ATC Group: L01EG Mammalian target of rapamycin (mTOR) kinase inhibitors

Everolimus is a selective mTOR (mammalian target of rapamycin) inhibitor. mTOR is a key serine-threonine kinase, the activity of which is known to be upregulated in a number of human cancers.

Sirolimus inhibits T-cell activation induced by most stimuli, by blocking calcium-dependent and calcium-independent intracellular signal transduction. Studies demonstrated that its effects are mediated by a mechanism that is different from that of ciclosporin, tacrolimus, and other immunosuppressive agents.

Temsirolimus is a selective inhibitor of mTOR (mammalian target of rapamycin). Temsirolimus binds to an intracellular protein (FKBP-12), and the protein/temsirolimus complex binds and inhibits the activity of mTOR that controls cell division. In vitro, at high concentrations (10-20 M), temsirolimus can bind and inhibit mTOR in the absence of FKBP-12. When mTOR activity is inhibited, its ability to phosphorylate, and thereby control the activity of protein translation factors (4E-BP1 and S6K, both downstream of mTOR in the P13 kinase/AKT pathway) that control cell division, is blocked.