Copanlisib in Treating Patients With Persistent or Recurrent Endometrial Cancer

Inclusion Criteria: * Patients must have the psychological ability and general health that permits completion of the study requirements and required follow-up * Women of child-bearing potential (WOCBP) must agree to use adequate contraception when sexually active; patients should continue contraception for 6 months after finishing study drug * Submission of tumor tissue is required for all patients; investigators should check with their site pathology department regarding release of biospecimens before approaching patients about participation in the trial * Patients must have recurrent or persistent endometrial cancer (endometrioid adenocarcinoma, serous adenocarcinoma, undifferentiated carcinoma, mixed epithelial carcinoma or adenocarcinoma not otherwise specified \[NOS\]); histologic confirmation of the primary tumor is required * All patients must have a somatic PIK3CA gene mutation (i.e., R88Q in exon 1, N345K in exon 4, C420R in exon 7, E542K, E545X \[E545A, E545D, E545G, and E545K\], Q546X \[Q546E, Q546K, Q546L, and Q546R\] in exon 9, and M1043I, H1047X \[H1047L, H1047R, and H1047Y\], or G1049R in exon 20) in a representative primary or metastatic tumor sample confirmed by the Roche COBAS PIK3CA Mutation Test at Q\^2 Solutions * All patients must have measurable disease as defined by Response Evaluation Criteria in Solid Tumors (RECIST) 1.1; measurable disease is defined as at least one lesion that can be accurately measured in at least one dimension (longest diameter …