MaaT Pharma Clears Safety Hurdle

MaaT Pharma just hit a big milestone in its Phase 2b PHOEBUS trial — the world’s largest randomized trial of microbiome therapy in cancer — with an encouraging thumbs-up from its safety monitoring board.

The company is testing MaaT033, an oral microbiome capsule, in patients who have undergone allogeneic hematopoietic stem cell transplants (allo-HSCT) — a group that’s highly vulnerable in the first few months post-transplant. The therapy is designed to modulate the immune system and potentially improve survival, without adding risk.

A pre-specified safety check was triggered after 30 patients had received MaaT033. This interim analysis focused on early mortality, a critical issue in this fragile population. The Data and Safety Monitoring Board (DSMB) reviewed unblinded data and found no safety concerns — no excess deaths in the treatment group — meaning the trial will continue as planned.

That’s a major vote of confidence in the therapy’s safety profile.

Patients undergoing allo-HSCT are in a precarious state, with a real risk of complications or death unrelated to cancer relapse. The fact that MaaT033 didn’t raise red flags at this early stage is a strong sign that the treatment is well tolerated. It also sets the stage for continuing enrollment, which is already underway across six European countries.

• PHOEBUS is a double-blind, placebo-controlled study expected to enroll 387 patients at up to 60 sites.

• MaaT033 is a standardized, freeze-dried, multi-donor microbiota therapy, designed for oral delivery — making it easier to use and more accessible.

• The next big safety readout (at 120 patients) is scheduled for Q3 2025, along with a routine six-month review.

MaaT Pharma is betting on the microbiome’s role in immune regulation — and it’s one of the few companies this far along in trying to apply that to cancer care. MaaT033 builds on the company’s earlier success with MaaT013, and its oral formulation opens the door to broader outpatient use.

If PHOEBUS continues to deliver positive results, MaaT033 could offer a novel, low-risk way to help patients recover better after stem cell transplants — and maybe reshape how we think about immune support in cancer therapy.