Everolimus and sirolimus in transplantation-related but different.
BACKGROUND
The inhibitors of the mammalian target of rapamycin (mTOR) sirolimus and everolimus are used not only as immunosuppressants after organ transplantation in combination with calcineurin inhibitors (CNIs) but also as proliferation signal inhibitors coated on drug-eluting stents and in cancer therapy. Notwithstanding their related chemical structures, both have distinct pharmacokinetic, pharmacodynamic and toxicodynamic properties.


METHODS
The additional hydroxyethyl group at the C(40) of the everolimus molecule results in different tissue and subcellular distribution, different affinities to active drug transporters and drug-metabolizing enzymes as well as differences in drug-target protein interactions including a much higher potency in terms of interacting with the mTOR complex 2 than sirolimus. Said mechanistic differences as well as differences found in clinical trials in transplant patients are reviewed.


CONCLUSIONS
In comparison to sirolimus, everolimus has higher bioavailability, a shorter terminal half-life, different blood metabolite patterns, the potential to antagonize the negative effects of CNIs on neuronal and kidney cell metabolism (which sirolimus enhances), the ability to stimulate mitochondrial oxidation (which sirolimus inhibits) and to reduce vascular inflammation to a greater extent. A head-to-head, randomized trial comparing the safety and tolerability of these two mTOR inhibitors in solid organ transplant recipients is merited.
University of Colorado, iC42 Clinical Research and Development , Anschutz Medical Campus, 1999 North Fitzsimons Parkway, Suite 100, Aurora, CO 80045-7503 , USA +1 303 724 5665 ; +1 303 724 5662 ; uwe.christians@ucdenver.edu.
Jost
J
Klawitter
Björn
B
Nashan
Uwe
U
Christians
D001682:Biological Availability; D000068338:Everolimus / Q000378:metabolism / Q000493:pharmacokinetics; D006084:Graft Rejection / Q000378:metabolism / Q000517:prevention & control; D006801:Humans; D007166:Immunosuppressive Agents / Q000378:metabolism / Q000493:pharmacokinetics; D007668:Kidney / Q000378:metabolism*; D000076225:Mechanistic Target of Rapamycin Complex 2; D008928:Mitochondria / Q000187:drug effects*; D046912:Multiprotein Complexes / Q000037:antagonists & inhibitors / Q000378:metabolism; D009474:Neurons / Q000378:metabolism*; D020123:Sirolimus / Q000378:metabolism / Q000493:pharmacokinetics; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism
D007166:Immunosuppressive Agents; D046912:Multiprotein Complexes; D000068338:Everolimus; D000076225:Mechanistic Target of Rapamycin Complex 2; D058570:TOR Serine-Threonine Kinases; D020123:Sirolimus
comparison; drug metabolism; everolimus; mammalian target of rapamycin complex 2; mitochondria; nephrotoxicity; neuronal metabolism; pharmacokinetics; sirolimus; vascular inflammation