(Bloomberg) -- Billionaire investor Carl Icahn upped his criticism of Illumina Inc.’s acquisition of Grail Inc., saying in his latest attack that its board set a “new low” in governance by pursuing the deal over antitrust regulators’ objections.

Illumina’s board of directors “elected voluntarily to declare war on antitrust regulators” by closing the $7 billion transaction in 2021 even as the EU moved to block it, Icahn said in a letter published Friday. Board members sought to protect themselves by taking out “an unprecedented level” of additional personal liability protection when the deal closed, Icahn said, citing a Securities and Exchange Commission filing.

Illumina said in a statement that all public US companies regularly review their insurance for directors and officers, and it’s not uncommon for coverage limits to be increased during an acquisition.

The San Diego-based company is fighting Icahn’s efforts to install three directors on its board. Illumina reiterated Friday that it believes those nominees are unqualified.

Grail emerged from Illumina’s accelerator program and was spun out in 2016. In 2020, Illumina said it would acquire Grail “to launch a new era of cancer detection.”

In his new letter, Icahn focused on the move by Illumina’s board move to protect itself from blowback related to the acquisition.

“Neither that SEC filing, nor any previous or subsequent SEC filing, press release or public statement by Illumina’s board contains any hint regarding what this agreement is, what it means or why it was adopted,” Icahn said. “And until the directors are deposed, the owners of the company will never truly know what fears prompted them to demand the execution of this agreement as a condition to their acquiescence to management’s maniacal desire to punch antitrust regulators in the face.”

Illumina shares rose 1.4% in New York. They’re up about 9% this year.

(Updates with Illumina statement in third paragraph.)

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