Discovery, Characterization, and Optimization of a Novel Positive Allosteric Modulator-Antagonist of the D3 Dopamine Receptor

To identify novel D3 dopamine receptor (D3R)-selective antagonist scaffolds, we conducted a high-throughput screen of a small-molecule library using a β-arrestin recruitment assay. The lead hit compound, MLS6357, displayed unprecedented D3R selectivity as well as unusual positive allosteric modulator (PAM)-antagonist activity, which may confer unique therapeutic advantages to this scaffold. Iterative medicinal chemistry was used to synthesize and characterize 137 analogues, with several demonstrating both high D3R selectivity and improved D3R potency in β-arrestin recruitment and G protein activation assays. Two of the more promising analogues with 10-fold or greater improvements in potency, 6a and 10aa, were further characterized and found to recapitulate both the allosteric PAM-antagonism and global D3R selectivity of MLS6357. 6a and 10aa also demonstrated favorable pharmacokinetics in mice suggesting that these compounds may serve as both research tools and therapeutic leads for the treatment of neuropsychiatric disorders, including substance use disorder.为了识别新型多巴胺D3受体（D3 dopamine receptor, D3R）选择性拮抗剂骨架，我们采用β抑制蛋白招募实验（β-arrestin recruitment assay）对小分子库开展了高通量筛选。先导命中化合物MLS6357展现出前所未有的D3R选择性，同时具备罕见的正变构调节剂（positive allosteric modulator, PAM）-拮抗双重活性，这可能为该骨架带来独特的治疗优势。我们通过迭代药物化学手段合成并表征了137个类似物，其中多个化合物在β抑制蛋白招募与G蛋白激活实验中同时表现出高D3R选择性以及增强的D3R活性效力。效力提升10倍及以上的两款更具潜力的类似物6a与10aa，经进一步表征后发现，它们重现了MLS6357的变构PAM-拮抗活性与全局性D3R选择性。在小鼠体内实验中，6a与10aa同样展现出良好的药代动力学特性，表明这些化合物既可作为研究工具，也可作为包括物质使用障碍在内的神经精神疾病治疗的先导候选药物。