Despite reports in August 2008 that two multiple sclerosis (MS) patients taking Tysabri had contracted the same potentially fatal brain infection, progressive multifocal leukoencephalopathy (PML), that caused Biogen to withdraw the multiple sclerosis treatment in 2005, Tysabri prescribing will not be significantly impacted for most neurologists, as usage continues to trend upward since its 2006 reintroduction, according to new research by GfK Healthcare.

The study showed that while 89 percent of neurologists had heard news of the recent PML cases, 62 percent responded that the negative news would not impact their prescribing, although 32 percent said it would limit it. Currently, the vast majority of neurologists – more than 80 percent – prescribe Tysabri, up from 73 percent in 2007 and 50 percent in 2006.

Neurologists believe the benefits offered by Tysabri outweigh the risks of developing PML and other infections, or having an allergic reaction. Notably, neurologists who have had clinical experience with pipeline drugs are more likely (5.40 on a seven-point scale) to agree that Tysabri’s efficacy benefits outweigh its safety risks, whereas neurologists who don’t have clinical experience with pipeline drugs are somewhat less likely (4.71) to agree with the same statement. However, GfK Healthcare’s research revealed that 88 percent of neurologists have not referred a patient to another physician for a Tysabri prescription.

“Looking at the data that showed neurologists who have clinical experience with Tysabri are more supportive of its benefit/risk profile may suggest an opportunity for Elan/Biogen to focus efforts toward these doctors to help minimize the occurrence of PML, as these are potentially better-trained doctors at managing this issue and selecting patients correctly to trial Tysabri,” said Kim Lazarus, Vice President and Category Business Leader, Neurology, for GfK Healthcare.

Patient reluctance to take Tysabri due to PML fears could, however, thwart neurologists’ increased use of the agent. While news of the most recent PML cases has reached only one-quarter of MS patients, negative associations with past PML cases still resonate. GfK Healthcare’s research with MS patients revealed that almost 60 percent of patients “very much agree” they are hesitant to begin taking or re-taking Tysabri because of the recent safety issues (up from 45 percent in 2007 and 39 percent in 2006). Furthermore, almost 40 percent of patients “very much agree” that they would only consider taking Tysabri once they have failed on all other MS therapies (up from 28 percent in 2007 and 25 percent in 2006).

“Given physicians’ increasing comfort with Tysabri, as well as patients’ openness to discussing the drug, physicians will be essential in convincing patients that Tysabri’s benefits outweigh the risks – particularly for patients who have experienced treatment failures with other agents,” said Ms. Lazarus. “However, marketing efforts targeting patients themselves will be equally important, given the involvement that patients frequently have in MS treatment decisions. Ultimately, though, continued Tysabri growth will be dependent upon how physicians and patients together balance the product’s efficacy versus safety concerns, and whether the frequency of PML cases remains low.”

Contact: Kim Lazarus, VP, Category Business Leader, Neurology
kim.lazarus@gfk.com