Reshaping the tumor microenvironment of cold soft-tissue sarcomas with oncolytic viral therapy: a phase 2 trial of intratumoral JX-594 combined with avelumab and low-dose cyclophosphamide

Most soft-tissue sarcomas (STS) exhibit an immunosuppressive tumor microenvironment (TME), leading to resistance against immune checkpoint inhibitors (ICIs) and limited therapeutic response. Preclinical data suggest that oncolytic viral therapy can remodel the TME, facilitating T cell accumulation and enhancing the immunogenicity of these tumors.We conducted the METROMAJX, a phase II clinical trial, to investigate the combination of JX-594, an oncolytic vaccinia virus engineered for selective tumor cell replication, with metronomic cyclophosphamide and the PD-L1 inhibitor avelumab in patients with advanced, 'cold' STS, characterized by an absence of tertiary lymphoid structures. The trial employed a two-stage Simon design. JX-594 was administered intratumorally at a dose of 1.109 pfu every 2 weeks for up to 4 intra-tumoral administrations. Cyclophosphamide was given orally at 50 mg twice daily in a week-on, week-off schedule, and avelumab was administered at 10 mg/kg biweekly. The primary endpoint was the 6-month non-progression rate.Fifteen patients were enrolled, with the most frequent toxicities being grade 1 fatigue and fever. Fourteen patients were assessable for efficacy analysis. At 6 months, only one patient remained progression-free, indicating that the trial did not meet the first stage endpoint of Simon's design. Analysis of sequential tissue biopsies and plasma samples revealed an increase in CD8 density and upregulation of immune-related protein biomarkers, including CXCL10.Intra-tumoral administration of JX-594 in combination with cyclophosphamide and avelumab is safe and capable of modulating the TME in cold STS. However, the limited efficacy observed warrants further research to define the therapeutic potential of oncolytic viruses, particularly in relation to specific histological subtypes of STS.

Impact of metronomic trabectedin combined with low-dose cyclophosphamide on sarcoma microenvironment and correlation with clinical outcome: results from the TARMIC study

Soft tissue sarcomas (STS) are diverse mesenchymal tumors with few therapeutic options in advanced stages. Trabectedin has global approval for treating STS patients resistant to anthracycline-based regimens. Recent pre-clinical data suggest that trabectedin's antitumor activity extends beyond tumor cells to influencing the tumor microenvironment (TME), especially affecting tumor-associated macrophages and their pro-tumoral functions. We present the phase I/II results evaluating a combination of metronomic trabectedin and low-dose cyclophosphamide on the TME in patients with advanced sarcomas. 50 patients participated: 20 in phase I and 30 in phase II. Changes in the TME were assessed in 28 patients using sequential tumor samples at baseline and day two of the cycle. Treatment notably decreased CD68 + CD163 + macrophages in biopsies from tumor lesions compared to pre-treatment samples in 9 of the 28 patients after 4 weeks. Baseline CD8 + T cell presence increased in 11 of these patients. In summary, up to 57% of patients exhibited a positive immunological response marked by reduced M2 macrophages or increased CD8 + T cells post-treatment. This positive shift in the TME correlated with improved clinical benefit and progression-free survival. This study offers the first prospective evidence of trabectedin's immunological effect in advanced STS patients, highlighting a relationship between TME modulation and patient outcomes.This study was registered with ClinicalTrial.gov, number NCT02406781.

TROP2 Is Associated with Primary Resistance to Immune Checkpoint Inhibition in Patients with Advanced Non-Small Cell Lung Cancer

PURPOSE

Mechanisms of primary resistance to inhibitors of the programmed cell death-1 (PD-1)/programmed death-ligand 1 (PD-L1) signaling axis in non-small cell lung cancer (NSCLC) are still poorly understood. While some studies suggest the involvement of trophoblast cell surface antigen 2 (TROP2) in modulating tumor cell resistance to therapeutic drugs, its specific role in the context of PD-1/PD-L1 axis blockade is not definitively established.

EXPERIMENTAL DESIGN

We performed high-throughput analysis of transcriptomic data from 891 NSCLC tumors from patients treated with either the PD-L1 inhibitor atezolizumab or chemotherapy in two large randomized clinical trials. To confirm our results at the protein level, we complemented this transcriptional approach by performing a multiplex immunofluorescence analysis of tumor tissue samples as well as a proteomic profiling of plasma.

RESULTS

We observed a significant association of TROP2 overexpression with worse progression-free survival and overall survival on PD-L1 blockade, independent of other prognostic factors. Importantly, we found increased TROP2 expression to be predictive of survival in patients treated with atezolizumab but not chemotherapy. TROP2 overexpression was associated with decreased T-cell infiltration. We confirmed these results at the proteomic level both on tumor tissue and in plasma.

CONCLUSIONS

Our results suggest an important contribution of TROP2 expression to the primary resistance to PD-L1 blockade in NSCLC. TROP2-biomarker-based strategy may be relevant in selecting patients with NSCLC who are more likely to benefit from a combination of immunotherapy and an anti-TROP2 agent.

Deciphering the correlation between metabolic activity through 18F-FDG-PET/CT and immune landscape in soft-tissue sarcomas: an insight from the NEOSARCOMICS study

Metabolic elevation in soft-tissue sarcomas (STS), as documented with 18F-Fluorodeoxyglucose positron emission tomography (18F-FDG-PET/CT) has been linked with cell proliferation, higher grade, and lower survivals. However, the recent diagnostic innovations (CINSARC gene-expression signature and tertiary lymphoid structure [TLS]) and therapeutic innovations (immune checkpoint inhibitors [ICIs]) for STS patients underscore the need to re-assess the role of 18F-FDG-PET/CT. Thus, in this correspondence, our objective was to investigate the correlations between STS metabolism as assessed by nuclear imaging, and the immune landscape as estimated by transcriptomics analysis, immunohistochemistry panels, and TLS assessment. Based on a prospective cohort of 85 adult patients with high-grade STS recruited in the NEOSARCOMICS trial (NCT02789384), we identified 3 metabolic groups according to 18F-FDG-PET/CT metrics (metabolic-low [60%], -intermediate [15.3%] and high [24.7%]). We found that T-cells CD8 pathway was significantly enriched in metabolic-high STS. Conversely, several pathways involved in antitumor immune response, cell differentiation and cell cycle, were downregulated in extreme metabolic-low STS. Next, multiplex immunofluorescence showed that densities of CD8+, CD14+, CD45+, CD68+, and c-MAF cells were significantly higher in the metabolic-high group compared to the metabolic-low group. Lastly, no association was found between metabolic group and TLS status. Overall, these results suggest that (i) rapidly proliferating and metabolically active STS can instigate a more robust immune response, thereby attracting immune cells such as T cells and macrophages, and (ii) metabolic activity and TLS could independently influence immune responses.

Upregulation of Indoleamine 2,3-Dioxygenase 1 in Tumor Cells and Tertiary Lymphoid Structures is a Hallmark of Inflamed Non-Small Cell Lung Cancer

PURPOSE

Overexpression of the tryptophan-catabolizing enzyme indoleamine 2,3-dioxygenase 1 (IDO1) has been reported in several tumor types, including non-small cell lung cancer (NSCLC), and has been shown to promote tumor-immune evasion and inhibit T-cell activation through increased tryptophan degradation and the production of several immunosuppressive metabolites collectively known as kynurenines. However, it remains unclear whether IDO1 expression by tumor cells is detrimental specifically in the context of programmed cell death protein 1 (PD-1)/programmed death ligand 1 (PD-L1) axis blockade.

EXPERIMENTAL DESIGN

We analyzed the transcriptome of 891 NSCLC tumor samples from patients enrolled in two large randomized clinical trials investigating the safety and activity of atezolizumab, a humanized IgG1 mAb that targets PD-L1, versus docetaxel in patients with advanced NSCLC. We complemented these transcriptomics results at the protein level by using multiplex immunofluorescence and at the functional level with in vitro experiments.

RESULTS

The increased expression of the tryptophan-catabolizing enzyme IDO1 was significantly associated with improved objective response, progression-free survival, and overall survival in patients treated with PD-L1 inhibitors, but not in those treated with chemotherapy. Strikingly, inflamed tumors had higher levels of IDO1, and IDO1 was also expressed in tertiary lymphoid structures (TLS) by mature follicular dendritic cells. L-kynurenine impaired the differentiation of antibody-producing B cells induced by follicular helper T (Tfh)/B-cell interactions, a hallmark process within TLS.

CONCLUSIONS

IDO1 pathway in NSCLC is driven by the immune system rather than by tumor cells. Targeting IDO1 in combination with anti-PD-1/PD-L1 might be beneficial only in patients with inflamed tumors and particularly in those bearing TLS.

Antitumor Effects of PRMT5 Inhibition in Sarcomas

Patients with advanced soft-tissue sarcomas (STS) have few therapeutic options. Protein arginine methyltransferase 5 (PRMT5), an anticancer target, has been extensively investigated in recent years in epithelial tumors. To date, no data related to the biological role of PRMT5 inhibition and its potential effect as a treatment in STS have been reported.To investigate the therapeutic potential of PRMT5 targeting in STS, we first evaluated the prognostic value of PRMT5 expression in two different cohorts of patients with STS. We then used the potent and selective GSK3326595 (GSK595) compound to investigate the antitumor effect of the pharmacologic inhibition of PRMT5 in vitro via MTT, apoptosis, cell cycle, clonogenicity, and proliferation assays. In vivo studies were performed with two animal models to evaluate the effects of GSK595 on tumor growth. The mechanisms of action were investigated by RNA sequencing, metabolic pathway analysis, Western blotting, and glucose uptake/lactate production assays.High PRMT5 gene expression levels were significantly associated with worsened metastasis-free survival of patients with STS. GSK595 decreased the global symmetric dimethylarginine level, the proliferation rate and clonogenicity of STS cell lines in vitro and tumor growth in vivo. Moreover, PRMT5 inhibition regulated aerobic glycolysis through downregulation of key enzymes of glycolysis as well as glucose uptake and lactate production.The current study demonstrated that PRMT5 regulates STS cell metabolism and thus represents a potential therapeutic target for STS. Additional studies in diverse sarcoma subtypes will be essential to confirm and expand upon these findings.

SIGNIFICANCE

STSs have limited therapeutic options. We show here the poor prognostic value of high PRMT5 expression in STS. Moreover, we demonstrate that the pharmacologic inhibition of PRMT5 has significant antitumor activity through the downregulation of glycolysis. Our findings support the clinical investigation of PRMT5 inhibition in STSs.

Abstract 5613: Tumor glucose metabolism profiles detected via [18F]-FDG PET/CT correlate with the immune landascape in soft-tissue sarcomas

Background: Improving the assessment of the immune landscape of soft-tissue sarcoma (STS) through imaging biomarkers could help better selecting and monitoring patients that could benefit from immunotherapy. Our aim was identify whether metabolic patterns of soft-tissue sarcoma (STS) on pre-treatment 18F-Fluorodeoxyglucose (18F-FDG) positron emission tomography (PET/CT) were associated with different immune profiles on molecular and cellular levels.

Methods: This single-center prospective study included consecutive adult patients with newly-diagnosed, non-metastatic, high-grade STS treated in a curative intent with available pre-treatement 18F-FDG-PET/CT. Maximal standardized uptake value (SUVmax), SUVpeak, SUVmean, metabolic tumor volume (MTV) and total lesion glycolysis (TLG) were extracted. A cross-validated principal component analysis (PCA) was developed on the PET/CT metrics. The first two principal components (PC1 and PC2) and an unsupervised metabolic classifications were computed.

Differential gene expression (DGE), oncogenesis pathways analyses, complexity index in sarcoma (CINSARC) molecular signature and immunohistochemistry panels (CD8, CD14, CD20, CD45, CD68, c-MAF) were performed. Correlations between nuclear imaging, immunohistochemistry and transcriptomics data were achieved.

