PfSPZ Challenge in Healthy Malaria-Naïve Adults in the United States

This phase I trial of the replication-intact PfSPZ Challenge vaccine given under CQ (PfSPZ-CVac) cover will randomize 28 healthy adult participants to one of three cohorts. Group 1 (n=12) will be randomized to receive PfSPZ Challenge vaccine at a dose of 51,200 sporozoites or 0.5 mL of sterile normal saline placebo by DVI on Days 3, 10 and 17. Group 2 (n=4) will be randomized to receive PfSPZ Challenge vaccine at a dose of 102,400 sporozoites or 0.5 mL of sterile normal saline placebo by DVI on Days 3, 10, and 17. Within both groups, placebo will be assigned 1:3, with blinded allocation to the two treatments within each group. All subjects in Study Groups 1 and 2 will receive, by directly observed treatment (DOT), oral chloroquine (CQ) on Days 1, 8, 15, and 22 at a suppressive dose of 600 mg base on Day 1 and 300 mg base on Days 8, 15 and 22. All subjects in Group 3 (n=9) will receive PfSPZ Challenge vaccine at a dose of 102,400 sporozoites per administration, with vaccine given on a Day 1, 6, and 11 schedule. Subjects in Group 3 will also receive, by DOT, oral CQ, with a suppressive dose of 600 mg base on Day 1 and a dose of 300 mg base on Days 6, 11, and 16. At 10 weeks after the third administration of study vaccine or placebo, all subjects within the three groups will receive the PfSPZ Challenge by direct venous injection at a dose of 3,200 P. falciparum sporozoites to assess vaccine efficacy against controlled human malarial infection (CHMI). The primary objective of this study is to 1) evaluate the safety and tolerability of escalating doses of Sanaria PfSPZ Challenge administered by DVI on varying schedules to healthy malaria-naïve adults taking suppressive doses of CQ (PfSPZ-CVac).