Dacinostat (also known as LAQ824), is a hydroxamate histone deacetylase inhibitor with potential anticancer activity. Dacinostat inhibits histone deacetylase enzymatic activities in vitro and transcriptionally activated the p21 promoter in reporter gene assays. Tumor cells treated with Dacinostat caused acetylation of HSP90 and degradation of its cargo oncoproteins. Flow cytometry studies revealed that both tumor cell lines and normal diploid fibroblasts arrested in the G2/M phase of the cell cycle after Dacinostat treatment. However, an increased sub-G1 population at 48 h (reminiscent of apoptotic cells) was only observed in the cancer cell lines treated with Dacinostat. Dacinostat exhibited antitumor effects in a xenograft animal models. In phase I trials, Dacinostat was well tolerated at doses that induced accumulation of histone acetylation, with higher doses inducing changes consistent with HSP90 inhibition. In another phase 1 in patients with advanced solid tumors, grade 3 or 4 toxicities were observed. Dacinostat had been in phase II clinical trials by Novartis for the treatment of solid tumors but further studies were discontinued.