Gerstner Sloan Kettering Graduate School of Biomedical Sciences, Memorial Sloan Kettering Cancer Center, NY, USA; Department of Radiology, Memorial Sloan Kettering Cancer Center, NY, USA.
Department of Radiology, Memorial Sloan Kettering Cancer Center, NY, USA.
Nucl Med Biol. 2020 Jul-Aug;86-87:9-19. doi: 10.1016/j.nucmedbio.2020.04.006. Epub 2020 May 1.
Despite its limitations, CA125 remains the most widely used biomarker for the diagnosis and treatment monitoring of ovarian cancer. Targeting the unshed portion of serum biomarkers such as CA125/MUC16 may afford more specific imaging and targeting of MUC16-positive tumors in High Grade Serous Ovarian Cancer (HGSOC) patients.
Six monoclonal antibodies raised against the 58 amino acid sequence between the extracellular cleavage site and the transmembrane region of MUC16 were radiolabeled with [Zr]Zr. The radioimmunoconjugates were evaluated in vitro for molar activities, target binding affinity, cellular internalization and serum stability. In vivo characterization was performed via longitudinal positron emission tomography (PET) imaging and ex vivo biodistribution studies in mice bearing subcutaneous xenografts of SKOV3 cells transfected with the proximal 114 amino-acids of MUC16 carboxy-terminus (SKOV3+).
In vitro screening identified 9C9 and 4H11 as the lead antibody candidates based on their comparable binding affinities, serum stability and cellular internalization profiles. Despite an identical molecular footprint for binding to MUC16, [Zr]Zr-DFO-4H11 yielded a more favorable in vivo radiopharmacologic profile. Furthermore, a humanized variant of 4H11 capable of binding MUC16 in vitro also yielded excellent in vivo profile in subcutaneous xenograft models of SKOV3+, OVCAR3 tumors and a patient-derived xenograft model representative of HGSOC.
Radiopharmacologic screening of antibodies early during their development can provide crucial information pertinent to the in vitro characterization and in vivo pharmacokinetics. The favorable in vivo profile demonstrated by humanized 4H11 combined with the use of its murine predecessor for immunohistochemical staining of biopsied tumor tissues from HGSOC patients makes a unique pair of antibodies that is poised for clinical translation.
尽管存在局限性，但 CA125 仍然是诊断和治疗监测卵巢癌最广泛使用的生物标志物。针对血清生物标志物（如 CA125/MUC16）未释放的部分，可能会更特异性地对高级别浆液性卵巢癌（HGSOC）患者的 MUC16 阳性肿瘤进行成像和靶向。
针对 MUC16 细胞外切割位点和跨膜区之间的 58 个氨基酸序列，共制备了 6 种单克隆抗体，并用 [Zr]Zr 进行放射性标记。对放射性免疫偶联物进行了体外摩尔活性、靶标结合亲和力、细胞内化和血清稳定性评估。通过纵向正电子发射断层扫描（PET）成像和在皮下转染 MUC16 羧基末端近端 114 个氨基酸的 SKOV3 细胞系（SKOV3+）的荷瘤小鼠的体外生物分布研究进行体内特性研究。
体外筛选确定 9C9 和 4H11 为基于其相似结合亲和力、血清稳定性和细胞内化特征的领先抗体候选物。尽管与 MUC16 结合的分子足迹相同，但 [Zr]Zr-DFO-4H11 产生了更有利的体内放射药物特征。此外，能够在体外结合 MUC16 的 4H11 的人源化变体在 SKOV3+、OVCAR3 肿瘤的皮下异种移植模型和代表 HGSOC 的患者衍生异种移植模型中也表现出优异的体内特征。
在抗体开发的早期进行放射药物筛选，可以为体外特征和体内药代动力学提供重要信息。人源化 4H11 表现出良好的体内特征，结合其鼠源前体用于对 HGSOC 患者活检肿瘤组织进行免疫组织化学染色，使其成为一对具有独特临床转化潜力的抗体。
