15. Rituxan

Product: Rituxan; MabThera
Generic name: rituximab
Companies: Roche; Pharmstandard
2015 sales: $7.39 billion
2022 sales: $2.89 billion
Current indications: non-Hodgkin lymphoma; chronic lymphocytic leukemia

Roche's third-biggest product, Rituxan, celebrates its 20th anniversary this year after debuting in 1997 in Switzerland and reaching the U.S. market the following year. The majority of sales for Rituxan are thought to come from oncology indications, although it is also approved for rheumatoid arthritis and organ rejection.

For now, Rituxan is still growing nicely, up 6% in the first half of 2016, thanks in part to a subcutaneous formulation of the antibody that reduces the treatment time and is more patient-friendly than the original intravenous infusion.

Since its launch in 2014, the new version has given some renewed momentum to the franchise, and according to one Roche exec, has around 35% penetration "with more to grow between now and the entrance of biosimilars."

Roche is expecting to face Rituxan biosimilars by the end of 2017 in Europe and in the U.S. after 2019. Several clones of the drug are already available in emerging markets, including India, Russia and several countries in Latin America. Celltrion is in pole position among the companies developing biosimilars of Rituxan, with the European Medicines Agency (EMA) filing its CT-P10 version of Roche's drug in late 2015. Another candidate from Novartis' generics unit Sandoz was filed in the EU in May, and Polish company Mabion S.A. has indicated it will submit its version before the end of the year. In December 2016, Sanofi struck a deal with Taiwan's JHL Biotech that could be worth up to $236 million to back future commercialization of JHL's in-development Rituxan copycat in China, among other products.

EvaluatePharma sees Rituxan as the most vulnerable among Roche's current stable of big-selling cancer drugs, losing $4.5 billion of its annual sales by 2022.

15. Rituxan