A Study of Abemaciclib (LY2835219) in Participants With Breast Cancer

Inclusion Criteria: * Have a diagnosis of HR+, HER2- breast cancer. Although not required as a protocol procedure, metastatic disease should be considered for biopsy whenever possible to reassess hormone receptor (HR) and human epidermal growth factor receptor 2 (HER2) status if clinically indicated. * To fulfill the requirement for HR+ disease, a breast cancer must express, by immunohistochemistry (IHC), at least 1 of the HRs (estrogen receptor \[ER\], progesterone receptor \[PgR\]) as defined in the relevant American Society of Clinical Oncology (ASCO)/College of American Pathologists (CAP) guidelines. * To fulfill the requirement of HER2- disease, a breast cancer must not demonstrate, at initial diagnosis or upon subsequent biopsy, overexpression of HER2 by either IHC or in-situ hybridization as defined in the relevant ASCO/CAP guidelines. * Meet either Inclusion Criterion (2a) or Inclusion Criterion (2b). Participants meeting Inclusion Criterion 2a will be enrolled in Cohort A and participants meeting Inclusion Criterion 2b will be enrolled in Cohort B. * (2a) Have locoregionally recurrent disease not amenable to resection or radiation therapy with curative intent or metastatic disease. * Relapsed with radiologic evidence of progression more than 1 year from completion of adjuvant endocrine therapy and have received no prior endocrine therapy for locoregionally recurrent or metastatic disease (Note: prior adjuvant endocrine therapy for localized disease may have …