The Society for Immunotherapy of Cancer (SITC) is pleased to present scientific highlights of the latest advances emerging from the 2019 Society for Melanoma Research Congress held in Salt Lake City on Nov. 20–23, 2019.
Murine models point to melanoma differences
MULTI-MODEL PRECLINICAL PLATFORM CORRELATES MELANOMA MULTIPOTENCY AND DIFFERENTIATION STATUS WITH CLINICAL RESPONSE TO IMMUNOTHERAPY
Eva Perez-Guijarro, PhD (National Institutes of Health)
In order to develop a better understanding of the determinants of immune checkpoint blockade efficacy, Dr. Eva Perez-Guijarro (National Institutes of Health) and colleagues developed syngeneic mouse models representing the diversity of human melanomas. Each of the four murine models represented a different pathway of melanogenesis and different molecular subtype, consequently recapitulating the diverse responses to CTLA-4 immunotherapy.
Two of the preclinical models (M1 and M2) demonstrated resistance to anti-CTLA-4 immunotherapy, while models M3 and M4 were at least partially sensitive. Through analysis of genomic and transcriptomic data from these mice, along with immune cell profiles, a number of correlations were found between these data and immunotherapy responsiveness. Specifically, resistant models demonstrated high levels of T cell dysfunction and exclusion programs, including the presence of tumor-promoting macrophages. While decreased antigen presentation is a proposed mechanism of immunotherapy resistance, no evidence for disruption of this pathway was observed in any of the models in this study. A “Melanocytic Plasticity Signature (MPS)” was developed, with higher levels of this measure indicating greater multipotency and undifferentiation of the melanocytic lineage, which were enriched in non-responders. Overall, the murine MPS score developed in this study predicted patient outcome to immunotherapy, warranting further comparative analysis of additional models.
Role of fibroblasts in immunotherapy responsiveness investigated
TARGETING CANCER-ASSOCIATED FIBROBLASTS SYNERGIZES WITH ANTI-PD-1 IMMUNOTHERAPY IN ADVANCED NON-CAUCASIAN MELANOMA
Yan Kong (Peking University Cancer Hospital & Institute)
In order to improve outcomes for Chinese patients, who appear to derive less benefit from anti-PD1 therapy than Caucasian melanoma patients, Dr. Yan Kong (Peking University Cancer Hospital & Institute, Department of Renal Cancer and Melanoma) and co-workers investigated the role of cancer-associated fibroblasts (CAFs) in responses to anti-PD-1 therapies. RNA sequencing and immunohistochemical analyses were performed on patient samples (from a total of 15 patients), and testing of identified hypotheses was performed in humanized murine models.
In patient samples, a higher presence of CAFs as well as M2 macrophages and a higher peritumoral/intratumoral CAF area index ratio were associated with poorer responses to anti-PD-1 therapy. It was also observed that Wnt signaling may be able to promote the proliferation of CAFs, which in turn can trigger the epithelial-to-mesenchymal transition, as well as secrete Interleukin-6. As focal adhesion kinase (FAK) signaling has been implicated in CAF-mediated tumor growth, a FAK inhibitor (Defactinib, VS-6063) was tested in combination with anti-PD-1 therapy in the humanized mouse models, and enhanced anti-tumor efficacy was noted with this combination. Notably, enhanced T cell infiltration into tumors was also noted after this combination therapy. Therefore, the authors propose that combination treatment with a FAK inhibitor and anti-PD-1 immunotherapy may enhance outcomes for acral melanoma patients.
Neuroinflammation suppression linked to melanoma brain metastasis
MELANOMA-SECRETED AMYLOID BETA SUPPRESSES NEUROINFLAMMATION AND PROMOTES BRAIN METASTASIS
Kevin Kleffman (New York University School of Medicine)
As melanoma has the highest rate of brain metastases among all cancers, Kevin Kleffman (NYU School of Medicine) and colleagues explored the mechanisms at play in this devastating complication of metastatic cancer. In order to accomplish this, the group utilized short-term cultures (STCs) derived from patients, and analyzed these using proteomics, a variety of in vivo assays, and preclinical therapeutic models.
Marked differences were observed in the proteomic data obtained from brain and non-brain metastases STCs, including heightened presence of neuroinflammation pathways and proteins. In vivo assays demonstrated that amyloid precursor protein (APP) is essential for the development and survival of melanoma brain metastases; in particular, amyloid beta is of critical importance to this process. Loss of APP reduced brain metastases, but did not impact metastases to other sites. As amyloid beta was found to polarize astrocytes to an anti-inflammatory state, treatment of mice with a beta secretase inhibitor (initially explored for the treatment of Alzheimer’s disease) was found to reduce brain metastasis burden by allowing microglial phagocytosis of melanoma cells. The proposed pathway for brain metastases from melanoma in this study may therefore point to new therapeutic options for this advanced stage of melanoma.
Interferon signaling impacts anti-PD-1 responsiveness
DECREASED ANTIVIRAL TYPE I IFN SIGNALING IN MUCOSAL MELANOMA IS ASSOCIATED WITH RESISTANCE TO ANTI-PD-1 IMMUNOTHERAPY
Kasey Couts, PhD (University of Colorado)
Dr. Kasey Couts (University of Colorado) explored the potential underlying mechanisms of resistance to immune checkpoint blockade, particularly focusing on acral (AM) and mucosal (MM) melanomas compared to the more common cutaneous melanoma (CM). The genomic characteristics of AM and MM are quite similar; therefore, the group focused their efforts on comparing transcriptomic profiles across the subtypes through RNA sequencing to explain the differing clinical response rates of these diseases to single agent anti-PD-1 immunotherapy (CM: 52%, AM: 50%, MM: 9%).
