Sirolimus (Rapamycin), a natural 31-membered macrocyclic
lactone produced by Streptomyces hygroscopicus. Sirolimus
(SRL) is a potent immunosuppressive agent used to prevent
rejection in organ transplantation especially useful in kidney
transplants approved by the Food and Drug Administration.
[1] It can down-regulate cytokine dependent kinase mTOR
(mammalian target of rapamycin), thus inducing cell-cycle
arrest in the late G1 phase. [2-3] It is well known that sirolimus
is only effective when bound to sirolimus binding protein
(FKBP), present on smooth muscle cells. [4] SRL inhibits the
proliferation of both rat and human smooth muscle cells in
vitro and reduces intimal thickening in models of vascular
injury. [5-6] It is the most preferred drug for inhibiting restenosis
in cardiac stenting and used as drug eluting stent