ESR1

Chr 6ADAR

estrogen receptor 1

Also known as: ER, ESR, ESRA, ESTRR, Era, NR3A1

The estrogen receptor 1 protein functions as a ligand-activated transcription factor that regulates estrogen-responsive genes involved in growth, metabolism, and sexual development. Mutations cause estrogen resistance syndrome with autosomal recessive inheritance, while some variants may contribute to migraine susceptibility with autosomal dominant inheritance. This gene is highly constrained against loss-of-function variation (pLI 0.99, LOEUF 0.19), indicating that complete loss of function is likely incompatible with normal development.

OMIMResearchSummary from RefSeq, OMIM, UniProt
MultiplemechanismAD/ARLOEUF 0.194 OMIM phenotypes
Clinical SummaryESR1
Population Constraint (gnomAD)
Highly constrained gene — heterozygous loss-of-function variants are very rare in the population (pLI 1.00). One damaged copy is likely sufficient to cause disease.
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Clinical Trials
12 active or recruiting trials — potential therapeutic options may be available

Population Genetics & Constraint

gnomAD v4 — loss-of-function & missense intolerance

LoF intolerant — likely haploinsufficient
LoF Constraint
0.19LOEUF
pLI 0.999
Z-score 4.45
OE 0.04 (0.010.19)
Highly constrained

Highly LoF-intolerant (top ~10% of genes)

Missense Constraint
1.61Z-score
OE missense 0.75 (0.680.84)
258 obs / 341.9 exp
Tolerant

Mild missense constraint

Observed / Expected Ratios
LoF OE0.04 (0.010.19)
00.351.4
Missense OE0.75 (0.680.84)
00.61.4
Synonymous OE1.13
01.21.6
LoF obs/exp: 1 / 25.0Missense obs/exp: 258 / 341.9Syn Z: -1.24
DN
0.5181th %ile
GOF
0.4776th %ile
LOF
0.81top 5%

This gene has evidence for multiple mechanisms of pathogenicity (loss-of-function, dominant-negative and gain-of-function). Both the Badonyi & Marsh prediction and the broader genomic evidence point to loss-of-function as the predominant mechanism. Different variants in this gene may act through different mechanisms — interpret in context of the specific variant.

LOFprediction above median · LOEUF 0.19
DN1 literature citation
GOF1 literature citation

Literature Evidence

DNUsing a luciferase assay, we found that mRNA encoding a truncated ESR1 significantly attenuates gene expression at estrogen-response elements demonstrating a dominant negative function.PMID:18424448
GOFIn the past 2 years, several studies unveiled gain-of-function mutations in ESR1, the gene encoding the ER, in approximately 20% of patients with metastatic ER-positive disease who received endocrine therapies, such as tamoxifen and aromatase inhibitors.PMID:26122181

Predictions from Badonyi M, Marsh JA. PLoS ONE. 2024;19(8):e0307312. Mechanism ranking also informed by gnomAD constraint, ClinVar, and ClinGen data.

ClinVar Variant Classifications

0 submitted variants in ClinVar

Protein Context — Lollipop Plot

ESR1 · protein map & ClinVar variants

Showing all ClinVar variants across the protein. Search a specific variant to highlight its position.

3D Protein StructureAlphaFold

Clinical Trials

Active and recruiting trials from ClinicalTrials.gov

ESR1 Gene MutationAdvanced Breast Cancer

Current Status of Treatment for Chinese Patients With ESR1-mutated HR+/HER2-advanced Breast Cancer

RECRUITING
NCT06548919SciClone PharmaceuticalsStarted 2024-08-08
Endocrine therapyChemotherapy Prednisone
Estrogen Receptor NegativeEstrogen Receptor PositiveHER2/Neu Negative

Paclitaxel & Cyclophosphamide With or Without Trastuzumab Before Surgery in Treating Previously Untreated Breast Cancer

