Novel Therapy for Diabetic PAD Monitored With Dual Isotope Multimodality Imaging

 描述(申请人提供)：症状性外周动脉疾病(PAD)是糖尿病患者的一种致残状态，可导致腿部溃疡、截肢和死亡。目前还没有有效的药物治疗方法来治疗症状性PAD，手术血管重建术和基于介入导管的方法，这些方法都可能失败，导致肢体丧失。开发治疗PAD的新疗法和对治疗的图像反应是一个未得到满足的需求。晚期糖基化终末产物(AGEs)是由葡萄糖与蛋白质非酶结合而产生的。AGEs结合一个受体(RAGE)来启动通路，这些通路在加速糖尿病血管疾病的发生和发展以及通过抑制对肢体缺血的血管生成反应中发挥重要作用。我们开发了一种用于成像的抗RAGE的单抗，并在糖尿病和高脂血症的小鼠和猪身上表明，RAGE在后肢血管组织中广泛表达。我们还使用了成像来证实，敲除RAGE可以恢复对股动脉结扎造成的组织缺氧的正常反应。我们推测，如果我们的抗体是一种封闭抗体，它可能有潜力作为PAD的治疗剂，因此在血管平滑肌细胞培养中进行了验证性实验，以证明阻断特性。利用免疫组织学证实的影像，我们发现在糖尿病小鼠股动脉结扎后，与生理盐水组相比，抗体组小鼠缺血后肢在5天内血管生成明显增加，24天后血流改善，与安慰剂组小鼠相比。在这项拨款申请中，我们提出了一项使用双同位素多模式成像来记录治疗反应的大型动物治疗试验。目的饲养的糖尿病尤卡坦小型猪接受抗体或非免疫性免疫球蛋白2个月。一个月后，将在这些猪和其他年龄和体重匹配的非糖尿病尤卡坦小型猪身上进行基于导管的单侧股动脉闭塞(FAO)。在FAO 201Tl术后24小时(急性损伤)和28天(愈合)行SPECT/CT混合成像，用于肢体骨骼肌灌注和CT血管成像，用于大血管解剖。在FAO术后第7天，将用99mTcscVEGF-PEGDOTA(SCV/TC)进行SPECT/CT成像，这是一种新型的针对血管内皮生长因子受体1和2的探针，并在小鼠身上进行了初步实验，以追踪肢体缺血时的血管生成。局部后肢肌肉灌注将通过早期和晚期时间点的Tl-201摄取以及第7天摄取SCV/TC探针的肢体局部血管生成来量化。我们预计，与安慰剂组相比，抗体治疗组在第1天到第28天的灌注缺陷的减少将更大，这种变化的幅度将与第7天的SCV/TC的定量摄取和第28天的侧支血管评分有关。拟议工作的结果有可能成为进一步开发抗体和这种双同位素多模式成像方法进行临床试验的理由。

 DESCRIPTION (provided by applicant): Symptomatic peripheral arterial disease (PAD) is a disabling condition in diabetes that can lead to leg ulcers, amputation, and death. There are currently no effective drug therapies for symptomatic PAD leaving surgical revascularization and interventional catheter based approaches and these can fail leading to limb loss. Developing novel therapies to treat PAD and to image response to therapy represents an unmet need. Advanced Glycation End products (AGEs) are produced by the nonenzymatic binding of glucose to proteins. AGEs bind a receptor (RAGE) to initiate pathways that play important roles in accelerating the development and progression of vascular disease in diabetes and by inhibiting the angiogenic response to limb ischemia. We developed a monoclonal anti-RAGE antibody for imaging and have shown in diabetic and hyperlipidemic mice and pigs that RAGE is expressed diffusely in vascular tissue of hindlimbs. We have also used imaging to confirm that knocking out RAGE restores the normal response to tissue hypoxia imposed by femoral artery ligation. We hypothesized that if our antibody is a blocking antibody it may have potential as a therapeutic agent for PAD and consequently performed confirmatory experiments in cell culture of vascular smooth muscle cells to document blocking properties. Using imaging confirmed by immunohistology we showed in diabetic mice with femoral artery ligation pretreated with antibody vs. saline greater angiogenesis at 5 days and improved blood flow at 24 days in the ischemic hind limb of antibody treated mice compared to placebo treated mice. In this grant application we propose a large animal treatment trial using dual isotope multimodality imaging to document response to therapy. Purpose bred diabetic Yucatan minipigs will receive either antibody or non-immune IgG for 2 months. After one month, catheter based unilateral femoral artery occlusion (FAO) will be performed in these pigs plus additional age matched and weight matched non-diabetic Yucatan minipigs. At 24 h (acute insult) and 28 days (healing) after FAO 201Tl hybrid SPECT/CT imaging will be performed for limb skeletal muscle perfusion and CT angiography for large vessel anatomy. At day 7 after FAO hybrid SPECT/CT imaging will be performed with 99mTc scVEGF-PEG-DOTA (scV/Tc) a novel probe that targets VEGF receptors 1 and 2 and shown in preliminary experiments in mice to track angiogenesis in limb ischemia. Regional hindlimb muscle perfusion will be quantified from uptake of thallium-201 for early and late time points and regional limb angiogenesis from uptake of scV/Tc probe for day 7. We expect that the reduction in perfusion defects from day 1 to 28 will be greater in the antibody treated compared to placebo treated pigs and the magnitude of this change will relate to the quantitative uptake of scV/Tc at day 7 and to the collateral vessel score at day 28. The result of the proposed work has the potential to serve as justification for further development of the antibody and this dual isotope multimodality imaging approach towards a clinical trial.