Antimalarial efficacy of piperaquine-based antimalarial combination therapies: facts and uncertainties

Piperaquine Population Pharmacokinetics and Cardiac Safety in Cambodia

Despite the rising rates of resistance to dihydroartemisinin-piperaquine (DP), DP remains a first-line therapy for uncomplicated malaria in many parts of Cambodia. While DP is generally well tolerated as a 3-day DP (3DP) regimen, compressed 2-day DP (2DP) regimens were associated with treatment-limiting cardiac repolarization effects in a recent clinical trial. To better estimate the risks of piperaquine on QT interval prolongation, we pooled data from three randomized clinical trials conducted between 2010 and 2014 in northern Cambodia. A population pharmacokinetic model was developed to compare exposure-response relationships between the 2DP and 3DP regimens while accounting for differences in regimen and sample collection times between studies. A 2-compartment model with first-order absorption and elimination without covariates best fit the data. The linear slope-intercept model predicted a 0.05-ms QT prolongation per ng/ml of piperaquine (5 ms per 100 ng/ml) in this largely male population. Though the plasma half-life was similar in both regimens, peak and total piperaquine exposures were higher in those treated with the 2DP regimen. Furthermore, the correlation between the plasma piperaquine concentration and the QT interval prolongation was stronger in the population receiving the 2DP regimen. Neither the time since the previous meal nor the baseline serum magnesium or potassium levels had additive effects on QT interval prolongation. As electrocardiographic monitoring is often nonexistent in areas where malaria is endemic, 2DP regimens should be avoided and the 3DP regimen should be carefully considered in settings where viable alternative therapies exist. When DP is employed, the risk of cardiotoxicity can be mitigated by combining a 3-day regimen, enforcing a 3-h fast before and after administration, and avoiding the concomitant use of QT interval-prolonging medications. (This study used data from three clinical trials that are registered at ClinicalTrials.gov under identifiers NCT01280162, NCT01624337, and NCT01849640.).

Synthesis, antimalarial activity, heme binding and docking studies of N-substituted 4-aminoquinoline-pyrimidine molecular hybrids

A series of novel N-substituted 4-aminoquinoline-pyrimidine hybrids have been synthesized via simple and economic route and evaluated for their antimalarial activity. Most compounds showed potent antimalarial activity against both CQ-sensitive and CQ-resistant strains with high selectivity index. All the compounds were found to be non-toxic to the mammalian cell lines. The most active compound 7b was analysed for heme binding activity using UV-spectrophotometer. Compound was found to interact with heme and a complex formation between compound and heme in a 1:1 stoichiometry ratio was determined using job plots. The interaction of these hybrids was also investigated by the molecular docking studies in the binding site of wild type Pf-DHFR-TS and quadruple mutant Pf-DHFR-TS. The pharmacokinetic property analysis of best active compounds was also studied by ADMET prediction.

Single dose treatment of malaria - current status and perspectives

INTRODUCTION

Despite increased international efforts for control and ultimate elimination, malaria remains a major health problem. Currently, artemisinin-based combination therapies are the treatment of choice for uncomplicated malaria exhibiting high efficacy in clinical trial settings in sub-Saharan Africa. However, their administration over a three-day period is associated with important problems of treatment adherence resulting in markedly reduced effectiveness of currently recommended antimalarials under real world settings.

AREAS COVERED

Antimalarial drug candidates and antimalarial drug combinations currently under advanced clinical development for the indication as single dose antimalarial therapy. Expert commentary: Several new drug candidates and combinations are currently undergoing pivotal proof-of-concept studies or clinical development programmes. The development of a single dose combination therapy would constitute a breakthrough in the control of malaria. Such an innovative treatment approach would simultaneously close the effectiveness gap of current three-day therapies and revolutionize population based interventions in the context of malaria elimination campaigns.

Research progress in electroanalytical techniques for determination of antimalarial drugs in pharmaceutical and biological samples

The review focusses on the role of electroanalytical methods for determination of antimalarial drugs in biological matrices and pharmaceutical formulations with a critical analysis of published voltammetric and potentiometric methods.

