A Case Report of Envafolimab in the Treatment of Microsatellite Stable (MSS) Metastatic Colon Cancer.

Envafolimab is a novel inhibitor for programmed cell death protein-ligand 1 (PD-L1) that can be administered subcutaneously. It has been found to be effective and safe in the treatment of advanced high microsatellite unstable (MSI-H) / mismatch repair deficient (dMMR) solid tumors. Currently, the efficacy of programmed cell death protein-1 (PD-1) / programmed cell death protein-ligand 1 (PD-L1) inhibitors in the treatment of microsatellite stable (MSS) tumors is not clear. We report a case of advanced colon cancer with MSS metastases in bilateral clavicle, mediastinum, retroperitoneum, bilateral hilum, and left side of thoracic 11/12 vertebral body. After 8 months of Envafolimab treatment, there was a significant reduction in metastatic lesions. As of February 1st, 2024, the patient exhibited no significant adverse reactions. The current efficacy evaluation was the partial response (PR), and the overall survival (OS) was more than 12 months. Considering the safety and efficacy of Envafolimab observed in our case, we believe that Envafolimab may be a promising drug for the treatment of MSS metastatic colon cancer.