Abstract LB-149: Targeting shared hotspot cancer mutations with a Listeria monocytogenes immunotherapy induce potent anti-tumor immunity
Authors: Villarreal Daniel , Coder Brandon , Armington Susan , L'Huillier Andrew , Mottershead Cristina , Filippova Elena , Thambi Nithya , Ramos Kim , Balli David , Petit Robert , Princiotta Michael 
Published: August 2018

Introduction: Virtually all tumors contain somatic mutations that can result in novel antigenic sequences that may be targeted by the host cellular immune response. Some of these mutations occur in preferential regions of specific genes commonly referred to as hotspot mutations. Hotspot mutations are commonly shared by cancer patients both within and across multiple tumor types. These hotspot mutations often confer loss or gain of function contributing to oncogenesis, which makes them promising therapeutic targets. One such mutation commonly found in several human tumor types is an aspartic acid substitution for glycine at position 12 (G12D) in KRAS. This same mutation occurs in the CT26 murine colorectal tumor model. To determine if expression of the KRAS G12D sequence in a bacterial immunotherapy vector can control tumor growth in the CT26 murine model, the Advaxis Listeria monocytogenes (Lm)-based platform was engineered to express a 21-amino acid KRAS sequence peptide containing the G12D mutation (Lm-Hot KRAS_G12D). In addition, we evaluated control of tumor growth using an ADXS-HOT construct (ADXS-503) that expresses multiple shared human hotspot and tumor-associated antigens, including the G12D KRAS. The ADXS-HOT clinical program is comprised of several Lm-based immunotherapies designed to target multiple shared hotspot and tumor-associated antigens commonly found in specific cancer types. In this study, we demonstrate control of tumor growth in a mouse model by targeting a commonly shared hotspot mutation using an Lm-based immunotherapy.

Results: We show that the Lm-HOT KRAS_G12D therapy significantly delayed tumor growth and improved long-term survival in the murine CT26 colon carcinoma model. This response was associated with an increase in the frequency of tumor infiltrating antigen-specific CD8 T cells and γδ T cells within the tumor microenvironment and a decrease in the frequency of intratumoral regulatory T cells (Tregs). Furthermore, tumor-specific CD8 T cells displayed lower expression of exhaustion markers as well as increased functionality upon restimulation. Interestingly, our proprietary ADXS-503 (a clinical ADXS-HOT construct) which includes KRAS G12D as one of its multiple targets, was also capable of significantly suppressing tumor growth in the CT26 tumor model.

Conclusion: These results suggest that our ADXS-HOT platform is a promising approach to target shared hotspot mutations. That ADXS Lm constructs targeting a single hotspot mutation can significantly control tumor growth whether it is in a single or multi-target construct. These data describe an exciting translatable discovery with the potential for broad utility across multiple tumor types and patients who share common hotspot mutations.

Citation Format: Daniel Villarreal, Brandon Coder, Susan Armington, Andrew L'Huillier, Cristina Mottershead, Elena Filippova, Nithya Thambi, Kim Ramos, David Balli, Robert Petit, Michael Princiotta. Targeting shared hotspot cancer mutations with a Listeria monocytogenes immunotherapy induce potent anti-tumor immunity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr LB-149.