Persephone Biosciences, a Y Combinator company, takes a novel approach to improving the efficacy of existing therapies, leveraging the systemic impact of the gut microbiome on the human immune system. Persephone's technology platform is based on collecting and analyzing gut microbiota samples from thousands of patients, then using machine learning in conjunction with systems biology tools to understand the impact of gut microbes on patient prognosis. The results are used to design novel immunotherapies and companion diagnostics for unmet needs. Persephone’s mission is to unlock the potential of the gut microbiome to develop equitable precision medicine.