HUMAN CARBOXYLESTERASES FOR TARGETED CPT-11 ACTIVATION

CPT-11是一种临床批准的抗癌药物。当在人体内使用时，CPT-11充当前药，并被羧酸酯酶转化为活性药物SN-38，一种具有大约1000倍细胞毒活性的试剂。由于注射的CPT-11只有2-5%被转化为SN-38，因此有很大的机会通过在肿瘤内产生活性药物来提高其活性并降低其全身毒性。这将通过癌症化疗的两步方法来完成，在给药CPT-11之前，允许单抗-羧酸酯酶结合物与细胞表面抗原结合。CPT-11与结合的偶联物接触后将转化为SN-38。人类羧酸酯酶的一种形式已经被鉴定出来，它可以影响CPT-11的激活，与兔、豚鼠和恒河猴中报道的最有效的酶一样。本研究的目的是从其氨基酸序列中鉴定这种人的羧酸酯酶，将其连接到抗肿瘤单抗上，并鉴定它们在体外和体内激活CPT-11的能力。这种单抗-酶/前药组合是独特的，因为它利用人酶和临床批准的抗癌药物来实现治疗效果。拟议的商业应用：CPT-11被广泛用于治疗许多常见的癌症、淋巴瘤和白血病，无论是作为单一药物还是药物组合，尽管它具有严重的剂量限制毒性。用单抗-羧酸酯酶结合物在实体瘤内产生活性形式的CPT-11，可获得较好的治疗效果和较低的全身毒性。这将是癌症临床治疗的重大进步。

CPT-11 is a clinically approved anticancer agent. When administered in people, CPT-11 acts as a prodrug, and is converted by carboxylesterases to the active drug, SN-38, an agent with approximately 1 ,000 times more cytotoxic activity. Since only 2 - 5% of the injected CPT-11 is converted to SN-38, a great opportunity exists to improve its activity and to lower its systemic toxicity by generating the active drug intratumorally. This will be accomplished in a two-step approach to cancer chemotherapy, in which a monoclonal antibody-carboxylesterase conjugate is allowed to bind to cell- surface antigens prior to the administration of CPT-11. Upon contact with the bound conjugate, CPT-11 will be converted to SN-38. A form of human carboxylesterase has been identified that can effect CPT-11 activation approximately as well as the most efficient enzymes reported from rabbit, guinea pig, and rhesus monkey. The aims of this study are to identify this human carboxylesterase from its amino acid sequence, attach the enzyme to antitumor monoclonal antibodies, and to characterize the conjugates for their abilities to activate CPT-11 both in vitro and in vivo. This mAb-enzyme/prodrug combination is unique, in that it utilizes a human enzyme and a clinically approved anticancer drug to achieve therapeutic efficacy. PROPOSED COMMERCIAL APPLICATIONS: CPT-11 is used widely, either as a single agent, or in drug combinations for the treatment of many common carcinomas, lymphomas and leukemia, even though it has severe dose limiting toxicities. Generation of the active form of CPT-11 inside solid tumors by mAb-carboxylesterase conjugates could lead to better therapeutic efficacy and lower levels of systemic toxicity. This would constitute a major advancement in the clinical treatment of cancer.