GlaxoSmithKline has been hit by a delay to one of the six key drugs on which it was awaiting regulatory decisions this year. The US Food and Drug Administration (FDA) moved the date when it will votes on whether to approve or reject GSK's experimental cancer drug Trametinib back to September 3rd 2013.The Prescription Drug User Fee Act (PDUFA) date has been delayed extended by three months in order to allow the FDA more time to analyse and review the submission.Chief executive Sir Andrew Witty last month said 2013 is "a key year for R&D pipeline delivery", with GSK counting on regulatory decisions on six drugs to help it boost sales by 1.0% this year.The group filed for US approval for trametinib in August 2012 and in February 2013 for European regulatory approval. Shares in GlaxoSmithKline had dipped 2.00p to 1,658.5p at 13.05 on the day of the announcement. OH