Biogen Idec and Elan have filed to extend the uses of their multiple sclerosis (MS) drug Tysabri to include first-line therapy, which could represent a major new market for the blockbuster drug.
The filings for the new indication in the US and EU come on the back of the approval last year of a companion diagnostic that can be used to screen patients who may be susceptible to a rare but serious side effect of treatment.
The side effect – called progressive multifocal leukoencephalopathy (PML) and linked to infection with the JC virus – was first encountered in 2005 and resulted in Tysabri (natalizumab) being taken off the market just a year after it was launched.
The product was however reintroduced in 2007 after regulators agreed that its benefits outweighed its risks in some MS patients. In trials, Tysabri has been shown to slow disability progression by between 42 and 54 per cent and reduce annualised relapse rates by 68 per cent.
The new applications request an expanded indication that would include first-line use for people living with certain relapsing forms of MS who have tested negative for antibodies to the JC virus.
Even with labelling restricting its use to second-line therapy Tysabri sales have been buoyant, reaching more than $400m in the third-quarter of 2012, and analysts have suggested first-line use could add another $1bn to the product’s top line.
Growth has been in the high single digits, but this has been pegged back by the availability of the JC virus test, which has led to a proportion of patients previously on the drug discontinuing therapy after a positive test result.
Biogen Idec and Elan’s filing comes shortly after the launch of a second-generation JC virus assay with improved sensitivity and specificity to detect patients with low levels of JCV-specific antibodies.
As well as moving Tysabri into first-line use in relapsing MS, Elan and Biogen Idec are carrying out phase III studies to try to extend its uses to include patients with secondary progressive forms of the disease.