Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of drug developer Exelixis (Nasdaq: EXEL) were soaring in early trading today, tacking on as much as 11% before settling back down to a low-single-digit gain.

So what: Investors got fired up after Bloomberg reported that Exelixis is working with Goldman Sachs to field potential buyout offers after its prostate cancer drug showed promise in a study late last year. As it is, the company's stock has more than doubled since the positive data on XL184 was published Nov. 17, but investors could see further gains if a buyer with deep pockets steps in to snap up the company. After a partnership with Bristol-Myers Squibb (NYSE: BMY) ended last June, Exelixis has sole rights to the treatment.

Now what: Both the company and Goldman are staying mum on the situation. I tend to be very skeptical when it comes to speculating on potential buyouts. Certainly there's a very plausible story here -- Exelixis has a promising treatment and the big pharma players need new drugs and have truckloads of cash to spend. However, investors may want to stay focused on the longer-term prospects for Exelixis on its own rather than gambling on the potential for a quick bump from a takeover.

Want to keep up to date on these stocks?

Exelixis is a Motley Fool Rule Breakers pick. The Fool owns shares of Exelixis. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors.

Fool contributor Matt Koppenheffer does not have a financial interest in any of the companies mentioned. You can check out what Matt is keeping an eye on by visiting his CAPS portfolio, or you can follow Matt on Twitter @KoppTheFool or on his RSS feed. The Fool's disclosure policy prefers dividends over a sharp stick in the eye.