Targeted Therapy for Recurrent Endometrial Cancer

Key Inclusion Criteria: * Recurrent or persistent endometrial carcinoma which has progressed or recurred after at least 1, but no more than 2, prior lines of therapy. Prior hormonal therapies (e.g., tamoxifen, aromatase inhibitors) will not count toward the prior regimen limit. Chemotherapy given in conjunction with radiotherapy as a radiosensitizer will be counted as a systemic therapeutic regimen. * Measurable disease per RECIST 1.1 * Availability of a representative tumor specimen that is suitable for determination of biomarker status via central testing (F1CDx) OR If a patient has a prior F1CDx report from 1 September 2019 or later, those NGS results can be used to determine biomarker status as long as the tumor tissue used in the report was obtained within 5 years prior to prescreening and appropriate signed consent is obtained from the patient. * Life expectancy \> 12 weeks * Recovery from effects of recent radiotherapy, surgery, or chemotherapy Key Exclusion Criteria: * Endometrial tumors with the following histologies: squamous carcinomas, sarcomas * Other invasive malignancies within the last 5 years, except for non-melanoma skin cancer with no evidence of disease within the past 5 years AND localized breast cancer with previous adjuvant chemotherapy treatment for breast cancer completed \> 5 years ago * Synchronous primary invasive ovarian or cervical cancer * Have an active or history of autoimmune disease or immune deficiency * Have a history of idiopathic pulmonary fibrosis, organizing pneumonia, drug-induced pneumonitis, idiopathic pneumonitis, or evidence of active pneumonitis based on a screening chest computed tomography (CT) scan * Active tuberculosis * Severe infections within 4 weeks * Have received therapeutic oral or IV antibiotic medication within 2 weeks, except prophylactic antibiotic medication * Have significant cardiovascular disease * Are administered treatment with a live attenuated vaccine within 4 weeks, or anticipation of need for such a vaccine during the course of the study * Have prior allogeneic bone marrow transplantation or solid organ transplant * History of treatment with systemic immunostimulatory agents (including but not limited to interferons, interleukin-2) within 4 weeks or 5 half-lives of the drug, whichever is longer, prior to initiation of study treatment * History of treatment with systemic immunosuppressive medications within 2 weeks except acute, low-dose, systemic immunosuppressant medications, corticosteroids for chronic obstructive pulmonary disease and asthma, or mineralocorticoids and low-dose corticosteroids for participants with orthostatic hypotension or adrenocortical insufficiency * Have a history or clinical evidence of any untreated CNS disease, seizures not controlled with standard medical therapy, or history of cerebrovascular accident (stroke), transient ischemic attack or subarachnoid hemorrhage within 6 months AFT-50A Specific Exclusion Criteria: ● Prior treatment with T-cell costimulating or immune checkpoint blockade therapies including, but not limited to, CD137 agonists, anti-PD-1, anti-PD-L1, and anti-CTLA-4 therapeutic antibodies Note: Additional study cohort specific inclusion and exclusion criteria may apply based on cohort assignment.