Efficacy and Safety of Ribociclib in Pre- and Postmenopausal Chinese Women With HR Positive, HER2-negative, Advanced Breast Cancer.

The study included three cohorts of subjects: a premenopausal cohort and a postmenopausal cohort, both randomized and double-blind, and an open-label, single-arm pharmacokinetic (PK) cohort of postmenopausal women. The premenopausal cohort assessed the efficacy and safety of treatment with a non-steroidal aromatase inhibitor (NSAI; letrozole or anastrozole) combined with goserelin and ribociclib, compared with NSAI plus goserelin and placebo. The postmenopausal cohort assessed the efficacy and safety of ribociclib plus letrozole versus placebo plus letrozole. The study consisted of three periods: screening, treatment, and follow-up. 1. Screening phase: The study began with a 28-day screening period during which potential participants were evaluated against inclusion and exclusion criteria before initiating treatment on Day 1. 2. Treatment phase: Eligible participants in the premenopausal and postmenopausal cohorts were randomized in a 1:1 ratio to one of two treatment arms, while participants in the PK cohort were not randomized. Treatment continued until disease progression, unacceptable toxicity, withdrawal of consent, loss to follow-up, or study termination. Following a statistically significant progression-free survival (PFS) benefit observed at the primary analysis and implementation of Protocol Amendment 5 (dated 18-Oct-2022), participants and investigators were unblinded. Participants still receiving placebo were offered the option to cross over to ribociclib, at the investigator's discretion and with participant consent. 3. Follow-up phase: * Safety follow-up: All participants were followed for safety for up to 30 days after the last dose of study treatment, except in cases of death, loss to follow-up, or withdrawal of consent. * Efficacy follow-up: Tumor assessments were performed at baseline and every 8 weeks (±1 week) from randomization for the first 18 months, then every 12 weeks (±1 week) until 36 months, and thereafter as clinically indicated until progression. Participants who discontinued treatment for reasons other than disease progression continued tumor assessments according to the same schedule until progression, death, withdrawal of consent, or loss to follow-up. * Survival follow-up: Survival status was assessed every 12 weeks (±1 week) for all participants, regardless of treatment discontinuation reason, unless consent was withdrawn. The end of the study was defined as the earliest occurrence of one of the following: all participants had discontinued or died; a new clinical study offering ribociclib became available and all ongoing participants were eligible for transfer; or participants still benefiting from treatment could continue receiving it through an alternative setting.