Irish biotech group Elan and its US partner Biogen Idec have won US clearance to modify the label of their multiple-sclerosis shot Tysabri with new safety information that may double the treatment's worldwide sales.
The Food and Drug Administration approved the revision that would help doctors identify patients with the highest and lowest risks of developing deadly brain infections linked to the drug, the agency said in a statement.
The news comes as one of the drug’s main rivals, Novartis’s Gilenya became the subject of a safety review by the European Medicines Agency.
The agency advised doctors yesterday to continuously monitor patients for six hours after giving them a first dose of Gilenya, casting a shadow over the potential blockbuster product, following reports of heart problems in patients and the death of one person in the United States within 24 hours of starting treatment.
The Swiss drugmaker said last month it was investigating whether Gilenya, seen by analysts as a potential multibillion-dollar seller, caused the death of the 59-year-old US patient.
Gilenya can temporarily slow the heart rate. Although this usually returns to normal after a few hours, the European watchdog recommended intense cardiovascular monitoring after the first dose.
Tysabri’s label change may push global sales to $2.5 billion to $3 billion by 2016, Michael Yee, an analyst at RBC Capital Markets in San Francisco, said in an interview.
Without the modification, sales may have reached $1.5 billion to $2 billion that year, Mr Yee said.
Tysabri increases the risk of progressive multifocal leukoencephalopathy, or PML, a viral infection in the brain that usually leads to death or severe disability, according to a boxed warning the drug's label has carried since 2006.
The new label will retain the boxed warning, the FDA's strictest caution, while adding a notification that patients who have antibodies against the JC virus are more likely to develop PML while taking Tysabri than people who don't have the antibodies.
Biogen and Elan developed a blood test known as a JCV assay to determine whether a person has the antibodies.
"The revision of the Tysabri label to include the use of the JCV assay as a risk-stratification tool is important for doctors and patients because it allows Tysabri to be most efficiently used in the safest group of patients," Mr Yee said.
The European Commission approved the label change in June, and the JCV test has been widely used by doctors in Europe since then, he said.
About 400,000 people in the US and 2.1 million worldwide have MS, according to the New York-based National Multiple Sclerosis Society.
Data collected by the companies shows a patient who tests negative for the antibodies may have one chance in 10,000 of developing PML while taking the drug, Mr Yee said.
Without the use of the JCV test, patients are estimated to have a 1.5 in 1,000 risk of developing the brain illness after two years of treatment, according to the drug's label.
As of February 2011, 102 cases of PML had been reported among 82,732 patients treated with Tysabri worldwide, the FDA said April 22nd in its most recent safety update on the drug.
Tysabri won FDA approval in 2004 for multiple sclerosis, a neurological disorder that causes a person's immune system to attack healthy nerve cells. The risk of PML emerged after Biogen and Elan began marketing Tysabri, leading to the suspension of sales in February 2005. The drug returned to the market in June 2006 with a risk
management program for patients who didn't benefit from rival medicines after research showed it was twice as effective as other MS treatments.
Teva's Copaxone, Merck's Rebif and Bayer's Betaseron are among injectible MS treatments that compete with Tysabri.
Novartis's Gilenya, approved by the FDA in 2010, is the first pill to treat the condition.
MS drugs generally must be taken throughout a patient's life to reduce flare-ups and delay disability.
The worldwide market for MS drugs, now $10 billion to $11 billion, may grow to $15 billion in 2016, Mr Yee said.
Tysabri's share of the market, now about 10 per cent to 13 per cent, may grow to 20 per cent that year with the revised label, he said.
Bloomberg/Reuters