Data points out paths to Tysabri rehab

The news that 23 Tysabri patients had developed the brain malady PML hit Biogen hard earlier this week. Some analysts now say that the estimated risk of developing PML--1 in 1,000--might actually be more like 1 in 400. But two new possibilities for fighting PML have emerged, raising hopes that the potentially fatal brain infection can a.) be better prevented, and b.) better treated.

As BNet Pharma reports, a disproportionate number of PML cases have occurred in Germany. Why might that be? Well, oversight isn't quite as rigorous there as it is in the U.S., where Tysabri use is governed by a strict risk-management program. By contrast, European distribution goes largely unrestricted. Also, Germany reportedly has been lax about making sure patients get completely free of other immunosuppressants before going on Tysabri, among other things. Biogen has been working with German clinics and academic medical centers to change that.

Meanwhile, a researcher at Elan--which discovered the drug--tells Forbes he's working on a diagnostic test that could screen patients for their risk of developing PML (progressive multifocal leukoencephalopathy). Tysabri suppresses the immune system, which can allow a dormant pathogen--the JC virus--to go into overdrive, causing PML. Previously, researchers thought 90 percent or more of us were infected with that virus, but Elan's Ted Yednock says his team has discovered an infection rate of 50 percent.

A diagnostic test could identify those patients who aren't infected, and thus are free and clear for Tysabri treatment. And those who have the virus could be closely monitored for symptoms.

- read the BNet post
- check out the story from Forbes