An antiviral originally designed to tackle Ebola. An anti-malarial treatment dating back to World War II. A drug combo already used against HIV. A molecule involved in regulating inflammation in the body tested on marmosets. You might ask what all of these drugs have in common? Well, according to the World Health Organisation, these compounds have the highest likelihood of working against Covid-19. Thus, they are all on focus on WHO's megatrial, called SOLIDARITY.