpatient administration, potentially reaching an expanded patient population of approximately 6,000 patients per year with an estimated market potential of €500 million across the EU5 and US markets. The European Medicines Agency has granted MaaT033 Orphan Drug Designation, recognizing its potential to address unmet medical needs in rare diseases.
Global Trial Expansion and Timeline
Patient enrollment for the PHOEBUS trial continues across France, Germany, Belgium, Spain, Netherlands, and the United Kingdom. The study is expected to enroll 387 patients across up to 60 clinical investigational sites. The next routine DSMB safety review is scheduled for the first quarter of 2026, maintaining the established six-month monitoring schedule.
MaaT Pharma, founded in 2014 and based in Lyon, France, has positioned itself as a pioneer in developing microbiome-driven immunomodulators for oncology. Using proprietary pooling and co-cultivation technologies, the company develops high-diversity, standardized drug candidates aimed at extending the lives of cancer patients. The company has been listed on Euronext Paris since 2021.
