Benefits of long-term Tysabri seen in RRMS patients in Japan: Study

Tysabri (natalizumab) significantly reduced the development of brain lesions on MRI scans in Japanese people with relapsing-remitting multiple sclerosis (RRMS), according to a new study.

The therapy also eased or stabilized disability levels in most patients after five years of treatment, and significantly reduced the annual rate of relapse from the first year onward.

“Given the rarity of MS in Japan, and the scarcity of data in treated patients for an extended period, our results, nevertheless, provide some insight into active lesion development and patient disability over the long-term,” researchers wrote.

The study, “Long-term effects of natalizumab on MRI activity and clinical outcomes in Japanese patients with relapsing-remitting multiple sclerosis,” was published in the journal BMC Neurology.

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Tysabri designed to prevent immune cells from entering brain, spinal cord

Tysabri is an approved multiple sclerosis (MS) treatment that works to prevent the movement of immune cells from circulation into the brain and spinal cord, therefore reducing the excess inflammation that drives the neurodegenerative disease.

By doing so, the treatment can be used to reduce relapses, decrease MRI disease activity, and slow disability progression in people living with MS. In the U.S., Tysabri is approved to treat relapsing forms of the disease, but in Japan, Europe, and several other countries, it is indicated only for people with active RRMS.

It is well established that Asian people may respond differently to some disease-modifying therapies. Although Tysabri has been deemed safe and effective in Japanese people with MS enrolled in a Phase 2 clinical trial (NCT01440101), that study followed patients for only six months, and neither the study nor its open-label extension (NCT01416155) used MRI scans to assess disease activity and progression.

Therefore, “more real-world data, including evidence from the start of its approval in Japan in the early 2010s, is needed,” the researchers wrote.

To investigate the long-term impact of Tysabri in Japanese people with RRMS, researchers retrospectively examined data from 85 patients followed at a single center in Osaka. The patients had received the therapy for at least one year and had available MRI data before and after initiating treatment.

Most patients were women (76.5%), were a mean of 37.5 years when they started on Tysabri, and had been living with the disease for a mean of 8.7 years.

Among the 85 patients, 29 had participated in the Phase 2 trial and its open-label extension, with a median duration of Tysabri treatment of 2.3 years. The remaining 56 participants had started Tysabri after its launch in the country and received the treatment for about 1.9 years.

In total, 58 patients stopped Tysabri, 43 of whom did so in the first two years. The main reason for stopping were concerns about progressive multifocal leukoencephalopathy, a severe opportunistic infection of the brain that’s a known side effect of Tysabri.

Results showed that the number of new or enlarging lesions was significantly reduced after Tysabri initiation. In the year before treatment, 52.9% of patients had developed new or enlarging lesions, but that percentage dropped to 2.4% between six and 18 months after starting the treatment and 1.6% between 18 and 30 months.

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No patients developed new lesions in remaining period up to 5.5 years

Although only a small number of patients were followed for more than 2.5 years, none of them developed new lesions in the remaining period up to 5.5 years.

Disability scores, as measured with the Expanded Disability Status Scale, also remained stable during the treatment for 61.8% of the patients, whereas 26.3% experienced improvements, and 11.8% had disability worsening in their last evaluation compared with before treatment.

Relapse rates decreased significantly with treatment, from about 1.12 relapses per year before Tysabri, to 0.12 in the first year, and 0.15 relapses per year in year 5. Similarly, the proportion of patients experiencing no relapses, no disability progression, and no new lesions increased from 67.1% in the first year on Tysabri to 86.7% in the third year.

“While this study provides the first long-term (5 years) MRI data in RRMS patients in Japan receiving [Tysabri], firm conclusions regarding its effectiveness beyond 2-3 years were limited by small patient numbers,” the researchers concluded.

Of note, the research was “conducted from a medical perspective based on a joint research agreement with Biogen Japan.” Biogen is the company that markets Tysabri.