There was some early evidence it could be effective. I’m actually supportive of the FDA’s move to do both the emergency approval and the retraction. Without the ability to take calculated risks in a situation where either approving or unapproving can cause harm, the agency could be a hindrance more than a help. And that means some emergency measures will prove wrong. If none prove wrong, the agency is being too cautious and allowing people to die because of it.

EDIT: I hate the politicization of HCQ by Trump, of course.