Seres Therapeutics Presents New Preclinical Data Supporting the Development of SER-401 for Immuno-Oncology at the 2019 American Association for Cancer Research Annual Meeting

Seres Therapeutics, Inc. (Nasdaq: MCRB) today announced that new preclinical data supporting the development of microbiome therapeutics for immuno-oncology (poster title “Leveraging gut microbiota networks to impact tumor immunotherapy”)¹ will be presented by Sceneay et al. at the 2019 American Association for Cancer Research Annual Meeting (AACR) in Atlanta, Georgia. The data presented provide new insights on the potential mechanism by which Seres’ microbiome therapies, including the Company’s SER-401 program, could improve outcomes of cancer patients treated with immune checkpoint inhibitors.

“The novel data presented at AACR provide mechanistic insights into the biological activity of our microbiome therapeutic candidates to augment immune checkpoint inhibitors,” said Matthew Henn, Ph.D., Chief Scientific Officer and Executive Vice President at Seres. “The valuable learnings obtained from this work have informed the development of SER-401, which is being evaluated in combination with an FDA approved immunotherapy in the ongoing MCGRAW Phase 1b study in patients with metastatic melanoma.”

Seres presented preclinical results evaluating the impact of various consortia of bacterial species on the anti-tumor immune response in murine models following treatment with an anti-PD-1 checkpoint inhibitor. Results demonstrated that germ-free or antibiotic-treated mice lacking a functional gastrointestinal microbiome failed to mount an effective anti-tumor response when administered anti-PD-1 checkpoint inhibitor treatment. The response to anti-PD-1 treatment was restored by the introduction of a specific consortia of commensal bacteria rationally designed using insights from both in vivo and human microbiome signatures of response and the functional properties of specific bacterial strains in Seres’ strain library of gastrointestinal bacteria.

These data provide support for the continued development of SER-401, an oral microbiome therapeutic candidate sourced from screened healthy individuals who have been identified to have a microbiome bacterial signature similar to that observed in responders to cancer immunotherapy. The therapeutic aim of SER-401 is to modify the microbiome of cancer patients to increase the efficacy of immunotherapy. SER-401 is being evaluated in a Phase 1b clinical study (NCT03817125) conducted in collaboration with The University of Texas MD Anderson Cancer Center and the Parker Institute for Cancer Immunotherapy in patients with metastatic melanoma. In addition, Seres has an ongoing collaboration with AstraZeneca to advance the mechanistic understanding of the microbiome in augmenting the efficacy of cancer immunotherapy, including in combination with agents in AstraZeneca’s oncology pipeline.