CD274 and neoplasm: This relatively small reagent (molecular weight of ~ 14 kDa reagent) possessed desirable tumor penetration properties, compared to conventional mAbs (molecular weight of ~ 150,000 kDa), and could be used as a PET imaging tracer to distinguish between PD-L1 positive and negative tumors in live mice, and was effective at reducing tumor volume in small and large CT26 syngeneic tumor models in mice in a preclinical murine model of colon cancer.