GPC3 mRNA Vaccine Combining Locally Retained LNPs and Two Adjuvants Suppresses Tumors in Liver Cancer Models
Background: A design to strengthen immune responses to GPC3 vaccines
A study combining locally retained lipid nanoparticles (LNPs) with two immune adjuvants in a GPC3 mRNA vaccine targeting hepatocellular carcinoma reported tumor suppression. In a therapeutic setting, the vaccine formulation achieved a tumor inhibition rate of 59.9%; adding blockade of the immune checkpoint protein PD-L1 increased it to 78.3%. Tumor inhibition rates in research models should be distinguished from patient response rates or cure rates.
Glypican-3 (GPC3) is being investigated as an immunotherapy target for hepatocellular carcinoma because of its tumor-specific expression. Existing GPC3-derived peptide vaccines have been limited by a narrow range of epitopes—the antigen regions recognized by the immune system—and weak immunogenicity. This study addressed these limitations by jointly designing an antigen-delivery formulation and molecular adjuvants that bind to the antigen. The results were published in Journal of Controlled Release.
Key findings: Local expression and stronger cellular and humoral immune responses
The team screened ionizable lipids and developed L1-LNP, an L1-based delivery system. Local expression was reported to be four times that of the comparator formulation ALC-0315-LNP, while liver accumulation was reduced. These results show differences in expression and distribution associated with delivery-system composition, but reduced liver accumulation alone does not establish lower liver toxicity or fewer systemic adverse effects.
The fusion mRNA construct HGPC3C was designed to encode a protein with a heat shock protein 70 (HSP70) peptide and complement C3d positioned on opposite sides of GPC3. The two molecular adjuvants were associated with different immune markers. HSP70 was associated with stronger cellular immune responses, including increases in interferon gamma (IFN-γ) and interleukin-12p70 (IL-12p70). C3d was associated with stronger humoral immune responses, including increased interleukin-6 (IL-6) and anti-GPC3 antibody titers. The researchers interpret the findings as supporting cooperative activation of the two immune responses. The analysis does not establish that the cytokine increases directly killed cancer cells.
The formulation containing HGPC3C mRNA in L1-LNP was reported to achieve tumor inhibition rates of 80.4% in a prophylactic model and 59.9% in a therapeutic setting. In the therapeutic setting, it was reported to be significantly more effective than ALC-0315-LNP and formulations without adjuvants. With PD-L1 blockade, the inhibition rate increased to 78.3%; tumor infiltration by CD8-positive T cells and antibody production also increased. The prophylactic model and therapeutic setting differ in experimental context, so the values alone cannot establish which approach is more effective.
Implications and outlook: What must be established before clinical translation
These results provide a basis for evaluating delivery systems' local expression and distribution alongside dual-adjuvant design in GPC3 vaccine development. The researchers see potential for clinical translation in combination with immune checkpoint blockade. However, the abstract provided does not identify the species used in the model, sample size, administration route, observation period, or formula used to calculate the tumor inhibition rate. Detailed values for each control group and toxicity assessment data are also unavailable, limiting judgments about reproducibility and safety. Efficacy in patients and improved long-term survival remain to be tested separately.
Source: Article abstract indexed in Europe PMC, DOI: 10.1016/j.jconrel.2026.114992.
Glypican-3 (GPC3) is a sought-after immunotherapeutic target for hepatocellular carcinoma (HCC) due to its tumor-specific expression. However, GPC3-derived peptide vaccines suffer from limited epitope coverage and weak immunogenicity. Herein, we developed a dual-adjuvanted GPC3 mRNA vaccine delivered by local-retention lipid nanoparticles (LNPs). Through rational ionizable lipids screening, we engineered L1-based lipid nanoparticles (L1-LNPs) that achieved 4-fold greater local expression than ALC-0315-LNPs with reduced hepatic accumulation. A fusion mRNA construct (HGPC3C) encoding GPC3 flanked by two molecular adjuvants of HSP70 peptide and complement C3d was further designed. Mechanistic analyses suggested that HSP70 was associated with enhanced cellular immune responses, including elevated IFN-γ and IL-12p70, whereas C3d was associated with enhanced humoral immune responses, including increased IL-6 and anti-GPC3 antibody titers, together supporting coordinated activation of both immune arms. In prophylactic models, L1-LNPs/HGPC3C mRNA achieved 80.4% tumor suppression. In therapeutic settings, L1-LNPs/HGPC3C (59.9%) significantly outperformed ALC-0315-LNPs and non-adjuvanted formulations, validating the coordinated advantages of local delivery and dual-adjuvant design. Its combination with PD-L1 blockade further increased suppression to 78.3%, with enhanced CD8
These findings may inform studies comparing delivery-system distribution and adjuvant combinations alongside antigen design when developing GPC3-targeted mRNA vaccine candidates. Follow-up experiments could vary LNP composition and the inclusion of HSP70 and C3d while assessing local expression, liver accumulation, cellular and humoral immune markers, and tumor suppression together. The results with PD-L1 blockade also support further testing of strategies that combine vaccination with immune checkpoint blockade. More information on the models, doses, observation periods, and toxicity is needed to guide development decisions for the candidate formulation. Reduced liver accumulation does not establish safety, and tumor inhibition rates do not indicate treatment effects in patients.