Structure-based discovery of receptor tyrosine kinase AXL degraders with excellent anti-tumor activity by selectively degrading AXL and inducing methuosis

The receptor tyrosine kinase (RTK) anexelekto (AXL) is mutated and/or overexpressed in various malignancies, and plays a central role in tumor development and acquired drug resistance. Although highly selective inhibitors have been developed in recent years, direct inhibition of AXL may block its ubiquitination, eventually leading to surface accumulation of the protein. Herein, we designed and synthesized a series of AXL degraders with high selectivity and without compensatory increase of AXL. In particular, compounds 20 and 22 showed significant AXL degradation capacity, which inhibited the proliferation and migration of cancer cells in vitro. In addition, these compounds induced the formation of cytoplasmic vacuoles and triggered methuosis, a new type of non-apoptotic cell death, by stimulating excessive production of macropinosomes. Vacuole formation was mediated via H-Ras activation, and was attenuated upon inhibition of its downstream regulatory factor Rac1. Furthermore, compound 20 inhibited the growth of tumor cell xenografts in vivo, and prolonged the survival of the tumor-bearing mice.