Malaria clinical studies entailing the experimental infection of healthy volunteers with
parasites by bites from infected mosquitos, injection of cryopreserved sporozoites, or injection of ...blood-stage parasites provide valuable information for vaccine and drug development. Success of these studies depends on maintaining safety. In this mini-review, we discuss the safety risks and associated mitigation strategies of these three types of experimental malaria infection. We aimed to inform researchers and regulators who are currently involved in or are planning to establish experimental malaria infection studies in endemic or non-endemic settings.
...we conducted a pilot study in which we inoculated participants with ART-R P. falciparum parasites harbouring the kelch13 gene mutation R539T (K13R539T strain) 4 to determine the safety, ...tolerability, and clearance of infection with ART-R parasites. Methods Study design We conducted 2 consecutive phase 1, single-centre, open-label studies: a pilot study and a randomised study. ART-R, artemisinin-resistant; ART-S, artemisinin-sensitive; A/P, atovaquone/proguanil; AS, artesunate; DHA/PQP, dihydroartemisinin/piperaquine phosphate; IV, intravenously; PQ, primaquine; qPCR, quantitative PCR https://doi.org/10.1371/journal.pmed.1003203.g001 Development of parasitaemia was monitored daily from Day 3 (pilot study Participant 1) or Day 4 (pilot study Participant 2 and comparative study) until parasites were detected by qPCR, then twice daily until AS administration. Outcomes A primary outcome of both studies was safety and tolerability of infection with ART-R parasites (and of ART-S parasites in the comparative study only), determined by evaluating adverse events, physical examinations, vital signs, clinical biochemistry, haematology, and urinalysis.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
In the absence of a method to culture Plasmodium vivax, the only way to source parasites is ex vivo. This hampers many aspects of P. vivax research. This study aimed to assess the safety of ...apheresis, a method for selective removal of specific components of blood as a means of extracting and concentrating P. vivax parasites.
An iterative approach was employed across four non-immune healthy human subjects in single subject cohorts. All four subjects were inoculated with ~ 564 blood stage P. vivax (HMP013-Pv) and subjected to apheresis 10 to 11 days later. Blood samples collected during apheresis (haematocrit layers 0.5% to 11%) were tested for the presence and concentration of P. vivax by microscopy, flow cytometry, 18S rDNA qPCR for total parasites, and pvs25 qRT-PCR for female gametocyte transcripts. Safety was determined by monitoring adverse events. Malaria transmission to mosquitoes was assessed by membrane feeding assays.
There were no serious adverse events and no significant safety concerns. Apheresis concentrated asexual parasites by up to 4.9-fold (range: 0.9-4.9-fold) and gametocytes by up to 1.45-fold (range: 0.38-1.45-fold) compared to pre-apheresis densities. No single haematocrit layer contained > 40% of all the recovered P. vivax asexual parasites. Ex vivo concentration of parasites by Percoll gradient centrifugation of whole blood achieved greater concentration of gametocytes than apheresis. Mosquito transmission was enhanced by up to fivefold in a single apheresis sample compared to pre-apheresis.
The modest level of parasite concentration suggests that the use of apheresis may not be an ideal method for harvesting P. vivax. Trial Registration Australia New Zealand Clinical Trials Registry (ANZCTR) Trial ID: ACTRN12617001502325 registered on 19th October 2017. https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=373812.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Summary Background Medical tourism, where patients travel abroad intentionally to access medical treatment, is a growing trend. Some of these patients travel to undergo organ transplantation. This ...study aims to quantify the number of UK patients who undergo liver transplantation abroad, assessing their motivations and management. Methods Questionnaires were sent to all seven UK liver transplant units enquiring about liver patients receiving transplant abroad. Included were questions on destination, motivation, and pre and post-transplant care. Results Responses were received from six of the seven transplant centres (86%). A total of 12 patients were identified as having undergone liver transplantation overseas. The top destinations were India, China and Egypt. Four units responded to questions regarding pre-transplant screening. One unit reported Hepatitis B and C screening not taking place. Four units responded to questions regarding post-transplant antimicrobial therapy. This revealed examples of patients inappropriately not receiving valganciclovir, co-trimoxazole, anti-fungal treatment and Hepatitis B immunoglobulins. Conclusions UK patients are undergoing liver transplant abroad, albeit in small numbers. Pre and post-transplant management of these patients is of a lower standard than that provided to those undergoing transplantation in the UK. Information transfer between overseas and UK based transplant teams is poor.
