This is a repurposed drug that has safety data available from...

This is a repurposed drug that has safety data available from previous Phase 3 trials for other indications. There is no reason to have another phase 3 data tria for safety data. It would be almost impossible to design a treatment trial for a mosquito-transmitted virus like Dengue as its onset and diagnosis are so uncertain even in endemic areas. You cannot ethically just give people standard Dengue Fever for a trial. Surely a phase 3 trial would use the US Army's attenuated Dengue Virus strain again and repeat the Phase 2b study with a larger number of cases. The US Army would most likely fund and run the trial.