Department of Medicine, University of Vermont Larner College of Medicine, Room 202 Stafford Hall, 95 Carrigan Drive, Burlington, Vermont, USA.
Department of Chemistry, Saint Louis University, Room 206 Monsanto Hall, 3501 Laclede Avenue, Saint Louis, MO, USA.
Nat Commun. 2024 Sep 27;15(1):8272. doi: 10.1038/s41467-024-52658-y.
Cryptosporidium parvum and C. hominis are parasites that cause life-threatening diarrhea in children and immunocompromised people. There is only one approved treatment that is modestly effective for children and ineffective for AIDS patients. Here, screening 278 compounds from the Merck KGaA, Darmstadt, Germany collection and accelerated follow-up enabled by prior investigation of the compounds identifies a series of pyrazolopyrimidine human phosphodiesterase (PDE)-V (hPDE-V) inhibitors with potent anticryptosporidial activity and efficacy following oral administration in C. parvum-infected male mice. The lead compounds affect parasite host cell egress, inhibit both C. parvum and C. hominis, work rapidly, and have minimal off-target effects in a safety screening panel. Interestingly, the hPDE-V inhibitors sildenafil and the 4-aminoquinoline compound 7a do not affect Cryptosporidium. C. parvum expresses one PDE (CpPDE1) continuously during asexual growth, the inhibited life stage. According to homology modeling and docking, the lead compounds interact with CpPDE1. Bulkier amino acids (Val900 and His884) in the CpPDE1 active site replace alanines in hPDE-V and block sildenafil binding. Supporting this, sildenafil kills a CRISPR-engineered Cryptosporidium CpPDE1 V900A mutant. The CpPDE1 mutation also alters parasite susceptibility to pyrazolopyrimidines. CpPDE1 is therefore a validated pyrazolopyrimidine molecular target to exploit for target-based optimization for improved anticryptosporidial development.
微小隐孢子虫和人隐孢子虫是寄生虫，会导致儿童和免疫功能低下者发生危及生命的腹泻。目前仅有一种经批准的治疗方法，对儿童的疗效适度，对艾滋病患者无效。在此，通过对德国达姆施塔特默克公司（Merck KGaA, Darmstadt, Germany）的 278 种化合物进行筛选，并对化合物进行了预先研究，以加速后续工作，从而确定了一系列吡唑并嘧啶类人磷酸二酯酶（PDE）-V（hPDE-V）抑制剂，对感染微小隐孢子虫的雄性小鼠口服给药后具有很强的抗隐孢子虫活性和疗效。这些先导化合物会影响寄生虫-宿主细胞逸出，能抑制微小隐孢子虫和人隐孢子虫，起效迅速，在安全性筛选中仅有最小的脱靶效应。有趣的是，hPDE-V 抑制剂西地那非和 4-氨基喹啉化合物 7a 对隐孢子虫没有影响。微小隐孢子虫在无性生殖过程中持续表达一种 PDE（CpPDE1），这是被抑制的生命阶段。根据同源建模和对接，先导化合物与 CpPDE1 相互作用。CpPDE1 活性位点较大的氨基酸（Val900 和 His884）取代了 hPDE-V 中的丙氨酸，从而阻断了西地那非的结合。支持这一观点的是，西地那非杀死了经 CRISPR 工程改造的微小隐孢子虫 CpPDE1 V900A 突变体。该 CpPDE1 突变还改变了寄生虫对吡唑并嘧啶类化合物的敏感性。因此，CpPDE1 是一个经验证的吡唑并嘧啶类分子靶点，可用于基于靶点的优化，以改善抗隐孢子虫药物的开发。
