STEMVAC in Patients With Early Stage Triple Negative Breast Cancer

Inclusion Criteria:

Participants with triple negative breast cancer, stages IB, II or III. Estrogen receptor (ER)-negative and progesterone receptor (PR)-negative is defined as breast cancer with less than 1% of ER or PR expression. HER2 negative is defined as:

0-1+ HER2 expression by immunohistochemistry (IHC) OR
Fluorescence in situ hybridization (FISH) negative OR
HER2 2+ and FISH negative

Participants must have completed standard of care systemic therapy (including immune modulating agents) and radiotherapy if used between 28 and 365 days prior to enrollment

* Note: Treatment with a bisphosphonate or denosumab to prevent bone loss is not considered to be systemic therapy for breast cancer and its use within the 28 day pre-enrollment period or while on study is not exclusionary

Participants must agree to avoid systemic steroids for the duration of the treatment period and until completion of the 1 month post 2nd booster vaccine visit (end of treatment)
Participants must be at least 18 years of age
Participants must have Eastern Cooperative Oncology Group (ECOG) performance status score of =< 1
White blood cell (WBC) >= 3000/mm^3 (within 60 days of enrollment and at least 28 days post standard of care [SOC] treatment)
Lymphocyte count >= 800/mm^3 (within 60 days of enrollment and at least 28 days post standard of care [SOC] treatment)
Platelet count >= 100,000/mm^3 (within 60 days of enrollment and at least 28 days post standard of care [SOC] treatment)
Hemoglobin (Hgb) >= 10 mg/dl (within 60 days of enrollment and at least 28 days post standard of care [SOC] treatment)
Serum creatinine =< 1.2 mg/dl OR creatinine clearance > 60 ml/min (within 60 days of enrollment and at least 28 days post standard of care [SOC] treatment)
Total bilirubin =< 1.5 X upper limit of institutional normal (ULN) (within 60 days of enrollment and at least 28 days post standard of care [SOC] treatment)
AST (aspartate aminotransferase)/serum glutamic-oxaloacetic transaminase (SGOT) =< 1.5 X upper limit of institutional normal (ULN) (within 60 days of enrollment and at least 28 days post standard of care [SOC] treatment)
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 precluding protocol treatment

The effects of STEMVAC on the developing human fetus are unknown. For this reason,

Female participant agrees to use adequate contraception (examples include: estrogen and/or progestogen containing hormonal contraception, barrier method (condom, cervical cap) or abstinence) while on the study and until 1 month after the 2nd booster vaccination when/if engaging in sex that could lead to pregnancy. Exceptions: Females who have had a hysterectomy, tubal ligation or bilateral oophorectomy OR meet one of the following criteria for postmenopausal: Age > 60 or age < 60 with >= 12 months amenorrhea and follicle-stimulating hormone (FSH) within the testing facility's postmenopausal range
Female participant agrees to inform her study physician immediately should she become pregnant or suspect she is pregnant while participating in this study
Male participants who are having sex that can lead to pregnancy must use an acceptable form of contraception (vasectomy with the absence of sperm, sexual abstinence, condoms) throughout the course of the study
Patients must be willing to not undergo major elective surgical procedures with general anesthesia or conscious sedation through the end of treatment visit. (Note: port removal is allowable)
Ability to understand and the willingness to sign a written informed consent document

Exclusion Criteria:

Contraindication or known hypersensitivity to receiving sargramostim (rhuGM-CSF) or other yeast based products
History of allergic reactions attributed to compounds of similar chemical or biologic composition to STEMVAC
Participants receiving any other investigational agents or enrolled in any other treatment study
Chronic use of nonsteroidal anti-inflammatory drugs (NSAIDs) is prohibited during the treatment period of the study, except when taken as low-dose (81 mg) aspirin therapy. Prohibited chronic use is defined as daily use for more than 7 days
Participants with any clinically significant autoimmune disease uncontrolled with treatment
Uncontrolled intercurrent illness including, but not limited to, ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness/social situations that would limit compliance with study requirements
Pregnant and breastfeeding women are excluded from this study

Known history of human immunodeficiency virus (HIV) infection, hepatitis B, or hepatitis C

* Note: These individuals are excluded in order to avoid confounding an existing condition with an immune response to STEMVAC

Has > Common Terminology Criteria for Adverse Events (CTCAE) grade 1 (mild) residual toxicity from prior breast cancer treatment