Despite advances in the treatment of early triple-negative breast cancer (TNBC), patients with residual invasive disease after neoadjuvant therapy have a high risk of disease recurrence and worse survival outcomes than those who have pathological complete response (pCR). Improving outcomes in early TNBC remains an unmet need requiring new adjuvant treatment approaches. Datopotamab deruxtecan (Dato-DXd) is an antibody-drug conjugate comprising a humanized anti-trophoblast cell-surface antigen 2 immunoglobulin G1 (IgG1) monoclonal antibody attached a plasma-stable, cleavable linker to a potent topoisomerase I inhibitor payload, with activity observed in advanced TNBC.

TROPION-Breast03 is an ongoing phase III study evaluating the efficacy and safety of Dato-DXd alone or combined with durvalumab standard-of-care therapy as adjuvant treatment in patients with stage I-III TNBC with residual invasive disease at surgical resection following neoadjuvant treatment.

Eligible patients, aged ⩾18 years, will be randomized in a 2:1:2 ratio to receive Dato-DXd [6 mg/kg intravenously (IV) every 3 weeks (Q3W); eight cycles] and durvalumab (1120 mg IV Q3W; nine cycles), Dato-DXd monotherapy (6 mg/kg IV Q3W), or investigator's choice of therapy (ICT; capecitabine, pembrolizumab, or capecitabine and pembrolizumab). The primary endpoint is invasive disease-free survival (iDFS) for Dato-DXd and durvalumab ICT. Key secondary endpoints include safety, distant disease-free survival, and overall survival for Dato-DXd and durvalumab ICT and iDFS for Dato-DXd monotherapy ICT.

TROPION-Breast03 will be approved by the independent ethics committees or institutional review boards at each study site. All study participants will provide written informed consent.

TROPION-Breast03 will help define the potential role of Dato-DXd in the treatment of patients with early-stage TNBC who do not have pCR after neoadjuvant therapy.

ClinicalTrials.gov identifier: NCT05629585 (registration date: 29 November 2022).