Extending the Interval of Natalizumab Dosing: Is Efficacy Preserved?

Marinella Clerico, Stefania Federica De Mercanti, Alessio Signori, Marco Iudicello, Cinzia Cordioli, Elisabetta Signoriello, Giacomo Lus, Simona Bonavita, Luigi Lavorgna, Giorgia Teresa Maniscalco, Erica Curti, Lorena Lorefice, Eleonora Cocco, Viviana Nociti, Massimiliano Mirabella, Damiano Baroncini, Giorgia Mataluni, Doriana Landi, Martina Petruzzo, Roberta LanzilloIlaria Gandoglia, Alice Laroni, Rita Frangiamore, Arianna Sartori, Paola Cavalla, Gianfranco Costantini, Maria Pia Sormani, Ruggero Capra

Research output: Contribution to journalArticlepeer-review


Extending the natalizumab interval after the 24th administration could reduce the risk of progressive multifocal leukoencephalopathy (PML). The objective is to evaluate the noninferiority of the efficacy of an extended interval dosing (EID) compared with the standard interval dosing (SID) of natalizumab. It is an observational, multicenter (14 Italian centers), retrospective cohort study, starting from the 24th natalizumab infusion to the loss of follow-up or 2 years after baseline. Patients were grouped in 2 categories according to the mean number of weeks between doses: < 5 weeks, SID; ≥ 5 weeks, EID. Three hundred and sixty patients were enrolled. Median dose interval (MDI) following 24th infusion was 4.7 weeks, with a bimodal distribution (modes at 4 and 6 weeks). Two hundred and sixteen patients were in the SID group (MDI = 4.3 weeks) and 144 in the EID group (MDI 6.2 weeks). Annualized relapse rate was 0.060 (95% CI = 0.033–0.087) in the SID group and 0.039 (95% CI = 0.017–0.063) in the EID group. The non-inferiority of EID versus SID was satisfied. In conclusion, there is no evidence of a reduced efficacy of natalizumab in an EID setting. This observation confirms previous results and together with the emerging evidence of a reduced risk of PML associated to an EID, supports the need of a randomized study to assess the need to change the standard of the natalizumab dosing schedule.

Original languageEnglish
Publication statusAccepted/In press - Jan 1 2019


  • efficacy
  • extended dose
  • Multiple sclerosis
  • natalizumab
  • progressive multifocal leukoencephalopathy

ASJC Scopus subject areas

  • Pharmacology
  • Clinical Neurology
  • Pharmacology (medical)


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