Results: 85 patients were included (median age: 62 years, 37 women) between 2016 and 2021. The robust PCA defined 3 metabolic groups (high [n=21], intermediate [n=15] and low [n=49]). PC1 reflected the tumor metabolism and PC2 the size and amount of necrosis. Transcriptomics and immunohistochemistry data were available in 32 and 31 patients, respectively. PC1 was significantly positively correlated with CINSARC (P=0.0029) and the cellular densities in CD8+, CD14+, CD45+, CD68+ and c-MAF (range of P-values: 0.0175-0.0499). The metabolic-high group was characterized by the upregulation of 13 immune pathways, including ICOS, CD27, IFNG, CXCL9-10/CXCL3 genes.

Conclusion: Metabolic profiles on 18F-FDG-PET/CT of high-grade STS highlights distinct immune profiles, which could pave the way for potential biomarkers of STS immunophenotyping.

Citation Format: Amandine Crombe, Frédéric Bertolo, Jean-Philippe Guegan, Alban Bessede, Raul Perret, Mariella Spalato-Ceruso, Maud Toulmonde, Audrey Laroche, Francois Le Loarer, Vanessa Chaire, Michèle Kind, Carlo Lucchesi, Antoine Italiano. Tumor glucose metabolism profiles detected via [18F]-FDG PET/CT correlate with the immune landascape in soft-tissue sarcomas. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5613.

Abstract 4705: Profiling of immune cell components and soluble factors in ovarian cancer ascites highlights impaired immune environment

Background: It’s now increasingly recognized that ovarian cancer (OC) ascites play a significant role in OC progression - behavior of tumor cells is influenced by the nature of their surrounding microenvironment. Thus, characterization of ascites composition is essential to understand how this milieu affects tumor progression and particularly the immunosuppressive pathways that would underlie immune response dysfunctions and, in turn, how biological ascites effects can be influenced by that composition.

Methods: Ascites samples were collected from advanced OC patients. Through respective multiplexed approaches of flow cytometry-based marker expression analysis and quantitation of mediators, immune context was profiled by investigating immune cell composition and levels of a plethora of soluble factors, including cytokines/chemokines, and metabolic pathways of some amino acids known to be involved in immunosuppression. Furthermore, ascites fluids were functionally screened for their biological effects on healthy monocytes, either undifferentiated or undergoing M1 polarization.

Results: Unlike healthy PBMCs, OC ascites were mostly “enriched” in regulatory/immunosuppressive immune cell subsets including T and myeloid populations. Also, T cells were shown to highly express immune checkpoints such as PD1 in T cells and TIGIT in Tregs. Intriguingly, a high CD4/CD8 ratio was seen. Also, CD163+ tumor-associated macrophages were shown to express CSF1R, CCR8 and CCR2, and to even display a mixed phenotype since also expressing Arg1, CD80, and iNOS. On acellular fractions, most ascites demonstrated elevated CCL18, IL6, LIF, VEGF, and CCL2 levels, and low IL2, IL4, and IL17 levels. Interestingly, unlike healthy plasmas, these ascites appeared to harbor a metabolically-immunosuppressive profile characterized by high glutaminolysis and tryptophan (Trp) degradation in kynurenine (Kyn). Functionally, we demonstrated that not only ascites basically polarized monocytes into M2 macrophages, but even antagonized with their M1 polarization to ultimately tilt to M2 status.

Conclusions: Taken together, our data show that ascites fluids most favorable to the M2 phenotype were associated with high LIF, VEGF, IL6, CCL2, and CCL18 levels, and with elevated Kyn to Trp ratios - Kyn levels being strongly higher than in healthy plasmas. Our results thus highlight a peculiar altered environment of OC ascites where a mixture of suppressive cells and signaling factors mediate extracellular cues leading to immune cell activity dysfunction. Altogether, these translational findings highlight OC ascites as a valuable tool to understand the mechanisms of suppression and develop predictive profiles, and to provide new insights for the identification of new targets and development of targeted-therapies.

Citation Format: Assia Chaibi, Coriolan Lebreton, Dominique Bodet, Jean-Philippe Guegan, Guillaume Babin, Antoine Italiano, Alban Bessede, Imane Nafia. Profiling of immune cell components and soluble factors in ovarian cancer ascites highlights impaired immune environment. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4705.

Standardized Pathology Screening of Mature Tertiary Lymphoid Structures in Cancers

Mature tertiary lymphoid structures (mTLSs) are organized lymphoid structures containing B lymphocytes admixed to CD23+ follicular dendritic cells. Their presence has been linked to improved survival and sensitivity to immune checkpoint inhibitors in several cancers, emerging as a promising pancancer biomarker. However, the requirements for any biomarker are clear methodology, proven feasibility, and reliability. In 357 patients' samples, we studied tertiary lymphoid structures (TLSs) parameters using multiplex immunofluorescence (mIF), hematoxylin-eosin-saffron (HES) staining, double CD20/CD23 staining, and single CD23 immunohistochemistry. The cohort included carcinomas (n = 211) and sarcomas (n = 146), gathering biopsies (n = 170), and surgical specimens (n = 187). mTLSs were defined as TLSs containing either a visible germinal center on HES staining or CD23+ follicular dendritic cells. Focusing on 40 TLSs assessed using mIF, double CD20/CD23 staining was less sensitive than mIF to assess maturity in 27.5% (n = 11/40) but was rescued by single CD23 staining in 90.9% (n = 10/11). In 97 patients, several samples (n = 240) were reviewed to characterize TLS distribution. The likelihood of finding TLSs in surgical material was 6.1 higher than in biopsy and 2.0 higher in primary samples than in metastasis after adjustment with a type of sample. Interrater agreement rates over 4 examiners were 0.65 (Fleiss kappa, 95% CI [0.46; 0.90]) for the presence of TLS and 0.90 for maturity (95% CI [0.83;0.99]). In this study, we propose a standardized method to screen mTLSs in cancer samples using HES staining and immunohistochemistry that can be applied to all specimens.

Phase 2 trial of intravenous oncolytic virus JX-594 combined with low-dose cyclophosphamide in patients with advanced breast cancer

Breast cancer is one the most common cause of cancer death in women worldwide. We report here the first phase II study investigating a virus genetically engineered for tumor-selective replication in patients with breast cancer. Ten patients were treated with a combination of low-dose oral cyclophosphamide and intra-venous JX-594, a thymidine kinase gene-inactivated oncolytic vaccinia virus engineered for the expression of transgenes encoding human granulocyte-macrophage colony-stimulating factor (GM-CSF) and β-galactosidase. Best response as per RECIST criteria was stable disease for 2 patients and progressive disease for 8 patients. Median progression-free and overall survival were 1.6 months (95% CI: [1.1-1.9]) and 14.4 months (95% CI: [2.0 - NA]) respectively. High throughput analysis of sequential plasma samples revealed an upregulation of protein biomarkers reflecting immune induction such as IFN gamma. Whether the combination of JX-594 with an immune checkpoint inhibitor is associated with meaningful clinical activity is therefore worth to investigate.

Pembrolizumab combined with low-dose cyclophosphamide and intra-tumoral injection of the toll-like receptor 4 agonist G100 in patients with advanced pretreated soft tissue sarcoma: results from the PEMBROSARC basket study

Soft tissue sarcomas (STS) are heterogeneous mesenchymal tumors with limited therapeutic options in the advanced setting. Immune checkpoint inhibitors have been shown to have significant clinical activity in inflamed STS which are characterized by the presence of tertiary lymphoid structures (TLS). New strategies are needed to sensitize TLS-negative STS to immunotherapy. Engagement of the toll-Like Receptor 4 (TLR4) signal pathway contributes to the development of a favorable tumor microenvironment in solid tumors. G100 is a highly potent toll-like receptor 4 (TLR4) agonist. We hypothesized that intra-tumoral G100 would induce a robust local and potentially systemic anti-tumor immune response in the microenvironment of TLS-negative sarcoma, leading to improved response to PD1 inhibition. Twenty metastatic STS patients who had a superficial injectable lesion were treated with 50 mg of cyclophosphamide (CP) orally twice daily (1 week on and 1 week off), 200 mg of pembrolizumab intravenously on day 8 of a planned 21-day cycle and G100 20 µg one weekly intra-tumoral injection for at least 6 weeks and for a maximum of 12 weeks (1st injection one week before CP administration, ie. Day -7). Biopsies and blood were collected pre and post treatment. Of the 17 patients assessable for efficacy analysis, 2 were progression-free at 6 months, and the 6-month non-progression rate was 11.8% (95% CI: 1.5–36.4), indicating that the first endpoint of the study was not reached. In 8 patients, there was an increase in T-cell infiltration into tumor after treatment. The ratio CD8/Fox-P3 + CD4 on treatment decreased in 11 cases out of 14 suggesting a predominant induction of Treg. Soluble PDL1 levels at baseline were also with adverse outcome. G100 appears to modulate the tumor microenvironment with significant infiltration of T cells. However, clinical activity in combination with PD1 inhibition was limited and no clear correlation was observed between tumor shrinkage and increased inflammation. TLR4 stimulation might have both antitumor and pro-tumor consequences.

Trial registration: This study was registered with ClinicalTrial.gov, number NCT02406781.

Prophylactic and Therapeutic Effect of Kynurenine for Experimental Autoimmune Encephalomyelitis (EAE) Disease

Background

The essential amino acid, tryptophan, is predominantly metabolised through the kynurenine pathway (KP) to generate kynurenine, an aryl-hydrocarbon receptor (AhR) pro-ligand that exerts its effects in a ligand-dependent manner. Interaction between kynurenine and the AhR is an effector mechanism of immunosuppression. We previously found that the KP is involved in multiple sclerosis (MS) disease progression. We postulated that AhR activation by kynurenine might be neuroprotective by encouraging differentiation of Tregs. In this study, we assess both the prophylactic and therapeutic efficiency of kynurenine on disease severity and progression in mice with experimental autoimmune encephalomyelitis (EAE), an MS model.

Methods

Myelin oligodendrocyte glycoprotein induced EAE mice (n = 6 per group) were treated with 200 mg/kg L-kynurenine once daily for 10 days beginning on either day 1 of EAE induction (prophylactic) or once they demonstrated motor weakness (therapeutic). Clinical disease severity measured by disease score, time on rotarod, and body weight.

Results

The prophylactic kynurenine treatment significantly (P < .0001) prevented the development of a more severe disease course with mice demonstrating diminished relapse rate and improved clinical and behavioural outcomes. However, therapeutic kynurenine did not significantly (P = .4463) decrease the clinical signs until 36 days following induction of disease; after 36 days, it also significantly (P = .0479) reduced disease relapse. Mean body weight measurements only correlated with time on rotarod (r = -.6410; P = .0007) but not clinical scores (r = .1925; P = .3674).

Conclusions

Kynurenine ameliorates EAE disease progression prophylactically and reduces relapses therapeutically. Further investigations are needed to elucidate the molecular mechanism explaining the therapeutic role of kynurenine for MS.

Circulating L-Arginine predicts the survival of cancer patients treated with immune checkpoint inhibitors

BACKGROUND

The discovery of immune checkpoint inhibitors (ICIs) has revolutionized the systemic approach to cancer treatment. However, most patients receiving ICIs do not derive benefits. Therefore, it is crucial to identify reliable predictive biomarkers of response to ICIs. One important pathway in regulating immune cell reactivity is L-arginine (ARG) metabolism, essential to T-cell activation. We therefore aimed to evaluate the association between baseline plasma ARG levels and the clinical benefit of ICIs.

