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AZD9833

Phase 3

ER-Positive HER2-Negative Breast Cancer | Small molecule | Oncology |AstraZeneca PLC|Last Updated: Aug 26, 2026

Success Probability

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Market & Valuation

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Trial Design

RandomizedDouble-BlindACTIVE_CONTROLLEDDMC
Total Trials2
Total Enrollment1,685

FDA Designations

No designations recorded

Clinical trial landscape

AZD9833 · 9 trials · 7 indications

Phase 3 2Phase 2 2Phase 1 5
NCT04964934Phase III Study to Assess AZD9833+ CDK4/6 Inhibitor in HR+/HER2-MBC With Detectable ESR1m Before Progression (SERENA-6)ER-Positive HER2-Negative Breast Cancer
ACTIVE NOT_RECRUITING315 Analytics
NCT04711252A Comparative Study of AZD9833 Plus Palbociclib Versus Anastrozole Plus Palbociclib in Patients With ER-Positive HER2 Negative Breast Cancer Who Have Not Received Any Systemic Treatment for Advanced DiseaseER-Positive HER2-Negative Breast Cancer
ACTIVE NOT_RECRUITING1,370 Analytics
PHASE3ACTIVE NOT_RECRUITING
Phase III Study to Assess AZD9833+ CDK4/6 Inhibitor in HR+/HER2-MBC With Detectable ESR1m Before Progression (SERENA-6)
ER-Positive HER2-Negative Breast CancerUnlock trial analytics
PHASE3ACTIVE NOT_RECRUITING
A Comparative Study of AZD9833 Plus Palbociclib Versus Anastrozole Plus Palbociclib in Patients With ER-Positive HER2 Negative Breast Cancer Who Have Not Received Any Systemic Treatment for Advanced Disease
ER-Positive HER2-Negative Breast CancerUnlock trial analytics

Study Endpoints

Primary Endpoints

Progression-free survival (PFS) assessed by the Investigator as defined by response evaluation criteria in solid tumors (RECIST version 1.1)
From randomization until the earlier of the progression event or death (approximately 2 years)

PFS is defined as the time from randomization to objective disease progression (as assessed by RECIST 1.1) or death.

Progression-free survival (PFS) assessed by the Investigator as defined by response evaluation criteria in solid tumors (RECIST) version 1.1
From randomization until progression per RECIST 1.1 as assessed by the investigator at local site or death due to any cause (up to 5 years)

PFS is defined as the time from randomization to objective disease progression (as assessed by RECIST) or death.

Percentage Change From Baseline in Estrogen Receptor (ER) Expression Between Pre- and On-treatment Tumour Samples (Primary Analysis)
Baseline (Screening Day -21 to 1) to Biopsy day (Days 5-7 [Stage 1 and 2] or Days 12-15 [Stage 3])

The pharmacodynamic (PD) effect of AZD9833 on ER expression comparing pre- and on-treatment tumour samples in women with early breast cancer after 5 to 7 days and 12 to 15 days of AZD9833 treatment was assessed. The assessment was done by immunohistochemistry (IHC) method. The percentage change was calculated from an analysis of covariance (ANCVOA) model adjusting for baseline ER score and day of on-treatment biopsy.

Percentage Change From Baseline in ER Expression Between Pre- and On-treatment Tumour Samples (Sensitivity Analysis)
Baseline (Screening Day -21 to 1) to Biopsy Day (Days 5-7 [Stage 1 and 2] or Days 12-15 [Stage 3])

The PD effect of AZD9833 on ER expression comparing pre- and on-treatment tumour samples in women with early breast cancer after 5 to 7 days and 12 to 15 days of AZD9833 treatment was assessed. The assessment was done by IHC method. The sensitivity analysis excluded any patients who were HER2-positive patient by central assessment as well as patients with baseline ER H-score \< 10. The percentage change was calculated from ANCVOA model adjusting for baseline ER score and day of on-treatment biopsy.

