A Study of Disitamab Vedotin in Adults With HER2 Expressing Advanced Breast Cancer

Required: HER2 (ERBB2) overexpression (IHC 3+ or IHC 2+/ISH+)

HER2+: immunohistochemistry (IHC) 3+ or IHC 2+/in situ hybridization (ISH)+

Required: HER2 (ERBB2) low expression (IHC 1+/ISH-negative or untested or IHC 2+/ISH-negative)

HER2-low: IHC 1+/ISH-negative or untested or IHC 2+/ISH-negative

Required: HER2 (ERBB2) ultralow expression (IHC 0 with membrane staining (>0 and ≤10% of cancer cells))

HER2-ultralow: IHC 0 with membrane staining (any staining of the membrane in >0 and ≤10% of cancer cells)

Allowed: ESR1 overexpression

HR+ disease is determined as either estrogen receptor (ER) and/or progesterone receptor (PgR) positive [ER or PgR ≥1%])

Allowed: PR (PGR) overexpression

HR+ disease is determined as either estrogen receptor (ER) and/or progesterone receptor (PgR) positive [ER or PgR ≥1%])

Allowed: ESR1 wild-type

HR negative disease is determined as both ER and PR negative [ER and PgR <1%])

Allowed: PR (PGR) wild-type

HR negative disease is determined as both ER and PR negative [ER and PgR <1%])

Allowed: BRCA1 germline mutation

Participants with known germline breast cancer gene (BRCA) mutation must have received a poly-ADP ribose polymerase (PARP) inhibitor

Allowed: BRCA2 germline mutation

Participants with known germline breast cancer gene (BRCA) mutation must have received a poly-ADP ribose polymerase (PARP) inhibitor

Allowed: PD-L1 (CD274) overexpression

programmed cell death receptor ligand 1 (PD-L1)-positive (combined positive score [CPS] ≥10)

Must have received: trastuzumab (trastuzumab) — advanced disease

Received prior trastuzumab, pertuzumab and a taxane if available as local first line standard of care therapy for advanced disease.

Must have received: pertuzumab (pertuzumab) — advanced disease

Received prior trastuzumab, pertuzumab and a taxane if available as local first line standard of care therapy for advanced disease.

Must have received: taxane — advanced disease

Received prior trastuzumab, pertuzumab and a taxane if available as local first line standard of care therapy for advanced disease.

Must have received: antibody-drug conjugate (trastuzumab deruxtecan) — any line advanced disease

Must have progression on or after, or be intolerant to, T-DXd in any line advanced disease setting.

Must have received: PARP inhibitor

Participants with known germline breast cancer gene (BRCA) mutation must have received a poly-ADP ribose polymerase (PARP) inhibitor, where available and not medically contraindicated.

Must have received: endocrine therapy — locally advanced/metastatic

Must have intolerance to endocrine therapy (ET) or ET refractory disease: Progressed on ≥2 lines of ET for LA/mBC AND had received a cyclin-dependent kinase (CDK)4/6 inhibitor in the adjuvant or metastatic setting if available as local standard of care and not contraindicated.

Must have received: CDK4/6 inhibitor — adjuvant or metastatic

had received a cyclin-dependent kinase (CDK)4/6 inhibitor in the adjuvant or metastatic setting if available as local standard of care and not contraindicated.

Must have received: endocrine therapy — locally advanced/metastatic

Progressed on 1 line of ET for LA/mBC AND had a relapse while on adjuvant ET after definitive surgery for primary tumor AND had received a cyclin-dependent kinase (CDK) 4/6 inhibitor in the adjuvant or advanced setting if available as local standard of care and not contraindicated.

Must have received: CDK4/6 inhibitor — adjuvant or advanced

had received a cyclin-dependent kinase (CDK) 4/6 inhibitor in the adjuvant or advanced setting if available as local standard of care and not contraindicated.

Must have received: antibody-drug conjugate (sacituzumab govitecan)

Prior sacituzumab govitecan is allowed.

Must have received: anti-PD-L1 therapy (pembrolizumab) — with chemotherapy

Participants with HR negative (TNBC), HER2-low and programmed cell death receptor ligand 1 (PD-L1)-positive (combined positive score [CPS] ≥10) tumors must have received pembrolizumab (or other PD-L1 inhibitor) with chemotherapy if available as local standard of care therapy and not medically contraindicated.

Must have received: endocrine therapy

Participants with HR+/HER2-ultra low tumors must have received at least 1 antihormonal therapy in any setting or be ineligible for ET.

Must have received: CDK4/6 inhibitor — adjuvant or advanced

Participants with HR+/HER2-ultra low tumors must have had prior therapy with a CDK4/6 inhibitor in the adjuvant or advanced setting.

Cannot have received: antibody-drug conjugate with MMAE payload

Prior therapy with ADCs with MMAE payload.