PDCD1 and esophageal squamous cell carcinoma: The first TIM-3-PD-1 BsAb, R07121661, was used in a Phase I study to treat advanced and/or metastatic solid tumors, including ESCC, melanoma, SCLC, and NSCLC (NCT03708328), and in a Phase II study, it was used to treat advanced or metastatic ESCC (NCT04785820) [195].