GlaxoSmithKline shares fall on threat of competition to its HIV drug

The threat of slowing demand and new competition in GlaxoSmithKline’s flagship HIV drug business has unnerved investors in the UK’s biggest drugmaker, sending its shares down 1.8%.

The company pared some losses but remained among the top losers in London’s FTSE-100 index after Citigroup downgraded the stock to neutral from buy and cut earnings forecasts by up to 9%.

HIV medicines, which GSK sells through its ViiV Healthcare unit, have been star performers in recent years and chief executive Emma Walmsley said in April that the “HIV portfolio continues to go from strength to strength”.