Progression-free Survival (PFS)
From date of randomisation to date of objective disease progression (or last evaluable assessment in the absence of progression) or death (up to data cut-off of 29 months)

PFS was assessed by the Investigator as defined by response evaluation criteria in solid tumors (RECIST) version 1.1. PFS was defined as the time from randomisation until the date of objective disease progression or death (by any cause in the absence of progression) regardless of whether the patient withdraws from randomised therapy or received another anti-cancer therapy prior to progression. Disease progression was defined as ≥20% increase in the sum of diameters of target lesions, unequivocal progression in non-target lesions, and/or appearance of new lesions. Data from the 300mg arm should be interpreted with caution as recruitment to the 300mg arm was stopped early at 20 patients randomised and therefore the 300mg data is highly variable.

Area under plasma concentration time curve from zero to infinity (AUCinf) of midazolam, omeprazole, total dabigatran, and celecoxib
For Arm A: Day 1 to Day 2 (Period 1 and 3); For Arm B: Day 1 to Day 3 (Period 1 and 2) (Each Period is 4 days); For Arm C: Day 1 to Day 4 (Period 1 and 3) (For Arm A and C, Period 1 is for 5 days and Period 3 is for 4 days)

The effects of AZD9833 will be evaluated in healthy postmenopausal female participants on the key pharmacokinetic (PK) variables of: - single-dose midazolam and omeprazole, administered together * single-dose dabigatran etexilate * single-dose celecoxib

Area under the plasma concentration curve from zero to the last quantifiable concentration (AUClast) of midazolam, omeprazole, total dabigatran, and celecoxib
For Arm A: Day 1 to Day 2 (Period 1 and 3); For Arm B: Day 1 to Day 3 (Period 1 and 2) (Each Period is 4 days); For Arm C: Day 1 to Day 4 (Period 1 and 3) (For Arm A and C, Period 1 is for 5 days and Period 3 is for 4 days)

The effects of AZD9833 will be evaluated in healthy postmenopausal female participants on the key pharmacokinetic variables of: * single-dose midazolam and omeprazole, administered together * single-dose dabigatran etexilate * single-dose celecoxib

Maximum observed plasma concentration (Cmax) of midazolam, omeprazole, dabigatran etexilate and celecoxib
For Arm A: Day 1 to Day 2 (Period 1 and 3); For Arm B: Day 1 to Day 3 (Period 1 and 2) (Each Period is 4 days); For Arm C: Day 1 to Day 4 (Period 1 and 3) (For Arm A and C, Period 1 is for 5 days and Period 3 is for 4 days)

The effects of AZD9833 will be evaluated in healthy postmenopausal female participants on the key pharmacokinetic variables of: * single-dose midazolam and omeprazole administered together * single-dose dabigatran etexilate * single-dose celecoxib

The cumulative amount of AZD9833 excreted (CumAe)
Urine and faecal samples collected from pre-dose until 168 hours post-dose

Assessment of the total radioactivity by measuring the cumulative amount of AZD9833 excreted

The cumulative amount of AZD9833 excreted, expressed as a percentage of the radioactive dose administered (Cum%Ae)
Urine and faecal samples collected from pre-dose until 168 hours post-dose

Assessment of the total radioactivity, expressed as a percentage, by measuring the cumulative amount of AZD9833 excreted

Assessment of metabolites in plasma by liquid chromatography-radiochemical-detection and subsequent mass spectrometry
Plasma samples collected from pre-dose until 168 hours post-dose
Assessment of metabolites in urine by liquid chromatography-radiochemical-detection and subsequent mass spectrometry
Urine samples collected from pre-dose until 168 hours post-dose
Assessment of metabolites in faeces by liquid chromatography-radiochemical-detection and subsequent mass spectrometry
Faeces samples collected from pre-dose until 168 hours post-dose
The number of subjects with dose-limiting toxicity, as defined in the protocol.
Minimum observation period 28 days on treatment.

Dose-limiting toxicity as described in the protocol that is not related to disease progression, intercurrent illness or concomitant medications and that, despite optimal therapeutic intervention, meets protocol-defined criteria of AZD9833 monotherapy. \[part A only\]

The number of subjects with treatment-related adverse events as assessed by CTCAE v5.0.
6 months after the last patient recruited starts study intervention or 28 days after the final patient discontinues study intervention

Data will include clinical observations, ECG parameters, clinical chemistry and haematology and vital signs assessed as the number of subjects with treatment-related adverse events assessed by CTCAE v5.0 of AZD9833 monotherapy.

