A Phase 1/2 interventional study of Patritumab deruxtecan and Trastuzumab in Breast Neoplasms and Breast Cancer, sponsored by Merck Sharp & Dohme LLC. Recruiting at 18 sites in 6 countries. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-10-06.
Sponsored by Merck Sharp & Dohme LLC · Phase 1/2, Interventional, and Treatment
Researchers want to learn if patritumab deruxtecan (MK-1022) can treat certain breast cancers. The breast cancers being studied are HER2 positive unresectable locally advanced or metastatic (the cancer has spread to other parts of the body). The goals of this study are to learn:
The following countries will be participating in the trial: Canada, United Kingdom, Israel, Japan, South Korea, and USA.
12,544 studies on the registry are indexed under Breast Neoplasms; 2,892 are open to participants now.
This study's planned enrollment of 181 is above the median of 72 across 9,303 interventional studies indexed under Breast Neoplasms.
Browse Breast Neoplasms studies →Merck Sharp & Dohme LLC is the lead sponsor of 2,114 studies on the registry; 133 are open to participants now.
Of its 489 completed or terminated interventional studies of FDA-regulated products, 362 (74%) have results posted.
Counted across the registry records on this site, refreshed daily.
The main inclusion criteria include but are not limited to the following:
Part 1 Arm 1:
Part 1 Arm 2:
-Has received no more than 5 prior lines of anti-HER2 therapy in the locally advanced or metastatic setting
Part 1 Arm 3:
-Has received and had disease progression from T-DXd treatment in any setting and a maximum of 3 prior lines of anti-HER2 therapy in the locally advanced or metastatic setting. T-DXd must be the most recent therapy received before enrollment.
Part 2 : Has not received prior systemic therapy (including T-DXd) for recurrent locally advanced or metastatic breast cancer (mBC).
Exclusion Criteria:
The main exclusion criteria include but are not limited to the following:
Part1: Arm 3 ONLY
- Has received prior treatment with tucatinib, lapatinib, or neratinib, or any investigational HER2-targeted tyrosine kinase inhibitors in the locally advanced or metastatic setting
Participants receive patritumab deruxtecan intravenous (IV) infusion and trastuzumab or trastuzumab biosimilar IV infusion on Day 1 of each 21-day cycle (every 3 weeks) until disease progression, intolerable toxicity, or investigator decision.
Biological: Patritumab deruxtecan · Biological: Trastuzumab · Biological: Trastuzumab Biosimilar
Participants receive patritumab deruxtecan IV infusion, pertuzumab IV infusion, and trastuzumab or trastuzumab biosimilar IV infusion on Day 1 of each 21-day cycle (every 3 weeks) until disease progression, intolerable toxicity, or investigator decision.
Biological: Patritumab deruxtecan · Biological: Trastuzumab · Biological: Trastuzumab Biosimilar · Biological: Pertuzumab
Participants receive patritumab deruxtecan IV infusion and trastuzumab or trastuzumab biosimilar IV infusion on Day 1 of each 21-day cycle (every 3 weeks), and tucatinib is administered orally twice daily for each 21-day cycle, until disease progression, intolerable toxicity, or investigator decision.
Biological: Patritumab deruxtecan · Biological: Trastuzumab · Biological: Trastuzumab Biosimilar · Biological: Tucatinib
Participants receive patritumab deruxtecan IV infusion, pertuzumab IV infusion, and trastuzumab or trastuzumab biosimilar IV infusion on Day 1 of each 21-day cycle (every 3 weeks) until disease progression, intolerable toxicity, or investigator decision.
Biological: Patritumab deruxtecan · Biological: Trastuzumab · Biological: Trastuzumab Biosimilar · Biological: Pertuzumab
Patritumab deruxtecan administered via IV infusion
Also known as: MK-1022, HER3-DXd, U3-1402
Trastuzumab administered via IV infusion
Also known as: Herceptin®
Trastuzumab biosimilar administered via IV infusion
Also known as: Trazimera®, Ogivri®, Herzuma®, Ontruzant®, Kanjinti®, Hercessi®
Pertuzumab administered via IV infusion
Tucatinib administered as oral tablets
Part 1: Number of Participants Experiencing Dose-Limiting Toxicity (DLT)
DLT will be defined as any drug-related AE observed during the DLT evaluation period that results in a change to a given dose or a delay in initiating the next cycle. The number of participants who experience a DLT will be presented.
Time frame: Up to 21 days
Part 1: Number of Participants with One or More Adverse Events (AEs)
An AE is defined as any unfavorable and unintended sign, symptom, disease, or worsening of preexisting condition temporally associated with study treatment and irrespective of causality to study treatment. The number of participants who experience an AE will be presented.
Time frame: Up to approximately 36 months
Part 1: Number of Participants who Discontinue Study Intervention Due to an AE
An AE is defined as any unfavorable and unintended sign, symptom, disease, or worsening of preexisting condition temporally associated with study treatment and irrespective of causality to study treatment. The number of participants who discontinue study treatment due to an AE will be presented.
