Shares of Biogen Idec (NASDAQ: [[ticker:BIIB]]) are climbing back up today after taking a dip yesterday on news that Tysabri, which Biogen markets in partnership with Ireland’s Elan, may cause liver damage. The stock closed down a couple of percent yesterday, at $60.13, but was trading back up around $61 at noon.
To be clear—and maybe this is aiding the bounceback in Biogen’s share price—the liver risk is not really new news. According to FDA spokesperson Sandy Walsh, it was discussed back in July when an FDA advisory committee met to consider the approval of Tysabri for Crohn’s disease. (Tysabri had previously been approved for treating multiple sclerosis.) What’s more, language warning about the risk was added to the labeling for the drug in January, when the Crohn’s approval was granted. The reason it popped up on the radar screen yesterday, she says, is that the manufacturers voluntarily decided to send a letter to physicians to ensure that they were aware of the warning.
In the letter, Biogen and Elan write that some patients treated with Tysabri have had elevated blood levels and other signs of liver damage as early as six days after their first treatment. What’s more, these sorts of signs recurred in some patients who were “rechallenged” with the drug, “providing evidence that Tysabri caused the injury.” The letter warns that treatment with Tysabri should be halted in patients with jaundice or other evidence of liver damage.
The new warning is based on 28 cases of liver damage observed in postmarketing surveillance of Tysabri users, according to an article by Bloomberg reporters Luke Timmerman and Catherine Larkin. In each case, the injury was reversible, and none of the patients died or required a liver transplant, the Bloomberg piece adds.
A host of different types of drugs cause liver side effects and, given that more than 21,000 patients were taking Tysabri at the end of last year, the risk associated with Tysabri doesn’t look to be a huge one. It likely came to light because Tysabri is one of the most closely scrutinized drugs out there. It was pulled from the market in 2005 after three users developed a dangerous brain infection called progressive multifocal leukoencephalopathy (PML) and reintroduced the next year under a strict prescribing and monitoring program.
But even though no Tysabri users have developed PML since the drug’s reintroduction, the drug’s safety profile is, for some, an ongoing source of skittishness. Indeed, many believe that it’s a big part of what tanked Biogen’s attempt to find a buyer for the company late last year. Our sources say that billionaire investor Carl Icahn, who has agitated for a Biogen sale, understands he’ll likely need to wait for safety data on Tysabri to accumulate and quell would-be buyers’ fears. Of course, if the company continues to have to add warnings to the label, even relatively mild ones, the additional time and scrutiny could have the opposite effect.
