According to the World Health Organization, around 240 million people had malaria in 2020, of which 627, 000 died. While a vaccine for malaria is available, its efficacy varies and thus underlines the necessity for new interventions that offer a high level of protection.
For the current study, researchers at the National Institutes of Health's (NIH) Vaccine Research Center (VRC) developed L9LS, a lab-made version of a naturally occurring antibody called L9, which was derived from the blood of a volunteer who had previously received an investigational malaria vaccine. The antibody works by neutralizing parasites in the skin and blood before they infect liver cells.
L9LS is similar to another anti-malarial antibody known as CIS43LS, also developed by the VRC. However, L9LS is two to three times more potent and can be administered via subcutaneous injection as opposed to intravenous infusion.
In the current study, researchers conducted a Phase 1 trial that involved 6 controls and 18 volunteer participants who received 1mg, 5mg, or 20mg per kg of body weight of L9LS intravenously or subcutaneously. Between two to six weeks after receiving the vaccine, the inoculated volunteers and controls were bitten five times on their forearms by mosquitoes carrying the malaria parasite.
In the end, the researchers found that L9LS fully protected 88% of the inoculated volunteers. Of those who contracted malaria, one received 1mg per kg of body weight of L9LS, and the other: 5mg. Meanwhile, all six controls developed malaria. All participants who became infected were treated without complications.
"This is the first demonstration that a monoclonal antibody can provide protection when given by the subcutaneous route, with important implications for widespread clinical use and reaching the goal of eliminating malaria," said Robert Seder, M.D., chief of the Cellular Immunology Section in the VRC, who led the development of L9LS. "We look forward to results in larger field studies that will help establish an effective dose."