HDAC9 and head and neck squamous cell carcinoma: Consistent with our knowledge on the actionable pathways/gene alterations in HNSCC, targeted cancer compounds inhibiting the PI3K/AKT/MTOR (n = 44), EGFR (n = 28) and HDAC (n = 20) were found among the MOAs with the largest number of active compounds making up 10.5%, 7.5% and 4.8% of all active targeted compounds, respectively [Fig. 1C].