A Phase 2 interventional study of Endocrine Therapy and a CDK 4/6 inhibitor and Endocrine Therapy and a CDK 4/6 inhibitor in Breast Cancer, sponsored by Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins. Active, not recruiting at 1 site in United States. Open to participants aged 18 Years to 100 Years. Per ClinicalTrials.gov, last updated 2026-08-07.
Sponsored by Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins · Phase 2, Interventional, and Treatment
The goal of this research study is to determine if the investigators can predict which participants will respond to endocrine therapy and a cyclin-dependent kinases 4 and 6 (CDK4/6) inhibitor for metastatic breast cancer and which participants will not. Investigators will use information from the tumor tissue and serial blood samples. Investigators hope that a deeper understanding of which participants will respond to this combination and how resistance emerges will allow the investigators to better tailor therapies for metastatic breast cancer.
Subjects will have archived tissue or new biopsy collected at study enrollment. This tissue will undergo special molecular testing. Subjects will also have blood collected at study enrollment and periodically thereafter. This blood will also undergo special molecular testing. Information from this testing will not be available to subjects or their treating physicians as the investigators do not know how this information should impact treatment.
The investigators will collect information about which treatment the subjects receive and how their cancer responds.
Any man or woman being seen at Johns Hopkins for treatment of newly diagnosed estrogen receptor positive (ER+) and/or progesterone receptor positive (PR+) metastatic breast cancer may be eligible.
Resistance to endocrine therapy (ET) invariably develops in patients with estrogen and/or progesterone receptor (ER/ PR) positive metastatic breast cancer (MBC). Data regarding primary resistance and patterns of emergence of acquired resistance in patients treated with endocrine therapy (ET) and cyclin dependent kinase 4 and 6 (CDK4/6) inhibitors are limited. Understanding these mechanisms could result in improved selection of treatment options and provide new targets for therapy development. In this study, we aim to identify and characterize determinants of intrinsic and acquired resistance to endocrine therapy in patients with hormone receptor (HR) positive, human epidermal growth factor receptor 2 (HER2) negative MBC treated with the combination of endocrine therapy (aromatase inhibitor or fulvestrant) and a CDK4/6 inhibitor.
Investigators will determine the prevalence of genomic alterations at baseline in the primary tumor, metastatic tissue and plasma tumor DNA (ptDNA), including in the gene encoding estrogen receptor- alpha (ESR1). The mutational tumor burden in the primary tumor, metastatic tumor and blood will be assessed. Blood samples will be collected at several time points, allowing the detection of changes in molecular markers over time. We will further characterize tissue markers associated with progression and duration of response by evaluating these markers in available tissue obtained at progression. Investigators goal is to evaluate the prevalence and role of known alterations determining endocrine resistance in patients with metastatic disease, as knowledge regarding this population remains limited.The investigators also hope to unveil novel markers of endocrine resistance.
Exclusion Criteria:
Participants will undergo blood collection (intervention) at time of initiating treatment with endocrine therapy and palbociclib, at 4 weeks after initiating this treatment, and every 3-4 months while on treatment. If a participant progresses on this treatment, they will have a blood collection at that time.
Drug: Endocrine Therapy and a CDK 4/6 inhibitor
Participants will undergo blood collection (intervention) at time of initiating treatment with endocrine therapy and palbociclib, at 4 weeks after initiating this treatment, and every 3-4 months while on treatment. If a participant progresses on this treatment, they will have a blood collection at that time.
Drug: Endocrine Therapy and a CDK 4/6 inhibitor
Participants with untreated metastatic disease receiving ET and a CDK 4/6 i as first line therapy.
Also known as: ET and CDK4/6i
Participants initiating a CDK 4/6 i after progression on ET.
Also known as: ET and CDK4/6i
Genetic Mutation
The number of participants who have an ESR1 mutation prior to receiving endocrine therapy and palbociclib.
Time frame: 2 years
Genetic Mutation
The amount of time from receiving palbociclib and endocrine therapy to the first detectable ESR1 mutation
Time frame: 4 years
Genetic Mutation
Percentage of participants with an ESR1 mutation at the time of progression for those who received treatment with endocrine therapy and palbociclib.
Time frame: 3 years
Plan to share: No
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This study is active, not recruiting, as verified in Aug 2026. You cannot join it, but the record below documents what was studied.
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Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins