Overview

Researchers are looking for new ways to treat triple-negative breast cancer (TNBC) and hormone receptor (HR) low positive/human epidermal growth factor receptor-2 (HER2) negative breast cancer. The main goals of this study are to learn:

• About the safety of the study treatments and if people tolerate them
• If people who receive patritumab deruxtecan, pembrolizumab, and chemotherapy before surgery have fewer cancer cells removed during surgery compared to those who receive only pembrolizumab (pembro) and chemotherapy.

Eligibility

Inclusion Criteria:

The main inclusion criteria include but are not limited to the following:

• Has locally advanced, non-metastatic (M0), breast cancer, defined as any of the following combined primary tumor (T) and regional lymph node (N) staging per current American Joint Committee on Cancer (AJCC) criteria: cT1c, N1-N2; cT2, N0-N2; cT3, N0-N2; or cT4a-d, N0-N2
• Has centrally confirmed diagnosis of breast cancer that is triple-negative or HR-low+/HER2- breast cancer that will be treated according to the triple-negative breast cancer (TNBC) paradigm
• Participants who are Hepatitis B surface antigen (HBsAg) positive are eligible if they have received Hepatitis B virus (HBV) antiviral therapy for at least 4 weeks and have undetectable HBV viral load
• Participants with a history of Hepatitis C virus (HCV) infection are eligible if HCV viral load is undetectable
• Has an Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 1 within 28 days prior to allocation/randomization
• Has left ventricular ejection fraction (LVEF) of ≥50% or ≥ lower limit of normal (LLN) as assessed by echocardiogram (ECHO) or multigate acquisition scan (MUGA) scan

Exclusion Criteria:

The main exclusion criteria include but are not limited to the following:

• Has uncontrolled or significant cardiovascular disease before randomization
• Has clinically significant corneal disease
• Has human immunodeficiency virus (HIV) infection with a history of Kaposi sarcoma and/or multicentric Castleman disease
• Has received prior therapy with an anti-programmed death (PD)-1, anti-PD-L1, or anti-PD-L2 agent, or with an agent directed to another stimulatory or coinhibitory T-cell receptor
• Has received any prior treatment, including radiation, systemic therapy, and/or definitive surgery for currently diagnosed breast cancer
• Has received prior treatment with an anti-human epidermal growth factor receptor 3 (HER3) antibody and/or antibody-drug conjugate (ADC) that consists of an exatecan derivative that is a topoisomerase I inhibitor (e.g., trastuzumab deruxtecan)
• Has metastatic (Stage IV) breast cancer or cN3 nodal involvement
• Has known additional malignancy that is progressing or has required active treatment within the past 5 years
• Has known active central nervous system (CNS) metastases and/or carcinomatous meningitis
• Has a history of (noninfectious) pneumonitis/interstitial lung disease that required steroids or has current pneumonitis/interstitial lung disease, or where suspected ILD/pneumonitis cannot be ruled out by standard diagnostic assessments
• Has an active infection requiring systemic therapy
• Has concurrent active HBV and HCV infection
• Has clinically severe respiratory compromise resulting from intercurrent pulmonary illness