Benzisothiazolinone Derivatives as Potent Allosteric Monoacylglycerol Lipase Inhibitors That Functionally Mimic Sulfenylation of Regulatory Cysteines.

We describe a set of benzisothiazolinone (BTZ) derivatives that are potent inhibitors of monoacylglycerol lipase (MGL), the primary degrading enzyme for the endocannabinoid 2-arachidonoyl-sn-glycerol (2-AG). Structure-activity relationship studies evaluated various substitutions on the nitrogen atom and the benzene ring of the BTZ nucleus. Optimized derivatives with nanomolar potency allowed us to investigate the mechanism of MGL inhibition. Site-directed mutagenesis and mass spectrometry experiments showed that BTZs interact in a covalent reversible manner with regulatory cysteines, Cys201 and Cys208, causing a reversible sulfenylation known to modulate MGL activity. Metadynamics simulations revealed that BTZ adducts favor a closed conformation of MGL that occludes substrate recruitment. The BTZ derivative 13 protected neuronal cells from oxidative stimuli and increased 2-AG levels in the mouse brain. The results identify Cys201 and Cys208 as key regulators of MGL function and point to the BTZ scaffold as a useful starting point for the discovery of allosteric MGL inhibitors.

Novel irreversible epidermal growth factor receptor inhibitors by chemical modulation of the cysteine-trap portion.

Irreversible EGFR inhibitors can circumvent acquired resistance to first-generation reversible, ATP-competitive inhibitors in the treatment of non-small-cell lung cancer. They contain both a driver group, which assures target recognition, and a warhead, generally an acrylamide or propargylamide fragment that binds covalently to Cys797 within the kinase domain of EGFR. We performed a systematic exploration of the role for the warhead group, introducing different cysteine-trapping fragments at position 6 of a traditional 4-anilinoquinazoline scaffold. We found that different reactive groups, including epoxyamides (compounds 3-6) and phenoxyacetamides (compounds 7-9), were able to irreversibly inhibit EGFR. In particular, at significant lower concentrations than gefitinib (1), (2R,3R)-N-(4-(3-bromoanilino)quinazolin-6-yl)-3-(piperidin-1-ylmethyl)oxirane-2-carboxamide (6) inhibited EGFR autophosphorylation and downstream signaling pathways, suppressed proliferation, and induced apoptosis in gefitinib-resistant NSCLC H1975 cells, harboring the T790M mutation in EGFR.