AACR 2025: MaaT Pharma, the gut microbiome, and immuno-oncology

Lyon, France-based late-stage clinical biotech MaaT Pharma has presented new preclinical data for MaaT034 at the American Association for Cancer Research (AACR) annual meeting 2025 in Chicago, US – with compelling anti-tumour efficacy results.

A leader in the development of Microbiome Ecosystem Therapies (METs), MaaT’s platform combines two complementary approaches. 

MaaT013 and MaaT033 leverage a GMP-compliant approach to produce standardised donor-derived therapies using pooled donations in order to restore the gut microbiome in patients with severe dysbiosis (in Phases 2 and 3, respectively).

The second approach advances next-generation, AI-driven co-culture technology to develop a donor-independent synthetic microbiome ecosystem at industrial scale, with MaaT034 – a first-in-class co-cultured product – aiming to optimise intestinal microbiome functions and improve patient responses to immunotherapy in combination with immune checkpoint inhibitors (ICIs).

Metagenomic analysis results presented at AACR showed that MaaT034 reproduces the microbial functions of MaaT013 – the company’s lead asset currently being evaluated in the randomised Phase 2 PICASSO trial in combination with ICIs ipilimumab (Yervoy) and nivolumab (Opdivo) for unresectable or metastatic melanoma. Additionally, MaaT034 was shown to improve DC-mediated T-cell activation and potentiate anti-tumour effects mediated by an anti-PD-1 checkpoint blockade in vitro.

The data also showed that 70% of MaaT034 microbial species engrafted in the germ-free mice, ensuring an enduring presence of beneficial bacteria in the gut environment, as it increases the production of key microbial-derived metabolites, such as short-chain fatty acids, resulting in gut mucosal restoration.

MaaT034 was overall shown to have optimised anti-PD1 mediated activity in tumour-bearing, germ-free mice. While anti-PD1 alone reduced tumour growth by 10%, the combination of anti-PD1 and MaaT034 resulted in a 83.7% tumour growth reduction (compared to a 24.2% reduction when using a single strain of Akkermansia muciniphila bacteria).

Dr Gianfranco Pittari, PhD, chief medical officer at MaaT Pharma, commented: “[This] positive data in tumour-bearing mice demonstrate[s] the significant potential of MaaT034 as a microbiome ecosystem therapy candidate and provide[s] a robust basis for the progression of this therapy into clinical development for solid tumours.”

MaaT034 is currently in preclinical development and was developed using the company’s co-culturing proprietary MET-C platform. Previously presented preclinical data showed that MaaT034 produced key metabolites, recognised as promoting gut barrier restoration and modulating immune responses, such as short-chain fatty acids (SCFAs), secondary bile acids, and tryptophan derivatives.

MaaT Pharma is focused on developing innovative gut microbiome-driven therapies to modulate the immune system and enhance cancer patient survival. The company has been listed on Euronext Paris (ticker: MAAT) since 2021.

The microbiome is ever more frequently spoken about. To find out more, catch up on a previous pharmaphorum podcast with Leo Grady, founder and CEO of Jona, discussing at-home personal microbiome profiling and uncovering the relationship between human health and the gut.