Study of Patritumab Deruxtecan Plus Pembrolizumab With Other Anticancer Agents in Participants With High-Risk Early-Stage Triple-Negative or Hormone Receptor-Low Positive/HER-2 Negative Breast Cancer (MK-1022-010, HERTHENA-Breast-03)

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 thefollowing combined primary tumor (T) and regional lymph node (N) staging per currentAmerican 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 orHR-low+/HER2- breast cancer that will be treated according to the triple-negativebreast cancer (TNBC) paradigm

• Participants who are Hepatitis B surface antigen (HBsAg) positive are eligible ifthey have received Hepatitis B virus (HBV) antiviral therapy for at least 4 weeksand have undetectable HBV viral load

• Participants with a history of Hepatitis C virus (HCV) infection are eligible if HCVviral 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 sarcomaand/or multicentric Castleman disease

• Has received prior therapy with an anti-programmed death (PD)-1, anti-PD-L1, oranti-PD-L2 agent, or with an agent directed to another stimulatory or coinhibitoryT-cell receptor

• Has received any prior treatment, including radiation, systemic therapy, and/ordefinitive 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 exatecanderivative 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 treatmentwithin the past 5 years

• Has known active central nervous system (CNS) metastases and/or carcinomatousmeningitis

• Has a history of (noninfectious) pneumonitis/interstitial lung disease that requiredsteroids or has current pneumonitis/interstitial lung disease, or where suspectedILD/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 pulmonaryillness