A Study of PI3-Kinase Inhibitor GDC-0941 in Combination With Paclitaxel, With and Without Bevacizumab or Trastuzumab, and With Letrozole, in Participants With Locally Recurrent or Metastatic Breast Cancer

This is an open-label, multicenter, Phase Ib dose-escalation study to assess the safety, tolerability, and pharmacokinetics of oral (PO) pictilisib administered with letrozole or intravenous (IV) paclitaxel with and without IV bevacizumab or IV trastuzumab in participants with locally recurrent or metastatic breast cancer. The study consists of three parts. Part 1 (pictilisib will be administered in 21+7 schedule along with paclitaxel and/or bevacizumab), Part 2 (pictilisib will be administered in 5+2 schedule along with paclitaxel and/or bevacizumab or trastuzumab) and Part 3 (pictilisib will be administered in combination with letrozole). Part 1 and Part 2 consists of two stages; a dose escalation stage and a cohort-expansion stage.