Clinical and In Vitro Resistance of Plasmodium falciparum to Artesunate-Amodiaquine in Cambodia

Abstract

Background Artesunate-amodiaquine is a potential therapy for uncomplicated malaria in Cambodia. Methods Between September 2016 and January 2017, artesunate-amodiaquine efficacy and safety were evaluated in a prospective, open-label, single-arm observational study at health centers in Mondulkiri, Pursat and Siem Reap Provinces, Cambodia. Adults and children with microscopically-confirmed Plasmodium falciparum malaria received oral artesunate-amodiaquine once daily for three days plus single-dose primaquine, with follow-up on Days 7, 14, 21 and 28. The primary outcome was Day-28 PCR-adjusted adequate clinical and parasitological response (ACPR). An amodiaquine parasite survival assay (AQSA) was developed and applied to whole genome sequencing results to evaluate potential amodiaquine resistance molecular markers. Results In 63 patients, Day-28 PCR-adjusted ACPR was 81.0% (95% confidence interval [CI], 68.9–88.7). Day 3 parasite positivity rate was 44.4% (28/63; 95%CI, 31.9–57.5). All 63 isolates had the K13(C580Y) marker for artemisinin resistance; 79.4% (50/63) had Pfpm2 amplification. The AQSA resistance phenotype (≥45% parasite survival) was expressed in 36.5% (23/63) of isolates and was significantly associated with treatment failure (P = 0.0020). Pfmdr1 mutant haplotypes were N86/184F/D1246 and Pfcrt was CVIET or CVIDT at positions 72–76. Additional Pfcrt mutations were not associated with amodiaquine resistance, but the G353V mutant allele was associated with ACPR compared to Pfmdr1 haplotypes harboring F1068L or S784L/R945P mutations (P = 0.030 and P = 0.0004, respectively). Conclusions For uncomplicated falciparum malaria in Cambodia, artesunate-amodiaquine had inadequate efficacy owing to amodiaquine-resistant P. falciparum. Amodiaquine resistance was not associated with previously identified molecular markers.

Artemisinin exposure at the ring or trophozoite stage impacts Plasmodium falciparum sexual conversion differently

“…This in turn prevents ART activation, resulting in resistance of early rings to the drug ( Birnbaum et al, 2020 ; Yang et al, 2019 ). Nowadays, ART resistance is frequently accompanied by simultaneous resistance to partner drugs such as mefloquine, piperaquine, or amodiaquine, resulting in high rates of treatment failure and limiting treatment options ( Mairet-Khedim et al, 2020 ; Phyo et al, 2016 ; van der Pluijm et al, 2019 ).…”

To what extent are the antimalarial markets in African countries ready for a transition to triple artemisinin-based combination therapies?

“…Artemisinin-based combination therapies (ACTs) are the global first-line antimalarial therapies for the treatment of uncomplicated falciparum malaria [ 1 ]. A worrying development is the emergence and spread of Plasmodium falciparum parasites resistant to both artemisinin and partner drugs, compromising ACT efficacy in large areas of Southeast Asia [ 2 – 5 ]. An even more significant threat is the risk of multidrug resistance spreading further throughout Asia and to the African continent, where most of the malaria burden is clustered [ 6 ].…”

Cross-resistance of the chloroquine-derivative AQ-13 with amodiaquine in Cambodian Plasmodium falciparum isolates

“…However, resistance to ACTs is occurring as several mutations in pfcrt participate in the resistance to DHA-PIP 3–5 while a mutation in pfmdr1 seems to be associated with AS-AQ treatment failures. 6 Drug-failure to ACTs in the Greater Mekong Subregion (GMS), notably with DHA-PIP, urges the development of new combinations to control and eradicate malaria. AQ-13 is a short chain chloroquine derivative that has been developed to circumvent chloroquine resistance.…”

“… 8 However, we have recently shown that the clinical efficacy of AS-AQ precludes its implementation in Cambodia. 6 …”