Abstract：
LAG3 is an inhibitory immune checkpoint expressed on activated T and NK cells. Blocking the interaction of LAG3 with its ligands MHC-II and FGL1 renders T cells improved cytotoxicity to cancer cells. Current study generated a panel of LAG3 monoclonal antibodies (mAbs) through immunization of mice followed by phage display. Some of them bound to the D1-D2 domain of LAG3, which is known for the engagement of its ligands FGL1 and MHC-II. Three outperformers, M208, M226, and M234, showed stronger blocking activity than Relatlimab in the FGL1 binding. Furthermore, M234 showed dual inhibition of FGL1 (IC50 of 20.6 nM) and MHC-II binding (IC50 of 6.2 nM) to LAG3. In vitro functional tests showed that M234 significantly stimulated IFN-γ secretion from activated PBMC cells. In vivo studies in a mouse model of hepatocellular carcinoma xenografts demonstrated that combining M234 IgG with GPC3-targeted bispecific antibodies significantly improved efficacy. In addition, GPC3-targeted CAR-T cells secreting IL-21-M234 scFv fusion protein exhibited enhanced activity in inhibiting tumor growth and greatly increased the survival rate of mice. Taken together, M234 has potential in cancer immunotherapy and warrants further clinical trial.
摘要：
LAG3是在活化的T和NK细胞上表达的抑制性免疫检查点。阻断LAG3与其配体MHC-II和FGL1的相互作用使得T细胞对癌细胞的细胞毒性提高。目前的研究通过免疫小鼠然后进行噬菌体展示产生了一组LAG3单克隆抗体(mAb)。它们中的一些与LAG3的D1-D2结构域结合，该结构域以其配体FGL1和MHC-II的接合而闻名。三个表现出色的人，M208、M226和M234在FGL1结合中显示出比Relatlimab更强的阻断活性。此外，M234显示对LAG3的FGL1(20.6nM的IC50)和MHC-II结合(6.2nM的IC50)的双重抑制。体外功能测试显示M234显著刺激活化PBMC细胞分泌IFN-γ。在肝细胞癌异种移植物的小鼠模型中的体内研究表明,将M234IgG与GPC3靶向的双特异性抗体组合显著提高了功效。此外,GPC3靶向的分泌IL-21-M234scFv融合蛋白的CAR-T细胞在抑制肿瘤生长方面表现出增强的活性，并大大提高了小鼠的存活率。一起来看,M234在癌症免疫疗法中具有潜力，值得进一步的临床试验。
