Brean Capital has come out today with a pair of substantial downgrades. First, it has downgraded VIVUS (VVUS), maker of the obesity drug Qsymia, to a sell, and set the price target at a painful $7 per share. This is a 50% downside from yesterday's $14.32; the stock fell 5% as a result. Brean also downgraded Celsion (CLSN 2.00%) to a sell, placing the price target at an astonishing $1 per share. Celsion is also down over 5% on the news. In this video, Motley Fool health-care analyst David Williamson tells us what was behind these killer downgrades, and whether investors should be worried.