Inclusion Criteria:

* Metastatic or locally-advanced, histologically documented TNBC (absence of HER2, ER, and PR expression)

* Part D only: Tumor tissue PD-L1 Combined Positive Score <10 expression.
* Have not previously received cytotoxic therapy for the treatment of unresectable locally-advanced breast cancer or metastatic breast cancer
* At least 6 months since prior treatment with curative intent and recurrence
* At least 1 tumor 10mm in diameter or greater OR lymph node of at least 15 mm in short axis
* Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1
* Able to provide biopsy tissue for biomarker analysis
* Meet baseline laboratory data criteria

Exclusion Criteria:

* Prior immune-oncology therapy
* Pre-existing neuropathy of at least Grade 2
* History of carcinomatous meningitis or active central nervous system (CNS) metastases. Patients are eligible if CNS metastases are adequately treated and patients have neurologically returned to baseline (except for residual signs or symptoms related to the CNS treatment) for at least 4 weeks prior to enrollment. Patients must be off corticosteroids.
* Received prior radiotherapy within 2 weeks of start of study treatment or have not adequately recovered from prior radiotherapy
* Active autoimmune disease requiring systemic treatment within the past 2 years
* History of interstitial lung disease
* Current pneumonitis or history of pneumonitis requiring steroids