Platform Study of ADC Rechallenge in ADC-treated Metastatic Breast Cancer

The duration of overall response is measured from the time measurement criteria are met for CR or PR (whichever is first recorded) until the first date that recurrent or progressive disease is objectively documented (taking as reference for progressive disease the smallest measurements recorded since the treatment started, or death due to any cause). Participants without reported events are censored at the last disease evaluation.

PFS based on Kaplan-Meier methodology will be defined as the time from randomization until the identification of disease progression or death, whichever occurs first. Subjects without disease progression or death at the time of analysis will be censored at the date of last disease evaluation.

Clinical Benefit Rate (CBR) is defined as the proportion of participants with CR, PR and stable disease (SD) for ≥ 24 weeks as the best overall response.

Overall survival based on the Kaplan-Meier method is defined as the time from randomization to death. Participants alive are censored at the last date of contact (including lost-to-follow-up) or at the date of withdrawal of consent, if relevant.

The percentage of participants who experienced any grade treatment-related adverse event based on the Common Toxicity Criteria for Adverse events Version 5.0 (CTCAEv5) as reported on case report forms.

The collected subjects' tumor tissues, paracancerous tissues, blood, and fecal samples will be used for discovering exploratory biomarkers (including but not limited to the expression of HER2, TROP2, HER3, Nectin4, etc.). The relationships between discovered biomarkers and subjects' disease status and treatment responses will also be investigated.