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