PATIENTS AND METHODS

The correlation between ARG levels and clinical ICI activity was assessed by analyzing plasma samples obtained before treatment onset in two independent cohorts of patients with advanced cancer included in two institutional molecular profiling programs (BIP, NCT02534649, n = 77; PREMIS, NCT03984318, n = 296) and from patients in a phase 1 first-in-human study of budigalimab monotherapy (NCT03000257). Additionally, the correlation between ARG levels and ICI efficacy in preclinical settings was evaluated using a syngeneic mouse model of colorectal cancer responsive to ICIs. Using matched PBMC plasma samples, we analyzed the correlation between ARG levels and PBMC features through multiplexed flow cytometry analysis.

RESULTS

In both discovery and validation cohorts, low ARG levels at baseline (<42 μM) were significantly and independently associated with a worse clinical benefit rate, progression-free survival, and overall survival. Moreover, at the preclinical level, the tumor rejection rate was significantly higher in mice with high baseline ARG levels than in those with low ARG levels (85.7% versus 23.8%; P = 0.004). Finally, PBMC immunophenotyping showed that low ARG levels were significantly associated with increased PD-L1 expression in several immune cell subsets from the myeloid lineage.

CONCLUSION

We demonstrate that baseline ARG levels predict ICI response. Plasma ARG quantification may therefore represent an attractive biomarker to tailor novel therapeutic regimens targeting the ARG pathway in combination with ICIs.

Abstract 2578: High regulatory T cells infiltrate within tertiary lymphoid structure restricts response to immune checkpoint blockers in sarcomas

Background: While composition of the tumor microenvironment (TME) is a prerequisite for an effective antitumor immunity, infiltration of organized B- and T-cells aggregates called tertiary lymphoid structures (TLS) has been recently demonstrated to predict response to immune checkpoint blockers (ICB) in sarcomas. However, only a minority of patient derive benefit, suggesting the implication of additional key determinants of ICB-mediated response in TLS-positive sarcomas, such as TLS composition. Using high-throughput spatial transcriptomics and multiplex immunofluorescence (IHF), we aimed at investigating the association between TLS composition and clinical outcome to ICB.

Methods: In an exploratory cohort, we spatially profiled the expression of more than 18000-protein encoding genes from responders (R) and non-responders (NR) using Nanostring’s GeoMx Digital Spatial Profiler (DSP) Whole Transcriptome Atlas (WTA) assay. A first set of regions of interest (ROI) was selected in the TLS and further segmented in “B-cells” vs “no B-cells” areas according to CD20+ staining; a second set of ROI was selected in the tumor tissue and further segmented into “tumor” vs “stroma” areas according to CD45+ staining. Deconvolution of data was performed using SpatialDecon algorithm to estimate cell population within TLS. We then evaluated the association between immune cell composition and response to ICB in each segment. In a validation cohort, we performed multiplexed-IHF assay enabling detection of T cells (CD8/GzmA/CD4/FoxP3/CD56) and B cells. These panel was applied to whole sections baseline sarcoma samples. We investigated the association between immune cell composition and clinical benefit in term of progression-free survival (PFS) and overall survival (OS).

Results: Six patients were selected for the exploratory cohort, including 3 R and 3 NR. Among the top immune cell infiltrate within TLS segment, NR demonstrated higher Treg infiltrate versus R in “no B-cells” compartment (3.4% vs 2.0%, respectively; p=0.010), whereas no association was observed between Treg infiltration and response to ICB in both stromal (p=0.67) or tumor cells (p=0.36) compartments from tumor area. In the validation cohort (N=16), we observed that Treg density within TLS was higher in NR versus R (p=0.0059). Patients with Treg-enriched TLS had shorter PFS (2.6 vs 11.1 months, p=0.042) and OS (9.0 vs 18.3 months, p=0.12) compared to those with Treg-low TLS infiltration. Concordantly, the CTLA-4 key Treg regulator gene was upregulated in the TLS regions from NR.

Conclusions: Altogether, our findings suggest that the presence of Treg within TLS may exert a negative influence on the capacity of TLS to generate an effective antitumor immune response in sarcoma patients treated with ICB, providing new insights in understanding role of TLS in antitumor immunotherapy.

Citation Format: Florent Peyraud, Jean-Philippe Guegan, Christophe Rey, Marina Pulido, Emmanuelle Bompas, Sophie Piperno-Neumann, Christine Chevreau, Nicolas Penel, François Bertucci, Maud Toulmonde, Carine Bellera, Catherine Sautès-Fridman, Antoine Bougoüin, Coralie Cantarel, Michèle Kind, Mariella Spalato-Ceruso, Bérengère Dadone-Montaudie, Jean-Yves Blay, Wolf Herman Fridman, François Le Loarer, Alban Bessede, Antoine Italiano. High regulatory T cells infiltrate within tertiary lymphoid structure restricts response to immune checkpoint blockers in sarcomas [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2578.

Abstract 2527: Ovarian cancer ascites display altered immune environment featured by enhanced soluble factors and suppressive cellular context

Background: Tumor microenvironment (TME) of epithelial ovarian cancer is unique among solid tumors as tumor cells create their "malignant ascites" TME. These ascites, acting as a complex mixture of soluble factors and cell components, are known to be rich in macrophages which were suggested to skew to a M2-like phenotype involved in resistance and metastases. However, while macrophages can adopt different phenotypes, it's now postulated that tumor-associated macrophages (TAM) from ovarian cancer patient ascites may even acquire mixed M1/M2 properties, providing a particular pro-inflammatory and tumor-promoting microenvironment. Characterization of cell composition along with the growth factors present in the microenvironment is thus crucial to understand ovarian cancer biology and more particularly the immunosuppressive pathways that would underlie the altered immune cell activity.

Methods & Results: Through flow cytometry-based marker expression analysis and quantitation of soluble mediators in ovarian cancer ascites, we investigated here the cell component nature as well as the presence of several growth factors. While these ascites were interestingly enriched in major "immunosuppressive" cell subsets including T and myeloid populations, TAM were intriguingly shown to display a mixed phenotype characterized by high expression of CD163, unrelated to M1/M2 categorization since also expressing Arg1, CD80, and iNOS markers. The immunosuppressive phenotype was also linked to IL6, LIF and IL10 among other factors present in the ascitic environment. In order to assess their role in the occurrence of such an immunosuppressive cell status, soluble mediators were then investigated on healthy monocytes undergoing M1 polarization. We demonstrated that, while LIF did not directly affect IL6 and IL10 levels released by the cells, interestingly IL6 alone or in co-presence with LIF decreased IL6 supernatant content, with respect to the control. These changes were concomitant with a decrease and increase in the expression of CD80 and CD163, respectively. Furthermore, CD14 and CD206 were found to increase in the presence of IL6+/-LIF.

Conclusion: All these data highlight a switching activity of IL6 skewing cells from M1 polarization and resulting in a proper macrophage phenotype exhibiting a mixed M1/M2 status and would suggest these ascite-containing factors as keys conferring an immunosuppressive cell phenotype. Altogether, these translational findings highlight ovarian patient-derived ascites as a valuable tool to understand the mechanisms of suppression and to allow for the identification of novel markers to develop innovative targeted therapies.

Citation Format: Imane Nafia, Assia Chaibi, Christophe Rey, Jean-Philippe Guegan, Alban Bessede, Coriolan Lebreton, Antoine Italiano. Ovarian cancer ascites display altered immune environment featured by enhanced soluble factors and suppressive cellular context [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2527.

Abstract 1251: Low plasma Arginine level is associated with resistance to immune checkpoint blockers in patients with advanced cancer

Background: The discovery of immune checkpoint blockers (ICB) has revolutionized the systemic approach of the treatment of cancer. However, most patients receiving ICB do not derive benefit. Therefore, there is a crucial need to identify reliable predictive biomarkers of response to anti-PD-1/PD-L1 agents, both to develop precision medicine in cancer immunotherapy and to better understand mechanisms of sensitivity and resistance. One pathway that plays an important role in the regulation of immune cell reactivity is L-Arginine (Arg) metabolism, which is essential to T-cell activation. We therefore aimed at evaluating the association of baseline plasmatic level of Arg - serving as a surrogate of Arginase (Arg1) activity - and clinical benefit to ICB.

Methods: Correlation with Arg levels and efficacy of ICB in the pre-clinical setting was assessed by using a syngeneic mouse model of colorectal cancer (MC38) known to be responsive to ICB. Correlation of Arg levels and clinical activity of ICB was assessed by analyzing the plasma samples obtained before treatment onset in two independent cohorts of patient with advanced cancer and included in two institutional molecular profiling programs (discovery cohort: BIP, NCT02534649, n=77; validation cohort: PREMIS, n=295, NCT03984318). In addition, using matched PBMCs-plasma samples, we analyzed the correlation between Arg level and features of PBMCs that were captured through multiplexed-flow cytometry analysis.

Results: As expected, treatment of MC38-tumor bearing mice with anti-PD(L)1 antibodies demonstrated a strong anti-tumor effect with tumor rejection observed for app. 40% of mice (11 out of 28). The tumor rejection rate was significantly higher in mice with high baseline Arg level than in mice with low Arg level: 85.7% versus 23.8%, p=0.004. In both discovery and validation cohorts, low Arg level at baseline (42 &lt;µmol/L) was significantly associated with worse clinical benefit rate, progression-free survival (PFS) and overall survival (OS). Multivariate analysis showed that low baseline Arg level isd an independent prognostic factor for both PFS and OS. Finally, PBMCs immunophenotyping showed that low Arg level was significantly associated with increased PDL1 expression in several immune cell subsets from the myeloid lineage.

Conclusions: Altogether, our results demonstrate that baseline Arg levels are highly predictive of ICB efficacy. Increase in PDL1 expression in myeloid cells upon Arg deprivation could partly underly its suppressive activity. Plasmatic Arg quantification can therefore represent an attractive biomarker to tailor novel therapeutic regimens targeting the Arginase pathway in combination with ICB.

Citation Format: Jean-Philippe Guegan, Florent Peyraud, Aurelien Marabelle, Nathalie Chaput, Dominique Bodet, Laure Fontan, Anthony Gaultier, Imane NAFIA, Francois-Xavier Danlos, David Planchard, Caroline Robert, Caroline Even, Mohamed Khettab, Lambros Tselikas, Luc Friboulet, Jean-Charles Soria, Fabrice Andre, Fabrice Barlesi, Alban Bessede, Antoine Italiano. Low plasma Arginine level is associated with resistance to immune checkpoint blockers in patients with advanced cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1251.

Abstract 3937: PRMT5 inhibition suppress soft tissue sarcomas tumorigenicity through the regulation of glucose metabolism

Introduction: Soft tissue sarcomas (STS) are a heterogeneous group of rare tumors representing 1% of solid tumors in adults and 15% in children. Despite adequate locoregional treatment, up to 40% of patients will develop metastatic disease. Doxorubicin represents the 1st line standard of care for patients in this setting. However, its activity is limited with a response rate of only 10%, a progression-free survival of less than 6-months. New therapeutic strategies are therefore urgently needed. PRMT5 belongs to a family of enzymes that catalyze the methylation of arginine residues on both histones and non-histone proteins. Recent evidence shows that PRMT5 is upregulated in a wide variety of cancers. Its expression and activity are associated with tumorigenesis and with a decrease in patient survival in several cancers, a rationale for developing highly potent inhibitors.

Methods: We analyzed the transcriptome data from 255 translocation-related STS and 389 complex genomics STS with annotated clinical data from the French Sarcoma Group. We then investigated the anti-tumor activity of the first -in class PRMT5 specific inhibitor, GSK3226593 in a panel of 7 cell lines and in two xenograft models established at Institut Bergonié (Bordeaux, France).

