Rational design of a JAK1-selective siRNA inhibitor for the modulation of autoimmunity in the skin. Rational design of a JAK1-selective siRNA inhibitor for the modulation of autoimmunity in the skin

Inhibition of Janus kinase (JAK) family enzymes has surged as a popular strategy for treating inflammatory and autoimmune skin diseases. In the clinic, current available small molecule JAK inhibitors show distinct efficacy and safety profiles, likely reflecting their variable selectivity for JAK subtypes. Nonselective inhibition of multiple JAK enzymes is associated with increased side effects and has resulted in FDA-mandated black box warnings. Developing therapeutics to enable absolute JAK subtype selectivity is challenging and has not yet been achieved. Here, we harness RNA interference (RNAi) for rationally designing small interfering RNA (siRNA) therapeutics that offer sequence-specific gene silencing of JAK1, thus narrowing the spectrum of action on JAK-dependent cytokine signaling pathways to maintain efficacy and improve safety. We developed a fully chemically modified siRNA that supports efficient silencing of JAK1 expression in human skin explant and functional modulation of JAK1-dependent inflammatory signaling. A single injection of the JAK1 siRNA into mouse skin enables JAK1 silencing for 5 weeks in vivo. In a mouse model of vitiligo, local administration of the JAK1 siRNA significantly reduces skin infiltration of autoreactive CD8+ T cells and prevents epidermal depigmentation. This work outlines a robust framework for designing targeted RNAi-based therapies and establishes a path toward novel siRNA treatments for inflammatory and autoimmune skin diseases. Overall design: PolyA RNA sequencing from human skin biopsies treated with PBS, non-targeting siRNA, or JAK1-targeting siRNA with and without stimulation with 10 ng/mL of recombinant IFN-γ and 10 ng/mL of TNF-α

Janus激酶（Janus kinase, JAK）家族酶的抑制已成为治疗炎症性与自身免疫性皮肤病的热门策略。临床中，当前可用的小分子JAK抑制剂展现出迥异的疗效与安全性特征，这大概率与其对JAK亚型的选择性差异相关。对多种JAK酶的非选择性抑制会增加不良反应风险，还引发了美国食品药品监督管理局（FDA）强制要求的黑框警告。开发具备绝对JAK亚型选择性的治疗药物极具挑战，目前尚未实现。
本研究借助RNA干扰（RNA interference, RNAi）技术，理性设计可对JAK1实现序列特异性基因沉默的小干扰RNA（small interfering RNA, siRNA）治疗药物，从而精准限定JAK依赖的细胞因子信号通路的作用范围，在维持疗效的同时提升安全性。我们开发了一种完全化学修饰的siRNA，其可在人体皮肤外植体中高效沉默JAK1的表达，并功能性调控JAK1依赖的炎症信号通路。向小鼠皮肤单次注射该JAK1 siRNA，可在体内实现长达5周的JAK1基因沉默。在白癜风小鼠模型中，局部施用JAK1 siRNA可显著减少自身反应性CD8+ T细胞的皮肤浸润，并阻止表皮色素脱失。
本研究构建了一套稳健的靶向RNAi治疗药物开发框架，为炎症性与自身免疫性皮肤病的新型siRNA治疗方案开辟了可行路径。
整体实验设计：对经磷酸盐缓冲液（PBS）、非靶向siRNA或JAK1靶向siRNA处理的人体皮肤活检样本进行PolyA RNA测序，其中部分样本额外施加10 ng/mL重组干扰素-γ（IFN-γ）与10 ng/mL肿瘤坏死因子-α（TNF-α）刺激，设置刺激与未刺激两组对照。