Survival and biomarker analyses from the OpACIN-neo and OpACIN neoadjuvant immunotherapy trials in stage III melanoma

Neoadjuvant ipilimumab plus nivolumab showed high pathologic response rates (pRRs) in patients with macroscopic stage III melanoma in the phase 1b OpACIN () and phase 2 OpACIN-neo () studies(1,2). While the results are promising, data on the durability of these pathologic responses and baseline biomarkers for response and survival were lacking. After a median follow-up of 4 years, none of the patients with a pathologic response (n = 7/9 patients) in the OpACIN study had relapsed. In OpACIN-neo (n = 86), the 2-year estimated relapse-free survival was 84% for all patients, 97% for patients achieving a pathologic response and 36% for nonresponders (P < 0.001). High tumor mutational burden (TMB) and high interferon-gamma-related gene expression signature score (IFN-gamma score) were associated with pathologic response and low risk of relapse; pRR was 100% in patients with high IFN-gamma score/high TMB; patients with high IFN-gamma score/low TMB or low IFN-gamma score/high TMB had pRRs of 91% and 88%; while patients with low IFN-gamma score/low TMB had a pRR of only 39%. These data demonstrate long-term benefit in patients with a pathologic response and show the predictive potential of TMB and IFN-gamma score. Our findings provide a strong rationale for a randomized phase 3 study comparing neoadjuvant ipilimumab plus nivolumab versus standard adjuvant therapy with antibodies against the programmed cell death protein-1 (anti-PD-1) in macroscopic stage III melanoma

Improving response and reducing toxicity to immune checkpoint blockade therapy in melanoma

Cancer immunotherapies utilizing immune checkpoint blockade (ICB) therapy targeting CTLA-4 and PD-1/PD-L1 relieve tumor-induced immune suppression and induce durable tumor regression. The use of ICB therapy have demonstrated remarkable therapeutic efficacy in a proportion of patients with melanoma. However, still a substantial percentage of patients does not respond (durable) to ICB treatment and many questions remain. Therefore, in this thesis, the aim is to improve our understanding of ICB efficacy. We demonstrate the promise of neoadjuvant ICB therapy (approach in which ICB therapy is applied before surgery) and analyze different cohorts of melanoma patients. This results in the identification of several markers that are associated with prognosis, including IFN-y related gene signature score, Batf3 dendritic cell associated gene signature score, tumor mutational burden and systemic LRG1 expression. These markers can potentially be targeted and might facilitate rational combination therapies that can boost the efficacy of ICB therapy. For this purpose, we perform a repurposing compound screen that targets antigen cross-presentation. Togethers, this work increases our understanding of factors that determine ICB therapy efficacy and toxicity, with the goal to identify novel strategies to improve outcome of melanoma patients in a rationale and personal manner. LUMC / Geneeskund

Dendritic cell-mediated cross presentation of tumor-derived peptides is biased against plasma membrane proteins

BACKGROUND: For effective tumor elimination, cytotoxic CD8(+) T cells must recognize tumor-derived antigens presented on class I major histocompatibility complex (MHC-I). Despite a general association between the expression of immunogenic antigens, typically neoantigens, and response to immunotherapy, the majority of patients lack strong endogenous responses to most putative neoantigens due to mechanisms that are not well understood. Cytotoxic CD8(+) T-cell responses are induced by dendritic cells (DCs) cross-presenting tumor-derived peptides on MHC-I. We hypothesized that cross presentation may form an unappreciated source of bias in the induction of cytotoxic T-cell responses. METHODS: We used stable isotope labeling of amino acids combined with immunopeptidomics to distinguish cross-presented from endogenous MHC-I peptides on DCs. To test impacts on T-cell activation, we targeted the model antigen SIINFEKL to specific subcellular compartments in tumor cells, which were used as sources for cross presentation to T cells. In vitro observations were validated using DNA and RNA sequencing data from two cohorts of patients with melanoma undergoing checkpoint blockade therapy. We used a novel quantitative mass spectrometry approach to measure the levels of model antigen on cross-presenting DCs following various means of tumor cell death. RESULTS: DCs exhibited a strong bias for cross-presenting peptides derived from cytoplasmic proteins and against those from plasma membrane proteins, which was confirmed using the model antigen SIINFEKL. In patients with melanoma, the proportion of membrane-derived neoantigens was correlated with reduced survival and failure to respond to therapy. Quantification of cross-presented SIINFEKL revealed that the mode of cell death could overcome DCs’ bias against plasma membrane proteins. CONCLUSIONS: Cross presentation of cellular antigens by DCs may impose constraints on the range of peptides available to activate CD8(+) T cells that have previously gone unappreciated. The share of neoantigens arising from membrane-derived sources may render some tumors less immunogenic due to inefficient cross presentation. These observations carry important implications for the encounter and intracellular processing of cellular antigens by DCs and merit further clinical studies for their therapeutic potential in stratifying patient populations and design of vaccine-based therapies

Comprehensive analysis of cutaneous and uveal melanoma liver metastases

Background The profound disparity in response to immune checkpoint blockade (ICB) by cutaneous melanoma (CM) and uveal melanoma (UM) patients is not well understood. Therefore, we characterized metastases of CM and UM from the same metastatic site (liver), in order to dissect the potential underlying mechanism in differential response on ICB. Methods Tumor liver samples from CM (n=38) and UM (n=28) patients were analyzed at the genomic (whole exome sequencing), transcriptional (RNA sequencing) and protein (immunohistochemistry and GeoMx Digital Spatial Profiling) level. Results Comparison of CM and UM metastases from the same metastatic site revealed that, although originating from the same melanocyte lineage, CM and UM differed in somatic mutation profile, copy number profile, tumor mutational burden (TMB) and consequently predicted neoantigens. A higher melanin content and higher expression of the melanoma differentiation antigen MelanA was observed in liver metastases of UM patients. No difference in B2M and human leukocyte antigen-DR (HLA-DR) expression was observed. A higher expression of programmed cell death ligand 1 (PD-L1) was found in CM compared with UM liver metastases, although the majority of CM and UM liver metastases lacked PD-L1 expression. There was no difference in the extent of immune infiltration observed between CM and UM metastases, with the exception of a higher expression of CD163 (p<0.0001) in CM liver samples. While the extent of immune infiltration was similar for CM and UM metastases, the ratio of exhausted CD8 T cells to cytotoxic T cells, to total CD8 T cells and to Th1 cells, was significantly higher in UM metastases. Conclusions While TMB was different between CM and UM metastases, tumor immune infiltration was similar. The greater dependency on PD-L1 as an immune checkpoint in CM and the identification of higher exhaustion ratios in UM may both serve as explanations for the difference in response to ICB. Consequently, in order to improve current treatment for metastatic UM, reversal of T cell exhaustion beyond programmed cell death 1 blockade should be considered.Experimentele farmacotherapi