A potent, small-molecule dual insulin-like growth factor-1 receptor (IGF-1R)/insulin receptor (IR) kinase inhibitor. Inhibits IGF-1R and IR kinases with IC₅₀ values of 35 nM and 75 nM, respectively. Linsitinib selectively blocks the autophosphorylation of both human IGF-1R and IR, inhibits the proliferation of a variety of tumor cell lines in vitro, and displays robust in vivo anti-tumor efficacy in an IGF-1R-driven xenograft model when administered orally.