Forty-five patient-derived melanoma xenograft models were employed for this study. Similar to their anti-PD-1 response rates, AM and CM were found to be very similar on an RNA level, while MM displayed many dysregulated genes that were enriched in immunotherapy non-responders as well, regardless of subtype. In particular, the type I IFN pathway was downregulated in these non-responders and MM tumors, with implications for both innate and adaptive immunity. Hypermethylation of IFN pathway genes is a common mechanism for this dysregulation; therefore, treatment of MM and non-responder cell lines with hypomethylating agents resulted in reduced cell viability. The importance of the transcriptomic properties of melanomas were emphasized in this study, providing potential treatment options for difficult-to-treat mucosal melanomas.
B cells may play a role in melanoma immunotherapy responsiveness
MULTI-OMIC PROFILING DEMONSTRATES IMPORTANCE OF B CELLS IN IMMUNE CHECKPOINT BLOCKADE RESPONSE
Rohit Thakur, PhD (The University of Texas MD Anderson Cancer Center)
As optimal biomarkers for response to immune checkpoint blockade have yet to be developed, Dr. Rohit Thakur (The University of Texas MD Anderson Cancer Center) and co-workers evaluated the importance of B cells in mediating responsiveness of melanomas to these therapies. Using a patient cohort from a neoadjuvant study of nivolumab combinations, the group performed a multi-omics analysis of tumor biopsies both before and during treatment to elucidate possible biomarkers and mechanisms of response.
At the bulk tissue level, expression of genes related to B cell function were enriched in responders as compared to non-responders, and immune cell signatures for B cells were predictive of response both at baseline and on-treatment (both p<0.01). Analysis of B cell receptors through bulk RNA sequencing analyses suggested clonal expansion of the B cells in responders. Mass cytometry demonstrated an abundance of activated memory and plasma(like) B cells within responders while naïve B cells were more predominant in non-responders. In a separate cohort of patients with metastatic melanoma treated with immune checkpoint blockade, increased B cell infiltration was found in responders through single-cell transcriptomic analysis, with clusters related to four properties of B cells identified: activation, metabolism, inflammation, and proliferation. Immunohistochemical analyses revealed that the B cells were predominantly found within the context of tertiary lymphoid structures. This study provides further support to the hypothesis that B cells play a critical role in immune checkpoint blockade responsiveness.
TCR/CD3 bispecific shows promise in advanced melanoma
PHARMACODYNAMIC EFFECT OF TEBENTAFUSP (TCR-CD3 BISPECIFIC) ON PERIPHERAL CYTOKINES AND ASSOCIATION WITH OS IN PATIENTS WITH ADVANCED MELANOMA
Alexander Shoushtari, MD (Memorial Sloan Kettering Cancer Center)
A phase I/II dose-finding study of tebentafusp, a TCR-CD3 bispecific, was reported by Dr. Alexander Shoushtari (Memorial Sloan Kettering Cancer Center). This agent is capable of redirecting T cells against the melanoma-associated antigen gp100, as it mimics the immune synapse formed by a natural T cell–tumor cell interaction against gp100. Eighty-four HLA-A2+ patients received treatment with tebentafusp as single agent, and serum, PBMC, and tumor samples were obtained from a subgroup of these patients both before and after treatment.
Treatment with tebentafusp induced a transient increase in cytokines inducible by IFN-gamma, and, in particular, patients with greatest increase in CXCL10 had a significantly longer overall survival, tumor shrinkage, and a greater passing reduction in CXCR3+ CD8+ T cells in the periphery. The intervention resulted in an increase of immune infiltration with CD3+, CD4+, and CD8+ cells in the tumor samples, while the expression of gp100 was unaffected. Additionally, on-treatment escalation of genes associated with the IFN-gamma pathway, immune-mediated cytotoxicity, and T cell markers was observed in responders through enrichment analysis. Tebentafusp is therefore the first soluble TCR/CD3 bispecific fusion protein to demonstrate antitumor activity in a solid tumor with additional pivotal trials ongoing.
Intrathecal administration of nivolumab demonstrates safety
SAFETY DATA FROM A SINGLE-CENTER PHASE I/IB STUDY OF CONCURRENT INTRAVENOUS (IV) AND INTRATHECAL (IT) NIVOLUMAB (N) FOR METASTATIC MELANOMA (MM) PATIENTS (PTS) WITH LEPTOMENINGEAL DISEASE (LMD)
Isabella C. Glitza Oliva, MD, PhD (The University of Texas MD Anderson Cancer Center)
Dr. Isabella Glitza Oliva (The University of Texas MD Anderson Cancer Center) presented a study of concurrent intravenous and intrathecal (IT) nivolumab therapy in melanoma patients with leptomeningeal disease (LMD). While LMD does occur across many tumor types, melanoma patients have the highest incidence of metastatic disease and survival for these patients remains extremely poor. Based on the extensive experience of the group with IT Interleukin-2, and the fact that PD-1 is expressed on the immune cells found in the CSF, the phase I/Ib study of combined intravenous and intrathecal nivolumab therapy for patients with melanoma LMD was developed after preclinical murine experiments showed no CNS toxicity from such an approach.
To date, thirteen patients have been treated on this protocol, receiving IT nivolumab Q2W at doses from 5-20 mg, and a fixed 240 mg nivolumab intravenously, for a median duration of exposure of six weeks (0-17.86 months). No adverse events of concern have been observed, with only minor events related to the IT administration of nivolumab. Therefore, the recommended IT dose of nivolumab for the expansion cohort was set at 20 mg. As the feasibility and safety of intrathecal nivolumab has thus been established, the authors aim to expand this approach to the treatment of LMD in other diseases and in combination with other therapies. In addition, the longitudinal sampling of both CSF and blood will allow for in depth translational analysis.