ABSTRACT
Hematotoxicity in individuals genetically deficient in glucose-6-phosphate dehydrogenase (G6PD) activity is the major limitation of primaquine (PQ), the only antimalarial drug in clinical use for treatment of relapsing
Plasmodium vivax
malaria. PQ is currently clinically used in its racemic form. A scalable procedure was developed to resolve racemic PQ, thus providing pure enantiomers for the first time for detailed preclinical evaluation and potentially for clinical use. These enantiomers were compared for antiparasitic activity using several mouse models and also for general and hematological toxicities in mice and dogs. (+)-(
S
)-PQ showed better suppressive and causal prophylactic activity than (−)-(
R
)-PQ in mice infected with
Plasmodium berghei
. Similarly, (+)-(
S
)-PQ was a more potent suppressive agent than (−)-(
R
)-PQ in a mouse model of
Pneumocystis carinii
pneumonia. However, at higher doses, (+)-(
S
)-PQ also showed more systemic toxicity for mice. In beagle dogs, (+)-(
S
)-PQ caused more methemoglobinemia and was toxic at 5 mg/kg of body weight/day given orally for 3 days, while (−)-(
R
)-PQ was well tolerated. In a novel mouse model of hemolytic anemia associated with human G6PD deficiency, it was also demonstrated that (−)-(
R
)-PQ was less hemolytic than (+)-(
S
)-PQ for the G6PD-deficient human red cells engrafted in the NOD-SCID mice. All these data suggest that while (+)-(
S
)-PQ shows greater potency in terms of antiparasitic efficacy in rodents, it is also more hematotoxic than (−)-(
R
)-PQ in mice and dogs. Activity and toxicity differences of PQ enantiomers in different species can be attributed to their different pharmacokinetic and metabolic profiles. Taken together, these studies suggest that (−)-(
R
)-PQ may have a better safety margin than the racemate in human.
摘要
葡萄糖-6-磷酸脱氢酶(G6PD)活性基因缺陷者的血液毒性是伯氨喹(PQ)的主要局限性。
间日疟原虫
疟疾的唯一抗疟药物。目前临床上使用的是外消旋体形式的 PQ。我们开发了一种可扩展的程序来解析外消旋 PQ,从而首次提供了纯对映体,用于详细的临床前评估,并有可能用于临床。利用几种小鼠模型对这些对映体的抗寄生虫活性进行了比较,同时还对小鼠和狗的一般毒性和血液学毒性进行了比较。
S
)-PQ比(-)-( R)-PQ显示出更好的抑制和因果预防活性。
R
)-PQ对感染了
疟原虫
.同样,(+)-(
S
)-PQ比(-)-(
R
)-PQ更有效。
卡氏肺囊虫
肺炎的小鼠模型中,(+)-( R )-PQ然而,在较高剂量下,(+)-(
S
)-PQ对小鼠也显示出更大的全身毒性。在小猎犬中,(+)-(
S
)-PQ会导致更多高铁血红蛋白血症,按每公斤体重每天5毫克的剂量口服3天会产生毒性,而(-)-( R )-PQ会导致更多高铁血红蛋白血症。
R
)-PQ 的耐受性良好。在一个与人类 G6PD 缺乏症相关的溶血性贫血的新型小鼠模型中,也证明了 (-)-(
R
)-PQ的溶血性低于(+)-(
S
)-PQ对接种到NOD-SCID小鼠体内的G6PD缺陷人红细胞的溶血作用更小。所有这些数据都表明,虽然(+)-(
S
)-PQ在啮齿类动物中显示出更强的抗寄生虫效力,但它的血液毒性也比(-)-( S )-PQ更强。
R
)-PQ对小鼠和狗的血液毒性更大。PQ 对映异构体在不同物种中的活性和毒性差异可归因于它们不同的药代动力学和代谢特征。综上所述,这些研究表明,(-)-(
R
)-PQ在人体中可能比外消旋体具有更好的安全系数。