A Phase 2, Open Label, Multicenter, Single Arm Trial Evaluating the Activity and Safety of Abemaciclib + Aromatase Inhibitors (AIs) as Second-Line Treatment After First-Line Fulvestrant in Hormone-Receptor-Positive (HR+), Human-Epidermal-Growth-Factor-Receptor-Negative (HER2-) Metastatic Breast Cancer (MBC) Patients. Final Results of HERMIONE-7 Trial

Background and Purpose: CDK 4/6 inhibitors with ET are the recommended choice as 1st-line therapy in HR+/HER2- MBC patients, however ET alone could remain an option for some of them. HERMIONE-7 is a multicenter, single-arm, Phase II study, aimed to evaluate Abemaciclib 150 mg BID + AIs, in patients who progressed on 1st line Fulvestrant. Materials and Methods: Primary aim was the efficacy of Abemaciclib + AIs in terms of Clinical Benefit Rate (CBR), secondary aims were Time to Progression (TTP), Overall Response Rate (ORR), duration of response (DOR), and safety. Results: From April 2020 to January 2022, we enrolled 31 patients. Median age was 72 years (range 47-86), 55% had < 2 comorbidities, mainly hypertension (12, 38.7%). Clinical Benefit Rate was 69% (95% CI, 49-85) and ORR was 21% (95%CI, 8-40). 1-year TTP and OS rates were 53.8% (95% CI, 38.6-74.9%) and 69.5% (95% CI, 54.8%-88.5%), respectively. Main adverse events remain diarrhea (80.6%), fatigue (54.8%) and nausea (35.5%), 3 patients (10.7%) had non drug-related fatal events. Conclusions: HERMIONE-7 study showed that 2nd-line treatment with Abemaciclib + AIs is a feasible option in MBC patients who progressed on Fulvestrant in 1st-line setting and could be an alternative especially in terms of optimizing the cost-benefit ratio in some Countries.