What: Exelixis (NASDAQ:EXEL) ended Friday up 10.5% after the company announced Thursday after the closing bell that the European Medicines Agency (EMA) had accepted its application to market cabozantinib as a treatment for kidney cancer.

Eight hours earlier -- before the bell, so investors had time to digest the news during yesterday's trading, when Exelixis fell 2.8% -- the company announced that the FDA had accepted the equivalent marketing application to sell the drug in the U.S.

So what: Exelixis had already announced that the applications had been submitted to regulators, so their acceptance shouldn't have come as a surprise.

Both U.S. and EU regulators gave cabozantinib a shortened review period -- called a priority review in the U.S. and an accelerated assessment in the EU -- which adds value to Exelixis because an earlier approval means cabozantinib will generate revenue for the company, assuming it's approved, of course. And let's face it -- an approval seems like all but a sure thing. Cabozantinib beat Novartis' (NYSE:NVS) Afinitor in a head-to-head trial. Novartis' drug is currently the standard of care for the patients Exelixis is applying to treat.

But the accelerated assessment in the EU was already announced, and investors should have expected a priority review in the U.S. because the FDA had already granted Breakthrough Therapy designation for cabozantinib.

Now what: While it's hard to see how the news justifies a 10% increase in the stock, keep in mind that, even with the move, Exelixis is still down 18% for the year. It's hard to see how any company news justifies the decline, as well.

Exelixis is currently trading at the whim of investor sentiment about biotechs, which seem to be gyrating daily. Getting cabozantinib approved and on the market will give investors something fundamental to value the company on. Even the larger biotechs have seen wild swings based on sentiment, so the rocky road may never go away completely.