* Epanova approved to reduce triglyceride levels
* AstraZeneca acquired drug after buying Omthera in 2013
* Sales seen at $322 mln by 2018 - consensus forecast (Adds details on drug, sales forecast, background)
LONDON, May 6 (Reuters) - AstraZeneca Plc has won U.S. approval for Epanova, a new pill for heart disease, providing a welcome - but relatively minor - piece of good news as it fights a $106 billion takeover approach from Pfizer Inc .
Epanova will be entering a crowded market for fish oil-based cardiovascular drugs, limiting its commercial potential. However, the fact that AstraZeneca secured approval on schedule is a sign that the company is delivering on its pipeline hopes.
"This approval is a significant milestone for AstraZeneca, as it strengthens our existing portfolio of cardiovascular medicines," Briggs Morrison, global head of medicines development, said in a statement.
Industry analysts, on average, expect Epanova sales to reach a relatively modest $322 million a year by 2018, according to Thomson Reuters Pharma.
The new pill is designed for treating people with very high levels of fatty triglycerides in their blood and was originally developed by Omthera Pharmaceuticals, which AstraZeneca acquired last year for up to $443 million.
The acquisition was one of a series by Chief Executive Pascal Soriot to revive AstraZeneca's fortunes through bolt-on deals.
Epanova is an ultra-pure mixture of the free fatty acid forms of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), derived from fish oil.
The new drug will compete with other fish oil-based medicines such as GlaxoSmithKline Plc's Lovaza, which now faces cut-price generic competition, and Amarin Corp Plc's Vascepa.
AstraZeneca also hopes to develop a fixed-dose combination of its cholesterol-lowering drug Crestor and Epanova. The new combination, if successful, would help extend the Crestor franchise beyond 2016, when the drug's U.S. patent ends. (Editing by Louise Heavens)