Results: We found that high PRMT5 gene expression level was significantly associated with worse metastases-free survival in both translocation-related and complex genomics STS (p=0.003 and p=0.009, respectively), support the relevance of PRMT5 as a potential therapeutic target in this indication. We then found that pharmacological inhibition of PRMT5 by using GSK3226593, suppressed the viability and the cell proliferation of 7 STS cell lines in vitro (IC50 range between 0.01 and 1.4 µM) as well as in vivo in two models of xenograft cell lines. This inhibition of cell growth was concomitant with an increase of p53 and p21 expression. However, anti-tumor activity of GSK3226593 was independent of p53 since the compound was still active in shp53 expressing cell lines. Moreover, we did not notice any significant effect of GSK3226593 on cell cycle phases or apoptosis. To decipher the mechanism of action of PRMT5 inhibition in STS, we did a comparative transcriptomic analysis (RNAseq) of STS cells before and after 10 days of treatment with GSK3226593. Gene Ontology and gene set enrichment analysis revealed downregulation of metabolic processes especially glycolysis and mTORC1 pathways. A specific metabolic pathway panel was used to confirm and deepen the underlying molecular mechanism. The downregulation of several genes by GSK3226593 such as PCK2 was confirmed at the protein level by Western blot. Glycolysis inhibition was confirmed by a decrease of glucose uptake.

Conclusion: PRMT5 inhibition has anti-tumor activity in vitro and in vivo through the regulation of STS cell metabolism providing a clear rationale for its clinical investigation in this indication.

Citation Format: Stephanie Verbeke, Laura Leroy, Aurelien Bourdon, Vanessa Chaire, Elodie Richard, Jean-Philippe Guegan, Alban Bessede, Antoine Italiano. PRMT5 inhibition suppress soft tissue sarcomas tumorigenicity through the regulation of glucose metabolism [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3937.

Abstract 622: Development and characterization of a novel anti-PD1 resistant sarcoma mouse model

Background: Soft Tissue Sarcoma (STS) is known to be resistant to cancer immunotherapy including the prototypical immune checkpoint inhibitor (ICI) anti-PD1 (1). It’s therefore crucial to develop innovative strategies aiming at improving current clinical benefit. To this end, a well-characterized sarcoma preclinical model that mimics resistance to immunotherapy is needed. Starting from the anti-PD(L)1-sensitive MCA205 sarcoma mouse model, we therefore aimed at developing and characterizing a novel model resistant to anti-PD1.

Methods: Anti-PDL1 antibody was first administered to the ICI-sensitive MCA205 mouse sarcoma model (MCA205-S) and tumor growth was followed overtime. Tumor from a “non-responder” animal - tumor growth profile being similar as in the vehicle group - was then retrieved and processed for tissue dissociation and cell culture. Tumor cells were then amplified and inoculated into immunocompetent C57BL/6 mice that were exposed or not to anti-PD1 antibody, and tumor growth was monitored for a 8-week period. In addition, tumor samples from satellite animals were collected and processed for intratumoral immune landscape characterization by multiparametric flow cytometry as well as for gene expression analysis by RNA sequencing.

Results: While anti-PD1 antibody demonstrated a strong anti-tumor effect in MCA205-S tumor-bearing mice, administration of anti-PD1 to the mice inoculated with the non-responder mouse-originating MCA205 cells did not yield to a significant anti-tumor effect thereby validating the resistant profile of this new MCA205-R cell line. Flow cytometry analysis of tumor-infiltrated immune cells revealed a higher abundance of macrophages (defined as CD11b+/F4:80+) in MCA205-R when compared to the MCA205-S model, which more likely harbor a M2 phenotype. Also, anti-PD1 treatment favored an important MCA205-R tumor infiltration by gMDSC which was more limited in the MCA205-S model. Gene expression profile of tumor samples is currently under investigation.

Conclusions: We developed and validated a novel preclinical mouse model of sarcoma (MCA205-R) characterized by its resistance to anti-PD1 and a high tumor infiltration by macrophages. This model - more reflecting the clinic in terms of immunotherapy sensitivity - can thus serve to evaluate novel immunotherapeutic regimens either alone or in combination with reference ICI, to ultimately translate into clinical benefit for STS patients treated with immunotherapy.

Citation Format: Imane Nafia, Jean-Philippe Guegan, Assia Chaibi, Noëlie Bos, Doriane Bortolotto, Christophe Rey, Loïc Cerf, Florent Peyraud, Antoine Italiano, Alban Bessede. Development and characterization of a novel anti-PD1 resistant sarcoma mouse model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 622.

Indoleamine 2,3-dioxygenase 1 activation in mature cDC1 promotes tolerogenic education of inflammatory cDC2 via metabolic communication

Conventional dendritic cells (cDCs), cDC1 and cDC2, act both to initiate immunity and maintain self-tolerance. The tryptophan metabolic enzyme indoleamine 2,3-dioxygenase 1 (IDO1) is used by cDCs in maintaining tolerance, but its role in different subsets remains unclear. At homeostasis, only mature CCR7⁺ cDC1 expressed IDO1 that was dependent on IRF8. Lipopolysaccharide treatment induced maturation and IDO1-dependent tolerogenic activity in isolated immature cDC1, but not isolated cDC2. However, both human and mouse cDC2 could induce IDO1 and acquire tolerogenic function when co-cultured with mature cDC1 through the action of cDC1-derived l-kynurenine. Accordingly, cDC1-specific inactivation of IDO1 in vivo exacerbated disease in experimental autoimmune encephalomyelitis. This study identifies a previously unrecognized metabolic communication in which IDO1-expressing cDC1 cells extend their immunoregulatory capacity to the cDC2 subset through their production of tryptophan metabolite l-kynurenine. This metabolic axis represents a potential therapeutic target in treating autoimmune demyelinating diseases.

Identification of super-exhausted T cells: A novel population predictive of response to immunotherapy

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Background: Given that most of cancer patients treated with anti-PD1/PD-L1 immune checkpoint blockers (ICB) do not derive benefit, there is a crucial need to identify reliable predictive biomarker of response. Besides PD-1, several key immune checkpoints, such as CTLA4, LAG3, TIM3 and TIGIT, are associated with a T cell exhausted phenotype and play a crucial role in leading to cancer immune evasion. The impact of simultaneous expression by T cells of distinct inhibitory receptors on outcome of patients treated with ICB is still unknown. Methods: We analyzed the tissue samples, collected before ICB initiation, from patients with solid tumors and included in an institutional molecular profiling program (NCT02534649). We used multiplexed-immunohistofluorescence with the following panel CD3/PD1/TIM3/LAG3/TIGIT/CTLA4, and performed immune cell characterization using multispectral images analysis. We then investigated the correlation between coexpression of T cell-associated exhaustion markers, clinical response rate, progression-free survival (PFS) and overall survival (OS) by Cox proportional hazards models. Results: Four hundred thirty five patients were included in the analysis (NSCLC: n=207, 47.6%; sarcoma: n=42, 9.7%; urothelial: n=30, 6.9%; others: n=156, 35.9%). Digital pathology analysis allowed us to identify a population of “super-exhausted” T cells characterized by the co-expression of PD1, LAG3, TIGIT and TIM3 which was enriched in 125 cases (28.7%), and was significantly associated with better PFS (HR 1.60, CI95 1.26-2.04, p<0.001) and OS (HR 1.42, CI95 1.07-1.89, p=0.016) in the whole cohort. Patients with super-exhausted high tumors had higher objective response rate (38.4%) compared to super-exhausted low tumors (19.7%, p<0.001). The presence of super-exhausted T cells was significantly higher in responders (10%) versus non responders (4%, p<0.001). Correlation with better outcome was observed whatever the subgroup considered (NSCLC vs other tumors, CD8 T cells density and presence of tertiary lymphoid structure [TLS]). In multivariate analysis (n=372, 85.5%), increased tumor infiltration by super-exhausted T cells (>1 %) was significantly associated with better PFS (HR 0.61, CI95 0.46-0.81, p<0.001, Table) and OS (HR 0.68, CI95 0.48-0.97, p=0.033, Table). Conclusions: The presence of super-exhausted T cells may represent a new predictive biomarker of response to ICB and pave the way for the development of effective ICB combinations. Data from an independent validation cohort will be presented at the meeting. [Table: see text]

REGOMUNE: Phase II study of regorafenib plus avelumab in solid tumors—Results of the gastroenteropancreatic neuroendocrine carcinomas (GEP-NEC) cohort

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Background: There is no standard treatment for patients (pts) with advanced extra-pulmonary neuroendocrine tumors (NET) and carcinomas (NEC) after failure of chemotherapy in the metastatic setting. PD-1/PD-L1 expression is frequent in these tumors. Combining anti-PD1/PDL1 agents with anti-angiogenics has been shown to be synergistic in several tumor models. Methods: This is a single-arm open-label multicentric phase II trial assessing the efficacy and safety of regorafenib (R) (160 mg QD 3weeks/4) + Avelumab (A) (10 mg/kg every 2 weeks) combination in pts with advanced or metastatic grade 2 or 3 (G2/3) gastroenteropancreatic (GEP)-NET or GEP-NEC. The primary endpoint was the confirmed objective response rate, based on central review according to RECIST 1.1. Secondary endpoints included: 1-year progression free survival (PFS), 1-year overall survival (OS), and Safety using NCI-CTCAE v5.0. Correlative studies were planned from pts tumor samples obtained at baseline. Results: Between May 2019 and Apr. 2021, 46 pts were enrolled in 6 centers. Median age was 63 (range 31 – 80). 10 pts presented with a NEC and 36 pts with a G2/3 NET. Median follow-up was 6.5 months (95% CI: 5.3 - 9.6). Median number of previous treatment lines was: 2 (range 0 – 8). 39 (84.8%) pts experienced at least 1 dose modification or treatment interruption. The most common grade 3/4 adverse events were : Hypertension (13% of pts), fatigue (13%), and diarrhea (11%). One death was related to the treatment. Among the 42 assessable pts, 7 (16.7%) achieved a partial response: 6 pts with a G2/3 NET and 1 patient with a NEC. 22 (52.4%) pts demonstrated stable disease, 22 (52.4%) pts had tumor shrinkage and 10 (23.8%) pts had progressive disease. 3 (7.1%) pts were inevaluable as per RECIST. The median duration of response was 15.5 months (95%CI: 3.7 - not reached (NR)). The median PFS and OS were 5.5 months (95% CI: 3.6 – 9.2) and NR respectively. One year OS rate was 69.4 % (95% CI: 45.1 % – 84.5 %). Conclusions: REGOMUNE is the largest prospective study ever conducted in pts with grade 2/3 GEP-NET or GEP-NEC refractory to cytotoxic chemotherapy. The R+A combination has significant clinical activity in pts with refractory disease. Full Biomarkers analyses will be presented at the meeting. Clinical trial information: NCT03475953.

REGOMUNE: A phase II study of regorafenib plus avelumab in solid tumors—Results of the oesophageal or gastric carcinoma (OGC) cohort

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Background: Combination VEGF and PD-1/PD-L1 axis blockade has shown benefit in various tumors and is emerging as a promising combination strategy. Methods: This is a single-arm open-label multicentric phase II trial assessing the efficacy and safety of regorafenib (R) (160 mg QD 3weeks/4) + avelumab (A) (10 mg/kg every 2 weeks) combination in advanced or metastatic oesophageal or gastric carcinoma (OGC) patients (pts). The primary endpoint was the confirmed objective response rate, based on central review according to RECIST 1.1. Secondary endpoints included: 1-year progression free survival (PFS), 1-year overall survival (OS), and safety using NCI-CTCAE v5.0. Correlative studies were planned from pts tumor samples obtained at baseline. Results: Between Dec. 2018 and Mar. 2021, 49 pts were enrolled in 6 centers: 33 adenocarcinoma (ADK), 16 squamous cell carcinoma (SCC). Median age was 63.9 (range 33 – 80). Median follow-up was 14.5 months. Median number of previous treatment lines was: 2 (range 1 – 6). 29 (59.2%) pts experienced at least 1 dose modification or treatment interruption due to an adverse event related to treatment. The most common grade 3/4 adverse events were : Hypertension (12.2% of pts), palmar-plantar erythrodysesthesia syndrome (10.2%), and hypophosphatemia (8.2%). No death was related to the treatment. Among the 42 (29 ADK and 13 SCC) pts who had at least one imaging tumor assessment, 8 (19.1%) achieved a partial response, 5 (17.2%) and 3 (23.1%) in the ADK and SCC group respectively. 12 pts (28.6%) demonstrated stable disease and 22 pts (52.3%) had progressive disease. The median PFS and OS were 1.9 months (95%CI 1.8 – 3.5) and 7.5 months (95%CI 4.5 – 15.7) respectively. Conclusions: The R+A combination is associated with encouraging antitumor activity in patients with OGC. Full Biomarkers analyses will be presented at the meeting. Clinical trial information: NCT03475953.

