The Discovery of in Vivo Active Mitochondrial Branched-Chain Aminotransferase (BCATm) Inhibitors by Hybridizing Fragment and HTS Hits

The hybridization of hits, identified by complementary fragment and high throughput screens, enabled the discovery of the first series of potent inhibitors of mitochondrial branched-chain aminotransferase (BCATm) based on a 2-benzylamino-pyrazolo­[1,5-a]­pyrimidinone-3-carbonitrile template. Structure-guided growth enabled rapid optimization of potency with maintenance of ligand efficiency, while the focus on physicochemical properties delivered compounds with excellent pharmacokinetic exposure that enabled a proof of concept experiment in mice. Oral administration of 2-((4-chloro-2,6-difluorobenzyl)­amino)-7-oxo-5-propyl-4,7-dihydropyrazolo­[1,5-a]­pyrimidine-3-carbonitrile 61 significantly raised the circulating levels of the branched-chain amino acids leucine, isoleucine, and valine in this acute study.通过互补片段筛选与高通量筛选鉴定得到的命中化合物的杂合设计，促成了首个基于2-苄基氨基-吡唑并[1,5-a]嘧啶酮-3-腈母核的强效线粒体支链氨基酸转氨酶（BCATm）抑制剂系列的发现。采用结构导向的配体生长策略，可在保留配体效率的前提下快速优化化合物的活性；同时通过对理化性质的精准调控，使化合物获得了优异的药代动力学暴露特性，进而得以在小鼠体内开展概念验证实验。在本急性研究中，口服给予2-((4-氯-2,6-二氟苄基)氨基)-7-氧代-5-丙基-4,7-二氢吡唑并[1,5-a]嘧啶-3-腈（化合物61），可显著升高循环系统中支链氨基酸亮氨酸、异亮氨酸与缬氨酸的水平。