Screening images may be obtained within 5 weeks of regist ration. Imaging obtained as part of standard of care but within 28 days (-7 days) of registration may be used for screening assessment. Imagin g may include chest, abdomen and pelvis CT or MRI scans, and bone scans. Bone scans will be performed at baseline if disease is suspected and on study as appropriate to fol low disease. Baseline central nervous system (CNS) imaging MRI or CT Brain to be conducted only if clinically indicated based on the investigator’s judgement. CT or MRI sc ans, as well as bone scans, when indicated, are to be done every 8 weeks (±5 days) with the first one to occur 8 weeks after C1D1 Repeat imaging will be completed every 8 wee ks up to and including Week 32 or until disease progression that requires new treatment modality, permanent discontinuation, or death. Disease progression will be con firmed with two consecutive timepoints at least 4-8 weeks apart in the absence of rapid clinical deterioration. Tumor assessment should be repeated at the End of Treatme nt visit if more than 6 weeks have passed since the last evaluation. 25. Acetylcholine receptor (AChR) antibody: Sample to be sent to the central laboratory for analysis. The evaluation for AChR antibodies is inc luded to exclude participants who test positive at screening as agreed upon with the United States Food and Drug Administration (US FDA) and to confirm requirement for evaluation if myasthenia gravis is suspected .99 30. ER, PR and HER2 Status : Inclusion Criteria 1(Section 4.1) defines TNBC as HER2 negative by IHC, FISH or CISH, and ō10% ER/PR stain positive. Results required during Screening, prior to participant randomization.