Design, synthesis, and Structure-Activity Relationships (SAR) of 3-vinylindazole derivatives as new selective tropomyosin receptor kinases (Trk) inhibitors.

Neurotrophic receptor tyrosine kinase (NTRK) fusions are oncogenic drivers for a variety of adult and pediatric tumors, validated by the US FDA approval of small molecular Trk inhibitors Larotrectinib (1, LOXO-101) and Entrectinib (2). However, gene mutation mediated resistance becomes a major challenge for Trk inhibitor therapies. Herein, we report the design, synthesis and Structure-Activity Relationship investigation of a series of 3-vinylindazole derivatives as new Trk inhibitors with low nanomolar potencies. A representative compound, 7mb, binds to TrkA/B/C with K values of 1.6, 3.1 and 4.9 nM, and suppresses their kinase functions with IC values of 1.6, 2.9 and 2.0 nM, respectively, but is obviously less potent for the majority of a panel of 403 wild-type kinases in a KINOMEscan selectivity investigation. The compound also potently suppresses proliferation of a panel of BaF3 cells stably transformed with NTRK fusions with IC values in low nM ranges. Additionally, the compound exhibits strong inhibition against the Larotrectinib-resistant cells with NTRK1-G667C or NTRK3-G696A mutations with IC values of 0.031 and 0.018 μM, respectively. Although the relatively poor oral bioavailability of 7mb will limit its further development, this compound may be utilized a lead molecule for further structural optimization.