ImmuneWatch supports clinical cancer vaccine developer TREOS BIO in the analysis of peptide-specific T-cell response

MSS metastatic colorectal cancer is characterised by low immunogenicity, limited T cell infiltration, and poor response to checkpoint inhibitors. A poster from the OBERTO-301 trial by TREOS BIO, presented at ESMO GI 2026, tested whether a multi-antigen peptide vaccine could convert these immune-cold tumours into something the immune system can actually attack.

In 10 patients with paired tumour biopsies, CD8+ TIL density increased by a median of 247% after treatment with PolyPEPI1018 plus atezolizumab. TCR clusters from blood and tumour samples were annotated using ImmuneWatch DETECT to infer antigen specificity, revealing that vaccine-induced T cell clonotypes had expanded in peripheral blood and trafficked into the tumour. The immune response then spread beyond the original vaccine targets to shared tumour antigens including KRASmut, RNF43mut, NY-ESO-1, and MART1.

The ImmuneWatch team supported TREOS Bio by providing TCR sequencing and TCR analysis expertise, specifically for linking TCRs to their antigen-specificity.