Antimalarial drug efficacy and resistance in malaria-endemic countries in HANMAT-PIAM_net countries of the Eastern Mediterranean Region 2016-2020: Clinical and genetic studies.

INTRODUCTION: The World Health Organization recommends regular monitoring of the efficacy of nationally recommended antimalarial drugs. We present the results of studies on the efficacy of recommended antimalarials and molecular markers of artemisinin and partner resistance in Afghanistan, Pakistan, Somalia, Sudan and Yemen. METHODS: Single-arm prospective studies were conducted to evaluate the efficacy of artesunate-sulfadoxine-pyrimethamine (ASSP) in Afghanistan and Pakistan, artemether-lumefantrine (AL) in all countries, or dihydroartemisinin-piperaquine (DP) in Sudan for the treatment of Plasmodium falciparum. The efficacy of chloroquine (CQ) and AL for the treatment of Plasmodium vivax was evaluated in Afghanistan and Somalia, respectively. Patients were treated and monitored for 28 (CQ, ASSP and AL) or 42 (DP) days. Polymerase chain reaction (PCR)-corrected cure rate and parasite positivity rate at Day 3 were estimated. Mutations in the P. falciparum kelch 13 (Pfk13) gene and amplifications of plasmepsin (Pfpm2) and multidrug resistance-1 (Pfmdr-1) genes were also studied. RESULTS: A total of 1680 (249 for ASSP, 1079 for AL and 352 for DP) falciparum cases were successfully assessed. A PCR-adjusted ASSP cure rate of 100% was observed in Afghanistan and Pakistan. For AL, the cure rate was 100% in all but four sites in Sudan, where cure rates ranged from 92.1% to 98.8%. All but one patient were parasite-free at Day 3. For P. vivax, cure rates were 98.2% for CQ and 100% for AL. None of the samples from Afghanistan, Pakistan and Yemen had a Pfk13 mutation known to be associated with artemisinin resistance. In Sudan, the validated Pfk13 R622I mutation accounted for 53.8% (14/26) of the detected non-synonymous Pfk13 mutations, most of which were repeatedly detected in Gadaref. A prevalence of 2.7% and 9.3% of Pfmdr1 amplification was observed in Pakistan and Yemen, respectively. CONCLUSION: High efficacy of ASSP, AL and DP in the treatment of uncomplicated falciparum infection and of CQ and AL in the treatment of P. vivax was observed in the respective countries. The repeated detection of a relatively high rate of Pfk13 R622I mutation in Sudan underscores the need for close monitoring of the efficacy of recommended ACTs, parasite clearance rates and Pfk13 mutations in Sudan and beyond. Registration numbers of the trials: ACTRN12622000944730 and ACTRN12622000873729 for Afghanistan, ACTRN12620000426987 and ACTRN12617001025325 for Pakistan, ACTRN12618001224213 for Somalia, ACTRN12617000276358, ACTRN12622000930785 and ACTRN12618001800213 for Sudan and ACTRN12617000283370 for Yemen.

Artemisinin-based combination therapy (ACT) and drug resistance molecular markers: A systematic review of clinical studies from two malaria endemic regions - India and sub-Saharan Africa.

Artemisinin-based combination therapies (ACT) are currently used as a first-line malaria therapy in endemic countries worldwide. This systematic review aims at presenting the current scenario of drug resistance molecular markers, either selected or involved in treatment failures (TF) during in vivo ACT efficacy studies from sub-Saharan Africa (sSA) and India. Eight electronic databases were comprehensively used to search relevant articles and finally a total of 28 studies were included in the review, 21 from sSA and seven from India. On analysis, Artemether + lumefantrine (AL) and artesunate + sulfadoxine-pyrimethamine (AS + SP) are the main ACT in African and Indian regions with a 28-day efficacy range of 54.3-100% for AL and 63-100% for AS + SP respectively. It was observed that mutations in the Pfcrt (76T), Pfdhfr (51I, 59R, 108N), Pfdhps (437G) and Pfmdr1 (86Y, 184F, 1246Y) genes were involved in TF, which varied with respect to ACTs. Based on studies that have genotyped the Pfk13 gene, the reported TF cases, were mainly linked with mutations in genes associated with resistance to ACT partner drugs; indicating that the protection of the partner drug efficacy is crucial for maintaining the efficacy of ACT. This review reveals that ACT are largely efficacious in India and sSA despite the fact that some clinical efficacy and epidemiological studies have reported some validated mutations (i.e., 476I, 539T and 561H) in circulation in these two regions. Also, the role of PfATPase6 in ART resistance is controversial still, while P. falciparum plasmepsin 2 (Pfpm2) in piperaquine (PPQ) resistance and dihydroartemisinin (DHA) + PPQ failures is well documented in Southeast Asian countries but studied less in sSA. Hence, there is a need for continuous molecular surveillance of Pfk13 mutations for emergence of artemisinin (ART) resistance in these countries.

Plasmodium falciparum Genetic Diversity in Continental Equatorial Guinea before and after Introduction of Artemisinin-Based Combination Therapy.

Efforts to control malaria may affect malaria parasite genetic variability and drug resistance, the latter of which is associated with genetic events that promote mechanisms to escape drug action. The worldwide spread of drug resistance has been a major obstacle to controlling Plasmodium falciparum malaria, and thus the study of the origin and spread of associated mutations may provide some insights into the prevention of its emergence. This study reports an analysis of P. falciparum genetic diversity, focusing on antimalarial resistance-associated molecular markers in two socioeconomically different villages in mainland Equatorial Guinea. The present study took place 8 years after a previous one, allowing the analysis of results before and after the introduction of an artemisinin-based combination therapy (ACT), i.e., artesunate plus amodiaquine. Genetic diversity was assessed by analysis of the Pfmsp2 gene and neutral microsatellite loci. Pfdhps and Pfdhfr alleles associated with sulfadoxine-pyrimethamine (SP) resistance and flanking microsatellite loci were investigated, and the prevalences of drug resistance-associated point mutations of the Pfcrt, Pfmdr1, Pfdhfr, and Pfdhps genes were estimated. Further, to monitor the use of ACT, we provide the baseline prevalences of K13 propeller mutations and Pfmdr1 copy numbers. After 8 years, noticeable differences occurred in the distribution of genotypes conferring resistance to chloroquine and SP, and the spread of mutated genotypes differed according to the setting. Regarding artemisinin resistance, although mutations reported as being linked to artemisinin resistance were not present at the time, several single nucleotide polymorphisms (SNPs) were observed in the K13 gene, suggesting that closer monitoring should be maintained to prevent the possible spread of artemisinin resistance in Africa.