Small Animal MRI with Protease-Sensing Contrast Agents

描述（由申请人提供）： 该I期STTR项目的目标是设计、合成和测试一类新的生化激活磁共振成像（MRI）造影剂，以检测和监测体内酶活性。该提案响应了题为“小动物成像系统和方法”的计划公告。我们的工作是基于这样的假设，即细胞外蛋白酶激活MRI造影剂代表了一种特别有前途的策略来检测和成像与癌症相关的生化过程。这代表了一个多学科的努力，汇集了癌症生物学，化学，酶学和物理学的专业知识，在工业和学术机构，以实现既定的目标;具体来说，我们建议确定是否肿瘤相关的基质金属蛋白酶（MMP）活性可以通过MRI在人类癌症的临床前模型中进行非侵入性成像。本课题的第一阶段主要研究蛋白酶靶点MRI检测试剂的制备和检测，具体目标如下：1）设计并制备钆螯合物MRI造影剂（蛋白水解造影剂，PCA），其在MMP裂解试剂后具有降低的水溶性; 2）在体内小鼠癌症模型的背景下表征未切割和蛋白酶切割的PCA的药效学性质。I期项目的成功将通过两个明确定义的里程碑的完成来判断：1）制备一种或多种基于Gd的MRI造影剂，其在体外响应于MMP的蛋白水解裂解而表现出水溶性降低至少10倍;和2）收集体内MRI数据，证明k（out）值，肿瘤的流出转移速率，MMP-阳性和MMP-阴性肿瘤之间和/或相对于在两种人类癌症小鼠模型中的至少一种中用不可裂解类似物测量的，即，通过证明MRI造影剂对PCA的蛋白水解裂解的时间响应的测量差异。该项目的成功有可能改善小动物和最终患者癌症的非侵入性检测和评估。它为该项目的第二阶段提供了基础，其总体目标是开发一种或多种商用PCA产品，以提供非侵入性临床评估，使癌症患者受益，并在临床实践中推进MRI在功能成像中的应用。

DESCRIPTION (provided by applicant): The goal of this Phase I STTR project is to design, synthesize, and test a new class of biochemically activated magnetic resonance imaging (MRI) contrast agents to detect and monitor enzymatic activity in vivo. The proposal responds to the Program Announcement entitled "Systems and methods for small animal imaging". We base this work on the hypothesis that activation of MRI contrast agents by extracellular proteases represents a particularly promising strategy to detect and image biochemical processes relevant to cancer. This represents a multi-disciplinary effort that brings together expertise in cancer biology, chemistry, enzymology, and physics at industrial and academic institutions to achieve the stated goals; specifically, we propose to determine if tumor-associated matrix metalloproteinase (MMP) activity can be non-invasively imaged by MRI in preclinical models of human cancer. We will approach the generation and testing of reagents useful for MRI detection of protease targets in Phase I of the project with the following specific aims: 1) Design and produce a gadolinium-chelate MRI contrast agent (Proteolytic Contrast Agent, PCA) that has decreased aqueous solubility following MMP cleavage of the agent; 2) Characterize the pharmacodynamic properties of both uncleaved and protease-cleaved PCAs in the context of in vivo mouse models of cancer. The success of the Phase I project will be judged by the completion of two well-defined milestones: 1) Preparation of one or more Gd-based MRI contrast agents that exhibit in vitro at least a 10-fold decrease in aqueous solubility in response to proteolytic cleavage by MMP; and 2) Collection of MRI data in vivo demonstrating a statistical difference in the value of k(out), the efflux transfer rate from the tumor, between MMP-positive and MMP-negative tumors and/or relative to that measured with an uncleavable analog in at least one of two mouse models of human cancer, i.e., by demonstrating a measured difference in the temporal response of the MRI contrast referable to proteolytic cleavage of the PCA. The success of this project has the potential for improved non-invasive detection and evaluation of cancer in small animals and eventually in patients. It provides the basis for Phase II of the project, with the overall goal of developing a commercial PCA product or products to provide for non-invasive clinical assessment to benefit patients with cancer, as well as to advance the use of MRI for functional imaging in clinical practice.