A Study to Assess CLBR001+ABBV-461 in Subjects With Locally Advanced or Metastatic Breast Cancer

Inclusion Criteria: * Refractory or relapsed locally advanced or metastatic breast cancer * Exhaused all standard of care therapy options * Measurable disease at time of screening in accordance with RECIST v1.1 criteria * Women or men age ≥18 years of age at time of consent * ECOG performance status 0 or 1 * Must provide a biopsy sample obtained during the screening period, following the end of the most recent prior line of therapy * Adequate hematological, renal, and liver function Exclusion Criteria: * History of a clinically significant infection within 4 weeks prior to consent * Active bacterial, viral, and/or fungal infection * Prior allogeneic stem cell transplant * Prior lentiviral- or retroviral-based therapy including CAR-T cell therapy * Prior lymphodepleting or T-cell cytotoxic therapy within 3 months of enrollment * Subjects receiving attenuated vaccines within 4 weeks of consent or need for live vaccine within 12 months of starting study therapy * History of significant cardiovascular conditions within the past 6 months * Subjects with a prior history of or concurrent malignancy whose natural history or treatment has the potential to interfere with either the safety or efficacy assessment of the investigational regimen