The neuropathological hallmark of Parkinsońs disease, multiple system atrophy and dementia with Lewy bodies is the accumulation of α-synuclein. The development of an imaging biomarker for α-synuclein is an unmet need. To date, no selective α-synuclein imaging agent has been identified, though initial studies suggest that the tau tracer [¹¹C]PBB3 displays some degree of binding to α-synuclein. In this study, a series of compounds derived from the PBB3 scaffold were examined using fluorescence imaging and tissue microarrays (TMAs) derived from brain samples with different proteinopathies. One compound, C05-01, was selected based on its higher fluorescence signal associated with Lewy body aggregates compared with other PBB3 analogues. In vitro binding assays using human brain homogenates and recombinant fibrils indicated that C05-01 had higher affinity for α-synuclein (KD/Ki 25 nM for fibrils, Ki 3.5 nM for brain homogenates) as compared with PBB3 (KD 58 nM). In autoradiography (ARG) studies using fresh frozen human tissue and TMAs, [³H]C05-01 displayed specific binding in cases with α-synuclein pathology.

C05-01 is the first PBB3 analogue developed as a potential compound targeting α-synuclein. Despite improved affinity for α-synuclein, C05-01 showed specific binding in AD tissue with Amyloid β and tau pathology, as well as relatively high non-specific and off-target binding. Additional efforts are needed to optimize the pharmacological and physicochemical properties of this series of compounds as ligands for α-synuclein. This study also showed that the construction of TMAs from different proteinopathies provides a tool for evaluation of fluorescent or radiolabelled compounds binding to misfolded proteins.

帕金森病、多系统萎缩和路易体痴呆的神经病理学标志是 α-突触核蛋白的积累。α-突触核蛋白成像生物标志物的开发是一个未满足的需求。迄今为止，尚未鉴定出选择性 α-突触核蛋白显像剂，尽管初步研究表明 tau 示踪剂 [ ¹¹ C] PBB3 显示出与 α-突触核蛋白一定程度的结合。在这项研究中，使用荧光成像和组织微阵列 (TMA) 检测了一系列来自 PBB3 支架的化合物，这些化合物来自具有不同蛋白质病的大脑样本。选择一种化合物 C05-01 是因为与其他 PBB3 类似物相比，它与路易体聚集体相关的荧光信号更高。体外使用人脑匀浆和重组原纤维的结合测定表明，与 PBB3 (KD 58 nM) 相比，C05-01 对 α-突触核蛋白具有更高的亲和力（原纤维的 KD/Ki 25 nM，脑匀浆的 Ki 3.5 nM）。在使用新鲜冷冻人体组织和 TMA 的放射自显影 (ARG) 研究中，[ ³ H]C05-01 在 α-突触核蛋白病理情况下显示出特异性结合。

C05-01 是第一个开发作为靶向 α-突触核蛋白的潜在化合物的 PBB3 类似物。尽管对 α-突触核蛋白的亲和力有所提高，但 C05-01 在 AD 组织中表现出与淀粉样蛋白 β 和 tau 病理的特异性结合，以及相对较高的非特异性和脱靶结合。需要额外的努力来优化这一系列化合物作为 α-突触核蛋白的配体的药理和理化性质。该研究还表明，构建来自不同蛋白质病的 TMA 为评估与错误折叠蛋白质结合的荧光或放射性标记化合物提供了一种工具。