SYNTHESES AND CELLULAR STUDIES OF NEW PHOTOSENSITIZERS FOR MEDICAL APPLICATIONS

描述(由申请人提供)：本提案侧重于设计、合成、开发和优化有望用于癌症和老年性黄斑变性诊断和治疗、用于抗动脉粥样硬化病变、用于从血液中清除病毒、骨髓净化以及抑制传染性海绵状脑病[牛(疯牛病)、羊(瘙痒病)和人型(Creutzfeld-Jacob病)]的四吡咯光动力疗法(PDT)光敏剂。光动力疗法是一种二元疗法，涉及针对特定细胞的光敏剂的光激活。这会导致产生单线态氧和其他细胞毒性物质，导致疾病细胞破坏，同时保留健康组织。只有两种FDA批准的四吡咯光敏剂--Photofrin和Visudyne；这两种药物都是对肿瘤组织具有有限选择性的化合物的混合物。提出了一种新的高效有机合成四吡咯光敏剂的新方法：氨基酸、多肽和聚乙二醇偶联物(1)二氯e6，(2)异卟啉，(3)苯并卟啉和卟啉。在很大程度上，其目的是制备针对细胞和特定细胞器的光敏剂，用于PDT治疗病变细胞和斑块。合成的四吡咯光敏剂将通过与一种或多种氨基酸、短肽或固定长度的聚乙二醇共轭，定向到特定的细胞器(最好是线粒体)。在任何一系列合成增敏剂中都有足够的例子可以研究细胞摄取、细胞内定位和细胞毒性的机制。最有希望的增敏剂的细胞死亡模式也将被确定。这项研究将导致结构/活性关系，这些关系对于设计和开发更好、更有效的PDT光敏剂至关重要，这些光敏剂用于癌症、心血管、输血、骨髓净化和海绵状脑病等医学领域。广泛的初步研究已经完成，并表明拟议研究的所有方面都是可行的。这些新药还将在内部调查细胞摄取、细胞内定位和暗/光毒性，并与细胞死亡模式(促进细胞凋亡而不是坏死)的顾问一起进行研究；根据生物学工作的反馈，可能会迅速修改方法。这将有可能平衡药物的生化和物理化学特性与其光动力疗法的效果，并利用机理知识来开发更有效的光动力疗法增敏剂。旨在了解新型四吡咯增敏剂的细胞靶向、摄取和亚细胞定位的机制，并开发新的高效医用药物。 公共卫生相关性：拟议的计划与公共健康具有重大相关性，因为癌症仍然是美国第二大最常见的死亡原因，而黄斑变性、动脉粥样硬化、病毒性血液和骨髓污染以及海绵状脑病是主要的世界性问题。光动力疗法(PDT)是FDA已经批准的一种治疗方式，并继续获得临床接受。只有发现具有更高细胞选择性和特异性的新药物，研究其生物学作用机制，并相对于现有模式评估其疗效，才能充分发挥其潜力。

DESCRIPTION (provided by applicant): This proposal focuses on the design, synthesis, development and optimization of promising tetrapyrrole photodynamic therapy (PDT) photosensitizers for use in diagnosis and treatment of cancer and age-related macular degeneration, for use against atherosclerotic lesions, in virus eradication from blood, bone marrow purging, and for inhibition of transmissible spongiform encephalopathies [bovine (BSE), sheep (scrapie) and human forms (Creutzfeld-Jacob disease)]. PDT is a binary therapy involving light-activation of a photosensitizer that has been targeted to specific cells. This results in the generation of singlet oxygen and other cytotoxic species that cause disease cell destruction while sparing healthy tissues. There are only two FDA-approved tetrapyrrole photosensitizers - Photofrin and Visudyne; both of these drugs are mixtures of compounds with limited selectivity for tumor tissue. It is proposed to develop new efficient organic synthesis methods to three types of tetrapyrrole photosensitizer: amino acid, peptide, and polyethylene glycol (PEG) conjugates of (1) chlorin e6, (2) isoporphyrins, and (3) benzoporphyrins and porphycenes. For the most part, the aim is to prepare cell- and specific organelle-targeted photosensitizers for the PDT treatment of diseased cells and plaque. The tetrapyrrole photosensitizers that are synthesized will be directed to specific organelles (preferably the mitochondria) by conjugation with one or more amino acid, short peptide, or PEG of defined length. Sufficient examples within any series of synthetic sensitizers will permit the investigation of mechanisms of cellular uptake, intracellular localization and cytotoxicity. Modes of cell death for the most promising sensitizers will also be determined. This research will result in structure/activity relationships that are crucial in the design and development of better and more effective PDT photosensitizers for use in cancer, cardiovascular, blood transfusion, bone marrow purging, and spongiform encephalopathy areas of medicine. Extensive preliminary studies have been completed and show viability of all aspects of the proposed research. The new drugs will also be investigated in house for cellular uptake, intracellular localization and dark/light toxicity, and with a consultant for modes of cell death (promoting apoptosis over necrosis); rapid modifications of approach will be possible based on feedback from the biological work. It will be possible to balance biochemical and physicochemical characteristics of drugs with their PDT efficacy, and to use mechanistic knowledge to develop more effective PDT sensitizers. It is intended to understand the mechanisms of cellular targeting, uptake and subcellular localization of new tetrapyrrole sensitizers and to develop new highly effective drugs for medical use. PUBLIC HEALTH RELEVANCE: The proposed program is of major relevance to public health because cancer remains the second most common cause of death in the USA, and macular degeneration, atherosclerosis, viral blood and bone marrow contaminants, and spongiform encephalopathies are major world problems. Photodynamic therapy (PDT) is a treatment modality already approved by the FDA that continues to gain clinical acceptance. The full potential can be realized only when new drugs with higher cellular selectivity and specificity are discovered, their mechanisms of biological action investigated, and their efficacy evaluated relative to existing modalities.