This study will evaluate the efficacy, safety, and pharmacokinetics of inavolisib in
combination with palbociclib and fulvestrant compared with placebo plus palbociclib and
fulvestrant in patients with PIK3CA-mutant, hormone receptor (HR)-positive, HER2-negative
locally advanced or metastatic breast cancer whose disease progressed during treatment or
within 12 months of completing adjuvant endocrine therapy and who have not received prior
systemic therapy for metastatic disease.