Trastuzumab deruxtecan is a new antibody-drug conjugate for the treatment of HER2-positive breast cancer, including residual early form of the disease after an incomplete response to previous therapy. In the phase III clinical study DESTINY-Breast03, the drug demonstrated a significant improvement in progression-free survival (PFS) and overall survival (OS) compared to standard treatment in patients with HER2-positive unresectable or metastatic breast cancer. 524 women were included in the study, of which approximately half had positive hormone receptors and about 70% had visceral involvement. Trastuzumab deruxtecan was also effective in patients previously treated with other anti-HER2 therapies, including trastuzumab and taxanes. The most common side effects included gastrointestinal and hematological problems, while the incidence of severe interstitial lung disease was low and mostly manageable with corticosteroids. This drug represents a significant advance in the treatment of HER2-positive breast cancer and changes the current treatment approach. Trastuzumab deruxtecan is approved for patients with unresectable or metastatic HER2-positive breast cancer who have received at least one line of anti-HER2 therapy[1][2][4][6].