3,4-Dihydropyrimidin-2(1H)‑ones as Antagonists of the Human A2B Adenosine Receptor: Optimization, Structure–Activity Relationship Studies, and Enantiospecific Recognition

We present and thoroughly characterize a large collection of 3,4-dihydropyrimidin-2­(1H)-ones as A2BAR antagonists, an emerging strategy in cancer (immuno) therapy. Most compounds selectively bind A2BAR, with a number of potent and selective antagonists further confirmed by functional cyclic adenosine monophosphate experiments. The series was analyzed with one of the most exhaustive free energy perturbation studies on a GPCR, obtaining an accurate model of the structure–activity relationship of this chemotype. The stereospecific binding modeled for this scaffold was confirmed by resolving the two most potent ligands [(±)-47, and (±)-38 Ki = 10.20 and 23.6 nM, respectively] into their two enantiomers, isolating the affinity on the corresponding (S)-eutomers (Ki = 6.30 and 11.10 nM, respectively). The assessment of the effect in representative cytochromes (CYP3A4 and CYP2D6) demonstrated insignificant inhibitory activity, while in vitro experiments in three prostate cancer cells demonstrated that this pair of compounds exhibits a pronounced antimetastatic effect.

本研究报道并系统表征了一系列作为A2BAR拮抗剂（A2BAR antagonists）的3,4-二氢嘧啶-2(1H)-酮（3,4-dihydropyrimidin-2(1H)-ones）类化合物，该类拮抗剂是癌症（免疫）治疗领域的新兴研究策略。多数化合物可选择性结合A2BAR，其中多个强效且高选择性的拮抗剂经功能性环磷酸腺苷（cyclic adenosine monophosphate, cAMP）实验得到进一步验证。本系列化合物借助G蛋白偶联受体（G protein-coupled receptor, GPCR）领域最为详尽的自由能微扰（free energy perturbation, FEP）研究之一进行分析，构建了该化学型化合物精准的构效关系模型。针对该母核骨架构建的立体特异性结合模型，通过拆分两个活性最强的配体[(±)-47与(±)-38，其外消旋体的解离常数（Ki）分别为10.20 nM与23.6 nM]得到各自的两种对映体（enantiomers），最终证实其亲和力主要集中于对应的(S)型活性对映体（(S)-eutomers），二者的解离常数（Ki）分别为6.30 nM与11.10 nM。针对代表性细胞色素酶（CYP3A4与CYP2D6）的活性评估显示，该类化合物无显著抑制活性；而在三株前列腺癌细胞系中开展的体外实验表明，该对化合物展现出显著的抗转移效应。