背景:淋巴细胞活化基因3(LAG-3)被认为是下一代免疫检查点和免疫疗法的有希望的预后生物标志物。与程序性细胞死亡蛋白1/程序性死亡配体1和细胞毒性T淋巴细胞抗原4抑制剂一样,正电子发射断层扫描(PET)成像策略有助于制定LAG-3相关治疗的临床决策.在这项研究中,我们开发并验证了68Ga标记的环肽示踪剂,用于LAG-3表达的PET成像。
方法:用68GaCl3修饰和放射性标记一系列LAG-3靶向环肽,并评估其亲和力和特异性,生物分布,药代动力学,和体外和体内辐射剂量学。此外,构建hu-PBL-SCID(PBL)小鼠模型以验证[68Ga]Ga-CC09-1用于使用纵向PET成像绘制LAG-3+淋巴细胞浸润物的能力。最后,[68Ga]Ga-CC09-1被转化为首次人体研究以评估其安全性,LAG-3表达的生物分布和成像潜力。
结果:使用一系列靶向LAG-3的环肽作为先导化合物来设计和开发68Ga标记的PET示踪剂。体外结合测定显示[68Ga]Ga-CC09-1在中国仓鼠卵巢-人LAG-3细胞和外周血单核细胞中具有更高的亲和力和特异性。体内PET成像显示[68Ga]Ga-CC09-1具有更好的成像能力,在注射后60分钟时,肿瘤摄取更高,为每克1.35±0.33%的注射剂量,肿瘤与肌肉的比率为17.18±3.20。此外,[68Ga]Ga-CC09-1可以检测脾脏中的LAG-3+淋巴细胞浸润,PBL小鼠的肺和唾液腺。在黑色素瘤和非小细胞肺癌患者中,在[68Ga]Ga-CC09-1PET中观察到具有适度肿瘤摄取的原发性病变,与[18F]FDGPET相比。更重要的是,[68Ga]Ga-CC09-1描绘了大肿瘤内LAG-3表达的异质性。
结论:这些发现巩固了[68Ga]Ga-CC09-1是定量肿瘤微环境中LAG-3表达的有前途的PET示踪剂,表明其在抗LAG-3治疗中作为患者分层和治疗反应监测的伴随诊断的潜力。
BACKGROUND: Lymphocyte activation gene 3 (LAG-3) has been considered as the next generation of immune checkpoint and a promising prognostic biomarker of immunotherapy. As with programmed cell death protein-1/programmed death-ligand 1 and cytotoxic T-lymphocyte antigen-4 inhibitors, positron emission tomography (PET) imaging strategies could benefit the development of clinical decision-making of LAG-3-related therapy. In this study, we developed and validated 68Ga-labeled cyclic peptides tracers for PET imaging of LAG-3 expression in bench-to-bedside studies.
METHODS: A series of LAG-3-targeted cyclic peptides were modified and radiolabeled with 68GaCl3 and evaluated their affinity and specificity, biodistribution, pharmacokinetics, and radiation dosimetry in vitro and in vivo. Furthermore, hu-PBL-SCID (PBL) mice models were constructed to validate the capacity of [68Ga]Ga-CC09-1 for mapping of LAG-3+ lymphocytes infiltrates using longitudinal PET imaging. Lastly, [68Ga]Ga-CC09-1 was translated into the first-in-human studies to assess its safety, biodistribution and potential for imaging of LAG-3 expression.
RESULTS: A series of cyclic peptides targeting LAG-3 were employed as lead compounds to design and develop 68Ga-labeled PET tracers. In vitro binding assays showed higher affinity and specificity of [68Ga]Ga-CC09-1 in Chinese hamster ovary-human LAG-3 cells and peripheral blood mononuclear cells. In vivo PET imaging demonstrated better imaging capacity of [68Ga]Ga-CC09-1 with a higher tumor uptake of 1.35±0.33 per cent injected dose per gram and tumor-to-muscle ratio of 17.18±3.20 at 60 min post-injection. Furthermore, [68Ga]Ga-CC09-1 could detect the LAG-3+ lymphocyte infiltrates in spleen, lung and salivary gland of PBL mice. In patients with melanoma and non-small cell lung cancer, primary lesions with modest tumor uptake were observed in [68Ga]Ga-CC09-1 PET, as compared with that of [18F]FDG PET. More importantly, [68Ga]Ga-CC09-1 delineated the heterogeneity of LAG-3 expression within large tumors.
CONCLUSIONS: These findings consolidated that [68Ga]Ga-CC09-1 is a promising PET tracer for quantifying the LAG-3 expression in tumor microenvironment, indicating its potential as a companion diagnostic for patients stratification and therapeutic response monitoring in anti-LAG-3 therapy.