Developing an effective vaccine against malaria continues to be a challenge, but US researchers think they have a monoclonal antibody candidate that could provide passive immunity against the parasite.
Scientists at the National Institutes of Health Clinical Center in Bethesda, Maryland, have started a phase 1 study to see if the antibody – called CIS43LS – can prevent malaria infection in healthy human volunteers.
The trial will enrol around 73 adults aged 18 to 50, who have never had malaria in the past. After treatment with one of three doses of the antibody (5, 20 and 40 mg/kg), the volunteers will be exposed to mosquitoes carrying the Plasmodium falciparum malaria parasite under controlled conditions, to see if the drug can prevent infection. Results should be available sometime in the first quarter of next year.
If it proves to be effective, the hope is that the antibody could be used to protect “tourists, medical workers or military personnel who travel to areas where malaria is common,” commented Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases (NIAID) in the US.
A recombinant malaria vaccine called Mosquirix (RTS,S/AS01) – developed by GlaxoSmithKline – was given a positive ‘scientific opinion’ by the EMA in 2015 after three decades of research, but is acknowledged to have limited efficacy.
It is nevertheless being used in a World Health organisation (WHO) pilot programme in areas of moderate-to-high malaria transmission in sub-Saharan Africa, focusing on young children in Ghana, Malawi and Kenya, on the basis that even modest efficacy could have a beneficial impact at population scale.
The pilot started dosing children in the three countries last year, with GSK donating ten million doses for the project, and is expected to continue until 2023.
In a phase 3 trial, four doses of Mosquirix given to children aged between five and 17 months had a preventive efficacy of 39%, but also seemed to protect them from developing severe malaria.
“In the absence of a highly effective, long-lasting vaccine, preventing malaria infections for several months with a single dose of monoclonal antibody also could be valuable in specific parts of Africa where malaria cases increase greatly during annual rainy seasons,” said Fauci.
The vaccine was developed by NIAID researchers led by Robert Seder several years ago, based on an antibody taken from the blood of a volunteer who had received an investigational vaccine made from whole, weakened malaria parasites.
There were 228 million cases of malaria worldwide in 2018, according to the WHO, causing 405,000 deaths.