RevisedTysabri® Update: No New Cases of PML; Re-release Possible; Potential Risks Still a Concern

August 18,2005

Good News for Patients Previously on Tysabri®…No new cases of PML

Biogen Idec and Elan Corporation, makers of Tysabri® (natalizumab), have conducted a safety evaluation of patients who previously took Tysabri. Any unusual responses to the drug are being investigated and reported to the FDA. Three cases of progressive multifocal leukoencephalopathy (PML) have resulted in two deaths so far in patients on Tysabri. PML is an often-fatal brain disorder thought to be caused by the activation of a virus known as the “JC Virus.”

According to a press release from Biogen Idec and Elan, dated August 9, 2005, no new confirmed cases of PML have been discovered. Almost 2,000 MS patients from clinical trials participated in the safety evaluation. With no additional cases of PML among patients exposed to Tysabri, Biogen Idec and Elan are taking preliminary steps to restart clinical trials in MS.

A safety evaluation of Tysabri-treated patients with Crohn’s disease or rheumatoid arthritis is also ongoing. Results are expected to be announced by the end of the summer.

Background on Tysabri and PML

To review, Tysabri was given early approval in November 2004 by the Food and Drug Administration (FDA) for the treatment of MS. The drug had shown initial success in clinical trials and was expected to be a strong candidate for the long-term treatment of MS. The drug was voluntarily suspended, however, in February 2005 after PML was confirmed in two patients taking both Tysabri and Avonex® (interferon beta-1a).

The first patient died and the second patient is reported to be improving. A third case was discovered upon the re-examination of a patient who took Tysabri in the treatment of Crohn’s disease and died in 2003.

Early test for virus may provide hope for Tysabri’s return

A letter from three doctors at Biogen Idec may be viewed on the New England Journal of Medicine’s website at http://content.nejm.org. The correspondence states that while little is known about PML and the JC virus, studies suggest that PML is not uniformly fatal, and cases of PML may be preceded by the JC virus.

The letter also notes that a test may be able to determine the presence of the JC virus in a patient’s plasma. The doctors speculate that through early diagnosis, Tysabri treatment might be discontinued in time to allow patients to recover, providing hope for some that Tysabri may return to the marketplace. So far this remains a theoretical possibility only, since Tysabri therapy has been stopped in all clinical trials.

Risks may still exist

According to The Wall Street Journal’s press release dated June 9, 2005, Dr. Joseph Berger from the University of Kentucky Medical Center has some concerns. He warns that while the idea of early diagnosis and recovery is a possibility, Tysabri does carry significant associated risks.

For instance, the studies being reviewed only have a few years of data available, and the risk of developing PML could potentially increase after more years of treatment. Additionally, Tysabri remains in the body for three months after treatment is stopped, which could increase the risk of developing PML even if the treatment is discontinued following the discovery of the JC Virus. This most-recent Biogen Idec/Elan press release helps to alleviate some of the fears that patients might still develop PML after Tysabri treatment has stopped.

Some of the information for this writing was obtained from the New England Journal of Medicine (at http://content.nejm.org), Reuters, and The Wall Street Journal.

Written by Susan Courtney, MSAA Senior Writer

Reviewed by Dr. Jack Burks, MSAA Vice President and Chief Medical Officer

For more information on Tysabri®, please see: "Antegren
Update," "FDA Approves Tysabri® (formerly Antegren) for the Treatment of Multiple Sclerosis" , "Voluntary Suspension of Tysabri® (Natalizumab) Marketing."   and  Anyone wishing additional information about MS and its treatments may contact MSAA's Helpline consultants by calling (800) 532-7667. Media questions should be directed to Andrea Borkowski at (800) 532-7667, ext. 123.

.

Read all the Latest News...