Gaudinski MR, Berkowitz NM, Idris AH, et al. - This study’s findings demonstrate that administration of the long-acting monoclonal antibody CIS43LS prevented malaria after controlled infection among adults who had never had malaria infection or vaccination.

• CIS43LS at a dose of 5 mg per kilogram of body weight, 20 mg per kilogram, or 40 mg per kilogram was administered in 25 participants, and 4 of the 25 participants received a second dose (20 mg per kilogram regardless of initial dose).

• No safety concerns were distinguished. Dose-dependent increases were found in CIS43LS serum concentrations, with a half-life of 56 days.

• Compared with 5 of 6 control participants who did not receive CIS43LS, none of the 9 participants who received CIS43LS, had parasitemia according to polymerase-chain-reaction testing through 21 days after controlled human malaria infection.

• The results revealed that two participants who received 40 mg per kilogram of CIS43LS and had undergone controlled human malaria infection approximately 36 weeks later had no parasitemia, with serum concentrations of CIS43LS of 46 and 57 μg per milliliter at the time of controlled human malaria infection.