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 Regeneron Pharmaceuticals (Nasdaq: REGN) are down 10% today as analysts pop the bubble brewing in the stock's valuation.

So what: Shares have been on a tear since early August, but analysts at Leerink Swann think they've run too far, downgrading the stock based on valuation and the uncertainty of the Eylea launch. The age-related macular degeneration treatment is expecting an approval decision in November from the FDA.

Now what: As companies await FDA approvals, their stocks can go through wild price swings, and even analysts don't have an idea where shares should trade. Leerink Swann analyst Joshua Schimmer said, "It's not clear to us what the 'right' price point for Eylea may be." That's the kind of uncertainty I'm going to avoid in this market.

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

Fool contributor Travis Hoium does not have a position in any company mentioned. You can follow Travis on Twitter at @FlushDrawFool, check out his personal stock holdings or follow his CAPS picks at TMFFlushDraw.

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