Lim Sheryl Y T, Huo Jenny, Laszlo George S, Cole Frances M, Kehret Allie R, Li Junyang, Lunn-Halbert Margaret C, Persicke Jasmyn L, Rupert Peter B, Strong Roland K, Walter Roland B
Translational Science and Therapeutics Division, Fred Hutchinson Cancer Center, Seattle, WA 98109, USA.
Basic Sciences Division, Fred Hutchinson Cancer Center, Seattle, WA 98109, USA.
Cancers (Basel). 2024 Oct 14;16(20):3476. doi: 10.3390/cancers16203476.
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. 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. 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-8-directed T cell-engaging BiAbs and Siglec-8-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-8 mAbs, Siglec-8-directed T cell-engaging BiAbs, and Siglec-8-directed CAR-modified NK cells showed high antigen-specific cytolytic activity against Siglec-8-positive human cell lines and primary patient eosinophils. Together, these data demonstrate Siglec-8-directed immunotherapies can be highly potent, supporting their further development for eosinophilic and mast cell disorders.
目前针对嗜酸性粒细胞和肥大细胞疾病的治疗方法往往无效。一个有望改善治疗效果的靶点是唾液酸结合免疫球蛋白样凝集素8（Siglec-8）。然而，目前存在一些限制，至今可用的Siglec-8单克隆抗体（mAb）很少，并且迄今为止针对Siglec-8的治疗主要集中在未偶联的mAb上，这可能并不充分，尤其是对肥大细胞。在此，我们利用转基因小鼠制备了一系列多样的全人源mAb，这些mAb可识别全长Siglec-8的V结构域、膜远端C2结构域或膜近端C2结构域，以此作为新型治疗药物的基础。所有mAb均能有效内化至表达Siglec-8的细胞中，表明它们具有递送细胞毒性载荷的潜力。使用来自Siglec-8 mAb的单链可变片段构建的工具性T细胞接合双特异性抗体（BiAb）和嵌合抗原受体（CAR）修饰的自然杀伤（NK）细胞，即使在靶抗原丰度非常低的情况下，对Siglec-8阳性细胞也表现出高效的细胞溶解活性，而对Siglec-8阴性靶细胞则无细胞溶解活性。针对Siglec-8的T细胞接合BiAb和针对Siglec-8的CAR修饰NK细胞，对表达仅含V结构域的人工小Siglec-8变体的细胞诱导的细胞毒性，比对表达全长Siglec-8的细胞诱导的细胞毒性大得多，这与靶向膜近端表位可增强基于Siglec-8抗体的治疗药物的效应功能这一观点一致。实际上，未偶联的Siglec-8 mAb、针对Siglec-8的T细胞接合BiAb和针对Siglec-8的CAR修饰NK细胞，对Siglec-8阳性人细胞系和原发性患者嗜酸性粒细胞均表现出高抗原特异性细胞溶解活性。总之，这些数据表明针对Siglec-8的免疫疗法可能具有高效性，支持其针对嗜酸性粒细胞和肥大细胞疾病的进一步开发。
