The Impact of pfmdr1 Gene Copy Number on the Efficacy of Dihydroartemisinin–Piperaquine in Treating Malaria in West Sumba and Kupang Districts, East Nusa Tenggara, Indonesia

The efficacy of antimalarial treatment, particularly artemisinin‐based combination therapy (ACT), continues to face persistent threats due to the development of drug resistance in Plasmodium falciparum . Although artemisinin derivatives remain effective, ACT regimen failure often results from decreased efficacy of the companion drug. Therefore, robust molecular surveillance focusing on genetic markers associated with companion drug resistance is essential to maintain global efficacy. The combination of dihydroartemisinin–piperaquine (DHA‐PPQ) has long been used as first‐line therapy and has proven effective; however, reports of resistance to piperaquine (PPQ) in Southeast Asia are cause for concern. The study is aimed at evaluating copy number variation (CNV) of the Plasmodium falciparum multidrug resistance-1 ( Pfmdr1 ) gene as part of a descriptive molecular surveillance approach in East Nusa Tenggara, Indonesia. A total of 41 dried blood spot (DBS) samples from patients with falciparum malaria treated with DHA‐PPQ were analyzed. The DNA extraction was performed using the QIAamp DNA Mini Kit, and CNV of the Pfmdr1 gene was determined by real‐time PCR. The phenotypes of all 41 patients showed a good treatment response, with 100% adequate clinical and parasitological response (ACPR) on Day 42. Analysis of the Pfmdr1 gene CNV identified 36 isolates (87.81%) with a single copy and 5 isolates (12.19%) with multiple copies. These findings indicate genetic variation related to selective pressure against PPQ. While DHA‐PPQ remains clinically effective in East Nusa Tenggara for now, the presence of these genetic markers necessitates a proactive surveillance strategy to detect shifts in drug sensitivity before widespread clinical failure occurs.