Pyronaridine-Artesunate (Pyramax) for Treatment of Artemisinin- and Piperaquine-Resistant Plasmodium falciparum in the Central Highlands of Vietnam

Abstract

The rise in Plasmodium falciparum resistance to dihydroartemisinin-piperaquine in Vietnam justifies the need to evaluate alternative artemisinin-based combination therapies. Between July 2018 and October 2019, a single-arm trial of pyronaridine-artesunate (Pyramax, PA) was conducted in Dak Nong province, Vietnam. PA (3-day course) was administered to adults and children infected with P. falciparum. PA was well tolerated by the participants. The proportion of patients with Day 42 PCR-corrected adequate clinical and parasitological response was 95.2% (95% confidence interval [CI], 82.3 to 98.8, n = 40/42) for treating falciparum malaria. The median parasite clearance half-life was 6.7 h (range, 2.6 to 11.9) and the median parasite clearance time was 72 h (range, 12 to 132) with 44.9% (22/49) of patients having positive blood films at 72 h. The two patients that recrudesced had comparable Day 7 blood pyronaridine concentrations (39.5 and 39.0 ng/ml) to the 40 patients who did not recrudesce (median 43.4 ng/ml, 95% CI, 35.1 to 54.9). Ring-stage and piperaquine survival assays revealed that of the 29 P. falciparum isolates collected from the patients before PA treatment, 22 (75.9%) had reduced susceptibility to artemisinins and 17 (58.6%) were resistant to piperaquine. Genotyping confirmed that 92.0% (46/50) of falciparum patients were infected with parasites bearing the Pfkelch13 C580Y mutation associated with artemisinin resistance. Of these, 56.0% (28/50) of the isolates also had multiple copies of the plasmepsin 2/3 genes responsible for piperaquine resistance. Overall, PA was effective in treating P. falciparum in the Central Highlands of Vietnam. (This study has been registered at AustralianClinicalTrials.gov.au under trial ID ACTRN12618001429246.).

Keywords: Central Highlands; Pfcrt; Pfkelch13; Pfmdr1; Plasmodium falciparum; Pyramax; Vietnam; antimalarial drug resistance; dihydroartemisinin; exo-E415G; piperaquine; plasmepsin 2/3; pyronaridine; pyronaridine-artesunate.

FIG 1

Provincial map of Vietnam with Dak Nong province highlighted in red (A). District map of Dak Nong province (B). Locations of study sites, Dak Drong Commune in Cu Jut District and Thuan An Commune in Dak Mil District, are indicated by arrows on district maps (C). (Map images courtesy of Gerard Kelly.)

FIG 2

Primary efficacy outcome. The Kaplan-Meier survival analysis of the PCR-adjusted adequate clinical and parasitological response (ACPR) over 42 days after pyronaridine-artesunate treatment of P. falciparum malaria across both Dak Drong and Thuan An communes (overall analysis).

FIG 3

Prevalence (values shown above bars) of molecular markers associated with Plasmodium falciparum antimalarial drug resistance in blood samples collected from patients in Dak Drong and Thuan An communes, Dak Nong province, Vietnam, before pyronaridine-artesunate (Pyramax) treatment.

FIG 4

Survival rates (%) at 72 h for ring-stage survival assay (RSA) (left) and piperaquine survival assay (PSA) (right) of Plasmodium falciparum isolates (n = 29) collected from patients before pyronaridine-artesunate (Pyramax) treatment. The RSA survival rate ranged between 0.0% and 7.3% for the 29 isolates, with seven isolates sensitive to DHA (range, 0.0%–0.8%; <1% cutoff) and 22 isolates resistant to DHA (range, 1.0%–7.3%; ≥1% cutoff). The PSA survival rates varied between 1.9% and 55.7% for the 29 isolates, with 12 isolates sensitive to PPQ (range, 1.9%–8.6%; <10% cutoff) and 17 isolates were resistant to PPQ (range, 11.4%–55.7%; ≥10% cutoff). The lines indicate mean values, with 95% CI values and the dashed lines are the drug resistance survival rate cutoff. VPA02 and VPA15 are isolates collected from patients who subsequently recrudesced.

FIG 5

Plasma concentrations of artesunate (AS) and dihydroartemisinin (DHA) at 1 h after the last dose on Day 3, as well as blood concentrations of pyronaridine (PRN) at Day 7 after commencement of pyronaridine-artesunate (Pyramax) treatment. Circles with black borders represent respective drug concentrations in VPA02 participant and a black half-filled triangle represents PRN concentration in VPA15 participant, the two patients who recrudesced. Plasma concentrations of AS and DHA were not available for VPA15.