Impact of acetaminophen on the efficacy of immunotherapy in patients with cancer

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Background: Pain is the most common symptom experienced by patients with advanced cancer. Acetaminophen (APAP, commonly known as paracetamol) alone or in combination with a weak opioid, such as codeine or tramadol, is usually considered as the first-line strategy to manage mild-to-moderate pain in this setting. Although generally considered to be safe, several evidences suggest that APAP may have negative immunomodulatory effects. Randomized studies have shown that APAP use is associated with blunted vaccine immune responses. Given its potential to impair vaccine effectiveness, the World Health Organization stated in 2015 that administration of APAP before or at the time of vaccination is not recommended. This study aimed to assess APAP impact on efficacy of immunotherapy in patients with cancer. Methods: Exposure to APAP was assessed by plasma analysis and was correlated with clinical outcome in three independent cohorts of patients with advanced cancer who were treated with immune checkpoint blockers (ICB): the CheckMate 025 trial, n = 297 (NCT01668784, sponsor: Bristol Myers Squibb), the institutional biomarker program BIP n = 34 (NCT02534649, sponsor: Institut Bergonié, Bordeaux, France) and the institutional biomarker program PREMIS n = 297 (NCT03984318, sponsor: Gustave Roussy, Villejuif, France). APAP immunomodulatory effects were evaluated on a pre-clinical tumor model (MC38) and on human peripheral blood mononuclear cells (PBMCs) from healthy donors. Results: Detectable plasma APAP levels at treatment onset was associated with a significantly worse clinical outcome in ICB-treated cancer patients (HR for progression-free survival : 1.43, 95% CI 1.07–1.91, p = 0.015; HR for overall survival: 1.78 95% CI 1.18–2.68, p = 0.006), independently of other prognostic factors (age, performance status, number of previous lines of treatment, tumor type, number of metastatic sites, presence of liver metastases, LDH levels). APAP significantly reduced ICB efficacy in the pre-clinical MC38 model, as well as the production of PD1 blockade-related interferon-γ secretion by human PBMCs. Moreover, reduction of ICB efficacy in vivo was associated with significantly increased tumor infiltration by regulatory T cells (Tregs). Administration of APAP over 24 h induced a significant expansion of peripheral Tregs in healthy individuals. In addition, interleukin-10, a crucial mediator of Treg-induced immune suppression, was significantly upregulated upon treatment with ICB in cancer patients taking APAP. Conclusions: This study provides strong pre-clinical and clinical evidence of the role of APAP as a potential suppressor of antitumor immunity. Hence, APAP should be used with caution in patients treated with ICB.

Impact of acetaminophen on the efficacy of immunotherapy in cancer patients

BACKGROUND

Acetaminophen (APAP) use has been associated with blunted vaccine immune responses. This study aimed to assess APAP impact on immunotherapy efficacy in patients with cancer.

PATIENTS AND METHODS

Exposure to APAP was assessed by plasma analysis and was correlated with clinical outcome in three independent cohorts of patients with advanced cancer who were treated with immune checkpoint blockers (ICB). APAP immunomodulatory effects were evaluated on a pre-clinical tumor model and on human peripheral blood mononuclear cells (PBMCs) from healthy donors.

RESULTS

Detectable plasma APAP levels at treatment onset was associated with a significantly worse clinical outcome in ICB-treated cancer patients, independently of other prognostic factors. APAP significantly reduced ICB efficacy in the pre-clinical MC38 model, as well as the production of PD1 blockade-related interferon-γ secretion by human PBMCs. Moreover, reduction of ICB efficacy in vivo was associated with significantly increased tumor infiltration by regulatory T cells (Tregs). Administration of APAP over 24 h induced a significant expansion of peripheral Tregs in healthy individuals. In addition, interleukin-10, a crucial mediator of Treg-induced immune suppression, was significantly upregulated upon treatment with ICB in cancer patients taking APAP.

CONCLUSION

This study provides strong pre-clinical and clinical evidence of the role of APAP as a potential suppressor of antitumor immunity. Hence, APAP should be used with caution in patients treated with ICB.

Pembrolizumab in soft-tissue sarcomas with tertiary lymphoid structures: a phase 2 PEMBROSARC trial cohort

Immune checkpoint inhibitors (ICIs) show limited clinical activity in patients with advanced soft-tissue sarcomas (STSs). Retrospective analysis suggests that intratumoral tertiary lymphoid structures (TLSs) are associated with improved outcome in these patients. PEMBROSARC is a multicohort phase 2 study of pembrolizumab combined with low-dose cyclophosphamide in patients with advanced STS (NCT02406781). The primary endpoint was the 6-month non-progression rate (NPR). Secondary endpoints included objective response rate (ORR), progression-free survival (PFS), overall survival (OS) and safety. The 6-month NPR and ORRs for cohorts in this trial enrolling all comers were previously reported; here, we report the results of a cohort enrolling patients selected based on the presence of TLSs (n = 30). The 6-month NPR was 40% (95% confidence interval (CI), 22.7-59.4), so the primary endpoint was met. The ORR was 30% (95% CI, 14.7-49.4). In comparison, the 6-month NPR and ORR were 4.9% (95% CI, 0.6-16.5) and 2.4% (95% CI, 0.1-12.9), respectively, in the all-comer cohorts. The most frequent toxicities were grade 1 or 2 fatigue, nausea, dysthyroidism, diarrhea and anemia. Exploratory analyses revealed that the abundance of intratumoral plasma cells (PCs) was significantly associated with improved outcome. These results suggest that TLS presence in advanced STS is a potential predictive biomarker to improve patients' selection for pembrolizumab treatment.

Spatial transcriptomics of macrophage infiltration in non-small cell lung cancer reveals determinants of sensitivity and resistance to anti-PD1/PD-L1 antibodies

BACKGROUND

Tumor-associated macrophages (TAMs) having immunosuppressive properties are one of the most abundant immune cells in the tumor microenvironment (TME). Preclinical studies have highlighted the potential role of TAMs in resistance to immune checkpoint blockers (ICBs). Here, we investigated the predictive value of TAM infiltration in patients with non-small cell lung cancer (NSCLC) treated with ICBs and characterized their transcriptomic profiles.

METHODS

Tumor samples were collected from 152 patients with NSCLC before ICB treatment onset. After immunohistochemical staining and image analysis, the correlation between CD163+ cell infiltration and survival was analyzed. Spatial transcriptomic analyses were performed using the NanoString GeoMx Immune Pathways assay to compare the gene expression profile of tumors with high or low levels of CD163+ cell infiltration and to identify determinants of response to ICBs in tumors with high CD163+ infiltration.

RESULTS

Low intratumoral CD163+ cell infiltration was associated with longer progression-free survival (PFS; HR 0.61, 95% CI 0.40 to 0.94, p=0.023) and overall survival (OS; HR 0.48, 95% CI 0.28 to 0.80, p=0.004) under ICB treatment. Spatial transcriptomic profiles of 16 tumors revealed the upregulation of ITGAM, CD27, and CCL5 in tumors with high CD163+ cell infiltration. Moreover, in tumors with high macrophage infiltration, the upregulation of genes associated with the interferon-γ signaling pathway and the M1 phenotype was associated with better responses under immunotherapy. Surprisingly, we found also a significantly higher expression of CSF1R in the tumors of responders. Analysis of three independent data sets confirmed that high CSF1R expression was associated with an increased durable clinical benefit rate (47% vs 6%, p=0.004), PFS (median 10.89 months vs 1.67 months, p=0.001), and OS (median 23.11 months vs 2.66 months, p<0.001) under ICB treatment.

CONCLUSIONS

Enrichment of TAMs in the TME of NSCLC is associated with resistance to immunotherapy regardless of the programmed death ligand 1 status and is driven by upregulation of CD27, ITGAM, and CCL5 gene expression within the tumor compartment. Our transcriptomic analyses identify new potential targets to alter TAM recruitment/polarization and highlight the complexity of the CSF1R pathway, which may not be a suitable target to improve ICB efficacy.

Targeting Tryptophan Catabolism in Cancer Immunotherapy Era: Challenges and Perspectives

Metabolism of tryptophan (Trp), an essential amino acid, represent a major metabolic pathway that both promotes tumor cell intrinsic malignant properties as well as restricts antitumour immunity, thus emerging as a drug development target for cancer immunotherapy. Three cytosolic enzymes, namely indoleamine 2,3-dioxygenase 1 (IDO1), IDO2 and tryptophan 2,3-dioxygenase (TDO2), catalyzes the first-rate limiting step of the degradation of Trp to kynurenine (Kyn) and modulates immunity toward immunosuppression mainly through the aryl hydrocarbon receptor (AhR) activation in numerous types of cancer. By restoring antitumor immune responses and synergizing with other immunotherapies, the encouraging preclinical data of IDO1 inhibitors has dramatically failed to translate into clinical success when combined with immune checkpoints inhibitors, reigniting the debate of combinatorial approach. In this review, we i) provide comprehensive evidences on immunomodulatory role of the Trp catabolism metabolites that highlight this pathway as relevant target in immuno-oncology, ii)ii) discuss underwhelming results from clinical trials investigating efficacy of IDO1 inhibitors and underlying mechanisms that might have contributed to this failure, and finally, iii) discuss the current state-of-art surrounding alternative approaches of innovative antitumor immunotherapies that target molecules of Trp catabolism as well as challenges and perspectives in the era of immunotherapy.

Regorafenib-avelumab combination in patients with biliary tract cancer (REGOMUNE): a single-arm, open-label, phase II trial

BACKGROUND

Regorafenib has shown substantial clinical activity in patients with advanced biliary tract cancers (BTCs). Preclinical data suggested that this drug modulates antitumour immunity and is synergistic with immune checkpoint inhibition.

PATIENTS AND METHODS

This is a single-arm, multicentric phase II trial. Regorafenib was given 3 weeks/4, 160 mg quaque die (once a day) (QD); avelumab 10 mg/kg IV was given every two weeks, beginning at C1D15 until progression or unacceptable toxicity. The primary end-point was the confirmed objective response rate under treatment, as per Response Evaluation Criteria in Solid Tumours 1.1. The secondary end-points included the following: 1-year non-progression rate; progression-free survival (PFS) and overall survival; safety and biomarkers studies performed on sequential tumour samples obtained at baseline and at cycle 2 day 1.

RESULTS

Thirty-four patients were enrolled in four centres. Twenty-nine patients were assessable for efficacy after central radiological review. The best response was partial response for four patients (13.8%), stable disease for 11 patients (37.9%) and progressive disease for 14 patients (48.3%). The median PFS and overall survival were 2.5 months (95% confidence interval [CI] [1.9-5.5]) and 11.9 months (95%CI [6.2-NA]) respectively. The most common grade 3 or 4 clinical adverse events related to treatment were hypertension (17.6%), fatigue (14.7%) and maculopapular rash (11.8%). High baseline levels of programmed cell death ligand 1 and of indoleamine 2, 3-dioxygénase expression were associated with improved outcomes.

