Phase I/II Study of Naxitamab and Sacituzumab Govitecan in Patients With Metastatic Triple-negative Breast Cancer (TNBC)

Inclusion criteria * Male and female participants aged 18 years or older and able to understand and give written informed consent * Eastern Cooperative Oncology Group (ECOG) performance status score of 0 or 1 (for the phase I portion of the study) and ECOG performance status of 0-2 (for the phase II portion of the study) * Life expectancy of at least 3 months * Histologically confirmed metastatic TNBC. (Estrogen receptor \[ER\] ≤10%; Progesterone receptor \[PgR\] ≤10%, HER2-negative as per ASCO/CAP guidelines) * Willingness to provide archival tumor tissue for correlative studies associated with this trial. * Received at least 1 prior line of systemic chemotherapy for metastatic TNBC and/or meet criteria to receive sacituzumab govitecan as standard of care * Measurable disease by CT or MRI as per RECIST Version 1.1 criteria * Adequate organ and marrow function as defined below: 2\. Exclusion Criteria Participants who meet any of the following exclusion criteria are not eligible to be enrolled in this study. * Positive serum pregnancy test or women who are lactating. * Known or severe (≥ Grade 3) hypersensitivity or allergy to naxitamab and/or sacituzumab govitecan, their metabolites, or formulation excipient. * Grade 3 or greater peripheral neuropathy * Have previously received treatment with an anti-GD2 antibody * Prior treatment with TROP2-targeting antibody drug conjugates in the metastatic setting. Participant s who have received TROP2-targeting antibody drug conjugates in the neoadjuvant setting or adjuvant setting are eligible if at least 6 months have elapsed since the last dose of TROP2-targeting antibody drug conjugate. * Have an active second malignancy. Participant s with a history of active cancer for 3 years prior to enrollment, or participant s with surgically cured tumors with low risk of recurrence (eg, nonmelanoma skin cancer, histologically confirmed complete excision of carcinoma in situ, or similar) are allowed to enroll. * Have known active central nervous system (CNS) metastases and/or carcinomatous meningitis. * Have undergone an allogenic tissue or solid organ transplant. * Uncontrolled hypertension, defined as a consistently elevated systolic blood pressure of \>160 mmHg despite optimal medical management * Clinically significant cardiac disease * Inadequate pulmonary function * Active chronic inflammatory bowel disease (ulcerative colitis, Crohn's disease) or GI perforation within 6 months of enrollment. * Uncontrolled seizure disorders despite anticonvulsant therapy (defined as a seizure event within 3 months prior to enrollment) * Active serious infection requiring systemic antimicrobial therapy. * Participants positive for HIV-1 or 2 with a history of Kaposi sarcoma and/or Multicentric Castleman Disease. * Have active hepatitis B or C infection * Has a diagnosis of immunodeficiency or receiving systemic corticosteroid therapy (higher than physiologic doses) ≥ 10 mg of prednisone per day or equivalent\] or any other form of immunosuppressive therapy within 14 days of initiation of study treatment. * Has received prior radiotherapy within 1 weeks of start of study intervention.