Among the groups circling the assets, buyout firm Bain Capital has teamed up with Belgian over-the-counter drugs group Omega Pharma and Dutch private equity group Waterland to pursue a bid, the sources said.
Bids for the European portfolio are due Wednesday, with pharma groups including Sanofi, and private equity firms including Advent International and Avista, expected to be eyeing the portfolio, according to the sources.
Britain’s biggest drugmaker sold a range of non-prescription products in the US to Prestige Brands Holdings for £426m (€512.7m) in December, after failing to find a single global buyer.
That leaves a collection of painkillers, dietary supplements, stomach and other treatments up for sale in Europe, which people involved in the process said might fetch up to £500m. GSK and potential bidders declined or were not available to comment.
GSK has also yet to dispose of global rights to Alli, its over- the-counter weight-loss drug, which has been the subject of health concerns, and could be sold separately, people said.
By teaming up with Omega, Bain will be hoping it stands a better chance of securing a deal this time around.