Roche, the Swiss pharmaceutical group, is funding a study to test the efficacy of its flu drug Tamiflu in combination with rival GlaxoSmithKline’s Relenza, in one of several initiatives to extend further the market for its blockbuster antiviral treatment.

David Reddy, Roche’s pandemic taskforce leader, said on Monday his company was supporting research by a French team analysing whether patients could be better treated by using both of the two drugs, which are closely related chemically.