KRAS mutations occur in approximately 20 to 25% of human cancers, with particularly high prevalence in pancreatic ductal adenocarcinoma (PDAC ~93%) and colorectal cancer (CRC ~50%). Despite curative-intent strategy and conventional locoregional therapy, recurrence is common, specifically in PDAC, where biomarker-defined minimal residual disease (MRD+) is determined by circulating tumor DNA (ctDNA) or serum tumor antigen, which indicates a significant relapse risk. KRAS mutations are fascinating immunotherapy targets because of their truncal status, necessary oncogenic role, and prevalence.
Preclinical investigations have revealed broad mKRAS-specific T-cell recognition of different HLA alleles. Conventional peptide vaccines have limited lymph node delivery, but amphiphile-modified vaccines use albumin-mediated transport to elevate the immune activation. ELI-002 2P is a lymph node-targeted amphiphile vaccine that contains KRAS G12R and G12D peptides with CpG-7909 adjuvant. It is used to stimulate both CD8+ and CD4+ T-cell responses.
The phase 1 AMPLIFY-201 trial aimed to investigate immunogenicity, safety, and preliminary clinical efficacy of ELI-002 2P in MRD+ CRC or PDAC patients after surgery and to investigate the correlation in overall survival (OS) or relapse-free survival (RFS) and mKRAS-specific T-cell response.
This multicenter, open-label, dose-escalation trial enrolled 25 patients (20 PDAC, 5 CRC) with mKRAS G12D or G12R mutations, ECOG 0 to 1, and MRD+ status by ctDNA and/or tumor markers. Patients who got six priming doses over 8 weeks followed by a booster phase after 3 months. Five adjuvant dose levels (0.1 to 10 mg) were tested with fixed peptide doses (0.7 mg each). The primary endpoint was safety. Exploratory endpoints involved biomarker clearance, radiographic RFS, OS, and immunogenicity measured by fold-change from baseline in ex vivo T-cell assays. Receiver operating characteristic (ROC) analysis identified a 9.17-fold T-cell response threshold optimally discriminating patients by outcomes. Survival analyses used Kaplan–Meier curves, hazard ratios (HR), and P-values. Correlations were assessed for T-cell responses and biomarker clearance.
After a median follow-up of 19.7 months, no new safety concerns occurred. In all patients, 84% (21/25) developed mKRAS-specific T-cell responses with 100% response at the two highest adjuvant doses. The median fold-change in T-cell response was 13.38. Seventeen patients (68%) exceeded the ROC threshold of 9.17. Above-threshold responders achieved universal biomarker reductions, including 100% ctDNA clearance (6/6).
Radiographic progression-free status was seen in 65% (11/17) of above-threshold patients versus 0% (0/8) below-threshold (relative risk = 2.96). Median OS was not reached in the above-threshold group vs 15.98 months below-threshold (HR = 0.23, P = 0.0099). Median RFS was not reached at 3.02 months (HR = 0.12, P = 0.0002). PDAC subset outcomes were mRFS 15.31 months and mOS 28.94 months, exceeding previous MRD+ PDAC standards (RFS 5 to 6.37 months, OS 17 months). Immunologically, 71% induced both CD4+ and CD8+ mKRAS-specific T cells, correlating significantly with tumor biomarker response. Cytotoxicity markers (granzyme B, perforin) were expressed in 68% of CD4+ and 84% of CD8+ T cells. Memory phenotypes persisted post-booster in 88% of evaluable patients. Antigen spreading occurred in 67% (6/9) of tested patients, expanding responses to 25% of evaluated nonvaccine neoantigens, with 83% of antigen-spreading cases above the ROC threshold.
Limitations of this study include its small sample size, nonrandomized design, absence of an external validation cohort for ROC findings, and follow-up shorter than median OS. It may lead to evolving survival estimates. Tumor tissue at relapse was not systematically collected, limiting immune microenvironment analyses. Subset analyses (e.g., G12R mutation carriers) were underpowered for definitive conclusions.
Long-term follow-up of AMPLIFY-201 demonstrates that ELI-002 2P is safe, highly immunogenic, and capable of inducing durable, polyfunctional CD4+ and CD8+ T-cell responses against mKRAS with linked biomarker clearance, delayed recurrence, and prolonged survival in MRD+ PDAC and CRC. Above-threshold mKRAS-specific T-cell induction (≥9.17-fold) was strongly correlated with improved RFS and OS, which suggests a potential immune correlate of protection.
The observed frequent antigen spreading supports the capacity of the vaccine to widen the tumor-specific immunity. These results urge further investigation in the ongoing randomized phase 2 ELI-002 7P trial with a potential application in mKRAS-expressing solid tumors.
Reference: Wainberg ZA, Weekes CD, Furqan M, et al. Lymph node-targeted, mKRAS-specific amphiphile vaccine in pancreatic and colorectal cancer: phase 1 AMPLIFY-201 trial final results. Nat Med. 2025. doi:10.1038/s41591-025-03876-4
