NCT07112053 · University of Washington
A Vaccine (STEMVAC) With Standard Endocrine-Based Therapy or Chemotherapy for the Treatment of Metastatic Hormone Receptor Positive, HER2 Negative Breast Cancer
What this study is about
This phase II trial studies how well a vaccine, STEMVAC, works in combination with standard endocrine-based therapy (ET) with a CDK4/6 targeted drug therapy, or with the chemotherapy drug capecitabine, in treating patients with hormone receptor (HR)-positive, HER2-negative breast cancer that has spread from where it first started (primary site) to other places in the body (metastatic).
View original scientific description
This phase II trial studies how well a vaccine, STEMVAC, works in combination with standard endocrine-based therapy (ET) with a CDK4/6 targeted drug therapy, or with the chemotherapy drug capecitabine, in treating patients with hormone receptor (HR)-positive, HER2-negative breast cancer that has spread from where it first started (primary site) to other places in the body (metastatic). STEMVAC is designed to target proteins that cancer cells use when they become more aggressive and start to spread, and it is believed to work by boosting the immune system to recognize and destroy the invader tumor cells that are causing the disease. Standard ET is treatment that adds, blocks, or removes hormones in order to slow or stop the growth of cancer. Standard CDK4/6 inhibitors, including abemaciclib, may stop the growth of tumor cells and may kill them by blocking some of the enzymes needed for cell growth. Capecitabine is in a class of medications called antimetabolites. It is taken up by tumor cells and breaks down into fluorouracil, a substance that kills tumor cells. Giving STEMVAC in combination with standard ET or chemotherapy may be an effective treatment for metastatic HR positive, HER2 negative breast cancer.
Interventions
BIOLOGICAL
CD105/Yb-1/SOX2/CDH3/MDM2-polyepitope Plasmid DNA Vaccine
Given ID
DRUG
Capecitabine
Given SOC capecitabine
PROCEDURE
Computed Tomography
Undergo CT or ultrasound-guided biopsies
DRUG
Cyclin-Dependent Kinase 4 Inhibitor
Given SOC CDK4/6i
DRUG
Cyclin-Dependent Kinase 6 Inhibitor
Given SOC CDK4/6i
DRUG
F-18 16 Alpha-Fluoroestradiol
Undergo FES PET
DRUG
Hormone Therapy
Given SOC ET
PROCEDURE
Positron Emission Tomography
Undergo PET or FES PET
PROCEDURE
Biopsy Procedure
Undergo image-guided biopsies
PROCEDURE
Biospecimen Collection
Undergo collection of blood samples
DRUG
Abemaciclib
Given SOC abemaciclib
Primary outcome measures
Incidence of adverse events (AEs)
Time frame: Up to 3 years after completion of study treatment
Safety and systemic toxicity will be determined by chemical and clinical parameters evaluated at various time points. Toxicity grading will be evaluated according to the National Cancer Institute (NCI) Common Terminology Criteria for Adverse Events version 6.0 and monitoring of AEs will be done per Food and Drug Administration and NCI guidelines. The type and grade of toxicities noted during the immunization regimen will be summarized. The duration of toxicities will also be summarized using descriptive statistics such as mean and standard deviation. All AEs noted by the investigator will be tabulated according to the affected body system. The frequency and severity of adverse events will be summarized with a proportion and a 95% confidence interval (CI).
Incidence of immunogenicity
Time frame: Pre-vaccine up to after 2 booster doses of STEMVAC vaccine (Up to 40 weeks)
Will be defined as the sum of the interferon gamma enzyme-linked immunosorbent spot of all STEMVAC antigens on blood samples collected pre-vaccine as compared to 1-month post dose #3 of the STEMVAC vaccine and again after 2 booster doses of STEMVAC vaccine. Both incidence and magnitude will be assessed. Immune responses will be summarized with mean and standard deviation or median and range (if skewness is observed) over time, the change over time will be summarized with graphs, and also analyzed using linear mixed-effects regression models with normalizing transformation if necessary.
Who can participate
This study lists these criteria on ClinicalTrials.gov. A study coordinator reviews eligibility during screening — this page does not determine whether you qualify.
