A Study of Patritumab Deruxtecan (HER3-DXd) in Combination With Trastuzumab Deruxtecan (T-DXd) in Participants With HR-Positive, HER2-Low or HER2-Ultralow Unresectable or Metastatic Breast Cancer

Sponsor
Daiichi Sankyo
Study ID
NCT07701941
Phase
PHASE1/PHASE2
Status
Not Yet Recruiting

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Conditions

  • HER2-low or HER2-ultralow
  • Hormone Receptor Positive
  • Unresectable or Metastatic Breast Cancer

Eligibility Criteria

Sex
ALL
Age
18 Years - N/A
Healthy Volunteers
Not accepted

Interventions

  • Patritumab deruxtecan — DRUG
    Intravenous administration as determined by treatment arm.
  • Trastuzumab deruxtecan — DRUG
    Intravenous administration as determined by treatment arm.

Study Details

The primary purpose of the study is to assess the safety, tolerability, and anti-tumor activity of HER3-DXd and T-DXd in the combination dosing regimens in participants with hormone receptor positive, HER2-low or HER2-ultralow, unresectable, or metastatic breast cancer.

Key Dates

First listed
Jul 14, 2026
Start date
Aug 3, 2026
Status verified
Jul 2026
Primary completion
Jan 1, 2031
Completion
May 1, 2032

Study Design

Enrollment
220 participants (estimated)
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
TREATMENT

Arms

  • Experimental: Part 1: Arm 1: Dose Regimen Determination
    Participants with unresectable or metastatic breast cancer (mBC) will receive T-DXd and HER3-DXd in combination regimen A until disease progression, death, unacceptable toxicity, or trial close.
  • Experimental: Part 1: Arm 2: Dose Regimen Determination
    Participants with unresectable or mBC will receive T-DXd and HER3-DXd in combination regimen B until disease progression, death, unacceptable toxicity, or trial close.
  • Experimental: Part 2: Arm 3: Dose Expansion
    Participants with unresectable or mBC will receive T-DXd and HER3-DXd in a combination regimen based on the available Part 1 data until disease progression, death, unacceptable toxicity, or trial close.
  • Active Comparator: Part 2: Arm 4: Monotherapy
    Participants with unresectable or mBC will receive T-DXd monotherapy until disease progression, death, unacceptable toxicity, or trial close.

Primary Outcome Measure

Part 1: Number of Participants With at Least One Treatment-emergent Adverse Event (TEAE) and Serious Adverse Event (SAE) [ Time Frame: Up to approximately 4.5 years ]

Central Contacts