BTK and B-cell chronic lymphocytic leukemia: If TP-0903 were to be added to CLL patients still on ibrutinib therapy this may be of additional clinical benefit in that we showed earlier that combined treatment of TP-0903 with ibrutinib or a reversible BTK inhibitor, TP-4216 (Tolero Pharmaceuticals) of CLL B-cells from previously untreated CLL patients augmented leukemic B-cell apoptosis than with each agent alone [16].