Discovery of novel indazole derivatives as second-generation TRK inhibitors

NTRK gene fusion leads to the activation of downstream signaling pathways, which is a oncogenic driver in various cancers. NTRK fusion-positive cancers can be treated with the first-generation Trk inhibitors, larotrectinib and entrectinib. Unfortunately, the patients eventually face the dilemma of no drugs available as the emergence of certain resistance mutations. The development of efficient and broad-spectrum second-generation Trk inhibitors is still of great significance. Here, we analyzed the binding modes of compounds 6, 10 with TrkA protein, respectively, a series of novel indazole Trk inhibitors were designed and synthesized using molecular hybridization strategy. Among them, the optimal compound B31 showed strong antiproliferative activities against Km-12, Ba/F3-TRKA^G595R, and Ba/F3-TRKA^G667C cell lines with IC₅₀ values of 0.3, 4.7, and 9.9 nM, respectively. And the inhibitory effect against TrkA^G667C (IC₅₀ = 9.9 nM) was better than that of selitrectinib (IC₅₀ = 113.1 nM). Further, compound B31 exhibited moderate kinase selectivity and excellent plasma stability (t_1/2 > 480 min). In vivo pharmacokinetic studies in Sprague-Dawley rats showed that B31 had acceptable pharmacokinetic properties.