Background/Objective:Current treatments for eosinophilic and mast cell disorders are often ineffective. One promising target to improve outcomes is sialic acid-binding immunoglobulin-like lectin-8 (Siglec-8). As limitations, there are few Siglec-8 monoclonal antibodies (mAbs) available to date, and Siglec-8-directed treatments have so far primarily focused on unconjugated mAbs, which may be inadequate, especially against mast cells.Methods:Here, we used transgenic mice to raise a diverse panel of fully human mAbs that either recognize the V-set domain, membrane-distal C2-set domain, or membrane-proximal C2-set domain of full-length Siglec-8 as a basis for novel therapeutics.Results:All mAbs were efficiently internalized into Siglec-8-expressing cells, suggesting their potential to deliver cytotoxic payloads. Tool T cell-engaging bispecific antibodies (BiAbs) and chimeric antigen receptor (CAR)-modified natural killer (NK) cells using single-chain variable fragments from Siglec-8 mAbs showed highly potent cytolytic activity against Siglec-8-positive cells even in cases of very low target antigen abundance, whereas they elicited no cytolytic activity against Siglec-8-negative target cells. Siglec-8V-set-directed T cell-engaging BiAbs and Siglec-8V-set-directed CAR-modified NK cells induced substantially greater cytotoxicity against cells expressing an artificial smaller Siglec-8 variant containing only the V-set domain than cells expressing full-length Siglec-8, consistent with the notion that targeting membrane-proximal epitopes enhances effector functions of Siglec-8 antibody-based therapeutics. Indeed, unconjugated Siglec-8C2-setmAbs, Siglec-8C2-set-directed T cell-engaging BiAbs, and Siglec-8C2-set-directed CAR-modified NK cells showed high antigen-specific cytolytic activity against Siglec-8-positive human cell lines and primary patient eosinophils.Conclusions:Together, these data demonstrate Siglec-8-directed immunotherapies can be highly potent, supporting their further development for eosinophilic and mast cell disorders.
背景/目的：目前针对嗜酸性粒细胞和肥大细胞疾病的治疗方法往往效果不佳。唾液酸结合免疫球蛋白样凝集素-8（Siglec-8）是改善疗效的一个潜在靶点。现有局限性在于，目前可用的Siglec-8单克隆抗体（mAbs）数量有限，且针对Siglec-8的治疗主要集中于未偶联单抗，这可能不足以有效应对肥大细胞等目标。 方法：本研究利用转基因小鼠制备了一系列全人源单克隆抗体，这些抗体可识别全长Siglec-8的V-set结构域、膜远端C2-set结构域或膜近端C2-set结构域，为开发新型疗法奠定了基础。 结果：所有单克隆抗体均能有效内化至表达Siglec-8的细胞中，表明其具备递送细胞毒性载荷的潜力。基于Siglec-8单抗单链可变片段构建的工具性T细胞衔接双特异性抗体（BiAbs）和嵌合抗原受体（CAR）修饰的自然杀伤（NK）细胞，即使在靶抗原丰度极低的情况下，仍对Siglec-8阳性细胞展现出高效细胞溶解活性，而对Siglec-8阴性靶细胞则无此作用。针对Siglec-8 V-set结构域的T细胞衔接双抗和CAR修饰NK细胞，对仅含V-set结构域的人工小型Siglec-8变异体表达细胞的杀伤作用，显著强于对全长Siglec-8表达细胞，这与靶向膜近端表位可增强Siglec-8抗体疗法效应功能的观点一致。事实上，未偶联的Siglec-8 C2-set单抗、针对Siglec-8 C2-set的T细胞衔接双抗及CAR修饰NK细胞，均对Siglec-8阳性人源细胞系及原代患者嗜酸性粒细胞表现出高抗原特异性细胞溶解活性。 结论：综上所述，这些数据表明针对Siglec-8的免疫疗法具有高效潜力，支持其进一步开发用于治疗嗜酸性粒细胞和肥大细胞疾病。
Optimizing Siglec-8-Directed Immunotherapy for Eosinophilic and Mast Cell Disorders
肿瘤(癌症)患者之家