Radiolabeled Antibody-Drug Conjugates in the Treatment of Solid Tumors

Antibody-drug conjugates (ADCs) utilize monoclonal antibodies (mAbs) that target tumor-specific antigens to deliver potent cytotoxic chemotherapy payloads to the tumor, while sparing normal tissues. The chemotherapy agents employed in ADCs are very potent, causing a tumoricidal effect at low drug concentrations. Several ADCs have been approved for the treatment of different solid tumors over the last decade following the superior efficacy and safety they demonstrated above standard-of-care treatment modalities in several clinical trials. Despite their efficacy, some patients do not respond to treatment with ADCs, as objective response rate typically range from 30% to 50%, and as low as 20% in some instances. Some patients who initially respond to treatment develop acquired resistance during their treatment, necessitating strategies to improve response rates and overcome treatment resistance. Radiation from radionuclides, with their ability to evoke a synergistic antitumor effect when used in combination with cytotoxic chemotherapy and induce a tumoricidal effect in tumor cells remote from the tumor they are bound to (crossfire effect), has the potential to improve the outcomes of ADC treatment. An expanding body of evidence, reporting the successful radiolabeling of established and experimental ADCs, is emerging in the literature. These studies have demonstrated improved antitumor effect of radiolabeled ADC relative to cold ADC, paving the way for further exploration, including in clinical settings.