Avelumab and M1774 in ARID1A-mutated Endometrial Cancer

Participants must have endometrial cancer that is ARID1A-mutated [loss of function (LOF) mutations] determined by any CLIA-certified next-generation sequencing assay. ARID1A LOF mutation status must be confirmed by the principal investigator prior to participant enrollment.

Participants must have measurable disease per RECIST 1.1, defined as at least one lesion that can be accurately measured in at least one dimension (longest diameter to be recorded for non-nodal lesions and short axis for nodal lesions). Each lesion must be >= 10 mm when measured by CT, MRI or caliper measurement by clinical exam; or >= 20 mm when measured by chest x-ray. Lymph nodes must be > 15 mm in short axis when measured by CT or MRI.

Prior Therapy: There is no upper limit of prior therapies, but patients must have had one prior chemotherapeutic regimen for management of endometrial carcinoma. Initial treatment may include chemotherapy, chemotherapy and radiation therapy, and/or consolidation/maintenance therapy. Furthermore, patients who have only received chemotherapy with immunotherapy in the adjuvant setting will be eligible for the study.

Participants must have received prior immunotherapy targeting the PD-1/PD-L1 pathway either in the adjuvant, first-line or recurrent setting. Up to 50% of participants (i.e. a maximum of 12 participants) who do not meet this requirement may enroll in the study.