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RecruitingLast updated: 20 April 2026

HERTHENA-Breast04: Targeted antibody-based treatment compared to chemotherapy and other medicines for the treatment of HR+, HER2- advanced breast cancerAn Open-label, Randomized, Phase 3 Study to Evaluate Patritumab Deruxtecan Monotherapy Versus Treatment of Physician's Choice in Hormone Receptor-positive, HER2-negative Unresectable Locally Advanced or Metastatic Breast Cancer

Trial purpose

Medical clipboardCancer treatment

Tumor type

Breast Cancers Breast

Age

People18+

Trial acronym

HERTHENA-Breast04

Clinical summary

Summary

Researchers are looking for other ways to treat breast cancer that is hormone receptor-positive and human epidermal growth factor receptor 2-negative (HR+/HER2-) and either unable to be completely removed with surgery (unresectable) and has spread into nearby issue or muscles (locally advanced) or spread to other parts of the body (metastatic).

Treatment for this type of breast cancer usually includes hormone therapy (also called endocrine therapy) and sometimes a second treatment. 

The main goal of this study is to learn if people who receive patritumab deruxtecan (also known as HER3-DXd and MK-1022) live longer overall or without the cancer growing or spreading, compared to people who receive chemotherapy or a different drug caleld trastuzumab deruxtecan.

Eligible participants will be randomly allocated (by chance) into one of two treatment arms.

In the Experimental Arm, participants will receive patritumab deruxtecan via intravenous (IV) infusion every 3 weeks for approximately 13 months. Patritumumab deruxtecan is a type of targeted immunotherapy called an antibody-drug conjugate (ADC).

In the Active Comparator Arm, participants will receive the physician's choice of treatment for up to 13 months. This may be any of the following options:

  • Paclitaxel chemotherapy IV 
  • Paclitaxel chemotherapy IV 
  • Nab-paclitaxel chemotherapy IV 
  • Capecitabine chemotherapy as oral tablets
  • Liposomal doxorubicin chemotherapy IV 
  • Trastuzumab deruxtecan targeted therapy IV

Conditions

This trial is treating people with HR+, HER2- unresectable, locally advanced or metastatic breast cancer whose cancer has progressed or come back following prior treatment with CDK4/6 inhibitor and hormone therapy

Eligibility

Inclusion

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

  • Has a diagnosis of hormone receptor positive (HR+)/human epidermal growth factor receptor 2 (HER2)- invasive breast carcinoma that is either locally advanced disease not amenable to resection with curative intent (herein called unresectable) or metastatic disease not treatable with curative intent
  • Has centrally-confirmed HR+ and HER2- results and human epidermal growth factor receptor 3 (HER3) evaluable results from a biopsy obtained from a distant metastatic site or a locally advanced lesion on or after the most recent line of therapy (with certain exceptions)
  • Must have had progression or recurrence on prior cyclin-dependent kinase (CDK)4/6 inhibitor + endocrine therapy (ET) with one of the following:

    • Radiographic disease progression, as assessed by the investigator, on CDK4/6 inhibitor + ET as 1L for treatment of unresectable locally advanced or metastatic HR+/HER2- breast cancer. CDK4/6 inhibitor + ET must be the only line of therapy received in the advanced setting, or
    • Disease recurrence, either radiographic and/or confirmed histologically via biopsy as assessed by the investigator, while on adjuvant ET in combination with a CDK4/6 inhibitor OR within 24 months from the date of last dose of adjuvant CDK4/6 inhibitor
  • Has measurable disease per RECIST 1.1 as assessed by the local site investigator/radiology
  • Human immunodeficiency virus (HIV)-infected participants must have well controlled HIV on antiretroviral therapy
  • Has an Eastern Cooperative Oncology Group performance status of 0 or 1 assessed within 7 days before randomization

Exclusion

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

  • Has breast cancer amenable to treatment with curative intent
  • Is eligible to receive additional endocrine-based treatment in the advanced setting as determined by the investigator
  • Has a known germline breast cancer gene (BRCA) mutation (deleterious or suspected deleterious) where poly (ADP-ribose) polymerase (PARP) inhibitor(s) is a potential treatment option
  • Has current visceral crisis or is at risk for impending visceral crisis that has or may cause imminent organ compromise and/or other life-threatening complications
  • Has any of the following: a pulse oximeter reading <92% at rest, or requires intermittent supplemental oxygen, or requires chronic supplemental oxygen
  • Has uncontrolled, significant cardiovascular disease or cerebrovascular disease
  • Has ≥Grade 2 peripheral neuropathy.
  • Has clinically significant corneal disease
  • Has received prior chemotherapy for unresectable locally advanced or metastatic breast cancer
  • Has received prior treatment with an anti-HER3 antibody and/or antibody-drug conjugate that consists of a topoisomerase I inhibitor (eg, T-DXd) or any other topoisomerase I inhibitor therapy
  • Has received prior systemic anticancer therapy within 4 weeks (or 5 half-lives, whichever is shorter) before randomization; participants previously treated with ET plus a CDK4/6 inhibitor may participate as long as at least 2 weeks have elapsed since the last dose of therapy was administered
  • Has received prior radiotherapy for non-central nervous system disease, or required corticosteroids for radiation-related toxicities, within 14 days of the first dose of study intervention
  • Has a diagnosis of immunodeficiency or is receiving chronic systemic steroid therapy
  • Has known additional malignancy that is progressing or has required active treatment within the past 3 years
  • Has history of (noninfectious) pneumonitis/interstitial lung disease (ILD) that required steroids, has current pneumonitis/interstitial lung disease, or has suspected ILD/pneumonitis that cannot be ruled out by imaging at Screening
  • Has severe hypersensitivity (≥Grade 3) to HER3-DXd and/or any of its excipients
  • Has severe hypersensitivity (≥Grade 3) to all the available TPC and/or any of their excipients

Inclusion

  • You have had treatment, but your cancer has come back (relapsed or recurrent).
  • Your cancer has spread to other parts of the body (metastatic) or has grown into nearby parts of the body (locally advanced).
  • Your cancer has not spread to other parts of the body, but it is not possible to perform surgery to remove it (unresectable).
  • You have had treatment but your cancer has gotten worse or has not responded to the treatment you have been given.
  • You have had a certain type of treatment or surgical procedure.

Exclusion

  • You have certain types of non-cancer medical conditions.
  • You have had certain treatments, surgical procedures or drugs.
Message

Clinical trials have complex eligibility criteria, and other criteria may apply for this trial. Ask your doctor about whether this trial could be right for you.

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More information

Trial Identifiers

Information on this page is partially produced from ClinicalTrials.gov, EU Clinical Trials Register *. View further details about this trial on the registry via the links below:

  • NCT07060807 *
  • 2025-520582-51-00 *
  • MK1022-016 -00; 1022-016; U1111-1317-5490; JRCT2031250297

Trial sponsor

Merck Sharp & Dohme LLC

Scientific Title

An Open-label, Randomized, Phase 3 Study to Evaluate Patritumab Deruxtecan Monotherapy Versus Treatment of Physician's Choice in Hormone Receptor-positive, HER2-negative Unresectable Locally Advanced or Metastatic Breast Cancer

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