ESR1 and breast cancer: This clinical trial is the first human study of OP-1250 to determine dose-limiting toxicity (DLT), maximum tolerated dose (MTD), and characterize safety and pharmacokinetic (PK) profiles (Olema Oncology Announces First Clinical Data on OP-1250 in Advanced ER+/HER2- Breast Cancer Olema Oncology, 2023).