Time frame: Up to approximately 12 months
Part 2: Objective Response Rate (ORR)
ORR is defined as the percentage of participants with Complete Response (CR: disappearance of all target lesions) or Partial Response (PR: at least a 30% decrease in the sum of diameters of target lesions) per Response Evaluation Criteria in Solid Tumors (RECIST) 1.1. The percentage of participants who experience CR or PR as assessed by Blinded Independent Central Review (BICR)will be presented.
Time frame: Up to approximately 36 months
Part 1: Maximum Plasma Concentration (Cmax) of Patritumab Deruxtecan Antibody-Drug Conjugate (ADC)
Blood samples collected at designated time points will be used to determine the Cmax of patritumab deruxtecan ADC.
Time frame: At designated time points (up to ~13 months)
Part 1: Trough Concentration (Ctrough) of Patritumab Deruxtecan ADC
Blood samples collected at designated time points will be used to determine the Ctrough of patritumab deruxtecan ADC.
Time frame: At designated time points (up to ~13 months)
Part 1: Area Under the Plasma Concentration-Time Curve (AUC) of Patritumab Deruxtecan ADC
Blood samples collected at designated time points will be used to determine the AUC of patritumab deruxtecan ADC.
Time frame: At designated time points (up to ~13 months)
Part 1: Maximum Plasma Concentration (Cmax) of Total Patritumab Deruxtecan Antidrug Antibody (ADA)
Blood samples collected at designated time points will be used to determine the Cmax of total patritumab deruxtecan ADA.
Time frame: At designated time points (up to ~13 months)
Part 1: Trough Concentration (Ctrough) of Total Patritumab Deruxtecan ADA
Blood samples collected at designated time points will be used to determine the Ctrough of total patritumab deruxtecan ADA.
Time frame: At designated time points (up to ~13 months)
Part 1: Area Under the Plasma Concentration-Time Curve (AUC) of Total Patritumab Deruxtecan ADA
Blood samples collected at designated time points will be used to determine the AUC of total patritumab deruxtecan ADA.
Time frame: At designated time points (up to ~13 months)
Part 1: Maximum Plasma Concentration (Cmax) of Patritumab Deruxtecan Free Payload
Blood samples collected at designated time points will be used to determine the Cmax of patritumab deruxtecan free payload.
Time frame: At designated time points (up to ~13 months)
Part 1: Trough Concentration (Ctrough) of Patritumab Deruxtecan Free Payload
Blood samples collected at designated time points will be used to determine the Ctrough of patritumab deruxtecan free payload.
Time frame: At designated time points (up to ~13 months)
Part 1: Area Under the Plasma Concentration-Time Curve (AUC) of Patritumab Deruxtecan Free Payload
Blood samples collected at designated time points will be used to determine the AUC of patritumab deruxtecan free payload.
Time frame: At designated time points (up to ~13 months)
Part 2: Duration of Response (DOR)
For participants who demonstrate a confirmed Complete Response (CR: disappearance of all target lesions) or Partial Response (PR: at least a 30% decrease in the sum of diameters of target lesions) per RECIST 1.1, DOR is defined as the time from first documented evidence of CR or PR until progressive disease (PD) or death. Per RECIST 1.1, PD is defined as at least a20% increase in the sum of diameters of target lesions. In addition to the relative increase of 20%, the sum must also demonstrate an absolute increase of at least 5 mm. The appearance of one or more new lesions is alsoc onsidered PD. DOR as assessed by BICR will be presented.
Time frame: Up to approximately 36 months
Part 2: Progression Free Survival (PFS)
PFS is defined as the time from first day of study intervention to the first documented progressive disease (PD)or death due to any cause, whichever occurs first as assessed by BICR. Per RECIST 1.1, PD is defined as ≥20% increase in the sum of diameters of target lesions. In addition to the relative increase of 20%, the sum must also demonstrate an absolute increase of ≥5 mm. The appearance of one or more new lesions is also considered PD. The appearance of one or more new lesions is also considered PD. PFS as assessed by BICR will be presented.
Time frame: Up to approximately 36 months
Part 2: Number of Participants with One or More AEs
An AE is defined as any unfavorable and unintended sign, symptom, disease, or worsening of preexisting condition temporally associated with study treatment and irrespective of causality to study treatment. The number of participants who experience an AE will be presented.
Time frame: Up to approximately 36 months
Part 2: Number of Participants who Discontinue Study Intervention Due to an AE
An AE is defined as any unfavorable and unintended sign, symptom, disease, or worsening of preexisting condition temporally associated with study treatment and irrespective of causality to study treatment. The number of participants who experience an AE will be presented.
Time frame: Up to approximately 12 months
Plan to share: Yes — https://trialstransparency.msdclinicaltrials.com/pdf/ProcedureAccessClinicalTrialData.pdf
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
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