Slaughter & May and Cleary Gottlieb Steen & Hamilton have been appointed to advise GlaxoSmithKline (GSK) on selling half its stake in South African drug maker Aspen for $853m (£574m).

GSK said it would sell 28.2 million shares in Africa’s biggest generic drug maker, or half its 12.4% holding, in a share placing run by Citigroup and UBS.