Lab-Made Antibodies Protect Malaria-Exposed Adults for Six Months in Mali Trial

In the villages of Kalifabougou and Torodo in Mali, during malaria season, people are bitten by infected mosquitoes an average of twice a day, according to earlier research. It was there that scientists tested whether a single infusion of lab-made antibodies could shield adults from the disease for months at a time.

The results, published Monday in the New England Journal of Medicine and presented at a medical meeting in Seattle, were encouraging. The study enrolled 330 adults in Mali. Each received one of two doses of the experimental antibody or a dummy infusion. For 24 weeks, all were tested for malaria infection every two weeks, and anyone who fell ill was treated.

Blood tests found infections in 20 people who received the higher dose, 39 who received the lower dose, and 86 who received the placebo. Measured against the placebo group, the higher dose was 88% effective and the lower dose 75% effective. The findings show protection lasting at least six months, which could cover the several months of a typical malaria season.

The antibody was developed by researchers at the U.S. National Institutes of Health, starting from an antibody taken from a volunteer who had received a malaria vaccine. It works by interrupting the parasite's life cycle. The parasite spreads through mosquito bites, and the antibody targets immature parasites before they reach the liver, where they would mature and multiply.

The approach differs from vaccination. A vaccine relies on the body to produce enough infection-blocking antibodies on its own. This trial supplied a large dose of those antibodies directly. That matters because the first authorized malaria vaccine, which the World Health Organization is now rolling out for children, is about 30% effective and requires four doses. "The available vaccine doesn't protect enough people," said Dr. Kassoum Kayentao of the University of Sciences, Techniques and Technologies in Bamako, who helped lead the study.

The stakes are large. Malaria killed more than 620,000 people in 2020 and sickened 241 million, mainly children under 5 in Africa.

There are practical limits. The antibody was delivered by IV, which is difficult to do at large scale. The same scientists have an easier-to-administer injectable version in early testing in infants, children and adults, and the Mali results bode well for it. Cost remains uncertain, though one estimate suggests the antibodies could be given for as little as $5 per child per malaria season.

Researchers envision using the antibodies alongside existing tools such as malaria pills, mosquito nets and vaccines rather than replacing them. Lab-made antibodies are already used to treat cancer, autoimmune diseases and COVID-19, noted Dr. Johanna Daily of Albert Einstein College of Medicine in New York, who was not involved in the study. "The good news is now we have another, immune-based therapy to try to control malaria," she said.

The next results to watch will come from the injectable version now in early testing, since that form is the one that could realistically reach people at scale.