Inclusion criteria
- Patients must be at least ≥ 18 years of age
- Histologically confirmed hormone receptor positive metastatic breast cancer: Tumors that are positive for estrogen receptor (ER) and/or progesterone receptor (PR)
- HER2-negative or HER2-low will be included and defined as:
- 0-1+ HER2 expression by immunohistochemistry (IHC) OR
- Fluorescence in situ hybridization (FISH) negative OR
- HER2 2+ and FISH negative
- HER2 low per standard of care in breast cancer
- Patients should be receiving the following therapies to be eligible for the study:
- Cohort 1: First or second line of endocrine therapy in the metastatic setting, in combination with a CDK4/6 inhibitor. Patients must have completed at least 2 cycles of CDK4/6 inhibitor. Patients who have stopped endocrine therapy for intolerance but remain on abemaciclib monotherapy will be considered for enrollment at the PI's discretion
- Cohort 2: Progressed on endocrine-based therapies and after completion of at least 1 cycle of capecitabine
- Subjects with Eastern Cooperative Oncology Group (ECOG) Performance Status Score of 0 or 1
- Willing to undergo up to two serial biopsies while on study
- Have at least 1 site of disease confirmed by the treating oncologist that could be biopsied during treatment
- White blood cell (WBC) ≥ 2000/mm\^3 (within 28 days of receiving the study vaccine)
- Lymphocyte count ≥ 500/mm\^3 (within 28 days of receiving the study vaccine)
- Absolute neutrophil count (ANC) ≥ 800/µL (within 28 days of receiving the study vaccine)
- Platelets ≥ 75,000/µL (within 28 days of receiving the study vaccine)
- Total bilirubin ≤ 1.5 x institutional upper limit of normal (ULN), except patients with Gilbert's syndrome in whom total bilirubin must be ≤ 3.0 mg/dL (within 28 days of receiving the study vaccine)
- Aspartate aminotransferase (AST)/alanine aminotransferase (ALT) ≤ 3 x institutional upper limit of normal (ULN) (within 28 days of receiving the study vaccine)
- Creatinine ≤ 2.0 mg/dL or creatinine clearance \> 30 mL/min (within 28 days of receiving the study vaccine)
- Patients of child-bearing potential must agree to use dual methods of contraception and have a negative urine pregnancy test at screening, and male patients must use an effective barrier method of contraception if sexually active with a female of child-bearing potential. Acceptable methods of contraception are condoms with contraceptive foam, oral, implantable or injectable contraceptives, contraceptive patch, intrauterine device, diaphragm with spermicidal gel, or a sexual partner who is surgically sterilized or postmenopausal. Effective methods of contraception must be used throughout the study and until the end of treatment on study
- Must have recovered from major infections and/or surgical procedures; and in the opinion of the investigator, not have any significant active concurrent medical illnesses or condition precluding protocol treatment
Exclusion criteria
- Patients with any of the following cardiac conditions:
- Symptomatic restrictive cardiomyopathy
- Dilated cardiomyopathy
- Unstable angina within 4 months prior to enrollment
- New York Heart Association functional class III-IV heart failure on active treatment
- Symptomatic pericardial effusion
- Uncontrolled hypertension
- Uncontrolled cardiac arrhythmias
- Patients with any autoimmune disease/comorbidity that require chronic steroids or immunosuppressants
- A non-breast malignancy requiring radiation or systemic therapy within last 5 years
- Known hypersensitivity reaction to the granulocyte-macrophage colony-stimulating factor (GM-CSF) adjuvant; any known contra-indication to GM-CSF
- Pregnant or breast feeding
- Known history of human immunodeficiency virus (HIV) infection, hepatitis B (e.g., hepatitis B virus surface antigen \[HBsAg\] reactive), or hepatitis C (e.g., hepatitis C virus \[HCV\] ribonucleic acid \[RNA\] \[qualitative\] is detected)
- Major surgery within the 4 weeks prior to initiation of study vaccine
- Current use of immunosuppressive agents or systemic corticosteroids. Topical, ocular, intra-articular, intranasal, and inhalational corticosteroids (with minimal systemic absorption) are allowed. Patients who have received systemic corticosteroids ≤ 30 days prior to starting study drug will be excluded
- Patient is currently enrolled in any other clinical protocol or investigational trial that involves administration of experimental therapy and/or therapeutic devices, or investigational drug
- NOTE: Biomarker or tissue collection or any other non-interventional clinical trial enrollment is allowed
- Must be 14 days between a non-study vaccine and any STEMVAC vaccination
- NOTE: The minimum of 14 days does not apply to the tetanus and diphtheria (Td) vaccine
- Any condition that may interfere with the patient's participation in the study per treating oncologist
Where
- Seattle, Washington
Related conditions & keywords
Frequently asked questions
What is a clinical trial?
A clinical trial is a research study that tests new medical treatments, drugs, devices, or procedures to determine their safety and effectiveness. Trials are carefully designed and monitored to protect participants while advancing medical knowledge.
Is it safe to participate?
Clinical trials follow strict safety guidelines and ethical standards. Trials must be reviewed and approved, and participants are closely monitored by medical professionals throughout the study. You can withdraw at any time if you choose.
Will I be compensated?
Many clinical trials offer compensation for your time, travel expenses, and inconvenience. The specific compensation varies by study and will be discussed during the screening process. All study-related medical care is typically provided at no cost to participants.
Will I receive a placebo instead of treatment?
When effective treatment exists, participants typically receive either the standard treatment plus the study intervention, or the standard treatment plus placebo. You would not be denied effective care. Placebos are primarily used when no proven treatment is available, or in addition to standard care. Your trial consent form will clearly explain what treatments you may receive.
Can I leave a trial if I change my mind?
Absolutely. Participation in clinical trials is completely voluntary. You have the right to withdraw from the study at any time, for any reason, without penalty or loss of benefits to which you are otherwise entitled.
How long does a clinical trial last?
Trial duration varies widely depending on the study design and purpose. Some trials last just a few weeks, while others may continue for months or years. The study coordinator will provide specific timeline information during your screening call.
Data: ClinicalTrials.gov · synced Apr 6, 2026 · Source of record for eligibility and locations