KD5170, a novel mercaptoketone-based histone deacetylase inhibitor that exhibits broad spectrum antitumor activity in vitro and in vivo

Abstract

Histone deacetylase (HDAC) inhibitors have garnered significant attention as cancer drugs. These therapeutic agents have recently been clinically validated with the market approval of vorinostat (SAHA, Zolinza) for treatment of cutaneous T-cell lymphoma. Like vorinostat, most of the small-molecule HDAC inhibitors in clinical development are hydroxamic acids, whose inhibitory activity stems from their ability to coordinate the catalytic Zn2+ in the active site of HDACs. We sought to identify novel, nonhydroxamate-based HDAC inhibitors with potentially distinct pharmaceutical properties via an ultra-high throughput small molecule biochemical screen against the HDAC activity in a HeLa cell nuclear extract. An alpha-mercaptoketone series was identified and chemically optimized. The lead compound, KD5170, exhibits HDAC inhibitory activity with an IC50 of 0.045 micromol/L in the screening biochemical assay and an EC50 of 0.025 micromol/L in HeLa cell-based assays that monitor histone H3 acetylation. KD5170 also exhibits broad spectrum classes I and II HDAC inhibition in assays using purified recombinant human isoforms. KD5170 shows significant antiproliferative activity against a variety of human tumor cell lines, including the NCI-60 panel. Significant tumor growth inhibition was observed after p.o. dosing in human HCT-116 (colorectal cancer), NCI-H460 (non-small cell lung carcinoma), and PC-3 (prostate cancer) s.c. xenografts in nude mice. In addition, a significant increase in antitumor activity and time to end-point occurred when KD5170 was combined with docetaxel in xenografts of the PC-3 prostate cancer cell line. The biological and pharmaceutical profile of KD5170 supports its continued preclinical and clinical development as a broad spectrum anticancer agent.

Sonic Hedgehog-Induced Histone Deacetylase Activation Is Required for Cerebellar Granule Precursor Hyperplasia in Medulloblastoma

“…HDAC5 and HDAC11 did not reveal any difference and the activities of other members were not in the detectable range. Comparison of the half maximal effective concentration (EC50) against the HDAC inhibitor, Trichostatin A (TSA) that exhibits more potency toward class I family HDACs (HDAC1, 2, 3) than class IIa (HDAC4, 5) [17], [18] revealed an EC50 of 16.44 nM in tumors and of 31.11 nM in wild-type cerebellum (Fig. S2) suggesting that HDAC1 and 2 might be the predominant contributors to the increased HDAC activity observed in Smo/Smo tumors.…”

Histone deacetylase inhibitors in multiple myeloma

“…KD5170 showed significant anti-proliferative activity against a variety of human tumor cell lines, including human MM cell lines. 44 …”

Histone Deacetylase Inhibitors

“…Related mercaptoketones were developed by the group at Kalypsys [94]. This group sought nonhydroxamate HDACis, and after a uHTS screen of 600 000 compounds, they identified disulfide 82 as a hit, IC 50 ¼ 135 nM.…”