Abstract 6716: ALK-mRNA vaccine as a new Immunotherapy for ALK+ cancers

Abstract Anaplastic lymphoma kinase (ALK)-driven cancers, including ALK+ lymphoma and non-small cell lung cancer (NSCLC), are treated with ALK tyrosine kinase inhibitors (TKIs), yet resistance and relapse remain major challenges. Vaccine-based immunotherapy has emerged as a promising approach. Our group previously developed DNA- and peptide-based vaccines that extended survival in NSCLC mouse model. However, their clinical translation is limited. The success of SARS-CoV-2 lipid nanoparticle (LNP)-mRNA vaccines has generated interest in this platform, demonstrating effective antigen delivery and strong T-cell activation. These findings support the evaluation of a new ALK-mRNA vaccination and the direct comparison with the peptide-based strategy. We designed a codon-optimized ALK cytoplasmic domain (exons 20-29) mRNA and formulated it with LNPs using Moderna technology as standard (F#1). Two additional ionizable lipids (F#2 and F#3) were tested to assess delivery efficiency. In vitro, ALK protein expression and immunogenic peptide presentation was evaluated in 293T cells (1 µg single dose) in 293T HLA-B*07:02 cells using ALK.TCR-T cell killing assay. In vivo, 1 or 10 µg ALK-mRNA or peptide vaccine was administered intramuscularly or subcutis, respectively, in three biweekly doses in BALB/c mice. ALK-specific CD8+ and CD4+ response, T cell immunophenotypes, and anti-tumor activity were evaluated. Moreover, we tested ALK peptide presentation upon ALK-mRNA vaccination in HLA-B*07:02 transgenic model. We demonstrate that the ALK-mRNA vaccine enables the delivery of the expected ALK protein (∼65 kDa) without detectable phosphorylation, and antigen presentation was confirmed using an ALK.TCR-T cell killing assay in HLA-B*07:02 cells in vitro. In vivo, 1 or 10 µg ALK-mRNA vaccinations induced robust anti-ALK-specific CD8+ T cell responses (40-60%) against immunogenic ALK portion PGPGRVAKI in BALB/c mice, markedly surpassing peptide-based vaccines, particularly with the F#1. The 10-µg dose further elicited a CD4+ ALK-specific response by ELISPOT and promoted CD4+ and CD8+ T cell expansion with increased effector CD44+CD62- expression. Notably, both ALK-mRNA doses slowed tumor growth and extended survival in a preventive low MHC-I ALK+ lung syngeneic tumor model. Additionally, ALK-mRNA vaccine elicited superior anti-ALKRPRPSQPSSL-CD8+ responses in HLA-B*07:02 mice compared to the peptide vaccine. No adverse effects were observed. Here, we identified F#1 as the best formulation and demonstrated that ALK-mRNA vaccine induces ALK-specific CD8+ and CD4+ strong, non-toxic immune response with an effector immunophenotype in vivo. In a preventive setting, ALK vaccination delayed tumor growth in a lung MHC-I-low ALK+ model. Overall, these results outperformed the peptide vaccine and supported further investigation of the ALK-mRNA vaccine in therapeutic settings within ALK+ malignancies for a future Phase I/II clinical trial. Citation Format: Gabriele Saccu, Alessandro Gasparetto, Carmen Mecca, Elisa Bergaggio, Simone Piane, Taek-Chin Cheong, Nirmala Tilija Pun, Roberto Chiarle. ALK-mRNA vaccine as a new Immunotherapy for ALK+ cancers abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 6716.