Dewulf Jonatan, Flieswasser Tal, Delahaye Tim, Vangestel Christel, Miranda Alan, de Haard Hans, Jacobs Julie, Smits Evelien, Van den Wyngaert Tim, Elvas Filipe
Molecular Imaging Center Antwerp (MICA), Integrated Personalized and Precision Oncology Network (IPPON), Faculty of Medicine and Health Sciences, University of Antwerp, Universiteitsplein 1, 2610, Wilrijk, Belgium.
Center for Oncological Research (CORE), Faculty of Medicine and Health Sciences, IPPON, University of Antwerp, Universiteitsplein 1, 2610, Wilrijk, Belgium.
EJNMMI Radiopharm Chem. 2023 Apr 24;8(1):8. doi: 10.1186/s41181-023-00194-3.
CD70-CD27 is a costimulatory ligand-receptor pair in the tumor necrosis factor receptor family. With only limited expression in normal tissues, CD70 is constitutively expressed in a variety of solid tumors and hematologic malignancies, facilitating immunosuppression through CD27 signaling in the tumor microenvironment by enhanced survival of regulatory T cells, induction of T cell apoptosis, and T cell exhaustion. Consequently, CD70 is an increasingly recognized target for developing antibody-based therapies, but its expression patterns vary among different tumor types in spatial distribution, magnitude of expression and percentage of positive cells. In that regard, individual confirmation of CD70 expression at screening and during treatment could enhance the successful implementation of anti-CD70 therapies. Here, we developed a gallium-68 (Ga) radiolabeled single-domain antibody-fragment targeting CD70 for in vivo positron emission tomography (PET) imaging.
An anti-CD70 VHH construct containing a C-direct-tag with a free thiol was developed to enable site-specific conjugation to a NOTA bifunctional chelator for Ga radiolabeling. [Ga]Ga-NOTA-anti-CD70 VHH was obtained in good radiochemical yield of 30.4 ± 1.7% and high radiochemical purity (> 94%). The radiolabeled VHH showed excellent in vitro and in vivo stability. Specific binding of [Ga]Ga-NOTA-anti-CD70 VHH was observed on CD70 786-O cells, showing significantly higher cell-associated activity when compared to the blocking condition (p < 0.0001) and CD70 NCl-H1975 cells (p < 0.0001). PET imaging showed specific radiotracer accumulation in CD70 expressing human tumor xenografts, which was efficiently blocked by prior injection of unlabeled anti-CD70 VHH (p = 0.0029). In addition, radiotracer uptake in CD70 tumors was significantly higher when compared with CD70 tumors (p < 0.0001). The distribution of the radioactivity in the tumors using autoradiography was spatially matched with immunohistochemistry analysis of CD70 expression.
[Ga]Ga-NOTA-anti-CD70 VHH showed excellent in vivo targeting of CD70 in human cancer xenografts. PET imaging using this radioimmunoconjugate holds promise as a non-invasive method to identify and longitudinally follow-up patients who will benefit most from anti-CD70 therapies.
CD70 - CD27是肿瘤坏死因子受体家族中的一对共刺激配体 - 受体。CD70在正常组织中仅有限表达，在多种实体瘤和血液系统恶性肿瘤中组成性表达，通过增强调节性T细胞的存活、诱导T细胞凋亡和T细胞耗竭，在肿瘤微环境中通过CD27信号传导促进免疫抑制。因此，CD70越来越被认为是开发基于抗体疗法的靶点，但其表达模式在不同肿瘤类型之间在空间分布、表达强度和阳性细胞百分比方面存在差异。在这方面，在筛查和治疗期间对CD70表达进行个体确认可以提高抗CD70疗法的成功实施。在此，我们开发了一种靶向CD70的镓 - 68（Ga）放射性标记单域抗体片段，用于体内正电子发射断层扫描（PET）成像。
开发了一种含有游离巯基的C - 直接标签的抗CD70 VHH构建体，以实现与用于Ga放射性标记的NOTA双功能螯合剂的位点特异性缀合。[Ga]Ga - NOTA - 抗CD70 VHH以30.4±1.7%的良好放射化学产率和高放射化学纯度（>94%）获得。放射性标记的VHH在体外和体内均表现出优异的稳定性。在CD70 786 - O细胞上观察到[Ga]Ga - NOTA - 抗CD70 VHH的特异性结合，与阻断条件（p < 0.0001）和CD70 NCl - H1975细胞（p < 0.0001）相比，显示出显著更高的细胞相关活性。PET成像显示在表达CD70的人肿瘤异种移植中特异性放射性示踪剂积聚，预先注射未标记的抗CD70 VHH可有效阻断这种积聚（p = 0.0029）。此外，与CD70阴性肿瘤相比，CD70阳性肿瘤中的放射性示踪剂摄取显著更高（p < 0.0001）。使用放射自显影法在肿瘤中的放射性分布与CD70表达的免疫组织化学分析在空间上相匹配。
[Ga]Ga - NOTA - 抗CD70 VHH在人癌异种移植中显示出对CD70优异的体内靶向性。使用这种放射免疫缀合物的PET成像有望作为一种非侵入性方法，用于识别和纵向随访将从抗CD70疗法中获益最大的患者。
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