Diminazene aceturate (DA) and imidocarb dipropionate are commonly used in livestock as antipiroplasm agents. However, toxic side effects are common in animals treated with these two drugs. Therefore, evaluations of novel therapeutic agents with high efficacy against piroplasm parasites and low toxicity to host animals are of paramount importance. In this study, the 400 compounds in the Pathogen Box provided by the Medicines for Malaria Venture foundation were screened against Babesia bovis, Babesia bigemina, Babesia caballi, and Theileria equi. A fluorescence-based method using SYBR Green 1 stain was used for initial in vitro screening and determination of the half maximal inhibitory concentration (IC50). The initial in vitro screening performed using a 1 μM concentration as baseline revealed nine effective compounds against four tested parasites. Two "hit" compounds, namely MMV021057 and MMV675968, that showed IC50 < 0.3 μM and a selectivity index (SI)> 100 were selected. The IC50s of MMV021057 and MMV675968 against B. bovis, B. bigemina, T. equi and B. caballi were 23, 39, 229, and 146 nM, and 2.9, 3, 25.7, and 2.9 nM, respectively. In addition, a combination of MMV021057 and DA showed additive or synergistic effects against four tested parasites, while combinations of MMV021057 with MMV675968 and of MMV675968 with DA showed antagonistic effects. In mice, treated with 50 mg/kg MMV021057 and 25 mg/kg MMV675968 inhibited the growth of Babesia microti by 54 and 64%, respectively, as compared to the untreated group on day 8. Interestingly, a combination treatment with 6.25 mg/kg DA and 25 mg/kg MMV021057 inhibited B. microti by 91.6%, which was a stronger inhibition than that by single treatments with 50 mg/kg MMV021057 and 25 mg/kg DA, which showed 54 and 83% inhibition, respectively. Our findings indicated that MMV021057, MMV675968, and the combination treatment with MMV021057 and DA are prospects for further development of antipiroplasm drugs.

中文翻译：

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筛选抗疟原虫寄生虫的药物。

醋酸地米那嗪（DA）和亚氨基甲酸二丙酯通常在牲畜中用作抗质子体剂。但是，在用这两种药物治疗的动物中，毒副作用是常见的。因此，对新型高效抗疟原虫和对宿主动物毒性低的治疗剂的评估至关重要。在这项研究中，针对疟疾巴贝斯牛，大贝贝斯贝米虫，巴贝斯贝卡虫和马鞭草（Theileria equi）对疟疾药物基金会提供的病原体盒中的400种化合物进行了筛选。使用SYBR Green 1染色剂的基于荧光的方法用于初始体外筛选和最大半数抑制浓度（IC50）的确定。使用1μM浓度作为基线进行的初始体外筛选显示，针对9种被测寄生虫，共有9种有效化合物。选择IC50 <0.3μM和选择性指数（SI）> 100的两种“命中”化合物，即MMV021057和MMV675968。MMV021057和MMV675968对B. bovis，B。bigemina，T。equi和B. caballi的IC50分别为23、39、229和146 nM，以及2.9、3、25.7和2.9 nM。此外，MMV021057和DA的组合显示出对四种测试寄生虫的累加或协同作用，而MMV021057和MMV675968以及MMV675968和DA组合显示出拮抗作用。与第8天的未治疗组相比，用50 mg / kg MMV021057和25 mg / kg MMV675968处理的小鼠分别抑制了小肠贝贝菌的生长，分别为54％和64％。 DA和25 mg / kg MMV021057抑制B. microti达91.6％，与单次用50 mg / kg MMV021057和25 mg / kg DA的单次治疗相比，抑制作用更强，分别显示54％和83％的抑制作用。我们的发现表明，MMV021057，MMV675968以及与MMV021057和DA的联合治疗有望进一步开发抗螺胞质药物。