PIK3CA and head and neck squamous cell carcinoma: Regarding ATP-competitive PI3K inhibitors, there are several phase-1 and -2 trials enrolling patients with HNSCC to be treated by CTX + Buparlisib (BKM 120) (NCT01816984, phases 1 and 2), Alpelisib (BYL719) (NCT01602315, phases 1b and 2) (126), and Copanlisib (NCT02822482, phases 1b and 2, COPAN-ORL06, specifically for patients harboring a PI3KCA mutation/amplification and/or a PTEN loss).