A Study of SYS6043 Versus Investigator's Choice Chemotherapy as First-Line Treatment in Patients With Unresectable Locally Recurrent or Metastatic Triple-Negative Breast Cancer

This is a randomized, controlled, open-label, multicenter study. Eligible participants are patients with unresectable locally recurrent or metastatic triple-negative breast cancer (TNBC) who have not received prior systemic therapy. Participants may be PD-L1 negative; or PD-L1 positive with disease recurrence after PD-1/PD-L1 inhibitor therapy in the neoadjuvant/adjuvant setting; or PD-L1 positive who cannot tolerate PD-1/PD-L1 inhibitor therapy due to other underlying comorbidities. Approximately 550 participants will be enrolled and randomized at a 1:1 ratio to the experimental group or the control group. All enrolled participants will continue study treatment until BICR-confirmed disease progression, no further clinical benefit as judged by the investigator, unacceptable toxicity, withdrawal of informed consent, loss to follow-up, death, or end of study, whichever occurs first. Upon discontinuation of study treatment, participants will complete the end-of-treatment (EOT) visit and safety follow-up. Survival visits will be performed every 3 months (±14 days) after the last study drug administration to collect participants' survival status and information regarding subsequent anti-tumor therapies