Zr-Df 标记的双特异性抗 PD-L1/TGF-βRII 融合蛋白 bintrafusp alfa 的放射性标记及临床前特征。
Radiolabelling and preclinical characterization of Zr-Df-radiolabelled bispecific anti-PD-L1/TGF-βRII fusion protein bintrafusp alfa.
机构信息
Tumour Targeting Laboratory, Olivia Newton-John Cancer Research Institute, 145 Studley Road, Heidelberg, Melbourne, Victoria, 3084, Australia.
School of Cancer Medicine, La Trobe University, Melbourne, Australia.
出版信息
Eur J Nucl Med Mol Imaging. 2021 Sep;48(10):3075-3088. doi: 10.1007/s00259-021-05251-0. Epub 2021 Feb 19.
PURPOSE
Τhis study aimed to optimize the Zr-radiolabelling of bintrafusp alfa investigational drug product and controls, and perform the in vitro and in vivo characterization of Zr-Df-bintrafusp alfa and Zr-Df-control radioconjugates.
METHODS
Bintrafusp alfa (anti-PD-L1 human IgG1 antibody fused to TGF-β receptor II (TGF-βRII), avelumab (anti-PD-L1 human IgG1 control antibody), isotype control (mutated inactive anti-PD-L1 IgG1 control antibody), and trap control (mutated inactive anti-PD-L1 human IgG1 fused to active TGF-βRII) were chelated with p-isothiocyanatobenzyl-desferrioxamine (Df). After radiolabelling with zirconium-89 (Zr), radioconjugates were assessed for radiochemical purity, immunoreactivity, antigen binding affinity, and serum stability in vitro. In vivo biodistribution and imaging studies were performed with PET/CT to identify and quantitate Zr-Df-bintrafusp alfa tumour uptake in a PD-L1/TGF-β-positive murine breast cancer model (EMT-6). Specificity of Zr-Df-bintrafusp alfa was assessed via a combined biodistribution and imaging experiment in the presence of competing cold bintrafusp alfa (1 mg/kg).
RESULTS
Nanomolar affinities for PD-L1 were achieved with Zr-Df-bintrafusp alfa and Zr-avelumab. Biodistribution and imaging studies in PD-L1- and TGF-β-positive EMT-6 tumour-bearing BALB/c mice demonstrated the biologic similarity of Zr-Df-bintrafusp alfa and Zr-avelumab indicating the in vivo distribution pattern of bintrafusp alfa is driven by its PD-L1 binding arm. Competition study with 1 mg of unlabelled bintrafusp alfa or avelumab co-administered with trace dose of Zr-labelled bintrafusp alfa demonstrated the impact of dose and specificity of PD-L1 targeting in vivo.
CONCLUSION
Molecular imaging of Zr-Df-bintrafusp alfa biodistribution was achievable and allows non-invasive quantitation of tumour uptake of Zr-Df-bintrafusp alfa, suitable for use in bioimaging clinical trials in cancer patients.
目的
本研究旨在优化 bintrafusp alfa 研究药物产品和对照品的 Zr 放射性标记，并对 Zr-Df-bintrafusp alfa 和 Zr-Df-对照品放射性缀合物进行体外和体内特性研究。
方法
将 bintrafusp alfa（抗 PD-L1 人 IgG1 抗体与 TGF-β 受体 II（TGF-βRII）融合，avelumab（抗 PD-L1 人 IgG1 对照抗体），同种型对照（突变失活的抗 PD-L1 IgG1 对照抗体）和陷阱对照（突变失活的抗 PD-L1 人 IgG1 与活性 TGF-βRII 融合）用对异硫氰酸苄基-去铁胺（Df）螯合。用锆-89（Zr）标记后，体外评估放射性缀合物的放射化学纯度、免疫反应性、抗原结合亲和力和血清稳定性。使用 PET/CT 进行体内生物分布和成像研究，以在 PD-L1/TGF-β 阳性的小鼠乳腺癌模型（EMT-6）中鉴定和定量 Zr-Df-bintrafusp alfa 肿瘤摄取。通过在存在竞争冷 bintrafusp alfa（1mg/kg）的情况下进行联合生物分布和成像实验来评估 Zr-Df-bintrafusp alfa 的特异性。
结果
Zr-Df-bintrafusp alfa 和 Zr-avelumab 对 PD-L1 的亲和力达到纳摩尔水平。在 PD-L1 和 TGF-β 阳性 EMT-6 荷瘤 BALB/c 小鼠中的生物分布和成像研究表明，Zr-Df-bintrafusp alfa 和 Zr-avelumab 的生物学相似性表明，bintrafusp alfa 的体内分布模式由其 PD-L1 结合臂驱动。用 1mg 未标记的 bintrafusp alfa 或与痕量 Zr 标记的 bintrafusp alfa 共给药的 avelumab 进行竞争研究表明了体内 PD-L1 靶向的剂量和特异性的影响。
结论
Zr-Df-bintrafusp alfa 生物分布的分子成像是可行的，允许对 Zr-Df-bintrafusp alfa 的肿瘤摄取进行非侵入性定量，适用于癌症患者的生物成像临床试验。
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