CONCLUSIONS

Regorafenib combined with avelumab has antitumour activity in a subset of heavily pretreated biliary tract cancer population. Further investigations are needed in patients selected based on tumour microenvironment features.

CLINICAL TRIAL REGISTRATION

NCT03475953.

Trabectedin plus durvalumab in patients with advanced pretreated soft tissue sarcoma and ovarian carcinoma (TRAMUNE): an open-label, multicenter phase Ib study

PURPOSE

Trabectedin has shown pre-clinical synergy with immune-checkpoint inhibitors in pre-clinical models.

EXPERIMENTAL DESIGN

TRAMUNE is a phase Ib study investigating trabectedin combined with durvalumab trough a dose-escalation phase and two expansion cohorts (soft tissue sarcoma and ovarian carcinoma). Trabectedin was given at three dose levels (1 mg/m2, 1.2 mg/m2 and 1.5 mg/m2) on day 1, in combination with durvalumab, 1120 mg on day 2, every 3 weeks. The primary endpoints were the recommended phase II dose (RP2D) of trabectedin combined with durvalumab and the objective response rate (ORR) as per RECIST 1.1. The secondary endpoints included safety, 6-month progression-free rate (PFR), progression-free survival (PFS), overall survival, and biomarker analyses.

RESULTS

40 patients were included (dose escalation: n=9; STS cohort: n=16; ovarian cohort: n=15, 80% platinum resistant/refractory). The most frequent toxicities were grade 1-2 fatigue, nausea, neutropenia, and alanine/aspartate aminotransferase increase. One patient experienced a dose-limiting toxicity at dose level 2. Trabectedin at 1.2 mg/m2 was selected as the RP2D. In the STS cohort, 43% of patients experienced tumor shrinkage, the ORR was 7% (95% CI 0.2 - 33.9) and the 6-month PFR 28.6% (95% CI 8.4-58.1). In the ovarian carcinoma cohort, 43% of patients experienced tumor shrinkage, the ORR was 21.4% (95% CI 4.7 - 50.8) and the 6-month PFR 42.9% (95% CI 17.7 - 71.1). Baseline levels of PD-L1 expression and CD8-positive T-cell infiltrates were associated with PFS in ovarian carcinoma patients.

CONCLUSIONS

Combining trabectedin and durvalumab is manageable. Promising activity is observed in platinum-refractory ovarian carcinoma patients.

CD95/Fas protects triple negative breast cancer from anti-tumor activity of NK cells

The apoptosis inducing receptor CD95/Fas has multiple tumorigenic activities. In different genetically engineered mouse models tumor-expressed CD95 was shown to be critical for cell growth. Using a combination of immune-deficient and immune-competent mouse models, we now establish that loss of CD95 in metastatic triple negative breast cancer (TNBC) cells prevents tumor growth by modulating the immune landscape. CD95-deficient, but not wild-type, tumors barely grow in an immune-competent environment and show an increase in immune infiltrates into the tumor. This growth reduction is caused by infiltrating NK cells and does not involve T cells or macrophages. In contrast, in immune compromised mice CD95 k.o. cells are not growth inhibited, but they fail to form metastases. In summary, we demonstrate that in addition to its tumor and metastasis promoting activities, CD95 expression by tumor cells can exert immune suppressive activities on NK cells, providing a new target for immune therapy.

Plasma proteomics identifies leukemia inhibitory factor (LIF) as a novel predictive biomarker of immune-checkpoint blockade resistance

BACKGROUND

Immune checkpoint blockers (ICBs) are now widely used in oncology. Most patients, however, do not derive benefit from these agents. Therefore, there is a crucial need to identify novel and reliable biomarkers of resistance to such treatments in order to prescribe potentially toxic and costly treatments only to patients with expected therapeutic benefits. In the wake of genomics, the study of proteins is now emerging as the new frontier for understanding real-time human biology.

PATIENTS AND METHODS

We analyzed the proteome of plasma samples, collected before treatment onset, from two independent prospective cohorts of cancer patients treated with ICB (discovery cohort n = 95, validation cohort n = 292). We then investigated the correlation between protein plasma levels, clinical benefit rate, progression-free survival and overall survival by Cox proportional hazards models.

RESULTS

By using an unbiased proteomics approach, we show that, in both discovery and validation cohorts, elevated baseline serum level of leukemia inhibitory factor (LIF) is associated with a poor clinical outcome in cancer patients treated with ICB, independently of other prognostic factors. We also demonstrated that the circulating level of LIF is inversely correlated with the presence of tertiary lymphoid structures in the tumor microenvironment.

CONCLUSION

This novel clinical dataset brings strong evidence for the role of LIF as a potential suppressor of antitumor immunity and suggests that targeting LIF or its pathway may represent a promising approach to improve efficacy of cancer immunotherapy in combination with ICB.

Mature tertiary lymphoid structures predict immune checkpoint inhibitor efficacy in solid tumors independently of PD-L1 expression

Only a minority of patients derive long-term clinical benefit from anti-PD1/PD-L1 monoclonal antibodies. The presence of tertiary lymphoid structures (TLS) has been associated with improved survival in several tumor types. Here, using a large-scale retrospective analysis of three independent cohorts of cancer patients treated with anti-PD1/PD-L1 antibodies, we showed that the presence of mature TLS was associated with improved objective response rate, progression-free survival, and overall survival independently of PD-L1 expression status and CD8+ T-cell density. These results pave the way for using TLS detection to select patients who are more likely to benefit from immune checkpoint blockade.

PD1 inhibition in soft-tissue sarcomas with tertiary lymphoid structures: A multicenter phase II trial

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Background: PD1 inhibition has shown limited activity in all comers clinical trials including patients with advanced soft-tissue sarcomas (STS). In the PEMBROSARC study, objective response rate, progression-free (PFS) and overall survival (OS) were respectively 2.1%, 1.4 and 7.1 months respectively (Toulmonde et al. Jama Oncol 2017). We have recently shown that the presence of tertiary lymphoid structures (TLS) may represent a biomarker to select patients who are more likely to benefit from immunotherapy (PetitPrez et al., Nature 2020). We report here the first clinical trial investigating the efficacy of PD1 inhibition in TLS-positive STS. Methods: PEMBROSARC is an open-label multicenter phase II study of pembrolizumab in combination with low-dose cyclophosphamide in pts with STS selected based on the presence of TLS. TLS status has been assessed centrally has previously described (PetitPrez et al., Nature 2020). Eligible patients received pembrolizumab 200mg IV q21 days and cyclophosphamide 50 mg BID 1week on, 1 week off. All patients had confirmed progressive disease at inclusion based on central review of two imaging performed at less than 6 months interval. The primary efficacy endpoint was 6-month non-progression (as per RECIST evaluation criteria v1.1). Based on the following hypotheses: 15% 6-month non-progression rate (H0), 40% acceptable 6-month non-progression rate (H1), 5% type I error rate, 90% power, a total of 29 assessable patients were necessary and 8 patients or more had to be progression-free at 6 months to reach the first endpoint. Results: 240 patients were screened for TLS status between September 2018 and January 2020 in 7 centers of the French Sarcoma Group. Among them, 48 were found to be TLS+ as per central review and 35 were included in the study. The three most frequent histological subtypes were: well-differentiated/dedifferentiated liposarcoma (n = 13); UPS (n = 6), and leiomyosarcoma (n = 4). 30 patients were eligible for efficacy. Of those, as per central imaging review, 13 patients (43.3%) had tumor shrinkage resulting in partial response in 8 patients (26.7%) and stable disease in 5 cases (16.7%). 10 patients had progressive disease. Twelve patients were progression-free at 6 months (40.0% 95%CI = [22.7 – 59.4]).Median PFS and OS were 4.1 months (95%CI, 1.4-9.6) and 14.5 months (95%CI, 8.5- 18.3 months), respectively. Conclusions: With an objective response and a 6-month non-progression rates of 26.7% and 40% respectively versus 2.1% and 4.2% in all comers, the PEMBROSARC study confirms that selection based on TLS status is an efficient approach to tailor immunotherapy in STS patients. Clinical trial information: NCT02406781.

Regomune: A phase II study of regorafenib + avelumab in solid tumors—Results of the biliary tract cancer (BTC) cohort

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Background: Regorafenib (R) has shown promising efficacy in patients (pts) with BTC refractory to standard chemotherapy. Anti-PD1/PD-L1 antibodies have only limited clinical activity. Synergy between R and anti–PD-1/PD-L1 antibodies has been shown in pre-clinical solid tumor models. Methods: This is a single-arm open-label multicentric phase II trial (Bayesian adaptive design) assessing the efficacy and safety of R (160 mg QD 3weeks/4) + avelumab (A) (10 mg/kg every 2 weeks) combination in BTC pts. The primary endpoint was the objective response rate under treatment, based on central review according to RECIST 1.1. Secondary endpoints included: 1-year progression free survival (PFS), 1-year overall survival (OS), and Safety using NCI-CTCAE v5.0. Correlative studies were planned from pts tumor samples obtained at baseline. Results: Between Nov. 2018 and Nov. 2019, 34 BTC pts were enrolled in 4 centers. Median age was 63 (range 36 – 80). Median follow-up was 9.8 months. Median number of previous treatment lines for metastatic or locally advanced disease was: 2 (range 1 – 4). Twenty-nine (85.3%) pts experienced at least 1 dose modification or treatment interruption of R or A due to an adverse event (AE) related to the treatment. The most common grade 3/4 AEs were : Hypertension (17.6%), Fatigue (14.7%), and maculo-papular rash (11.8%). No death was related to the treatment. Among the 29 pts with at least one imaging tumor assessment, 4 (13.8%) achieved a partial response, and 11 (37.9%) demonstrated stable disease including 10 (34.5%) pts with tumor shrinkage. Fourteen pts (48.3%) had progressive disease. The median PFS and OS were 2.5 months (95%CI 1.9 – 5.5) and 11.9 months (95%CI 6.2 – NA) respectively. Baseline tumor samples were available for 27 pts. High IDO and PD-L1 expression at baseline was associated with better outcome. Conclusions: The R+A combination is associated with significant anti-tumor activity with promising survival rates in this heavily pre-treated population. Full Biomarkers analyses will be presented at the meeting. Clinical trial information: NCT03475953.

Regorafenib-Avelumab Combination in Patients with Microsatellite Stable Colorectal Cancer (REGOMUNE): A Single-arm, Open-label, Phase II Trial

PURPOSE

Regorafenib is synergistic with immune checkpoint inhibition in colorectal cancer preclinical models.

PATIENTS AND METHODS

This was a single-arm, multicentric phase II trial. Regorafenib was given 3 weeks on/1 week off, 160 mg every day; avelumab 10 mg/kg i.v. was given every 2 weeks, beginning at cycle 1, day 15 until progression or unacceptable toxicity. The primary endpoint was the confirmed objective response rate under treatment, as per RECIST 1.1. The secondary endpoints included a 1-year nonprogression rate, progression-free survival (PFS), and overall survival (OS), safety and biomarkers studies performed on sequential tumor samples obtained at baseline and at cycle 2 day 1.

RESULTS

Forty-eight patients were enrolled in four centers. Forty-three were assessable for efficacy after central radiological review. Best response was stable disease for 23 patients (53.5%) and progressive disease for 17 patients (39.5%). The median PFS and OS were 3.6 months [95% confidence interval (CI), 1.8-5.4] and 10.8 months (95% CI, 5.9-NA), respectively. The most common grade 3 or 4 adverse events were palmar-plantar erythrodysesthesia syndrome (n = 14, 30%), hypertension (n = 11, 23%), and diarrhea (n = 6, 13%). High baseline infiltration by tumor-associated macrophages was significantly associated with adverse PFS (1.8 vs. 3.7 months; P = 0.002) and OS (3.7 months vs. not reached; P = 0.002). Increased tumor infiltration by CD8⁺ T cells at cycle 2, day 1 as compared with baseline was significantly associated with better outcome.

