HDAC9 and melanoma: The ENCORE 601 trial was a phase Ib/II study designed to assess the efficacy of entinostat, a class-I HDAC inhibitor, in combination with pembrolizumab in advanced solid tumors, with phase 2 expansion cohorts in patients with advanced NSCLC and melanoma who have progressed after ICI treatment, and another expansion cohort in mismatch repair-proficient CRC patients.