Phase IIIb Study of Dato-DXd Treatment for Adults with HR-positive, HER2 IHC 0 Inoperable or Metastatic Breast Cancer Not Responding to Endocrine Therapy

What this Trial Is About

Researchers are evaluating the efficacy and safety of Dato-DXd in patients with hormone receptor-positive, HER2 IHC 0, locally advanced inoperable or metastatic breast cancer that is resistant to endocrine therapy. This Phase IIIb, single-arm, open-label, multinational study focuses on patients who have not undergone chemotherapy for their metastatic disease. The study aims to understand how Dato-DXd performs in this specific breast cancer group and to assess its impact on disease progression and patient outcomes. Participants will receive Dato-DXd at a dose of 6 mgkg administered intravenously every three weeks, with a maximum dose of 540 mg for participants weighing 90 kg or more. Treatment will continue until disease progression as defined by RECIST 1.1 criteria, unacceptable side effects, or participant withdrawal. The study includes collection of tumor biopsies at baseline and progression when possible, along with repeated liquid biopsies during the treatment period to analyze biomarkers related to response and resistance. Imaging scans will be conducted every 8 weeks for the first 48 weeks and then every 12 weeks until disease progression. During the study, participants will undergo regular assessments including tumor imaging, laboratory tests, and monitoring for side effects such as oral mucositis and ocular events. Researchers will track progression-free survival as the primary outcome over approximately 24 months. Secondary outcomes include response rates, duration of response, clinical benefit, overall survival, and safety measures. Participants are expected to provide informed consent and comply with study requirements, with close monitoring throughout the treatment period.

A Study of Dato-DXd in Inoperable or Metastatic Hormone Receptor-positive, HER2 IHC 0 Breast Cancer