HDAC6-IN-67 is a selective HDAC6 inhibitor with an IC50 of 17.15 nM, demonstrating 19-fold selectivity over HDAC1. It selectively inhibits HDAC6 by interacting with Ser531 and His614. HDAC6-IN-67 induces apoptosis by cleaving caspase9, 8, 3 and PARP, upregulating Bax expression, and downregulating Bcl-2 expression. It effectively acetylates α-tubulin in MCF-7/ADR cells without affecting histone H3 acetylation. HDAC6-IN-67 is applicable in breast cancer research.

HDAC6-IN-67 exhibits a significant time-dependent inhibitory effect on tumor cells across all tested human cancer cell lines, with GI 50 values ranging from 2.9 to 24.8 μM. It strongly inhibits proliferation in MCF-7/ADR cells after 72 hours (GI 50 = 2.4 μM). At concentrations of 0.01-2 μM over 24 hours, HDAC6-IN-67 increases acetylation of α-tubulin in MCF-7/ADR cells in a dose-dependent manner without affecting the acetylation of histone H3. Additionally, HDAC6-IN-67 (0.1-2 μM over 10 days) significantly and dose-dependently inhibits colony formation in MCF-7/ADR cells. It induces both early and late apoptosis and dose-dependently triggers the cleavage of Caspase 9, Caspase 8, Caspase 3, and PARP. Moreover, HDAC6-IN-67 significantly upregulates the expression of pro-apoptotic protein Bax and downregulates the expression of anti-apoptotic protein Bcl-2 in MCF-7/ADR cells.

HDAC6-IN-67 administered at doses of 5 mg/kg and 10 mg/kg via intraperitoneal injection once daily on weekdays for 17 days inhibits the growth of HCT116 tumors in mice in a dose-dependent manner, without significant toxicity.