Bolsonaro’s Chloroquine Believers Hamstring Drugmakers in Brazil

French biotech company Abivax SA is just weeks away from starting tests in Brazil of a treatment it says could prevent the most serious Covid-19 symptoms.

But in a nation whose president is a die-hard fan of chloroquine, Abivax and rival drugmakers not only have to prove their alternatives actually work, but also change public opinion. Neither are easy feats.

Brazil’s President Jair Bolsonaro has turned quasi-spokesman for the controversial malaria drug since the pandemic first started racing around the globe. He’s carried boxes to public rallies and shown it off on social media. He even popped a pill during ...