The study, “High-Risk PML Patients Switching from Natalizumab to Alemtuzumab: an Observational Study,” appeared in the journal Neurology and Therapy.
Tysabri, an antibody with anti-inflammatory action, is co-marketed by Biogen and Élan. Its exact mechanism of action is not yet fully understood, but previous studies have supported its approval based on its ability to reduce the relapse rate in MS.
However, Tysabri has also been shown to increase the risk of a rare opportunistic viral infection of the brain called progressive multifocal leukoencephalopathy (PML). Alternative therapies for these patients are therefore needed.
Lemtrada, an antibody therapy, specifically targets the CD52 protein, which is present on the surface of certain immune cells, such as T- and B-cells, thereby blocking their action. The drug, developed by Sanofi Genzyme, received approval in December 2014 by the U.S. Food and Drug Administration to treat RRMS. It is given as intravenous infusions for five consecutive days initially, and for three consecutive days one year later.
The Italian study aimed to investigate whether MS patients stopping their treatment with Tysabri could safely switch to Lemtrada.
Researchers at the University Hospital San Luigi Gonzaga of Orbassano followed 16 patients who had received a median of 20 Tysabri infusions before quitting the treatment due to an increased risk of PML. The switch to Lemtrada occurred after a median wash-out period of 70 days.
All patients underwent brain MRI every three months while on Tysabri and shortly after starting Lemtrada treatment, to check for signs of PML. They received new MRIs six and 12 months after starting Lemtrada.
The study is still ongoing, but so far, according to researchers, those who have received Lemtrada for at least six months or for one year showed no sign of disease activity or new lesions. Furthermore, they have neither relapsed nor worsened on the Expanded Disability Status Scale — a measure that quantifies disability in patients with MS.
Although this study includes only a small number of patients, researchers concluded that the study’s “initial data are very promising as no patient had radiological signs or clinical symptoms of disease reactivation/progression, no patient experienced severe side effects and no patient developed PML.”
The team added: “Obviously, patients must be well-informed about risks and advantages derived from interrupting [Tysabri] and switching to [Lemtrada], and the decision to stop [Tysabri] and start [Lemtrada] must be completely shared between the patient and neurologist.”