Improving Immune Checkpoint Blockade Efficacy in Melanoma Brain Metastases through Myddosomal inhibition with Emavusertib

Abstract

Current advances in the treatment of melanoma brain metastases through immune checkpoint blockade and targeted therapy has significantly improved outcomes and patient survival. Yet, half of all patients continue to die from brain metastases despite use of these therapies and the addition of localized therapies like surgery and stereotactic radiosurgery. Novel treatments are needed to improve the morbidity and mortality associated with melanoma brain metastases. We have identified the inflammatory myddosomal pathway as a novel potential target of therapy in melanoma brain metastases, with gross upregulation in both tumor tissue and tumor-infiltrating immune cells. These cells display upregulation in MYD88, IRAK-1, IRAK-4, and downstream mediators of inflammatory activation at both the gene and protein level. We have previously shown the ability of the oral IRAK-4 inhibitor emavusertib (CA-4948) to penetrate the blood brain barrier and inhibit the myddosomal pathway in metastatic melanoma and primary CNS lymphoma. In this study we further show the capacity for IRAK-4 inhibition with emavusertib to improve the therapeutic efficacy of anti-PD-1 immune checkpoint blockade in melanoma brain metastases. Emavusertib in combination with anti-PD-1 therapy results in improved tumor-infiltrating lymphocyte recruitment, decreased myeloid derived suppressor cell function, and upregulation of interferon γ signaling resulting in improved survival in aggressive mouse models of melanoma brain metastases. This work supports the development of combination strategies of emavusertib with immune checkpoint blockade in melanoma brain metastases.