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A Phase 2 Bridging Study of Elacestrant Monotherapy in Advanced or Metastatic Breast Cancer

A Phase 2 Open-Label, Single-Arm, Multicenter Trial to Evaluate the Efficacy and Safety of Elacestrant Monotherapy for the Treatment of Japanese Participants With ER+/HER2- Advanced or Metastatic Breast Cancer With ESR1-mutation Following CDK4/6 Inhibitor Therapy

Status
Recruiting
Phases
Phase 2
Study type
Interventional
Source
ClinicalTrials.gov
Registry ID
NCT07766018
Enrollment
70
Registered
2026-08-14
Start date
2026-08-18
Completion date
2028-10-01
Last updated
2026-09-10

For informational purposes only — not medical advice. Sourced from public registries and may not reflect the latest updates. Terms

Conditions

Breast Cancer

Keywords

Elacestrant, Bridging Study, Japan, ESR1-mutation, Breast Cancer, CDK4/6i

Brief summary

This is a multicenter, open-label, Phase 2 bridging study to evaluate the efficacy and safety of elacestrant in Japanese post-menopausal women and men with estrogen receptor positive (ER+)/human epidermal growth factor receptor 2 negative (HER2-) advanced or metastatic breast cancer with estrogen receptor 1 gene mutation (ESR1-mut) whose disease has relapsed or progressed on at least 1 and no more than 2 prior lines of endocrine therapy for metastatic breast cancer, which must have included cyclin-dependent kinase 4/6 inhibitor (CDK4/6i) therapy in combination with fulvestrant or an aromatase inhibitor.

Interventions

DRUGElacestrant

Administered as an oral tablet

Sponsors

Stemline Therapeutics, Inc.
Lead SponsorINDUSTRY

Study design

Allocation
NA
Intervention model
SINGLE_GROUP
Primary purpose
TREATMENT
Masking
NONE

Eligibility

Sex/Gender
ALL
Age
18 Years to No maximum
Healthy volunteers
No

Inclusion criteria

Key Inclusion Criteria: * Must have a histologically or cytologically proven diagnosis of adenocarcinoma of the breast with evidence of either locally advanced disease not amenable to resection or radiation therapy with curative intent or metastatic disease not amenable to curative therapy * Female participants must be post-menopausal (as defined by the protocol) * Must have ER+ and HER2- tumor status confirmed per local laboratory testing * Participants must be ESR1-mutant positive determined via testing with the Guardant360 Companion Diagnostic panel test prior to enrollment * Must have disease progression during or within 28 days of completion of prior treatment with a CDK4/6 inhibitor in combination with either fulvestrant or an aromatase inhibitor (this counts as a line of prior endocrine therapy) for metastatic breast cancer Key

Exclusion criteria

* Prior treatment with: elacestrant or investigational or approved selective estrogen receptor degrader or ER antagonist; antibody-drug conjugate therapy for advanced/metastatic breast cancer; anti-cancer or investigational drug treatment * Radiation therapy within 14 days (28 days for brain lesions) before the first dose of study drug * Intact uterus with a history of endometrial intraepithelial neoplasia (atypical endometrial hyperplasia or higher-grade lesion) * Diagnosis of any other malignancy within 5 years before enrollment, except for adequately treated basal cell or squamous cell skin cancer, carcinoma in situ of the cervix, or second primary breast cancer Note: Other protocol-defined inclusion/

Design outcomes

Primary

MeasureTime frame
Progression-free Survival as Assessed by the Imaging Review CommitteeUp to approximately 27 months

Secondary

MeasureTime frame
Number of Participants with Adverse EventsUp to approximately 27 months
Plasma Concentration of ElacestrantUp to approximately 27 months
Progression-free Survival as Assessed by the InvestigatorUp to approximately 27 months
Overall SurvivalUp to approximately 27 months

Countries

Japan

Contacts

CONTACTStemline Trials
clinicaltrials@menarinistemline.com1-877-332-7961
STUDY_DIRECTORMedical Director

Stemline Therapeutics, Inc.

Outcome results

None listed

Source: ClinicalTrials.gov · Data processed: Sep 11, 2026