Palazestrant in Combination With Ribociclib for the First-line Treatment of ER+/HER2- Advanced Breast Cancer

Overall Survival (OS)

To compare OS between investigational and control arms.

Time frame: From Date of Randomization until Death Due to Any Cause (estimated as up to 5.5 years)

Progression Free Survival (PFS)

To evaluate PFS based on Blinded Independent Review Committee (BIRC) assessment

Time frame: From Date of Randomization until Disease Progression or Death Due to Any Cause (estimated as up to 3.5 years)

Overall response Rate (ORR)

To evaluate ORR based on Blinded Independent Review Committee (BIRC) assessment

Time frame: From Date of Randomization until Tumor Response (estimated as up to 3.5 years)

Duration of Response (DOR)

To evaluate DOR based on Blinded Independent Review Committee (BIRC) assessment

Time frame: From Date of Tumor Response (CR or PR) until Disease Progression (estimated as up to 3.5 years)

Clinical Benefit Rate (CBR)

To evaluate CBR based on Blinded Independent Review Committee (BIRC) assessment

Time frame: Proportion of subjects achieving CR, PR or SD with duration of at least 24 weeks (estimated as up to 3.5 years)

Overall response Rate (ORR)

To evaluate ORR based on local investigator assessment

Time frame: From Date of Randomization until Tumor Response (estimated as up to 3.5 years)

Duration of Response (DOR)

To evaluate DOR based on local investigator assessment

Time frame: From Date of Tumor Response (CR or PR) until Disease Progression (estimated as up to 3.5 years)

Clinical Benefit Rate (CBR)

To evaluate CBR based on local investigator assessment

Time frame: Proportion of subjects achieving CR, PR or SD with duration of at least 24 weeks (estimated as up to 3.5 years)

Safety and tolerability

To evaluate safety and tolerability assessed by AEs, SAEs, dose modifications, clinical laboratory parameters, ECGs, performance status and vital sign measurements

Time frame: Up to 42 days after end of treatment (estimated as up to 3.5 years)

Pharmacokinetics (PK) of palazestrant and ribociclib

To evaluate plasma levels of palazestrant and ribociclib to establish pharmacokinetic (PK) parameters

Time frame: Every 28 days (estimated as up to 3.5 years)

Health-related patient-reported outcomes (PROs)

To evaluate the change from baseline in health-related PROs assessed using standardized instruments that are widely used in (breast) cancer clinical trials

Time frame: Every 28 days (estimated as up to 3.5 years)