Abstract：
Janus Kinase 3 (JAK3) is important for the signaling transduction of cytokines in immune cells and is identified as potential target for treatment of rheumatoid arthritis (RA). Recently, we designed and synthesized two JAK3 inhibitors J1b and J1f, which featured with high selectivity but mild bioactivity. Therefore, in present study the structure was optimized to increase the potency. As shown in the results, most of the compounds synthesized showed stronger inhibitory activities against JAK3 in contrast to the lead compounds, among which 9a was the most promising candidate because it had the most potent effect in ameliorating carrageenan-induced inflammation of mice and exhibited low acute in vivo toxicity (MTD > 2 g/kg). Further analysis revealed that 9a was highly selective to JAK3 (IC50 = 0.29 nM) with only minimal effect on other JAK members (>3300-fold) and those kinases bearing a thiol in a position analogous to that of Cys909 in JAK3 (>150-fold). Meanwhile, the selectivity of JAK3 was also confirmed by PBMC stimulation assay, in which 9a irreversibly bound to JAK3 and robustly inhibited the signaling transduction with mild suppression on other JAKs. Moreover, it was showed that 9a could remarkably inhibited the proliferation of lymphocytes in response to concanavalin A and significantly mitigate disease severity in collagen induced arthritis. Therefore, present data indicate that compound 9a is a selective JAK3 inhibitor and could be a promising candidate for clinical treatment of RA.
摘要：
Janus激酶3（JAK3）对于免疫细胞中细胞因子的信号转导很重要，并且被确定为治疗类风湿性关节炎（RA）的潜在靶标。最近,我们设计并合成了两种JAK3抑制剂J1b和J1f，具有高选择性，但生物活性温和。因此,在本研究中，对结构进行了优化以提高效力。如结果所示，与先导化合物相比，合成的大多数化合物对JAK3表现出更强的抑制活性，其中9a是最有希望的候选药物，因为它在改善角叉菜胶诱导的小鼠炎症方面具有最有效的作用，并且表现出低的急性体内毒性（MTD>2g/kg）。进一步的分析显示,9a对JAK3具有高度选择性(IC50=0.29nM),对其他JAK成员(>3300倍)和在与JAK3中的Cys909的位置类似的位置上带有硫醇的那些激酶(>150倍)仅有最小的影响。同时,PBMC刺激试验也证实了JAK3的选择性，其中9a不可逆地与JAK3结合，并强烈抑制信号转导，对其他JAK具有轻度抑制。此外，研究表明，9a可以显着抑制伴刀豆球蛋白A反应的淋巴细胞增殖，并显着减轻胶原诱导性关节炎的疾病严重程度。因此,目前的数据表明,化合物9a是一种选择性的JAK3抑制剂,可能是临床治疗RA的有希望的候选药物.
