A Phase III, multicenter, randomized placebo-controlled study of atezolizumab (anti-PD-L1 antibody) in combination with nab paclitaxel compared with placebo with nab paclitaxel for patients with previously untreated metastatic triple negative breast cancer.

• Metastatic or locally advanced, histologically documented TNBC
• No prior chemotherapy or targeted systemic therapy for metastatic TNBC (prior endocrine tx with AR therapy is allowed)
• Measurable disease by RECIST 1.1
• ECOG PS 0-1
• No known CNS disease, except for treated asymptomatic CNS mets
• No history of infratentorial CNS mets, regardless of symptoms or treatment
• No symptomatic hypercalcemia
• Not currently receiving denosumab (bisphosphonate tx to prevent skeletal events is OK)
• No history of autoimmune disease
• No history of pneumonitis (history of radiation pneumonitis is allowed)
• HIV negative
• No receipt of systemic steroids (unless low dose and chronic) within 2 weeks of randomization

Primary- PFS + OS; Secondary- ORR, DOR, time to deterioration, safety