#AAN2018 – Extending Time Between Tysabri Doses Linked to Lower PML Risk, Analysis Suggests

Patricia Inacio, PhD avatar

by Patricia Inacio, PhD |

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Extending the time between standard doses of Tysabri (natalizumab) from four weeks to up to 12 weeks is linked to a significant decrease in the risk of progressive multifocal leukoencephalopathy (PML) in multiple sclerosis (MS) patients infected with what’s known as the JC virus, according to a recent analysis of data from the TOUCH Prescribing Program.

The results were recently presented at the 2018 Annual Meeting of the American Academy of Neurology in an emerging science poster presentation titled, “Natalizumab extended interval dosing (EID) is associated with a significant reduction in progressive multifocal leukoencephalopathy (PML) risk compared with standard interval dosing (SID) in the TOUCH® Prescribing Program.

Tysabri, marketed by Biogen, was shown to reduce clinical relapses and the formation of new brain/spinal cord lesions,  leading to its approval for relapsing forms of MS. The therapy is typically administered as a 300 mg intravenous dose every four weeks.

However, safety concerns have been raised after studies linked Tysabri administration with a higher risk of PML, a rare but potentially fatal infection in the brain caused by the John Cunningham (JC) virus.

Researchers investigated whether extending the interval between doses of the therapy would maintain the efficacy of Tysabri while reducing the risk of PML. They defined the extended interval dosing range as three-plus weeks to 12 weeks.

Researchers used data from the U.S. risk evaluation and mitigation program – the TOUCH Prescribing Program – which gathers data about the risk of PML associated with Tysabri treatment. All patients recruited for this analysis were positive for antibodies against the JC virus, meaning that they had been infected.

The first stage of the analysis included 13,132 patients receiving the standard interval dosing and 1,988 patients receiving the extended interval dosing in the last 18 months of patient’s treatment.

In a second step of the analysis, involving 15,424 patients receiving the standard and 3,331 patients receiving the extended interval dosing, researchers identified any period of extended interval dosing throughout patients’ treatment history with Tysabri.

The first analysis showed that the average dosing interval was 30 days for the standard interval dosing and 37 days for the extended interval dosing. The overall median exposure to Tysabri was 44 months (3.7 years) and 59 months (4.9 years) for standard and extended interval dosing periods, respectively.

The results from the first and second analysis showed that extending Tysabri’s interval dosing reduced the patients’ risk for PML.

Overall, these results suggest that in MS patients positive for antibodies against the JC virus, extending the dosing interval for Tysabri “is associated with a clinically and statistically significant reduction in PML risk as compared with SID [standard interval dosing],” researchers wrote.

Nonetheless, “as TOUCH does not collect effectiveness data, further studies are needed,” the team added.

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