Summary Background Due to ongoing poor availability of organs, increasingly patients from developed countries are reported to be travelling abroad for renal transplants. We aimed to assess the extent ...and characteristics of this trend across the UK and Republic of Ireland. Methods A questionnaire-based cross-sectional survey; 397 renal consultants from 33 hospitals with renal units across the UK and the Republic of Ireland were contacted through email and 62 replied (16%). Results Fifty-seven out of 62 (93%) renal consultants managed transplant patients, and of these 36/57 (63%) had managed at least one patient who had undergone a transplant abroad. The most popular reason reported for doing this was being on the UK or Republic of Ireland transplant list but seeking a shorter wait. Respondents reported commencement by overseas doctors of appropriate routine post-transplant prophylaxis with the following medications in all cases they had encountered as follows: co-trimoxazole 12%, isoniazid 3%, anti-fungals 0%, and Cytomegalovirus prophylaxis or treatment 0%. Fourty-four percent of renal consultants reported having some prior warning of a patient undergoing a renal transplant abroad. Conclusions Renal transplant tourism has become widely established in the UK and the Republic of Ireland, and care for these patients is often suboptimal. Furthermore, the opportunity exists for pre-transplant counselling.
M5717 is the first plasmodium translation elongation factor 2 inhibitor to reach clinical development as an antimalarial. We aimed to characterise the safety, pharmacokinetics, and antimalarial ...activity of M5717 in healthy volunteers.
This first-in-human study was a two-part, single-centre clinical trial done in Brisbane, QLD, Australia. Part one was a double-blind, randomised, placebo-controlled, single ascending dose study in which participants were enrolled into one of nine dose cohorts (50, 100, 200, 400, 600, 1000, 1250, 1800, or 2100 mg) and randomly assigned (3:1) to M5717 or placebo. A sentinel dosing strategy was used for each dose cohort whereby two participants (one assigned to M5717 and one assigned to placebo) were initially randomised and dosed. Randomisation schedules were generated electronically by independent, unblinded statisticians. Part two was an open-label, non-randomised volunteer infection study using the Plasmodium falciparum induced blood-stage malaria model in which participants were enrolled into three dose cohorts. Healthy men and women of non-childbearing potential aged 18–55 years were eligible for inclusion; individuals in the volunteer infection study were required to be malaria naive. Safety and tolerability (primary outcome of the single ascending dose study and secondary outcome of the volunteer infection study) were assessed by frequency and severity of adverse events. The pharmacokinetic profile of M5717 was also characterised (primary outcome of the volunteer infection study and secondary outcome of the single ascending dose study). Parasite clearance kinetics (primary outcome of the volunteer infection study) were assessed by the parasite reduction ratio and the corresponding parasite clearance half-life; the incidence of recrudescence up to day 28 was determined (secondary outcome of the volunteer infection study). Recrudescent parasites were tested for genetic mutations (exploratory outcome). The trial is registered with ClinicalTrials.gov (NCT03261401).
Between Aug 28, 2017, and June 14, 2019, 221 individuals were assessed for eligibility, of whom 66 men were enrolled in the single ascending dose study (eight per cohort for 50–1800 mg cohorts, randomised three M5717 to one placebo, and two in the 2100 mg cohort, randomised one M5717 to one placebo) and 22 men were enrolled in the volunteer infection study (six in the 150 mg cohort and eight each in the 400 mg and 800 mg cohorts). No adverse event was serious; all M5717-related adverse events were mild or moderate in severity and transient, with increased frequency observed at doses above 1250 mg. In the single ascending dose study, treatment-related adverse events occurred in three of 17 individuals in the placebo group; no individual in the 50 mg, 100 mg, or 200 mg groups; one of six individuals in each of the 400 mg, 1000 mg, and 1250 mg groups; two of six individuals in the 600 mg group; and in all individuals in the 1800 mg and 2100 mg groups. In the volunteer infection study, M5717-related adverse events occurred in no participants in the 150 mg or 800 mg groups and in one of eight participants in the 400 mg group. Transient oral hypoesthesia (in three participants) and blurred vision (in four participants) were observed in the 1800 mg or 2100 mg groups and constituted an unknown risk; thus, further dosing was suspended after dosing of the two sentinel individuals in the 2100 mg cohort. Maximum blood concentrations occurred 1–7 h after dosing, and a long half-life was observed (146–193 h at doses ≥200 mg). Parasite clearance occurred in all participants and was biphasic, characterised by initial slow clearance lasting 35–55 h (half-life 231·1 h 95% CI 40·9 to not reached for 150 mg, 60·4 h 38·6 to 138·6 for 400 mg, and 24·7 h 20·4 to 31·3 for 800 mg), followed by rapid clearance (half-life 3·5 h 3·1 to 4·0 for 150 mg, 3·9 h 3·3 to 4·8 for 400 mg, and 5·5 h 4·8 to 6·4 for 800 mg). Recrudescence occurred in three (50%) of six individuals dosed with 150 mg and two (25%) of eight individuals dosed with 400 mg. Genetic mutations associated with resistance were detected in four cases of parasite recrudescence (two individuals dosed with 150 mg and two dosed with 400 mg).
The safety, pharmacokinetics, and antimalarial activity of M5717 support its development as a component of a single-dose antimalarial combination therapy or for malaria prophylaxis.
Wellcome Trust and the healthcare business of Merck KGaA, Darmstadt, Germany.
