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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