CONCLUSIONS

The combination of regorafenib + avelumab mobilizes antitumor immunity in a subset of patients with microsatellite stable colorectal cancer. Computational pathology through quantification of immune cell infiltration may improve patient selection for further studies investigating this approach.

Abstract 6697: DT095895, a selective EP4 receptor antagonist with monotherapy efficacy in syngeneic mouse model(s) and best-in-class properties

Elevated levels of Prostaglandin E2 (PGE2), an eicosanoid notably synthesized by the cyclooxygenase-2 (COX-2), exert strong immunosuppressive effects in the tumor microenvironment. COX-2-positive solid tumors have the ability to use this pathway as a resistance mechanism, especially to escape from the host immune system, thus limiting the anti-tumor effects of immune checkpoint inhibitors (ICI). These immunosuppressive effects are largely mediated by the EP4 receptor, expressed on multiple immune cells. A novel series of EP4 receptor antagonists has been developed, with improved pharmacokinetic properties when compared to the EP4 receptor antagonists currently being evaluated in clinical trials. An intensive lead optimization program led to the identification of DT095895, a small molecule development candidate with a “best-in class” potential. Its preclinical package will be presented in the poster. DT095895 was assessed in multiple syngeneic mouse tumor models selected for their COX-2 expression profile. Efficacy was seen both in a monotherapy setting, as well as in combination with ICI. Additionally, a specific biomarker program was implemented and validated in order to show target engagement. A phospho-flow murine whole blood assay was set up to assess the ability of DT095895 to inhibit CREB phosphorylation induced by a selective EP4 receptor agonist in CD3+ cells. This biomarker was further developed for human whole blood to support Phase 1 and clinical trials studies. In conclusion, DT095895 is a selective EP4 receptor antagonist and demonstrates strong anti-tumor effects in multiple syngeneic mouse tumor models, both as a monotherapy and in combination with ICI, through the inhibition of the PGE2-induced immunosuppression. DT095895 progresses in regulatory development.

Citation Format: Anne-Laure Blayo, Laurène Deshons, Alexia Dumont, Christel Franchet, Célia Halter, Ludovic Herbin, Gaël Hommet, Stanislas Mayer, Alban Bessede, Imane Nafia, Marjorie Sidhoum, Xavier Leroy, Stephan Schann. DT095895, a selective EP4 receptor antagonist with monotherapy efficacy in syngeneic mouse model(s) and best-in-class properties [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6697.

Abstract 3938: Anti-angiogenic therapy combination with hypoxia-regulating agent leads to improved tumor regression in a murine model or renal carcinoma

Background: While antiangiogenic therapies have been shown effective in preclinical and clinical trials, tumors can acquire resistance conferring them the ability to survive and grow under hypoxic conditions, even, induced by antiangiogenic drugs themselves.

Methods: This study investigated the effects of an antiangiogenic strategy and hypoxia-regulating agent, each alone and in combination. Here, we have tested the synergistic activity of the anti-angiogenic agent Sunitinib and the mTOR inhibitor Everolimus in murine syngeneic renal cancer model - renal carcinoma being known as angiogenesis-dependent and hypoxia-driven malignancy. Anti-tumor effects were investigated on tumor growth and survival. Flow cytometry-based immunoprofiling was performed at the peripheral level - blood and spleen - while immunohistofluorescence and quantitative image analysis served to characterize and evaluate tumor immune cell infiltrate, tumor hypoxia, and tumor vascular density/features.

Results: While Sunitinib and more importantly Everolimus led to a significant tumor growth inhibition as single agents, their combination was more effective on tumor regression. At the peripheral level, Sunitinib, but also Everolimus, led each to declines in circulating and splenic myeloid-derived suppressor cells (MDSCs) - depicted as CD11b+/Gr1+, an event that was further optimized upon combination of both agents. In addition, tumor sections analyses showed decreased microvessel density under Sunitinib and combination treatment. Differential modulations of correlative endothelium/pericytes staining and hypoxia degree were also observed upon the different treatments. This study confirms the preclinical efficacy of Sunitinib and a hypoxia regulator in renal tumor model and suggests that limitation of Sunitinib-induced hypoxia through mTOR targeting or with hypoxia regulators represents a suitable strategy to enhance effect of anti-angiogenic agent thereby limiting tumor growth.

Citation Format: Imane Nafia, Assia Chaibi, Doriane Bortolotto, Christophe Rey, Alban Bessede. Anti-angiogenic therapy combination with hypoxia-regulating agent leads to improved tumor regression in a murine model or renal carcinoma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3938.

Abstract 934: “GPCR-ome” modulation upon PD1 / PDL1 axis blockade

Background: Immunotherapy represents a novel weapon within the cancer armamentarium with unprecedented response observed in several indications including among others metastatic melanoma and Lung cancer. However, the limited rate of response accounting for app. 30% requires further optimization and thus calls the interest in elucidating mechanisms underlying sensitivity to immune checkpoint inhibitors. G Protein-Coupled Receptors (GPCRs) are the largest gene family of cell membrane-associated molecules mediating signal transmission, involved in several physiological functions including the shaping of the immune response but their role in tumor biology and particularly in immune evasion and resistance to immunotherapy remains to be elucidated

Methods: Using a preclinical syngeneic mouse model of sarcoma based on the inoculation of murine sarcoma MCA205 cell line, we investigated - besides the evaluation of tumor growth and survival - a large set of GPCRs upon PDL1 or PD1 blockade. Gene expression analysis was performed on tumor samples by mean of RNA sequencing. Data were analyzed using computational methodology including CIBERSORT and GSEA algorithms to evaluate immune cell subset within the tumor and specific gene datasets enrichment respectively. A large set of GPCRs (1412 in total) was then investigated through conventional Differential Gene Expression (DGE) analysis.

Results: PDL1/PD1 axis blockade, using specific antibodies, exhibited a strong anti-tumor effect. As highlighted by CIBERSORT analysis, anti-PD1/PDL1 antibodies triggered a CD8 and activated NK cells infiltration within the tumor. The recruitment of such effectory populations was associated with enrichment in genes from different hallmarks datasets including allograft rejection and interferon signaling thus confirming the induction of an efficient anti-tumor immune response. Concomitantly, this study revealed a significant up-regulation of several GPCRs already known to be involved in immune evasion - including Adenosine, Prostaglandins and chemokines receptors - but also highlighted the modulation of unexpected orphan or peptidic receptors. Altogether, this novel dataset confirms the induction of an effective anti-tumor immune response upon PD1 / PDL1 blockade and highlights the modulation of GPCRs that warrants further investigation to delineate their exact participation in sensitivity to immunotherapy.

Citation Format: Imane Nafia, Xavier Leroy, Loic Cerf, Jean-Philippe Guegan, Anne-Laure Blayo, Antoine Italiano, Stephan Schann, Alban Bessede. “GPCR-ome” modulation upon PD1 / PDL1 axis blockade [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 934.

Inactivating mutations in genes encoding for components of the BAF/PBAF complex and immune-checkpoint inhibitor outcome

Alterations of genes encoding subunits of the BAF/PBAF complexes are among the most frequent gene aberrations in human cancer. Such alterations have been shown to have an impact on tumor microenvironnement and on the capacity of tumors to respond to immune-checkpoint inhibitors (ICI). We analysed the clinical and genetic data from 43,728 patients accessed through cBioportal. The mutational frequencies of ARID1A, ARID1B, ARID2, PBRM1, SMARCA4, and SMARCB1 were 6.6%, 3,4, 3.4, 3.2, 4.1, and 1.2%, respectively. We then investigated the association between the presence of least one nonsynonymous somatic mutation of ARID1A, ARID1B, ARID2, PBRM1, SMARCA4, or SMARCB1 and overall survival of 1661 patients treated with an ICI. Across the entire cohort, patients with BAF/PBAF mutated tumors have a statistically significant improvement in overall survival (median overall survival: 28 months [95% CI 21.6-34.3] versus 15 months [95% CI 12.9-17.0], p < 0.0001). When tumor mutational burden was adjusted for a multivariable Cox regression analysis, BAF/PBAF gene mutations remained an independent prognostic factor for overall survival in patients treated ICI. Our results establish a relationship between mutations in key genes encoding for components of the BAF/PBAF complex and outcome of patients treated with ICI. Further studies are needed to elucidate the underlying mechanisms of this interaction.

REGOMUNE: A phase II study of regorafenib plus avelumab in solid tumors—Results of the non-MSI-H metastatic colorectal cancer (mCRC) cohort

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Background: Regorafenib (R) has been shown to modulate anti-tumor immunity by different mechanisms including reduction of tumor-associated macrophages (TAMs). Synergy between R and anti–PD-1/PD-L1 antibodies has been shown in pre-clinical models. Methods: This is a single-arm open-label multicentric phase II trial assessing the efficacy and safety of R (160 mg QD 3weeks/4) + Avelumab (A) (10 mg/kg every 2 weeks) combination in non MSI-H mCRC patients (pts). The primary endpoint was the confirmed objective response rate, based on central review according to RECIST 1.1. Secondary endpoints included: 1-year progression free survival (PFS), 1-year overall survival (OS), and Safety using NCI-CTCAE v5.0. Correlative studies were planned from pts tumor samples obtained at baseline and C2D1. Results: Between Nov. 2018 and Oct. 2019, 48 pts were enrolled in 4 centers. Median age was 61.8 (range: 26.3-78.7). Median follow-up was: 7.2 months. Median number of previous treatment lines was: 3 (range: 1-7). 41 (87.2%) pts experienced at least 1 dose modification or treatment interruption. The most common grade 3/4 adverse events were palmar-plantar erythro-dysesthesia syndrome (29.8%), hypertension (23.4%) and diarrhea (12.8%). No death was related to the treatment. Among 40 pts who had at least one imaging tumor assessment, 12 (30%) had reduction in tumor burden. Best response was stable disease for 23 pts (57.5%) and progressive disease for 17 pts (42.5%). The median PFS and OS were 3.6 months (CI95%: [1.8 – 5.4]) and 10.8 months (CI95%: [5.9 – NA]) respectively. Baseline tumor samples and paired biopsies were available for 24 and 15 pts respectively. High infiltration by TAMs at baseline was significantly associated with adverse outcome (PFS: 1.9 vs 3.7 months, p=0.045; OS: 4.8 months vs NR, p=0.027). Increased tumor infiltration by CD8+ at C2D1 compared to baseline was significantly associated with better PFS (p=0.011). Combining low TAMs infiltration and low tumor cells to CD8+ T cells distance enabled the identification of a subgroup of pts (n= 6/24, 25%) more likely to benefit from R+A combination: median PFS: 5.3 vs 1.9 months (p=0.037); median OS: NR vs 5.3 months (p=0.02). Conclusions: The R+A combination achieved PFS and OS that compared favourably with historical data of R alone in this clinical setting. High-resolution analysis of tumor samples identified a composite score based on TAMs infiltration and tumor cell to CD8+ T cells distance which could be used as a biomarker in further studies investigating this approach in mCRC pts. Clinical trial information: NCT03475953 .

