Engineered antibody fragments for PET imaging of immunotherapeutic targets in gliomas

项目概要/摘要 没有有效的非侵入性诊断成像方法来准确分层和监测 成人和儿童神经胶质瘤的免疫治疗。 PET 成像，利用放射性标记的抗体片段， 微型抗体 (Mb) 或双抗体 (Db) 与放射性金属稳定螯合，是安全有效的有前途的选择 直接定量神经胶质瘤患者的细胞表面标记物，反映动态免疫过程 直接影响免疫治疗效果。然而，用于分子成像的 PET 的发展 指导免疫治疗的标记物正处于起步阶段。该应用程序的长期目标是翻译 基于抗体片段的有效放射性示踪剂，用于术前和术中的非侵入性诊断成像 免疫疗法对免疫疗法患者的临床决策产生有意义的影响。整体 该应用的目的是验证放射性示踪剂成分在监测中的独特情况 患者相关小鼠神经胶质瘤模型中的免疫疗法。拟议研究的理由是，非 使用放射性示踪剂进行侵入性诊断成像，量化重要的免疫靶标、活化的 T 细胞和 免疫抑制细胞可以预防和缩短无效治疗的持续时间。中心假设是 放射性标记的 CD11b、EphA2 和 CD69、基于抗体的 PET 示踪剂可以有效指导免疫治疗 用于恶性胶质瘤。在目标 1 中，将使用 Cu-64 标记的抗-PET 技术对神经胶质瘤模型中的 CD11b 进行定量。 CD11b Mb/Db 用于在 TAMC 之前和期间量化免疫抑制肿瘤相关骨髓细胞 (TAMC) 靶向免疫疗法。在目标 2 中，将采用临床前 PET 来量化 EphA2 表达水平 神经胶质瘤。 EphA2是一个高度相关的临床免疫治疗靶点，将作为“原理证明”抗原，并且 为制定全面的抗原-PET 策略提供基础。 Cu-64-的标准摄取值（SUV） 标记的抗 EphA2 Mb/Db 将用于量化同基因原位模型中神经胶质瘤细胞上的 EphA2 水平 具有一系列 EphA2 水平，并鉴定出对免疫疗法有反应的携带神经胶质瘤的小鼠。在目标 3 中， 神经胶质瘤免疫治疗的反应将通过 CD69 PET 和 Cu-64 标记的抗 CD69 Mb/Db 进行评估 量化 T 细胞激活并预测 T 细胞介导的神经胶质瘤小鼠的存活率 免疫疗法。使用强大的成像探针化学、成人和儿童鼠神经胶质瘤模型，以及 免疫治疗方法，将验证新型人/小鼠交叉反应性 Mb/Db 的转化 容量。如果成功，该提案将从根本上改变神经胶质瘤的分层和监测方式 免疫治疗试验，使用实时分子 PET 成像来确定招募哪些受试者以及何时招募 停止或继续治疗。这项研究的结果将大大提高免疫疗法的反应率 同时减少不必要的治疗相关副作用、无效且昂贵的治疗，在这个时代 精准医疗，增加治疗选择。

PROJECT SUMMARY/ABSTRACT There are no effective non-invasive diagnostic imaging approaches to accurately stratify and monitor immunotherapy in adults and children with glioma. PET imaging, utilizing radiolabeled antibody fragments, minibodies (Mb), or diabodies (Db), stably chelated to radiometals, is a promising option for the safe and effective direct quantification of cell surface markers in glioma patients that reflect dynamic immunological processes that bear directly on immunotherapeutic effectiveness. However, development of PET for molecular imaging of markers to guide immunotherapy is in its nascent stage. The long-term goal of this application is to translate effective antibody fragment-based radiotracers for non-invasive diagnostic imaging before and during immunotherapy to meaningfully impact clinical decision making for patients on immunotherapies. The overall objective of this application is to validate radiotracer compositions for unique situations in monitoring immunotherapies in patient-relevant murine glioma models. The rationale for the proposed research is that non- invasive diagnostic imaging with radiotracers quantifying an important immune target, activated T-cells, and immunosuppressive cells to prevent and shorten the duration of ineffective therapies. The central hypothesis is that radiolabeled CD11b, EphA2, and CD69, antibody-based PET tracers can effectively guide immunotherapies for malignant gliomas. In Aim 1, CD11b will be quantified in glioma models by PET with Cu-64-labeled anti- CD11b Mb/Db to quantify immunosuppressive tumor-associated myeloid cells (TAMC) before and during TAMC- targeted immunotherapies. In Aim 2 preclinical PET will be employed to quantify EphA2 expression levels in gliomas. EphA2, a highly relevant clinical immunotherapy target, will serve as a “proof of principle” antigen, and provide a base to develop comprehensive antigen-PET strategies. Standard uptake values (SUV) of Cu-64- labeled anti-EphA2 Mb/Db will be used to quantify EphA2 levels on glioma cells in syngeneic orthotopic models with a range of EphA2 levels and identify glioma-bearing mice that will respond to immunotherapies. In Aim 3, responses to glioma immunotherapy will be assessed by CD69 PET with Cu-64-labeled anti-CD69 Mb/Db to quantify T-cell activation and predict survival rates of glioma-bearing mice following T-cell-mediated immunotherapies. The use of robust imaging probe chemistry, adult and pediatric murine glioma models, and immunotherapy approaches, will validate novel human/mouse cross-reactive Mb/Db for their translational capacity. If successful, this proposal will radically change the way gliomas are stratified and monitored on immunotherapy trials, using real-time molecular PET imaging to determine which subjects to enroll and when to stop or continue therapy. Outcomes from this research will greatly improve response rates to immunotherapy while reducing unnecessary treatment-related side effects, ineffective and costly treatments, in an era of precision medicine with increased treatment options.