The novel PTPN2 inhibitors ABBV-CLS-579 (NCT04417465) and ABBV-CLS-484 (NCT04777994) are currently under investigation in combination with anti-PD1 therapy in phase 1 clinical trials for locally advanced and metastatic solid tumors, including HNSCC. Here, PDCD1 is linked to head and neck squamous cell carcinoma.