Switzerland’s Roche and partner Chugai Pharmaceutical have taken the unusual step of announcing that they will conduct preclinical research on the influenza drug Tamiflu, as fears grow in Japan over a possible link between the drug and abnormal behaviour.

The news comes after it was revealed that the number of people confirmed to have behaved abnormally after taking Tamiflu (oseltamavir) has risen to 211, according to Japan's Ministry of Health, Labour and Welfare, up from 128 in April. Earlier this year, the ministry issued warnings against prescribing Tamiflu to teenagers, prompted by a number of cases of young people jumping from buildings after taking the drug.

The ministry also said it would launch a full investigation into whether there was a causal link between the drug and psychiatric problems, having previously maintained that there was no link. Roche and Chugai have continuously noted that no causal relationship has been established between Tamiflu and neuropsychiatric symptoms, but have still decided to do a series of back-to-basics studies on the compound.

These will include conduct additional preclinical research such as toxicity studies using rats (for behaviour and brain transfer studies, as well as clinical studies on the effects of Tamiflu on sleep, and the drugs transport to cerebrospinal fluid. "We are taking the situation seriously and are increasing our efforts to look into whether there is any causality and raise the level of safety measures," Chugai said, adding that it “places the highest priority on assuring patient safety, and as such is continuing to promote its appropriate use along with revision of the package insert”.

The firms’ response has been applauded by the MHLW and the move highlights the importance of the product to the companies. Chugai estimates that some 35 million people have taken the drug, which accounts for around 70% of the world's Tamiflu prescriptions.

Roche Diagnostics buys NimbleGen for $272.5 million

Meantime, Roche has signed a definitive agreement to acquire privately-held NimbleGen, a Wisconsin, USA-based company that specialises in high-density DNA microarrays.

Under the terms of the deal, the Basle-based firm is paying $272.5 million and Severin Schwan, head of Roche Diagnostics, said that the acquisition “represents a further milestone in our strategy to strengthen our position as a major player and complete solution provider in the genomics research market by extending our activities into the microarray segment". He added that NimbleGen’s technology is “highly synergistic and will complement the existing Roche portfolio of innovative genomic research tools” such as the high-throughput sequencing systems from the recently acquired company 454 Life Sciences.

Roche plans to maintain NimbleGen’s facilities in Wisconsin as well as its centres in Reykjavik, Iceland, and Waldkraiburg, Germany, plus the company’s 140 employees. The transaction is expected to close in the third quarter.