Off-label treatment with Tysabri (natalizumab) significantly lessens disease activity and reduces the number of relapses per year in patients with pediatric-onset multiple sclerosis (POMS), real-world data from Portugal show.
The treatment also was considered safe in this population, in agreement with earlier studies.
These findings support the usefulness of Tysabri for treating MS patients who develop the disease during childhood, the researchers said.
Titled “TyPed study: Natalizumab for the treatment of pediatric-onset multiple sclerosis in Portugal,” the study was published in the journal Multiple Sclerosis and Related Disorders.
Patients with POMS — which comprises about 5% of all MS cases — experience significant brain inflammation, and develop early onset physical and cognitive disability, which has a negative impact on these individuals’ overall quality of life.
The standard approach for treating these patients usually consists of first-line treatment with disease-modifying therapies (DMT) such as interferon beta (sold as Avonex, among others) and glatiramer acetate (sold as Copaxone and others). However, around one-third of patients respond poorly to such therapies and require second-line DMTs.
Biogen‘s Tysabri is a second-line DMT approved for adults with MS, in whom it proved effective at preventing cognitive decline.
The therapy also has shown the ability to reduce disease activity in POMS patients, including those with more severe disease.
Few clinical trials have studied Tysabri in childhood MS, however. Therefore, according to the researchers, there is a need to continue collecting real-world data on the safety and efficacy of this treatment in POMS patients.
Now, researchers at the University of Coimbra, in Portugal, reported the outcomes of all POMS patients who received Tysabri in their country from 2007 to 2018. Of note, the treatment was introduced in Portugal for adults in 2007.
A total of 21 children and adolescents were included, of whom 14 (67%) were girls. Their median age at diagnosis was 13, and three patients were diagnosed before age 10.
The patients received Tysabri for a median of 27 months, or two years and three months. Before starting the treatment, more than half (57.1%) had been treated with at least one DMT. The most prescribed was interferon-beta.
Among the 13 patients who received Tysabri for at least one year and had available disease activity information, none experienced a worsening in disability — as measured with the Expanded Disability Status Scale score (EDSS), in which higher scores indicate greater disability.
In these patients, EDSS scores at baseline, or the study’s start, were 1.50, on average, and significantly dropped to 1.00 after two years of treatment.
The number of relapses per year also decreased, dropping from 1.31 events per patient each year to zero events after one year, and 0.04 after two years. Overall, the mean time to relapse was 35.8 months, or just less than three years.
MRI scans were available for eight patients who completed one year of treatment, and five patients who received two years of Tysabri. None of these patients showed new lesions or signs of inflammation in the brain after one year. One had new lesions or inflammatory lesions in the brain at two years.
No Evidence of Disease Activity (NEDA)-3 — defined as no EDSS progression, no relapses, and no new lesions — also was observed in all patients after one year of treatment and in 75% of them after two years.
Regarding safety, the researchers reported a total of 13 adverse events (side effects) experienced by six patients. Eight of those adverse events were possibly related to Tysabri. One patient experienced a serious adverse event, specifically pneumonia, that required treatment for one month but no adjustment in Tysabri dosing.
Five patients discontinued Tysabri after lab tests showed antibodies against the John Cunningham virus (JVC). Tysabri has been linked with an increased risk of progressive multifocal leukoencephalopathy (PML), a severe opportunistic infection of the brain caused by JVC.
Overall, these results suggest that Tysabri “may be an effective and safe disease-modifying therapy for POMS,” the researchers wrote.
“Our results are in line with data published for the adult population, as well as with similar observational studies in pediatric populations in other regions,” the investigators concluded.
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