HDAC9 and head and neck squamous cell carcinoma: Regarding HDAC inhibitors, a trial investigating romidepsin (NCT00084682) as monotherapy in the R/M HNSCC did not show clinical efficacy and tolerability was limiting; however, the expected pharmacodynamic effects with increased H3 hyperacetylation in PBMCs were observed, suggesting that other HDAC inhibitors with a better tolerability profile could be investigated in combination regimens in this patient population.