A single injection that could provide protection against malaria for months has been shown to be effective and safe in a small early clinical trial of adults.
The injection, which contains monoclonal antibodies, would be intended primarily for infants and children in countries with the highest malaria transmission, say the team that conducted the trial. These young children are at the highest risk of dying from severe malaria.
In the clinical trial, 15 of 17 participants who received the monoclonal antibodies did not become infected after being exposed to malarial mosquitoes in the lab, researchers report in the August 4 issue New England Journal of Medicine. All six people who did not receive the drug developed infections.
The clinical trial tested different doses and administered the drug intravenously or as an injection. Based on a computer model of how the body absorbs, distributes and eliminates the drug, the researchers estimate that one injection can protect against malaria for six months.
“What we’ve always been looking for is some kind of intervention that reliably prevents infection for as long as possible,” says Miriam Laufer, a pediatric infectious disease physician and director of the Malaria Research Program at the University of Maryland. . Baltimore School of Medicine.
The ideal, Laufer says, would be a highly effective vaccine that provides years and years of protection. A new malaria vaccine has been available recently, but only modestly protects against the disease, and that protection wears off quickly (Serial number: 12/22/21). The vaccine requires four injections.
Monoclonal antibodies could provide an option that requires only one injection, once a year. More research will be needed to see how well malaria antibodies work outside the laboratory and how cost-effective the injection is.
The injection of monoclonal antibodies would not rule out the need for other prevention strategies, says Laufer, who was not involved in the new study. But it could be “one of the easiest interventions in terms of minimal contact with the health care system, with good benefits.”
What’s appealing, he says, “is the possibility that children, even very young children, can be given an injection [of] pre-made antibodies that could last six months or more and protect them during the rainy season.” That once-a-season vaccine would be useful in West African countries, where malaria transmission only occurs during the rainy season.
Malaria sickened an estimated 241 million people and killed 627,000 worldwide in 2020. Most of those deaths occurred in sub-Saharan Africa in children under 5 years of age. These young children have not had a chance to develop immunity to the disease and are more likely to die if severe malaria develops.
Reducing the spread of malaria includes measures to control mosquitoes, such as using insecticide-treated bed nets or fumigation to kill mosquitoes indoors, as well as infection prevention, such as taking antimalarial drugs at regular intervals . In October 2021, the World Health Organization also recommended the new vaccine, which in clinical trials reduced cases of malaria and severe malaria by 36% after four years of follow-up.
Monoclonal antibodies are a laboratory version of antibodies, the proteins produced by the immune system in response to a vaccine or natural infection. Monoclonal means that it contains clones or copies of a particular antibody.
The antibody tested in the clinical trial attaches to a protein on the surface of sporozoites, the form of the malaria parasite that enters the body after the bite of an infected mosquito, and prevents the parasites from infecting the liver.
The new monoclonal antibody features improvements over an earlier version developed by the same research team. The new version binds more tightly to the malaria parasite-specific protein. It also has a fit that prevents it from breaking down too quickly on the body. This increases its half-life in the blood (the time it takes for half of the drug to break down) to 56 days, nearly three times longer than its predecessor.
Two clinical trials are planned to test how well the drug protects children in places where malaria is spreading. A trial in Mali, where malaria transmission is seasonal, will study the efficacy of the injection for seven months. Another trial in Kenya, one of the East African countries where malaria spreads throughout the year, will test how well the injection works while following children for a year. Those studies will also help determine the best dose for children.