Roche's Tamiflu Still Works In Swine Flu Despite Denmark Case

UNE 29, 2009, 11:31 A.M. ET

By Anita Greil

Of DOW JONES NEWSWIRES

ZURICH (Dow Jones)--Roche Holding AG (ROG.VX) said Monday that a patient in Denmark developed resistance to Tamiflu, but that the drug is still effective in the circulating H1N1 swine flu virus.

"Such a development had to be expected, and is no surprise from a scientific point of view," David Reddy, Roche's Pandemic Taskforce leader told journalists on a conference call.

The Danish patient, who has since recovered, was taking the drug as a prevention to avoid the contraction of swine flu, Reddy said. He was probably already infected with the virus, and resistance to the drug emerged because he was given the lower prevention dose.

This is a case of so-called drug-induced resistance, which is rare, but it was known from clinical studies that this can happen, Reddy said. Around 0.4% of adults, and around 4% of children, were shown to develop resistance to Tamiflu in clinical studies, he said.

Drug-induced resistance occurs when a patient who is taking the drug develops resistance. It differs from naturally incurring resistance, where a virus strain in itself isn't responding to the drug. This had been the case with the winter flu virus that was spreading in Europe in 2008, he added.

This isn't the case here, meaning that Tamiflu is still working against swine flu, and Roche thus expects the World Health Organization to continue to back the use of the drug, Reddy said.

At some point, there will certainly be resistance to Tamiflu, said Birgit Kulhoff, pharmaceutical analyst in Zurich with private bank Rahn & Bodmer.

"Sooner or later there will be resistance, and I would expect that to happen when the swine flu virus starts mixing with seasonal flu viruses," she said.

As such, an isolated case in Denmark doesn't yet change the sales prospects of Tamiflu. "It would have been much more worrisome if we saw repeated cases of resistance in the Southern hemisphere, where it's winter now, and the viruses could mix," she said.
hat-tip Dutchy