LONDON –

One of the top 10 shareholders in drugmaker Takeda Pharmaceutical Co. is "skeptical" about the value that will be created from the group's $62 billion takeover of rare-disease specialist Shire PLC, the Sunday Times reported, citing the unidentified investor.

The deal, the biggest in Osaka-based Takeda's history, has already faced opposition from a group of investors that calls itself "Thinking About Takeda's Future."

It comprises former Takeda employees and shareholders who together own about 1 percent of the company's stock and who oppose Takeda's expansion. Concerns have also been raised about Takeda's debt after the acquisition, which includes a $31 billion loan.

The Sunday Times reported the shareholder said the deal had come as a "surprise" and raised concerns about the ability of Takeda to cut costs and improve shareholder returns.

"There will be some value distraction from the deal," the shareholder told the newspaper. "That's why we are skeptical."

Takeda shareholders, however, gave their indirect backing for the takeover in June by voting down a proposal requiring prior approval for any acquisitions larger than ¥1 trillion, or around $8.9 billion.

Takeda is also understood to have plans to address the debt concerns. It is reportedly considering selling Shire's Xiidra eye treatment when the deal is completed and may also offload Shire's Natpara, which is used to control blood calcium levels.

The Japanese group is in the process of completing the country regulatory approvals it needs to complete the deal, most recently getting passage for the takeover in China. Further regulatory approvals remain before the companies' shareholders will get a vote.

A Bloomberg News survey of 25 M&A and event-driven desks, equity analysts and fund managers found that participants expect the deal to be completed in March, in line with Takeda's original guidance.