Illustration of immunosupressant drug rapamycin (red), also known as siromlimus. It is an inhibitor of protein complex mTORC1 (mammalian target of rapamycin complex 1, blue). Rapamycin is mainly used to prevent rejection in organ transplantation, and is used in kidney transplants. It also has anti-fungal and anti-cancer properties, and was originally derived from soil bacteria found on Easter Island.