CD274 and neoplasm: Altogether, these LDD studies illustrate that (1) IT LDD does not cause systemic toxicities that are observed upon IV administration of PD-1/PD-L1 ICIs, (2) IT administration effectively induces tumor regression and prolongs survival in several subcutaneous tumor models, and (3) the use of hydrogels for LDD greatly enhances the efficacy of IT administered PD-1/PD-L1 ICIs compared to IT free drug infusions.