A Phase 3, Randomized, Open-label Study Comparing Efficacy and Safety of Sacituzumab Tirumotecan (sac-TMT, MK-2870) as a Monotherapy and in Combination with Pembrolizumab (MK-3475) Versus Treatment of Physician’s Choice in Participants With Previously Untreated Locally Recurrent Unresectable or Metastatic Triple-Negative Breast Cancer Expressing PD L1 at CPS Less than 10 (TroFuse 11)

This trial is testing sacituzumab tirumotecan (sac-TMT) when given alone and with pembrolizumab (pembro) in people with triple negative breast cancer (TNBC). The trial will test these drugs in people with TNBC that: Cannot be treated with surgery; Has spread to other parts of the body Sac-TMT is experimental. It has not been approved to treat any cancers. It is also called MK 2870. Pembro has been approved by some health authorities for treating various cancers, including some types of TNBC. It is not approved in any country for your type of TNBC. It is also called KEYTRUDA. This trial will compare giving sac-TMT alone or with pembro to giving standard chemotherapy. This trial will: Test the safety of sac-TMT, sac-TMT given with pembro, and standard chemotherapy. See how well sac-TMT works, compared to standard chemotherapy. See how well the combination of sac-TMT and pembro works, compared to standard chemotherapy. See if participants who get sac-TMT alone have a better quality of life than participants who get standard chemotherapy. See if participants who get sac-TMT with pembro have a better quality of life than participants who get standard chemotherapy. Measure what happens as sac-TMT goes through the body.