IDO Targeting in Sarcoma: Biological and Clinical Implications

Sarcomas are heterogeneous malignant mesenchymal neoplasms with limited sensitivity to immunotherapy. We recently demonstrated an increase in Kynurenine Pathway (KP) activity in the plasma of sarcoma patients treated with pembrolizumab. While the KP has already been described to favor immune escape through the degradation of L-Tryptophan and production of metabolites including L-Kynurenine, Indoleamine 2,3 dioxygenase (IDO1), a first rate-limiting enzyme of the KP, still represents an attractive therapeutic target, and its blockade had not yet been investigated in sarcomas. Using immunohistochemistry, IDO1 and CD8, expression profiles were addressed within 203 cases of human sarcomas. At a preclinical level, we investigated the modulation of the KP upon PDL1 blockade in a syngeneic model of sarcoma through mRNA quantification of key KP enzymes within the tumor. Furthermore, in order to evaluate the possible anti-tumor effect of IDO blockade in combination with PDL1 blockade, an innovative IDO inhibitor (GDC-0919) was used. Its effect was first assessed on Kynurenine to Tryptophan ratio at plasmatic level and also within the tumor. Following GDC-0919 treatment, alone or in combination with anti-PDL1 antibody, tumor growth, immune cell infiltration, and gene expression profiling were measured. IDO1 expression was observed in 39.1% of human sarcoma cases and was significantly higher in tumors with high CD8 infiltration. In the pre-clinical setting, blockade of PDL1 led to a strong anti-tumor effect and was associated with an intratumoral inflammatory cytokines signature driven by Ifng but also with a modulation of the KP enzymes including Ido1 and Ido2. IDO1 inhibition using GDC-0919 resulted in (i) a significant decrease of plasmatic Kynurenine to Tryptophan ratio and in (ii) a decrease of tumoral Kynurenine. However, GDC-0919 used alone or combined with anti-PDL1, did not show anti-tumoral activity and did not affect the tumor immune cell infiltrate. In order to elucidate the mechanism(s) underlying the lack of effect of GDC-0919, we analyzed the gene expression profile of intratumoral biopsies. Interestingly, we have found that GDC-0919 induced a downregulation of the expression of pvr and granzymes, and an upregulation of inhba and Dtx4 suggesting a potential role of the IDO pathway in the control of NK function.

Cabozantinib in patients with advanced Ewing sarcoma or osteosarcoma (CABONE): a multicentre, single-arm, phase 2 trial

BACKGROUND

Patients with Ewing sarcoma or osteosarcoma have a median overall survival of less than 12 months after diagnosis, and a standard treatment strategy has not yet been established. Pharmacological inhibition of MET signalling and aberrant angiogenesis has shown promising results in several preclinical models of Ewing sarcoma and osteosarcoma. We aimed to investigate the activity of cabozantinib, an inhibitor of MET and VEGFR2, in patients with advanced Ewing sarcoma and osteosarcoma.

METHODS

We did a multicentre, single-arm, two-stage, phase 2 trial in patients with advanced Ewing sarcoma or osteosarcoma recruited from ten centres in the French Sarcoma Group. Key eligibility criteria were aged 12 years or older, Eastern Cooperative Oncology Group performance status of 0-1, and documented disease progression (according to Response Evaluation Criteria in Solid Tumors version 1.1) before study entry. The number of previous lines of treatment was not limited. Patients received cabozantinib (adults 60 mg, children [<16 years] 40 mg/m²) orally once daily in 28-day cycles until disease progression, unacceptable toxicity, the investigator's decision to discontinue, or participant withdrawal. The primary endpoint for Ewing sarcoma was best objective response within 6 months of treatment onset; for osteosarcoma, a dual primary endpoint of 6-month objective response and 6-month non-progression was assessed. All enrolled patients who received at least one dose of cabozantinib were included in the safety analysis, and all participants who received at least one complete or two incomplete treatment cycles were included in the efficacy population. This study was registered with ClinicalTrials.gov, number NCT02243605.

FINDINGS

Between April 16, 2015, and July 12, 2018, 90 patients (45 with Ewing sarcoma 45 with osteosarcoma) were recruited to the study. Median follow-up was 31·3 months (95% CI 12·4-35·4) for patients with Ewing sarcoma and 31·1 months (24·4-31·7) for patients with osteosarcoma. 39 (87%) patients with Ewing sarcoma and 42 (93%) patients with osteosarcoma were assessable for efficacy after histological and radiological review. In patients with Ewing sarcoma, ten (26%; 95% CI 13-42) of 39 patients had an objective response (all partial responses) by 6 months; in patients with osteosarcoma, five (12%; 4-26) of 42 patients had an objective response (all partial responses) and 14 (33%; 20-50) had 6-month non-progression. The most common grade 3 or 4 adverse events were hypophosphataemia (five [11%] for Ewing sarcoma, three [7%] for osteosarcoma), aspartate aminotransferase increase (two [4%] for Ewing sarcoma, three [7%] for osteosarcoma), palmar-plantar syndrome (three [7%] for Ewing sarcoma, two [4%] for osteosarcoma), pneumothorax (one [2%] for Ewing sarcoma, four [9%] for osteosarcoma), and neutropenia (two [4%] for Ewing sarcoma, four [9%] for osteosarcoma). At least one serious adverse event was reported in 61 (68%) of 90 patients. No patients died from drug-related toxic effects.

INTERPRETATION

Cabozantinib has antitumor activity in patients with advanced Ewing sarcoma and osteosarcoma and was generally well tolerated. Cabozantinib could represent a new therapeutic option in this setting, and deserves further investigation.

FUNDING

Institut Bergonié; French National Cancer Institute; Association pour la Recherche contre le Cancer.

Sustained activation of the Aryl hydrocarbon Receptor transcription factor promotes resistance to BRAF-inhibitors in melanoma

BRAF inhibitors target the BRAF-V600E/K mutated kinase, the driver mutation found in 50% of cutaneous melanoma. They give unprecedented anti-tumor responses but acquisition of resistance ultimately limits their clinical benefit. The master regulators driving the expression of resistance-genes remain poorly understood. Here, we demonstrate that the Aryl hydrocarbon Receptor (AhR) transcription factor is constitutively activated in a subset of melanoma cells, promoting the dedifferentiation of melanoma cells and the expression of BRAFi-resistance genes. Typically, under BRAFi pressure, death of BRAFi-sensitive cells leads to an enrichment of a small subpopulation of AhR-activated and BRAFi-persister cells, responsible for relapse. Also, differentiated and BRAFi-sensitive cells can be redirected towards an AhR-dependent resistant program using AhR agonists. We thus identify Resveratrol, a clinically compatible AhR-antagonist that abrogates deleterious AhR sustained-activation. Combined with BRAFi, Resveratrol reduces the number of BRAFi-resistant cells and delays tumor growth. We thus propose AhR-impairment as a strategy to overcome melanoma resistance.

Abstract 5716: Functional evidence for an immunosuppressive role of kynurenine in cancer patients

Background: While being neglected for decades, tumor immune escape is now considered as a new paradigm that promotes tumor growth and evasion. Besides the prototypical PD1 / PDL1 axis, several mechanisms has been identified as important actor in immune editing process. Indoleamine 2,3 dioxygenase (IDO1), a first rate-limiting enzyme of the Kynurenine pathway, has been described to favor tolerance and immune escape through the production of a series of metabolites including L-Kynurenine. However, functional evidences have not yet been clearly demonstrated.

Methods: We reconstituted in vitro a human immune - tumor cell synapse where ability of primary immune cells to promote tumor cell death has been kinetically followed through fluorescent-based live cell imaging in the presence and absence of L-Kynurenine. Two different donors as source of Peripheral Blood Mononuclear Cells (PBMCs) and three different tumor cell lines - namely IB115 and IB136 as sarcoma models & H1299 as reference lung adenocarcinoma model - have been used in this study. Finally, in order to determine cancer subtypes that might be highly exposed to Kynurenine pathway dysregulation and associated immune dysfunction, a comprehensive analysis of Kynurenine and Tryptophan levels was done in a series of 691 patients with advanced solid tumors

Results: L-Kynurenine demonstrated a clear propensity to limit the immune cell-mediated tumor apoptosis elicited by TCR ligation - an event that was consistent within the two different donors and the three different cell lines. Interestingly, this immune suppressive feature of L-Kynurenine was associated with a limited amount of gamma-Interferon (IFNγ) in the cell culture supernatant while no effect was observed on Tumor Necrosis Factor alpha (TNFα). It's worth to note that L-Kynurenine had no effect on tumor cells without immune cells thus suggesting that Kynurenine has direct action on immune cells through which it limits their anti-tumor function -The Kyn/Trp ratio in cancer patients was significantly higher than that reported in healthy subjects (median: 71.2, range: 5.8-2825.2). Median value was the highest in breast cancer (126) and the lowest in colorectal (54) and pancreatic cancer (51) patients. No correlation with IDO1 tumor expression neither with systemic markers of inflammation (C-reactive protein) was observed.

In conclusion, these results represent the first large description of the Kynurenine/Tryptophan ratio levels in cancer patients and the first functional evidence of a direct inhibition by Kynurenine of lymphocytes's effector functions.

Citation Format: Alban Bessede, Antoine Italiano, Assia Chaïbi, Christophe Rey, Imane Nafia, Sylvestre le Moulec, Sophie Cousin, Maud Toulmonde, Céline Auzanneau, Marina Pulido. Functional evidence for an immunosuppressive role of kynurenine in cancer patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5716.

Use of PD-1 Targeting, Macrophage Infiltration, and IDO Pathway Activation in Sarcomas: A Phase 2 Clinical Trial

IMPORTANCE

There is a strong rationale for treating sarcomas with immunotherapy.

OBJECTIVE

To assess the efficacy and safety of programmed cell death protein 1 (PD-1) targeting in combination with metronomic chemotherapy in sarcomas.

DESIGN, SETTING, AND PARTICIPANTS

This was an open-label, multicenter, phase 2 study of 4 cohorts of patients with advanced soft-tissue sarcoma (STS), including leiomyosarcoma (LMS), undifferentiated pleomorphic sarcoma (UPS), other sarcomas (others), and gastrointestinal stromal tumor (GIST). All patients received 50 mg twice daily cyclophosphamide 1 week on and 1 week off and 200 mg of intravenous pembrolizumab every 3 weeks.

INTERVENTION OR EXPOSURE

Pembrolizumab in combination with metronomic cyclophosphamide.

MAIN OUTCOMES AND MEASURES

There was a dual primary end point, encompassing both the nonprogression and objective responses at 6 months per Response Evaluation Criteria in Solid Tumours (RECIST) v1.1 for LMS, UPS, and others and 6-month nonprogression for GIST. An objective response rate of 20% and/or a 6-month nonprogression rate of 60% were determined as reasonable objectives for treatment with meaningful effect. Correlative studies of immune biomarkers were planned from patient tumor and plasma samples.

RESULTS

Between June 2015 and July 2016, 57 patients were included (median [range] age, 59.5 [18.5-84.0] years; 24 women [42%]); 50 patients were assessable for the efficacy end point. Three patients experienced tumor shrinkage, resulting in a partial response in a single solitary fibrous tumor. The 6-month nonprogression rates were 0%, 0%, 14.3% (95% CI, 1.8%-42.8%) for LMS, UPS, and others, respectively, and 11.1% (95% CI, 2.8%-48.3%) for GIST. The most frequent adverse events were grade 1 or 2 fatigue, diarrhea, and anemia. The only patient who experienced partial response was the only one with strong programmed cell death 1 ligand 1-positive staining in immune cell. Strong infiltration by macrophage expressing the inhibitory enzyme indoleamine 2,3-dioxygenase 1 (IDO1) was observed in the majority of cases. Moreover, a significant increase in the kynurenine to tryptophan ratio was observed in patient plasma samples during the study treatment.

CONCLUSIONS AND RELEVANCE

We found that PD-1 inhibition has limited activity in selected STS and GIST. This may be explained by an immunosuppressive tumor microenvironment resulting from macrophage infiltration and IDO1 pathway activation.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT02406781.