The three most active HDAC6i (SW-117, SW-101, WT-36-87), plus SW-113 that showed negligible activity as a single agent, were tested in combination with the PI3Kα/δ inhibitor copanlisib and the BCL2 inhibitor venetoclax, in DOHH2 and SU-DHL-4. All four HDAC6i showed enhanced anti-proliferative activity in at least one of the combinations tested.