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 biotech Inhibitex (Nasdaq: INHX) were skyrocketing on Monday, gaining an eye-popping 144% after Bristol-Myers Squibb (NYSE: BMY) announced over the weekend that it's buying the drug developer for $2.5 billion.

So what: For Inhibitex shareholders, the benefit of the deal is very apparent. The $26-per-share offer from Bristol-Myers represents a premium of more than 160% over Friday's closing price. Sure, some shareholders may have expected even better gains over time, but the buyout provides a significant profit today and eliminates the risk that the company's leading treatments don't end up getting approved.

For Bristol-Myers shareholders, it's a bit more complicated. The company picks up a promising developer with a particularly notable hepatitis-C treatment that's currently in phase 2. However, it also assumes the approval risk and the funding requirements to get that drug (INX-189) and others to the finish line. In the company's press release it said that deal would likely be dilutive through 2016.

Now what: Often the gap between a target company's previous stock price and the takeover price closes pretty quickly. In this case, today's 140%-plus surge gets Inhibitex's stock pretty close to Bristol-Myer's offer price, but investors could still pick up nearly 10% more by sticking around until the full $26 is realized. The risk that they run is the plunge that would take place if the deal fell apart -- an eventuality that's less likely when the buyer is as large and well-capitalized as Bristol-Myers.

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