Cystoisosporosis is a leading diarrheal disease in suckling piglets. With the confirmation of resistance against the only available drug toltrazuril, there is a substantial need for novel therapeutics to combat the infection and its negative effects on animal health. In closely related apicomplexan species, bumped kinase inhibitors (BKIs) targeting calcium-dependent protein kinase 1 (CDPK1) were shown to be effective in inhibiting host-cell invasion and parasite growth. Therefore, the gene coding for Cystoisospora suis CDPK1 (CsCDPK1) was identified and cloned to investigate activity and thermal stabilization of the recombinant CsCDPK1 enzyme by BKI 1369. In this comprehensive study, the efficacy, safety and pharmacokinetics of BKI 1369 in piglets experimentally infected with Cystoisospora suis (toltrazuril-sensitive, Wien-I and toltrazuril-resistant, Holland-I strains) were determined in vivo and in vitro using an established animal infection model and cell culture, respectively. BKI 1369 inhibited merozoite proliferation in intestinal porcine epithelial cells-1 (IPEC-1) by at least 50% at a concentration of 40 nM, and proliferation was almost completely inhibited (>95%) at 200 nM. Nonetheless, exposure of infected cultures to 200 nM BKI 1369 for five days did not induce structural alterations in surviving merozoites as confirmed by transmission electron microscopy. Five-day treatment with BKI 1369 (10 mg/kg BW twice a day) effectively suppressed oocyst excretion and diarrhea and improved body weight gains in treated piglets without obvious side effects for both toltrazuril-sensitive, Wien-I and resistant, Holland-I C. suis strains. The plasma concentration of BKI 1369 in piglets increased to 11.7 μM during treatment, suggesting constant drug accumulation and exposure of parasites to the drug. Therefore, oral applications of BKI 1369 could potentially be a therapeutic alternative against porcine cystoisosporosis. For use in pigs, future studies on BKI 1369 should be directed towards ease of drug handling and minimizing treatment frequencies.

中文翻译：

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颠簸激酶抑制剂1369在体内和体外均有效地抵抗猪圆孢菌。

胞质孢子虫病是乳猪的主要腹泻病。随着对唯一可用药物托他脲的耐药性的确认，迫切需要新的疗法来对抗感染及其对动物健康的负面影响。在密切相关的apicomplexan物种中，针对钙依赖蛋白激酶1（CDPK1）的突触激酶抑制剂（BKI）已显示在抑制宿主细胞入侵和寄生虫生长方面有效。因此，鉴定并克隆了编码猪Cystoisospora suis CDPK1（CsCDPK1）的基因，以研究BKI 1369对重组CsCDPK1酶的活性和热稳定性。在这项全面的研究中，BKI 1369在经实验感染的仔猪中的功效，安全性和药代动力学猪Cystoisospora suis（对托曲脲敏感，使用已建立的动物感染模型和细胞培养分别在体内和体外测定Wien-I和耐托曲唑的Tollrazuril抗性（I）。在浓度为40 nM时，BKI 1369在肠猪上皮细胞1（IPEC-1）中抑制裂殖子增殖至少50％，而在200 nM时，增殖几乎被完全抑制（> 95％）。尽管如此，如通过透射电子显微镜所证实的，将感染的培养物暴露于200 nM BKI 1369中五天并没有诱导存活的裂殖子中的结构改变。BKI 1369（每天两次，每次10 mg / kg体重）五天治疗有效抑制了经处理的仔猪的卵囊排泄和腹泻，并改善了体重增加，而对曲妥瑞环敏感的Wien-I和耐药的Holland-I均无明显副作用猪油杆菌菌株。在治疗过程中，仔猪中BKI 1369的血浆浓度增加到11.7μM，这表明药物不断蓄积并且寄生虫暴露于药物中。因此，BKI 1369的口服应用可能是对抗猪囊状孢子虫病的治疗选择。为了在猪中使用，对BKI 1369的未来研究应针对简化药物处理并最大程度地减少治疗频率。