Antibody-Drug Conjugates in Breast Cancer: Toward a Molecular Perspective Into Clinical Practice.

Antibody-drug conjugates (ADCs) are at the forefront of cancer therapy, combining targeted precision with potent cytotoxicity. Conceived by Paul Ehrlich in the early 1900s, the concept of a magic bullet selectively eliminating cancer cells has evolved alongside bioengineering and cancer biology advancements. ADCs consist of a monoclonal antibody, linker, and cytotoxic payload, designed to target specific antigens on tumor cells while minimizing collateral damage. Mechanistically, ADCs are internalized via endocytosis, releasing the cytotoxic payload within the lysosome, potentially affecting neighboring tumor cells. ADC development has progressed through multiple generations, each addressing limitations of its predecessors. From gemtuzumab ozogamicin to trastuzumab emtansine (T-DM1), and now to third-generation agents such as trastuzumab deruxtecan (DS-8201) and disitamab vedotin (RC48), improvements have been made in target selectivity, potency, linker stability, and reduced off-target effects. Significant success has been seen in ADCs targeting human epidermal growth factor receptor 2 and trophoblast cell-surface antigen 2 antigens, especially in patients with breast cancer, including those resistant to previous therapies. The future of ADCs includes exploring new surface antigens, bispecific antibodies, immune-activating antibodies, radiopharmaceutical-loaded ADCs, and masked ADCs for tissue-specific activation. Ongoing research aims to optimize treatment efficacy while minimizing toxicity, expanding the potential of combination therapy. ADCs represent a promising frontier in precision cancer treatment, with continued research enhancing their potential in breast cancer and beyond. This review provides a comprehensive exploration of ADCs' evolution in breast cancer therapy, offering a molecular perspective to inform clinical practice and update colleagues on this dynamic field.