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) plunged as much as 23% Tuesday after overstating the clinical-trial response to its combination Kalydeco/VX-809 cystic fibrosis treatment.

So what: Vertex shares soared earlier this month after data suggested that the two-drug therapy was on the straight path to becoming a blockbuster, but management's mistake -- 35% of patients, not the previously stated 46%, showed improved lung function -- is naturally forcing investors to sober up a bit. While the revised data is still higher than Wall Street had initially expected, the "misinterpretation" of the initial results calls management's credibility into question.  

Now what: I'd look into this plunge as a possible buy-in opportunity. Despite the less robust data, management hasn't changed its conclusions regarding Kalydeco/VX-809 and still plans to move forward with a late-stage clinical trial. Although today's news will certainly weigh on investor sentiment in the short run, the drug's long-term multibillion-dollar potential remains largely intact.

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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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