Phase 1 Dose-Escalation, Dose-Expansion Trial of Intratumoral HER2- and HER3-Primed Dendritic Cells Injections for the Treatment of Early-Stage TNBC and ER Low Positive Breast Cancer (DecipHER)

• A diagnosis of HER2-negative breast cancer.

• Diagnosis of HR negative or HR low positive tumor.

• Clinical stage T1c, nodal stage N1-N2 or stage T2-4, nodal stage N0-N2 breast cancer.

• Participant must be medically and surgically appropriate to undergo neoadjuvant chemotherapy regimen followed by standard of care local therapy as determined by their treating physician.

• Age ≥18 years.

• ECOG performance status 0 or 1.

• Patients must have normal organ and marrow function, as defined below, within 14 days of registration:

• \*Absolute neutrophil count (ANC) ≥ 1500/μL

• \*Platelets ≥ 75 000/μL

• \*Total bilirubin ≤ 1.5 x institutional ULN, except patients with Gilbert's syndrome in whom total bilirubin must be \< 3.0 mg/dL

• \*AST/ALT ≤ 3 x institutional ULN

• \*Creatinine ≤ 1.5 x institutional ULN

• Left ventricular ejection fraction above institutional lower limit of normal (by echocardiogram or MUGA scan).

• Female patients of childbearing potential must agree to use dual methods of contraception and have a negative serum pregnancy test at screening. 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 post-menopausal. Effective methods of contraception must be used throughout the study and for 5 months following the last dose. To show that women do not have childbearing potential, postmenopausal women must be amenorrheic for at least 12 months naturally (and not because of/following chemotherapy) or patients must be surgically sterile.

• Ability to understand and the willingness to sign a written informed consent agreement prior to study registration.