A Phase 1/2 interventional study of AVZO-021 and Fulvestrant in HR+/HER2- Breast Cancer and HR+, HER2-, Advanced Breast Cancer, sponsored by Avenzo Therapeutics, Inc.. Recruiting at 16 sites in United States. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-08-10.
Sponsored by Avenzo Therapeutics, Inc. · Phase 1/2, Interventional, and Treatment
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This study, the first clinical trial of AVZO-023, aims to determine the safety, tolerability, pharmacokinetics (PK), pharmacodynamics, maximum tolerated dose, and anti-tumor effects of AVZO-023 in patients with advanced solid tumors. AVZO-023 is an oral medication that inhibits cyclin-dependent kinase 4 (CDK4).
AVZO-023 is an oral, potent, and selective inhibitor of CDK4. AVZO-021 is an oral, potent, and selective inhibitor of CDK2 that is currently being investigated in a global Phase 1/2 study in patients with advanced hormone receptive positive (HR+)/human epidermal growth factor receptor 2 negative (HER2-) breast cancer (NCT05867251).
In Phase 1, the safety and tolerability of AVZO-023 in patients with HR+/HER2- locally advanced or metastatic breast cancer (mBC) will be assessed. The goal of Phase 1 is to determine the MTD/preliminary RP2D of AVZO-023 for use as monotherapy and in combination with AVZO-021 with or without endocrine therapy (ET).
Phase 2 will assess the antitumor activity and confirm the RP2D of AVZO-023 in combination therapy in patients with HR+/HER2- locally advanced or mBC.
14,832 studies on the registry are indexed under Breast Neoplasms; 3,320 are open to participants now.
This study's planned enrollment of 380 is above the median of 72 across 10,903 interventional studies indexed under Breast Neoplasms.
Browse Breast Neoplasms studies →Avenzo Therapeutics, Inc. is the lead sponsor of 4 studies on the registry; 4 are open to participants now.
Counted across the registry records on this site, refreshed daily.
Key Inclusion Criteria:
Key Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
A scale of how much an illness limits everyday activity. For people being assessed to join a study, scores run from 0 (fully active) to 4; lower is more active.
Studies most often ask for 0–1 or 0–2. Your doctor gives the score; the WHO scale uses the same steps. The full scale also has 5, which records death.
The study doctor’s estimate of how long someone is likely to live. Criteria use it so that people can stay in the study long enough for it to answer its question.
The diagnosis was confirmed by looking at a sample under a microscope: tissue from a biopsy or surgery (histology), or cells from a fluid or needle sample (cytology).
Your pathology report is the document that shows this.
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
The amount of disease can be tracked with a defined measurement, so the study can see whether it shrinks or grows. It might be a tumour measured on a scan or, in some blood cancers such as myeloma, a marker measured in blood or urine.
The criteria or the study team say which measurement counts — having no tumour visible on a scan does not by itself rule you out.
The standard rules for measuring tumours on CT or MRI scans, to tell whether a cancer is shrinking, stable or growing during treatment.
“Measurable disease per RECIST 1.1” usually means at least one tumour 10 mm or more at its longest on a CT scan, or a lymph node 15 mm or more across its short axis.
A biopsy takes a small piece of tissue to examine. “Archival tissue” is a sample already taken, for example at diagnosis, and kept by the hospital.
Whether a stored sample will do depends on when it was taken, how much there is and what the study needs. Ask whether the study accepts your stored sample or needs a new biopsy.
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Cancer deposits in the brain from a cancer that started elsewhere in the body (CNS metastases include the spinal cord).
Studies differ: some leave out any brain metastases, some accept ones treated and stable for some weeks. Check what this study allows.
Cancer that has spread from where it began to other parts of the body. “Metastatic” cancer is cancer that has spread this way.
Cancer that has spread to the leptomeninges, the thin layers covering the brain and spinal cord, and the fluid between them. It is not the same as brain metastases.
Criteria often treat it separately, and many studies leave it out even where treated brain metastases are allowed.
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
CYP3A is a group of enzymes, mainly CYP3A4, in the liver and gut that break down many medicines. Some medicines, supplements and foods (grapefruit, St John’s wort) slow them down or speed them up, which changes how much of a study drug stays in the body.
