Pilot Study of Tocilizumab in Patients With Erdheim-Chester Disease

The study we propose is a pilot phase II, interventional, treatment, open-label, single-arm, efficacy/safety clinical trial of a 6-month treatment with tocilizumab (8 mg/kg once monthly) in adult patients with extraskeletal Erdheim-Chester disease (ECD). Efficacy will be assessed as the effect of the treatment on the size of the measurable lesions, as evaluated by bidimensional measurements, and by the impact of the treatment on symptom control and on patient quality of life. Safety of the treatment will be determined by the analysis of adverse events and of the relevant safety laboratory parameters. Secondary objectives of the study will be: 1. to better characterize the mechanisms underlying such disease and the possible response to the treatment. In particular: i) we will investigate the immunophenotypic and histomorphologic features of ECD histiocytes; ii) we will gather gene expression data from peripheral blood immune cells to better characterize their functional status, to define their transcriptional fingerprints and their possible modulation as a result of tocilizumab treatment; iii) we will assess the production of soluble mediators and the expression of activation molecules by monocytes derived from ECD patients, as well as after stimulation with selected inflammatory cytokines; iv) we will investigate the ex vivo and in vitro impact of tocilizumab treatment on those markers, for possible use as a predictor or indicator of response to treatment. 2. to investigate the metabolic pattern in ECD patients before and after tocilizumab treatment as evaluated by fluoro-d-glucose positron emission tomography (FDG-PET) and to verify if it can be an indicator of ECD activity.