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 hepatitis C drug developer Inhibitex (Nasdaq: INHX) felt ill today, with shares down as much as 17%, over continued safety concerns with its drug INX-189.

So what: Last month, rival Pharmasset (Nasdaq: VRUS) reported some safety issues with its own similar drug, crushing others in the sector and setting the stage for investor skittishness. This morning's sell-off may be attributed to cautious comments from Bank of America Merrill Lynch analyst Rachel McMinn.

Now what: McMinn said that there could be a lot of downside if safety issues arise, although she believes the risk-reward balance is still positive. Inhibitex is conducting a study to evaluate different dosages, and the interim results of the study are expected within this month or next. Shareholders are anxious that INX-189 may share too many similarities with Pharmasset's PSI-938.

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