Hey Harry,

As you know, I've been a little freaked out at the number of patients who started and stopped Tysabri on its first approval and are now showing severe allergic reactions to it once they start the infusions again. Despite the warning to discontinue its use at that point -- listed in Tysabri's own prescribing info -- they're setting up those reactive patients to receive Benadryl infusions in conjunction with Tysabri to counteract future allergic reactions. Mind boggling...

Also on the Tysabri site they point out that starting, stopping, and starting it again may produce this type of hypersensitivity with monoclonal antibodies.


"The long-term immunogenicity of TYSABRIŽ and the effects of low to moderate levels of antibody to natalizumab are unknown. Experience with other monoclonal antibodies suggests that patients who receive therapeutic antibodies after an extended period without treatment may be at higher risk of hypersensitivity reactions than patients who received regularly scheduled treatment. It is not known if this will occur with TYSABRI (see WARNINGS, Hypersensitivity and ADVERSE REACTIONS, Infusion-related Reactions)."


This thread's discussion about the Crohn's patient reminded me of something else about his case that was documented in the NEJM article, so I pulled out my copy (I have dozens of Tysabri articles printed up and filed here). The Crohn's patient who came down with PML had also stopped Tysabri for several months and resumed the treatment later.

No JC virus appeared during any of his other drug treatments which, like Harry said, had ended months before the JC virus was finally noted in his system. No JC virus appeared during his first 3 Tysabri infusions or during the 9 months he was on placebo.

But...the JC virus showed up immediately after his Tysabri infusions resumed and the viral load increased substantially during the 5 infusions before he was admitted to the hospital. It's always bothered me that the Crohn's patient came down with PML after fewer infusions than the other patients, especially since he had been on placebo for much of the trial.

It was reassuring to think that Tysabri must be pretty safe for at least a couple of years, but now I think I'm even more freaked out. What if there's something else going on entirely? They just don't understand these drugs yet.

P.S. Many of us already knew that there is no test for PML, no treatment, and that its damage is permanent. I just don't think that fact has been stressed enough to potential patients who haven't followed the whole saga as closely as we have.

Check out the "Patient Medication Guide" and the "Product Information" on the Tysabri website
http://www.tysabri.com/product-information.html