A Cancer Vaccine (STEMVAC) in Combination With Chemotherapy for the Treatment of PD-L1 Negative Metastatic Triple-Negative Breast Cancer

Inclusion Criteria28

• Patients must be at least ≥ 18 years of age
• Note: Because no dosing or adverse event (AE) data are currently available on the use of STEMVAC in patients \< 18 years of age, children and adolescents are excluded from this study, but will be eligible for future pediatric trials, if applicable
• Patients with Eastern Cooperative Oncology Group (ECOG) Performance Status Score of ≤ 2
• Histologically confirmed triple-negative breast cancer
• Tumors with estrogen receptor (ER)-low (≤ 5%) or negative and progesterone receptor (PR)-low (≤ 5%) or negative will be included
• HER2-negative or HER2-low will be fined by the American Society of Clinical Oncology (ASCO)/College of American Pathologists (CAP) 2023 "Human Epidermal Growth Factor Receptor 2 (HER2) Breast Testing Guideline Update" which reaffirms the 2018 "HER2 Breast Testing Guideline Focused Update"
• Tumor is negative for PD-L1 marker testing per standard of care antibodies/clones in breast cancer at time of eligibility
• Metastatic disease that is measurable based on Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 or PET Response Criteria in Solid Tumors (PERCIST). Target lesions situated in a previously irradiated area are considered measurable if progression has been demonstrated in such lesions
• Have at least 1 site of disease confirmed by the treating oncologist that could be biopsied during treatment. This site should not be a site that is used to determine measurable disease for efficacy purposes. Lesions that will be biopsied should not be in a previously irradiated area unless progression has been demonstrated in such lesions
• Patients should not have received any prior cancer immunotherapy in the metastatic setting
• Prior Food and Drug Administration (FDA)-approved antibody drug conjugates are allowed
• Patients are appropriate candidates to receive standard of care chemotherapy as per treating oncologist's clinical judgement
• NOTE: Only chemotherapy partners listed in the protocol are allowed to be administered in metastatic setting concurrently with STEMVAC vaccine
• Patients who have received prior neoadjuvant or adjuvant chemotherapy are allowed
• A minimum of 14 days washout since last systemic therapy or any palliative radiotherapy is required
• Treatment with a bisphosphate or denosumab concurrently with protocol-specific therapy is allowed while on study (it is not exclusionary)
• Patients must be at least 28 days post systemic steroids prior to enrollment, unless this is a steroid administered concurrently with chemotherapy or used as part of prophylaxis to prevent intravenous (IV) contrast reactions
• 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
• Willing to undergo up to two serial biopsies while on study
• White blood cell (WBC) ≥ 2500/mm\^3 (Within 28 days of receiving first study vaccine)
• Lymphocyte count ≥ 500/mm\^3 (Within 28 days of receiving first study vaccine)
• Absolute neutrophil count (ANC) ≥ 1000/μL (Within 28 days of receiving first study vaccine)
• Hemoglobin (Hgb) ≥ 9 g/dl (Within 28 days of receiving first study vaccine)
• Platelets ≥ 75,000/μL (Within 28 days of receiving first 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 first study vaccine)
• Aspartate aminotransferase (AST)/alanine aminotransferase (ALT) ≤ 1.5 X institutional ULN (Within 28 days of receiving first study vaccine)
• Creatinine ≤ 1.5 X ULN mg/dL or creatinine clearance \> 60 ml/min (Within 28 days of receiving first 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 person of child-bearing potential. Acceptable methods of contraception are abstinence, 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 post-menopausal. Effective methods of contraception must be used throughout the study until the end of treatment on study