Abstract
Introduction
Dysregulated activity of matrix metalloproteinases (MMPs) drives a variety of pathophysiological conditions. Non-invasive imaging of MMP activity in vivo promises diagnostic and prognostic value. However, current targeting strategies by small molecules are typically limited with respect to the bioavailability of the labeled MMP binders in vivo. To this end, we here introduce and compare three chemical modifications of a recently developed barbiturate-based radiotracer with respect to bioavailability and potential to image MMP activity in vivo.
Methods
Barbiturate-based MMP inhibitors with an identical targeting unit but varying hydrophilicity were synthesized, labeled with technetium-99m, and evaluated in vitro and in vivo. Biodistribution and radiotracer elimination were determined in C57/BL6 mice by serial SPECT imaging. MMP activity was imaged in a MMP-positive subcutaneous xenograft model of human K1 papillary thyroid tumors. In vivo data were validated by scintillation counting, autoradiography, and MMP immunohistochemistry.
Results
We prepared three new 99mTc‐labeled MMP inhibitors, bearing either a glycine ([99mTc]MEA39), lysine ([99mTc]MEA61), or the ligand HYNIC with the ionic co-ligand TPPTS ([99mTc]MEA223) yielding gradually increasing hydrophilicity. [99mTc]MEA39 and [99mTc]MEA61 were rapidly eliminated via hepatobiliary pathways. In contrast, [99mTc]MEA223 showed delayed in vivo clearance and primary renal elimination. In a thyroid tumor xenograft model, only [99mTc]MEA223 exhibited a high tumor-to-blood ratio that could easily be delineated in SPECT images.
Conclusion
Introduction of HYNIC/TPPTS into the barbiturate lead structure ([99mTc]MEA223) results in delayed renal elimination and allows non-invasive MMP imaging with high signal-to-noise ratios in a papillary thyroid tumor xenograft model.
摘要
基质
金属
蛋白酶(
MMPs)的异常活性导致多种病理生理状况。非侵入性成像
MMP活性
in vivo有望提供诊断和预后价值。然而,目前小分子靶向策略通常受限于标记的
MMP结合剂
in vivo的
生物可用性。为此,我们在这里介绍并比较了一种最近开发的
巴比妥酸基放射性示踪剂的三种
化学修饰,以评估其
生物可用性和成像
MMP活性
in vivo的潜力。
方法
合成了具有相同靶向单元但亲
水性不同的
巴比妥酸基
MMP抑制剂,标记了
锝-99m,并进行了
in vitro和
in vivo评估。通过连续的
SPECT成像在C57/BL6小鼠中确定
生物分布和示踪剂清除。在人类K1乳头状甲状腺肿瘤的
MMP阳性皮下异种移植模型中成像
MMP活性。
in vivo数据通过闪烁计数、放射自显影和
MMP免疫组织
化学进行验证。
结果
我们制备了三种新的
99mTc标记的
MMP抑制剂,分别带有甘
氨酸([
99mTc]
MEA39)、赖
氨酸([
99mTc]
MEA61)或具有离子共
配体TPPTS的
配体HYNIC([
99mTc]
MEA223),逐渐增加亲
水性。[
99mTc]
MEA39和[
99mTc]
MEA61通过肝胆途径迅速排出。相反,[
99mTc]
MEA223显示出延迟的
in vivo清除和主要的肾脏排泄。在甲状腺肿瘤异种移植模型中,只有[
99mTc]
MEA223显示出高的肿瘤/血液比值,可以在
SPECT图像中轻松勾勒出来。
结论
将HYNIC/
TPPTS引入
巴比妥酸铅结构([
99mTc]
MEA223)中,导致延迟肾脏排泄,并允许在乳头状甲状腺肿瘤异种移植模型中进行高信噪比的非侵入性
MMP成像。