Safety and parasite clearance of artemisinin-resistant Plasmodium falciparum infection: A pilot and a randomised volunteer infection study in Australia

Abstract

Background Artemisinin resistance is threatening malaria control. We aimed to develop and test a human model of artemisinin-resistant (ART-R) Plasmodium falciparum to evaluate the efficacy of drugs against ART-R malaria. Methods and findings We conducted 2 sequential phase 1, single-centre, open-label clinical trials at Q-Pharm, Brisbane, Australia, using the induced blood-stage malaria (IBSM) model, whereby healthy participants are intravenously inoculated with blood-stage parasites. In a pilot study, participants were inoculated (Day 0) with approximately 2,800 viable P. falciparum ART-R parasites. In a comparative study, participants were randomised to receive approximately 2,800 viable P. falciparum ART-R (Day 0) or artemisinin-sensitive (ART-S) parasites (Day 1). In both studies, participants were administered a single approximately 2 mg/kg oral dose of artesunate (AS; Day 9). Primary outcomes were safety, ART-R parasite infectivity, and parasite clearance. In the pilot study, 2 participants were enrolled between April 27, 2017, and September 12, 2017, and included in final analyses (males n = 2 [100%], mean age = 26 years [range, 23-28 years]). In the comparative study, 25 participants were enrolled between October 26, 2017, and October 18, 2018, of whom 22 were inoculated and included in final analyses (ART-R infected participants: males n = 7 [53.8%], median age = 22 years [range, 18-40 years]; ARTS infected participants: males n = 5 [55.6%], median age = 28 years [range, 22-35 years]). In both studies, all participants inoculated with ART-R parasites became parasitaemic. A total of 36 adverse events were reported in the pilot study and 277 in the comparative study. Common adverse events in both studies included headache, pyrexia, myalgia, nausea, and chills; none were serious. Seven participants

Development and evaluation of a new Plasmodium falciparum 3D7 blood stage malaria cell bank for use in malaria volunteer infection studies

“…Parasite viability of 3D7-MBE-008 was determined using flow cytometry as previously described [ 20 ] at the time of manufacture and then in an ongoing stability and sterility program, with testing every 12 months. The viability of the parasites in the 3D7-V1 bank was determined at the time of manufacture by limiting dilution assay followed by PCR as previously described [ 19 ].…”

“…The viability of ring stage parasites in the MBE-008 MCB was assessed by flow cytometry as previously described [ 20 ], to identify the dilution required to achieve an inoculum dose similar to 3D7-V2 MCB. To prepare the inoculum, one or more vials of the MCB were thawed, with the resulting red cell pellet washed and resuspended in 0.9% sodium chloride.…”

“…An alternative approach is the in vitro manufacture of banks using a bioreactor, such as the Wave ™ 25 bioreactor system [ 17 ]. This method has been used previously to produce and test in vivo two cell banks, a genetically modified P. falciparum blood stage-cell bank [ 17 ], and an arteminisin-resistant P. falciparum cell bank [ 20 ]. This proved to be a cost-efficient method for the production of a MCB for use in IBSM studies [ 17 , 21 ].…”

Development and evaluation of a new Plasmodium falciparum 3D7 blood stage malaria cell bank for use in malaria volunteer infection studies

“…Parasite viability of 3D7-MBE-008 was determined using ow cytometry as previously described [20] at the time of manufacture and then in an ongoing stability and sterility program, with testing every 12 months. The viability of the parasites in the 3D7-V1 bank was determined at the time of manufacture by limiting dilution assay followed by PCR as previously described [19].…”

Molecular approaches to Malaria 2020

“…Dr Maria Rebelo from QIMR Berhofer Medical Research Institute, Australia, investigated the viability of artemisinin‐resistant (K13) and artemisinin‐sensitive (3D7) P . falciparum parasites after artesunate treatment in human volunteer infection studies (Watts et al, 2020). Parasite growth was assessed in pre‐ and post‐treatment samples using flow cytometry on ex vivo cultures then the percentage of viable parasites estimated using exponential growth mathematical models.…”