Elan and Biogen Idec will return their multiple sclerosis drug Tysabri to the market next month, but have hiked the price by 20%.

The Irish drugmaker plans to sell Tysabri (natalizumab) at an annual cost of $28,400 in the USA, up from the $23,500 it charged before the drug was removed from the market last year after being linked to a serious brain disease called progressive multifocal leukoencephalopathy (PML).

Tysabri was cleared to return as a second-line treatment for MS after Elan and Biogen Idec conducted additional trials to explore the frequency of the side effect. The US Food and Drug Administration restored its license last week, on the understanding that patients due to receive it would be treated at registered medical centres and undergo regular imaging tests to check for PML.

In March, an FDA advisory committee voted 12-0 in favor of returning Tysabri to the market as a monotherapy. Meanwhile, in Europe the Committee on Proprietary Medicinal Products for Human Use (CHMP) said last month that Tysabri should return to the market, and a final ruling on the matter is expected in the next few weeks.

The increase in cost to $2,185 per single-use, 300mg vial – given every four weeks - was a result of price inflation and the additional costs of studies used to support the reintroduction of the drug, according to analysts.