The risk of a relapse is two to three times higher in relapsing-remitting multiple sclerosis (RRMS) patients who switch from Tysabri (natalizumab) to an oral or other injectable disease-modifying therapy after two or more years of its use, than it is in those who stay with Tysabri, a large observational study found.
A return of disease activity was not found to exceed pretreatment levels in the patient group analyzed, the researchers noted.
But these findings highlight the importance of evaluating a person’s risk factors, including treatment duration and necessary “washout” time, before choosing to move from Tysabri to a different disease-modifying therapy (DMT).
The study, “Clinical outcomes in patients who discontinue natalizumab therapy after 2 years in the Tysabri Observational Program (TOP),” was published in the Multiple Sclerosis Journal.
Tysabri, marketed by Biogen, is an antibody-based injection therapy that lowers inflammation in RRMS patients by preventing immune cells from entering the brain. Several clinical trials and real-world studies show it to be highly efficacious in treating RRMS, and it is approved in both the U.S. and EU.
“However, several factors may prompt physicians and patients to consider switching to another therapy, most notably the risk of progressive multifocal leukoencephalopathy (PML),” investigators wrote.
PML is a rare brain infection caused by the John Cunningham virus, and it is more likely to affect patients who have a weakened immune system. Long-term treatment (more than two years) with Tysabri has been associated with a higher risk of PML.
Previous studies also report that patients who stop using Tysabri are at a higher risk of experiencing a relapse, particularly in the four to eight months after their last dose.
“Determining the best therapy to switch to and establishing the optimal timing for start of the next therapy” are both crucial factors to consider when switching, the study stated.
To investigate in more detail factors that could increase a relapse risk, researchers analyzed data from the Biogen-sponsored Tysabri Observational Program (TOP; NCT00493298), the largest real-world study of the medication’s effectiveness and safety.
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