[Update: 10/23/09, 1:10 pm Eastern] Shares of Biogen Idec and its Irish partner Elan dropped this morning after European regulators said they are taking a new look at the risk and benefit of natalizumab (Tysabri) for multiple sclerosis, now that 23 patients on the drug have been diagnosed with a rare, potentially fatal brain infection called PML.
Cambridge, MA-based Biogen (NASDAQ: BIIB) fell 5.5 percent to $44.61 at 11 am Eastern time today, while Elan (NYSE: ELN) dropped 21 percent to $5.11. The European Medicines Agency said it has initiated the review to discuss any additional measures necessary to ensure the safety of natalizumab, according to a Reuters report.
The new report was bound to alarm some investors, because 23 cases of progressive multifocal encephalopathy, or PML, is significantly more than the tally of 13 cases the FDA counted last month. Cases of PML been adding up since the drug was re-introduced to the U.S. market in July 2006 after it was previously withdrawn because of the risk. Despite the chance of the infection, which the FDA pegged at about 1 in 1,000, patients have continued to seek out the treatment, which physicians say is the most effective therapy on the market for multiple sclerosis. (Natalizumab is also approved as a treatment for Crohn’s disease.) More than 46,200 people worldwide were taking the drug at the end of September, Biogen said earlier this week.
Biogen finance chief Paul Clancy told Dow Jones earlier this week that the company will discuss how to communicate the link between long-term use of the drug and increasing incidence of the dangerous side effect.
Regulators might choose to recommend that patients who take the drug for long periods of time take breaks, or “drug holidays,” said analyst Christopher Raymond of Robert W. Baird & Co., in a note to clients this morning. Since so many patients depend on the product to control their symptoms, it’s unlikely that regulators would force it off the market, he said.
“We deem it highly unlikely that either FDA or EMEA would pull Tysabri from the market,” Raymond said. “With PML risk well known, we think the most likely scenario would be additional labeling restrictions suggesting perhaps a drug holiday after an extended treatment period.”
[Updated comment from Biogen Idec.] There isn’t any data that suggests imposing a drug holiday would reduce the risk of patients getting PML, but there is data that shows symptoms of multiple sclerosis return quickly once patients quit taking natalizumab, says Biogen Idec spokeswoman Naomi Aoki. The company is talking with regulators about the best way to update the drug’s prescribing information to reflect the increased risk with extended usage, but even so, the incidence of PML still appears within the stated range of 1 in 1,000 patients, she says.
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