The company said full-year revenue would be in the lower half of its guidance range of 410 million to 440 million pounds, reflecting flat revenue for Varithena as demand was dampened by insurers currently taking significantly longer to settle claims than for established treatment options.

Analysts at Jefferies said the update on Varithena was "disappointing", and they expected the shares to fall around 5 percent, but they kept their "buy" recommendation, saying the current share price more than discounted the Varithena risk.

(Reporting by Paul Sandle; editing by Sarah Young)