Systemic and gastrointestinal targeted CDPK1 inhibitors for cryptosporidiosis - ABSTRACT Cryptosporidium species, including C. hominis and C. parvum, are protozoan parasites that present a significant health threat, particularly to young children and immunocompromised adults. These organisms have the potential to be deliberately introduced into the water supply, making them a CDC class B bioterrorism agent. Current treatment options for Cryptosporidium infections are very limited to one FDA-approved drug that is not effective in young children and immunocompromised adults. In addition, vaccines are unavailable. Calcium dependent protein kinase 1 (CDPK1) has emerged as a promising target for treating cryptosporidiosis, since silencing this protein significantly reduces parasite survival. Consequently, selective CDPK1 inhibitors that can efficiently access the gastrointestinal (GI) system, where parasites reside, will provide an effective strategy for the treatment of cryptosporidiosis. We have identified a structurally distinct class of CDPK1 inhibitors that demonstrate promising enzymatic potency, selectivity over representative human kinases, encouraging anti-parasitic activity in cell culture and a mouse cryptosporidiosis model. The overall goal of this study is to refine this new class of CDPK1 inhibitors and to define the optimal tissue targeting for efficient treatment of cryptosporidiosis. This will be achieved by pursuing three specific aims. The first aim will conduct structure-activity relationship analysis and optimization using structure-guided design to achieve highly potent and selective CDPK1 inhibitors with minimal activity on human kinases. We will also develop an innovative design allowing for glucuronidation-mediated enterohepatic recycling to maximize GI tissue targeting for direct comparison to systemically available derivatives. The second aim will evaluate in vivo pharmacokinetic, biodistribution, impact on the host microbiota and acute toxicity properties of the CDPK1 inhibitors. The third aim will evaluate and compare optimized GI-tissue targeting with systemically bioavailable CDPK1 inhibitors in a mouse model of cryptosporidiosis and dose escalating toxicity. Achieving the goal of this study will provide valuable tool compounds for the biomedical research community, candidates for further clinical development and guidance for optimal tissue distribution that can be applied in other anti-Cryptosporidium drug discovery programs.
