Boronated nucleosides for neutron capture therapy of brain tumors

描述(由申请人提供)：传统癌症治疗的进步并没有在治疗多形性胶质母细胞瘤(GBM)方面产生任何显著的改善。因此，进一步开发新的治疗方式，如硼中子俘获疗法(BNCT)，仍然是美国卫生科学界的一项紧迫任务。目前拨款申请的主题是继续开发3-Carboranyl胸苷类似物(3CTA)，这是一种治疗GBM的新型BNCT药物。3CTA的作用机制主要是基于它们作为人胸苷激酶1(TK1)底物的能力，TK1只在增殖细胞中活跃。通过脑内(I.C.)接受N5-2OH的荷瘤啮齿动物的BNCT，N5-2OH是我们3CTA文库的当前先导化合物。或瘤内(I.T.)注射导致肿瘤生长减少，生存时间延长。另一方面，同样的研究也揭示了N5-2OH和其他3CTA的两个主要局限性。它们是(1)TK1底物结合部位与内源性胸腺嘧啶核苷(THD)的次优竞争和(2)缺乏水溶性，这需要使用有机溶剂来溶解3CTA用于生物学研究。此外，3CTA的关键生化和生物学特性仍不清楚。这些是(3)超过单磷酸化步骤的3CTA的合成代谢，包括它们可能结合到DNA中，以及(4)3CTA及其代谢产物招募进入和离开细胞的机制。针对这些不足，我们开发了以下具体目标：(1)合成在TK1活性部位与THD竞争能力增强的3CTA，在TK1酶分析中评价它们的底物和抑制能力，并测定它们的理化性质；(2)合成N5-2OH的水溶性氨基酸前体药物，并评价它们对I.C.的适用性。(3)研究N5-2OH和3CTA的体外代谢，以及在核苷酸酶和DNA聚合酶检测中的代谢；(4)研究N5-2OH、3CTA及其代谢产物的细胞内流和流出机制；(5)优化I.C.将特异性靶点1-4产生的具有最大改善的类药物和酶性质的3CTA应用于RG2胶质瘤荷瘤大鼠，并确定可能的神经毒性。公共卫生相关性：将开发新的硼化核苷，用于通过硼中子俘获疗法(BNCT)治疗脑肿瘤。BNCT是一种癌症的二元治疗方式，既依赖于化学成分，也依赖于辐射成分。被称为多形性胶质母细胞瘤的脑瘤是所有癌症中最致命的癌症之一。传统癌症治疗的进展并没有在这些脑瘤的治疗方面产生任何显着的改善。含硼核苷的脑肿瘤的BNCT可能具有提高存活率的潜力。

DESCRIPTION (provided by applicant): Advances in conventional cancer therapy have not produced any significant improvement in the treatment of glioblastoma multiforme (GBM). Therefore, the further development of novel treatment modalities for GBM, such as boron neutron capture therapy (BNCT), remains a pressing task for the health science community in the USA. Subject of the present grant application is the continued development of 3-carboranyl thymidine analogues (3CTAs), a novel class of BNCT agents for the treatment of GBM. The mechanism of action of 3CTAs is primarily based on their ability to function as substrates of human thymidine kinase 1 (TK1), which is only active in proliferating cells. BNCT of tumor-bearing rodents that had received N5-2OH, the current lead compound of our 3CTA library, via intracerebral (i.c.) or intratumoral (i.t.) injection resulted in reduced tumor growth and prolonged survival times. On the other hand, the same studies have revealed two major limitations of N5-2OH and other 3CTAs. These are (1) the suboptimal competition with endogenous thymidine (Thd) at the substrate-binding site of TK1 and (2) the lack of water-solubility, which necessitated the use of organic solvents to solubilize 3CTAs for biological studies. In addition crucial biochemical and biological features of 3CTAs are still unknown. These are (3) the anabolism of 3CTAs beyond the monophosphorylation step, including their possible incorporation into DNA, and (4) the mechanisms that 3CTAs and their metabolites recruit to enter and exit cells. To address these shortcomings, the following SPECIFIC AIMS were developed: (1) To synthesize 3CTAs with improved ability to compete with Thd at the active site of TK1, to evaluate their substrate and inhibitory capacities in enzyme assays with TK1, and to determine their physicochemical properties, (2) to synthesize water-soluble amino acid prodrugs of N5-2OH and to evaluate their applicability for i.c. administration, (3) To study the metabolism of N5-2OH and 3CTAs with improved drug-like and enzymatic properties that emerged from Specific Aims 1 and 2 in vitro and in enzyme assays with nucleotide kinases and DNA polymerase, (4) to study the mechanisms of cellular influx and efflux of N5-2OH, 3CTAs with improved drug-like and enzymatic properties that emerged from Specific Aims 1 and 2, and their metabolites in vitro, and (5) to optimize parameters for i.c. administration of the 3CTA with the most improved drug-like and enzymatic properties that emerged from Specific Aims 1- 4 to RG2 glioma bearing rats and to determine possible neurotoxicity. PUBLIC HEALTH RELEVANCE: Novel boronated nucleosides will be developed for the treatment of brain tumors by boron neutron capture therapy (BNCT). BNCT is a binary treatment modality for cancer that relies both on a chemical and a radiation component. Brain tumors called glioblastoma multiforme are among the deadliest of all cancers. Advances in conventional cancer therapy have not produced any significant improvement in the treatment of these brain tumors. BNCT of these brain tumors with boronated nucleosides may have the potential to improve survival rates.