text: The bacterial natural product rapamycin or sirolimus, a cytostatic agent, has been used in combination therapy with corticosteroids and cyclosporine in patients who received kidney transplantation to prevent organ rejection both in the US  and Europe, due to its unsatisfying pharmacokinetic properties. In 2003, the U.S. Food and Drug Administration approved sirolimus-eluting coronary stents, which are used in patients with narrowing of coronary arteries, or so-called atherosclerosis.
  Recently rapamycin has shown effective in the inhibition of growth of several human cancers and murine cell lines. Rapamycin is the main mTOR inhibitor, but deforolimus (AP23573), everolimus (RAD001), and temsirolimus (CCI-779), are the newly developed rapamycin analogs.