Open Actively Recruiting

Trial of H3B-6545, in Women With Locally Advanced or Metastatic Estrogen Receptor-positive, HER2 Negative Breast Cancer


Brief Summary

The primary purpose of phase 1 portion of this study is to determine the maximum tolerated dose (MTD) and recommended phase 2 dose (RP2D) of H3B-6545 in women with locally advanced or metastatic estrogen receptor (ER)-positive, human epidermal growth factor 2 (HER2)-negative breast cancer.

The primary purpose of phase 2 portion of this study is to estimate the efficacy of H3B-6545 in terms of best overall response rate, duration of response (DoR), clinical benefit rate (CBR), disease control rate (DCR), progression-free survival (PFS), and overall survival (OS) in all participants with ER-positive, HER2-negative breast cancer and in those with and without ER alpha mutation (including a clonal estrogen receptor 1 gene [ESR1] Y537S mutation).

Primary Purpose
Study Type
Phase I/II


Healthy Volunteers
Minimum Age
18 Years
Maximum Age

Inclusion Criteria:

  • Pre- or post-menopausal women.
  • ER-positive, HER2-negative breast cancer that is advanced or metastatic.
  • Progressed on prior therapy. Multiple prior lines of therapy allowed in Phase 1 and 2. Participants under amendment 6 (or subsequent amendments) must have received prior cyclin-dependent kinase (CDK4/6) inhibitor therapy. Up to one prior chemotherapy in the metastatic setting is allowed.
  • A recent archival tumor tissue obtained within 6 months prior to enrollment or a fresh tumor biopsy must be provided. A second biopsy after initiating trial therapy is not required.
  • Eastern Cooperative Oncology Group (ECOG) performance status (PS) of 0 or 1.
  • Adequate bone marrow and organ function.
  • Participants under amendment 6 (or subsequent amendments) must have measurable disease at baseline as per Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 criteria.
  • Participants under amendment 6 (or subsequent amendments) must have ESR1 Y537S mutation in absence of ESR1 D538G mutation as per the results of a central laboratory from a Nucleic Acids Whole Blood sample.

Exclusion Criteria:

  • Participants must have at least one measurable lesion.
  • Participant with inflammatory breast cancer.
  • Participant has received more than one prior chemotherapy regimen for metastatic disease (Phase 2 only).
  • Females of childbearing potential who are unable or unwilling to follow adequate contraceptive measures.

Join this Trial

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Study Stats
Protocol No.
Shenetra Walker
  • UCLA Burbank
  • UCLA Laguna Hills
  • UCLA Pasadena
  • UCLA Santa Monica
  • UCLA Westlake Village
  • UCLA Westwood
For Providers
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