The description provides compositions and methods for treating ETBR-related cancer. In certain aspects, the description provides a delivery system for the controlled, systemic release of at least one of ETBR antagonists, caspase-8 inhibitors, or a combination thereof, optionally including an ETAR antagonist, an anti-PD-1 antibody, a bRAF inhibitor, niacinamide or a combination thereof. The compositions described are useful for the treatment of certain cancers, including, e.g., breast cancer, malignant melanoma, squamous cell carcinoma, glioblastoma, as well as others. In addition, the description provides a delivery system for the controlled release of at least one of ETBR antagonists, caspase-8 inhibitors or a combination thereof, optionally including at least one of an ETAR antagonist, an anti-PD-1 antibody, a bRAF inhibitor, niacinamide, or a combination thereof, to the central nervous system that are useful for treating cancers that have spread to the brain.
