Abstract CT107: Durable immunogenicity of ELI-002 2P in AMPLIFY-201: Lymph node targeted mKRAS-specific amphiphile vaccine in pancreatic and colorectal cancer

Abstract Background: Colorectal cancer (CRC) and pancreatic ductal adenocarcinoma (PDAC) are the second and third leading causes of cancer death in the United States. Kirsten rat sarcoma driver mutations (mKRAS) are prevalent in CRC (52%) and PDAC (93%), making them attractive targets for immunotherapy where therapeutic options are otherwise limited. ELI-002 2P immunotherapy enhances lymph node delivery and immune responses using Amphiphile (Amph) modification of vaccine components. 84% of patients (21/25) induced mKRAS-specific T-cells post-vaccination as assessed by direct ex vivo Fluorospot and/or ICS assays with an average 58-fold increase from baseline. A balanced CD4+ and CD8+ T cell response was observed in 59% of patients. Reductions in ctDNA or serum tumor biomarker antigen from baseline were observed in 84% of patients (21/25) and 24% (6/25) had complete biomarker clearance. The induction of strong mKRAS T cell responses correlated with reductions in tumor biomarker response/clearance and relapse-free survival (RFS) in patients. Methods: ELI-002-001 is a first-in-human Phase 1 trial (NCT04853017) of ELI-002 2P cancer vaccine as adjuvant treatment for patients with high relapse-risk mKRAS+ PDAC and CRC. ELI-002 2P consists of 2 Amph-modified mKRAS peptide antigens, Amph-G12D and Amph-G12R (Amph-Peptides 2P), and an Amph-modified immune-stimulatory oligonucleotide adjuvant (Amph-CpG-7909). 25 patients received ELI-002 2P at 1.4 mg of Amph-Peptides 2P and Amph-CpG-7909 at 5 dose levels; 0.1, 0.5, 2.5, 5, and 10 mg. Peripheral blood and circulating tumor DNA (ctDNA) or serum tumor antigen were collected longitudinally to assess T cell immunogenicity and reductions in clinical biomarkers. Results: A majority of patients who received the booster immunizations maintained or increased mKRAS-specific T cell responses relative to baseline. A high frequency of polyfunctional cells secreting IFNγ, TNFα, IL-2, and/or Granzyme B was observed. CD4+ T regulatory cells were not induced after ELI-002 2P immunization. Assessment of the breadth of responses to 7 different KRAS mutations revealed broad cross-reactivity to KRAS mutants, including non-immunizing epitopes, and no responses to WT. Additional phenotypic and functional qualities were assessed. Conclusions: ELI-002 is an off-the-shelf vaccine targeting common KRAS tumor mutations demonstrating several key advantages: lymph node-targeted vaccine design, high immunogenicity, with balanced CD4+ and CD8+ T cell responses, HLA-agnostic activity, and targeting of vaccine antigens critical for tumor survival. A randomized Phase 2 clinical trial (NCT05726864) investigating a 7-peptide formulation (G12D, R, V, A, C, S, G13D) is underway. Citation Format: James R. Perry, Haley VanWyk, Amy M. Tavares, Thian Kheoh, Esther Welkowsky, Christopher M. Haqq, Peter C. DeMuth, Lisa K. McNeil. Durable immunogenicity of ELI-002 2P in AMPLIFY-201: Lymph node targeted mKRAS-specific amphiphile vaccine in pancreatic and colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT107.