Image source: stevepb via Pixabay.

What: Shares of Medivation (MDVN) were up more than 10% as of 3:00 p.m. ET after the cancer-focused biopharmaceutical company reported its fourth-quarter earnings.

So what: Sales of its cancer medication Xtandi continue to grow strongly. Medivation's collaboration partner Astellas Pharma (ALPMY -0.42%) reported $315.9 million in U.S. sales of Xtandi, up 37% versus the same time last year. Growth outside the U.S. was even stronger and came in at $231 million, up 83%.

Remember that Medivation records Xtandi revenue in three different ways: U.S. collaboration revenue, ex-U.S. collaboration revenue, and up-front and milestone payments.

Here's how those results came in for the quarter:

 Q4 2015Q4 2014Change %
U.S. Collaboration: $157.9 million  $115.1 million 37%
Ex-U.S. Collaboration $44.8 million $18.2 million 146%
Milestone Payments $175 million $141 million 24%

In total, GAAP collaboration revenue for the period came in at $377 million, up 35% from the year-ago period and was ahead of the $371.9 million that analysts were expecting. However, moving forward, it said that it will not be earning more milestone payments from Astellas -- the $175 million it recorded during the period would be its last.

Stripping out the milestone payments revenue came in at $202.7 million, up strongly from the $133.4 million that it reported in the year-ago period. That allowed Medivation to report non-GAAP net income of $49.5 million or $0.29 per diluted share, which was $0.05 higher than analysts were expecting.

The company also confirmed that its supplemental new drug application to expand the labelling of Xtandi has been accepted by the Food and Drug Administration. The agency gave the companies a PDUFA date of Oct. 22, 2016.

The beat on revenue and earnings per share appear to be the reasons that shares are soaring today.

Now what: To keep sales of Xtandi going strong in 2016 the company announced that it increased its specialty sales force more than 40% during the quarter. The company believes that will allow it to more effectively target the roughly 80% of prostate cancer drug prescribing urologists that have yet to write a prescription for Xtandi.

In total, Medivation offered up the following guidance for 2016:

For reference, the company reported non-GAAP collaboration revenue of $695 million in 2015 and non-GAAP earnings per share of $1.01, so the midpoint of its ranges represents growth of roughly 35%. That's roughly in line with what the market was expecting, as analysts were projecting revenue of $910 million and $1.35 in earnings.

Given the solid quarterly numbers and the upbeat forecast, it's hard to blame the market for feeling bullish about Medivation's stock today.