A Phase 3, Randomized, Placebo-Controlled, Double-Blind, Multicenter Trial of Selinexor in Maintenance Therapy After Systemic Therapy for Patients With p53 Wild-Type, Advanced or Recurrent Endometrial Carcinoma

Inclusion Criteria: Patients must meet all of the following inclusion criteria in order to be eligible to participate in this study:
*  Adults (Aged ≥ 18 years)
*  Histologically confirmed endometrial cancer (endometrioid, serous, undifferentiated, or carcinosarcoma sub-types) that is TP53 wild type by central NGSHistologically confirmed EC including endometrioid, serous, undifferentiated, and carcinosarcoma
*  Must have completed at least 12 weeks of platinum-based chemotherapy (with or without immune checkpoint inhibitors), with a confirmed partial or complete response according to RECIST v1.1
*  Must be able to initiate C1D1 within 3-8 weeks after last platinum dose
*  Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1
*  Adequate bone marrow function and organ function

Exclusion Criteria: Patients meeting any of the following exclusion criteria are not eligible to participate in this study:
*  Uterine sarcomas, clear cell or small cell carcinoma with neuroendocrine differentiation
*  Palliative radiotherapy administered within 14 days of intended C1D1
*  Any gastrointestinal dysfunction that could interfere with the absorption of oral study therapy
*  Serious psychiatric or medical conditions that could interfere with study participation or would make study involvement unreasonably hazardous
*  Previous treatment with an XPO1 inhibitor
*  Stable disease or disease progression after platinum-based chemotherapy
*  Pregnancy, breastfeeding, or other legal/ethical restrictions to trial participation
*  Known dMMR/MSI-H EC tumors that are medically eligible to receive an immune checkpoint inhibitor