We herein report the structural optimization and structure–activity relationship studies of 5-(2,3-dihydro-1H-indol-5-yl)-7H-pyrrolo­[2,3-d]­pyrimidin-4-amine derivatives as a new class of receptor-interacting protein kinase 1 (RIPK1) inhibitors. Among all obtained RIPK1 inhibitors, 1-(5-{4-amino-7-ethyl-7H-pyrrolo­[2,3-d]­pyrimidin-5-yl}-2,3-dihydro-1H-indol-1-yl)-2-[3-(trifluoromethoxy)­phenyl]­ethan-1-one (22b) is the most active one. This compound potently inhibited RIPK1 with a binding affinity (K D) of 0.004 μM and an enzymatic IC50 value of 0.011 μM and also showed good kinase selectivity. It could efficiently protect cells from necroptosis and attenuate the necrotic cell death of vascular endothelial cells induced by tumor cells both in vitro and in vivo. Importantly, compound 22b exhibited excellent antimetastasis activity in the experimental B16 melanoma lung metastasis model. It also displayed favorable pharmacokinetic properties. Collectively, 22b could be a promising agent for preventing tumor metastasis.

A TEMPO-mediated [3 + 2] annulation–aromatization protocol for the preparation of pyrazolo­[1,5-a]­pyridines from N-aminopyridines and α,β-unsaturated compounds was developed. The procedure offered multisubstituted pyrazolo­[1,5-a]­pyridines in good to excellent yield with high and predictable regioselectivity. The modification of marketed drugs including Loratadine, Abiraterone, and Metochalcone, and a one-pot three-step gram scale synthesis of key intermediate for the preparation of Selpercatinib were demonstrated. Mechanism studies show that TEMPO serves both as a Lewis acid and as an oxidant.

Diabetic retinopathy (DR) is a major cause of blindness, and there is a lack of effective treatment at present. Rho-associated coiled-coil containing serine/threonine protein kinases (ROCKs) have recently been suggested as potential targets for the DR treatment. We herein report the discovery of 4H-chromen-4-one derivatives as a new class of ROCK inhibitors. Structure–activity relationship analyses led to the identification of the most active compound, 4-(dimethylamino)-N-(3-{2-[(4-oxo-4H-chromen-7-yl)­oxy]­acetamido}­phenyl) (12j). This compound showed excellent kinase selectivity for ROCK I and ROCK II against 387 other kinases. In retinal explants, compound 12j protected retinal neurons from high glucose-induced oxidative stress and apoptosis-mediated cell death. Furthermore, 12j administration suppressed the improper proliferation of Müller cells and promoted the regression of vascular vessels in retinal explants cultured in a high glucose microenvironment. Collectively, our data suggest that 12j could be a potential lead compound for the treatment of DR, hence deserving further in-depth studies.

The Traf2- and Nck-interacting protein kinase (TNIK) is a downstream signal protein of the Wnt/β-catenin pathway and has been thought of as a potential target for the treatment of colorectal cancer (CRC) that is often associated with dysregulation of Wnt/β-catenin signaling pathway. Herein, we report the discovery of a series of 3,4-dihydrobenzo­[f]­[1,4]­oxazepin-5­(2H)-one derivatives as a new class of TNIK inhibitors. Structure–activity relationship (SAR) analyses led to the identification of a number of potent TNIK inhibitors with compound 21k being the most active one (IC50: 0.026 ± 0.008 μM). This compound also displayed excellent selectivity for TNIK against 406 other kinases. Compound 21k could efficiently suppress CRC cell proliferation and migration in in vitro assays and exhibited considerable antitumor activity in the HCT116 xenograft mouse model. It also showed favorable pharmacokinetic properties. Overall, 21k could be a promising lead compound for drug discovery targeting TNIK and deserves further studies.