Anti-Cryptosporidium efficacy of BKI-1708, an inhibitor of Cryptosporidium calcium-dependent protein kinase 1

Cryptosporidiosis is a diarrheal disease caused by the parasite Cryptosporidium. Symptoms can be long-lasting and severe, particularly in malnourished children and immunocompromised people, leading to prolonged gut inflammation, wasting, and chronic infections. Unfortunately, the sole treatment on the market appears to be effective only in people with healthy immune systems. Hence, there is an urgent need for a new and safe drug that works in all patients, one that offers rapid relief from diarrhoea and leads to a cure. In this study, we show that a promising drug candidate, BKI-1708, when administered at a low dose in mouse and newborn calf models of Cryptosporidium infection, leads to significant reduction in parasite levels in stool. In calves, BKI-1708 quickly resolves diarrhoea and leads to improved clinical outcomes. We show BKI-1708 is processed in the liver to form a metabolite that is still potent against Cryptosporidium. In mice this metabolite remains in the body for a longer time, extending BKI-1708’s therapeutic potential. Finally, we demonstrate BKI-1708 is well-tolerated at high concentrations in rats and dogs, which considering its substantial efficacy at low concentrations, offers a very promising safety margin during treatment. Thus, our results support further clinical development of BKI-1708 for treatment of human cryptosporidiosis.

Keywords: Q3 2025