Efficacy and safety of fixed dose combination of arterolane maleate and piperaquine phosphate dispersible tablets in paediatric patients with acute uncomplicated Plasmodium falciparum malaria: a phase II, multicentric, open-label study

BACKGROUND

The World Health Organization (WHO) recommends artemisinin combination therapy (ACT) for the treatment of uncomplicated Plasmodium falciparum malaria. The present study investigated the efficacy and safety of fixed dose combination (FDC) of arterolane maleate 37.5 mg and piperaquine phosphate (PQP) 187.5 mg dispersible tablets in paediatric patients aged 6 months to 12 years.

METHODS

Male and female patients aged 6 months to 12 years who were confirmed cases of P. falciparum mono-infection with fever or documented history of fever in the previous 24 h were included. The patients were administered FDC of arterolane maleate and PQP as single daily doses for three consecutive days based on their age. The primary efficacy outcome was proportion of patients with polymerase chain reaction (PCR)-corrected adequate clinical and parasitological response (ACPR) on day 28. Safety was analysed based on adverse events (AE), laboratory abnormalities and abnormalities on electrocardiograph.

RESULTS

A total of 141 eligible paediatric patients received FDC of arterolane maleate and PQP in a 42-day follow-up study. All the enrolled patients (141) were included in intention to treat (ITT) and safety analyses, and 126 patients were considered in per protocol (PP) population. The PCR-corrected ACPR on day 28 was achieved in all patients (100 %; 95 % CI 97.11-100) included in PP population. The median parasite clearance time (PCT) and fever clearance time (FCT) were 24 h (95 % CI 18.0-24.0) and 10 h (95 % CI 4.0-18.0), respectively. The most frequently reported clinical AE was vomiting. Majority of the AEs were mild to moderate in severity and resolved without sequelae. No patient was discontinued for any QTc (corrected QT interval) prolongation. No deaths or serious AEs were reported during the study.

CONCLUSION

The findings from this study showed that FDC of arterolane maleate and PQP effectively cures P. falciparum malaria and attains acceptable level of cure by day 28 in paediatric patients. The efficacy and safety results observed in children warrants further studies on FDC of arterolane maleate and PQP dispersible tablets.

TRIAL REGISTRATION

Clinical Trial Registry India: CTRI/2009/091/000531.

Prospective observational study to evaluate the clinical safety of the fixed-dose artemisinin-based combination Eurartesim® (dihydroartemisinin/piperaquine), in public health facilities in Burkina Faso, Mozambique, Ghana, and Tanzania

BACKGROUND

The World Health Organization recommends artemisinin-based combination (ACT) for the treatment of uncomplicated malaria. Post-licensure safety data on newly registered ACT is critical for evaluating their risk/benefit profile in malaria endemic countries. The clinical safety of the newly registered combination, Eurartesim®, following its introduction into the public health system in four African countries was assessed.

METHODS

This was a prospective, observational, open-label, non-comparative, longitudinal, multi-centre study using cohort event monitoring. Patients with confirmed malaria had their first dose observed and instructed on how to take the second and the third doses at home. Patients were contacted on day 5 ± 2 to assess adherence and adverse events (AEs). Spontaneous reporting of AEs was continued till day 28. A nested cohort who completed full treatment course had repeated electrocardiogram (ECG) measurements to assess effect on QTc interval.

RESULTS

A total of 10,925 uncomplicated malaria patients were treated with Eurartesim®. Most patients,95% (10,359/10,925), did not report any adverse event following at least one dose of Eurartesim®. A total of 797 adverse events were reported. The most frequently reported, by system organ classification, were infections and infestations (3. 24%) and gastrointestinal disorders (1. 37%). In the nested cohort, no patient had QTcF > 500 ms prior to day 3 pre-dose 3. Three patients had QTcF > 500 ms (509 ms, 501 ms, 538 ms) three to four hours after intake of the last dose. All the QTcF values in the three patients had returned to <500 ms at the next scheduled ECG on day 7 (470 ms, 442 ms, 411 ms). On day 3 pre- and post-dose 3, 70 and 89 patients, respectively, had a QTcF increase of ≥ 60 ms compared to their baseline, but returned to nearly baseline values on day 7.

CONCLUSION

Eurartesim® single course treatment for uncomplicated falciparum malaria is well-tolerated. QT interval prolongation above 500 ms may occur at a rate of three per 1,002 patients after the third dose with no association of any clinical symptoms. QT interval prolongation above 60 ms was detected in less than 10% of the patients without any clinical abnormalities.