ACTIVE NOT RECRUITING
NCT01750073Phase PHASE2University of NebraskaStarted 2012-12-07
CyclophosphamideDoxorubicin HydrochlorideLaboratory Biomarker Analysis
Breast AdenocarcinomaEstrogen Receptor- Negative Breast CancerEstrogen Receptor-positive Breast Cancer

Neoadjuvant Pembrolizumab + Decitabine Followed by Std Neoadj Chemo for Locally Advanced HER2- Breast Ca

ACTIVE NOT RECRUITING
NCT02957968Phase PHASE2Virginia Commonwealth UniversityStarted 2017-01-24
DoxorubicinCyclophosphamidePaclitaxel
Breast CancerTriple Negative Breast Cancer

Use of Imatinib to Convert Triple Negative Breast Cancer Into ER-positive Breast Cancer (I-CONIC)

RECRUITING
NCT05722795Phase NAVastra Gotaland RegionStarted 2023-06-01
Imatinib 400 MG Oral Tablet
Anatomic Stage I Breast Cancer AJCC v8Anatomic Stage II Breast Cancer AJCC v8Anatomic Stage III Breast Cancer AJCC v8

Effect of HSD3B1 (1245C) Gene Mutation on Treatment of Stage I-III Breast Cancer

RECRUITING
NCT05183828Phase PHASE4University of WashingtonStarted 2022-01-23
Biospecimen CollectionLetrozoleQuestionnaire Administration
Breast AdenocarcinomaHormone Receptor PositiveStage IA Breast Cancer AJCC v7

Hormone Therapy With or Without Combination Chemotherapy in Treating Women Who Have Undergone Surgery for Node-Negative Breast Cancer (The TAILORx Trial)

ACTIVE NOT RECRUITING
NCT00310180Phase PHASE3National Cancer Institute (NCI)Started 2006-04-07
AnastrozoleExemestaneLaboratory Biomarker Analysis
Breast Cancer

The T-REX Trial: Tailored Regional External Beam Radiotherapy in Clinically Node-negative Breast Cancer Patients With 1-2 Sentinel Node Macrometastases.

RECRUITING
NCT05634889Phase NARegion SkaneStarted 2023-03-17
De-escalation
Advanced Breast CancerER-positive Breast CancerHER2-negative Breast Cancer

Elacestrant + Everolimus in Patients ER+/HER2-, ESR1mut, Advanced Breast Cancer Progressing to ET and CDK4/6i.

RECRUITING
NCT06382948Phase PHASE3MedSIRStarted 2024-12-05
EverolimusElacestrantPlacebo
Breast Cancer

S1207 Hormone Therapy With or Without Everolimus in Treating Patients With Breast Cancer

ACTIVE NOT RECRUITING
NCT01674140Phase PHASE3SWOG Cancer Research NetworkStarted 2013-09-12
anastrozoleeverolimusexemestane
Breast Cancer

Elacestrant and Exemestane for Patients With Pretreated HR+/HER2- Metastatic Breast Cancer and [18F] FES-avid Lesions (COMBINE)

NOT YET RECRUITING
NCT07395336Phase PHASE2European Institute of OncologyStarted 2026-04
elacestrant and exemestane
Breast Cancer

PErsonalized TREatment of High-risk MAmmary Cancer - the PETREMAC Trial

ACTIVE NOT RECRUITING
NCT02624973Phase PHASE2Haukeland University HospitalStarted 2016-04-15
Neoadjuvant tamoxifen + goserelin (premenopausal women)Neoadjuvant letrozole (postmenopausal women)Neoadjuvant endocrine therapy + palbociclib (if lack of response to endocrine therapy alone)
Breast Atypical HyperplasiaBreast CarcinomaBreast Ductal Carcinoma In Situ

Low Dose Tamoxifen With or Without Omega-3 Fatty Acids for Breast Cancer Risk Reduction

RECRUITING
NCT06195306Phase PHASE2National Cancer Institute (NCI)Started 2025-07-28
Biospecimen CollectionMammographyOmega-3-Acid Ethyl Esters
Clinical Literature
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