PDCD1 and cancer: There are early phase 1 studies designed to improve response among patients with anti-PD-1 resistant/refractory digestive cancers based on gut microbiota interventions in which investigators extracted the gut microbiota of healthy participants whose gut was similar to that of those with anti-PD-1 responsive digestive cancers to product FMT capsules and re-challenge anti-PD-1 immunotherapy in combination with FMT in cancer patients who had failed anti-PD-1 therapy (126).