What: After confirming second quarter financial results issued by its marketing partner Astellas (ALPMY 0.10%)Medivation's (MDVN) shares soared 10% higher earlier today.

So what: Medivation reports that net U.S. sales of its prostate cancer drug Xtandi totaled $298.4 million last quarter, up 33% from the first quarter. Roughly half of that growth in the quarter stems from script volume, while the other half came courtesy of price hikes.

Medivation also reports that sales of Xtandi outside the U.S. continue to gain ground too. International sales of Xtandi, on which Medivation is paid a royalty, totaled $188 million in the second quarter, up 42% from the first quarter.

Additionally, Medivation also announced that its board of directors has approved a 2 for 1 stock split for investors on record as of August 13.

Now what: Xtandi is the company's only approved medicine and it's also the only drug the company is currently studying in clinical trials, so Medivation is a bit of a one-trick pony.

Medivation's ongoing trials could expand Xtandi's label to include use as a first line option in prostate cancer and as a breast cancer therapy, but only time will tell if those studies pan out and if so, how big a financial impact those indications would make on Medivation's future sales.

Investors should also know that a new rating system by the American Society of Clinical Oncology, or ASCO, appears to favor Johnson & Johnson's competing drug Zytiga, and that could lead to some shifts in market share this year. ASCO awarded a score of 42 to a combination of Zytiga and prednisone versus placebo and a score of 32 to Xtandi versus placebo. Admittedly, these two scores are being compared to placebo, rather than each other, so it's unclear whether doctors' prescribing trends will change, but it still warrants watching.

Investors should gain more insight into Xtandi's impact on Medivation and management's plans for the rest of the year when the company officially reports its second quarter financials on August 6.