TP53 and B-cell chronic lymphocytic leukemia: Therefore, in order to start to elucidate the factors governing sensitivity/resistance to Ibrutinib, we sought to analyze: i) the clonal evolution of TP53 mutations in a pilot group of B-CLL patients undergoing Ibrutinib therapy in a 12 months follow-up; ii) the potential anti-leukemic activity of the combination of Ibrutinib with γ-secretase inhibitors (GSI) by in vitro assays performed using B-CLL primary cells.