Macrocyclic-triene antibiotic possessing potent immunosuppressant activity. It forms a complex with FKBP12 that binds to an effector, thus inhibiting IL-2 and other growth promoting lymphokines. The effectors were recently identified as FRAP (FKBP12 rapamycin-associated protein) and RAFT1 (rapamycin and KFBP12target). Rapamycin induces inhibition of p70s6k, p33cdk2 and p34cdc2. Enhances apoptosis.SOURCE/HOST:Isolated from Streptomyces hygroscopicus.