HDAC6-IN-19 (Compound 14g) is a HDAC6 inhibitor ( IC 50 : 2.68 nM). HDAC6-IN-19 also inhibits HDAC1 , HDAC2 and HDAC3 with IC 50 s of 61.6 nM, 98.7 nM and 103 nM. HDAC6-IN-19 potently inhibits multiple cancer cell proliferation, including leukemia, colon cancer , melanoma, and breast cancer cell lines.