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A monoclonal antibody appeared to show some efficacy in a small group of patients with malaria who had never been exposed to the disease, according to a first-in-human phase I trial.

None of the nine participants exposed to controlled human malaria infection in the treatment group developed parasitemia through day 21 compared with five of six controls 8 to 9 days after infection, reported Robert Seder, MD, of the Vaccine Research Center at the National Institute of Allergy and Infectious Diseases (NIAID) in Bethesda, Maryland, and colleagues in the VRC-612 group.

Moreover, two participants exposed to controlled human malaria infection had no parasitemia about 36 weeks later, they wrote in the .

Not only that, but the treatment was safe, with no infusion-related reactions or treatment-related serious adverse events, the authors noted.

"The results reported today suggest that a single infusion of a monoclonal antibody can protect people from malaria for at least 9 months," said NIAID Director Anthony Fauci, MD, in a statement. "Additional research is needed, however, to confirm and extend this finding."

Seder's group noted that the treatment, CIS43LS, was developed from the blood of a volunteer who received an investigational malaria vaccine. They discovered the CIS43 antibody could bind to a site on the parasite surface protein that helps facilitate malaria infection; preclinical trials showed positive results, as well.

The group conducted a of healthy adults ages 18-50 who had not been exposed to malaria infection or vaccination.

Part A was a dose-ranging study of 21 participants from Jan. 7 to March 5, 2020. Four received an intravenous dose of monoclonal antibody of 5 mg/kg of body weight, four received a subcutaneous dose of 5 mg/kg, five received an intravenous dose of 20 mg/kg, and eight received an intravenous dose of 40 mg/kg. Four of these participants also received a second dose of 20 mg/kg.

Part B enrolled 18 participants from Sept. 8 to Oct. 16, 2020. Seven participants from Part A were re-enrolled, and 11 were newly enrolled. Ten participants received the treatment in Part A, Part B, or both, and eight served as controls. Among 11 newly enrolled participants, four received 40 mg of treatment intravenously and seven served as controls. In addition, four of seven re-enrolled participants from Part A received a second dose of treatment at 20 mg/kg intravenously.

Adverse events were mild to moderate, and only occurred among patients receiving 5 mg/kg intravenously. They included single events of dizziness, transient asymptomatic neutropenia, and elevation in creatinine level, all of which resolved.

The authors noted dose-dependent increases in serum concentrations, and a half-life of 56 days.

Limitations to the data included its small sample size, and that only data on intravenous administration, not subcutaneous administration, were evaluated.

"Monoclonal antibodies may represent a new approach for preventing malaria in travelers, military personnel, and healthcare workers traveling to malaria-endemic regions," said Seder in a statement. "Further research will determine whether monoclonal antibodies can also be used for the seasonal control of malaria in Africa and ultimately for malaria-elimination campaign."

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