Hybrid Molecules From Benzylguanidine and Cytotoxic Drugs (Busulfan, Melphalan, Thiotepa) for Specific Therapy of Neuroblastoma

在世界范围内，~(123)I标记的间碘苯甲基胍([~(123)I]-MIBG)被用于神经母细胞瘤的放射性核素诊断。同位素[~(131)I]-MIBG是相同疾病的常规治疗方法。这些都是海德堡和图宾根神经母细胞瘤首次临床成功(1984年独立和同时)的后续发展的顶峰。有趣的是，非放射性的[127I]-MIBG也显示出抗神经母细胞瘤的活性(MYC相关的肿瘤特异性葡萄糖代谢起着重要作用)。对位异构体[127I]-pIBG也显示出同样的活性，但它在体内的快速脱碘阻碍了它的临床应用。这项临床和合成研究的联合项目计划赋予MIBG和pIBG的类似物治疗神经母细胞瘤的潜力，这将是第一次无碘的MIBG和pIBG。我们将这些类似物设计为去碘IBG支架和相关细胞抑制剂的烷化部分的杂交结构。结构动机(BG)将允许我们的类似物(BG候选药物)通过去甲肾上腺素转运体进入神经母细胞瘤细胞。烷基化部分的灵感来自于丁硫丹、梅尔法兰和硫代替巴。之所以选择白花丹和马法兰，是因为它们在神经母细胞瘤干细胞移植前的预适应方面优于其他细胞抑制药物。因此，可以预期它们的结合可以确保适当的细胞毒性。我们为期3年的合作研究计划的目标是利用这种设计在这种假定的抗神经母细胞瘤化合物中将细胞选择性与细胞毒性配对。弗莱堡将合成42个BG候选药物及其6个[14C]标记的同位素。这一工作量是现实的，因为我们史无前例地从任何目标分子中消除了碘：这将步骤要求减少了50%。Tübingen将测试所有BG候选药物。基本筛查将包括增殖/活力研究以及与白花丹、马法兰、硫代替巴和未标记的MIBG的比较。此外，细胞培养分析将揭示这些化合物被神经母细胞瘤细胞摄取的机制和程度，以及它们是否导致线粒体积聚。BG候选药物对神经母细胞瘤细胞代谢的影响应在高级筛查开始时进行分析。一个焦点将是肿瘤(神经母细胞瘤)特定的葡萄糖代谢(Warburg效应)，包括BG对N-myc表达的影响。另一个焦点将是烷基化部分对DNA的损伤。在我们研究的这一点上，最有希望的BG候选药物将使用神经母细胞瘤球体模型进行分析。将在神经母细胞瘤小鼠模型上测试更有限的化合物选择，以确定最合适的BG候选药物(S)，用于人类患者的潜在应用。

Around the world, iodine-123 labeled meta-iodobenzylguanidine ([123I]-mIBG) is used for the scintigraphic diagnosis of neuroblastoma. The isotopologe [131I]-mIBG is a routine therapeutical for the same disease. These are culmination points of developments in the sequel of the first respective clinical successes with neuroblastoma in Heidelberg and Tübingen (independent and simultaneous in 1984). Interestingly, non-radioactive [127I]-mIBG reveals anti-neuroblastoma activity, too (and the MYC-associated tumor-specific glucose metabolism plays an important role). The same activity would be exhibited by the para isomer [127I]-pIBG, but its rapid deiodination in the body prevents its clinical application. This joint project of a clinical and a synthetic research plans to endow analogs of mIBG und pIBG, which shall be iodine-free for the first time, with a therapeutic potential for neuroblastoma.We design these analogs as hybrid structures of the iodine-deprived IBG scaffold and of the alkylating moieties of pertinent cytostatics. The structural motive benzylguanidine (BG) shall allow our analogs (BG-drug candidates) to enter neuroblastoma cells via the noradrenalin transporter. The alkylating moieties are inspired by busulfan, mel¬phalanx, and thiotepa. Busulfan and melphalan were selected specifically because they are superior to other cytostatic drugs in conditioning before stem-cell transplantation in neuroblastoma. Accordingly, it may be expected that their incorporation assures an appropriate cytotoxicity. The goal of our 3-year collaborative research plan is to use this design for pairing cell selectivity with cell toxicity in such putative anti-neuroblastoma compounds. Freiburg will synthesize 42 BG-drug candidates and 6 [14C]-labeled isotopologs thereof. This volume of work is realistic due to our unprecedented concept of abolishing iodine from whatever target molecule: this reduces the step requirement by 50%. Tübingen will test all BG-drug candidates. A basic screening will include proliferation/vitality studies and comparisons with busulfan, melphalan, thiotepa, and unlabeled mIBG. Moreover, cell culture assays shall reveal, by which mechanism and to which extent these compounds are taken up by neuroblastoma cells and whether they cause an accumulation in mitochondria. The impact of BG-drug candidates on the metabolism of neuroblastoma cells shall be analyzed at the beginning of an advanced screening. One focus will be on the tumor (neuroblastoma) specific glucose metabolism (Warburg effect) including BG effects on N-myc expression. Another focus will be on DNA damage by the alkylating moieties. The most promising BG-drug candidates at this point of our study shall be analyzed using a neuroblastoma spheroid model. A still more restricted selection of compounds shall be tested on a neuroblastoma-bearing mouse model for identifying the most suitable BG-drug candidate(s) for a potential application in human patients.