Background

Inhibitors of the Janus kinase-signal transducers and activators of transcription (JAK-STAT) pathway have demonstrated efficacy in the treatment of rheumatoid arthritis (RA) and inflammatory bowel disease (IBD). Differences in selectivity of JAK inhibitors for JAK1, JAK2, JAK3 and TYK2 may influence their respective safety profiles, and the mechanisms responsible are not currently known. Filgotinib (FIL), a JAK1 inhibitor, did not negatively impact haemoglobin, LDL:HDL ratios or natural killer (NK) cell counts in clinical trials. Here, we compare the in vitro mechanistic profiles of four JAK inhibitors at clinically relevant doses.

Methods

JAK inhibitors (FIL, FIL metabolite [GS-829845], baricitinib [BARI], tofacitinib [TOFA], and upadacitinib [UPA]) were evaluated in vitro in human-cell-based assays. Growth of erythroid progenitors from human cord blood CD34⁺ cells was assessed using a HemaTox™ liquid expansion assay, NK cell proliferation was induced by IL-15 and LXR agonist-induced cholesteryl ester transfer protein (CETP) expression was assessed in the hepatic cell line, HepG2. Using assay-generated IC50 values and the reported human plasma concentrations from clinical studies, we calculated the target coverage for each JAK inhibitor at clinically relevant doses. The activity of FIL in humans was based on PK/PD modelling of FIL + GS-829845.

Results

Inhibition of cellular activity was calculated for each JAK inhibitor based on in vitro dose-response data, human exposure data and modelled PK/PD relationships. At clinically relevant doses, FIL resulted in lower calculated inhibition of NK cell proliferation compared with other JAK inhibitors. FIL 100 mg and 200 mg also reduced CETP expression, whereas other JAK inhibitors had no effect. There was no difference in the effect of FIL vs. other JAK inhibitors on erythroid progenitor cell differentiation or maturation.

Conclusion

FIL, a JAK1 inhibitor, resulted in less inhibition of NK cell proliferation compared with BARI, TOFA, and UPA. FIL also reduced LXR agonist-induced CETP expression, while the other inhibitors did not alter these levels. These results provide a potential mechanistic link between the observed reduction of CETP concentration following FIL treatment and the previously observed reduction in the LDL:HDL ratio in RA patients.

中文翻译：

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P460评估类风湿关节炎临床研究中非洛替尼安全性观察的潜在机制

背景

Janus激酶信号转导子和转录激活子（JAK-STAT）通路的抑制剂已证明在类风湿性关节炎（RA）和炎症性肠病（IBD）的治疗中有效。JAK抑制剂对JAK1，JAK2，JAK3和TYK2的选择性差异可能会影响其各自的安全性，目前尚不清楚其作用机理。在临床试验中，JAK1抑制剂非戈替尼（FIL）对血红蛋白，LDL：HDL比率或自然杀伤（NK）细胞计数没有负面影响。在这里，我们在临床相关剂量下比较了四种JAK抑制剂的体外机理。

方法

在基于人细胞的测定中，体外评估了JAK抑制剂（FIL，FIL代谢物[GS-829845]，baricitinib [BARI]，tofacitinib [TOFA]和upadacitinib [UPA]）。使用HemaTox™液体扩增测定法评估人脐带血CD34 ⁺细胞中红系祖细胞的生长，通过IL-15诱导NK细胞增殖，并评估肝细胞系中LXR激动剂诱导的胆固醇酯转移蛋白（CETP）表达，HepG2。使用测定法产生的IC50值和临床研究报告的人血浆浓度，我们计算了临床相关剂量下每种JAK抑制剂的目标覆盖率。FIL在人类中的活性基于FIL + GS-829845的PK / PD模型。

结果

根据体外剂量反应数据，人体暴露数据和建模的PK / PD关系，计算每种JAK抑制剂的细胞活性抑制率。与其他JAK抑制剂相比，在临床相关剂量下，FIL对NK细胞增殖的抑制作用较低。FIL 100 mg和200 mg也可降低CETP表达，而其他JAK抑制剂则无作用。FIL与其他JAK抑制剂对类红细胞祖细胞分化或成熟的作用没有差异。

结论

与BARI，TOFA和UPA相比，JIL1抑制剂FIL对NK细胞增殖的抑制作用较小。FIL还降低了LXR激动剂诱导的CETP表达，而其他抑制剂未改变这些水平。这些结果提供了在FIL治疗后观察到的CETP浓度降低与RA患者先前观察到的LDL：HDL比降低之间的潜在机械联系。