EXTH-41. COMBINATION TREATMENT WITH RAF/MEK AND FAK INHIBITION ENHANCES TUMOR GROWTH INHIBITION IN MENINGIOMA

Abstract BACKGROUND Patients with meningiomas who have progressed after multimodal treatments face a significant shortage of viable therapeutic options. Recent advancements in the molecular understanding of meningiomas have identified the FAK and RAF/MEK signaling pathways as potential promising targets for progressive meningiomas. METHODS In vitro, we tested two human meningioma cell lines, IOMM-Lee (NF2 wild-type and CDKN2A loss) and CH157-MN (NF2 mutant). The cells were plated in Matrigel-coated wells, treated with defactinib (FAK inhibitor), VS-6766 (RAF/MEK inhibitor, avutometinib) and the combination over a 7-day period and assessed for cell viability using the CellTiter-Glo 3D assay. In vivo, we tested the efficacy of the FAK inhibitor VS-4718 (possessing favorable pharmacokinetic properties in mice) and RAF/MEK inhibitor VS-6766, both given daily via oral gavage, in athymic nude mice bearing IOMM-Lee or CH157-MN tumors. RESULTS In the matrigel assay, VS-6766 suppressed IOMM-Lee and CH157-MN cells in a dose dependent manner. The drug combination was mostly additive in IOMM-Lee cells. However, CH157-MN cells showed a strong synergistic response across all drug concentrations tested. In the IOMM-Lee flank tumor model, VS-4718 alone had no effect, while VS-6766 alone or in combination significantly reduced tumor growth and extended median survival from 25 days to 47 days (p < 0.05). In the CH157 flank tumor model, VS-4718 monotherapy did not affect tumor growth or survival, but VS-6766 monotherapy slowed tumor growth and increased median survival from 10 days to 31 days (p < 0.001). Combining both drugs further reduced tumor growth and extended median survival to 42 days (p < 0.001). CONCLUSION Treatment with FAK and RAF/MEK inhibitors showed synergistic or combination effects in the NF2 mutant CH157-MN model in vitro and in vivo. RAF/MEK inhibitor monotherapy was effective for the IOMM-Lee model (NF2 wild-type), without clear benefit of combining with the FAK inhibitor. Investigations in intracranial tumor models are underway.