Alemtuzumab (Lemtrada®) is a humanized monoclonal antibody actually approved by European Medicines Agency (EMA) for the treatment of adults with highly active relapsing remitting multiple sclerosis (RRMS). It targets and depletes cells with CD52 surface antigen (lymphocytes, monocytes, macrophages, eosinophils and NK cells) (Dubey et al., 2015; Hale, 2001). Depletion of circulating T and B cells is followed by a distinct pattern of T and B cells repopulation (Cox et al., 2005).

In CAMMS223 phase II trial (Coles et al., 2008) and in CARE-MS I and CARE-MS II phase III trials (Cohen et al., 2012; Coles et al., 2012) alemtuzumab has demonstrated to be more efficacious than interferon beta 1a 44 µg on clinical and MRI outcomes. Durability of effect is proved in CAMMS223 extension and TOPAZ studies (Steingo et al., 2020; Ziemssen et al., 2020). Common adverse events associated with alemtuzumab in clinical trials are infusion-associated reactions, infections, and secondary autoimmunity (thyroid disorders, immune thrombocytopenia, nephropathies). In November 2019, EMA modified label indication of alemtuzumab due to postmarketing reports concerning rare but serious effects, including deaths, from immune-mediated conditions and serious heart, circulation and bleeding disorders, including stroke. Immune-mediated conditions can occur many months after treatment while serious disorders of the heart, circulation and bleeding may develop within days of receiving alemtuzumab.

Although alemtuzumab was approved by EMA in 2013 and by the U.S. Food and Drug Administration (FDA) in 2014, information about its use in real clinical practice is limited and based mainly on retrospective studies with small cohorts (Prosperini et al., 2018; Frau et al., 2019; Hyun et al., 2019; di Ioia et al., 2020; Bose et al., 2021; Herman et al., 2021; Zmira et al., 2021; Theodorsdottir et al., 2021; Russo et al., 2022). The objective of this study was to evaluate alemtuzumab effectiveness and safety in a real-world setting.