Plasma AZD9833 concentrations and derived PK parameters.
At predefined intervals throughout the AZD9833 treatment period (approximately 16 weeks )

To characterise the single- and multiple-dose PK of AZD9833 monotherapy.

The number of subjects with treatment-related adverse events as assessed by CTCAE v4.03.
Minimum observation period 28 days on treatment, and will continue until the subject is off the study (approximately 1 year).

Data will include clinical observations, ECG parameters, clinical chemistry and haematology and vital signs assessed as the number of subjects with treatment-related adverse events assessed by CTCAE v4.03.

Secondary Endpoints

Progression-free survival 2 (PFS2)
From randomization to the earliest of the progression event (following the initial progression), subsequent to first subsequent therapy or death (approximately 3.5 years)
Overall survival (OS)
From randomization until the date of death due to any cause (approximately 5 years)
Chemotherapy free survival
From randomization until the earlier of the start date of chemotherapy or death due to any cause (approximately 5 years)
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Study Design & Arms

AllocationRANDOMIZED
MaskingTRIPLE
ModelPARALLEL
PurposeTREATMENT

Treatment Arms

ArmTypeDescription
AZD9833 + palbociclib, abemaciclib or ribociclibEXPERIMENTALThe patients will receive AZD9833 (75 mg, PO, once daily) + palbociclib (PO, once daily, 125, 100 or 75 mg for 21 consecutive days followed by 7 days off treatment), abemaciclib (PO, twice daily, 150,100 or 50 mg) or ribociclib (To Be Determined, PO, once daily for 21 consecutive days followed by 7 days off treatment) + anastrozole placebo (PO, once daily) or letrozole placebo (PO, once daily)
Anastrozole or letrozole + palbociclib, abemaciclib or ribociclibACTIVE_COMPARATORThe patients will recieve anastrozole (1 mg, PO, once daily) or letrozole (2.5 mg, PO, once daily) + palbociclib (PO, once daily, 125, 100 or 75 mg for 21 consecutive days followed by 7 days off treatment), abemaciclib (PO, twice daily, 150, 100 or 50 mg) or ribociclib (To Be Determined, PO, once daily for 21 consecutive days followed by 7 days off treatment) + AZD9833 placebo (PO, once daily)
AZD9833 + palbociclibEXPERIMENTALThe patients will receive AZD9833 (75 mg, PO, once daily) + palbociclib (PO, once daily, 125 mg for 21 consecutive days followed by 7 days off treatment) + anastrozole placebo (1 mg, PO, once daily)
Anastrozole + palbociclibACTIVE_COMPARATORThe patients will recieve Anastrozole (1 mg, PO, once daily) + palbociclib (PO, once daily, 125 mg for 21 consecutive days followed by 7 days off treatment) + AZD9833 placebo (PO, once daily)
Stage 1: AZD9833 Dose AEXPERIMENTALPost-menopausal participants will receive once daily oral dose A of AZD9833 in stage 1 of the study.
Stage 1: AZD9833 Dose BEXPERIMENTALPost-menopausal participants will receive once daily oral dose B of AZD9833 in stage 1 of the study.
Stage 2: AZD9833 Dose AEXPERIMENTALPost-menopausal participants will receive once daily oral dose A of AZD9833 in stage 2 of the study.
Stage 2: AZD9833 Dose BEXPERIMENTALPost-menopausal participants will receive once daily oral dose B of AZD9833 in stage 2 of the study.
Stage 2: AZD9833 Dose CEXPERIMENTALPost-menopausal participants will receive once daily oral dose C of AZD9833 in stage 2 of the study.
Stage 3: AZD9833 Dose AEXPERIMENTALPost-menopausal participants will receive once daily oral dose A of AZD9833 in stage 3 of the study.
Stage 3: AZD9833: Dose BEXPERIMENTALPost-menopausal participants will receive once daily oral dose B of AZD9833 in stage 3 of the study.
AZD9833 Dose AEXPERIMENTALThe patients will receive AZD9833 (Dose A).
AZD9833 Dose BEXPERIMENTALThe patients will receive AZD9833 (Dose B).
AZD9833 Dose CEXPERIMENTALThe patients will receive AZD9833 (Dose C).
Fulvestrant 500 mgACTIVE_COMPARATORThe patients will receive Fulvestrant (500 mg).
Arm A (midazolam and omeprazole)EXPERIMENTALParticipants will receive single oral doses of midazolam and omeprazole together (Day 1 of Treatment Periods 1 and 3) and repeated doses of AZD9833 (Days 1 to 5 of Treatment Period 2 and Day 1 of Treatment Period 3)
Arm B (Dabigatran etexilate)EXPERIMENTALParticipants will receive single oral doses of dabigatran etexilate (Day 1 of Treatment Periods 1 and 2) and single oral dose of AZD9833 (Day 1 of Treatment Period 2)
Arm C (Celecoxib)EXPERIMENTALParticipants will receive single oral doses of celecoxib (Day 1 of Treatment Periods 1 and 3) and repeated oral doses of AZD9833 (Days 1 to 5 of Treatment Period 2 and Day 1 of Treatment Period 3)
[14C]AZD9833 (D8532C00005)EXPERIMENTALOral Solution, 75 mg (NMT 0.67 MBq)
AZD9833 monotherapy dose escalationEXPERIMENTAL -
AZD9833 monotherapy dose expansionEXPERIMENTAL -
AZD9833 with palbociclib dose expansionEXPERIMENTAL -
AZD9833 with everolimus dose expansionEXPERIMENTAL -
AZD9833 monotherapyEXPERIMENTALDose escalation of AZD9833 monotherapy for patients with ER+ HER2- advanced breast cancer
AZD9833 with palbociclib dose escalationEXPERIMENTAL -
AZD9833 with everolimus dose escalationEXPERIMENTAL -
AZD9833 with abemaciclib (± anastrozole) dose escalationEXPERIMENTAL -
AZD9833 with abemaciclib (± anastrozole)dose expansionEXPERIMENTAL -
AZD9833 with capivasertib dose escalationEXPERIMENTAL -
AZD9833 with capivasertib dose expansionEXPERIMENTAL -
AZD9833 with ribociclib (± anastrozole) dose escalationEXPERIMENTAL -
AZD9833 with ribociclib (± anastrozole) dose expansionEXPERIMENTAL -
AZD9833 with anastrozole dose escalationEXPERIMENTAL -
AZD9833 with anastrozole dose expansionEXPERIMENTAL -

