Li J, Deng Y, Zhang W, et al. - Among patients with previously treated advanced defective mismatch repair (dMMR)/microsatellite instability high (MSI-H) tumors, who were recruited from 25 clinical sites across China, this open-label, single-arm, phase 2 study was conducted to test the efficacy as well as safety of envafolimab in this patient population. In a 28-day treatment cycle, weekly 150 mg subcutaneous envafolimab injections were administered to adults with histologically proven locally advanced or metastatic malignant dMMR/MSI-H solid tumors. The objective response rate and disease control rate were 42.7% and 66.0%, respectively. A median progression-free survival of 11.1 months and overall survival at 12 months of 74.6% was reported. In this first pivotal phase 2 study to assess the efficacy as well as safety of a single-domain immune checkpoint antibody in the treatment of cancer, findings showed the effectiveness as well as acceptable safety of envafolimab in the treatment of previously treated advanced dMMR/MSI-H solid tumors. The results also indicate the potential of envafolimab, as the first single-domain programmed death ligand 1-targeting antibody delivered by rapid subcutaneous injection, to represent a significant advance in the treatment of cancer.