13. Enbrel

Amgen and Pfizer
Rheumatoid arthritis, psoriasis and other inflammatory conditions
2015 sales: $5.36 billion
2020 projection: $4.95 billion

Enbrel is among the few drugs expected to top the rankings in 2020 despite an impending decline in sales. The drug is on the verge of facing biosimilar competition in Europe, with Biogen ($BIIB) and Samsung Bioepis set to launch a competing version. Biosim rivals are farther away in the U.S.--just how far away is open to question--but Amgen ($AMGN) won new patents in 2011 that could protect the drug through 2029.

Europe is Pfizer's ($PFE) problem, because it holds marketing rights to the drug outside the U.S. Biogen and Samsung won European committee backing for their version, Benepali, in November 2015, with full approval expected within a few months.

The conventional wisdom on biosimilars is that the pricing discounts will be modest and market-share gains commensurately smaller than with run-of-the-mill generics. But as Remicade's experience in the European market shows, some biosimilar makers are acting more aggressively, with discounts topping 50% or even 60% in some countries. Whether Biogen and Samsung are eager to do the same remains to be seen.

Meanwhile, Pfizer's international Enbrel sales face other problems, albeit smaller: Merck ($MRK) and Samsung Bioepis have biosim approval in South Korea, while Cipla sells a version in India.

It's Amgen that will face U.S. competition, but perhaps not for many years yet. The Thousand Oaks, CA-based biotech figures its new patents will hold off biosimilar Enbrel till 2029. But Novartis' ($NVS) Sandoz unit has already filed for FDA approval for its version, and it's ready to challenge Enbrel's new patent protection.

"Sandoz believes that it has a good faith legal basis to challenge the validity of these patents," Sandoz said in a statement after the FDA accepted its approval app.

For Amgen, an Enbrel copy in the U.S. would put $5.1 billion in 2015 revenue at risk, and the California biotech has been preparing. In 2014, it announced far-reaching job cuts affecting 2,900 positions--or 15% of its workforce. Since then, Novartis has already begun threatening Enbrel's slice of the pie with next-gen psoriasis-fighter Cosentyx, which hit the market earlier this year. -- Tracy Staton (email | Twitter)

For more:
Novartis targets Amgen's Enbrel with second biosimilar app
Biogen and Samsung's Enbrel biosimilar wins EMA nod for EU approval
Big question for Pfizer: Will Enbrel's EU biosim bring on the pain?

13. Enbrel