Highlights
– VG161, a multi‑armoured oncolytic HSV‑1 encoding IL‑12, IL‑15 and a PD‑L1 antagonist, was well tolerated and produced objective immune activation in 24 patients with advanced intrahepatic cholangiocarcinoma (ICC).
– Multiomics profiling of longitudinal tumour biopsies demonstrated antigen-presenting cell (APC) expansion, CD8+ T‑cell activation, and depletion of M2‑like macrophages; single‑cell and spatial transcriptomics nominated epithelial (Epi‑C2) and macrophage (Macro‑C1QC) subpopulations as response biomarkers.
– Clinical signals included encouraging antitumour activity in a heavily pretreated cohort and suggestive overall‑survival benefit versus historical second‑line FOLFOX; prior exposure to immune checkpoint inhibitors (CPIs) was associated with enhanced benefit.
Background: Unmet need in intrahepatic cholangiocarcinoma
Intrahepatic cholangiocarcinoma (ICC) is a biologically aggressive malignancy of the biliary epithelium with rising incidence in many regions and generally poor prognosis. Most patients present with advanced disease; systemic chemotherapy (gemcitabine‑cisplatin first line) provides modest survival benefit, and options after progression are limited. Second‑line FOLFOX has been adopted on the basis of randomized evidence for biliary tract cancers, but outcomes remain unsatisfactory for many patients. There is a pressing need for novel therapeutic strategies that produce durable responses or convert previously immunologically ‘cold’ tumours into inflamed, therapy‑sensitive microenvironments.
Therapeutic rationale for VG161
Oncolytic viruses offer a dual mechanism: selective intratumoural cytolysis plus induction of antitumour immunity through antigen release and local immune stimulation. VG161 is an engineered herpes simplex virus‑1 (HSV‑1) described as multi‑armoured because it expresses three immune‑potentiating transgenes: interleukin‑12 (IL‑12), interleukin‑15 (IL‑15), and a programmed death‑ligand 1 (PD‑L1) antagonist. IL‑12 and IL‑15 favour type‑1 immune responses, supporting CD8+ T‑cell and natural killer (NK) cell activation and memory formation, while local PD‑L1 blockade can reduce T‑cell exhaustion in the injected microenvironment. These properties provide a clear biological rationale for testing VG161 in ICC, a tumour type often characterized by immunosuppressive stroma and low baseline T‑cell infiltration.
Study design and methods (pooled analysis)
This report pools data from two multicentre clinical studies: a Phase I dose‑escalation study and a Phase IIa exploratory trial. Together, 24 patients with advanced, histologically confirmed ICC received ultrasound‑guided intratumoural injections of VG161. Patients were heavily pretreated (most receiving VG161 in third line or later); a subset had prior exposure to systemic immune checkpoint inhibitors (CPIs). Serial tumour biopsies were collected longitudinally for multiomics analyses, including bulk transcriptomics, single‑cell RNA sequencing, and spatial transcriptomics, to interrogate immune changes in the tumour microenvironment (TME). Safety, objective tumour responses, and survival outcomes were assessed; outcomes were contextualized against historical second‑line FOLFOX data to provide a hypothesis‑generating benchmark.
Key clinical findings
Safety: VG161 was generally well tolerated when administered by ultrasound‑guided intratumoural injection into hepatic lesions. Adverse events were consistent with local viral delivery and immune activation; no new safety signals precluding further development were reported in the pooled cohort.
Antitumour activity: Despite administration predominantly in third line or later, VG161 demonstrated encouraging antitumour activity across the small cohort. The pooled dataset reported objective tumour shrinkage in a subset of patients and clinical benefit in heavily pretreated individuals. The authors note an improved overall survival signal compared with historical controls treated with second‑line FOLFOX — a provocative finding given VG161 was used in later lines — though the analysis is hypothesis‑generating rather than definitive.
Interaction with prior CPI exposure: Exploratory analyses indicated patients who had previously received systemic CPIs derived enhanced benefit from VG161. This observation suggests VG161 may be particularly effective at re‑invigorating or expanding pre‑existing antitumour immunity that CPIs initially primed or partially activated.
Immune and molecular correlates from multiomics profiling
The translational strength of the pooled study lies in its longitudinal, high‑resolution tissue profiling. Key changes observed after VG161 administration included:
- Expansion and activation of antigen‑presenting cells (dendritic cells and related myeloid APC populations), consistent with enhanced tumour antigen presentation.
- Marked infiltration and activation of CD8+ T cells, with transcriptomic signatures indicating cytotoxic effector functions.
- Reduction in M2‑like, immunosuppressive tumour‑associated macrophage populations, suggesting reprogramming of suppressive myeloid compartments.
Single‑cell and spatial transcriptomics further resolved intratumoural heterogeneity and nominated cellular subpopulations associated with response or resistance: an epithelial subcluster (designated Epi‑C2) and a macrophage cluster (Macro‑C1QC). These populations correlated with differential immune cell recruitment and spatial patterns of activation, making them plausible biomarker candidates to test in subsequent studies.
