Novel mRNA-LNP Platform Delivers Liver-Targeted T Cell Engager for Hepatocellular Carcinoma Treatment
Key Insights
Researchers developed MLX0473 (search)-based lipid nanoparticles (LNPs) that demonstrate 7-fold higher liver-specific mRNA delivery compared to conventional Lipid5 (search)-based systems, enabling targeted therapeutic protein expression in hepatic tissue.
The mRNA-encoded bispecific T cell engager MTS105 targeting glypican-3 (search) (GPC3 (search)) and CD3 (search) achieved complete tumor regression in orthotopic hepatocellular carcinoma (search) models, with no recurrence observed during 84-day follow-up.
MTS105 treatment induced robust immune memory formation, with tumor-free mice showing resistance to rechallenge and enhanced effector memory CD8 T cell populations in both peripheral blood and spleen.
A breakthrough in liver-targeted cancer immunotherapy has emerged with the development of a novel mRNA-lipid nanoparticle (LNP) platform that delivers bispecific T cell engagers directly to hepatic tissue. Researchers have successfully engineered MLX0473 (search)-based LNPs that demonstrate superior liver-tropic delivery compared to existing systems, opening new possibilities for treating hepatocellular carcinoma (search) (HCC (search)).
Enhanced Liver-Specific Delivery Platform
The research team identified MLX0473 (search), a novel ionizable lipid that forms the basis of highly efficient liver-targeting LNPs. In vivo imaging studies revealed that MLX0473-based LNPs exhibited 7-fold higher luciferase activity in the liver compared to Lipid5 (search)-based LNP systems, which are widely used for liver-targeted mRNA delivery. The enhanced hepatic delivery was further confirmed in rats, where human erythropoietin (hEPO) mRNA encapsulated in MLX0473-LNPs showed sustained, elevated expression compared to Lipid5-based formulations after five repeated doses.
The superior performance of MLX0473 (search)-based LNPs extended beyond conventional approaches, significantly outperforming both Lipid5 (search) and GalNAc-conjugated LNP systems that rely on ASGPR receptor-mediated endocytosis for hepatic targeting.
MTS105: A Liver-Targeted Bispecific T Cell Engager
Building on this delivery platform, researchers developed MTS105, an mRNA-encoded T cell engager (TCE) designed to target HCC (search). The therapeutic combines single-chain variable fragments (ScFvs) targeting both glypican-3 (search) (GPC3 (search)), a prominent HCC antigen, and CD3 (search) on T cells, connected by a flexible peptide linker. Notably, the design omits the Fc domain to optimize the T cell stimulation window, taking advantage of the controlled release nature of mRNA-protein translation.
In vitro validation demonstrated that MTS105-encoded TCE bound both human CD3 (search) on Jurkat cells and hGPC3 on expressing HEK293 cells in a concentration-dependent manner. Functional assays revealed potent lytic activity when co-cultured with human peripheral blood mononuclear cells (PBMCs) and GPC3 (search)-positive Hepa1-6-hGPC3-luc cell lines, with efficacy equivalent to established controls including ERY974 and recombinant TCE. Importantly, no appreciable lysis of GPC3-negative MC38-luc cells was detected, confirming target-dependent T cell activation.
Remarkable Therapeutic Efficacy in Preclinical Models
The therapeutic potential of MTS105 was evaluated in an orthotopic HCC (search) model using human CD3 (search) transgenic mice. Following surgical inoculation of Hepa1-6-hGPC3-luc cells in the liver, mice received three weekly intravenous injections of MTS105 at doses of 0.05, 0.15, or 0.5 μg per mouse.
MTS105 demonstrated superior tumor penetration compared to the antibody-based control ERY974. While ERY974 did not penetrate the tumor tissue, MTS105-translated TCEs were detected within the orthotopic liver tumor, indicating enhanced therapeutic access to the target site. This tumor-specific enrichment contributed to more potent antitumor effects despite MTS105's shorter half-life due to the removal of the Fc element.
