Boronated nucleosides for neutron capture therapy of brain tumors

描述（由申请人提供）：传统癌症治疗的进展尚未对多形性胶质母细胞瘤（GBM）的治疗产生任何显著改善。因此，进一步开发新的治疗GBM的方式，如硼中子捕获疗法（BNCT），仍然是美国健康科学界的一项紧迫任务。本资助申请的主题是继续开发3-碳硼烷胸苷类似物（3CTA），这是一类用于治疗GBM的新型BNCT药物。3CTA的作用机制主要基于其作为人胸苷激酶1（TK 1）底物的能力，TK 1仅在增殖细胞中有活性。通过脑内（i.c.）或瘤内（i.t.）注射导致减少的肿瘤生长和延长的存活时间。另一方面，相同的研究揭示了N5- 2 OH和其他3CTA的两个主要局限性。这些是（1）在TK 1的底物结合位点与内源性胸苷（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征仍然未知。这些是（3）3CTA的单磷酸化步骤之外的抑制，包括它们可能掺入DNA，和（4）3CTA及其代谢物招募进入和离开细胞的机制。为了克服这些缺点，开发了以下具体目标：（1）合成在TK 1的活性位点上与Thd竞争的具有改进能力的3个CTA，在TK 1的酶测定中评估它们的底物和抑制能力，并确定它们的理化性质;（2）合成N5- 2 OH的水溶性氨基酸前药，并评估它们在i. c.（3）在体外以及在使用核苷酸激酶和DNA聚合酶的酶试验中研究特定目的1和2产生的具有改善的药物样和酶性质的N5- 2 OH和3CTA的代谢，（4）研究特定目的1和2产生的具有改善的药物样和酶性质的N5- 2 OH，3CTA的细胞流入和流出机制，及其体外代谢产物;（5）优化i.c.将从特异性目的1- 4中出现的具有最改善的药物样和酶性质的3CTA施用至携带RG 2神经胶质瘤的大鼠，并确定可能的神经毒性。公共卫生相关性：将开发新型硼化核苷，用于硼中子捕获疗法（BNCT）治疗脑肿瘤。BNCT是癌症的二元治疗模式，依赖于化学和放射成分。被称为多形性胶质母细胞瘤的脑肿瘤是所有癌症中最致命的。传统癌症治疗的进展并没有对这些脑肿瘤的治疗产生任何显着的改善。这些脑肿瘤的硼化核苷BNCT可能有潜力提高生存率。

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.