A Phase-I trial of a monoclonal antibody for malaria, sponsored by the National Institutes of Health (NIH), has shown that one dose prevented malaria for up to nine months in those exposed to the malaria parasite Plasmodium falciparum. The open-label, dose-escalating two-part study is the first to demonstrate that a monoclonal antibody, CIS43LS, can prevent malaria in people, and a larger, Phase II study is now under way. CIS43LS was discovered and has been developed at NIH. For details see reporting by GEN.