DataSheet1_Nonclinical evaluations of deucravacitinib and Janus kinase inhibitors in homeostatic and inflammatory pathways.docx

Translational medicine provides insight into novel drugs and predicts unwanted effects. In well-characterized pathways (e.g., cytokine-Janus kinase [JAK]-signal transducers and activators of transcription [STAT]), a variety of in vitro assessments were used to estimate selectivity of effects on different potential targets (i.e., JAK1, JAK2, JAK3, and tyrosine kinase 2 [TYK2]). Several approved drugs were characterized as selective for the JAK family. These assessments are challenged by a lack of compounds that only inhibit one JAK family member. Deucravacitinib is a first-in-class, oral, selective, allosteric inhibitor of TYK2, a kinase required for IL-12, IL-23, and Type I interferon signaling. Unlike deucravacitinib, which selectively binds to the TYK2 regulatory domain, JAK1,2,3 inhibitors target the catalytic domain, contributing to nonselective targeting of JAK1,2,3. Cytokines associated with JAK1,2,3 signaling are required for both immune and nonimmune functions. A similar laboratory abnormality profile was observed in clinical trials using JAK1,2,3 inhibitors that has not been observed with deucravacitinib. In vitro testing of JAK1,2,3 inhibitors has relied upon assays of signal transduction, such as those measuring STAT phosphorylation, for estimates of potency and selectivity. These assay systems can be effective in estimating in vivo efficacy; however, they may not provide insight into downstream outcomes of receptor signaling, which may be more relevant for evaluating safety aspects. Assay systems assessing functional outcomes from cells may yield a more useful translational evaluation. Here, deucravacitinib was assessed for potency and selectivity versus three representatives of the JAK inhibitor class (tofacitinib, baricitinib, and upadacitinib) based on functional assays. JAK inhibitors had suppressive activity against JAK2-dependent hematopoietic colony-forming assays modeling thrombopoiesis, erythropoiesis, and myelopoiesis; however, deucravacitinib did not. Deucravacitinib had limited potency against NK cells, cytotoxic T cells, T-helper cells, and regulatory T cells activated by JAK1/JAK3-dependent common gamma chain cytokines. These data are consistent with the biologic role of JAK1,2,3 and pharmacodynamic changes in clinical laboratory abnormalities. Against TYK2-dependent cytokines, deucravacitinib selectively inhibited Type I interferon stimulation of monocytes and dendritic cells and was a more potent inhibitor than JAK inhibitors. IL-12 and IL-23 functional outputs were similarly potently inhibited by deucravacitinib. Results are consistent with deucravacitinib selectively inhibiting TYK2.

转化医学可为新型药物研发提供科学洞见，并预测药物不良反应。在已得到充分表征的信号通路（如细胞因子-贾纳斯激酶（Janus kinase, JAK）-信号转导与转录激活因子（Signal transducers and activators of transcription, STAT）通路）中，研究人员常采用多种体外评估方法，以预测药物对不同潜在靶点（即JAK1、JAK2、JAK3及酪氨酸激酶2（Tyrosine kinase 2, TYK2））的作用选择性。已有多款获批药物被证实可选择性作用于JAK家族。但此类评估面临的一大挑战是，缺乏仅能单一抑制JAK家族成员的化合物。氘可来昔替尼（Deucravacitinib）是一款首创新药（first-in-class）口服选择性TYK2变构抑制剂（allosteric inhibitor），而TYK2是介导白细胞介素12（IL-12）、白细胞介素23（IL-23）及I型干扰素（Type I interferon）信号转导的关键激酶。与仅结合TYK2调节域（regulatory domain）的氘可来昔替尼不同，JAK1、2、3抑制剂靶向催化域（catalytic domain），这导致其对JAK1、2、3的靶向缺乏选择性。介导JAK1、2、3信号转导的细胞因子，同时参与免疫与非免疫功能的调控。在使用JAK1、2、3抑制剂的临床试验中，观察到了类似的实验室异常特征，但此类特征从未在氘可来昔替尼的临床试验中被报道。此前针对JAK1、2、3抑制剂的体外检测，多依赖于信号转导相关实验，例如通过检测STAT磷酸化水平来评估药物的效价（potency）与选择性（selectivity）。此类检测系统可有效预测体内药效，但无法揭示受体信号转导的下游结局，而后者或与药物安全性评价的相关性更高。基于细胞功能结局的检测系统，或可提供更具转化价值的评估结果。本研究基于功能实验，对比了氘可来昔替尼与三款JAK抑制剂类代表药物（托法替布（tofacitinib）、巴瑞替尼（baricitinib）及乌帕替尼（upadacitinib））的效价与选择性。JAK抑制剂可抑制依赖JAK2的造血集落形成实验（hematopoietic colony-forming assays，该实验模拟血小板生成（thrombopoiesis）、红细胞生成（erythropoiesis）及髓系生成（myelopoiesis）过程）中的活性，但氘可来昔替尼无此作用。氘可来昔替尼对由JAK1/JAK3依赖的共同γ链细胞因子（common gamma chain cytokines）激活的NK细胞（NK cells）、细胞毒性T细胞（cytotoxic T cells）、辅助T细胞（T-helper cells）及调节性T细胞（regulatory T cells），仅表现出微弱的抑制活性。上述数据与JAK1、2、3的生物学功能及临床实验室异常的药效学变化相符。针对依赖TYK2的细胞因子，氘可来昔替尼可选择性抑制I型干扰素对单核细胞（monocytes）及树突状细胞（dendritic cells）的刺激作用，且其抑制活性优于JAK抑制剂。IL-12与IL-23的功能输出，同样可被氘可来昔替尼强效抑制。上述结果均证实，氘可来昔替尼可选择性抑制TYK2。