Enhancing the efficacy of nucleoside analogs

描述(申请人提供)：尽管在治疗血液系统恶性肿瘤方面取得了进展，但大多数患者在最初的治疗反应后要么没有缓解，要么复发。核苷类似物(Nas)，包括阿糖胞嘧啶(Ara-C)、氟达拉滨、克拉德滨、五磷酸腺苷，以及最近的吉西他滨、曲西他滨和阿糖鸟嘌呤(Ara-G)，是目前用于治疗血液系统恶性肿瘤的最重要的治疗药物之一。它们的抗肿瘤活性依赖于细胞内酶转化为活性的磷酸化代谢物。脱氧胞苷酸激酶(DCK)催化所有这些前体药物的限速磷酸化步骤。这项应用寻求(1)开发一种将DCK输送到细胞内隔室的治疗系统，以克服NA激活的速率限制步骤，以及(2)为该治疗系统设计具有更高催化活性的酶。我们将使用Ara-C作为这些研究的模型化疗DCK底物，并使用抗CD33抗体作为肿瘤靶向配体。CD33抗原由髓系白血病原始细胞表达，但不表达造血干细胞或其他组织。我们将测试这种“结合疗法”在体外和体内的应用，增加阿糖胞苷(Ara-C，Ara-C)的胞内形态，增强其化疗效果。我们将操纵酶的结构，以提高核苷类似物联合治疗的疗效和治疗指数。几种肿瘤靶向抗体已经在临床上用于将附着的蛋白质、药物或放射性同位素内化到肿瘤细胞中。与放射性同位素和药物系统相比，这里提出的具有更高活性的酶的选择性递送具有潜在的降低毒性的优势。该项目的长期目标是开发方法，将这种选择性增强的酶传递系统(种子)应用于多种类型的恶性肿瘤。

DESCRIPTION (provided by applicant): Despite advances in treating hematological malignancies, most patients either do not achieve remission or relapse after an initial therapeutic response. Nucleoside analogues (NAs), including arabinosyl cytosine (ara-C), fludarabine, cladribine, pentostatin, and more recently gemcitabine, troxcitabine and arabinosyl guanine (ara-G), are among the most important therapeutic agents currently used to treat hematological malignancies. Their antitumor activity depends on conversion to active, phosphorylated metabolites by intracellular kinases. Deoxycytidine kinase (dCK) catalyzes the rate-limiting phosphorylation step for the activation of all of these prodrugs. This application seeks (1) to develop a therapeutic system for delivery of dCK to the intracellular compartment to overcome the rate limiting step in NA activation, and (2) to engineer enzymes with improved catalytic activity for this therapeutic system. We will use ara-C as the model chemotherapeutic dCK substrate for these studies and an anti-CD33 antibody as the tumor targeting ligand. CD33 antigen is expressed by myeloid leukemia blasts, but not hematopoietic stem cells or other tissues. We will test the application that this "conjugate therapy" will increase the intracellular form of ara-C (ara-C triphosphate) and enhance its chemotherapeutic effect both in vitro and in vivo. We will manipulate enzyme structure with the goal of increasing both the efficacy and the therapeutic index of combined treatment with nucleoside analogues. Several tumor targeting antibodies are already in clinical use to internalize an attached protein, drug, or radioisotope into tumor cells. The selective delivery of enzymes with increased kinase activity that is proposed here has the potential advantage of reduced toxicity compared with radioisotope and drug systems. The long-term goal of this project is to develop methods to translate this Selective Enhanced Enzyme Delivery System (SEEDS) to applications for multiple types of malignancies.