Interventions

NameTypeDescription
AZD9833DRUGDosage formulation: AZD9833 tablets will be administered orally
AZD9833 PlaceboDRUGDosage formulation: AZD9833 placebo tablets will be administrated orally.
AnastrozoleDRUGDosage formulation: anastrozole tablets will be administered orally.
Anastrozole placeboDRUGDosage formulation: anastrozole placebo tablets will be administrated orally.
LetrozoleDRUGDosage formulation: letrozole tablets will be administered orally.
Letrozole placeboDRUGDosage formulation: letrozole placebo tablets will be administered orally.
PalbociclibDRUGDosage formulation: palbociclib tablets/capsules will be administered orally
AbemaciclibDRUGDosage formulation: abemaciclib tablets will be administered orally
Luteinizing hormone-releasing hormone (LHRH) agonistDRUGMen (when medically applicable) and pre- or peri-menopausal women are required to receive a monthly LHRH agonist.
RibociclibDRUGDosage formulation: ribociclib tablets will be administered orally
FulvestrantDRUGDosage formulation: Fulvestrant will be administered via intramuscular (IM) injection.
MidazolamDRUGMidazolam will be administered orally as a syrup once on Day 1 of Treatment Periods 1 and 3; administered together with Omeprazole
OmeprazoleDRUGAn Omeprazole capsule will be administered once on Day 1 of Treatment Periods 1 and 3; administered together with Midazolam
Dabigatran EtexilateDRUGA Dabigatran Etexilate capsule will be administered once on Day 1 of Treatment Periods 1 and 2
CelecoxibDRUGA Celecoxib capsule will be administered once on Day 1 of Treatment Periods 1 and 3
[14C]AZD9833 Oral Solution, 75 mgDRUGOral Solution, 75 mg (NMT 0.67 MBq) - oral, fasted
AZD9833 with palbociclibDRUGPart B: AZD9833 with palbociclib dose expansion
AZD9833 with everolimusDRUGPart B: AZD9833 with everolimus dose expansion
AZD9833 with abemaciclibDRUGPart G: AZD9833 in combination with abemaciclib (± anastrozole) dose escalation
AZD9833 with capivasertibDRUGPart I: AZD9833 in combination with capivasertib dose escalation
AZD9833 with ribociclibDRUGPart K: AZD9833 in combination with ribociclib (± anastrozole) dose escalation
AZD9833 with anastrozoleDRUGPart M: AZD9833 in combination with anastrozole dose escalation
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Eligibility Criteria

