PDCD1 and ovarian cancer: For instance, a Phase II clinical trial of Nivolumab, an FDA-approved anti-PD-1 antibody, in patients with platinum-resistant ovarian cancer displayed an overall response rate of only ~15% [18], suggesting that several challenges still exist in expanding the use of ICIs as effective intervention and exploration on potential therapeutics combination that can cooperate with the ICIs to advance the clinical response in ovarian cancer is urgently required.