Phase 3 Study in HR+/HER2- after progression on 1L

• Research type

  Research Study

• Full 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 (HERTHENA-Breast04)

• IRAS ID

  1012280

• Contact name

  - -

• Contact email

  N/A

• Sponsor organisation

  Merck Sharp & Dohme LLC

• Clinicaltrials.gov Identifier

  NCT07060807

• Research summary

  Researchers are looking for other ways to treat breast cancer (BC) that is hormone receptor-positive and human epidermal growth factor receptor 2-negative (HR+/HER2-) and either unresectable locally advanced or metastatic.

  The current first treatment is endocrine therapy (ET). ET stops or slows certain hormones from helping cancer grow or spread. It’s sometimes given together with other treatments. These treatments may not work for some people or may stop working overtime. Second treatment options include chemotherapy or antibody drug conjugates (ADCs).

  The trial medicine HER3-DXd (MK-1022 or patritumab deruxtecan) is an ADC. Researchers want to know if HER3-DXd can treat HR+/HER2- BC when given as a second treatment.

  The main goal of this trial is to learn if people who receive HER3-DXd live longer overall or without the cancer growing or spreading than people who receive a second treatment of the researcher’s choice.

  Globally, up to about 1,000 participants will be in this trial. They will have unresectable locally advanced or metastatic HR+/HER2- BC and meet the following criteria:
  • Are at least 18 years old
  • Had the cancer grow or spread while taking or within a certain time of stopping first treatment
  • Have not received certain other treatments for the cancer

  Participants will be placed in 1 of 2 groups:
  • Group A: HER3-DXd
  • Group B: Treatment of Physician’s Choice

  HER3-DXd will be given into a vein as an intravenous (IV) infusion every 3 weeks. Chemotherapy will be either taken by mouth (pill) or as an IV infusion. How often participants get chemotherapy will depend on the type of chemotherapy. Participants will receive treatment until the cancer grows or spreads, they or the researcher decide to stop it, or the trial ends.

  Both the participants in the trial and the researchers will know the treatment a person is getting (open-label study).

  Participants may be in the trial for up to about 8 years.

• REC name

  London - Surrey Borders Research Ethics Committee

• REC reference

  25/LO/0496

• Date of REC Opinion

  5 Sep 2025

• REC opinion

  Further Information Favourable Opinion