A Study of a Medicine Called Atirmociclib in Combination With Giredestrant in Adult Participants With ER-positive, HER2-negative Early-stage Breast Cancer

KEY INCLUSION CRITERIA

1. Histologically confirmed unilateral primary adenocarcinoma of the breast

• ER-positive by local assessment
• documented HER2-negative

2. Node positive or node negative as defined by:
   • Pathological node positive (microscopic and/or macroscopic tumor involvement >/=pN1)
   • pN0 and pT >1cm with at least one of the following:
     1. pT4N0 or
     2. histologically Grade 3 disease or
     3. high-risk classification based on genomic assay
3. Randomization within 16 months of definitive breast surgery
4. If indicated, completed adjuvant and/or neoadjuvant chemotherapy, adjuvant radiation therapy >/= 21 days prior to randomization

KEY EXCLUSION CRITERIA

1. Distant metastases of breast cancer beyond regional lymph nodes
2. Multicentric or multifocal breast cancer if any tumor foci meet pathologic criteria for ER(-) or HER2(+)
3. Clinically significant cardiovascular disease or cardiac repolarization abnormality for 6 months prior to randomization; resting heart rate <50bpm
4. Has received the following prior systemic anti-cancer therapy for breast cancer

• prior atirmociclib, giredestrant, other investigational anti-cancer agent
• prior treatment with olaparib

NOTES:

• short course of prior neo/adjuvant CDK4/6 inhibitor treatment (</=8 weeks) is permitted; 10-day washout period required
• short course of prior neoadjuvant and/or adjuvant ET (</=18 weeks) is permitted; 35-day washout period for tamoxifen is required

5. Prior treatment with investigational product within 30 days or 5 half-lives