Identification of Cryptosporidium parvum Active Chemical Series by Repurposing the Open Access Malaria Box

The apicomplexan parasitesCryptosporidium parvum andCryptosporidium hominis are major etiologic agents of human cryptosporidiosis. The infection is typically self-limited in immunocompetent adults, but it can cause chronic fulminant diarrhea in immunocompromised patients and malnutrition and stunting in children. Nitazoxanide, the current standard of care for cryptosporidiosis, is only partially efficacious for children and is no more effective than a placebo for AIDS patients. Unfortunately, financial obstacles to drug discovery for diseases that disproportionately affect low-income countries and technical limitations associated with studies ofCryptosporidium biology impede the development of better drugs for treating cryptosporidiosis. Using a cell-based high-throughput screen, we queried the Medicines for Malaria Venture (MMV) Open Access Malaria Box for activity againstC. parvum . We identified 3 novel chemical series derived from the quinolin-8-ol, allopurinol-based, and 2,4-diamino-quinazoline chemical scaffolds that exhibited submicromolar potency againstC. parvum . Potency was conserved in a subset of compounds from each scaffold with varied physicochemical properties, and two of the scaffolds identified exhibit more rapid inhibition ofC. parvum growth than nitazoxanide, making them excellent candidates for further development. The 2,4-diamino-quinazoline and allopurinol-based compounds were also potent growth inhibitors of the related apicomplexan parasiteToxoplasma gondii , and a good correlation was observed in the relative activities of the compounds in the allopurinol-based series againstT. gondii andC. parvum . Taken together, these data illustrate the utility of the Open Access Malaria Box as a source of both potential leads for drug development and chemical probes to elucidate basic biological processes inC. parvum and other apicomplexan parasites.