GlaxoSmithKline has started a pivotal study testing intravenous zanamivir against Roche’s best-selling pill Tamiflu as a treatment for patients hospitalised with influenza, it said on Wednesday.

Intravenous zanamivir is not currently approved for sale in any country, but the medicine has been available since 1999 in inhaled form under the brand name Relenza. GSK licensed the product from Australia’s Biota.

GSK’s Phase III trial, which will measure the time to clinical response in patients with confirmed flu, aims to enroll 462 patients in 20 countries and will take around three years to complete.

The British drugmaker had previously said it planned to develop an intravenous form of zanamivir to help the sickest patients, following clinical reports it might help when other treatment options failed.

British doctors said in 2009 they saved the life of a woman with severe H1N1 swine flu after giving her unlicensed intravenous zanamivir. The patient, whose immune system was impaired due to recent chemotherapy, did not respond to Tamiflu.

(Reporting by Ben Hirschler, editing by Kate Kelland and Will Waterman)

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(Reuters)