LONDON - There is no clear evidence that Roche's widely used drug Tamiflu prevents complications such as pneumonia in people with flu, a group of medical experts said on Tuesday.

Governments around the world have mobilized Tamiflu stockpiles to fight swine flu but an updated review of past clinical trial results found there was insufficient data to know if the medicine cut complications in otherwise healthy people.

Roche contested the finding and said it stood behind the robustness and integrity of previous data showing a benefit.

Sales of the antiviral drug, also known by the generic name oseltamivir, have soared since the start of the current H1N1 flu pandemic in April due to massive government orders.

That has provided a windfall for the Swiss drugmaker, which said in October it expected Tamiflu revenue to reach 2.7 billion Swiss francs ($2.65 billion) this year.

The latest analysis, which updates an earlier 2006 review, was published online by the British Medical Journal, whose editor-in-chief, Fiona Godlee, said it left important questions about Tamiflu's effectiveness unresolved.

Governments around the world have spent billions of pounds on a drug that the scientific community now finds itself unable to judge, she said.

The BMJ report was also the subject of a Channel 4 News story on British television.

At issue is whether or not certain previously published trials on Tamiflu should be included or excluded when analyzing the drug's effectiveness.

For the latest review, a team led by Chris Del Mar from Bond University in Australia looked at 20 trials -- but they decided to drop eight that were included in the earlier review because they were unable to independently verify the results.

As a result they concluded that while Tamiflu reduced flu symptoms by about a day they had no confidence in previous claims that it cut the risk of flu complications.

David Reddy, Roche's pandemic taskforce leader, said the expert group was wrong to exclude the data from the eight studies.

He told reporters that Roche would have supplied full data on the contested studies if the investigators had signed confidentiality agreements, which were drawn up to protect patients.

We fully stand behind the robustness of the data and the integrity of that data, particularly the efficacy and safety of Tamiflu, the conduct of our clinical studies and the publication process, Reddy said.

Tamiflu, which Roche manufactures under license from Gilead Sciences, has been commercially available for 10 years as a treatment for seasonal flu and used by around 68 million people worldwide.

The pill competes with another less widely used flu medicine from GlaxoSmithKline, called Relenza, which must be inhaled.

($1=1.020 Swiss francs)

(Editing by Greg Mahlich)

Review Medicine