Human IL7 mRNA

Local delivery of mRNA-based immunotherapies offers a promising avenue as it enables the production of specific immunomodulatory proteins that can stimulate the immune system to recognize and eliminate cancer cells while limiting systemic exposure and toxicity. Here, researchers developed and used lipid-based nanoparticles (LNPs) to deliver a mixture of mRNAs encoding the cytokines interleukin (IL)-21 and IL-7 and the immunostimulatory molecule 4-1BB ligand (triplet LNPs) into tumors. The synergistic effect of IL-21 with IL-7 and 4-1BBL resulted in a significant increase in the frequency of tumor-infiltrating CD8+ T cells and their ability to produce granzyme B and IFN-γ, leading to tumor eradication and the formation of long-term immune memory. Mechanistically, the efficacy of the triplet LNPs depended on the trafficking of tumor-draining lymph nodes to tumor CD8+ T cells. The triplet LNPs outperformed the efficacy of immune checkpoint blockade in multiple tumor models in female mice. Expression of these immunomodulators was associated with better overall survival in cancer patients.

Given the reported antitumor efficacy of IL-21, researchers first developed LNPs carrying IL-21 mRNA. After a single intratumoral injection of IL-21 LNPs, IL-21 protein levels in tumors and serum were significantly increased, which may be due to its leakage from the tumor into the blood circulation (Figure 1A, B). To enhance the efficacy of IL-21, researchers have tried to combine it with other immunostimulatory molecules with potential synergy. IL-7 has been shown to synergize with IL-21 both in vivo and in vitro to promote CD8+ T cell proliferation and cytotoxicity. 4-1BB has become an attractive immunotherapy target among other molecules such as OX40 and CD27 due to its role in enhancing CD8+ T cell survival and cytokine production. To this end, LNPs carrying IL-7 mRNA or 4-1BBL mRNA were developed, and protein levels in tumors and serum were evaluated after a single intratumoral injection (Figure 1A, C, D). Next, the researchers evaluated the efficacy of IL-21, IL-7, and 4-1BBL LNPs alone and in combination to assess their potential synergistic effects (Figure 1E, F). While IL-21 LNP monotherapy was able to inhibit MC38 tumor growth in 3 of 7 mice, IL-7 and 4-1BBL alone had no effect on tumor growth. IL-7 synergized with IL-21, leading to complete tumor regression in 5 of 7 mice (Figure 1F). In contrast, only 1 of 7 mice treated with IL-21/4-1BBL LNPs showed complete tumor regression, suggesting that its antitumor activity may be lower than that of mice treated with IL-21 alone (Figure 1F). Notably, tumor growth was delayed in mice treated with IL-7/4-1BBL LNPs compared with IL-7 and 4-1BBL monotherapy, and tumor growth was completely abolished in 1 of 7 mice (Figure 1F). More importantly, the combination of IL-21, IL-7, and 4-1BBL (i.e., triple LNP) showed the highest therapeutic effect, with complete tumor regression in 6 out of 7 mice (Figure 1F).

Figure 1. Triplet LNP eradicates tumors across multiple preclinical models. (Hamouda A E I, et al., 2024)