Trastuzumab plus nivolumab with gemcitabine and cisplatin as first-line therapy for HER2-positive unresectable biliary tract cancer: a phase 1b/2 trial.

Biliary tract cancers (BTCs) are associated with poor outcomes despite recent incorporation of immune checkpoint inhibitors into first-line chemotherapy. Human epidermal growth factor receptor 2 (HER2) overexpression or amplification defines a therapeutically targetable subset of BTC but its integration into first-line chemoimmunotherapy has not been prospectively evaluated. This multi-institutional, open-label, phase 1b/2 HERBOT study (KCSG-HB23-05) aimed to evaluate first-line HER2-targeted quadruplet regimen consisting of trastuzumab, nivolumab, gemcitabine and cisplatin in participants with HER2-positive advanced BTC. Here the primary endpoint was met with an objective response rate of 55% (95% confidence interval (CI) 38.5-70.7; one complete response and 21 partial responses among 40 participants) and a disease control rate of 95% (95% CI 83.5-99.4); the median duration of response was 12.6 months (95% CI 5.7-not reached). With a median follow-up of 17.0 months, the median progression-free survival was 10.6 months (95% CI 7.8-17.4) and median overall survival was not reached. Two participants (5.0%) underwent curative-intent conversion surgery. Common grade ≥3 treatment-related adverse events included neutropenia (57.5%), anemia (30.0%) and thrombocytopenia (22.5%). Preplanned artificial-intelligence-powered whole-slide image analyses suggested that tumors with higher proportions of HER2 3+ cells were associated with greater clinical benefit. These findings suggest that upfront HER2-targeted therapeutic intensification in BTC may represent a promising direction for future first-line treatment strategies, with relevance to ongoing phase 3 studies. ClinicalTrials.gov identifier: NCT05749900 .