Table_1_NPC1161B, an 8-Aminoquinoline Analog, Is Metabolized in the Mosquito and Inhibits Plasmodium falciparum Oocyst Maturation.docx

Malaria is a major global health threat, with nearly half the world’s population at risk of infection. Given the recently described delayed clearance of parasites by artemisinin-combined therapies, new antimalarials are needed to facilitate the global effort toward elimination and eradication. NPC1161 is an 8-aminoquinoline that is derived from primaquine with an improved therapeutic profile compared to the parent compound. The (R)-(−) enantiomer (NPC1161B) has a lower effective dose that results in decreased toxic side effects such as hemolysis compared to the (S)-(+)-enantiomer, making it a promising compound for consideration for clinical development. We explored the effect of NPC1161B on Plasmodium falciparum oocyst and sporozoite development to evaluate its potential transmission-blocking activity viz. its ability to cure mosquitoes of an ongoing infection. When mosquitoes were fed NPC1161B 4 days after P. falciparum infection, we observed that total oocyst numbers were not affected by NPC1161B treatment. However, the sporozoite production capacity of the oocysts was impaired, and salivary gland sporozoite infections were completely blocked, rendering the mosquitoes non-infectious. Importantly, NPC1161B did not require prior liver metabolism for its efficacy as is required in mammalian systems, suggesting that an alternative metabolite is produced in the mosquito that is active against the parasite. We performed liquid chromatography–mass spectrometry (LC-MS)/MS analysis of methanol extracts from the midguts of mosquitoes fed on an NPC1161B (434.15 m/z)-treated blood meal and identified a compound with a mass of 520.2 m/z, likely a conjugate of NPC1161B or an oxidized metabolite. These findings establish NPC1161B, and potentially its metabolites, as transmission-blocking candidates for the treatment of P. falciparum.

疟疾是全球主要的公共卫生威胁，全球近半数人口面临感染风险。鉴于近期报道的青蒿素联合疗法导致的寄生虫清除延迟，为了促进全球消除和根除疟疾的努力，迫切需要新的抗疟药物。NPC1161是一种从伯氨喹啉衍生的8-氨基喹啉，其治疗效果优于母体化合物。其中，(R)-(−)异构体（NPC1161B）的有效剂量较低，相对于(S)-(+)-异构体，可减少如溶血等毒副作用，使其成为临床开发的潜在候选药物。本研究探讨了NPC1161B对恶性疟原虫子孢子体和裂殖体发育的影响，以评估其潜在的传播阻断活性，即其治愈蚊子现有感染的能力。当蚊子在感染恶性疟原虫4天后摄入NPC1161B时，观察到总子孢子体数量未受NPC1161B治疗的影响。然而，子孢子体的产生能力受到损害，唾液腺中的子孢子体感染被完全阻断，使蚊子失去传染性。重要的是，NPC1161B不需要像哺乳动物系统中的那样经过肝脏代谢即可发挥其疗效，这表明蚊子可能产生了一种对寄生虫具有活性的替代代谢物。我们对摄入含有NPC1161B（434.15 m/z）处理的血液餐的蚊子的中肠甲醇提取物进行了液相色谱-质谱联用（LC-MS）/MS分析，并鉴定出一种质量为520.2 m/z的化合物，可能是NPC1161B的共轭物或氧化代谢物。这些发现将NPC1161B及其潜在的代谢物确立为治疗恶性疟原虫的传播阻断候选药物。