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 drugmaker Regeneron Pharmaceuticals (Nasdaq: REGN) soared 17% in intraday trading Wednesday on a fresh round of worries over Roche's rival eye-disease drug Avastin.

So what: This latest bit of bad news -- Bloomberg reports that the Department of Veterans Affairs has stopped using Avastin -- simply reinforces the notion that Regeneron's own ophthalmic-drug candidate, Eylea, might eventually have the market all to itself. In fact, the stock even hit a new 52-week high of $79.90 earlier in the day.

Now what: I'd continue to be cautious about jumping into the shares. Eylea's potential is certainly exciting, but I'm worried that Regeneron's valuation -- the shares are up nearly 200% over the past year -- might already have plenty of optimism baked into it. Of course, with the FDA scheduled to rule on Eylea in November, investors won't have to wait very long to see the action.

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

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.