Gilead Sciences (NASDAQ: GILD) experienced a decline of over 2% in its stock on Tuesday, contrasting with the S&P 500’s 0.6% gain, following negative news regarding one of its investigational programs. The U.S. Food and Drug Administration (FDA) issued a halt to Gilead’s testing of a two-drug combination intended to treat HIV, which is linked to AIDS. This regulatory setback has raised concerns among investors, contributing to the drop in Gilead’s stock price.