Department of Radiology and Molecular Imaging, University of California San Francisco, 185 Berry St., Suite 350, San Francisco, CA, 94107, USA.
Department of Radiation Oncology, University of California San Francisco, 2340 Sutter St., San Francisco, CA, 94115, USA.
Mol Imaging Biol. 2020 Feb;22(1):105-114. doi: 10.1007/s11307-019-01363-0.
Tumor necrosis factor alpha (TNFα) drives inflammation and bone degradation in patients with rheumatoid arthritis (RA). Some RA patients experience a rapid clinical response to TNFα inhibitors such as certolizumab pegol (CZP) while other patients show limited to no response. Current methods for imaging RA have limited sensitivity and do not assist in the selection of patients most likely to respond to immune-mediated therapy. Herein, we developed a novel positron emission tomography (PET) radiotracer for immuno-PET imaging of TNFα in transgenic human TNFα-expressing mice.
CZP was modified with p-isothiocyanatobenzyl-deferoxamine (DFO) and radiolabeled with Zr-89. The biological activity of [Zr]DFO-CZP was evaluated by HPLC and binding assay using human recombinant TNFα (hTNFα). The feasibility of specific immuno-PET imaging of human TNFα was assessed in a transgenic mouse model of RA that expresses human TNFα. This model resembles the progression of RA in humans by maintaining lower levels of circulating hTNFα and exhibits chronic arthritis in the forepaw and hind paw joints. The dosimetry of [Zr]DFO-CZP in humans was estimated using microPET/CT imaging in Sprague Dawley rats.
[Zr]DFO-CZP was isolated with radiolabeling yields of 85 ± 6 % (n = 5) and specific activities ranging from 74 to 185 MBq/mg (n = 5). Following size exclusion purification, the radiochemical purity of [Zr]DFO-CZP was greater than 97 %. [Zr]DFO-CZP retained high immunoreactivity with more than 95 % of the radioactivity shifted into higher molecular weight complexes. Images showed increasing uptake of the tracer in forepaw and hind paw joints with disease progression. No uptake was observed in the model previously administered with an excess amount of unmodified CZP and in normal control mice, demonstrating in vivo specific uptake of [Zr]DFO-CZP.
The feasibility of immuno-PET imaging of human TNFα with [Zr]DFO-CZP has been demonstrated in a preclinical model of RA.
肿瘤坏死因子-α（TNFα）可导致类风湿关节炎（RA）患者发生炎症和骨降解。一些 RA 患者对 TNFα 抑制剂（如 certolizumab pegol，CZP）表现出快速的临床应答，而其他患者则表现出有限或无应答。目前用于 RA 的成像方法灵敏度有限，无法帮助选择最有可能对免疫介导治疗产生应答的患者。在此，我们开发了一种新型正电子发射断层扫描（PET）放射性示踪剂，用于对表达人 TNFα 的转基因人 TNFα 表达小鼠进行免疫 PET 成像。
用对异硫氰酸苯甲基去铁胺（DFO）进行修饰，并与 Zr-89 进行放射性标记。通过高效液相色谱法（HPLC）和使用人重组 TNFα（hTNFα）的结合测定评估 [Zr]DFO-CZP 的生物学活性。通过表达人 TNFα 的 RA 转基因小鼠模型评估了特异性免疫 PET 成像人 TNFα 的可行性。该模型通过维持较低水平的循环 hTNFα 并在前爪和后爪关节中表现出慢性关节炎，类似于人类 RA 的进展。使用 microPET/CT 成像在 Sprague Dawley 大鼠中估计了 [Zr]DFO-CZP 在人体内的剂量学。
[Zr]DFO-CZP 的放射性标记产率为 85±6%（n=5），放射性比活度范围为 74 至 185MBq/mg（n=5）。经过分子筛纯化后，[Zr]DFO-CZP 的放射化学纯度大于 97%。[Zr]DFO-CZP 保留了高免疫反应性，超过 95%的放射性活性转移到高分子量复合物中。随着疾病的进展，图像显示示踪剂在前爪和后爪关节中的摄取量逐渐增加。在之前给予过量未修饰的 CZP 的模型和正常对照小鼠中未观察到摄取，表明 [Zr]DFO-CZP 具有体内特异性摄取。
在 RA 的临床前模型中已经证明了使用 [Zr]DFO-CZP 进行人 TNFα 免疫 PET 成像的可行性。
