The purpose of this study was to evaluate the preliminary safety and tolerability of ribociclib to standard adjuvant endocrine therapy (ET) in patients with hormone receptor (HR) positive, Human Epidermal Growth Factor Receptor2 (HER2) negative high risk early breast cancer (EBC).~Originally, this was a randomized, Phase III, double-blind, placebo-controlled, multi-center, international study to evaluate efficacy and safety of ribociclib with ET as an adjuvant treatment in patients with HR-positive, HER2-negative, high risk EBC.~Patients were randomized at a ratio of 1:1 to receive either ribociclib or placebo for approximately 24 months in combination with a standard adjuvant ET with ET continued for at least 60 months.~However, following a review of the ribociclib development program strategy, a decision was taken to explore a different approach by initiating a single Phase III study for simplicity of trial logistics and for the purpose of analyzing the overall population through a single clinical trial. Therefore, this study was closed to enrollment early and was amended to be an open label, multi-center Phase II study conducted in the US only. All randomized patients were unblinded; patients randomized to placebo were permanently discontinued from the study and patients randomized to ribociclib were offered the option to continue treatment with ribociclib + ET.~The study included a screening phase (28 days), a treatment phase composed of maximum of 26 cycles of ribociclib in combination with ET (approximately 24 months) or until disease recurrence, intolerable toxicity, withdrawal of consent, or discontinuation from the study treatment for any other reason, whichever was earlier, and a 30 days safety follow up from last dose of ribociclib. Ribociclib was given orally once a day on days 1 to 21 in each 28 days cycle.~Safety was assessed for each patient until 30 days after the last dose of ribociclib and included routine safety monitoring except in case of death, loss to follow up or withdrawal of consent.
This was an open label, multi-center protocol for U.S. patients enrolled in the study of ribociclib with endocrine therapy as an adjuvant treatment in patients with hormone receptor-positive, HER2-negative, high risk early breast cancer