ESR1 and breast cancer: While no trials are currently underway that are investigating further combination in solely OC, a phase II trial is currently ongoing, investigating the efficacy of PI3Kα/δ-selective inhibitor copanlisib with the ER antagonist fulvestrant on ER-positive and/or progesterone receptor (PR)-positive OC, EC, and breast cancers with PI3K (PIK3CA, PIK3R1) and/or PTEN alterations (NCT05082025).