Two months after the Trump administration awarded $21 million to study whether a common heartburn drug was effective against COVID-19, government health officials raised serious concerns about patient safety and scientific integrity, according to internal documents obtained by The Associated Press.

The U.S. Department of Health and Human Services outlined a long list of concerns in a June 8 letter, concluding there was "a high probability" that the companies doing the research would fail to honor the terms of the deal to assess famotidine, the active ingredient in Pepcid, as a coronavirus trea...