Researchers are working as quickly as science will allow to determine whether hydroxychloroquine, a decades-old malaria drug touted by President Donald Trump as a potential “game changer” in curtailing the Covid-19 pandemic, is effective in fighting the coronavirus. Federal health regulators have fast-tracked approvals for coronavirus research, allowing scientists across the nation to skip through months of red tape on potential treatments and vaccines for the deadly virus. On March 24, researchers at NYU Langone launched one of the nation’s largest hydroxychloroquine studies and enrolled their first patient 10 days later. It’s one of more than a dozen formal studies...