Adverse events of patients treated with antibody-drug conjugates in phase 1 clinical trials at the Royal Marsden Drug Development Unit from 2014 to 2024.

Abstract

e15020 Background: Antibody-drug conjugates (ADCs) are designed to improve therapeutic indices of cytotoxic agents. Nevertheless, they may induce unexpected toxicities not observed with parent payloads. This study aimed to characterize the adverse events (AEs) seen in patients treated with ADCs in Phase 1 trials at The Royal Marsden Drug Development Unit (DDU). Methods: This is a retrospective cohort analysis of consecutive patients who received at least one dose of an ADC in a phase I trial from January 2014 to January 2024 at The Royal Marsden DDU. Descriptive statistics of patient characteristics, ADCs, and treatment-related AEs were performed. Univariate and multivariate logistic regression will be utilized to assess correlations among patient and ADC characteristics and adverse events. P values of < 0.05 will be considered significant. Results: A total of 131 patients who participated in twelve ADC trials were included. The median age of participants was 63 years (range: 31-84) and 61% were females. Patients received a median of three prior lines of systemic treatment. The most common type of ADC target, antibody, linker and payload were receptor tyrosine kinase (51%), humanized IgG monoclonal antibody (69%), valine-citrulline (VC) cleavable linker (85%), and a tubulin-binding payload (59%), respectively. Most patients received an ADC dose of 1-3 mg/kg (76%) with each cycle given once every 3 weeks (64%). The median number of cycles was 3 with an average treatment duration of 63 days. Within the cohort, 89% of patients developed any grade AE and 17% experienced grade 3 or higher AEs. The major treatment-related AEs were fatigue (48%), nausea/vomiting (27%), ocular toxicity (26%), neuropathy (26%), skin rash (20%) and pneumonitis (8%). The median time to first onset of treatment-related adverse events were 37 days for ocular toxicity, 46 days for pneumonitis, and 54 days for neuropathy. ADC-related AEs led to treatment interruptions (51%), dose reductions (13%), and treatment discontinuations (28%). Two treatment-related grade 5 events occurred. The objective response rate was 18%, with 1 complete response and 22 partial responses. Conclusions: Despite being designed to minimize side effects, ADCs were associated with significant toxicities, including unexpected adverse events unrelated to target, antibodies or the payloads, limiting their therapeutic indices. Further analysis of the relationship between different components of the wide range of ADCs and AEs are warranted to better understand the potential mechanisms of ADC toxicity.