Characterizing the blood stage antimalarial activity of pyronaridine in healthy volunteers experimentally infected with Plasmodium falciparum

Although pyronaridine has been used to successfully treat malaria for many years, its antimalarial activity in humans has not been completely characterized. This volunteer infection study aimed to determine the pharmacokinetic/pharmacodynamic (PK/PD) relationship of pyronaridine in healthy malaria naïve adults. Volunteers were inoculated with Plasmodium falciparum 3D7-infected erythrocytes on day 0 and different single oral doses of pyronaridine were administered on day 8. Parasitemia, and concentrations of pyronaridine in whole blood were measured and standard safety assessments performed. Curative artemether-lumefantrine therapy was administered if parasite regrowth occurred, or on day 47±2. Outcomes were parasite clearance kinetics, PK and PK/PD parameters from modelling. Ten participants were inoculated and administered 360 mg (n=4), 540 mg (n=4), or 720 mg (n=1) pyronaridine. One participant was withdrawn without receiving pyronaridine. Time to maximum pyronaridine concentration after dosing was 1-2 hours and the elimination half-life was 8-9 days. A parasite clearance half-life of approximately 5 hours was calculated for all dose levels. Parasite regrowth occurred after dosing with 360 mg (4/4 participants) and 540 mg (2/4 participants). Key efficacy parameters of pyronaridine including the minimum inhibitory concentration (MIC: 5.5 ng/mL) and minimum parasiticidal concentration that leads to 90% of maximum effect (MPC90: 8 ng/mL) were derived from the final PK/PD model. Adverse events considered related to pyronaridine were predominantly mild to moderate gastrointestinal symptoms. There were no serious adverse events. Data obtained in this study will support the use of pyronaridine in new antimalarial combination therapies by informing partner drug selection and dosing considerations. ### Competing Interest Statement BEB declares receipt of funding from Medicines for Malaria Venture (MMV) to perform the study. JJM, ACM, JF, and NG are employees of MMV. ACM declares holding shares in Novartis, Alcon and Idorsia. All other authors declare no conflicts of interest. ### Clinical Trial NCT05287893 ### Funding Statement This study was funded by a grant from the Bill and Melinda Gates Foundation (INV-007155) awarded to Medicines for Malaria Venture (MMV). ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: This study was approved by the QIMR Berghofer Human Research Ethics Committee (P3800). I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as [ClinicalTrials.gov][1]. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors. * AEs : adverse events BSM : induced blood stage malaria PK/PD : pharmacokinetic/pharmacodynamics VIS : volunteer infection study. [1]: http://ClinicalTrials.gov