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 Cubist Pharmaceuticals (UNKNOWN:CBST.DL), a biopharmaceutical company devoted to developing acute care therapies, added 12% following the announcement of its second-quarter earnings results.

So what: For the quarter, Cubist reported 12.2% revenue growth over the year-ago period, to $258.8 million, as its lead product Cubicin saw revenue jump 13.5%, to $227.1 million. Profit for the quarter decreased to $0.42 per share, from $0.56 per share last year. Still, this was certainly more than enough to excite investors, because Wall Street had been expecting just $254 million in sales and a profit of $0.40 per share. Also fueling today's gains was an update on the advancement of ceftolozane/tazobactam (previously CXA-201) in late-stage trials.

Now what: This was another solid quarter for Cubist. As always, I'm a bit leery when a biotech stock gets a massive chunk of revenue from just a single drug -- in this case, Cubicin is responsible for nearly 88% of total revenue -- as it leaves the company exposed should a sales or safety problem arise with that drug. However, I'm also seeing the beginnings of a diverse pipeline. Ceftolozane/tazobactam, should it be approved for all three tested indications, including the treatment of ventilator-associated bacterial pneumonia, could have peak sales potential of anywhere from $1 billion to $1.3 billion according to varying estimates. If I were you, I'd be adding Cubist Pharmaceuticals to your Watchlist.