Calibr Cryptosporidium panel screens.

BackgroundDiarrheal pathogens, such as Cryptosporidium, impose a heavy burden of disease in resource-limited regions. Cryptosporidiosis often causes chronic infection in immunocompromised people and gastrointestinal injury in malnourished children, leading to wasting, stunting, and cognitive impairment. Current treatment for cryptosporidiosis fails in these vulnerable populations, highlighting the need for new medicines. Here we describe the anti-Cryptosporidium efficacy, pharmacokinetics, and safety of a bumped kinase inhibitor BKI-1708. BKI-1708 inhibits the essential molecular target, calcium-dependent protein kinase 1 (CDPK1), which is highly expressed in the major proliferative stages of the parasite life cycle.Methods and FindingsEfficacy was demonstrated in the Cryptosporidium parvum IFNγ-KO mouse infection and calf diarrhea models. Dose response in the mouse model demonstrated oral doses as low as 15 mg/kg administered daily for 3 days completely suppressed oocyst shedding. Metabolite profiling in pre-clinical species and human hepatocytes identified an active metabolite, M2, which retains sub-micromolar activity against C. parvum. Pharmacokinetic analysis of BKI-1708 and M2 in mice demonstrates good systemic exposure, important for treating biliary and upper respiratory infections in some cases of cryptosporidiosis. In mice, M2 reaches 7-fold and >3-fold higher levels over BKI-1708 in plasma and the gastrointestinal tract, respectively. Oral administration of M2 completely suppressed oocyst shedding in the mouse model at doses as low as 8 mg/kg for 3 days. Wide safety margins are demonstrated in mice, rats, and dogs.ConclusionsBKI-1708 has characteristics of a safe and effective drug for treating Cryptosporidium infections in animal models and shows promise for use in humans. Moreover, BKI-1708 and M2 formed in vivo, offer an attractive prospect of a dually active preclinical candidate for the treatment of cryptosporidiosis.背景 隐孢子虫（Cryptosporidium）这类腹泻致病菌在资源匮乏地区造成了沉重的疾病负担。隐孢子虫病常使免疫功能低下人群罹患慢性感染，并导致营养不良儿童出现胃肠道损伤，进而引发消瘦、发育迟缓与认知功能受损。当前针对隐孢子虫病的现有治疗方案在这类脆弱人群中疗效不佳，凸显了开发新型治疗药物的迫切需求。本研究报道了凸位激酶抑制剂（bumped kinase inhibitor）BKI-1708的抗隐孢子虫活性、药代动力学特征与安全性。BKI-1708可靶向抑制寄生虫生命周期主要增殖阶段高表达的必需分子靶点——钙依赖性蛋白激酶1（CDPK1）。 方法与研究结果 研究在小隐孢子虫（Cryptosporidium parvum）干扰素γ基因敲除（IFNγ-KO）小鼠感染模型与犊牛腹泻模型中验证了BKI-1708的抗虫活性。小鼠模型中的剂量反应实验显示，每日口服给药15 mg/kg、连续给药3天即可完全抑制卵囊排出。通过对临床前物种及人类肝细胞开展代谢物谱分析，鉴定得到活性代谢产物M2，其对小隐孢子虫仍保有亚微摩尔级的抑制活性。针对BKI-1708与M2的小鼠药代动力学分析表明，二者均具备良好的全身暴露量，这对部分隐孢子虫病患者的胆道与上呼吸道感染治疗至关重要。在小鼠体内，血浆与胃肠道中的M2浓度分别较BKI-1708高出7倍与3倍以上。以每日8 mg/kg的剂量口服给予M2、连续给药3天，即可完全抑制小鼠模型中的卵囊排出。在小鼠、大鼠与犬类实验中均证实BKI-1708具备宽泛的安全边际。 结论 在动物模型中，BKI-1708具备安全且有效的抗隐孢子虫感染药物特性，展现出用于人类治疗的潜力。此外，BKI-1708及其体内生成的代谢产物M2均具备抗隐孢子虫活性，为隐孢子虫病的治疗提供了一类极具吸引力的双重活性临床前候选药物。