Studies list them so they can be avoided or switched; bring a list of everything you take, including supplements.
The US National Cancer Institute’s scale of how severe an adverse event is — any unwanted medical event during a study, such as a symptom, an illness or an abnormal test result, whether or not a treatment caused it. Whether it did is judged separately.
“Side effects of earlier treatment resolved to grade 1 or less” means they have settled to mild or gone.
ECOG performance status
A scale of how much an illness limits everyday activity. For people being assessed to join a study, scores run from 0 (fully active) to 4; lower is more active.
Studies most often ask for 0–1 or 0–2. Your doctor gives the score; the WHO scale uses the same steps. The full scale also has 5, which records death.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Life expectancy
The study doctor’s estimate of how long someone is likely to live. Criteria use it so that people can stay in the study long enough for it to answer its question.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Histologically or cytologically confirmed
The diagnosis was confirmed by looking at a sample under a microscope: tissue from a biopsy or surgery (histology), or cells from a fluid or needle sample (cytology).
Your pathology report is the document that shows this.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Cancer (malignancy)
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Measurable disease
The amount of disease can be tracked with a defined measurement, so the study can see whether it shrinks or grows. It might be a tumour measured on a scan or, in some blood cancers such as myeloma, a marker measured in blood or urine.
The criteria or the study team say which measurement counts — having no tumour visible on a scan does not by itself rule you out.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
RECIST
The standard rules for measuring tumours on CT or MRI scans, to tell whether a cancer is shrinking, stable or growing during treatment.
“Measurable disease per RECIST 1.1” usually means at least one tumour 10 mm or more at its longest on a CT scan, or a lymph node 15 mm or more across its short axis.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Biopsy and archival tissue
A biopsy takes a small piece of tissue to examine. “Archival tissue” is a sample already taken, for example at diagnosis, and kept by the hospital.
Whether a stored sample will do depends on when it was taken, how much there is and what the study needs. Ask whether the study accepts your stored sample or needs a new biopsy.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Investigational drug or device
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Brain metastases
Cancer deposits in the brain from a cancer that started elsewhere in the body (CNS metastases include the spinal cord).
Studies differ: some leave out any brain metastases, some accept ones treated and stable for some weeks. Check what this study allows.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Metastases
Cancer that has spread from where it began to other parts of the body. “Metastatic” cancer is cancer that has spread this way.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Leptomeningeal disease
Cancer that has spread to the leptomeninges, the thin layers covering the brain and spinal cord, and the fluid between them. It is not the same as brain metastases.
Criteria often treat it separately, and many studies leave it out even where treated brain metastases are allowed.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Corticosteroids (steroids)
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
CYP3A (CYP3A4) inhibitors and inducers
CYP3A is a group of enzymes, mainly CYP3A4, in the liver and gut that break down many medicines. Some medicines, supplements and foods (grapefruit, St John’s wort) slow them down or speed them up, which changes how much of a study drug stays in the body.
Studies list them so they can be avoided or switched; bring a list of everything you take, including supplements.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
CTCAE grade
The US National Cancer Institute’s scale of how severe an adverse event is — any unwanted medical event during a study, such as a symptom, an illness or an abnormal test result, whether or not a treatment caused it. Whether it did is judged separately.
“Side effects of earlier treatment resolved to grade 1 or less” means they have settled to mild or gone.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Escalating doses of twice daily, oral AVZO-023 in 28-day cycles, with addition of fulvestrant
Drug: Fulvestrant · Drug: AVZO-023
Escalating doses of twice daily, oral AVZO-023 in combination with once daily, oral AVZO-021 in 28-day cycles, with addition of fulvestrant
Drug: AVZO-021 · Drug: Fulvestrant · Drug: AVZO-023
Escalating doses of twice daily, oral AVZO-023 in combination with once daily, oral AVZO-021, with once daily, oral letrozole in 28-day cycles
Drug: AVZO-021 · Drug: Letrozole · Drug: AVZO-023
Oral doses of AVZO-023 in 28-day cycles at the RP2D determined in Part 1B/1C, in combination with: 2A) letrozole 2B) fulvestrant 2C) AVZO-021 plus fulvestrant 2D) AVZO-021 plus letrozole
Drug: AVZO-021 · Drug: Fulvestrant · Drug: Letrozole · Drug: AVZO-023
AVZO-021 is an oral selective CDK2 inhibitor
Antineoplastic agent, estrogen receptor antagonist
Also known as: Faslodex
Antineoplastic agent, aromatase inhibitor
Also known as: Femara
AVZO-023 is an oral selective CDK4 inhibitor
Occurrence of Dose Limiting Toxicities (DLTs) during the first cycle (Phase 1)
Number of participants with DLTs assessed for severity using CTCAE v5.0 criteria will be summarized by dose level.
