Whole Body Imaging of Beta Cell Mass in Diabetes

描述（由申请人提供）：本提案的总体目标是开发具有临床转化潜力的小鼠β细胞团块（BCM）的非侵入性全身成像。这些药物将用于在多种小鼠模型中研究I型糖尿病的进展，以阐明该疾病的病因和进展。候选人Greg Thurber在了解显像剂的分布和药代动力学方面拥有丰富的经验，并将运用这些技能设计新型显像剂和量化BCM。BCM显像剂的成功开发将对糖尿病研究领域做出重大贡献，极大地促进了疾病的诊断、进展和治疗干预。候选人的长期目标是开发新型显像剂，以解决糖尿病研究中的重要生物学问题。这项工作将在哈佛大学/MGH系统生物学中心进行，由Ralph Weissleder博士指导。由于候选人曾与这位导师一起进行T32培训，他还请来了糖尿病研究方面的专家Diane Mathis博士和Christophe Benoist博士为他提供额外的指导和专业知识。Marcelo Di Carli博士在获得临床翻译见解方面的支持也将包括在候选人的培训中。这些咨询委员会的成员将促进候选人从主要导师的工作过渡到发展一个成功的独立糖尿病研究人员的职业生涯。本提案的具体目标是首先开发一种具有优化性能的β细胞显像剂，用于全身成像，然后在各种动物模型中进行体内成像。这项工作源于对β细胞胰岛活体显微镜使用扩展素衍生物的初步研究。这些探针具有体内荧光成像的最佳药代动力学，但全身成像的额外限制，如脱靶摄取和放射化学合成，使这些探针不理想。广泛的药代动力学模拟表明，通过延长血浆半衰期和降低剂量，可以提高靶本比，提高检测灵敏度。此外，模拟表明了在炎症引起的可变递送情况下定量BCM所需的剂量和成像时间点。Specific aim 1将开发基于扩展蛋白肽的新型探针，通过聚乙二醇化和/或特异性白蛋白结合肽减少血浆清除率，用于β细胞靶向。这是一种有效的延长血浆半衰期和减少肾脏摄取的方法，广泛的体外和体内试验将用于确保充分的靶向性。特异性靶2将利用新型四氮和反环辛烯化学对靶1中的新型探针进行快速放射性标记，用于体内无创成像。多种用于研究1型糖尿病的新型动物模型将使用新型探针进行成像，以测试成像信号对不同BCM并发炎症的敏感性。如果成功，这些药物将允许对任何疾病动物模型的BCM进行纵向无创成像，并可用于监测进展和测量治疗干预。此外，全身成像使这些药物可能用于监测BCM患者的临床翻译。

DESCRIPTION (provided by applicant): The broad goal of this proposal is to develop non-invasive whole body imaging of beta cell mass (BCM) in mice with the potential for clinical translation. These agents will be used to study the progression of type I diabetes mellitus in a variety of mouse models to elucidate the etiology and progression of the disease. The candidate, Greg Thurber, has extensive experience in understanding the distribution and pharmacokinetics of imaging agents and will apply these skills to design novel agents and quantify BCM. The successful development of an imaging agent for measuring BCM would make a substantial contribution to the field of diabetes research, greatly facilitating the diagnosis, progression, and treatment intervention for the disease. The long term goal of the candidate is to develop novel imaging agents to address important biological questions in diabetes research. This work will be conducted in the Harvard/MGH Center for Systems Biology under the mentorship of Dr. Ralph Weissleder MD PhD. Since the candidate has worked with this mentor for his T32 training, he has also brought on Dr. Diane Mathis PhD and Dr. Christophe Benoist MD PhD, both experts in diabetes research, for additional mentoring and expertise. The support of Dr. Marcelo Di Carli MD in gaining insight into clinical translation will also be included in the candidate's training. These members of the advisory committee will facilitate the transition of the candidate's work away from the primary mentor to develop a successful career as an independent diabetes researcher. The specific aims of this proposal first develop a beta cell imaging agent with optimized properties for whole body imaging followed by in vivo imaging in a variety of animal models. This work stems from preliminary research using exendin derivatives for intravital microscopy of beta cell islets. These probes have optimal pharmacokinetics for in vivo fluorescence imaging, but the additional constraints for whole body imaging, such as off target uptake and radiochemical synthesis, make these probes non-ideal. Extensive pharmacokinetic simulations show that by extending the plasma half life and reducing the dose, the target to background ratio can be improved, increasing the sensitivity of detection. Additionally, the simulations indicate the doses and imaging time points required for quantitating BCM in the context of variable delivery due to inflammation. Specific aim 1 will develop novel probes based on the exendin peptide for beta cell targeting by reducing plasma clearance through PEGylation and/or specific albumin binding peptides. This is a well validated method for extending plasma half life and reducing renal uptake, and extensive in vitro and in vivo testing will be utilized to ensure adequate targeting. Specific aim 2 will utilize novel tetrazine and trans-cyclo- octene chemistry to rapidly radiolabel the novel probes from aim 1 for in vivo non-invasive imaging. A variety of novel animal models for studying type 1 diabetes will be imaged with the novel probes to test the sensitivity of imaging signal to varying BCM with concurrent inflammation. If successful, these agents will allow longitudinal non-invasive imaging of BCM for any animal model of disease and can be used for monitoring progression and measuring therapeutic intervention. Furthermore, the whole body imaging enables the possible clinical translation of these agents for monitoring BCM in patients.