Sun Pharmaceutical, which has had its U.S. sales gut-kicked as its deal with FDA concerns at some of its manufacturing plants, has launched in the U.S. its copy of Novartis' ($NVS) blockbuster blood cancer drug Gleevec. With its first-to-file approval, the Sun generic will have the market to itself for 6 months. Gleevec is Novartis' top seller, generating $4.65 billion in 2015 revenue. The Swiss drugmaker expects to take a big hit from Sun's generic and subsequent copies. The situation is not as fortunate for Novartis as it was when its previous top selling med, heart pill Diovan, went off patent in 2012. Ranbaxy Laboratories, which Sun acquired last year, had the 180-day exclusive for Diovan but had to hold it off the market for nearly two years because of FDA regulatory concerns about the plant where it was to be produced. The delay was a big boost to Novartis' bottom line but prevented consumers from benefits from hundreds of millions of dollars in savings from the generic. Story | More | More