In vitro pharmacodynamic drug-drug interaction and translational evaluation of cabamiquine and pyronaridine as new antimalarial combination using P.falciparum field isolates
Sebastian G. Wicha (1), Maiga Mohamed (2), Akash Khandelwal (3), Perrine Courlet (4) Thomas Spangenberg (5), Claude Oeuvray (5), Laurent Dembélé (2), Claudia Demarta-Gatsi (5)
(1) Department of Clinical Pharmacy, Institute of Pharmacy, University of Hamburg, Bundesstr. 45, 20146 Hamburg, Germany (2) Malaria Research and Training Centre (MRTC), Faculty of Pharmacy, Université des Sciences, des Techniques et des Technologies de Bamako (USTTB), Bamako, Mali (3) The healthcare business of Merck KGaA, Darmstadt, Germany (4) Merck Institute for Pharmacometrics, Ares Trading S.A. (an affiliate of Merck KGaA, Darmstadt, Germany), Lausanne, Switzerland (5) Global Health Institute of Merck, Ares Trading S.A., Route de Crassier 1, 1262 Eysins, Switzerland, a subsidiary of Merck KGaA, Darmstadt, Germany
Objectives
Every year, malaria continues to inflict extensive morbidity and mortality in resource-poor countries. In recent decades, new interventions, such as antimalarial drug combinations have become available to reduce the burden of malaria. However, this progress has slowed down due to the spread of Plasmodium falciparum resistance to several drugs in the antimalarial armamentarium. Cabamiquine is a novel antimalarial drug acting as a Plasmodium elongation factor 2 inhibitor [1]. While monotherapy of cabamiquine led to selection of mutant parasites in the P. falciparum animal model, its combination with pyronaridine led to the suppression of cabamiquine-resistant mutants, as well as significantly delay the recrudescence of parasites both with suboptimal and optimal dosing regimens [2]. The objective of the study was to provide a detailed assessment of the potential pharmacodynamic (PD) interaction between both compounds in vitro. Findings were then translated into the clinical perspective to support optimization of cabamiquine dose using modelling and simulations.
Methods
A total of seven wild type P. falciparum field isolate parasites sensitive to cabamiquine and two in vitro selected mutant P. falciparum field isolate parasites resistant to cabamiquine were cultured in 96 well plates at 1% parasitemia and 2% haematocrit up to 72 h. At the end of the drug treatment, the sensitivity of the parasites was assessed using a SYBR Green assay combined with Mitotracker readout as previously reported [3].
The parasite kinetics of the seven wild type strains was modelled jointly using a one compartment model with growth and drug mediated-killing in a non-linear mixed effects model in NONMEM® 7.5, while separate models were built for the resistant isolates. For cabamiquine, adaptive resistance development, i.e. parasite growth after initial killing was observed in the raw data. This was modelled by a concentration- and time-dependent EC50 using an adaptive resistance compartment [4]. Potential PD interactions were quantified as deviation from Bliss Independence and quantified using the general PD interaction (GPDI) model [5].
Simulations based on a previously developed pharmacokinetic model [6] were performed to identify cabamiquine doses which would allow to exceed the model predicted EC50. [KJ1] A virtual population of 5000 African adults receiving one cabamiquine dose varying from 60 to 660 mg was simulated using the mrgsolve package in R.
Results
The parasite kinetics of the seven wild type field isolates was well described by the model. For pyronaridine, a constant EC50 described the data well, whereas for cabamiquine the model accounting for adaptive resistance development of cabamiquine provided a superior model fit as compared to the model with a sole time-dependent EC50 (delta Akaike Information Criterion (dAIC): +91.44) or a static EC50 (dAIC: +634.16). The typical value of the EC50 of cabamiquine was increased from 0.799 nM to a maximum value of 5.90 nM. Inter-parasite variability was supported on the parasite growth rate, EC50 of both drugs, maximum adaption towards cabamiquine and initial assay signal as well as baseline assay signal.
Using the estimated distribution of EC50 and the maximum adaption factor, the EC50,90% (i.e. the 90% percentile of the EC50 distribution) was derived for cabamiquine, which was 1.34 nM at t=0 h and 18.8 nM after full adaption. An additive PD interaction using Bliss Independence described the data well. Of note, the observed regrowth in the cabamiquine monotherapy arm, suggesting adaptive resistance to the drug, was suppressed when pyronaridine concentrations exceeded its EC50.
The results of simulations suggested that a cabamiquine dose of at least 200 mg is required to observe cure (concentrations > EC50,90%) in >95% of the population.
For one of the resistant isolates, modelling revealed a synergistic interaction, where inactive cabamiquine potentiated the effect of pyronaridine, which was inactive alone at 5 nM, but became active in combination. For the other resistant isolate, additivity was observed.
Conclusions
The present study used modelling and simulation techniques to evaluate the combination of cabamiquine and pyronaridine in vitro and translated the findings into the clinical setting. This approach will allow the selection of suitable drug combinations early in the drug development process, as well as their respective doses, that promise to work in a clinical setting.
References:
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[6] J. Wilkins, Justin J., W. M. Bagchus, Ö. Yalkinoglu, C. Oeuvray, J. S. McCarthy, und A. Khandelwal, „Population Pharmacokinetics analysis of M5717, a novel antimalarial agent“, in PAGE Meeting, 2019, S. Abstr 9044. [Online]. Verfügbar unter: https://www.page-meeting.org/?abstract=9044