Time frame: Cycle 1 (28 Days)
Number of Participants with Treatment Emergent Adverse Events (TEAEs) and lab abnormalities (Phase 1)
Time frame: From baseline until end of study treatment or study completion (approximately 2 years)
Determine the Maximum Tolerated Dose (MTD) and/or Recommended Phase 2 Dose (RP2D) (Phase 1)
Time frame: Approximately 16 months
Objective Response Rate (ORR) (Phase 2)
Defined as the proportion of patients with a confirmed Complete Response (CR) or Partial Response (PR), as determined by the investigator by radiographic disease assessment according to RECIST v1.1.
Time frame: From baseline through disease progression or study completion (approximately 2 years)
Objective Response Rate (ORR) (Phase 1)
Time frame: From baseline through disease progression or study completion (approximately 2 years)
Duration of response (DOR) (Phase 1 and Phase 2)
Defined as the time from the first confirmed response to radiologic/objective progression.
Time frame: From baseline through time to event on study or study completion (approximately 2 years)
Progression Free Survival (PFS) (Phase 1 and Phase 2)
Defined as the time from study drug treatment to death or disease progression, as determined by the investigator by radiographic disease assessment according to RECIST v1.1.
Time frame: From baseline through time to event on study or study completion (approximately 2 years)
Overall Survival (OS) (Phase 1 and Phase 2)
Defined as the time from study drug treatment initiation to death from any cause.
Time frame: Approximately 76 months
Disease control rate (DCR) (Phase 1 and Phase 2)
Defined as the proportion of patients who achieve tumor relief (CR or PR) and stable disease (SD) after treatment; calculated as the sum of CR, PR, and SD.
Time frame: From baseline through disease progression or study completion (approximately 2 years)
Clinical benefit rate (CBR) (Phase 1 and Phase 2)
Defined as the percentage of advanced cancer patients who achieve CR, PR, or at least six months of SD after treatment.
Time frame: From baseline through disease progression or study completion (approximately 2 years)
PK Parameters: Maximum plasma concentration (Cmax) (Phase 1)
Time frame: Day 1 and Day 15 of Cycle 1 (each cycle is 28 days)
PK Parameters: Time to maximum plasma concentration (Tmax) (Phase 1)
Time frame: Day 1 and Day 15 of Cycle 1 (each cycle is 28 days)
PK Parameters: Elimination half-life (t1/2) (Phase 1)
Time frame: Day 1 and Day 15 of Cycle 1 (each cycle is 28 days)
PK Parameters: Area under the plasma concentration-time curve from time 0 to last measurable concentration (AUC 0-last) (Phase 1)
Time frame: Day 1 and Day 15 of Cycle 1 (each cycle is 28 days)
Determination of RP2D (Phase 2)
Time frame: Approximately 16 months
Number of Participants with Treatment Emergent Adverse Events (TEAEs) and lab abnormalities (Phase 2)
Time frame: From baseline until end of study treatment or study completion (approximately 2 years)
Started Aug 2025 (actual). Primary completion is estimated for Aug 2028, 36 months after the start.
Of 161 industry-sponsored phase 1/2 interventional studies under Breast Neoplasms, half reached primary completion within 59 months of starting (the median), counting those still running; a quarter within 44 and three quarters within 75. This study's planned 36 months is below that.
Counting every sponsor, half of 327 studies reached it within 61 months; a quarter within 45 and three quarters within 88.
How these figures are worked out, and which studies are left out of them.
Eligibility is decided by the study team. Share this record with your doctor or contact the team directly.
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Avenzo Therapeutics, Inc.