Dihydroartemisinin-piperaquine failure associated with a triple mutant including kelch13 C580Y in Cambodia: an observational cohort study

BACKGROUND

Dihydroartemisinin-piperaquine has been adopted as first-line artemisinin combination therapy (ACT) for multidrug-resistant Plasmodium falciparum malaria in Cambodia because of few remaining alternatives. We aimed to assess the efficacy of standard 3 day dihydroartemisinin-piperaquine treatment of uncomplicated P falciparum malaria, with and without the addition of primaquine, focusing on the factors involved in drug resistance.

METHODS

In this observational cohort study, we assessed 107 adults aged 18-65 years presenting to Anlong Veng District Hospital, Oddar Meanchey Province, Cambodia, with uncomplicated P falciparum or mixed P falciparum/Plasmodium vivax infection of between 1000 and 200,000 parasites per μL of blood, and participating in a randomised clinical trial in which all had received dihydroartemisinin-piperaquine for 3 days, after which they had been randomly allocated to receive either primaquine or no primaquine. The trial was halted early due to poor dihydroartemisinin-piperaquine efficacy, and we assessed day 42 PCR-corrected therapeutic efficacy (proportion of patients with recurrence at 42 days) and evidence of drug resistance from the initial cohort. We did analyses on both the intention to treat (ITT), modified ITT (withdrawals, losses to follow-up, and those with secondary outcomes [eg, new non-recrudescent malaria infection] were censored on the last day of follow-up), and per-protocol populations of the original trial. The original trial was registered with ClinicalTrials.gov, number NCT01280162.

FINDINGS

Between Dec 10, 2012, and Feb 18, 2014, we had enrolled 107 patients in the original trial. Enrolment was voluntarily halted on Feb 16, 2014, before reaching planned enrolment (n=150) because of poor efficacy. We had randomly allocated 50 patients to primaquine and 51 patients to no primaquine groups. PCR-adjusted Kaplan-Meier risk of P falciparum 42 day recrudescence was 54% (95% CI 45-63) in the modified ITT analysis population. We found two kelch13 propeller gene mutations associated with artemisinin resistance--a non-synonymous Cys580Tyr substitution in 70 (65%) of 107 participants, an Arg539Thr substitution in 33 (31%), and a wild-type parasite in four (4%). Unlike Arg539Thr, Cys580Tyr was accompanied by two other mutations associated with extended parasite clearance (MAL10:688956 and MAL13:1718319). This combination triple mutation was associated with a 5·4 times greater risk of treatment failure (hazard ratio 5·4 [95% CI 2·4-12]; p<0·0001) and higher piperaquine 50% inhibitory concentration (triple mutant 34 nM [28-41]; non-triple mutant 24 nM [1-27]; p=0·003) than other infections had. The drug was well tolerated, with gastrointestinal symptoms being the most common complaints.

INTERPRETATION

The dramatic decline in efficacy of dihydroartemisinin-piperaquine compared with what was observed in a study at the same location in 2010 was strongly associated with a new triple mutation including the kelch13 Cys580Tyr substitution. 3 days of artemisinin as part of an artemisinin combination therapy regimen might be insufficient. Strict regulation and monitoring of antimalarial use, along with non-pharmacological approaches to malaria resistance containment, must be integral parts of the public health response to rapidly accelerating drug resistance in the region.

FUNDING

Armed Forces Health Surveillance Center/Global Emerging Infections Surveillance and Response System, Military Infectious Disease Research Program, National Institute of Allergy and Infectious Diseases, and American Society of Tropical Medicine and Hygiene/Burroughs Wellcome Fund.

Triazine–pyrimidine based molecular hybrids: synthesis, docking studies and evaluation of antimalarial activity

A series of novel triazine–pyrimidine hybrids have been synthesized and evaluated for their in vitro antimalarial activity.

