Lessons learned from QT prolongation risk assessment for antibody-drug conjugates in oncology

Antibody-drug conjugates (ADCs) are advanced cancer therapeutics that link monoclonal antibodies to cytotoxic drugs, enhancing targeted delivery to tumors. Since the FDA's first ADC approval in 2000, 14 ADCs have received approval to date (March 2025), underscoring their therapeutic value across cancer types. A prolonged QT interval is a known risk factor for the development of torsades de pointes (TdP), a potentially fatal ventricular arrhythmia. Therefore, assessing and mitigating the potential for QT prolongation is a fundamental aspect of drug development, especially for oncology therapeutics where patients may already be at an increased risk of cardiovascular complications or receiving other QT-prolonging drugs. Traditional QT risk assessment, as outlined in the ICH E14 guidance, is challenging in oncology due the safety profile of anticancer drugs, which precludes study in healthy participants, and the ethical complications of placebo-controlled studies in patients with cancer; therefore, dedicated QT studies and/or concentration-corrected QT (QTc) assessments have been used as alternative approaches. This review investigates QT risk assessment for FDA-approved ADCs, examining nonclinical and clinical approaches and summarizing the strategies used in informing each ADC's labeling. Findings suggest that ADCs generally exhibit low proarrhythmic risk, attributed to the low systemic concentration of their payloads, and minimal QT effects have been observed in clinical settings. This analysis advocates a streamlined, fit-for-purpose QT risk assessment strategy in ADC development, reducing reliance on dedicated QT studies and promoting integrated assessments in early-phase trials. This approach can optimize ADC safety evaluation, supporting ongoing innovation and therapeutic application in oncology.