Establishment of KRAS G12C Mutant Brain Metastasis Models for Pre-clinical Evaluation of KRAS G12C Targeted Anti-Cancer Therapy

KRAS is one of the most frequently mutated oncogenes, present in ~25% of tumours and KRAS mutations are frequent drivers in lung, colorectal and
pancreatic cancer. Clinical research has shown that ~14% of non-small cell lung cancers (NSCLCs) carry the KRAS G12C mutation. Patients with NSCLC
and the KRAS G12C mutation have an increased risk of developing brain metastases (30%); with limited treatment options, the clinical outcome for
these patients is poor. AMG 510 (Sotorasib) is a small-molecule inhibitor of KRAS G12C that specifically binds to inactive GDP-bound KRAS G12C,
preventing its oncogenic signaling. Sotorasib has been approved by the FDA for the treatment of NSCLC and recent clinical studies have demonstrated
some activity of Sotorasib against KRAS G12C NSCLC brain metastases.

ChemPartner have developed a comprehensive KRAS biochemical assay platform that includes GTP association assay, KRAS activity assay, KRAS-SOS1
and KRAS-RAF binding assays, facilitating fast and reproducible screening of new KRAS-targeted inhibitors.

To evaluate the in vivo activity of AMG 510 for NSCLC brain metastasis treatment and gain insights for developing new KRAS-targeted inhibitors, we
have also established technically challenging orthotopic models. The cell line used for inoculation was the NCI-H358-luc cell line; a non small cell lung
cancer cell line which harbors the KRAS G12C mutation. Models established include intracranial, intracarotid and intracardiac metastatic models, and
each model was validated with AMG 510 as a single agent and/or combined with radiation, a common approach in brain tumour therapy. This
approach aimed to investigate both the efficacy and the ability of AMG 510 to cross the blood-brain barrier (BBB) and target a KRAS G12C mutant
tumour. Tumour growth and metastasis was measured using bioluminescence imaging (BLI) and all animal studies adhered to AAALAC guidelines and
animal welfare regulations.

Preliminary results suggest that AMG 510 can penetrate the blood-brain barrier and demonstrate therapeutic activity against KRAS G12C metastatic
brain tumours as demonstrated using the intracarotid and intracardiac models that leave the blood-brain barrier intact. Furthermore, using the
intracranial model, we demonstrated that the combination of AMG 510 with radiation increased efficacy compared to radiation alone.

The in vivo models represent powerful tools for clinically relevant assessment of the efficacy of KRAS G12C inhibitors. The in vivo and in vitro models
can also be expanded for research on other KRAS mutations associated with brain metastases or new inhibitor development.