Design, synthesis and anti-necroptosis evaluation of RIPK1 inhibitors derived from sunitinib

Inhibiting receptor-interacting serine/threonine-protein kinase 1 (RIPK1) to block necroptosis is a validated therapeutic strategy for inflammatory and neurodegenerative diseases. Herein, we identified the antitumor drug sunitinib as a hit compound with RIPK1 inhibitory activity (IC₅₀ = 450 nM). Guided by the structural features of the RIPK1 active pocket, sunitinib was systematically modified to design a series of novel derivatives. Screening via in vitro kinase assays and a mouse L929 fibroblast necroptosis model yielded compound 5e (encoded KWJY-5e), a highly potent RIPK1 inhibitor with an IC₅₀ of 92 nM (5-fold more active than sunitinib). In L929 cells induced to undergo necroptosis with mouse tumor necrosis factor-α (mTNF-α)/Z-VAD-FMK, 5e exhibited robust anti-necroptotic activity (EC₅₀ = 450 nM). Mechanistically, 5e pretreatment reduced the phosphorylation of RIPK1, RIPK3, and mixed lineage kinase domain-like pseudokinase (MLKL), suppressed necrosome formation, and preserved mitochondrial/lysosomal function and cell membrane integrity. In vivo, 5e alleviated hypothermia and multi-organ injury in a mouse model of mTNF-α-induced systemic inflammatory response syndrome (SIRS). Although 5e retains some multi-kinase inhibitory activity, its improved RIPK1 potency and in vivo efficacy support further optimization.