Abstract
Background
Plasmodium malariae is considered a minor malaria parasite, although its global disease burden is underappreciated. The aim of this study was to develop an induced blood-stage ...malaria (IBSM) model of P. malariae to study parasite biology, diagnostic assays, and treatment.
Methods
This clinical trial involved 2 healthy subjects who were intravenously inoculated with cryopreserved P. malariae–infected erythrocytes. Subjects were treated with artemether-lumefantrine after development of clinical symptoms. Prior to antimalarial therapy, mosquito-feeding assays were performed to investigate transmission, and blood samples were collected for rapid diagnostic testing and parasite transcription profiling. Serial blood samples were collected for biomarker analysis.
Results
Both subjects experienced symptoms and signs typical of early malaria. Parasitemia was detected 7 days after inoculation, and parasite concentrations increased until antimalarial treatment was initiated 25 and 21 days after inoculation for subjects 1 and 2 respectively (peak parasitemia levels, 174 182 and 50 291 parasites/mL, respectively). The parasite clearance half-life following artemether-lumefantrine treatment was 6.7 hours. Mosquito transmission was observed for 1 subject, while in vivo parasite transcription and biomarkers were successfully profiled.
Conclusions
An IBSM model of P. malariae has been successfully developed and may be used to study the biology of, diagnostic testing for, and treatment of this neglected malaria species.
Clinical Trials Registration
ACTRN12617000048381.
A human model of Plasmodium malariae infection has been successfully developed and may be used to study the biology of, diagnostic testing for, and treatment of this neglected malaria species.
Malaria volunteer infection studies (VISs) accelerate new drug and vaccine development. In the induced blood-stage malaria (IBSM) model, volunteers are inoculated with erythrocytes infected with
. ...Observations of elevated liver enzymes in the IBSM model with new chemical entities (NCEs) promoted an analysis of available data. Data were reviewed from eight IBSM studies of seven different NCEs, plus two studies with the registered antimalarial piperaquine conducted between June 2013 and January 2017 at QIMR Berghofer, Brisbane, Australia. Alanine aminotransferase (ALT) was elevated (> 2.5 times the upper limit of normal ×ULN) in 20/114 (17.5%) participants. Of these, 8.9% (10/114) had moderate increases (> 2.5-5 × ULN), noted in seven studies of six different NCEs ± piperaquine or piperaquine alone, and 8.9% (10/114) had severe elevations (> 5 × ULN), occurring in six studies of six different NCEs ± piperaquine. Aspartate aminotransferase (AST) was elevated (> 2.5 × ULN) in 11.4% (13/114) of participants, across six of the 10 studies. Bilirubin was > 2 × ULN in one participant. Published data from other VIS models, using sporozoite inoculation by systemic administration or mosquito feeding, also showed moderate/severe liver enzyme elevations. In conclusion, liver enzyme elevations in IBSM studies are most likely multifactorial and could be caused by the model conditions, that is, malaria infection/parasite density and/or effective parasite clearance, or by participant-specific risk factors, acetaminophen administration, or direct hepatotoxicity of the test drug. We make recommendations that may mitigate the risk of liver enzyme elevations in future VISs and propose measures to assist their interpretation, should they occur.
BACKGROUNDInterventions that interrupt Plasmodium vivax transmission or eliminate dormant P. vivax liver-stage parasites will be essential for malaria elimination. Development of these interventions ...has been hindered by the lack of P. vivax in vitro culture and could be accelerated by a safe and reproducible clinical model in malaria-naive individuals.METHODSHealthy, malaria-naive adults were enrolled in 2 studies to assess the safety, infectivity, and transmissibility of a new P. vivax isolate. Participants (Study 1, n = 2; Study 2, n = 24) were inoculated with P. vivax-infected red blood cells to initiate infection, and were treated with artemether-lumefantrine (Study 1) or chloroquine (Study 2). Primary endpoints were safety and infectivity of the new isolate. In Study 2, transmission to mosquitoes was also evaluated using mosquito feeding assays, and sporozoite viability was assessed using in vitro cultured hepatocytes.RESULTSParasitemia and gametocytemia developed in all participants and was cleared by antimalarial treatment. Adverse events were mostly mild or moderate and none were serious. Sixty-nine percent of participants (11/16) were infectious to Anopheles mosquitoes at peak gametocytemia. Mosquito infection rates reached 97% following membrane feeding with gametocyte-enriched blood, and sporozoites developed into liver-stage schizonts in culture.CONCLUSIONWe have demonstrated the safe, reproducible, and efficient transmission of P. vivax gametocytes from humans to mosquitoes, and have established an experimental model that will accelerate the development of interventions targeting multiple stages of the P. vivax life cycle.TRIAL REGISTRATIONACTRN12614000930684 and ACTRN12616000174482.FUNDING(Australian) National Health and Medical Research Council Program Grant 1132975 (Study 1). Bill and Melinda Gates Foundation (OPP1111147) (Study 2).
PDF
