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 Omthera Pharmaceuticals (NASDAQ:OMTH), a developer of clinical therapies to treat cardiovascular diseases, doubled in intraday trading today following the announcement that AstraZeneca (NYSE:AZN) is purchasing the company.

So what: The details of the acquisition are that AstraZeneca will pay $323 million for Omthera, with the option of an additional $120 million in future payments based on the performance of Omthera's pipeline. The deal could therefore be worth as much as $443 million when all is said and done. The reasoning behind the acquisition is that it allows AstraZeneca to get in on the rapidly growing fish oil market designed to treat high levels of triglycerides and high-risk patients with cardiovascular disease. Omthera's most exciting product in development is Epanova, a fish oil capsule currently in late-stage trials.

Now what: Omthera shareholders certainly made out like bandits today, just a month after the company went public. While it's certainly a boost for Omthera with the financial backing of AstraZeneca, it's a crushing blow to Amarin (NASDAQ:AMRN) and its FDA-approved fish oil treatment Vascepa. Amarin has long been thought to be the buyout candidate based on its triglyceride-lowering fish oil treatment, yet Omthera, at roughly 45% of Amarin's market value, garnered the interest from big pharma. Worse yet, AstraZeneca can kick in its marketing expertise if Epanova is eventually approved. Today is certainly a case of one company's pain being another's gain!

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Fool contributor Sean Williams has no material interest in any companies mentioned in this article. You can follow him on CAPS under the screen name TMFUltraLong, track every pick he makes under the screen name TrackUltraLong, and check him out on Twitter, where he goes by the handle @TMFUltraLong.

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