A Single Centre, Randomised, Double-blind, Placebo-controlled, Phase Ib Study to Evaluate the Safety, Tolerability and Chemoprotective Antimalarial Activity of P218 Against Controlled Human Malaria Infection With Plasmodium Falciparum Sporozoite Challenge in Non-immune Healthy Adult Volunteers

This was a single centre, randomised, double-blind, placebo-controlled Phase Ib study, to evaluate the safety, tolerability and chemoprotective activity of P218 in a controlled P. falciparum sporozoite infection model.

32 healthy men and women, aged 18 to 45 years were to be enrolled in 3 cohorts of respectively 8, 12 and 12 subjects. A subject could be enrolled in one cohort only and was to be randomised in a 3:1 ratio, to receive two consecutive administrations, 48 hours apart, of either P218 or placebo. Enrolment in cohorts proceeded sequentially, to facilitate review of data by a Safety Review Team (SRT) before populating a subsequent cohort.

Cohort 1 consisted of 2 subgroups of subjects, to be enrolled sequentially: subgroup 1 was to be composed of 2 subjects: one to receive two 1000 mg doses of P218 and one to receive placebo twice. Subgroup 2 was to be composed of 6 subjects: five to receive two 1000 mg doses of P218 and one to receive placebo twice. Subjects in subgroup 2 would not be treated until 24 hours after second IMP administration in the last subject of subgroup 1 and only after review of the safety data from subgroup 1 by the PI. Duration of each subject treatment and follow-up in Cohort 1 was 9 days. Progression to Cohort 2 was subject to review of the safety and tolerability data by a SRT.

Cohort 2 consisted of three subgroups of subjects, to be enrolled sequentially. Subgroup 1 was to be composed of 2 subjects: one to receive two 1000 mg doses of P218 and one to receive placebo twice. Subgroups 2 and 3 were to be composed of 5 subjects each: four to receive two 1000 mg doses of P218 and one to receive placebo twice. Subjects in subgroup 2 would not be treated until 24 hours after second IMP administration in the last subject of subgroup 1. On Day 1, each subject in Cohort 2 would be administered 3200 P. falciparum sporozoites (PfSPZ Challenge) by direct venous inoculation (DVI). First administration of 1000 mg of P218 or placebo will take place 2 hours after PfSPZ Challenge DVI; second administration of 1000 mg of P218 or placebo would take place 48 hours later. As of Day 7, parasitemia in every subject was to be assessed daily until the installation of malarial infection or until Day 28. Overall duration of each subject observation in Cohort 2 was 35 days. Progression to Cohort 3 was subject to assessment of safety and parasitemia data, as well as malaria signs and symptoms by a SRT.

Cohort 3 was to consist of two subgroups each with 6 subjects, to be enrolled sequentially. Treatment was to be allocated in a ratio of 3 active: 1 placebo. In each subgroup, at least 1 subject was to receive placebo and the remaining subjects would receive two 100 mg doses of P218 48 hours apart. Subjects in subgroup 2 would not be inoculated until 24 hours after second IMP administration in the last subject of subgroup 1. On Day 1, subjects were to be administered 3200 P. falciparum sporozoites by DVI. As of Day 7, parasitemia in every subject was to be assessed daily until the installation of malarial infection or until Day 28. Overall duration of each subject observation in Cohort 3 is 35 days.