Research Centre for Infectious Diseases, School of Biological Sciences, The University of Adelaide, Adelaide, 5005, Australia.
Walter and Eliza Hall Institute of Medical Research, Melbourne, Victoria, 3050, Australia.
BMC Biol. 2020 Sep 29;18(1):133. doi: 10.1186/s12915-020-00859-4.
Resistance to front-line antimalarials (artemisinin combination therapies) is spreading, and development of new drug treatment strategies to rapidly kill Plasmodium spp. malaria parasites is urgently needed. Azithromycin is a clinically used macrolide antibiotic proposed as a partner drug for combination therapy in malaria, which has also been tested as monotherapy. However, its slow-killing 'delayed-death' activity against the parasite's apicoplast organelle and suboptimal activity as monotherapy limit its application as a potential malaria treatment. Here, we explore a panel of azithromycin analogues and demonstrate that chemical modifications can be used to greatly improve the speed and potency of antimalarial action.
Investigation of 84 azithromycin analogues revealed nanomolar quick-killing potency directed against the very earliest stage of parasite development within red blood cells. Indeed, the best analogue exhibited 1600-fold higher potency than azithromycin with less than 48 hrs treatment in vitro. Analogues were effective against zoonotic Plasmodium knowlesi malaria parasites and against both multi-drug and artemisinin-resistant Plasmodium falciparum lines. Metabolomic profiles of azithromycin analogue-treated parasites suggested activity in the parasite food vacuole and mitochondria were disrupted. Moreover, unlike the food vacuole-targeting drug chloroquine, azithromycin and analogues were active across blood-stage development, including merozoite invasion, suggesting that these macrolides have a multi-factorial mechanism of quick-killing activity. The positioning of functional groups added to azithromycin and its quick-killing analogues altered their activity against bacterial-like ribosomes but had minimal change on 'quick-killing' activity. Apicoplast minus parasites remained susceptible to both azithromycin and its analogues, further demonstrating that quick-killing is independent of apicoplast-targeting, delayed-death activity.
We show that azithromycin and analogues can rapidly kill malaria parasite asexual blood stages via a fast action mechanism. Development of azithromycin and analogues as antimalarials offers the possibility of targeting parasites through both a quick-killing and delayed-death mechanism of action in a single, multifactorial chemotype.
一线抗疟药物（青蒿素联合疗法）的耐药性正在蔓延，急需开发新的药物治疗策略来快速杀死疟原虫。阿奇霉素是一种临床使用的大环内酯类抗生素，被提议作为疟疾联合治疗的联合用药，也已作为单药进行了测试。然而，其对寄生虫类质体细胞器的缓慢杀伤“迟亡”活性和作为单药的不佳活性限制了其作为潜在抗疟药物的应用。在这里，我们探索了一组阿奇霉素类似物，并证明可以通过化学修饰来大大提高抗疟作用的速度和效力。
对 84 种阿奇霉素类似物的研究表明，针对红细胞内寄生虫发育的最早阶段，具有纳米摩尔级的快速杀伤效力。事实上，最好的类似物在体外治疗不到 48 小时的情况下，其效力比阿奇霉素高出 1600 倍。类似物对动物源性疟原虫 knowlesi 疟疾寄生虫有效，对多药和青蒿素耐药的恶性疟原虫系也有效。阿奇霉素类似物处理的寄生虫代谢组学图谱表明，其在寄生虫食物泡和线粒体中的活性受到干扰。此外，与靶向食物泡的药物氯喹不同，阿奇霉素及其类似物在整个血期发育过程中都具有活性，包括裂殖体入侵，这表明这些大环内酯类药物具有快速杀伤活性的多因素机制。添加到阿奇霉素及其类似物中的功能基团的定位改变了它们对细菌样核糖体的活性，但对“快速杀伤”活性的影响最小。缺乏类质体的寄生虫仍然对阿奇霉素及其类似物敏感，进一步证明快速杀伤与类质体靶向、迟亡活性无关。
我们表明，阿奇霉素及其类似物可通过快速作用机制迅速杀死疟原虫无性血期。阿奇霉素及其类似物的开发为通过单一的、多因素化学型在寄生虫中靶向快速杀伤和迟亡作用机制提供了可能。
