The Study Group was formed in June 2015. The Study Group closed to new participants in December 2015. The analysis was completed between 2016–2018 and the group published in January 2019. WWARN K13 Genotype-Phenotype Study Group. Association of mutations in the Plasmodium falciparum Kelch13 gene (Pf3D7_1343700) with parasite clearance rates after artemisinin-based treatments—a WWARN individual patient data meta-analysis. BMC Medicine. January 17, 2019.

Artemisinin-based combination therapies (ACTs) are now the mainstay for uncomplicated malaria treatment in most endemic areas and have substantially contributed to the dramatic decrease of malaria incidence and mortality over the last decade (WHO 2014). However, the emergence of Plasmodium falciparum resistance to artemisinin in the Mekong sub-region threatens to jeopardise those gains (Dondorp et al. 2009). Resistance to artemisinin has been associated with delayed parasite clearance after ACT or artemisinin monotherapy treatment and a variety of mutations in the propeller region of the K13 gene (Ariey et al. 2014).

K13 mutant alleles are now very widely distributed in the Mekong region (Ashley et al. 2014; Tun et al. 2015; Miotto et al. 2015).  Parasites with some of these mutations have spread locally, but also have emerged independently in different locations (Takala-Harrison et al. 2014; Miotto et al. 2015). Gene exchange experiments have confirmed that some of the K13 mutations found in parasites from the Mekong region can confer protection against artemisinin exposure in the laboratory (Witkowski et al. 2013; Straimer et al. 2014).

In addition, molecular surveillance alone has identified K13 mutants in many sites, but without correlation of these alleles with a parasite phenotype, their significance is not yet known. Moreover, the prevalence and role of K13-propeller mutations are poorly known in sub-Saharan Africa. The confirmation that a particular K13 allele does encode the expected parasite phenotype requires either clinical investigation of the parasite clearance (Ariey et al. 2014; Ashley et al. 2014; Huang et al. 2015) or in vitro assessment of the decreased susceptibility of the parasite in the specialized ring-stage survival assay (RSA) (Witkowski et al. 2013). A number of studies assessing the relationship between the K13 molecular markers and delayed parasite clearance have been published recently; this pooled analysis collated published and unpublished studies to explore the relationships between identified K13 mutant alleles and delayed parasite clearance.

• To assess the relationship between K13 mutations and delayed parasite clearance 

• Results of K13 genotyping

AND

• Clinical efficacy studies of uncomplicated falciparum malaria in Asia and Africa
• Patients treated with either an ACT or artemisinin monotherapy
• Repeated measure of parasitaemia in the first days of treatment at least every 12 hours allowing the calculation of parasite clearance half life

• Patient follow up for a minimum of 28 days post treatment
• PCR genotyping to distinguish reinfection and recrudescence
• Mg/Kg dosing protocol
• Weight of the patient

After upload to the WWARN Data Repository, WWARN standardised clinical data sets according to the WWARN Clinical Data Management and Statistical Analytical Plan and pool these into a single database of quality-assured individual patient data.

The parasite clearance curve was determined using the WWARN parasite clearance estimator tool (PCE), and delayed parasite clearance was defined as clearance half-life ≥ 5 hours.

Non-synonymous mutations in the propeller region > codon 440 in the K13 gene will be included in the analysis.

The Study Group comprised participating investigators who contributed relevant data sets to the pooled analysis. Data sets remain the property of the investigator. The Study Group collectively made decisions with respect to including additional studies, data analysis and plans for publication, in line with the WWARN Publication Policy. The Study Group identified one or two people who coordinated activities including data analysis and drafting of publications and reports for group review. The WWARN statistician(s) were be responsible for statistical analyses.

For further information, contact Sabina Dahlstrom-Otienoburu - clinical@wwarn.org.

Ariey, F. et al., 2014. A molecular marker of artemisinin-resistant Plasmodium falciparum malaria. Nature, 505(7481), pp.50–5.

Ashley, E.A. et al., 2014. Spread of Artemisinin Resistance in Plasmodium falciparum Malaria. New England Journal of Medicine, 371(5), pp.411–423.

Dondorp, A.M. et al., 2009. Artemisinin resistance in Plasmodium falciparum malaria. N Engl J Med, 361(5), pp.455–467.

Cooper RA et al.2015. Lack of Artemisinin Resistance in Plasmodium falciparum in Uganda Based on Parasitological and Molecular Assays. Antimicrob Agents Chemother, 59(8), pp.5061-5064.

Huang, F. et al., 2015. A single mutation in K13 predominates in Southern China and is associated with delayed clearance of Plasmodium falciparum following artemisinin treatment. The Journal of infectious diseases.

Miotto, O. et al., 2015. Genetic architecture of artemisinin-resistant Plasmodium falciparum. Nature Genetics, 47(3), pp.226–34.

Ouattara A, et al. 2015.  Polymorphisms in the K13-Propeller Gene in Artemisinin-Susceptible Plasmodium falciparum Parasites from Bougoula-Hameau and Bandiagara, Mali. Am J Trop Med Hyg, 92(6), pp.1202-1206.

Straimer, J. et al., 2014. K13-propeller mutations confer artemisinin resistance in Plasmodium falciparum clinical isolates. Science, 347(6220), pp.428–31.

Takala-Harrison, S. et al., 2014. Independent Emergence of Artemisinin Resistance Mutations Among Plasmodium falciparum in Southeast Asia. The Journal of infectious diseases, 211(5), pp.670–9.

Tun, K.M. et al., 2015. Spread of artemisinin-resistant Plasmodium falciparum in Myanmar: a cross-sectional survey of the K13 molecular marker. The Lancet Infectious Diseases, 15(4), pp.415–21.

WHO, 2014. World malaria report 2014, Geneva.

Witkowski, B. et al., 2013. Reduced artemisinin susceptibility of Plasmodium falciparum ring stages in western Cambodia. Antimicrob Agents Chemother, 57(2), pp.914–923.

WWARN K13 Genotype-Phenotype Study Group. Association of mutations in the Plasmodium falciparum Kelch13 gene (Pf3D7_1343700) with parasite clearance rates after artemisinin-based treatments—a WWARN individual patient data meta-analysis. BMC Medicine. January 17, 2019.