New York, Aug 5 (IANS): Single-dose of a new monoclonal antibody (mAb) has shown to be safe and highly protective in adults exposed to the malaria parasite, according to results of Phase 1 clinical trial.

Malaria is a mosquito-borne disease caused by Plasmodium parasites. The World Health Organization estimates that in 2020, about 240 million people had malaria and about 627,000 of them died.

Scientists at the US National Institutes of Health, led the trial of the mAb, known as L9LS -- a laboratory-made version of a naturally occurring antibody called L9, derived from the blood of a volunteer who had received an investigational malaria vaccine.

The antibody prevents malaria by neutralising the parasites in the skin and blood before they can infect liver cells.

"These early clinical trial results demonstrating that a monoclonal antibody administered subcutaneously can protect people from malaria are highly encouraging," said Anthony Fauci, Director of National Institute of Allergy and Infectious Diseases (NIAID), part of NIH.

"A one-time intervention that protects against malaria for six months to a year could significantly reduce morbidity and mortality among children in malaria-endemic regions and offer an effective preventive tool for health care workers, military personnel and travellers to these areas," he added.

L9LS is similar to a candidate anti-malarial antibody known as CIS43LS that the NIH's Vaccine Research Center (VRC), developed and found to be highly protective in a small trial when administered by the intravenous route.

However, L9LS is two to three times more potent. Increasing the potency allowed for subcutaneous injection, a more cost-effective and feasible route of administration than intravenous infusion.

The trial, detailed in The New England Journal of Medicine, involved 18 volunteer participants receiving various doses of L9LS subcutaneously or intravenously.

After tolerating the injection and experiencing no safety concerns, the participants allowed mosquitoes carrying the malaria parasite to bite their forearm five times, starting from two to six weeks after receiving the mAb candidate, in a carefully controlled setting.

L9LS fully protected 15 of 17 (88 per cent) participants from malaria infection during the 21-day period.

All volunteers in the control group that did not receive L9LS, became infected and were promptly treated without complications. Encouragingly, four of the five participants who received a low, subcutaneous dose of the mAb were protected from malaria.

"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, chief of the Cellular Immunology Section in the VRC, who led the development of L9LS.

Additional clinical trials evaluating if L9LS can prevent malaria over six to 12 months against seasonal and perennial transmission are underway in infants and children in Mali and Kenya, where malaria is endemic.