Initial ribociclib plus endocrine therapy for HR +/ HER2 − advanced breast cancer in pre‐ and postmenopausal Chinese women: Primary results from a phase 2 randomized study

Abstract Background The MONALEESA‐7 and ‐2 phase 3 randomized trials demonstrated a statistically significant progression‐free survival (PFS) and overall survival (OS) benefit with initial ribociclib + endocrine therapy (ET) versus placebo + ET in pre‐ and postmenopausal patients with hormone receptor–positive (HR+)/human epidermal growth factor receptor 2–negative (HER2−) advanced breast cancer (ABC), respectively. Similar trends were observed in Asian subgroup analyses. This phase 2 bridging study of initial ET + ribociclib enrolled pre‐ and postmenopausal patients with HR+/HER2– ABC from China and was conducted to demonstrate consistency of PFS results in a Chinese population relative to the global MONALEESA‐7 and ‐2 studies. Methods Patients were randomized (1:1) to ET (nonsteroidal aromatase inhibitor + goserelin for premenopausal patients; letrozole for postmenopausal patients) + either ribociclib or placebo. The primary endpoint was investigator‐assessed PFS. Results As of April 25, 2022, the median follow‐up was 34.7 months in both cohorts. In the premenopausal cohort, median PFS was 27.6 months in the ribociclib arm (n = 79) versus 14.7 months in the placebo arm (n = 77) (hazard ratio 0.67 [95% CI: 0.45, 1.01]). In the postmenopausal cohort, median PFS was not reached in the ribociclib arm versus 18.5 months in the placebo arm (n = 77 in each arm) (hazard ratio 0.40 [95% CI: 0.26, 0.62]). Data also suggested improvements in secondary efficacy endpoints, although OS data were not mature. The safety profile in this population was consistent with that in global studies. Conclusions These data demonstrate a favorable benefit–risk profile for ribociclib + ET in Chinese patients.