Safety and Preliminary Effectiveness of BNT327, an Investigational Therapy for Breast Cancer, When Given in Combination With Chemotherapy

Inclusion Criteria: * Have given informed consent by signing and dating an informed consent form before initiation of any study-specific procedures. * Male or female, aged ≥18 years at the time of giving informed consent. * Are willing and able to comply with scheduled visits, the treatment schedule, the planned study assessments (including participant completed diaries) and other requirements of the study. This includes that they are able to understand and follow study-related instructions. * Have confirmed locally recurrent inoperable or mTNBC as defined by the most recent American Society of Clinical Oncology (ASCO) / College of American Pathologists (CAP) guidelines. Note, participants initially diagnosed with hormone receptor-positive and/or HER2-positive breast cancer must have histological confirmation of TNBC in a tumor biopsy obtained from a local recurrence or distant metastasis site. * Systemic treatment naïve locally advanced/metastatic participants are eligible if: * They have received no prior systemic therapy in the locally advanced unresectable/metastatic setting including chemotherapy, immunotherapy, or investigational agents. * They have completed treatment for Stage I-III breast cancer, if indicated, and ≥6 months has elapsed between the completion of treatment with curative intent (e.g., date of primary breast tumor surgery or date of last adjuvant chemotherapy administration, or date of last radiation therapy, whichever occurred last) and fir…