Model System Identifies Kinetic Driver of Hsp90 Inhibitor Activity against African Trypanosomes and Plasmodium falciparum

Abstract

Hsp90 inhibitors, well studied in the laboratory and clinic for antitumor indications, have promising activity against protozoan pathogens, including which causes African sleeping sickness, and the malaria parasite, To progress these experimental drugs toward clinical use, we adapted an dynamic hollow-fiber system and deployed artificial pharmacokinetics to discover the driver of their activity: either concentration or time. The activities of compounds from three major classes of Hsp90 inhibitors in development were evaluated against trypanosomes. In all circumstances, the activities of the tested Hsp90 inhibitors were concentration driven. By optimally deploying the drug to match its kinetic driver, the efficacy of a given dose was improved up to 5-fold, and maximal efficacy was achieved with a significantly lower drug exposure. The superiority of concentration-driven regimens was evident over several logs of drug exposure and was predictive of efficacy in a mouse model of African trypanosomiasis. In studies with , antimalarial activity was similarly concentration driven. This experimental strategy offers an expedient and versatile translational tool to assess the impact of pharmacokinetics on antiprotozoal activity. Knowing kinetic governance early in drug development provides an additional metric for judging lead compounds and allows the incisive design of animal efficacy studies.

From Circulation to Cultivation: Plasmodium In Vivo versus In Vitro

“…Gentle shaking of Plasmodium cultures can partially overcome the challenges associated with high hematocrit and parasitemia, while also increasing chances for non-motile merozoites to contact and invade uninfected RBCs. Utilization of non-traditional culture systems that allow for continual flow of RBCs through an in vivo-like environment, such as hollow-fiber capillary bioreactors (HFBRs), further overcomes this problem; HFBRs allow for high parasite replication at physiological hematocrit levels by not only increasing surface area for nutrient exchange but also by allowing continual addition of fresh medium [25][26][27][28][29]. The pumped fluid flow design of HFBRs has specifically facilitated precise in vitro modulation of drug concentrations over time, generating conditions that more closely mimic the pharmacokinetics of in vivo drug treatment [25,26,28].…”

Kinetic Driver of Antibacterial Drugs against Plasmodium falciparum and Implications for Clinical Dosing

“…These studies provide clear evidence that the antimalarial efficacy of the four studied antibacterials is time-driven in vitro: enhanced by constant presence above a therapeutic threshold. Though ostensibly logical that any antimalarial should continuously be kept above the MIC, time dependence of these agents is distinctly different from the concentration-driven artemisinins and experimental Hsp90 inhibitors, for which the same total dose and AUC are best deployed as a short-lived high concentration, despite many subsequent hours without meaningful drug levels, an in vitro finding confirmed in animals (19,20). Interestingly, the time dependence of CIP efficacy against malaria parasites is unlike its concentration-driven action against bacteria (Table 1).…”

“…Time-kill curves, which variably capture any post-anti-infective response, may not faithfully reflect kinetic governance (10). The kinetic driver of antibacterial action is, however, the same across a therapeutic class of agents (e.g., all aminoglycosides are concentration-driven), and we recently demonstrated this to be so for antitrypanosomals (19).…”

“…Using a novel apparatus that can deploy, in vitro, dynamically changing drug concentrations against P. falciparum, we demonstrated that the concept of efficacygoverning PK driver (either concentration or time) is also applicable to antimalarial drugs (19,20). The remarkable activity of short-lived artemisinins (with plasma half-lives Time 3 Tetracycline 70S ribosome, 30S subunit Time 6Ϫ11 Chloramphenicol 70S ribosome, 50S subunit Time 3 Ciprofloxacin DNA gyrase, topoisomerase IV Concn 4…”

Comparative analyses of parasites with a comprehensive database of genome-scale metabolic models

“…As a result of these difficulties ( Figure 1A ), data collected in one organism are frequently extrapolated to infer knowledge about another parasite, across and within genera ( Figure 1B ). Toxoplasma gondii is frequently used as a model organism for other apicomplexa due to its genetic and biochemical manipulability (Li and He 2017; Meyer, Caton, and Shapiro 2018; Sidik et al 2016; Kim and Weiss 2004). Mouse models of malaria (Huang, Pearman, and Kim 2015; Minkah, Schafer, and Kappe 2018) and cryptosporidiosis (Ward 2017; Sateriale et al 2019) imperfectly represent the disease and/or use different species than the human pathogen.…”