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 Vertex Pharmaceuticals (Nasdaq: VRTX) sank as much as 13% today after reporting initial data on a combination cystic fibrosis treatment.

So what: Although the midstage study showed a potential benefit from combining VX-770 and VX-809, the results -- patients' sweat chloride levels were reduced by 9.1 millimoles per liter -- just weren't as impressive as Wall Street had hoped. Given the relatively small treatment effect, investors are obviously questioning whether the combo drug is indeed potent enough to improve lung function.

Now what: Today's plunge might be an opportunity for less risk-averse Fools. Investor expectations aside, Vertex's phase 2 data were nonetheless statistically significant, with some patients displaying very marked improvement. I wouldn't be so quick to count out its blockbuster potential just yet, and with the stock now down roughly 20% over the past month, it might even be a good time to bet on it.

Interested in more info on Vertex? Add it to your watchlist.

Fool contributor Brian Pacampara owns no position in any of the companies mentioned. Motley Fool newsletter services have recommended buying shares of Vertex. Try any of our Foolish newsletter services free for 30 days.

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