A Phase 2, Open-label, Randomized Study Investigating the Tolerability of Concurrent Versus Staggered Administration of Abemaciclib and Endocrine Therapy With Tersolisib in Patients With HR+, HER2- Node-Positive, PIK3CA-Mutated Early Breast Cancer.

Inclusion Criteria: * Have histologically or cytologically confirmed breast cancer, defined as individuals with: * early stage, resected, invasive breast cancer without evidence of distant metastasis, and * have confirmed hormone receptor positive (HR+), human epidermal growth factor receptor 2 negative (HER2-) status defined by * Hormone Receptor (HR) status: documented estrogen receptor positive (ER+) and/or progesterone receptor+ tumor, defined as greater than or equal to (≥) 1% of tumor cells stained positive, assessed locally on primary disease specimen, as defined by American…