Molecular Imaging Program at Stanford (MIPS), Department of Radiology and Bio-X Program, Stanford University, Stanford, California, 94305, USA.
Bioconjug Chem. 2011 Mar 16;22(3):413-21. doi: 10.1021/bc100432h. Epub 2011 Feb 7.
Affibody molecules have received significant attention in the fields of molecular imaging and drug development. However, Affibody scaffolds display an extremely high renal uptake, especially when modified with chelators and then labeled with radiometals. This unfavorable property may impact their use as radiotherapeutic agents in general and as imaging probes for the detection of tumors adjacent to kidneys in particular. Herein, we present a simple and generalizable strategy for reducing the renal uptake of Affibody molecules while maintaining their tumor uptake. Human serum albumin (HSA) was consecutively modified by 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid mono-N-hydroxysuccinimide ester (DOTA-NHS ester) and the bifunctional cross-linker sulfosuccinimidyl 4-[N-maleimidomethyl]cyclohexane-1-carboxylate (Sulfo-SMCC). The HER2 Affibody analogue, Ac-Cys-Z(HER2:342), was covalently conjugated with HSA, and the resulting bioconjugate DOTA-HSA-Z(HER2:342) was further radiolabeled with ⁶⁴Cu and ¹¹¹In and evaluated in vitro and in vivo. Radiolabeled DOTA-HSA-Z(HER2:342) conjugates displayed a significant and specific cell uptake into SKOV3 cell cultures. Positron emission tomography (PET) investigations using ⁶⁴Cu-DOTA-HSA-Z(HER2:342) were performed in SKOV3 tumor-bearing nude mice. High tumor uptake values (>14% ID/g at 24 and 48 h) and high liver accumulations but low kidney accumulations were observed. Biodistribution studies and single-photon emission computed tomography (SPECT) investigations using ¹¹¹In-DOTA-HSA-Z(HER2:342) validated these results. At 24 h post injection, the biodistribution data revealed high tumor (16.26% ID/g) and liver (14.11% ID/g) uptake but relatively low kidney uptake (6.06% ID/g). Blocking studies with coinjected, nonlabeled Ac-Cys-Z(HER2:342) confirmed the in vivo specificity of HER2. Radiolabeled DOTA-HSA-Z(HER2:342) Affibody conjugates are promising SPECT and PET-type probes for the imaging of HER2 positive cancer. More importantly, DOTA-HSA-Z(HER2:342) is suitable for labeling with therapeutic radionuclides (e.g., ⁹⁰Y or ¹⁷⁷Lu) for treatment studies. The approach of using HSA to optimize the pharmacokinetics and biodistribution profile of Affibodies may be extended to the design of many other targeting molecules.
亲和体分子在分子成像和药物开发领域受到了广泛关注。然而，亲和体支架显示出极高的肾脏摄取率，尤其是在用螯合剂修饰后再用放射性金属标记时。这种不利的特性可能会影响它们作为放射治疗剂的一般用途，以及作为检测紧邻肾脏的肿瘤的成像探针的用途。在此，我们提出了一种简单且可推广的策略，可降低亲和体分子的肾脏摄取率，同时保持其对肿瘤的摄取率。人血清白蛋白（HSA）依次用 1,4,7,10-四氮杂环十二烷-1,4,7,10-四乙酸单-N-羟基琥珀酰亚胺酯（DOTA-NHS 酯）和双功能交联剂磺基琥珀酰亚胺基 4-[N-马来酰亚胺甲基]环己烷-1-羧酸酯（Sulfo-SMCC）修饰。HER2 亲和体类似物 Ac-Cys-Z（HER2:342）与 HSA 共价偶联，所得的生物缀合物 DOTA-HSA-Z（HER2:342）进一步用 64Cu 和 111In 标记，并进行了体外和体内评价。放射性标记的 DOTA-HSA-Z（HER2:342）缀合物在 SKOV3 细胞培养物中表现出显著的特异性细胞摄取。使用 64Cu-DOTA-HSA-Z（HER2:342）进行正电子发射断层扫描（PET）研究在 SKOV3 荷瘤裸鼠中进行。观察到高肿瘤摄取值（24 和 48 小时时＞14% ID/g）和高肝脏蓄积但低肾脏蓄积。使用 111In-DOTA-HSA-Z（HER2:342）进行的生物分布研究和单光子发射计算机断层扫描（SPECT）研究验证了这些结果。在注射后 24 小时，生物分布数据显示出高肿瘤（16.26% ID/g）和肝脏（14.11% ID/g）摄取率，但相对较低的肾脏摄取率（6.06% ID/g）。用共注射的非标记 Ac-Cys-Z（HER2:342）进行的阻断研究证实了 HER2 的体内特异性。放射性标记的 DOTA-HSA-Z（HER2:342）亲和体缀合物是用于 HER2 阳性癌症成像的有前途的 SPECT 和 PET 型探针。更重要的是，DOTA-HSA-Z（HER2:342）适合用治疗性放射性核素（例如 90Y 或 177Lu）标记，用于治疗研究。使用 HSA 优化亲和体的药代动力学和生物分布特征的方法可扩展到许多其他靶向分子的设计。
