Extending the dosing periods of Tysabri (natalizumab) treatment may help reduce the risk of progressive multifocal leukoencephalopathy, or PML, in multiple sclerosis (MS) patients infected with the JC virus, a study suggests.
The study, “Natalizumab Extended Interval Dosing Is Associated with a Reduction in Progressive Multifocal Leukoencephalopathy Risk in the Touch Registry,” was recently presented at the third annual Americas Committee for Treatment and Research in Multiple Sclerosis (ACTRIMS) Forum 2018, held Feb. 1-3 at the Hilton San Diego Bayfront in San Diego, California.
Tysabri — an approved therapy for relapsing forms of MS marketed by Biogen — administered as a 300 mg intravenous dose every four weeks is known to be linked to a higher risk of PML, a rare viral infection in the brain caused by the John Cunningham (JC) virus.
Extending the dosing intervals between Tysabri treatments is sometimes practiced, especially in patients at high risk of developing PML, but the outcome of this strategy in terms of PML risk remains inconclusive.
In this study, researchers used a U.S. risk evaluation and mitigation program called TOUCH Prescribing Program to assess whether extending the interval of Tysabri dosing could be associated with a reduced PML risk compared with the standard four-week interval. The TOUCH program had data from 90,038 MS patientsas of June 1, 2017.
The team analyzed data from patients who tested positive for anti–JC virus antibodies, and defined three different standard and extended dosage intervals: from three to five weeks for standard treatment, and from five to 12 weeks for extended interval dosing. Patients with dosing intervals of more than 12 weeks or less than three weeks were excluded.
The average dosing interval was 29 days for standard treatment and 36 days for the extended interval program, with a median exposure of 44 and 59 months, respectively. The majority of patients followed a standard program for more than two years before undergoing the extended interval dosing program.
The results showed that the extended dosing program was associated with a significant reduction in the risk of developing PML, compared with the standard regimen in anti-JCV-antibody-positive patients.
However, whether Tysabri maintained the same effectiveness as in the standard regimen was not evaluated, because the TOUCH program does not collect effectiveness data.
As such, “additional studies are needed to establish whether the effectiveness of natalizumab is maintained with EID [extended interval dosing],” the team concluded.