A small molecule and non-prodrug analogue of the lipophilic macrolide antibiotic rapamycin with potential antitumor activity. Ridaforolimus binds to and inhibits the mammalian target of rapamycin (mTOR), which may result in cell cycle arrest and,consequently, the inhibition of tumor cell growth and proliferation. Upregulated in some tumors, mTOR is a serine/threonine kinase involved in regulating cellular proliferation, motility, and survival that is located downstream of the PI3K/Akt signaling pathway. or A substance being studied in the treatment of soft tissue and bone cancers. It is also being studied in the treatment of other solid tumors and hematologic cancer. Ridaforolimus stops cells from dividing and may cause cancer cells to die. It is a type of mTOR inhibitor. Also called AP23573.