(Reuters) -GSK shares fell more than 6% on Friday after a U.S. FDA advisory panel recommended against approving its blood cancer drug Blenrep, citing earlier concerns over eye-related side effects.

The British drugmaker was trying to revive the drug, which was pulled from U.S. markets in 2022 after failing a late-stage study. GSK's renewed application is based on two late-stage trials showing that Blenrep, when used in combination, improved overall survival in patients.

The setback from the U.S. FDA advisory vote comes at a time when GSK is focusing on expanding its pipeline to offset declining sales from top drugs and vaccines.

The company's shares fell as much as 7% to 1,315 pence, and were the top percentage loser on London's blue-chip FTSE 100 index, which was up 0.2%.

The FDA is due to give a formal decision on Blenrep next week, and analysts at Berenberg and JPMorgan said the regulator is unlikely to approve it then.

The FDA typically follows the advice of its advisory panels, though it is not bound to do so.

"GSK remains confident in the benefit/risk profile of Blenrep and will continue to work closely with the FDA as they complete their review for Blenrep," the company had said in a statement on Thursday.

The company has forecast peak annual sales for Blenrep, chemically called belantamab mafodotin, of over 3 billion pounds ($4 billion). The therapy is currently under review for approval in more than 10 countries.

Including Friday's losses, GSK shares are down about 2% for the year.

($1 = 0.7449 pounds)