 As modipafant is untested in uncomplicated dengue fever patients, a double-blinded sentinel group consisting of 4 participants randomised in a 1:1:1:1 ratio of Cohort 1: Cohort 2: Cohort 3: Cohort 4 will complete treatment to Study Day 5 prior to continuing enrolment of the remaining participants. Remaining 68 participants will be enrolled in parallel in a double-blinded fashion. 