DESTINY Breast05 (GBG103)

This study investigated which treatment is more effective for patients with HER2-positive breast cancer following neoadjuvant therapy and with residual invasive disease: trastuzumab deruxtecan (T-DXd) or trastuzumab emtansine (T-DM1).

The focus was on invasive disease-free survival (IDFS). IDFS was evaluated in both a 3-year and a 5-year analysis to compare the long-term efficacy of the two treatments.

The first interim efficacy analysis, based on data as of July 2, 2025, showed a significant improvement in invasive disease-free survival (IDFS) with T-DXd treatment compared to T-DM1. In this analysis, T-DXd demonstrated superior efficacy with a manageable safety profile. These results were published in the New England Journal of Medicine and led to the FDA designating T-DXd as a “breakthrough therapy” on December 22, 2025.

The study data were presented at several scientific conferences in 2025, including as oral presentations at ESMO 2025 and SABCS 2025. The study was submitted to the FDA in January 2026.

The second database lock (Database Lock 2) is scheduled for the summer or early September 2026.