Most remarkably, MTS105 induced complete tumor regression with no recurrence observed during an 84-day follow-up period. The treatment triggered rapid intratumoral T cell infiltration and strong Granzyme B release in tumor tissue at 24 hours post-injection, with effects becoming more pronounced at 72 hours. Importantly, no body weight loss was observed over 21 days post-treatment, and MTS105-treated mice exhibited significantly lower ALT levels compared to control groups.
Immune Memory Formation and Long-Term Protection
A key advantage of the MTS105 approach was the induction of durable immune memory. Tumor-free mice from the MTS105-treated group showed complete resistance to rechallenge with Hepa1-6-hGPC3-luc cells 56 days post-tumor regression, while control mice developed uninhibited tumor growth.
Immunophenotype analysis revealed that MTS105 treatment significantly enhanced CD8 T cell populations in peripheral blood, accompanied by increased effector memory CD8 T cells and decreased naive subsets. Similar expansion of effector memory CD8 T cells was detected in the spleen, suggesting that the shift toward an effector memory phenotype contributes to the durability of MTS105's antitumor activity.
Synergistic Combination Potential
The research also demonstrated synergistic effects when MTS105 was combined with immune checkpoint inhibition. Using a suboptimal dose of MTS105 (0.15 μg/mouse) in combination with a murine anti-PD-1 (search) antibody, the combination therapy showed significantly enhanced antitumor efficacy compared to either agent as monotherapy, supporting the potential for combination approaches in clinical development.
Superior Pharmacodynamic Profile
Comparative studies with an equivalent protein-based TCE (rTCE) highlighted several key advantages of the mRNA approach. Despite less frequent dosing (once-weekly versus three times weekly for rTCE), MTS105 achieved significantly greater antitumor efficacy. Immunophenotyping revealed that MTS105 induced a higher CD8/CD4 T cell ratio in both peripheral blood and tumor tissue, while rTCE treatment led to higher PD-1 (search) expression on intratumoral T cells. Both treatments showed similar levels of activation and proliferation markers, but MTS105 increased levels of effector memory CD8 T cells in both peripheral blood and spleen.
Comprehensive Safety Profile in Non-Human Primates
Extensive safety evaluation in cynomolgus monkeys provided crucial translational data. In a 4-week repeated-dose GLP toxicology study, MTS105 demonstrated favorable pharmacokinetic properties with a time to peak plasma concentration (Tmax) of 6-9 hours after dosing, indicating rapid protein expression. The terminal elimination half-life was 13.7 ± 5.05 hours in females and 13.6 ± 0.92 hours in males, notably longer than general BiTE format TCEs such as blinatumomab.
Tissue distribution studies across mice, rats, and cynomolgus monkeys consistently showed highest TCE protein concentrations in the liver at 24 hours post-treatment, with detectable levels also found in spleen and kidney. The higher liver-to-plasma concentration ratio suggested a favorable therapeutic window for minimizing peripheral cytokine release-related adverse effects.
Safety monitoring revealed transient IL-6 level increases in all MTS105-treated groups at 24 hours post-first dose, returning to baseline by day 7. Liver and renal function biomarkers showed only transient elevations after the first dose, with all values returning to baseline levels by the second weekly dose. Histopathological analysis showed mild inflammatory cell infiltration in the liver at the end of the dosing period, with complete recovery observed by the end of the 4-week recovery period.
Clinical Translation Readiness
The comprehensive preclinical data package, including demonstrated efficacy, favorable pharmacokinetics, and acceptable safety profile in non-human primates, supports the advancement of MTS105 to first-in-human clinical trials. The liver-specific delivery approach addresses key limitations of systemic T cell engager therapies while maintaining potent antitumor activity and immune memory formation.
This innovative mRNA-LNP platform represents a significant advancement in precision cancer immunotherapy, offering the potential to transform treatment approaches for hepatocellular carcinoma (search) and potentially other liver-associated malignancies.