CD274 and neoplasm: A protein-dose escalation biodistribution experiment showed that the co-injection of 30 μg of an unlabeled antibody provided—via the saturation of PD-L1-positive receptors occurring in the spleen—the best results, with the highest tumor uptake at 48 h p.i., a tumor-to-muscle ratio of 21.71 ± 1.28, and a tumor-to-blood ratio of 2.51 ± 0.11.