Key Inclusion Criteria:

- Age > 18 years, with residual invasive triple negative breast cancer (TNBC) in the
breast or lymph nodes after neoadjuvant therapy and surgery:

- TNBC criteria for the study is defined as estrogen receptor (ER) and progesterone
receptor (PR) < 10%, human epidermal growth factor receptor 2 (HER2)-negative per
American Society of Clinical Oncology and College of American Pathologists
(ASCO/CAP) guidelines (immunohistochemistry (IHC) and/or in situ hybridization
(ISH)).

- Adequate excision and surgical removal of all clinically evident of disease in the
breast and/or lymph nodes and have adequately recovered from surgery.

- Submission of both pre-neoadjuvant treatment diagnostic biopsy and resected residual
invasive disease tissue.

- Eastern Cooperative Oncology Group (ECOG) performance status 0-1.

- Individuals must have received appropriate radiotherapy and have recovered prior to
starting study treatment.

- Adequate organ function.

Key Exclusion Criteria:

- Stage IV (metastatic) breast cancer as well as history of any prior (ipsi- or
contralateral) invasive breast cancer.

- Prior treatment with another stimulatory or coinhibitory T-cell receptor agent (eg,
cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4), OX-40, cluster of
differentiation 137 (CD137), prior treatment with any HER2-directed agent.

- Evidence of recurrent disease following preoperative therapy and surgery.

- Prior treatment with topoisomerase 1 inhibitors or antibody-drug conjugates (ADCs)
containing a topoisomerase inhibitor.

- Individuals with known germline breast cancer gene (BRCA) mutations.

- Myocardial infarction or unstable angina pectoris within 6 months of enrollment or
history of serious ventricular arrhythmia (ie, ventricular tachycardia or ventricular
fibrillation), high-grade atrioventricular block, or other cardiac arrhythmias or Left
ventricular ejection fraction (LVEF) of < 50%

- Active serious infections requiring anti-microbial therapy.

Note: Other protocol defined Inclusion/Exclusion criteria may apply.

Note: Other protocol defined Inclusion/Exclusion Criteria may apply.

Eligibility last updated 6/27/23. Questions regarding updates should be directed to the study team contact.