Last Updated: 31/08/2025
Discovery of Antimalarial Drugs Using Humanized Pseudo-Liver Immunodeficient Mouse Model
Objectives
The overall objectives of this study are three-fold.
- First, to optimize and qualify the pseudo huLivNSG mouse model using engraftment of a human liver cell line that retains human hepatocyte-like characteristics and is well-vascularized following subcutaneous growth;
- Second, this model will be incorporated as part of a testing strategy to identify new 8-AQs that overcome either the toxicity liability or the pharmaco-genomic liability of the class. If drugs can be identified that circumvent the toxicity of 8AQs, this would be an important advance in antimalaria drug development; and
- Third, to incorporate this model into a testing strategy that includes the P. berghei CYP2D knockout IVIS model already in place at WRAIR, to identify compounds that are active against liver stage parasite and do not require CYP 2D6 activation for in vivo efficacy.
The focus will complement the current medicinal chemistry effort at WRAIR to find liver stage active 8-AQ analogs that circumvent CYP2D activation, which has several very promising lead compounds.
The specific aims are:
- Qualify the P. falciparum pseudo-huLiv NSG mouse model for human Plasmodium infection and drug discovery using Walter Reed Army Institute of Research (WRAIR) legacy 8-AQ analogs;
- Assess efficacy and toxicity of 8-AQ analogs in preclinical mouse models; and
- Synthesize an 8-AQ that does not require CYP2D6 for metabolic activation and that clears P. falciparum liver stage infection in the pseudo-huLiv NSG mouse model.
Walter Reed Army Institute of Research (WRAIR), United States
The 8-Aminoquinoline (8-AQ) drugs are among the most effective of the antimalarial drug classes available. Primaquine (PQ), the prototypic 8-AQ, is the only approved drug able to eliminate the hypnozoite stage of Plasmodium vivax that is responsible for relapsing malaria. PQ is also effective against the gametocyte stage, suggesting that 8-AQs will be important in malaria transmission blocking campaigns. The unique efficacy profile of 8-AQs differentiates this class as a powerful weapon in the arsenal targeting malaria treatment and prophylaxis. However, two issues complicate the use of 8-AQs: the requirement for cytochrome p450 (CYP) 2D6 activation for the in vivo efficacy against Plasmodium parasites and the induction of hemolytic anemia in individuals with glucose 6 phosphate dehydrogenase (G6PD) deficiency. Preliminary data indicate that there are 8-AQs that have reduced hemolytic toxicity but retain efficacy comparable to PQ and that using rational drug design of 8-AQs designed to release a 5-OH PQ that circumvents CYP 2D metabolism.
Three different in vivo pre-translational models have been developed to test the efficacy and hemolytic toxicity of 8-AQs. The first model is the G6PDd huRBC SCID mouse model that tests hemolytic toxicity. The second model is the P. bergheicausal prophylactic (CP) IVIS model for prescreening of liver stage activity and for testing the requirement for CYP2D metabolism in efficacy. The final model that will be qualified in this proposal is the pseudo-huLiv NSG model that tests antimalaria drug efficacy against human Plasmodium infection.
Combined with extensive experience in medicinal chemistry and utilizing the animal model tools available, the research team will test the following hypothesis: the pseudo-huLiver NSG mouse model can be used for testing causal prophylaxis against human Plasmodium infection that will provide preclinical in vivo data reflective of human malaria efficacy. Furthermore, the molecular species of 8-AQ that is responsible for antimalaria liver stage efficacy is a different molecular entity than that which is responsible for 8-AQ mediated hemolytic effects on G6PDd huRBC.
It is anticipated that at the end of the study period, the team will have qualified a new mouse model, the P. falciparuminfection of pseudo-huLiv NSG model, that is significantly less expensive than existing humanized liver models, thus making it suitable as a drug screening tool for testing antimalaria drugs for causal prophylaxis. The utilization of this model in the current drug testing paradigm along with the evaluation of WRAIR legacy 8-AQ compounds along with rational drug design of new 8-AQs will identify new 8-AQs that will lead to the identification of at least one novel candidate molecule for profiling as a potential antimalarial treatment and prophylactic drug. The data obtained from the project will be used in support of Investigational New Drug and New Drug Application filings to the Food and Drug Administration and address the Department of Defense’s critical mission of developing antimalarial agents to protect the Warfighter deployed or traveling through malaria-endemic regions. In the process of working towards a candidate nomination, it is expected that the data gathered in this series will help define structural and physicochemical properties that impact blood stage activity, liver stage activity, and pharmacokinetic properties that may be applicable in structurally related chemical series. These data could inform the research community about strategies that may help solve issues in the field of antimalarial drug discovery.
Aug 2016 — Sep 2020
$1.03M
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