One promising approach to the treatment of cancer is inhibition or modulating the crucial signal transduction pathway of PI3K-Akt-mTOR. Several PI3K inhibitors are being tested in the clinical trials for cancer treatment but not for the head and neck cancer yet. BYL719 is an alpha specific I PI3K inhibitor. It showed significant, concentration dependent cell growth inhibition and induction of apoptosis. We suggest multicenter single arm phase II study to determine anti-tumor effects of BYL719 in patients with recurrent and/or metastatic SCCHN who failed to prior chemotherapy regimens. Enrollment will be done in 5 or more clinical trial centers in Korea. Primary objective is to evaluate disease control rate (DCR) at 8 weeks of BYL719, and the efficacy will be evaluated by the investigators analysis based on RECIST version 1.1.