Key takeaways:

• One dose of a monoclonal antibody was up to 77% effective against clinical malaria in children.
• A single dose was up to 70% effective against Plasmodium falciparum infection.

One subcutaneous dose of an experimental monoclonal antibody protected children from infection and clinical malaria during a 6-month malaria season in Mali, according to phase 2 results published in The New England Journal of Medicine.

Scientists have made recent strides against malaria, including the licensing of the first two vaccines. Evidence has also showed that a monoclonal antibody (mAb) can protect adults from malaria.

The new study tested an mAb called L9LS, which is more potent than the mAb tested among adults in the trial linked above. L9LS was also previously tested among adults in a small phase 1 trial, which identified no safety concerns, according to results published in 2022.

“A long-acting monoclonal antibody delivered at a single health care visit that rapidly provides high-level protection against malaria in these vulnerable populations would fulfill an unmet public health need,” Jeanne M. Marrazzo, MD, MPH, director of the National Institute of Allergy and Infectious Diseases, said in a press release.

For the new trial, researchers enrolled 225 children aged between 6 to 10 years and randomly assigned groups of 75 receive either 150 mg of L9LS, 300 mg of L9LS or a placebo.

The efficacy endpoint was presence of Plasmodium falciparum infection, as detected on blood smear performed at least every 2 weeks for 24 weeks.

According to the researchers, the efficacy of L9LS against P. falciparum infection compared with placebo was 66% (adjusted 95% CI, 45%-79%) with the 150 mg dose and 70% (adjusted 95% CI, 50%-82%) with the 300 mg dose. Against clinical malaria, efficacy was 67% (adjusted 95% CI, 39%-82%) with the 150 mg dose and 77% (adjusted 95% CI, 55%-89%) with the 300 mg dose.

During the study period, 81% of the children in the placebo group were infected with P. falciparum, compared with 48% in the 150 mg group and 40% in the 300 mg group.

The researchers did not identify any safety concerns over the course of the trial.

In a related editorial, Trevor Mundel, MD, PhD, president of global health at the Bill & Melinda Gates Foundation, called the results “promising” and said further improvements will be needed for mAbs to have “a broad effect in reducing the malaria burden.”

“The success of monoclonal antibodies will also be highly dependent on innovation that brings us beyond the status quo of costs of manufacturing goods, cold-chain requirements, and the delivery needs of health care systems,” Mundel wrote. “Trials that not only provide clinical insight but also show operational feasibility and the potential for cost-effective scale would provide a compelling argument for the acceleration of development and prequalification of this new class of product.”