Artemether–lumefantrine with or without single-dose primaquine and sulfadoxine–pyrimethamine plus amodiaquine with or without single-dose tafenoquine to reduce Plasmodium falciparum transmission: a phase 2, single-blind, randomised clinical trial in Ouelessebougou, Mali

Background

Artemether–lumefantrine is widely used for uncomplicated Plasmodium falciparum malaria; sulfadoxine–pyrimethamine plus amodiaquine is used for seasonal malaria chemoprevention. We aimed to determine the efficacy of artemether–lumefantrine with and without primaquine and sulfadoxine–pyrimethamine plus amodiaquine with and without tafenoquine for reducing gametocyte carriage and transmission to mosquitoes.

Methods

In this phase 2, single-blind, randomised clinical trial conducted in Ouelessebougou, Mali, asymptomatic individuals aged 10–50 years with P falciparum gametocytaemia were recruited from the community and randomly assigned (1:1:1:1) to receive either artemether–lumefantrine, artemether–lumefantrine with a single dose of 0·25 mg/kg primaquine, sulfadoxine–pyrimethamine plus amodiaquine, or sulfadoxine–pyrimethamine plus amodiaquine with a single dose of 1·66 mg/kg tafenoquine. All trial staff other than the pharmacist were masked to group allocation. Participants were not masked to group allocation. Randomisation was done with a computer-generated randomisation list and concealed with sealed, opaque envelopes. The primary outcome was the median within-person percent change in mosquito infection rate in infectious individuals from baseline to day 2 (artemether–lumefantrine groups) or day 7 (sulfadoxine–pyrimethamine plus amodiaquine groups) after treatment, assessed by direct membrane feeding assay. All participants who received any trial drug were included in the safety analysis. This study is registered with ClinicalTrials.gov, NCT05081089.

Findings

Between Oct 13 and Dec 16, 2021, 1290 individuals were screened and 80 were enrolled and randomly assigned to one of the four treatment groups (20 per group). The median age of participants was 13 (IQR 11–20); 37 (46%) of 80 participants were female and 43 (54%) were male. In individuals who were infectious before treatment, the median percentage reduction in mosquito infection rate 2 days after treatment was 100·0% (IQR 100·0–100·0; n=19; p=0·0011) with artemether–lumefantrine and 100·0% (100·0–100·0; n=19; p=0·0001) with artemether–lumefantrine with primaquine. Only two individuals who were infectious at baseline infected mosquitoes on day 2 after artemether–lumefantrine and none at day 5. By contrast, the median percentage reduction in mosquito infection rate 7 days after treatment was 63·6% (IQR 0·0–100·0; n=20; p=0·013) with sulfadoxine–pyrimethamine plus amodiaquine and 100% (100·0–100·0; n=19; p<0·0001) with sulfadoxine–pyrimethamine plus amodiaquine with tafenoquine. No grade 3–4 or serious adverse events occurred.

Interpretation

These data support the effectiveness of artemether–lumefantrine alone for preventing nearly all mosquito infections. By contrast, there was considerable post-treatment transmission after sulfadoxine–pyrimethamine plus amodiaquine; therefore, the addition of a transmission-blocking drug might be beneficial in maximising its community impact.

Funding

Bill & Melinda Gates Foundation.