Hay Michael P, Gamage Swarna A, Kovacs Mary S, Pruijn Frederik B, Anderson Robert F, Patterson Adam V, Wilson William R, Brown J Martin, Denny William A
Auckland Cancer Society Research Centre, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag 92019, Auckland, New Zealand.
J Med Chem. 2003 Jan 2;46(1):169-82. doi: 10.1021/jm020367+.
Tirapazamine (TPZ, 1,2,4-benzotriazin-3-amine 1,4-dioxide) is a bioreductive hypoxic cytotoxin currently in Phase II/III clinical trials in combination with radiotherapy and with cisplatin-based chemotherapy. As part of a program to develop TPZ analogues with improved solubility/potency and therapeutic indices, we synthesized 34 1,2,4-benzotriazin-3-amine 1,4-dioxides (BTO) to examine structure-activity relationships (SAR) for ring substitution. The electronic, hydrophobic, and steric parameters of substituents at the 5-, 6-, 7-, and 8-positions were systematically varied, and the aqueous solubility and one-electron reduction potentials [E(1)] of the analogues were determined. For each compound, we determined cell killing of mouse SCCVII tumor cells in vitro under aerobic and hypoxic conditions by clonogenic survival and determined their relative hypoxic toxicity (RHT; relative to TPZ) and hypoxic cytotoxicity ratio (HCR). A subset of compounds was independently evaluated using a 96-well SRB proliferation assay, the data from which correlated well with that derived by the clonogenic endpoint. Most substituents, except 5- and 8-dimethylamino and 8-diethylamino, gave analogues less soluble than TPZ. E(1) values ranged from -240 mV through -670 mV (with TPZ having a value of -456 mV) and correlated well with the electronic parameter sigma for substituents at the 5-, 6-, 7-, and 8-positions. Aerobic cytotoxic potency showed a strong positive correlation with E(1) (i.e., electron-withdrawing substituents increased aerobic toxicity). Hypoxic cytotoxicity also generally increased with increasing E(1), with a maximum (RHT up to 3.9-fold) seen in halo- and trifluoromethyl-substituted BTO derivatives having E(1) between ca. -370 to -400 mV. Analogues with high HCRs (>50) all had E(1)s in the range -450 to -510 mV (weakly electron-donating substituents) with the exception of the 8-CF(3) analogue, which had an HCR of 112 against SCCVII despite a high E(1) of -372 mV). The results suggest that ring-A substituents in BTO analogues can be used to predictably vary one-electron reduction potentials and also provide a much better definition than previously of the optimum range of these reduction potentials for a desirable biological activity profile (high HCR, RHT, and solubility).
替拉扎明（TPZ，1,2,4-苯并三嗪-3-胺1,4-二氧化物）是一种生物还原型低氧细胞毒素，目前正处于与放疗以及基于顺铂的化疗联合使用的II/III期临床试验阶段。作为开发具有改善的溶解度/效力和治疗指数的TPZ类似物计划的一部分，我们合成了34种1,2,4-苯并三嗪-3-胺1,4-二氧化物（BTO），以研究环取代的构效关系（SAR）。系统地改变了5-、6-、7-和8-位取代基的电子、疏水和空间参数，并测定了类似物的水溶性和单电子还原电位[E(1)]。对于每种化合物，我们通过克隆存活法测定了其在需氧和低氧条件下对小鼠SCCVII肿瘤细胞的体外杀伤作用，并确定了它们的相对低氧毒性（RHT；相对于TPZ）和低氧细胞毒性比（HCR）。使用96孔SRB增殖试验对一部分化合物进行了独立评估，其数据与通过克隆终点得出的数据相关性良好。除了5-和8-二甲基氨基以及8-二乙氨基外，大多数取代基得到的类似物的溶解度都低于TPZ。E(1)值范围为-240 mV至-670 mV（TPZ的值为-456 mV），并且与5-、6-、7-和8-位取代基的电子参数sigma相关性良好。需氧细胞毒性效力与E(1)呈强正相关（即吸电子取代基增加需氧毒性）。低氧细胞毒性通常也随着E(1)的增加而增加，在E(1)约为-370至-400 mV的卤代和三氟甲基取代的BTO衍生物中观察到最大值（RHT高达3.9倍）。具有高HCR（>50）的类似物的E(1)值均在-450至-510 mV范围内（弱供电子取代基），但8-CF(3)类似物除外，尽管其E(1)较高，为-372 mV，但对SCCVII的HCR为112。结果表明，BTO类似物中的A环取代基可用于可预测地改变单电子还原电位，并且比以前更好地定义了这些还原电位对于理想生物活性谱（高HCR、RHT和溶解度）的最佳范围。
