Abstract 1433: Acquired resistance to KRASG12C inhibitors evolves from drug tolerant cells vulnerable to AsiDNA
Authors: Jdey Wael , Dubois Aurelie , Ratel Loane , Lienafa Marie-Christine , Trochon-Joseph Veronique , Bono Francoise 
Published: July 2021

Abstract
Purpose: Mutated KRAS represents one of the most prevalent tumor-driving events in a variety of human cancers. Although there is compelling evidence that oncogenic KRAS drives tumorigenesis, efforts to target mutant KRAS have been stalled for many years. Recently, progress has been made in the development of therapeutics against KRASG12C mutation, which is present in ~15% of lung adenocarcinoma and 0-8% of other cancers. However, therapeutic resistance to KRASG12C inhibition
(KRASG12Ci) is still a clinical hurdle. Here, we describe that resistance to KRASG12Ci emerges from Drug Tolerant Cells (DTC) preventing KRASG12Ci from achieving long-term efficacy. AsiDNA is able to target specifically DTC and therefore represents a therapeutic opportunity to impede tumor progression or relapse.
Experimental design: AsiDNA is a double-stranded (DS) DNA molecule that mimics DS DNA breaks to interfere with DNA repair, by over-activating a false DNA damage signaling through DNA-PK and PARP enzymes (decoy agonist). We used continuous treatment protocols, to select resistance to KRASG12Ci Sotorasib and MRTX849 and assessed the impact of AsiDNA addition on resistance prevention and abrogation. We also addressed the mechanisms underlying the survival and evolution of the residual DTC under KRASG12Ci treatment, and how AsiDNA could impede their outgrowth.
Results: Long-term treatment of NCI-H23, Calu-1 or MIA PACA 2 cells harboring KRASG12C mutation led to acquired resistance in all independently treated populations. Addition of
AsiDNA to Sotorasib or MRTX849 completely and irreversibly abolished resistance emergence. Cloning assays showed that acquired resistance to KRASG12Ci does not occur through the selection of a pre-existing KRAS-wt or KRAS-independent sub-clones, but rather via de novo evolution of tumor cells toward a drug resistant state. We hypothesized that resistance to KRASG12Ci could occur through the evolution of remaining tumor cells through drug-tolerant dormant cells, as it's described for other targeted therapies like tyrosine kinase inhibitors. DTC are characterized by a transient senescent phenotype and evolve progressively into proliferative state. We showed that continuous treatment with KRASG12Ci lead to the emergence of a DTC-like population displaying a senescent phenotype evolving over time into proliferative cells. The co-treatment with AsiDNA and KRASG12Ci prevents DTC regrowth. This resistance prevention was also observed when adding AsiDNA during the DTC state (three to five weeks after KRASG12Ci start), indicating a DTC-dependent resistance abrogation by AsiDNA. In line with this, we showed that DTC are hyper-sensitive to AsiDNA compared to parental cells.
Conclusion: Our results provide the evidence that resistance to KRASG12Ci can evolve from DTC, and point to the therapeutic opportunity of combining AsiDNA and KRASG12Ci to overcome tumor progression or relapse.
Citation Format: Wael Jdey, Aurelie Dubois, Loane Ratel, Marie-Christine Lienafa, Veronique Trochon-Joseph, Francoise Bono. Acquired resistance to KRASG12C inhibitors evolves from drug tolerant cells vulnerable to AsiDNA [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1433.