Age Range18 Years to 130 Years
SexALL
Healthy VolunteersNo
Study Sites264

INCLUSION CRITERIA: INFORMATION FOR TRIAL PARTICIPANTS - Participants can join the trial if they: * Have advanced breast cancer that is not able to be treated with surgery or radiation; * Have an ESR1 mutation in their cancer; * Have breast cancer that is HR-positive and HER2-negative; * Are curre...

Countries:United StatesAustraliaAustriaBelgiumBulgariaCanadaFranceGermanyHungaryIsraelItalyJapanNorwayPolandPortugalRussiaSlovakiaSouth KoreaSpainSwitzerlandTaiwanTurkey (Türkiye)United KingdomChileChinaCzechiaIndiaMalaysiaMexicoGeorgiaUkraine
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Recent Changes (Last 90 Days)

LOWAug 26, 2026NCT04214288lastUpdatePostDate: changed
LOWAug 26, 2026NCT04214288lastUpdatePostDate: changed
LOWAug 19, 2026NCT03616587lastUpdatePostDate: changed
LOWAug 19, 2026NCT03616587lastUpdatePostDate: changed
LOWAug 19, 2026NCT03616587lastUpdatePostDate: changed
LOWJul 14, 2026NCT04964934lastUpdatePostDate: changed
LOWJul 14, 2026NCT04964934lastUpdatePostDate: changed
MEDIUMJun 16, 2026NCT04214288Completion: 2026-03-17 → 2027-06-16
MEDIUMJun 16, 2026NCT04214288Completion: 2026-03-17 → 2027-06-16
MEDIUMJun 16, 2026NCT04214288Completion: 2026-03-17 → 2027-06-16
MEDIUMJun 16, 2026NCT04214288Completion: 2026-03-17 → 2027-06-16

Frequently asked questions about AZD9833

What is AZD9833 used for?

AZD9833 is an investigational small molecule being studied for the treatment of ER-positive, HER2-negative advanced or metastatic breast cancer in postmenopausal women. It is also being evaluated in healthy volunteers for drug interaction studies. The drug is in clinical development and has not been approved by regulatory authorities.

Who makes AZD9833?

AZD9833 is being developed by AstraZeneca PLC, a biopharmaceutical company traded on the NASDAQ under the ticker symbol AZN. The company is conducting clinical trials of AZD9833 in multiple countries, including the United States, Spain, the United Kingdom, Japan, and others.

What phase is AZD9833 in?

AZD9833 is in Phase 2 clinical development for advanced ER-positive HER2-negative breast cancer. It is also being studied in Phase 1 trials. The drug is investigational and has not received FDA approval. Clinical trials are active but not recruiting participants.

What clinical trials is AZD9833 in?

AZD9833 is being studied in several clinical trials. NCT03616587 is a Phase 1 study of AZD9833 alone or in combination in women with advanced breast cancer. NCT04214288 is a Phase 2 trial comparing oral AZD9833 with intramuscular fulvestrant in postmenopausal women with advanced ER-positive HER2-negative breast cancer. NCT04541433 is a completed Phase 1 study in Japanese women, and NCT05438303 is a completed drug interaction study in healthy volunteers.

How does AZD9833 work?

AZD9833 is a small molecule designed to target the estrogen receptor in ER-positive breast cancer cells. By interacting with this receptor, it aims to inhibit estrogen-driven tumor growth. The drug is being developed as an oral therapy for patients with ER-positive, HER2-negative advanced breast cancer.

Is AZD9833 the same as fulvestrant?

No, AZD9833 is not the same as fulvestrant. Fulvestrant is an intramuscularly administered estrogen receptor degrader used as a comparator in a Phase 2 clinical trial of AZD9833. AZD9833 is an oral investigational drug being studied as a potential alternative treatment for advanced ER-positive HER2-negative breast cancer.