Selinexor in Treating Participants with Advanced Thymic Epithelial Tumor

Inclusion Criteria

• Histologically confirmed advanced TET (thymoma)
• Progression after primary chemotherapy
• No more than two previous lines (neoadjuvant or chemoradiotherapy will count as one line if disease progression has occurred within 6 months)
• Inoperable per local Investigator (Masaoka stage III or IV)
• Progression after treatment with least one platinum containing chemotherapy regimen
• Measurable disease (RECIST 1.1)
• Eastern Cooperative Oncology Group (ECOG) performance status (PS) =< 2
• Patients must have recovered from the toxic effects of prior therapy at the time of initiation of the study drug unless toxicity is stable
• A 4 weeks or five half-lives interval from any investigational agents or cytotoxic chemotherapy to start of study is required (whichever is shorter)
• Signed informed consent
• Total white blood cell count (WBC) >= 3000/mm^3
• Absolute neutrophil count (ANC) >= 1500/mm^3
• Platelet count >= 100,000/mm^2
• Hemoglobin >= 9.0 gm/dL
• Bilirubin < 1.5 times the upper limit of normal (ULN)
• Alanine aminotransferase (ALT) < 2.5 times upper limit of normal (ULN) or ALT < 5.0 times ULN in the presence of liver metastases
• Creatinine clearance > 30 ml/min according to Cockcroft-Gault
• Patients of childbearing potential must agree to use adequate birth control during and for 3 months after participation in this study

Exclusion Criteria

• No significant medical illness that in the investigator’s opinion cannot be adequately controlled with appropriate therapy or would compromise the patient’s ability to tolerate this therapy, including * Unstable cardiovascular function * Known active hepatitis A, B, or C infection; or known to be positive for hepatitis C virus (HCV) ribonucleic acid (RNA) or hepatitis B surface antigen (HBsAg) (hepatitis B virus [HBV] surface antigen) * Markedly decreased visual acuity * Active infection requiring intravenous antibiotics
• Pregnancy or breast-feeding
• Symptomatic brain metastasis requiring corticosteroids
• Uncontrolled autoimmune disorders. Patients with autoimmune disorders under control on medication may be included. Patients with pure red cell aplasia may be included if hemoglobin levels are relatively stable on transfusions or medication
• Significantly diseased or obstructed gastrointestinal tract, malabsorption, uncontrolled vomiting or diarrhea or inability to swallow oral medications
• No dehydration of National Cancer Institute (NCI)-Common Terminology Criteria for Adverse Events (CTCAE) grade >= 1
• Serious psychiatric or medical conditions that could interfere with treatment
• No history of organ allograft
• No concurrent therapy with approved or investigational anticancer therapeutics