ChEBI: Sirolimus is a macrolide lactam isolated from Streptomyces hygroscopicus consisting of a 29-membered ring containing 4 trans double bonds, three of which are conjugated. It is an antibiotic, immunosupressive and antineoplastic agent. It has a role as an immunosuppressive agent, an antineoplastic agent, an antibacterial drug, a mTOR inhibitor, a bacterial metabolite and an anticoronaviral agent. It is a cyclic acetal, a cyclic ketone, an ether, a secondary alcohol, an organic heterotricyclic compound, an antibiotic antifungal drug and a macrolide lactam.NCI Thesaurus (NCIt): Sirolimus is a natural macrocyclic lactone produced by the bacterium Streptomyces hygroscopicus, with immunosuppressant properties. In cells, sirolimus binds to the immunophilin FK Binding Protein-12 (FKBP-12) to generate an immunosuppressive complex that binds to and inhibits the activation of the mammalian Target Of Rapamycin (mTOR), a key regulatory kinase. This results in inhibition of T lymphocyte activation and proliferation that occurs in response to antigenic and cytokine (IL-2, IL-4, and IL-15) stimulation and inhibition of antibody production. (NCI04)