LOXO-101 is an inhibitor of the tropomyosin-related kinases TrkA, TrkB, and TrkC (IC50s = 2-20 nM). It is selective for TrkA, -B, and -C over a panel of 226 kinases at 1 μM. LOXO-101 inhibits the growth of CUTO-3.29, KM12, and MO-91 patient-derived cancer cell lines (IC50s = <100, <10, and <10 nM, respectively). In vivo, LOXO-101 (60 and 200 mg/kg) reduces tumor growth in a KM12 mouse xenograft model.