Strong sales in developing markets helped drug giant GlaxoSmithKline offset weakness in Europe and the US to post a rise in first quarter profits.Turnover was down by 10% at £6.585bn, but earnings per share climbed by 5% to 32.2p.The sales decline was largely due to a slide in sales of pandemic related products, but underlying sales were strong. Emerging markets sales climbed by 23% to £830m while Japan saw a 53% rise to £465m. Sales in the US and Europe were down by 4% to £1.571m and 5% to £1.418m respectively.Emerging markets saw continued growth across most categories, while Japan benefited from strong sales of Cervarix, a cancer vaccine. US sales were hurt by higher discounts due to healthcare reforms. Government austerity measures hit sales in Europe.