Effectiveness of sulfadoxine–pyrimethamine plus amodiaquine and dihydroartemisinin–piperaquine for seasonal malaria chemoprevention in Uganda: a three-arm, open-label, non-inferiority and superiority, cluster-randomised, controlled trial

Abstract

Background

Seasonal malaria chemoprevention (SMC) with sulfadoxine–pyrimethamine combined with amodiaquine (SPAQ) effectively protects eligible children from malaria in areas of high and seasonal transmission. However, concerns about parasite resistance to sulfadoxine–pyrimethamine in East and Southern Africa necessitate evaluating alternative drug regimens. This study assessed the effectiveness of SPAQ and dihydroartemisinin–piperaquine for SMC in Uganda.

Methods

This three-arm, open-label, non-inferiority and superiority, cluster-randomised, controlled trial was conducted in Karamoja subregion, Uganda, among children aged 3–59 months and 6–59 months for SPAQ and dihydroartemisinin–piperaquine, respectively. Of 427 villages, 380 were randomly assigned (1:1) to the SPAQ group and dihydroartemisinin–piperaquine group, and 47 were assigned to the control group (no SMC). The superiority component compared the SPAQ and dihydroartemisinin–piperaquine groups with the control group, whereas the non-inferiority component compared the dihydroartemisinin–piperaquine group with the SPAQ group. The primary endpoint was confirmed malaria incidence using rapid diagnostic tests or microscopy. Survival analyses were done on an intention-to-treat basis (in all randomised participants), with adjustments made for covariate imbalances at baseline. Additionally, molecular markers associated with resistance to sulfadoxine–pyrimethamine and amodiaquine were analysed on 750 malaria-positive blood samples from children younger than 5 years before and after five SMC cycles. This trial was registered with ClinicalTrials.gov, NCT05323721, and has been completed.

Findings

During June 18–30, 2022, 3881 children were enrolled; 1755 in SPAQ, 1736 in dihydroartemisinin–piperaquine, and 390 in control villages. Of these children, 3629 were analysed. Incidence rates were 0·90 cases per 100 person-months in the SPAQ group, 0·80 cases per 100 person-months in the dihydroartemisinin–piperaquine group, and 18·26 cases per 100 person-months in the control group. SPAQ and dihydroartemisinin–piperaquine reduced malaria risk by 94% (hazard ratio [HR] 0·06 [95% CI 0·04–0·08]; p<0·001) and 96% (0·04 [0·03–0·06]; p<0·001), respectively. Based on the prespecified non-inferiority margin of 1·4, there was non-inferiority between the protective effectiveness of dihydroartemisinin–piperaquine and that of SPAQ (HR 0·90 [95% CI 0·58–1·39]). Prevalence of mutations linked to moderate (Plasmodium falciparum dihydrofolate reductase [PfDHFR] and P falciparum dihydropteroate synthetase reductase [PfDHPS]) and high (PfDHFR Ile164Leu and PfDHPS Ala581Gly) sulfadoxine–pyrimethamine resistance were more than 88% and less than 5%, respectively. Mutations associated with 4-aminoquinolone resistance (P falciparum multidrug resistance protein-1 [PfMDR1] Asp1246Tyr and PfMDR1 Asn86Tyr) were less than 1%. There was no significant increase in the prevalence of antifolate and artemisinin partial resistance-associated mutations, but a decrease was observed for key aminoquinoline resistance-associated alleles: P falciparum chloroquine resistance transporter protein Lys76Thr, P falciparum multidrug resistance protein Asn86Tyr, and PfMDR1 Asp1246Tyr (p<0·001). No serious or fatal adverse events were reported.

Interpretation

SPAQ and dihydroartemisinin–piperaquine effectively reduced malaria in children younger than 5 years, with no safety concerns. There was no evidence of resistance selection by SMC. Although these findings support SPAQ-based SMC in Eastern and Southern Africa, ongoing resistance surveillance and efficacy monitoring are essential for sustained impact.

Funding

GiveWell.

Translation

For the Swahili translation of the abstract see Supplementary Materials section.