Selective Inhibitors to Improve CPT-11 Therapy

说明(申请人提供)：CPT-11是一种喜树碱衍生的前药，它被羧酸酯酶(CE)激活而产生SN-38，一种有效的拓扑异构酶I抑制剂。CPT-11在动物模型中显示出显著的抗肿瘤活性，目前正被用于各种人类恶性肿瘤的临床试验。这种药物在肝脏中被激活，主要通过在胆汁中沉积来排泄。然而，这种药物的剂量限制毒性是迟发性腹泻，出现在给药后24-96小时。由于胆管开口进入十二指肠的肠道，十二指肠是肠道中CE和CPT-11转换活性最高的区域，我们认为腹泻是通过肠道中存在的人类肠道CE(HICE)的药物激活而发生的。为了减轻这种毒性，我们开发了选择性HICE抑制剂。在这一应用中，我们将使用各种分子模拟和QSAR技术来提高这些化合物的效力，并确定这些新化学物质抑制酶的机制。最后，我们将在动物模型中评估这些药物在减少CPT-11引起的腹泻方面的效果。 因此，本应用的具体目的是：1)基于SAR分析设计和合成选择性抑制剂；2)确定抑制作用的机制；3)评估新型抑制剂在体外和细胞培养系统中选择性抑制Hice的能力；4)建立受小鼠肠道CE启动子控制的Hice基因表达的小鼠模型；以及5)确定新型抑制剂是否可以改善CPT-11引起的小鼠腹泻。 总体而言，这些研究应该允许开发与CPT-11结合使用的选择性抑制剂，以降低该药物的毒性。此外，这些化合物可能会增强CPT-11的剂量，以改善癌症治疗。

DESCRIPTION (provided by applicant): CPT-11 is a camptothecin derived prodrug that is activated by carboxylesterases (CE) to yield SN-38, a potent topoisomerase I inhibitor. CPT-11 has demonstrated remarkable antitumor activity in animal models and is currently being used in clinical trials for a variety of human malignancies. The drug is activated in the liver and primarily excreted by deposition in the bile. However, the dose limiting toxicity for this drug is delayed diarrhea that occurs 24-96 hours following administration. Since the bile duct opens into the gut in the duodenum, the region of the intestine that demonstrates the highest levels of CE and CPT-11 converting activity, we propose that the diarrhea occurs via drug activation from the human intestinal CE (hiCE) present in the gut. In an attempt to ameliorate this toxicity, we have developed selective hiCE inhibitors. In this application, we will use a variety of molecular modeling and QSAR techniques to improve the potency of these compounds and determine the mechanism of enzyme inhibition by these novel chemicals. Finally, we will assess the efficacy of these agents towards reducing CPT-11-induced diarrhea in an animal model. The Specific Aims of this application are therefore to: 1) design and synthesize selective inhibitors based upon SAR analysis; 2) determine the mechanism of inhibition; 3) assess the ability of the novel inhibitors to selectively inhibit hiCE both in vitro and in cell culture systems; 4) generate a mouse model that results in expression of the hiCE cDNA under control of the mouse intestinal CE promoter; and 5) determine whether the novel inhibitors ameliorate CPT-11-induced diarrhea in this mouse model. Overall, these studies should allow development of selective inhibitors for use in combination with CPT-11 to reduce the toxicity of the drug. Additionally, such compounds may allow dose intensification of CPT-11 for improved cancer therapy.