Inhaled DNA demethylating therapy for lung cancer and bronchial premalignancy

描述(由申请人提供)：继发于启动子高甲基化的肿瘤抑制基因沉默在支气管癌变过程中起着关键作用。去甲基化药物5-氮杂胞苷在治疗白血病前期状态的骨髓发育不良中显示了临床疗效。我们实验室的初步研究表明，当5-氮胞苷通过气管内给药途径用于裸鼠原位人类肺癌模型时，其治疗指数增加了75倍。在这一应用中，我们建议进行临床前研究，并首次通过吸入进行5-氮胞苷的人体研究。我们的基本治疗策略包括利用5-氮胞苷的去甲基化特性，同时通过使用去甲基化的、无细胞毒性的剂量来避免其细胞毒性作用，通过长时间吸入直接给药到靶组织--支气管上皮。在我们开始拟议的5-氮胞苷吸入性临床I期研究之前，我们将确定吸入5-氮胞苷的最小有效剂量以及在相关的肺部癌前病变小鼠模型中的肺毒性。这些临床前研究将使我们能够合理地确定可能对人体既安全又有治疗作用的起始剂量。然后，我们建议进行一项可行性和原则性的第一阶段研究，目的是以靶组织中肿瘤抑制基因的重新表达为药效学终点，确定吸入5-氮胞苷的最佳生物剂量。其具体目的是：1.确定小鼠气管内吸入烟草致癌物的最佳剂量(第1年和第2年)。终点将是：肺毒性，延缓肺癌发展的有效性，以及在支气管上皮中肿瘤抑制基因的重新表达。2.对标准治疗失败(3-5年)的晚期非小细胞肺癌患者进行吸入5-氮胞苷的I期可行性和原理证明研究。终点将是：耐受性和毒性，特别强调肺毒性，肿瘤抑制基因在支气管上皮中的重新表达，以及支气管上皮中甲基化模式的变化。这项建议代表了一项长期计划的第一步，该计划旨在开发有针对性的表观遗传策略来治疗晚期支气管癌前病变，并最终预防肺癌。如果成功，这一战略将为极大一部分面临罹患癌症和死于癌症相关死亡最常见原因的风险的个人提供临床益处。 公共卫生相关性：由于缺乏有效的早期发现和干预策略，肺癌仍然是癌症相关死亡的头号原因。多年来，这种疾病仍然局限于呼吸道表面。我们建议开始在临床上探索一种新的早期干预策略，包括通过吸入给药，5-氮胞苷，具有逆转烟草对正常肺造成的遗传损害的潜力。如果成功，这种干预可能会推迟或有效地预防大量高危人群中肺癌的发生。

DESCRIPTION (provided by applicant): Tumor suppressor silencing secondary to promoter hypermethylation plays a key role in the bronchial carcinogenesis process. The demethylating agent 5-azacytidine has demonstrated clinical efficacy in the treatment of the preleukemic condition myelodysplasia. Preliminary studies in our laboratory have demonstrated a 75-fold increase in the therapeutic index of 5-azacytidine when the intratracheal route of administration is used against orthotopic human lung cancer models in nude mice. In this application we propose to perform preclinical studies and the first human study of 5-azacytidine by inhalation. Our basic therapeutic strategy consists of exploiting the demethylaring properties of 5-azacytidine while avoiding its cytotoxic effects by using demethylating, non-cytotoxic doses, directly delivered to the target tissue, the bronchial epithelium, by inhalation over long periods of time. Before we initiate the proposed clinical Phase I study of inhaled 5-azacytidine we will determine the minimal effective dose as well as the lung toxicity of inhaled 5-azacytitine in a relevant murine model of lung premalignancy. These preclinical studies will allow us to rationally determine the starting dose that is likely to be both safe and therapeutic in man. We then propose to perform a feasibility and proof of principle Phase I study aimed at determining the optimal biological dose of inhaled 5-azacytidine using tumor suppressor gene reexpression in the target tissue as the pharmacodynamic endpoint. The specific aims are: 1. To determine the optimal dose of inhaled 5- azacytidine in mice exposed to tobacco carcinogens intratracheally (years 1 and 2). Endpoints will be: lung toxicity, efficacy in delaying lung tumor development, and tumor suppressor gene reexpression in the bronchial epithelium. 2. To perform a Phase I feasibility and proof of principle study of inhaled 5-azacytidine in patients with advanced NSCLC after failure of standard therapy (years 3-5). Endpoints will be: tolerability and toxicity with special emphasis on lung toxicity, tumor suppressor gene reexpression in the bronchial epithelium, and changes in methylation patterns in the bronchial epithelium. This proposal represents the first step of a long term program aimed at developing targeted epigenetic strategies for the treatment of advanced bronchial premalignancy and eventually the prevention of lung cancer. If successful, this strategy will provide clinical benefit to the very large population of individuals at risk of developing and dying from the most common cause of cancer-related death. PUBLIC HEALTH RELEVANCE: Lung cancer remains the number one cause of cancer-related death because of lack of effective early detection and intervention strategies. For many years, the disease remains confined to the airway surface. We propose to start exploring clinically a new early intervention strategy consisting on delivering by inhalation an agent, 5 azacytidine that has the potential of reversing the genetic damage produced by tobacco in the normal lung. If successful, such intervention may postpone or effectively prevent the occurrence of lung cancer in the large population of individuals at risk.