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 Tetraphase Pharmaceuticals Inc (NASDAQ:TTPH) popped as high as 14% today after the Food & Drug Administration granted Fast Track designations for both the intravenous and oral formulations of its lead antibiotic candidate, eravacycline.

So what: The news suggests that the FDA considers complicated intra-abdominal infections as a serious unmet medical need and, in turn, raises the probability that eravacycline will be approved much sooner than expected. The most recently approved next-generation tetracycline tigecycline, Pfizer's (NYSE:PFE) Tygacil, is already generating more than $400 million in sales, so Wall Street is naturally excited over Tetraphase's market opportunity.

Now what: Tetraphase will continue working with the FDA to advance eravacycline through Phase 3 development, with its NDA filing expected for the end of 2015. "There is a serious and growing public health threat as a result of the rise in increasingly difficult-to-treat bacterial infections, particularly those caused by multidrug-resistant Gram-negative bacteria," said President and CEO Guy Macdonald. "With eravacycline and our pipeline of novel antibiotic candidates, we are attempting to directly address this threat." So while Tetraphase might still be too speculative for average investors, today's positive news, coupled with the fact that the shares remain well off their 52-week high, may make the stock an interesting pick for biotech-savvy Fools.

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