British pharmaceutical group GlaxoSmithKline plc (GSK) is planning to spin off a subsidiary that focuses on developing treatments for HIV.

Announcing its third quarter results this week, the company said that ViiV Healthcare has proved to be "a highly innovative and successful venture" with equity partners Pfizer and Shionogi, which each own a minority stake.

GSK itself currently holds 78.3 percent of the business, but said it was looking to sell a minority shareholding in an IPO. At this stage it is not clear whether Pfizer and Shionogi would keep hold of their stakes or decide to sell, but reports suggest they are likely to retain a share of the business to benefit from future growth.

Created five years ago as a joint venture between GSK and Pfizer, ViiV Healthcare operates in 16 countries. In the first nine months of 2014 it generated revenues of just over £1 billion ($1.6 billion) and made an operating profit of £675 million ($1.08 billion). The business could be valued at up to £15 billion ($24 billion).

GSK said that ViiV has made significant progress in both R&D and commercial execution, culminating in the recent launches of Tivicay and Triumeq.

GSK chief executive Sir Andrew Witty believes that the company would be ranked in the FTSE 100 somewhere between the top third and number 40.

"This is not a forecast, but this business will make a £1 billion profit this year if you simply grossed up the nine months' year-to-date on a straight line basis. That, I think, tells you straight away what the kind of underpinning profit number of this business might be," he commented.

As a group, GSK saw nine-month revenues fall 14 percent to £16.8 billion ($27 billion) and operating profit was down 37 percent to £2.9 billion ($4.6 billion).