The safety and activity of PD-1 ICB was first tested by Ansell et al. (2015) in a phase 1 study on 23 heavily pretreated cHL patients who received biweekly nivolumab, a PD-1 inhibitor, demonstrating an impressive 87% overall response rate (ORR) and a 17% complete metabolic response rate (CMR) [11,29]. Here, PDCD1 is linked to classic Hodgkin lymphoma.