ImClone Systems Incorporated Under Siege

How often do you see a pharmaceutical company's drug receive marketing approval and then watch a rival's shares end up in positive territory for the day as well? Not very often, but shares of ImClone Systems (Nasdaq: IMCL - News) did just that yesterday. This happened despite news of FDA regulatory approval for Amgen's (Nasdaq: AMGN - News) colon cancer drug, Vectibix, which will compete directly with ImClone's only marketed drug, Erbitux.