Unveiling the molecular and immunological drivers of antibody–drug conjugates in cancer treatment

After decades of investment, antibody–drug conjugates (ADCs) are finally demonstrating their potential, marked by a growing number of clinical approvals, applications in earlier lines of treatment and integration into drug combinations, including immunotherapies. This progress has spurred investment in developing new ADCs and expanding the use of approved ADCs in clinical practice. The design of ADCs is complex, involving multiple molecular components that interact with both tumour and host tissue microenvironments. In this Review, we explore the molecular and immunological factors influencing ADC efficacy and toxicity. We describe how the molecular components of ADCs determine their systemic, tissue and cellular distribution, which ultimately dictates therapeutic efficacy. These interactions also determine the toxicity profile and set limitations on maximum dosing. Finally, we discuss the impact of ADC treatment on immune cells, emphasizing the distinct but interconnected roles of immunogenic cell death, activation of immune cells such as dendritic cells and antibody–Fc interactions. These mechanisms are crucial for increasing efficacy beyond the direct cytotoxic effects of the payload. By providing insights into the intricate interactions of ADCs, this Review aims to inform the rational design of combination therapies and guide the development of the next generation of clinically effective ADCs.