Projected 2018 sales:
$2.584 billion
2012 sales: $998 million

Novartis ($NVS) has a good thing going with blood cancer drug Gleevec, and it's trying to keep it going. Gleevec is a revolutionary blockbuster that has obtained a variety of new uses since 2001, but its patent expires in 2015. And with competitors like Bristol-Myers Squibb's ($BMY) Sprycel and Pfizer's ($PFE) Bosulif floating around, Novartis is looking for ways to keep patients using drugs within its franchise. Enter Tasigna.

Novartis is hoping to retain its market for Gleevec by switching patients over to Tasigna, marketed as a drug for the same patient pool that does a more effective job. While Gleevec and Tasigna cost a couple of thousand dollars per month, a generic of Gleevec could cost as little as $40 or $50, so for Novartis, the switchover is the key to keeping customers and saving huge sales dollars. The company has gone as far as to conduct discontinuation trials in hopes of proving Tasigna's greater healing power.

For now, the strategy seems to be working. In its April 2013 earnings release, Novartis reported that Tasigna had continued to increase its share of the company's chronic myeloid leukemia franchise to 26% from 21% last year, citing a molecular response superior to Gleevec's.

For more:
Novartis has a win some, lose some day with Gleevec
Novartis wants Tasigna to cannibalize Gleevec to save its sales