Department of Radiology, Duke University Medical Center, Durham, North Carolina 27710, United States.
Mol Pharm. 2021 Oct 4;18(10):3871-3881. doi: 10.1021/acs.molpharmaceut.1c00531. Epub 2021 Sep 15.
RG7388 (Idasanutlin) is a potent inhibitor of oncoprotein murine double minute 2 (MDM2). Herein we investigated the feasibility of developing F-labeled RG7388 as a radiotracer for imaging MDM2 expression in tumors with positron emission tomography (PET). Two fluorinated analogues of RG7388, and , were synthesized by attaching a fluoronicotinyl moiety to RG7388 via a polyethylene glycol (PEG) or a propyl linker. The inhibitory potency (IC) of and against MDM2 was determined by a fluorescence polarization (FP)-based assay. Next, compound was labeled with F using a trimethylammonium triflate precursor to obtain [F]FN-PEG-RG7388 ([F]), and its properties were evaluated in MDM2 expressing wild-type p53 tumor cell lines (SJSA-1 and HepG2) in vitro and in tumor xenografts in vivo. The FP assays revealed an IC against MDM2 of 119 nM and 160 nM for and , respectively. F-labeling of was achieved in 50.3 ± 7.5% radiochemical yield. [F] exhibited a high uptake (∼70% of input dose) and specificity in SJSA-1 and HepG2 cell lines. Saturation binding assays revealed a binding affinity () of 128 nM for [F] on SJSA-1 cells. In mice, [F] showed fast clearance from blood with a maximum tumor uptake of 3.80 ± 0.85% injected dose per gram (ID/g) in HepG2 xenografts at 30 min postinjection (p.i.) and 1.32 ± 0.32% ID/g in SJSA-1 xenografts at 1 h p.i. Specificity of [F] uptake in tumors was demonstrated by pretreatment of mice with SJSA-xenografts with a blocking dose of RG7388 (35 mg/kg body weight, i.p.). In vivo stability studies in mice using HPLC showed ∼60% and ∼30% intact [F] remaining in plasma at 30 min and 1 h p.i., respectively, with the remaining activity attributed to polar peaks. Our results suggest that RG7388 is a promising molecular scaffold for F-labeled probe development for MDM2. Additional labeling strategies and functionalizing locations on RG7388 are under development to improve binding affinity and in vivo stability of the F-labeled compound to make it more amenable for PET imaging of MDM2 in vivo.
RG7388（Idasanutlin）是一种有效的癌蛋白鼠双微体 2（MDM2）抑制剂。在此，我们研究了将 F 标记的 RG7388 开发为正电子发射断层扫描（PET）成像肿瘤中 MDM2 表达的示踪剂的可行性。通过将氟代烟酰基部分通过聚乙二醇（PEG）或丙基接头连接到 RG7388 上，合成了两种 RG7388 的氟化类似物 和 。通过荧光偏振（FP）测定法测定 和 对 MDM2 的抑制效力（IC）。接下来，使用三氟甲磺酸三甲铵前体将 标记为 F，以获得 [F]FN-PEG-RG7388（[F]），并在体外表达野生型 p53 的 SJSA-1 和 HepG2 肿瘤细胞系以及体内肿瘤异种移植中评估其特性。FP 测定显示， 和 对 MDM2 的 IC 分别为 119 nM 和 160 nM。 在 50.3±7.5%的放射化学产率下实现了 F 标记。 [F]在 SJSA-1 和 HepG2 细胞系中表现出高摄取（约为输入剂量的 70%）和特异性。饱和结合测定显示，[F]在 SJSA-1 细胞上的结合亲和力（）为 128 nM。在小鼠中，[F]在血液中的清除速度很快，在注射后 30 分钟（p.i.）时 HepG2 异种移植瘤中的最大肿瘤摄取量为 3.80±0.85%注入剂量/克（ID/g），1 小时 p.i.时 SJSA-1 异种移植瘤中为 1.32±0.32% ID/g。通过用 35 mg/kg 体重（腹腔内）的 RG7388 对携带 SJSA- 异种移植瘤的小鼠进行预处理，证明了 [F]摄取的特异性。使用 HPLC 进行的小鼠体内稳定性研究表明，在 30 分钟和 1 小时 p.i.时，分别有∼60%和∼30%的完整[F]仍留在血浆中，其余活性归因于极性峰。我们的结果表明，RG7388 是开发用于 MDM2 的 F 标记探针的有前途的分子支架。正在开发其他标记策略和 RG7388 上的功能化位置，以提高 F 标记化合物的结合亲和力和体内稳定性，使其更适合用于 MDM2 的体内 PET 成像。
