Momelotinib (LM-1149) is an orally bioavailable small-molecule inhibitor of Janus kinases 1 and 2 (JAK1/2) with IC50 of 11 nM/18 nM. JAK1/2 inhibitor CYT387 competes with JAK1/2 for ATP binding, which may result in inhibition of JAK1/2 activation, inhibition of the JAK-STAT signaling pathway, and so the induction of apoptosis and a reduction of tumor cell proliferation in JAK1/2-expressing tumor cells.

JAK1:11 nM, JAK2:18 nM

作用于鼠MPN 模型时,CYT387可使血球密度,白细胞数和脾脏大小正常化,并恢复炎性细胞因子生理水平.

在体外,CYT387对IL-3刺激的亲本Ba/F3细胞增殖有抑制作用（IC50：1400 nM）。此外,CYT387对体外JAK2V617F阳性PV患者红系集落生长的抑制效果与之相似（IC50：2-4 μM）。CYT387抑制IGF-1和IL-6诱导的Ras/MAPK和PI3K/AKT信号。且在原发性多发骨髓瘤细胞中,CYT387 单独使用,或与MM治疗药硼替佐米和美法仑联用可诱发细胞凋亡。CYT387对JAK1和JAK2（IC50：11 nM和18 nM）的选择性比JAK3激酶(IC50为155 nM)高9倍。CYT387还可作用于组成型激活的 JAK2 或 MPL信号 的细胞系,包括 Ba/F3-MPLW515L细胞（IC50：200 nM）,CHRF-288-11细胞（IC50：1 nM）和Ba/F3-TEL-JAK2细胞（IC50：700 nM）,还抑制细胞增殖。

Cell-free kinase activity assays: Glutathione-S-transferase (GST)-tagged JAK kinase domains expressed in insect cells are purified before use in a peptide substrate phosphorylation assay. Assays are carried out in 384-well optiplates using an Alphascreen Protein Tyrosine Kinase P100 detection kit and a PerkinElmer Fusion Alpha instrument.

Ba/F3 cells expressing JAK2V617F (Ba/F3-JAK2V617F) and MPLW515L (Ba/F3-MPLW515L) mutants, as well as CHRF-288-11 (JAK2T875N) and CMK (JAK3A572V) cells are used. The TEL/JAK2 and TEL/JAK3 fusions are generated and introduced into Ba/F3 murine cells. The TEL/JAK2- or TEL/JAK3-transfected cells are cultured in Dulbecco's modified Eagle's medium (DMEM) containing 10% fetal calf serum (FCS). Ba/F3 wild-type cells are cultured in RPMI containing 10% FCS supplemented with 5 ng/mL murine IL-3. Proliferation is measured using the Alamar Blue assay after incubating for 72 hours at 37 °C with 5% CO2