(Other name for: sirolimus) or A drug used to keep the body from rejecting organ and bone marrow transplants. Rapamune blocks certain white blood cells that can reject foreign tissues and organs. It also blocks a protein that is involved in cell division. It is a type of antibiotic, a type of immunosuppressant, and a type of serine/threonine kinase inhibitor. Rapamune was previously called rapamycin. Also called sirolimus.