P5091 treatment effectively induces apoptosis in both TP53-mutated MEC-1 and TP53-wild-type EHEB cell lines and, remarkably, is highly effective in del17p CLL primary CD19+ lymphocytes, with an apoptotic induction ‘potency’ like the one observed in TP53-wild type CLL samples. The gene discussed is CD19; the disease is B-cell chronic lymphocytic leukemia.