PDCD1 and neoplasm: B7-H3 provides an alternative immune checkpoint molecule to therapeutically target alone or in combination with PD-1-targeted therapies.8–10 B7-H3 expression has been demonstrated on antigen-presenting cells (APC), but it is limited or absent in most normal tissue.11 In contrast, high B7-H3 expression is observed on solid tumors, with expression detectable on malignant epithelial cells, the tumor vasculature, and subsets of infiltrating immune cells.