SER-401

SER-401 is an investigational, orally administered microbiome therapeutic developed by Seres Therapeutics. [4] It is a rationally-designed consortium of live bacterial spores sourced from screened healthy donors who have a microbiome signature similar to that observed in cancer immunotherapy responders. [4, 15] The therapeutic was designed to modulate the gut microbiome to improve patients' response to immune checkpoint inhibitor immunotherapy. [4] SER-401 was evaluated in a Phase 1b clinical trial (NCT03817125), known as the MCGRAW study, in combination with nivolumab for the treatment of metastatic melanoma. [1, 4] This study was conducted in collaboration with The Parker Institute for Cancer Immunotherapy and The University of Texas MD Anderson Cancer Center. [4, 6] Seres also had a research collaboration with AstraZeneca to explore the drug's potential. However, this agreement was terminated in April 2021. In March 2021, Seres announced the voluntary discontinuation of enrollment in the MCGRAW study and the deprioritization of the SER-401 program, citing challenges with enrollment during the COVID-19 pandemic. [6]