The Federal Trade Commission has sent three warning letters to companies marketing Thymosin Alpha-1 as a treatment for COVID-19. The agency says such claims are “unlawful,” because they are not backed by reliable scientific evidence.

FILE – This Jan. 28, 2015, file photo, shows the Federal Trade Commission building in Washington. Federal regulators are amping up their investigation of the market dominance of five giant tech companies, demanding detailed information on their acquisitions back to 2010. The Federal Trade Commission announced the move Tuesday, issuing orders to Facebook, Amazon, Apple, Microsoft and Google’s parent Alphabet Inc. (AP Photo/Alex Brandon, File)