Sanaria PfSPZ Challenge With Pyrimethamine or Chloroquine Chemoprophylaxis Vaccination (PfSPZ-CVac Approach): A Randomized Double Blind Placebo Controlled Phase I/II Trial to Determine Safety and Protective Efficacy Against Natural Plasmodium Falcipa...

Chloroquine phosphate is approved for suppressive treatment (prophylaxis) and for acute attacks of malaria due to P. vivax, P. malariae, P. ovale, and susceptible strains of Pf. Chloroquine is a blood-stage schizonticide, highly active against replicating forms of blood-stage drug- sensitive parasites. As such, it is routinely employed as first-line prophylaxis against development of patent parasitemia and clinical malaria in non-immune travelers to areas with chloroquine sensitive Pf. In the pilot, chloroquine administration will begin with a loading dose 2 days prior to PfSPZ Challenge and finishing with a maintenance dose 5 days after PfSPZ Challenge. In the main phase, chloroquine will be first administered as a loading dose 2 days prior to PfSPZ Challenge and continuing weekly using a maintenance dose for a total of 10 doses, finishing with a last dose 5 days after the third injection with PfSPZ Challenge.

PfSPZ Challenge (NF54) acts as the immunogen in the PfSPZ-CVac approach to vaccinating against malaria. Participants will receive either one (in the pilot phase) or 3 (in the main phase) 400,000 or 300,000 aseptic, purified, cryopreserved, fully infectious PfSPZ injections by DVI (with concurrent administration of antimalarial drugs). Following immunization, participants in the main phase will be followed through the transmission season in order to assess vaccine efficacy.

"Pyrimethamine has been FDA approved for acute treatment and chemoprophylaxis of malaria due to susceptible strains of plasmodia.~Pyrimethamine has been shown to possess both liver and blood stage activity. In this study, we plan to use a higher dose of pyrimethamine, 75 mg orally for either one or two days each month. The pilot arms will receive either a total of 1 daily dose or 2 daily doses. The main arms will receive a total of 3 daily doses or a total of 6 doses."

Antimalarial (Coartem ) will be administered to all participants twice during the study, approximately 2 weeks prior to the first vaccination in order to clear pre-existing parasitemia that may interfere with immunity development. The second dose will be given approximately 2 weeks prior to the 3rd vaccination in order to clear any parasitemia infection that may have happened naturally during the vaccination period and prior to the follow up period.

Ibuprofen likewise is not a part of the investigational product/regimen, but will be provided to participants in the chloroquine arm (Arm 4) if required to mitigate typical symptoms of malaria infection such as headache, myalgia, fever and chills.