高凝集素-3（Gal-3）是一种高度表达在侵袭性癌症肿瘤微环境中的β-半乳糖苷结合凝集素，并且据说能预测免疫检查点治疗（使用抗PD-1单克隆抗体Pembrolizumab）的不良反应。我们的目标是评估Gal-3的效应是否是与免疫检查点受体直接相互作用的结果。通过体外生物化学和细胞实验以及体内同种移植模型，评估了在有无阻断抗体的情况下，Gal-3与PD-1/PD-L1复合物的相互作用能力。Gal-3通过增强PD-1/PD-L1复合物的相互作用，降低了免疫检查点抑制剂Pembrolizumab（抗PD-1）和Atezolizumab（抗PD-L1）的结合。在高选择性的Gal-3小分子抑制剂（GB1211）存在的情况下，抗PD-1/抗PD-L1治疗物的结合恢复到对照水平。这一观察结果是通过表面等离子共振测定蛋白质-蛋白质相互作用和流式细胞术进行的。GB1211与抗PD-L1阻断抗体的联合治疗减少了体内同种移植模型的肿瘤生长，并增加了肿瘤浸润T淋巴细胞的百分比。我们的研究表明，Gal-3可能增强PD-1/PD-L1免疫轴，并有可能在肿瘤微环境内参与免疫抑制信号机制。此外，Gal-3阻止Atezolizumab和Pembrolizumab与其相应的免疫检查点受体的结合。临床候选药GB1211逆转了这种效应，为抗PD-1和PD-L1的阻断抗体提供了增强联合治疗的潜在选择。版权所有 © 2023 Mabbitt, Holyer, Roper, Nilsson, Zetterberg, Vuong, Mackinnon, Pedersen and Slack.

Galectin-3 (Gal-3) is a β-galactoside-binding lectin that is highly expressed within the tumor microenvironment of aggressive cancers and has been suggested to predict a poor response to immune checkpoint therapy with the anti-PD-1 monoclonal antibody pembrolizumab. We aimed to assess if the effect of Gal-3 was a result of direct interaction with the immune checkpoint receptor.The ability of Gal-3 to interact with the PD-1/PD-L1 complex in the absence and presence of blocking antibodies was assessed in in vitro biochemical and cellular assays as well as in an in vivo syngeneic mouse cancer model.Gal-3 reduced the binding of the checkpoint inhibitors pembrolizumab (anti-PD-1) and atezolizumab (anti-PD-L1), by potentiating the interaction between the PD-1/PD-L1 complex. In the presence of a highly selective Gal-3 small molecule inhibitor (GB1211) the binding of the anti-PD-1/anti-PD-L1 therapeutics was restored to control levels. This was observed in both a surface plasmon resonance assay measuring protein-protein interactions and via flow cytometry. Combination therapy with GB1211 and an anti-PD-L1 blocking antibody reduced tumor growth in an in vivo syngeneic model and increased the percentage of tumor infiltrating T lymphocytes.Our study suggests that Gal-3 can potentiate the PD-1/PD-L1 immune axis and potentially contribute to the immunosuppressive signalling mechanisms within the tumor microenvironment. In addition, Gal-3 prevents atezolizumab and pembrolizumab target engagement with their respective immune checkpoint receptors. Reversal of this effect with the clinical candidate GB1211 offers a potential enhancing combination therapeutic with anti-PD-1 and -PD-L1 blocking antibodies.Copyright © 2023 Mabbitt, Holyer, Roper, Nilsson, Zetterberg, Vuong, Mackinnon, Pedersen and Slack.