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.