The study, “Safety and Efficacy of Natalizumab in Japanese Patients with Relapsing-Remitting Multiple Sclerosis: Open-Label Extension Study of a Phase 2 Trial,” appeared in the journal Neurology and Therapy.
In non-Asian populations, it has been reported that Tysabri-treated RRMS patients experience continued reductions in annualized relapse rate (ARR) after four to five years of follow-up.
Among Asian Japanese patients, a 24-week study NCT01440101) demonstrated that Tysabri reduces AAR and increases the ratio of relapse-free patients (24 percent) compared to placebo (38 percent). After this study, researchers continued to follow Japanese RRMS patients for two years to evaluate Tysabri’s long-term efficacy and safety.
Researchers initially selected 97 Japanese patients aged 18–65 years for the short-term study. Of the total, 54 received 300 mg Tysabri intravenously while 43 got a placebo. In the two-year extension study (NCT01416155), all patients received Tysabri, which is co-marketed by Biogen and Élan.
The team found that after two years of Tysabri treatment, ARR remained lower in patients treated with the drug (0.13) than those who had been on placebo (0.30). The percentage of relapse-free patients was also higher (55 percent) in previously Tysabri-treated patients than among the placebo group (43 percent).
Researchers found no major differences regarding safety and tolerability between patients who were always treated with Tysabri and those who first received placebo and then started Tysabri treatment. MS relapse and nasopharyngitis were the most frequently reported events in both groups.
Nor did they find differences between groups in the percentage of patients who had viral anti-JCV antibodies. Although the risk of developing progressive multifocal leukoencephalopathy (PML) — a viral brain infection that has been associated with Tysabri treatment — is higher in patients who test positive for anti-JCV antibodies, no cases of PML were reported during this long-term study.
“The efficacy and safety findings from the double-blind bridging study and the open-label extension study are comparable to and confirm results reported from other clinical trials of natalizumab [Tysabri] conducted in non-Asian patient populations, and provide longer-term evidence of the efficacy and safety of natalizumab treatment in Japanese patients with RRMS,” authors wrote.