LOXO-195

LOXO-195 (Selitrectinib;LOXO 195, LOXO195) is a potent, selective, next-generation Trk tyrosine kinase inhibitor with IC50 of 0.6 nM and <2.5 nM for WT TrkA and WT TrKC, respectively; also diplays high potentcy against mutant TrkA G595R, TrkA G667C, TrkC G623R and TrkC G696A with IC50 of 2.0, 9.8, 2.3 and <2.5 nM, respectively; overcomes acquired resistance mediated by recurrent kinase domain (solvent front and xDFG) mutations identified in multiple patients.Lung Cancer Phase 1 Clinical(In Vitro):Selitrectinib (LOXO-195) demonstrates strong binding to the wild-type TRKA, TRKB and TRKC kinase domains. Selitrectinib (LOXO-195) has potent (IC50<1 nM) inhibitory activity in kinase enzyme assays. Importantly, Selitrectinib (LOXO-195) achieves low nanomolar inhibitory activity against TRKA G595R, TRKC G623R, and TRKA G667C, with IC50s ranging from 2.0-9.8 nM. 228 individual kinases in vitro are profiled at a Selitrectinib (LOXO-195) concentration of 1 μM, which is ~1667-fold higher than its IC50 for TRKA (0.6 nM). Selitrectinib (LOXO-195) is more than 1000-fold selective for 98% of non-TRK kinases tested. Selitrectinib (LOXO-195) demonstrates potent inhibition of cell proliferation in TRK fusion-containing KM12, CUTO-3, and MO-91 cell lines (IC50≤5 nM).\n(In Vivo):Stably transfected NIH-3T3 ΔTRKA and ΔTRKA-G595R cells are implanted subcutaneously into the flanks of nude mice. Both larotrectinib and Selitrectinib (LOXO-195) are effective at reducing phosphorylated TRKA in tumors driven by ΔTRKA. In contrast, only Selitrectinib (LOXO-195) strongly suppresses phospho-TRKA in ΔTRKA-G595R cells in a dose-dependent manner. Selitrectinib (LOXO-195) also causes inhibition of tumor growth relative to vehicle at all doses in four TRKA-dependent tumor models (ΔTRKA, ΔTRKA-G595R, ΔTRKAG667C, and TPM3-NTRK1 fusion-positive KM12 colorectal cancer cells. Larotrectinib inhibits KM12 and NIH 3T3-ΔTRKA tumors to a similar degree. Group mean body weight loss does not exceed 5% for any agent. Selitrectinib (LOXO-195) displays high selectivity for the TRK proteins.