UK pharmaceutical producer GlaxoSmithKline has invited private equity firms to consider making offers for a range of its older drugs, news agencies report, citing people familiar with the matter.

The move is said to be part of a reshaping of the drugmaker's portfolio, which also involves a $20 billion asset swap with Novartis that will see the Swiss company acquiring GSK's oncology activities while GSK takes Novartis' vaccines business.

GSK chief Andrew Witty said last month that Britain's biggest pharmaceuticals company could dispose of individual medicines or a broader portfolio of older established products.