Malaria is a devastating disease that affects nearly half the world's population and results in more than 440,000 deaths per year. Due to increased drug resistance reported throughout Southeast Asia, it is widely accepted that new drugs with novel mechanisms are required to combat this epidemic. Plasmodium falciparum, the malarial parasite that causes the most deaths, utilizes a complex lifecycle initially infecting hepatocytes, followed by the reproductive cycle in mature erythrocytes and finally gametocyte differentiation for transmission to the mosquito host. As malarial symptoms are caused by the repeated invasion and lysis of erythrocytes, the majority of drug treatments target the blood-stage parasite. Plasmodium de novo lipid biosynthesis has been suggested to be critical for blood-, liver-, and gametocyte development stages; therefore, drugs that affect phospholipid metabolism may be useful not only for blood stage treatment but may also provide the added benefit of prophylactic and transmission-blocking activities. Plasmodium de novo PC biosynthesis is accomplished through the cytidine diphosphate-choline pathway beginning with the ATP- dependent phosphorylation of choline by choline kinase (CK). Based on essentiality, a broad expression profile across all key infection stages, opportunity for selectivity over the human CK protein, and ability to be inhibited by small molecules, I hypothesize that P. falciparum CK will be an excellent target for the design of novel antimalarial drugs. Choline mimetic P. falciparum CK inhibitors have been reported to have antimalarial activity; however, these inhibitors have poor drug-like properties, exhibit off-target effects, and are mildly toxic to human cells.
Specific Aim 1 combines computational and chemical high throughput screening (HTS) approaches to identify CK inhibitors that will target the adenine, rather than choline, substrate binding site as adenine pockets are well-documented druggable motifs for other kinases. Identified inhibitors will be evaluated for their ability to overcome the limitations of currently characterized CK inhibitors including reducing off-target effects and improving parasite homolog specificity.
Specific Aim 2 will characterize the efficacy of the identified inhibitors as antimalarials in cell-based assays where hit series showing good drug-like properties and strong activity against both P. falciparum CK and the parasite will be prioritized for future development.
Specific Aim 3 will elucidate the molecular interactions between P. falciparum CK and inhibitors by x-ray crystallography. These interactions will be optimized to improve inhibitor potency and selectivity by generating structure-activity relationships. The outcome of these studies will be to 1) establish a new enzymatic target for antimalarial drug discovery and 2) deliver a well-characterized hit series targeting P. falciparum CK for a future lead optimization program directed at developing a novel antimalarial agent.
Malaria is a devastating disease that affects nearly half the world's population, an estimated 3.3 billion people, and resulted in more than 440,000 deaths in 2015 alone. Due to emergence of malaria drug resistance, I intend to confirm that an enzyme involved in lipid synthesis is essential for the malarial parasite. Furthermore, I will deliver a set of well-characterized inhibitors that target this enzyme as the foundation for novel antimalarial drug development.
