Time-of-day of first checkpoint inhibitor dose influences clinical outcomes and immune responses in hepatocellular carcinoma

BACKGROUND: Although immune checkpoint inhibitors (ICIs) have long half-lives, preclinical and retrospective clinical studies across multiple tumor types suggest that the time-of-day of ICI infusion may influence therapeutic efficacy by aligning initial drug exposure with circadian peaks in T-cell responsiveness. The immunological basis of this phenomenon and its clinical relevance in hepatocellular carcinoma (HCC) remains unknown. METHODS: We followed patients with advanced HCC receiving ICI therapy at Johns Hopkins from 2021 to 2025, classifying them into a morning (first treatment before 12:00 hours) or afternoon (first treatment after 12:00 hours) group. We assessed clinical outcomes and compared immunological responses from baseline to early-on-treatment by profiling peripheral blood mononuclear cells using cytometry by time-of-flight and plasma cytokines using a 39-plex Luminex assay. RESULTS: Our cohort included 84 patients, 39 of whom received their first infusion in the morning. There were no statistically significant differences in baseline demographic or clinical characteristics between patients initiating therapy in the morning versus afternoon. The morning group had superior progression-free survival (multivariable HR 0.50, 95% CI 0.30 to 0.84, p