HER2-Directed Intensification Moves Into First-Line Treatment
Biliary tract cancers (BTCs) are a heterogeneous collection of malignancies — including intrahepatic cholangiocarcinoma and other subtypes arising in the biliary system — that continue to carry a poor prognosis. Immune checkpoint inhibitors have been added to first-line chemotherapy in recent years, yet the overall benefit for most patients remains limited, leaving a clear need for better upfront strategies.
One promising subset is defined by human epidermal growth factor receptor 2 (HER2) overexpression or amplification, a molecular feature that makes these tumors targetable with existing HER2-directed drugs. Until now, however, the question of whether HER2 blockade could be combined safely with checkpoint inhibition and chemotherapy as first-line treatment had not been prospectively evaluated. The multi-institutional, open-label phase 1b/2 HERBOT study (KCSG-HB23-05), reported in Nature Medicine on 22 September 2026, was designed to fill that gap.
How the HERBOT Trial Was Designed
Investigators enrolled participants with HER2-positive advanced BTC and treated them with an upfront quadruplet regimen: trastuzumab, nivolumab, gemcitabine and cisplatin. The approach layers HER2-targeted therapy onto a PD-1 checkpoint inhibitor and a chemotherapy backbone already familiar in the first-line BTC setting.
The trial's primary endpoint was objective response rate, with the study conducted across multiple institutions and registered on ClinicalTrials.gov under the identifier NCT05749900. The design was open label, meaning participants and investigators knew which treatments were being given, and the phase 1b/2 structure was intended to establish both tolerability and early signals of activity before larger randomized testing.
Response Rates and Survival Outcomes
The primary endpoint was met. Among 40 participants, the objective response rate reached 55% (95% confidence interval 38.5–70.7), comprising one complete response and 21 partial responses. The disease control rate was 95% (95% CI 83.5–99.4), indicating that nearly every participant had either a response or stable disease.
Responses appeared durable rather than fleeting. The median duration of response was 12.6 months (95% CI 5.7 months to not reached). With a median follow-up of 17.0 months, median progression-free survival was 10.6 months (95% CI 7.8–17.4), while median overall survival had not been reached at the time of reporting.
Investigators also noted that two participants, or 5.0% of the cohort, were able to undergo curative-intent conversion surgery. In a disease setting where tumors are considered unresectable at the outset, the possibility of converting a patient to surgery represents a meaningful, if uncommon, milestone.
Key Numbers From the Trial
- Objective response rate: 55% (95% CI 38.5–70.7) among 40 participants
- One complete response and 21 partial responses
- Disease control rate: 95% (95% CI 83.5–99.4)
- Median duration of response: 12.6 months (95% CI 5.7–not reached)
- Median progression-free survival: 10.6 months (95% CI 7.8–17.4)
- Median overall survival: not reached with median follow-up of 17.0 months
- Curative-intent conversion surgery: 2 participants (5.0%)
Safety and Tolerability Profile
As might be expected with a platinum- and gemcitabine-based combination, the most frequent grade 3 or higher treatment-related adverse events were hematologic. Neutropenia was reported in 57.5% of participants, anemia in 30.0% and thrombocytopenia in 22.5%. These figures point to a regimen that requires attentive blood count monitoring and supportive care, and they frame the risk-benefit discussion for any future first-line use.
Because the study was open label and reported by its investigators, the toxicity data reflect events attributed to treatment during the trial. The hematologic pattern is consistent with the intensity of a four-drug regimen, and managing it will be a central consideration as the strategy moves toward larger studies.
AI-Assisted Pathology Hints at Who Benefits Most
An unusual feature of the trial was a preplanned analysis using artificial-intelligence-powered whole-slide image evaluation. These analyses suggested that tumors with higher proportions of HER2 3+ cells were associated with greater clinical benefit from the quadruplet.
If confirmed, that signal could eventually help clinicians identify which HER2-positive patients are most likely to gain from intensified first-line therapy. For now, the finding should be treated as hypothesis-generating: it comes from a modestly sized phase 1b/2 cohort and needs validation in larger, prospectively designed datasets before it influences treatment selection.
What the Results Mean for Biliary Tract Cancer Care
The authors conclude that upfront HER2-targeted therapeutic intensification in BTC may represent a promising direction for future first-line treatment strategies, with direct relevance to ongoing phase 3 studies. The combination tested here builds on drugs already in clinical use, which could ease translation if later trials confirm the benefit.
Important caveats remain. This was an open-label phase 1b/2 trial with 40 participants, not a randomized comparison against standard first-line chemoimmunotherapy, so the results describe outcomes among treated participants rather than establishing superiority over existing care. Overall survival data are also immature, with the median not yet reached after a median 17.0 months of follow-up.
Open Questions and Next Steps
- Will the 55% response rate and 95% disease control rate hold up in randomized phase 3 testing?
- Does the regimen extend overall survival compared with standard first-line chemoimmunotherapy?
- How should HER2 status be scored, and can AI-based whole-slide analysis standardize identification of the patients most likely to benefit?
- What are the best strategies for preventing and managing grade 3 or higher neutropenia, anemia and thrombocytopenia?
- Can conversion to curative-intent surgery be reproduced, and in what proportion of patients?
For a disease in which first-line progress has been incremental, the HERBOT results provide a rationale for continuing to test HER2-directed intensification — while keeping the tolerability burden and the need for randomized confirmation firmly in view.
This article is based on reporting by Nature Medicine. Read the original article.
Originally published on nature.com