Efficacy and safety of dihydroartemisinin-piperaquine for treatment of uncomplicated Plasmodium falciparum malaria in endemic countries: meta-analysis of randomised controlled studies

The present review aimed to synthesise available evidence on the efficacy of dihydroartemisinin-piperaquine (DP) in treating uncomplicated Plasmodium falciparum malaria in people living in malaria-endemic countries by performing a meta-analysis of relevant studies. We searched relevant studies in electronic data bases up to December 2011. Published results from randomised controlled trials (RCTs) comparing efficacy of DP with other artemisinin-based combination therapies (ACTs), or non-ACTs, or placebo were selected. The primary endpoint was 28-day and 42-day treatment failure. We identified 26 RCTs. Many of the studies included in the present review were of high quality. Overall, DP, artesunate-mefloquine (MAS3) and artemether-lumefentrine (AL) were equally effective for reducing the risk of recurrent parasitaemia. The PCR confirmed efficacy of DP (99.5%) and MAS3 (97.7%) at day 28 exceeded 90%; both are efficacious. Comparable efficacy was also found for DP (95.6%) and AL (94.3%). The present review has documented that DP is comparable to other currently used ACTs such as MAS3 and AL in treating uncomplicated falciparum malaria. The better safety profile of DP and once-daily dosage improves adherence and its fixed co-formulation ensures that both drugs are taken together. Our conclusion is that DP has the potential to become a first-line antimalarial drug.

Therapeutic efficacy and safety of dihydroartemisinin-piperaquine versus artesunate-mefloquine in uncomplicated Plasmodium falciparum malaria in India

BACKGROUND

Resistance in Plasmodium falciparum to commonly used anti-malarial drugs, especially chloroquine, is being increasingly documented in India. By 2007, the first-line treatment for uncomplicated malaria has been revised to recommend artemisinin-based combination therapy (ACT) for all confirmed P. falciparum cases.

OBJECTIVE

The objective of this study was to compare the efficacy, safety and tolerability between dihydroartemisinin-piperaquine (DP) and artesunate plus mefloquine (A + M) drug combinations in the treatment of uncomplicated P. falciparum malaria in India.

METHODS

Between 2006 and 2007, 150 patients with acute uncomplicated P. falciparum malaria were enrolled, randomized to DP (101) or A + M (49) and followed up for 63 days as part of an open-label, non-inferiority, randomized, phase III multicenter trial in Asia.

RESULTS

The heterogeneity analysis showed no statistically significant difference between India and the other countries involved in the phase III study, for both the PCR-corrected and uncorrected cure rates. As shown at the whole study level, both forms of ACT were highly efficacious in India. In fact, in the per protocol population, the 63-day cure rates were 100% for A + M and 98.8% for DP. The DP combination exerted a significant post-treatment prophylactic effect, and compared with A + M a significant reduction in the incidence of new infections for DP was observed (respectively 17.1% versus 7.5% of patients experienced new infection within follow up). Parasite and fever clearance was rapid in both treatment arms (median time to parasite clearance of one day for both groups). Both DP and A + M were well tolerated, with the majority of adverse events of mild or moderate severity. The frequencies of individual adverse events were generally similar between treatments, although the incidence of post treatment adverse events was slightly higher in patients who received A + M with respect to those treated with DP.

CONCLUSION

DP is a new ACT displaying high efficacy and safety in the treatment of uncomplicated P. falciparum malaria and could potentially be considered for the first-line treatment of uncomplicated falciparum malaria in India.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN 81306618.

pfmdr1 amplification is related to increased Plasmodium falciparum in vitro sensitivity to the bisquinoline piperaquine

The 4-aminoquinoline bisquinoline piperaquine is an important partner drug in one of the presently recommended artemisinin combination therapies. Recent clinical trials have confirmed its high efficacy in combination with dihydroartemisinin. Resistance to piperaquine alone has, however, been documented. Amplification in copy number of the Plasmodium falciparum multidrug resistance locus on chromosome 5, containing the pfmdr1 gene, has been shown to confer resistance to structurally unrelated antimalarials. Through the determination of the 50% inhibitory concentrations (IC(50)s) and IC(90)s for piperaquine and chloroquine in a set of 46 adapted P. falciparum cultures originating from the Thai-Burmese border, we have characterized the regions around the pfmdr1 gene and identified a significant association between the presence of pfmdr1 duplications and enhanced sensitivity to piperaquine (P = 0.005 for IC(50) and P = 0.002 for IC(90)) and chloroquine, reaching statistical significance at IC(90)s (P = 0.026). These results substantiate the potential importance of pfmdr1 copy number amplifications in the efficacy of the combination therapy piperaquine-dihydroartemisinin. It supports the rational use of 4-aminoquinolines and artemisinin-based compounds, as they independently select for mutually incompatible combinations of mutations.