PDCD1 and cancer: However, in a single arm phase II trial, designed based on the observation that HPV16+ OPSCC patients lacking tumor infiltration with HPV16-specific T cells are most likely the ones that are diagnosed with incurable HPV16+ cancer (6, 24) and that PD-1 checkpoint therapy has most impact in patients with pre-existing tumor-specific T cell responses (155), HPV16+ OPSCC patients received a combined treatment with ISA101 and nivolumab (146).