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 high-flying biotechnology firm Regeneron Pharmaceuticals (Nasdaq: REGN) are at it again, up as much as 14% earlier in the trading session, following better-than-expected first-quarter earnings and a much-awaited sales update on its blockbuster drug, Eylea.

So what: For the quarter, Regeneron reported a 52% increase in revenue to $232 million and a profit of $0.11. Both of these figures crushed Wall Street's expectations for the first quarter. The big news of the day was that Regeneron once again doubled its sales forecast for Eylea -- the second time it has done so in just a matter of months. Regeneron now expects sales of $500 million to $550 million, which far exceeds the $250 million to $300 million it forecast in February.

Now what: Any worries about competing treatments seem to be flying out the window. Eylea, which is used to treat wet age-related macular degeneration, is a cheaper alternative to Lucentis which is co-marketed by Roche (OTC: RHHBY) and Novartis (NYSE: NVS), but had raised worries that it could be pressured by Roche's Avastin, which is far cheaper and currently not an approved treatment for wet AMD. Those worries seem to be fading. I'm still not convinced that at 80-plus times forward earnings I'd consider the company a good buy here, but these guidance doublings are starting to change my tune.

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