TOKYO, May 16 (Reuters) - Takeda Pharmaceutical Co Ltd , Japan's biggest drug company, has no interest in acquisitions driven by tax benefits or synergies, its chief financial officer said, dismissing the forces behind Pfizer Inc's $106 billion offer for AstraZeneca PLC.

Takeda CFO Francois-Xavier Roger also rejected the idea that greater size would necessarily be an advantage for his company, the world's 12th largest pharmaceutical company.

"We don't believe that being huge is necessarily good. You lose flexibility and agility. Agility is something we value because it allows you to move fast," Roger told Reuters in an interview on Friday.

Pfizer's pursuit of Britain's AstraZeneca, which has so far been rejected, is driven in large part by the prospects of a lower-tax domicile in the UK, and has spurred expectations of similar offers.

Tax savings could be a particularly compelling motive for Japanese companies, which pay among the highest corporate tax rates in the industrialised world and have lobbied hard for reductions.

But Roger said tax and cost savings were not currently important considerations that could lure his company into an acquisition deal.

"To make a move just for cost-cutting and for tax is not an exciting proposal. You won't see Takeda doing that," he said.

"If we go back to acquisitions we would focus again on strategic acquisitions and what they bring to us. Millennium brought us access to oncology, so I have access to a new franchise and a better footprint in the U.S."

He did not dismiss tax and synergy benefits entirely from any M&A discussion, but added: "It shouldn't be the main driver."

Roger also played down the issue of size when asked about the behemoth that the industry would confront if the union between Pfizer and AstraZeneca were to go through.

"We don't feel any pressure," he said.

"For example, we don't have any objective whatsoever of being in the top 10 in the pharmaceutical industry. Today we are ranking about number 12. If this deal happens we will be number 11, and maybe one day we will be number 10. It doesn't really matter to us."

Citing the example of Abbott Laboratories, which spun off its patent-protected drugs last year, he said: "They went the other way, probably because they became too big. At the end of the day it's about being agile, being able to move fast, and being efficient in what you do." (Reporting by Chang-Ran Kim and Ritsuko Shimizu; Writing by Edmund Klamann; Editing by Mark Potter)