(Reuters) -GSK shares fell more than 6% on Friday to the bottom of Britain's blue-chip index after a U.S. FDA advisory panel recommended against approving its blood cancer drug Blenrep, citing earlier concerns over side effects.

GSK Plc shares tumbled after its blood cancer drug failed to secure the backing of a panel of US regulatory advisers, putting its approval in doubt.

GSK has failed to win the backing of influential advisers to the US drugs regulator for a key blood cancer drug, putting its approval in doubt and sending shares in the pharmaceutical group 7 per cent lower on Friday morning.