Selective JAK3 inhibitors have been shown to have a potential benefit in the treatment of autoimmune disorders. Here we report the identification of a series of pyrazolopyrimidine derivatives as potent JAK3 inhibitors that exploit a unique cysteine (Cys909) residue in JAK3. Most of these compounds (13k, 13n and 13 t), displayed stronger anti-JAK3 kinase activity and selectivity than tofacitinib. Furthermore, the most active inhibitor 13t (IC50 = 0.1 nM), also exhibited favourable selectivity for JAK3 in a panel of 9 kinases which contain the same cysteine. In a series of cytokinestimulated cellular analysis, compound 13 t, could potently block the JAK3-STAT signaling pathway. Further biological studies, including cellular antiproliferative activity assays and a rat adjuvant-induced arthritis model for in vivo evaluation, also indicated its efficacy and low toxicity in the treatment of rheumatoid arthritis. The results of these experimental explorations suggested that 13t is a promising lead compound for the development of selective JAK3 inhibitor with therapeutic potential in rheumatoid arthritis.

中文翻译：

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新型1H-吡唑并[3,4-d]嘧啶-6-氨基衍生物，作为有效的选择性Janus激酶3（JAK3）抑制剂。评估其在治疗类风湿关节炎中的改善作用。

选择性JAK3抑制剂已显示在自身免疫性疾病的治疗中具有潜在的益处。在这里，我们报告鉴定一系列有效的JAK3抑制剂吡唑并嘧啶衍生物，这些抑制剂利用JAK3中的独特半胱氨酸（Cys909）残基。这些化合物中的大多数（13k，13n和13 t）显示出比托法替尼更强的抗JAK3激酶活性和选择性。此外，活性最高的抑制剂13t（IC50 = 0.1 nM）在包含相同半胱氨酸的9种激酶中也显示出对JAK3的良好选择性。在一系列细胞动力学估计的细胞分析中，化合物13 t可能有效阻断JAK3-STAT信号传导途径。进一步的生物学研究，包括用于体内评估的细胞抗增殖活性测定和大鼠佐剂诱发的关节炎模型，还表明其在治疗类风湿关节炎中的功效和低毒性。这些实验探索的结果表明，13t是开发具有治疗风湿性关节炎潜力的选择性JAK3抑制剂的有前途的先导化合物。