Selitrectinib

Selitrectinib (LOXO-195) is a next-generation TRK kinase inhibitor, with IC₅₀s of 0.6 nM and <2.5 nM for TRKA and TRKC, respectively^[1]. IC50 & Target: 0.6 nM (TRKA), <2.5 nM (TRKC)^[1]. 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)^[1]. 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^[1]