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Analysts back Tysabri return despite FDA concern

Market predicts MS drug will be back on the market, with restrictions

Analysts are backing a return to market for Elan's and its US marketing partner Biogen's controversial multiple sclerosis drug Tysabri despite the US Food and Drug Administration's (FDA) concerns over the two companies' plan to manage the safety risks.

Tysabri was withdrawn a year ago after two patients taking it in combination with another Biogen MS drug, Avonex, developed a rare and often fatal brain infection known as progressive multifocal leukoencephalopathy (PML).

A panel of FDA medical experts has begun discussing Tysabri's risk-benefit profile and whether to allow the drug back on to the market. But one day before the meeting was due to start, an FDA staff team made public its concerns in a report posted on the FDA's website. It said that under Elan and Biogen's safety plan, Tysabri could be prescribed to patients ìwhere the potential clinical benefits have not been demonstrated to justify the potential risk of PMLî.

Such patients were referred to as those with ìless severe forms of the diseaseî or who suffer from other conditions, such as Crohn's disease.

However, most analysts believe Tysabri will come back on the market, albeit with restrictions.

ìClearly the drug is going to come back,î said William Tanner, analyst at Leerink Swan & Co. ìThe drug safety people are not asking them to reinvent the wheel. They're asking them to be more rigorous in their risk-minimisation plan.î

Some analysts said it was hard to gauge the importance of the FDA staff team report, given that Elan and Biogen have not disclosed their safety plan. The report showed that the firms had proposed voluntary enrolment of Tysabri patients in a programme designed to educate them and their doctors about the risks of PML. After FDA objections, they agreed to make enrolment mandatory.

Last month, Elan and Biogen were given the go-ahead by the FDA to resume clinical trials of Tysabri. Both Elan and Biogen have said they expect to be allowed to resume marketing Tysabri for MS later this year, although analysts have warned that the FDA panel will include some external experts not involved in the decision to allow clinical trials.

Meanwhile, an article in late February in the British Medical Journal argued that Tysabri was approved too quickly and probably should not go back on the market without more data. ìThe rate at which Tysabri was first tracked is absolutely unacceptable for a condition like multiple sclerosis, which can last for 30 years,î said the author, Dr Abhijit Chaudhuri, a consultant neurologist for the Essex Centre for Neurological Sciences at Oldchurch Hospital. ìThey did not even look into the side effects and this is unbelievable. It's a major failing.î

30th September 2008


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