Treatment-related adverse events of antibody drug-conjugates in clinical trials

Antibody-drug conjugates (ADCs) aim to enhance the therapeutic index of cytotoxic agents but can cause unexpected toxicities. This study evaluated adverse events (AEs) from phase 1 trials at The Royal Marsden Drug Development Unit (DDU) over a decade and pivotal phase 2 and 3 trials leading to FDA registration, correlating AEs with ADC components such as target, antibody, linker, payload, and Drug-to-Antibody Ratio (DAR).

We performed a retrospective cohort analysis of patients treated with ADCs in phase 1 trials (January 2014 to January 2024) compared to published phase 2-3 trials of FDA-approved ADCs. Univariate and multivariate logistic regression analyzed ADC components and treatment toxicities.

One hundred thirty one phase 1 trial patients and 2666 phase 2-3 trial participants were included. High incidences of any-grade treatment-related AEs were observed (89% in phase 1, 93% in phase 2-3), with 58% experiencing grade 3 or higher toxicities in phase 1 and 46% in later phases. Major AEs included fatigue, hematologic toxicities, nausea/vomiting, ocular toxicities, and peripheral neuropathy. Antibody targets were linked to neuropathy, non-cleavable linkers to ocular, pulmonary, and hematologic toxicities, and tubulin-binding payloads to peripheral neuropathy. ADCs with DAR > 4 were associated with higher pulmonary and hematologic AEs.

Despite their design to minimize toxicity, ADCs were linked to significant AEs. Specific ADC components may contribute to distinct toxicities, necessitating more robust trial data to inform future ADC design.