Olema Pharmaceuticals Inc. has announced updated data from a Phase 1b/2 clinical study evaluating palazestrant (OP-1250) in combination with ribociclib for patients with estrogen receptor-positive (ER+), human epidermal growth factor receptor 2-negative (HER2-) advanced or metastatic breast cancer. The results, which will be presented at the European Society for Medical Oncology (ESMO) Congress 2025 on October 20, showed that the combination demonstrated activity across all dose cohorts and subgroups. The median progression-free survival $(PFS)$ was 15.5 months in the 120 mg palazestrant cohort overall. Among patients previously treated with CDK4/6 inhibitors, median PFS was 9.2 months for those with ESR1 wild-type tumors and 13.8 months for those with ESR1 mutant tumors. The regimen continued to show favorable tolerability and a safety profile consistent with known profiles of the individual drugs. These findings support the ongoing Phase 3 OPERA-02 trial, which is assessing the combination as a frontline therapy in advanced or metastatic breast cancer.