Tumor-specific antibody cocktail treatment suppresses colorectal tumor growth in mice

Colorectal cancer (CRC) remains a leading cause of cancer-related mortality, with advanced-stage disease frequently marked by treatment resistance and recurrence. Tumor heterogeneity, driven by the accumulation of somatic mutations, undermines the efficacy of conventional therapies and limits the long-term success of targeted agents. There is an urgent need for new therapeutic strategies that can exploit, rather than be constrained by, this heterogeneity.

We developed a personalized immunotherapeutic pipeline in the syngeneic CT26 murine model of CRC. Briefly, whole exome sequencing identified mutated surface proteins (MSPs) unique to these cells. Of these MSPs, we selected 10 for the generation of MSP-specific polyclonal antibodies (pAbs). These pAbs were tested for specificity and peptide binding to peptides via ELISA, tumor tissue by immunofluorescence, and tumor cells by flow cytometry. Therapeutic efficacy was evaluated in vivo using CT26 tumor-bearing mice treated with the pAb cocktail alone or in combination with anti-PD-1 immune checkpoint blockade. To assess clinical relevance, we analyzed The Cancer Genome Atlas (TCGA) whole exome sequencing data from 100 human CRC patients for MSP prevalence and inter-patient variability.

The 10-pAb oligoclonal antibody cocktail preparations exhibited additive, high-affinity, tumor-specific binding with minimal reactivity to healthy tissues. In vivo, this pAb cocktail significantly suppressed tumor growth and, when combined with PD-1 blockade, prolonged median survival to over 90 days in treated mice compared to less than 25 days in controls. Whole exome sequence data revealed that the majority of human CRC tumors harbored 10 or more MSPs, with minimal overlap between individuals, highlighting the feasibility and necessity of personalized antibody-based therapies.

Our findings establish a proof-of-concept for individualized, mutation-guided antibody therapies, supporting further development of this approach to improve outcomes in patients with advanced CRC.