PDCD1 and head and neck squamous cell carcinoma: In December 2020, an open-label, phase I/II tumor immunotherapy trial was initiated using RM‐1929-mediated NIR-PIT in combination with anti-programmed cell death protein 1 (PD1) immune checkpoint inhibitors in patients with recurrent or metastatic HNSCC, or advanced or metastatic CSCC (NCT04305795).