Search

Melanoma-derived brain metastases (MBM) represent an unmet clinical need because central nervous system progression is frequently an end stage of the disease. Immune checkpoint inhibitors (ICI) provide a clinical opportunity against MBM; however, the MBM tumor microenvironment (TME) has not been fully elucidated in the context of ICI. To dissect unique elements of the MBM TME and correlates of MBM response to ICI, we collected 32 fresh MBM and performed single-cell RNA sequencing of the MBM TME and T-cell receptor clonotyping on T cells from MBM and matched blood and extracranial lesions. We observed myeloid phenotypic heterogeneity in the MBM TME, most notably multiple distinct neutrophil states, including an IL8-expressing population that correlated with malignant cell epithelial-to-mesenchymal transition. In addition, we observed significant relationships between intracranial T-cell phenotypes and the distribution of T-cell clonotypes intracranially and peripherally. We found that the phenotype, clonotype, and overall number of MBM-infiltrating T cells were associated with response to ICI, suggesting that ICI-responsive MBMs interact with peripheral blood in a manner similar to extracranial lesions. These data identify unique features of the MBM TME that may represent potential targets to improve clinical outcomes for patients with MBM.

Supplementary Figure from Microenvironmental Landscape of Human Melanoma Brain Metastases in Response to Immune Checkpoint Inhibition

Supplementary Data from Microenvironmental Landscape of Human Melanoma Brain Metastases in Response to Immune Checkpoint Inhibition

Melanoma-derived brain metastases (MBM) represent an unmet clinical need because central nervous system progression is frequently an end stage of the disease. Immune checkpoint inhibitors (ICI) provide a clinical opportunity against MBM; however, the MBM tumor microenvironment (TME) has not been fully elucidated in the context of ICI. To dissect unique elements of the MBM TME and correlates of MBM response to ICI, we collected 32 fresh MBM and performed single-cell RNA sequencing of the MBM TME and T-cell receptor clonotyping on T cells from MBM and matched blood and extracranial lesions. We observed myeloid phenotypic heterogeneity in the MBM TME, most notably multiple distinct neutrophil states, including an IL8-expressing population that correlated with malignant cell epithelial-to-mesenchymal transition. In addition, we observed significant relationships between intracranial T-cell phenotypes and the distribution of T-cell clonotypes intracranially and peripherally. We found that the phenotype, clonotype, and overall number of MBM-infiltrating T cells were associated with response to ICI, suggesting that ICI-responsive MBMs interact with peripheral blood in a manner similar to extracranial lesions. These data identify unique features of the MBM TME that may represent potential targets to improve clinical outcomes for patients with MBM.

INTRODUCTION High-grade meningiomas are associated with significant neuro-cognitive morbidity and a poor prognosis. Systemic therapies, to date, have demonstrated minimal efficacy. We recently found that high-grade meningiomas harbor an immunosuppressive tumor microenvironment and that programmed cell death-ligand 1 (PD-L1) expression may contribute to the aggressive phenotype of these tumors. Therefore, we conducted a single-arm, open-label phase II trial evaluating efficacy of pembrolizumab, a PD-1 inhibitor, in a cohort of 24 patients with recurrent and progressive grade II and III meningiomas. METHODS The primary endpoint was the rate of progression-free survival at 6 months. The trial distinguished between 6-month PFS (PFS-6) rates of 26% vs. 52%. If at least 10 patients demonstrated a 6-month PFS, among the 24 patients, the agent would be considered worthy of further study. This design has at least 88% power using an exact binomial test with a one-sided significance level of 0.1. RESULTS Between November 2017 to December 2019, twenty-four patients were enrolled. The majority of the patients in our cohort were heavily pre-treated; prior to enrolling to the study, twenty patients underwent more than one surgical resection and twelve patients had received more than one round of radiotherapy. Our study met its primary endpoint and achieved a 6-month progression-free survival rate of 0.50 (90% exact CI: 0.32-0.68) and a median PFS of 8.3 months (90% CI: 4.1-12.9 months). For the twelve patients who achieved the PFS-6 primary endpoint, median PFS from the start of treatment was 17.3 months (90% CI: 9.7 – 24.3 months). Four patients had grade-3 or higher adverse events that were at least possibly treatment-related, including colitis, skin infection, encephalopathy and transaminitis. CONCLUSION Our study achieved its primary endpoint. These results suggest that pembrolizumab exerts promising activity on these tumors and results in prolonged PFS compared to historical controls.

