Design, synthesis and biological evaluation of 1H-indazole derivatives as novel ASK1 inhibitors.

Apoptosis signal-regulating kinase 1 (ASK1, MAP3K5), a member of the mitogen-activated protein kinase (MAPK) signaling pathway, is involved in cell survival, differentiation, stress response, and apoptosis. ASK1 kinase inhibition has emerged as a promising therapeutic strategy for inflammatory disease. A series of novel ASK1 inhibitors with 1H-indazole scaffold were designed, synthesized and evaluated for their ASK1 kinase activity and AP1-HEK293 cell inhibitory effect. Systematic structure-activity relationship (SAR) efforts led to the discovery of promising compound 15, which showed excellent in vitro ASK1 kinase activity and potent inhibitory effects on ASK1 in AP1-HEK293 cells. In a tumor necrosis factor-α (TNF-α)-induced HT-29 intestinal epithelial cell model, compound 15 exhibited a significantly protective effect on cell viability comparable to that of GS-4997; moreover, compound 15 exhibited no obvious cytotoxicity against HT-29 cells at concentrations up to 25 µM. Mechanistic research demonstrated that compound 15 suppresses phosphorylation in the ASK1-p38/JNK signaling pathway in HT-29 cells, and regulates the expression levels of apoptosis-related proteins. Altogether, these results show that compound 15 may serve as a potential candidate compound for the treatment of inflammatory bowel disease (IBD).

Structure-based discovery of 1H-indole-2-carboxamide derivatives as potent ASK1 inhibitors for potential treatment of ulcerative colitis.

Apoptosis signal-regulating kinase 1 (ASK1), a member of the mitogen-activated protein kinase (MAPK) family, is implicated in many human diseases. Here, we describe the structural optimization of hit compound 7 and conduct further structure-activity relationship (SAR) studies that result in the development of compound 19 with a novel indole-2-carboxamide hinge scaffold. Compound 19 displays potent anti-ASK1 kinase activity and stronger inhibitory effect on ASK1 in AP1-HEK293 cells than previously described ASK1 inhibitor GS-4997. Besides improved in vitro activity, compound 19 also exhibits an appropriate in vivo PK profile. In a dextran sulfate sodium (DSS)-induced mouse model of ulcerative colitis (UC), compound 19 shows significant anti-UC efficacy and markedly attenuates DSS-induced body weight loss, colonic shortening, elevation in disease activity index (DAI) and inflammatory cell infiltration in colon tissues. Mechanistically, compound 19 represses the phosphorylation of ASK1-p38/JNK signaling pathways and suppresses the overexpression of inflammatory cytokines. Together, these findings suggest that ASK1 inhibitors can potentially be used as a therapeutic strategy for UC.

Synthesis and Evaluation of O2-Derived Diazeniumdiolates Activatable via Bioorthogonal Chemistry Reactions in Living Cells.

A class of O2-alkyl derived diazeniumdiolates 3a-f and 4a-c were designed and synthesized as new bioorthogonal NO precursors, which can be effectively uncaged in the presence of a palladium catalyst via bioorthogonal bond cleavage reactions to generate NO in living cancer cells, eliciting potent antiproliferative activity.