BKM120 in Esophageal Squamous Cell Carcinoma After Failure of First Line Chemotherapy

Inclusion Criteria: * Patient has provided a signed Informed Consent Form (ICF) obtained prior to any screening procedure. * Age ≥ 18 years old * Histologically confirmed diagnosis of esophageal squamous cell carcinoma and available archival tissue for evaluation of further studies. * Metastatic or unresectable disease * Received one prior chemotherapy or biological therapy regimen for unresectable or metastatic disease * More than 30 days since prior chemotherapy, surgery, radiotherapy, or investigational agents * Measurable disease in at least 1 diameter by CT scan or MRI as per RECIST 1.1 criteria * No evidence of brain metastasis * ECOG ≤ 2 * Patient has adequate bone marrow and organ function * Absolute Neutrophil Count (ANC) ≥ 1.5 x 109/L * Platelets ≥ 100 x 109/L * Hemoglobin ≥ 9.0 g/dL * INR ≤ 2 * Potassium, calcium, magnesium within normal limits for the institution * Serum Creatinine ≤ 1.5 x ULN or Creatinine clearance \> 60 mL * AST and ALT not more than 2.5 times ULN (not more than 5.0 times ULN if there is liver metastasis) * Serum bilirubin within normal range (or ≤ 1.5 x ULN if liver metastases are present; or total bilirubin ≤ 3.0 x ULN with direct bilirubin within normal range in patients with well documented Gilbert Syndrome) * Fasting serum glucose \< 1.5 times ULN Exclusion Criteria: * Patient has received previous treatment with PI3K inhibitors * Patient has symptomatic CNS metastases * Patients with controlled and asymptomatic CNS metastases may participate in this trial. As such, the patient must have completed any prior treatment for CNS metastases \> 28 days (including radiotherapy and/or surgery) prior to enrollment in this study and should not be receiving chronic corticosteroid therapy for the CNS metastases. * Patient has a concurrent malignancy or has a malignancy within 5 years of study enrollment, (with the exception of nonmelanoma skin cancer or cervical carcinoma in situ. * Patient has any of the following mood disorders as judged by the Investigator or a Psychiatrist, or meets the cut-off score of ≥ 10 in the PHQ-9 or a cut-off of ≥ 15 in the GAD-7 mood scale, respectively, or selects a positive response of '1, 2, or 3' to question number 9 regarding potential for suicidal thoughts ideation in the PHQ-9 (independent of the total score of the PHQ-9) * Medically documented history of or active major depressive episode, bipolar disorder (I or II), obsessive-compulsive disorder, schizophrenia, a history of suicidal attempt or ideation, or homicidal ideation (immediate risk of doing harm to others) ≥ CTCAE grade 3 anxiety * Patient is concurrently using other approved or investigational antineoplastic agent * Patient has had major surgery within 28 days prior to starting study drug or has not recovered from major side effects of the surgery * Patient has poorly controlled diabetes mellitus(HbA1c \> 8 %) * Patient has active cardiac disease including any of the following: * LVEF \< 50% * QTc \> 480 msec on screening ECG (using the QTcF formula) * Angina pectoris that requires the use of anti-anginal medication * Ventricular arrhythmias except for benign premature ventricular contractions * Supraventricular and nodal arrythmias requiring a pacemaker or not controlled with medication * Conduction abnormality requiring a pacemaker * Valvular disease with documented compromise in cardiac function * Symptomatic pericarditis * Patient has a history of cardiac dysfunction including any of the following; * Myocardial infarction within the last 6 months, documented by persistent elevated cardiac enzymes or persistent regional wall abnormalities on assessment of LVEF function * History of documented congestive heart failure (New York Heart Association functional classification III-IV) * Documented cardiomyopathy * Patient is currently receiving treatment with QT prolonging medication known to have a risk to induce Torsades de Pointes, and the treatment cannot be discontinued or switched to a different medication prior to starting study drug * Inability to swallow, impaired gastrointestinal (GI) function, or GI disease that would significantly alter the absorption of study drugs or preclude the use of oral medications * Patient has other concurrent severe and/or uncontrolled medical condition that would, in the investigator's judgment contraindicate her participation in the clinical study (e.g.,chronic pancreatitis, active chronic hepatitis etc.) * Patient is currently being treated with drugs known to be moderate and strong inhibitors or inducers of isoenzyme CYP3A, and the treatment cannot be discontinued or switched to a different medication prior to starting study drug.