Biogen Idec's (NASDAQ:BIIB) earnings announcement was delayed because of the snow storm in Boston, but it was well worth the wait. Fourth-quarter revenue was up 34% year over year, with adjusted earnings per share 74% higher than the year-ago quarter. It's hard to complain about growth like that.

Going into the release, there was worry that growth of Tecfidera, Biogen's oral multiple sclerosis drug, was slowing down, especially in the U.S., but that doesn't really seem to be as big of a problem as investors feared.


Q1 2014

Q2 2014

Q3 2014

Q4 2014

Tecfidera Sales (in millions)





Quarter-Over-Quarter Growth





Source: Company press releases.

There was one extra shipping week in the fourth quarter that helped U.S. sales; but even factoring that in, Biogen shipped $65.4 million worth of Tecfidera to U.S. customers each week in the fourth quarter compared to $60.5 million per week in the third quarter.

As you'd expect, switching from other therapies to Tecfidera has slowed down as Biogen runs out of patients looking for other treatment options -- first in the U.S., and then in Europe where it launched later -- which explains the slower growth in the latter half of the year. More importantly, Biogen hasn't seen a huge discontinuation rate of people already on therapy after a case of progressive multifocal leukoencephalopathy was revealed last quarter.

While Tecfidera has blown past Tysabri and Avonex to become Biogen Idec's most important drug, the latter two are nonetheless important given that they're still multi-billion dollar products. Avonex and its follow-on drug, Plegridy, combined for $3.1 billion in sales in 2014, up slightly from the $3 billion worth of Avonex sales in the prior year. Tysabri sales came in at $2 billion for the year, up about 18% from the prior year.

Considering the three drugs all treat the same disease, the lack of cannibalization is rather amazing. Combined, the three drugs grew 49% year over year in 2014. I don't know how many new patients were diagnosed with multiple sclerosis in 2014, but I can guarantee the number of patients didn't increase by 49%.

Biogen has some other drugs, as well, but they're a bit washed out by the big three that make up $8 billion of the company's $9.7 billion in 2014 sales. It made for a nice year, but Biogen isn't going to be able to keep the growth rate as high as it was in 2014. This year's revenue guidance is for year-over-year growth of 14% to 16%.

To get to hyper-growth again -- not that 14% growth is anything to complain about -- the company will need another megablockbuster. The most likely candidate for the job is BIIB037, an Alzheimer's disease drug that Biogen is fast tracking straight from phase 1b to phase 3 because the interim data was so good. I wouldn't pencil in revenue from BIIB037 just yet -- a lot more Alzheimer's disease drugs have failed than have succeeded -- but if the phase 3 program is successful, it's not hard to see BIIB037 being as large as the big three combined.