Xeloda - $647.6 million


Company: Genentech
2011 sales: $647.6 million
Developer: Roche
FDA approvals: Metastatic colorectal cancer, 1998; metastatic breast cancer, 2002; adjuvant colon cancer therapy, 2005

Xeloda, the first FDA-approved oral chemotherapy, is one of the older drugs on our list, with more than a dozen years on the U.S. market. And it shows little sign of slowing down--yet. Sales grew 19% in 2011 on top of 13% growth in 2010, as it gained market share in breast cancer and benefited from shortages of rival drugs.

It also benefits from its role in some FDA-approved combination therapies--with GlaxoSmithKline's ($GSK) Tykerb for breast cancer, for instance, or with Genentech's own Herceptin for stomach cancer. The Tykerb-Xeloda combo may soon be shot down by the company's experimental breast cancer drug, T-DM1; a study pitting the two treatments against each other is set for release next month.

Despite its age, Xeloda also has no generic competition in the U.S.--yet. Roche settled a patent fight with copycat drugmaker Mylan ($MYL) last June after two years, granting the generics company a license, but the terms were undisclosed. So, it's unclear when Mylan will be ready to launch its copy; Roche had contended that Xeloda's patent protection won't expire till 2013.

Xeloda - $647.6 million