4-iodo-SAHA is a hydrophobic derivative of the class I and class II histone deacetylase (HDAC) inhibitor SAHA. At 1 μM it demonstrates >60% inhibition of HDAC1 and HDAC6 activity in a deacetylase activity assay, similar to that of SAHA. 4-iodo-SAHA inhibits proliferation of SK-BR-3 breast-derived and HT29 colon-derived cell lines with EC50 values comparable to that of SAHA (1.1 and 0.95 μM versus 2.1 and 2 μM, respectively). It is 10-fold more potent as an inhibitor of U937 leukemia cell proliferation compared to SAHA (0.12 μM versus 1.2 μM, respectively).
