Healthy Skepticism Library item: 838

Warning: This library includes all items relevant to health product marketing that we are aware of regardless of quality. Often we do not agree with all or part of the contents.

Publication type: news

Herper M.
Tysabri Is No Vioxx
Forbes.com 2005 Feb 28

Full text:

Just when it seemed the pharmaceutical business might finally gain some respite from the issue of drug safety, another serious side effect has cropped up.

This time, the problems lie with Tysabri, which was widely expected to become the top treatment for multiple sclerosis but now may have caused a rare brain disease in two patients. Its makers, Biogen Idec and Elan, have stopped selling it, at least for now.

“I think that it’s important for the MS patients to know that there are a series of drugs that can be used to control the disease,” says Howard Weiner, Director of the Partners’ Multiple Sclerosis Center at Brigham & Women’s Hospital. “Tysabri advanced our understanding of MS and the treatment of it in very real ways.”

Weiner consults and performs clinical trials for MS drugmakers, including Biogen and Elan.

The drug safety issue has officially reached biotech. But though the circumstances may remind investors of the withdrawal of Merck’s Vioxx earlier this year, it’s worth noting that the particulars are very different. When Merck pulled Vioxx from the market, many doctors had been fretting for years that the arthritis pill might cause heart attacks. Many lawsuits were filed before the drug was withdrawn. By contrast, Biogen Idec and Elan found out about these side effects within a matter of weeks and responded rapidly. Tysabri was approved by the Food and Drug Administration in November 2004.

Common side effects like increased heart attacks—the problem with Vioxx—are hard to discern with conventional clinical trials. But rare events like those that effect Tysabri are harder to pin down. Whatever else can be said about Tysabri, it is certainly no Vioxx.

Still for Tysabri’s makers, the news is disastrous. Shares in Biogen Idec, which sells Tysabri in the U.S., dropped 46% to $36.97. Shares in Dublin-based Elan, which invented the drug, fell 68% to $8.70.

Analysts differ on Tysabri’s prospects. Michael King, of Bank of America Securities, said in a note to investors this morning that there is still hope for Tysabri and that the market’s reaction was overdone. In contrast, Geoff Porges at Sanford C. Bernstein says that in the best-case scenario, Tysabri would get a black box warning—the most serious kind. “We believe resolution of this issue will take months,” Porges wrote in a note to investors, “not days or weeks.”

What exactly happened? In MS, the immune system strips the lining from the nerves. For some patients, that means paralysis and eventually death. Tysabri slowed the progression of the disease in clinical trials by suppressing the immune system. But now it seems that the drug may have caused an unexpected problem.

In two patients, the drug seems to have had a worse effect. In a rare condition called progressive multifocal leukoencephalopathy, a virus stripped the lining from their nerves in their brain much more quickly than MS would have. One patient died as a result.

The virus itself is very common but only causes the disease when the immune system is damaged. Both of the patients were also taking Avonex, a second drug made by Biogen Idec. It’s possible the virus would not have gained a toehold if the patients had been treated with Tysabri alone. But it’s also possible that long-term use of Tysabri alone is also dangerous when given for a long time.

“There’s no way to know,” says the Brigham’s Weiner. “The biological systems we work with are very complex.”

On a conference call this morning, Biogen Idec said that only 1,000 MS patients had been followed on Tysabri for more than two years. Chief Executive James Mullen said the smartest thing for Biogen Idec and for patients was to take a “step back” until it became clear what was causing the two cases of PML. While the analysis is ongoing, rival drugmakers such as Serono, Pfizer, and Teva may benefit. But over the long term, launching new treatments for this disease is only likely to get more difficult.