Natalizumab in aggressive multiple sclerosis after haematopoietic stem cell transplantation.

High-dose cyclophosphamide followed by autologous haematopoietic stem cell transplantation (HDC-AHSCT) is a treatment option for aggressive and refractory multiple sclerosis (MS). Natalizumab is a monoclonal antibody approved for relapsing-remitting (RR) MS unresponsive to immunomodulating drugs. Nothing is known about the use of natalizumab in patients after HDC-AHSCT. We describe five female RR-MS patients with incomplete response to HDC-AHSCT. Natalizumab was then administered with abolition of both MRI and clinical activity. No severe adverse events, in particular opportunistic infections such as Progressive Multifocal Leukoencephalopathy (PML), were observed. Our results suggest that the use of natalizumab in aggressive RR-MS after HDC-AHSCT could be effective and safe. The very long-term risk of adverse events due to sequential aggressive immunosuppression has to be established.