Ridaforolimus, also known as AP23573, MK-8669 Deforolimus, is an investigational targeted and small-molecule inhibitor of the protein mTOR, a protein that acts as a central regulator of protein synthesis, cell proliferation, cell cycle progression and cell survival, integrating signals from proteins, such as PI3K, AKT and PTEN known to be important to malignancy. Blocking mTOR creates a starvation-like effect in cancer cells by interfering with cell growth, division, metabolism, and angiogenesis. It has had promising results in a clinical trial for advanced soft tissue and bone sarcoma.