Substrate-analogous inhibitors exert antimalarial action by targeting the <i>Plasmodium</i> lactate transporter PfFNT at nanomolar scale

Resistance against all available antimalarial drugs calls for novel compounds that hit unexploited targets in the parasite. Here, we show that the recently discovered Plasmodium falciparum lactate/proton symporter, PfFNT, is a valid druggable target, and describe a new class of fluoroalkyl vinylogous acids that potently block PfFNT and kill cultured parasites. The original compound, MMV007839, is derived from the malaria box collection of potent antimalarials with unknown targets and contains a unique internal prodrug principle that reversibly switches between a lipophilic transport form and a polar, substrate-analogous active form. Resistance selection of cultured P. falciparum parasites with sub-lethal concentrations of MMV007839 produced a single nucleotide exchange in the PfFNT gene; this, and functional characterization of the resulting PfFNT G107S validated PfFNT as a novel antimalarial target. From quantitative structure function relations we established the compound binding mode and the pharmacophore. The pharmacophore largely circumvents the resistance mutation and provides the basis for a medicinal chemistry program that targets lactate and proton transport as a new mode of antimalarial action.当前所有临床可用抗疟药物均已产生耐药性，亟需开发靶向疟原虫未被发掘靶点的新型化合物。本研究证实，近期发现的恶性疟原虫乳酸/质子同向转运体（Plasmodium falciparum lactate/proton symporter, PfFNT）是一个可靠的可药用靶点，并报道了一类新型氟烷基插烯酸（fluoroalkyl vinylogous acids），该类化合物可强效抑制PfFNT活性，并杀死体外培养的恶性疟原虫。本研究中的原始化合物MMV007839源自靶向未知靶点的强效抗疟剂疟疾盒化合物库（Malaria Box），其具备独特的内置前药设计原理，可在脂溶性转运形式与极性底物类似物活性形式之间可逆切换。通过使用亚致死浓度的MMV007839对体外培养的恶性疟原虫进行耐药株筛选，我们在PfFNT基因中发现了一处单核苷酸替换；结合该G107S突变型PfFNT的功能表征实验，证实PfFNT是一个全新的抗疟靶点。通过定量结构-功能关联分析，我们明确了该化合物的结合模式与药效团（pharmacophore）。该药效团可有效规避该耐药突变，为以乳酸-质子转运为全新抗疟作用机制的药物化学研发项目奠定了坚实基础。