In the following video, Motley Fool health-care analyst David Williamson continues his look at the top-performing health-care stocks of this past January, by highlighting the biggest winner of the month, Keryx (KERX). The stock exploded this month, shooting up 247%, although David reminds us that this was possible only because of the stock's starting point after the share price collapsed last year, when a cancer drug it shared with Aeterna Zentaris (AEZS -4.99%) failed its phase 3 trial. David tells us about the new drug in Keryx's pipeline that is crushing its trial endpoints, and how the new drug compares with its competition.