MaaT Pharma has announced encouraging preclinical data for its next-generation microbiome therapy, MaaT034, at the American Association for Cancer Research (AACR) Annual Meeting 2025 in Chicago. The clinical-stage French biotech company is exploring the role of microbiome ecosystem therapies in enhancing patient response to immunotherapies for cancer.

The company’s new results suggest that MaaT034 could offer a powerful new approach for solid tumor treatment by supporting the gut microbiome and strengthening the body’s immune response. MaaT Pharma said the therapy is designed to optimize the intestinal environment in order to improve outcomes when used alongside immune checkpoint inhibitors, such as anti-PD1 agents.

MaaT034 is the first therapy developed using the company’s synthetic co-culture platform, which allows the growth of complex, donor-independent microbial communities at industrial scale. This is a departure from the company’s previous therapies, MaaT013 and MaaT033, which are derived from pooled donor material and are currently in Phase 2 and Phase 3 clinical trials for patients with gut dysbiosis.

At AACR, the company presented metagenomic analyses indicating that MaaT034 closely reproduces the microbial diversity and function of MaaT013. According to MaaT Pharma, this similarity could translate to comparable clinical benefits, including improved immune modulation in cancer patients.

The preclinical findings also showed that MaaT034 enhances dendritic cell-mediated T cell activation in vitro and boosts the anti-tumor effects of anti-PD1 therapy. When tested in germ-free mice, the company observed that approximately 70% of the bacterial species in MaaT034 successfully engrafted in the gut, suggesting the potential for long-lasting colonization.

In addition, treatment with MaaT034 led to an increase in the production of beneficial metabolites such as short-chain fatty acids. These compounds play a key role in maintaining gut health and were associated with improved gastrointestinal physiology in the test animals, including restoration of gut mucosa.

Most notably, when MaaT034 was combined with anti-PD1 therapy, tumor growth was reduced by nearly 84% in mice. This was a marked improvement over anti-PD1 therapy alone, which reduced tumor growth by only 10%, and was also more effective than combining anti-PD1 with a single strain of Akkermansia muciniphila, which resulted in a 24% reduction.

“These positive data in tumor-bearing mice demonstrate the significant potential of MaaT034 as a microbiome ecosystem therapy candidate and provide a robust basis for the progression of this therapy into clinical development for solid tumors,” said Gianfranco Pittari, chief medical officer at MaaT Pharma.

The company has not yet announced a clinical timeline for MaaT034, but said the results lay important groundwork for its eventual evaluation in human studies.