Intratumoral Injection of Triplet mRNA-LNP Therapy Induces Systemic Anti-tumor Immunity

Recently, Belgian scientists published a research paper titled "Intratumoral delivery of lipid nanoparticle-formulated mRNA encoding IL-21, IL-7, and 4-1BBL induces systemic anti-tumor immunity" in Nature Communications, a subsidiary of Nature. The study developed a Triplet lipid nanoparticles (LNP) therapy, in which intratumoral injection of LNP-delivered mRNA encoding IL-21, IL-7, and 4-1BBL can induce systemic anti-tumor immune response.

IL-21 (interleukin-21) is a member of the common γ-chain cytokine family and can regulate a variety of immune cell subsets, including T cells, B cells, natural killer (NK) cells, macrophages, monocytes, and dendritic cells (DCs). In multiple preclinical tumor models, IL-21 has been shown to promote the proliferation of NK cells and T cells and regulate their effector functions, including cytotoxicity and interferon (IFN)-γ secretion, thereby inducing anti-tumor responses.

In these studies, recombinant IL-21 or oncolytic viruses expressing IL-21 are usually used. The half-life of recombinant IL-21 in mice is only 0.2 hours, and the half-life in humans is only 2 hours, which limits its therapeutic effect in clinical trials. The use of viral vectors is associated with the risk of insertion mutations and the development of anti-vector immunity, which makes repeated dosing difficult. In addition, IL-21 monotherapy cannot achieve the best therapeutic response and needs to be used in combination with chemotherapy drugs and immune checkpoint inhibitors to improve efficacy.

Local administration of mRNA encoding IL-21 is a promising alternative because mRNA is safe, short-acting, easier to manufacture, and can be administered repeatedly. In addition, mRNA encoding IL-21 can be mixed with mRNA encoding other co-immunomodulatory proteins to optimize its therapeutic effect.

IL-7 is another member of the common γ-chain cytokine family and plays a key role in the development and survival of naïve CD8+T cells and in peripheral homeostatic proliferation. IL-7 can also induce the differentiation of naïve CD8+T cells toward a memory phenotype and enhance their effector function. In the tumor microenvironment (TME), IL-7 can protect CD8+T cells from adenosine-mediated immunosuppression, thereby exerting antitumor effects. However, systemic administration of recombinant IL-7 monotherapy, despite significantly increasing circulating CD8+T cells, has no benefit in cancer patients, which may be due to the general expansion of IL-7 receptor+CD8+T cells, most of which are not tumor-specific.

4-1BB is a member of the tumor necrosis factor (TNF) receptor family and is transiently induced on CD8+ T cells after T cell receptor (TCR) stimulation. Binding of the TCR to the 4-1BB ligand (4-1BBL) initiates a signaling cascade that leads to enhanced CD8+ T cell proliferation, cytotoxic capacity, and cytokine production. Systemic administration of 4-1BB agonistic antibodies has produced encouraging antitumor responses, but its clinical efficacy has been limited by severe dose-limiting hepatotoxicity.

mRNA-based immunotherapy offers a promising approach to cancer treatment. Because it produces specific immunomodulatory proteins that stimulate the immune system to recognize and eliminate cancer cells while limiting systemic exposure and toxicity. In this new study, the research team developed LNP for the delivery of nucleoside-modified mRNA encoding IL-21, IL-7, and 4-1BBL, thereby constructing a Triplet LNP therapy. Synergy of IL-21 with IL-7 and 4-1BBL results in a significant increase in the frequency of tumor-infiltrating CD8+ T cells and their ability to produce granzyme B and IFN-γ. This results in tumor clearance and the formation of long-term immune memory, preventing tumor recurrence.

Figure 1. Intratumoral injection of Triplet LNP induces regression of distal tumors. (Hamouda A E I, et al., 2024)

Mechanistically, the effect of Triplet LNP therapy depends on the transport of tumor-draining lymph nodes to tumor CD8+ T cells. In addition, the study also verified the therapeutic potential of Triplet LNP therapy in multiple tumor models in female mice, as well as its superior therapeutic effect over immune checkpoint blockade (ICB) therapy. It can also resensitize immunotherapy-resistant tumor models to anti-PD-1 treatment. Overall, IL-21, IL-7, and 4-1BBL expression were associated with better overall survival in cancer patients.

Reference

Hamouda A E I, et al. Intratumoral delivery of lipid nanoparticle-formulated mRNA encoding IL-21, IL-7, and 4-1BBL induces systemic anti-tumor immunity. Nature communications, 2024, 15(1): 1-20.