Abstract 5264: KRASG12C inhibition synergizes with checkpoint blockade in KRASG12C-mutated tumor model
Authors: Hua Li , Li Shuang , Nie Chenpan , Zhang Chenfei , Bourre Ludovic , Wang Jingjing 
Published: March 2024

Introduction: The KRASG12C mutation is found in 14% of non-small cell lung cancer (NSCLC) and 3% of colorectal cancer (CRC). Sotorasib (AMG510), which covalently binds to the mutated cysteine 12 of KRASG12C protein, became the first KRASG12C inhibitors approved by the FDA for KRASG12C-mutated NSCLC treatment. AMG510 not only increased apoptosis in cancer cells harboring KRASG12C mutation, but also re-modelled tumor microenvironment. Thus, to evaluate novel therapeutic strategies for treating KRASG12C-mutated tumors, we established a CT26-KRASG12C tumor model and explored the combination of AMG510 with anti-PD1 therapy.

Methods: We knocked in KRASG12C mutation in murine CT26 colorectal cancer cells using CRISPR/Cas9 to generate CT26-KRASG12C cells. The mutation was confirmed by PCR sequencing. In vitro, CT26-KRASG12C cells were treated with AMG510 for 2h or 72h, and then p-ERK and cell viability were analyzed. In vivo, 3×105 CT26-KRASG12C cells were subcutaneously injected into BALB/c mice, and the tumor bearing mice were treated with AMG510 (30 mg/kg or 100 mg/kg, QD×21), anti-PD-1 (10 mg/kg, BIW×3) and combination of AMG510 and anti-PD-1. On day 5 after randomization, the composition of immune cells, including CD4+ T cells, CD8+ T cells, dendritic cells (DC), and natural killer (NK) cells in tumors were analyzed by flow cytometry. The mice with complete tumor regression were re-challenged with bilateral tumors of CT26-KRASG12C (3×105) and unrelated mouse breast tumor cells, 4T1 (3×105) to evaluate the effect on tumor growth.

Results: Following confirmation of KRASG12C mutation, AMG510 treatment decreased p-ERK expression by ~50% and impaired the cell growth with IC50 value of 0.1802 μM in CT26-KRASG12C cells. In vivo, single treatment of AMG510 at 30 mg/kg or 100 mg/kg significantly inhibited tumor growth with TGI of 60% or 99% on day 15 after randomization, respectively (both p&lt;0.001). Combined treatment of AMG510 (30 mg/kg or 100 mg/kg) and anti-PD-1 also led to significant tumor inhibition with TGI of 64% or 99% on the same day, respectively (both p&lt;0.001), although PD-1 blockade didn’t show anti-tumor effect alone. Noticeably, combined treatment of AMG510 (100 mg/kg) and anti-PD-1 induced complete tumor regression in 3 of 10 mice, which remained cured 124 days later. Moreover, the combined treatment significantly improved survival compared to the AMG510 treatment alone. Notably, all 4T1 tumors grew, but none of the CT26-KRASG12C tumors were palpable in the cured mice after the re-challenge. In the control group, all tumors were well established. Additionally, combined treatment of AMG510 (100mg/kg) and anti-PD-1 markedly increased the infiltration of CD4+ T cells, DC, and NK cells in the tumors.

Conclusion: The successfully established CT26-KRASG12C model is a useful tool for investigating therapeutic strategies to combine KRASG12C inhibitors with immunotherapy.

Citation Format: Li Hua, Shuang Li, Chenpan Nie, Chenfei Zhang, Ludovic Bourre, Jingjing Wang. KRASG12C inhibition synergizes with checkpoint blockade in KRASG12C-mutated tumor model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5264.