A clinical trial for a coronavirus antibody treatment made by the drug company Eli Lilly has been halted due to a “potential safety concern,” according to emails obtained by The New York Times. The trial, sponsored by the government, was testing the drug on hundreds of hospitalized COVID-19 patients. In emails sent Tuesday, government officials told researchers at testing sites that they should stop adding volunteers out of an “abundance of caution.” A company spokeswoman confirmed the pause but wouldn’t say what the safety issue was.

Yesterday, Johnson & Johnson paused its coronavirus vaccine trial because of an illness in a patient, and AstraZeneca halted its vaccine trial last month after two participants had adverse side effects. President Trump took a similar product to Eli Lilly’s to treat his coronavirus, later erroneously calling it a “cure” and saying he wanted it to be made available, for free, to every coronavirus patient. Eli Lilly had applied for emergency use authorization shortly after.