ABSTRACT
The human and veterinary disease complex known as African trypanosomiasis continues to inflict significant global morbidity, mortality, and economic hardship. Drug resistance and toxic side effects of old drugs call for novel and unorthodox strategies for new and safe treatment options. We designed methyltriazenyl purine prodrugs to be rapidly and selectively internalized by the parasite, after which they disintegrate into a nontoxic and naturally occurring purine nucleobase, a simple triazene-stabilizing group, and the active toxin: a methyldiazonium cation capable of damaging DNA by alkylation. We identified 2-(3-acetyl-3-methyltriazen-1-yl)-6-hydroxypurine (compound 1) as a new lead compound, which showed submicromolar potency against
Trypanosoma brucei
, with a selectivity index of >500, and it demonstrated a curative effect in animal models of acute trypanosomiasis. We investigated the mechanism of action of this lead compound and showed that this molecule has significantly higher affinity for parasites over mammalian nucleobase transporters, and it does not show cross-resistance with current first-line drugs. Once selectively accumulated inside the parasite, the prodrug releases a DNA-damaging methyldiazonium cation. We propose that ensuing futile cycles of attempted mismatch repair then lead to G
2
/M phase arrest and eventually cell death, as evidenced by the reduced efficacy of this purine analog against a mismatch repair-deficient (
MSH2
−/−
) trypanosome cell line. The observed absence of genotoxicity, hepatotoxicity, and cytotoxicity against mammalian cells revitalizes the idea of pursuing parasite-selective DNA alkylators as a safe chemotherapeutic option for the treatment of human and animal trypanosomiasis.
摘要
被称为非洲锥虫病的人类和兽医综合疾病继续在全球造成严重的发病率、死亡率和经济困难。旧药的耐药性和毒副作用要求我们采用新颖、非正统的策略来寻找新的安全治疗方案。我们设计的甲基三嗪基嘌呤原药可被寄生虫快速、选择性地内化,然后分解成一种无毒的天然嘌呤核碱基、一个简单的三嗪稳定基团和活性毒素:一种能通过烷基化破坏 DNA 的甲基二氮阳离子。我们发现了 2-(3-乙酰基-3-甲基三氮烯-1-基)-6-羟基嘌呤(化合物 1)作为一种新的先导化合物,该化合物对布氏锥虫的毒性为亚摩尔级。
布氏锥虫
在急性锥虫病动物模型中显示出治疗效果。我们对这种先导化合物的作用机制进行了研究,结果表明这种分子对寄生虫的亲和力明显高于哺乳动物核碱基转运体,而且不会与目前的一线药物产生交叉耐药性。一旦选择性地在寄生虫体内蓄积,该原药就会释放出破坏 DNA 的甲基偶氮阳离子。我们认为,随后尝试错配修复的徒劳循环会导致 G
2
/M期停滞,最终导致细胞死亡。
MSH2
-/-
)锥虫细胞系的疗效降低就证明了这一点。观察到这种嘌呤类似物对哺乳动物细胞没有遗传毒性、肝毒性和细胞毒性,这使我们重新燃起了将寄生虫选择性DNA烷化剂作为治疗人类和动物锥虫病的安全化疗选择的想法。