A widely-used multiple sclerosis drug has caused a tenth person to develop a potentially deadly brain infection since being reintroduced three years ago.
Biogen Idec, manufacturer of Tysabri (natalizumab), revealed that since the drug went back on the market in 2006 there had been 10 cases of progressive multifocal leukoencephalopathy (PML) reported in multiple sclerosis patients across the world, the latest occurring on 23 June.
Since the start of the year, there have been six reported cases of PML, with three in June alone, while the other four cases occurred in the second half of last year.
The intravenous prescription drug was temporarily taken off the US market in 2005 due initial concerns of a link to PML but registered in Australia in November 2006.
Earlier this year, fears of a link to PML lead to the withdrawal of psoriasis drug Raptiva from the Australian market.
Two cases of PML associated with Tysabri were reported in the United States, with the rest occurring in other parts of the world, though Biogen Idec did not specify where.
In Australia, 2,201 prescriptions for Tysabri were issued under the Pharmaceutical Benefits Scheme in the past year costing the scheme $4.7 million.
According to Biogen Idec, 40,000 patients were currently using the drug and 56,700 have been treated with it across the world.
In the three years since Tysabri was reintroduced, the company said 24,900 patients took the drug for at least a year, 14,400 were on the therapy for 18 months and 6,800 patients took it for two years.
In the latest case of PML, the patient had been taking the drug for 30 months, and the majority of those who developed the condition had been on the therapy for at least a year.