Takeda Pharmaceutical Co. Chief Executive Officer Christophe Weber pushed back against dissident shareholders seeking to stop the drugmaker’s acquisition of Shire PLC, saying he won’t release minutes of boardroom discussions.

A group including members of Takeda’s founding family opposes the planned $62 billion (about ¥7 trillion) acquisition of the U.K.-listed biotech, which would rank as the biggest overseas acquisition ever by a Japanese company.

The investors plan to sue Takeda in a bid to obtain details of the board talks leading up to the May deal, trade publication DealReporter said last week.

“We discuss many confidential topics, and we think board minutes should remain confidential,” Weber said in an interview in London.

The planned transaction, which would vault the maker of cancer drug Ninlaro into the ranks of the world’s largest pharmaceutical giants and boost its pipeline of new medicines, is on track, Weber said.

Authorities in China, the U.S., Brazil and Japan have cleared the deal, leaving the European Union as the last major regulator to issue a decision. Takeda has offered to dispose of an experimental Shire treatment for Crohn’s disease, a malady of the digestive system, to win approval and is in discussions with the European Commission on the matter, Weber said.

Takeda plans to hold an extraordinary general meeting by Jan. 18 for shareholders to vote on the deal; Shire investors would get a separate vote around the same time.

While the Japanese company’s shares are down about 19 percent since its intentions were first made public at the end of March, Shire’s stock has gained 47 percent.

The dissident group represents fewer than 100 people and holds less than 1 percent of Takeda, Weber said.

A representative for the investors did not immediately reply to an email seeking comment.

Takeda said last week that Weber’s management team informed the board of its interest in Shire as early as September 2017. Directors were regularly briefed on Takeda’s due-diligence procedures and the takeover talks, according to Weber.

“They have a different vision of what Takeda should become,” Weber said. “It’s a question of being a global company versus a local company.”

The only way the company would relent on the request to release the board minutes, the CEO said, is if a court orders it. So far, he said, he’s unaware of any legal action by the dissidents, who argue that Weber railroaded the deal past directors with insufficient scrutiny.