UPDATE 1-Illumina decision to close Grail deal disappointing, EU says

(Adds fresh Commission quotes, details)

BRUSSELS, Aug 19 (Reuters) - EU antitrust regulators on Thursday expressed disappointment at U.S. life sciences company Illumina’s decision to complete its takeover of cancer detection test maker Grail and warned that gun-jumping could lead to hefty fines.

Illumina late on Wednesday said it had closed the deal and will treat Grail as a separate company. The move came amid an ongoing EU investigation and ahead of an Aug. 24 trial by the U.S. Federal Trade Commission, both of which have voiced concerns about the impact of the deal.

The European Commission, which acts as the competition watchdog for the 27-country European Union, said in an emailed response to Reuters queries that it had taken note of Illumina’s announcement.

“The Commission... regrets the decision by Illumina to proceed with the closing of its acquisition of Grail, while the Commission’s review of the proposed transaction is still pending,” a spokesperson said.

EU merger rules require companies to notify the EU antitrust enforcer and get its approval for their deals before they can close them under a clause called the standstill obligation.

“The Commission attaches great importance to this obligation which is one of the cornerstones of the Merger Regulation and takes breaches of such obligation very seriously,” the spokesperson said, adding that the EU can open a separate investigation which can lead to fines.

Breaches can lead to fines of as much as 10% of the aggregate turnover of the companies. In 2018, French telecoms group Altice was hit with a 125-million-euro ($146 million) fine for closing its 2015 takeover of PT Portugal before gaining regulatory approval.

Illumina did not immediately respond to a request for comment.

$1 = 0.8554 euros Reporting by Foo Yun Chee; Editing by Susan Fenton and Tomasz Janowski