BACKGROUND Adequate treatment options are limited for patients with meningiomas once they have exhausted surgery and radiation. As our molecular understanding of meningiomas and their progression has improved, CDK, FAK, and RAF/MEK pathways have emerged as potential avenues for therapeutic intervention. However, patient-derived cell and xenograft models of meningiomas are difficult to establish, presenting a challenge in preclinical testing and validation of new therapeutic targets. The objective of this study is to develop informative preclinical models of meningiomas and use those to evaluate the activity of potent and selective inhibitors of CDK4/6, FAK, and RAF/MEK. METHODS We used CellTiter-Glo assay to assess the anti-tumor effects of CDK4/6 inhibitor abemaciclib, FAK inhibitor defactinib (VS-6063) and dual RAF/MEK inhibitor RO5126766 (VS-6766) in BEN-MEN-1 (WHO Grade I, NF2-mutant), CH157-MN (WHO Unknown, NF2-mutant), and IOMM-Lee (WHO Grade III, CDKN2A loss) cell lines. Additionally, we used CyQUANT assays to quantify anti-proliferation activity of these inhibitors in a newly established patient-derived cell line MN14 (WHO Grade II, NF2 mutant). In parallel, we continue our attempts to establish patient-derived cell and xenograft models using freshly isolated surgical specimens of progressive meningioma. RESULTS Defactinib monotherapy significantly decreased cell viability across a 10nM-10μM range for all three established cell lines. RO5126766 showed improved efficacy (by 10-fold) in IOMM-Lee, compared to CH157-MN and Ben-Men-1. Abemaciclib showed potent effects at 10nM in IOMM-Lee and BEN-MEN-1, compared to 100nM for CH157-MN. In the MN14 patient-derived cell line, established from an NF2-mutant atypical meningioma, we observed a significant decrease in cell proliferation with defactinib. A decrease in cell proliferation was also observed with RO5126766 and abemaciclib. CONCLUSION Selective inhibitors of CDK4/6, FAK, and RAF/MEK showed anti-meningioma activity against traditional and patient-derived cell models in vitro. Molecular characterization and establishment of patient-derived models that encompass the diversity of clinical meningiomas are ongoing.

Melanoma-derived brain metastases (MBM) represent an unmet clinical need due to central nervous system (CNS) progression as a frequent, end-stage site of disease. Immune checkpoint inhibition (ICI) represents a clinical opportunity against MBM; however, the MBM tumor microenvironment (TME) has not been fully elucidated in the context of ICI. To dissect unique MBM-TME elements and correlates of MBM-ICI response, we collected 32 fresh MBM and performed single cell RNA sequencing of the MBM-TME and T cell receptor clonotyping on T cells from MBM and matched blood and extracranial lesions. We observed myeloid phenotypic heterogeneity, most notably multiple distinct neutrophil states including an IL-8 expressing population that correlated with malignant cell epithelial-to-mesenchymal transition. Additionally, we observe significant relationships between intracranial T cell phenotypes and the distribution of T cell clonotypes intracranially and peripherally. We found that the phenotype, clonotype, and overall number of MBM-infiltrating T cells were associated with response to ICI, suggesting that ICI-responsive MBMs interact with peripheral blood in a manner similar to extracranial lesions. These data demonstrate unique features of the MBM-TME, which may represent potential targets to improve clinical outcomes for patients with MBM.