No, the entire staff doesn’t have to pick up and move. But as of May, Andrew Witty plans to run the drugmaker’s affairs out of London, rather than officially use the US headquarters in Philadelphia as his base, which JP Garnier, the outgoing ceo, has done since 2001, The Times of London reports. Witty, who has run Glaxo’s European pharma biz, will work out of the Brentford office in what may amount to a “significant change in corporate structure,” the paper writes.

A Glaxo spokesman tells the paper Witty will remain in the UK, partly for family reasons, but emphasized there would be no “significant relocation of staff or resources” from Philadelphia to the UK. He added that Witty would visit the US frequently and Glaxo would continue to operate a “dual headquarters” split between the two cities.

The Philadelphia office, which employs 2,800 people, will continue to oversee global manufacturing, info technology, human resources and the consumer healthcare business that include brands such as the Alli diet pill. The US, where Glaxo employs 25,000 staff, generates roughly half of the annual sales of about $40 billion. London will continue to handle other functions, such as finance, legal and communications.

Glaxo’s decision to shift its focus reflects growing expectations that the US will be a less lucrative market for big medicine makers over the next few years because of increased industry regulation. Big drugmakers are also likely to expand in other regions, such as Asia-Pacific.