In Vitro: Spliceostatin A (2.5-20 nM; 0-24 h) induces caspase-dependent apoptosis of CLL cells in a dose- and time-dependent manner. Spliceostatin A (10 nM, 20 nM; 24 h) in combination with ABT-199 or ABT-263 synergises, augments apoptosis in CLL cells following IL4/CD40L (10 ng/mL, 300 ng/mL; 6 h) treatment, and reduce phosphorylation levels of related proteins. Spliceostatin A inhibits the viability of normal B (CD19+) and T (CD3+) lymphocytes with IC50s of 12.1 nM, and 61.7 nM, respectively.