Tysabri relaunch mooted for next year

In a report prepared by NCB Stockbrokers, senior analyst Dr Orla Hartford has reviewed the data available in Elan drug Tysabri's Biological License Application (BLA) in an attempt to understand why PML developed in two multiple sclerosis patients on Tysabri and AVONEX combination treatment.

The analysis revealed that, after a relatively short period of combination treatment, AVONEX had a significant effect on the accumulation, clearance and half-life of Tysabri and essentially led to almost double the intended Tysabri concentration after only 20 weeks of treatment.

Patients on Tysabri alone did not accumulate the drug.

Dr Hartford said: “This suggests to us that over a sustained period of Tysabri and AVONEX treatment, the trends of accumulation and reduced clearance of Tysabri leads to an "overdosing" of patients with Tysabri.

“Given Tysabri's mechanism of action, we suggest a possible explanation for the occurrence of PML in patients on combination treatment. The absence of confirmed cases in the monotherapy group (without a complicating factor) gives us comfort in our thesis.”

“We believe that the potential oversuppression of the immune system in patients on Tysabri and AVONEX combination treatment will form a central plank of the case made to the FDA for the re-launch of Tysabri (as a monotherapy).

“The efficacy of Tysabri in treating multiple sclerosis is undeniable and we continue to believe that Tysabri will return to the market as a significant therapy.

“We are assuming a re-launch in 2006 with the product achieving 10% market penetration in the multiple sclerosis market in the US and in Europe by 2009.”