Discovery of 4-amino-1,6-dihydro-7H-pyrrolo[2,3-d]pyridazin-7-one derivatives as potential receptor-interacting serine/threonine-protein kinase 1 (RIPK1) inhibitors.

Receptor-interacting serine/threonine-protein kinase 1 (RIPK1) is an important regulatory factor in the necroptosis signaling pathway, and is considered an attractive therapeutic target for treating multiple inflammatory diseases. Herein, we describe the design, synthesis, and structure–activity relationships of 4-amino-1,6-dihydro-7 H -pyrrolo [2,3- d ]pyridazin-7-one derivatives as RIPK1 inhibitors. Among them, 13c showed favorable RIPK1 kinase inhibition activity with an IC 50 value of 59.8 nM, and high RIPK1 binding affinity compared with other regulatory kinases of necroptosis (RIPK1 K d = 3.5 nM, RIPK3 K d = 1700 nM, and MLKL K d > 30,000 nM). 13c efficiently blocked TNFα-induced necroptosis in both human and murine cells (EC 50 = 1.06–4.58 nM), and inhibited TSZ-induced phosphorylation of the RIPK1/RIPK3/MLKL pathway. In liver microsomal assay studies, the clearance rate and half-life of 13c were 18.40 mL/min/g and 75.33 min, respectively. 13c displayed acceptable pharmacokinetic characteristics, with oral bioavailability of 59.55%. In TNFα-induced systemic inflammatory response syndrome, pretreatment with 13c could effectively protect mice from loss of body temperature and death. Overall, these compounds are promising candidates for future optimization studies. [Display omitted] • Pyrrolo [2,3- d ] pyridazinone derivatives were synthesized as RIPK1 inhibitors. • 13c showed high RIPK1 binding affinity and anti-necrosis cell activity. • 13c could effectively protect mice from hypothermia and death in the SIRS model. [ABSTRACT FROM AUTHOR]