Study of Navtemadlin as Maintenance Therapy in TP53WT Advanced or Recurrent Endometrial Cancer

Inclusion Criteria: * ECOG 0-1 * Histologically or cytologically confirmed diagnosis of endometrial cancer documented as TP53WT * Subjects with advanced or recurrent disease must have completed a single line of up to 6 cycles of taxane-platinum based chemo and achieved a CR or PR per RECIST V1.1 * Adequate hematologic, hepatic and renal function (within 14 days) Exclusion Criteria: * Has any sarcomas or small-cell carcinomas with neuroendocrine differentiation * Prior immune therapy, cytokine therapy, or any investigational therapy (within 28 days) * Indwelling surgical drains * Grade 2 or higher QTc prolongation * History of major organ transplant * History of bleeding diathesis; major hemorrhage or intracranial hemorrhage (within 24 weeks)