Discovery of Potent and Orally Effective Dual Janus Kinase 2/FLT3 Inhibitors for the Treatment of Acute Myelogenous Leukemia and Myeloproliferative Neoplasms

Herein,
we describe the design, synthesis, and structure–activity
relationships of a series of unique 4-(1H-pyrazol-4-yl)-pyrimidin-2-amine
derivatives that selectively inhibit Janus kinase 2 (JAK2) and FLT3
kinases. These screening cascades revealed that 18e was
a preferred compound, with IC50 values of 0.7 and 4 nM
for JAK2 and FLT3, respectively. Moreover, 18e was a
potent JAK2 inhibitor with 37-fold and 56-fold selectivity over JAK1
and JAK3, respectively, and possessed an excellent selectivity profile
over the other 100 representative kinases. In a series of cytokine-stimulated
cell-based assays, 18e exhibited a higher JAK2 selectivity
over other JAK isoforms. The oral administration of 60 mg/kg of 18e could significantly inhibit tumor growth, with a tumor
growth inhibition rate of 93 and 85% in MV4-11 and SET-2 xenograft
models, respectively. Additionally, 18e showed an excellent
bioavailability (F = 58%), a suitable half-life time
(T1/2 = 4.1 h), a satisfactory metabolic
stability, and a weak CYP3A4 inhibitory activity, suggesting that 18e might be a potential drug candidate for JAK2-driven myeloproliferative
neoplasms and FLT3-internal tandem duplication-driven acute myelogenous
leukemia.

本文详述了一系列独特的4-(1H-吡唑-4-基)-嘧啶-2-胺类衍生物的设计、合成及构效关系，该类衍生物可选择性抑制贾努斯激酶2（JAK2）与FLT3激酶。通过一系列筛选级联实验发现，化合物18e为优选候选物，其对JAK2和FLT3的半最大抑制浓度（IC50）分别为0.7 nM和4 nM。此外，18e是一种强效JAK2抑制剂，对JAK1和JAK3的选择性分别达37倍和56倍，且对其余100种代表性激酶均表现出优异的选择性谱。在一系列细胞因子刺激的细胞实验中，18e相较于其他JAK同工型，展现出更显著的JAK2选择性。以60 mg/kg的剂量口服给予18e，可显著抑制肿瘤生长，在MV4-11和SET-2异种移植瘤模型中的肿瘤生长抑制率分别为93%和85%。此外，18e具备优异的生物利用度（F=58%）、适宜的半衰期（T1/2=4.1 h）、良好的代谢稳定性，且对细胞色素P450 3A4（CYP3A4）的抑制活性较弱，表明18e有望成为针对JAK2驱动的骨髓增殖性肿瘤以及FLT3内部串联重复突变驱动的急性髓系白血病的潜在候选药物。