Mechanistic interpretation
VG161’s transgenes provide mechanistic plausibility for the observed immune remodelling. IL‑12 drives Th1 differentiation and enhances CD8+ T‑cell and NK cell cytotoxicity; IL‑15 supports proliferation and survival of memory CD8+ T cells and NK cells; and local PD‑L1 antagonism reduces inhibitory signalling that can blunt effector T‑cell function. Intratumoural viral replication causes tumour antigen release and local inflammatory cues that together convert cold tumours into inflamed microenvironments receptive to adaptive immune attack. The depletion or reprogramming of M2‑like macrophages observed here aligns with an immunologic shift from suppressive to permissive stroma.
Clinical implications and potential pathways for development
These data support several translational strategies:
- Randomized evaluation of VG161 versus or in combination with systemic standards (e.g., chemotherapy, CPIs) in earlier lines of therapy to determine whether the signals observed here translate to meaningful, reproducible survival benefits.
- Combination regimens pairing VG161 with systemic PD‑1/PD‑L1 inhibitors or other immune‑modulating agents, since VG161 both delivers local PD‑L1 blockade and appears to synergize with previous CPI exposure.
- Prospective validation of biomarker candidates (Epi‑C2, Macro‑C1QC) to enrich for patients most likely to benefit or to monitor on‑treatment biological responses.
- Operational refinement for intratumoural delivery in liver lesions, including patient selection criteria for accessibility and safety considerations for repeated injections.
Strengths and limitations
Strengths of the pooled analysis include the integration of clinical outcomes with rich, longitudinal tissue multiomics, which permits direct linking of biological effects to clinical signals. The multicentre nature of the studies supports generalizability across treatment settings, and the inclusion of heavily pretreated patients emphasizes the therapy’s activity in a high‑need population.
Limitations are important and temper interpretation: the analysis is small (n=24) and nonrandomized, precluding definitive efficacy claims. Comparison with second‑line FOLFOX is historical rather than contemporaneous and therefore subject to selection bias and confounding. Heterogeneity in prior treatments and timing of biopsies further complicates causal inference. Finally, intratumoural delivery raises logistical considerations; durable systemic immune control will require demonstration that local therapy can produce clinically meaningful distant (abscopal) effects.
Expert commentary
VG161 represents a logical evolution in oncolytic virotherapy — combining direct oncolysis with local delivery of cytokines and checkpoint blockade to drive multi‑modal immune activation. The translational data here are compelling for early‑phase work: demonstration of APC recruitment, CD8+ activation, and macrophage reprogramming provides mechanistic evidence supporting the observed clinical signals. However, enthusiasm must be balanced with the need for rigorous randomized evaluation and biomarker validation. If validated, VG161 or similar multi‑armoured oncolytic platforms could become a useful modality in ICC where conventional systemic therapies leave an unmet need.
Conclusion
The pooled Phase I/IIa evaluation of VG161 in advanced intrahepatic cholangiocarcinoma shows that an intratumourally delivered, multi‑armoured oncolytic HSV‑1 can safely induce substantive local immune remodelling and offers early clinical signals of activity, even in a heavily pretreated population. Prior CPI exposure may augment response, and multiomics profiling has identified candidate cellular biomarkers for further study. These hypothesis‑generating results justify randomized trials to define clinical benefit, optimal combinations, and predictive biomarkers.
Funding and clinicaltrials.gov
Complete funding, sponsor, and trial registration details are reported in the primary manuscript: Shen Y et al., Gut. 2025 (gutjnl‑2025‑335904). Readers should consult the original publication for full trial identifiers and funding acknowledgements.
References
1. Shen Y, Jin X, Song W, et al. Hypothesis‑generating evaluation of multi‑armoured oncolytic HSV‑1 (VG161) in intrahepatic cholangiocarcinoma: pooled insights from multicentre studies. Gut. 2025 Sep 29:gutjnl‑2025‑335904. doi:10.1136/gutjnl‑2025‑335904.
2. Andtbacka RH, Kaufman HL, Collichio F, et al. Talimogene laherparepvec improves durable response rate in patients with advanced melanoma. J Clin Oncol. 2015;33(25):2780–2788. doi:10.1200/JCO.2014.58.3377.
3. Lamarca A, Palmer DH, Wasan HS, et al. ABC‑06: A randomized phase III trial of second‑line FOLFOX chemotherapy versus active symptom control for advanced biliary tract cancer. Lancet Oncology. 2021. [See original trial report for full citation and details]
Note
This article synthesizes and interprets the pooled findings reported by Shen et al. (Gut, 2025) and places them in clinical and mechanistic context. The conclusions herein are intended to be hypothesis‑generating and to inform clinicians and investigators considering oncolytic virotherapy approaches in biliary malignancies.