Europe's highest court upheld a 52.5 million-euro EU antitrust fine levied against British drugmaker AstraZeneca for blocking the entry of cheaper rivals to its then bestseller ulcer drug Losec.

"...The abuses must be characterized as serious infringements, and consequently the amount of the fine cannot be reduced for those reasons," the Luxembourg-based EU Court of Justice (ECJ) said in a statement on Thursday.

The General Court, Europe's second-highest, had backed the European Commission in 2010 against AstraZeneca, but cut the penalty to 52.5 million euros from an original 60 million.

The Commission, which acts as EU antitrust and competition authority, originally penalized AstraZeneca for actions that regulators said had kept Losec prices artificially high.

Regulators on both sides of the Atlantic have generally frowned on actions by brand-name companies to delay either the production or sale of cheaper medicines to protect their own products.

(Reporting by Foo Yun Chee; editing by Rex Merrifield)