Abstract 3283: GEN1046 (DuoBody®-PD-L1x4-1BB) in combination with PD-1 blockade potentiates anti-tumor immunity

GEN1046 (DuoBody®-PD-L1x4-1BB) is an investigational, potential first-in-class bispecific immunomodulatory antibody designed to elicit an anti-tumor immune response by simultaneous and complementary blockade of PD-L1 on tumor or immune cells and conditional 4-1BB stimulation on T cells and NK cells. Previously, we described encouraging preclinical and early clinical activity of GEN1046 (Muik, et al., 2022, Cancer Discovery). We hypothesized that combining GEN1046 with PD-1 blockade would further potentiate anti-tumor activity through distinct and complementary immune modulatory effects. Addition of an anti-PD-1 agent would free up PD-L1 for binding to GEN1046, thus promoting PD-L1-dependent 4-1BB conditional agonism, while maintaining complete blockade of the PD-1 pathway by inhibiting interactions with both PD-L1 and PD-L2. ​Here we provide preclinical evidence supportive of therapeutic synergy by the combination of GEN1046 and anti-PD-1 and describe the mechanisms of enhanced anti-tumor immunity elicited by the combination. In in vitro studies, combining GEN1046 with an anti-PD-1 agent potentiated cytokine release in mixed lymphocyte reaction assays (using either unstimulated T cells or T cells exhausted by repeated CD3/CD28 co-stimulation) and enhanced T-cell expansion and cytokine secretion in antigen-specific proliferation assays compared to each single agent. In in vivo studies in mice bearing syngeneic subcutaneous MC38 tumors, the combination of an anti-mouse PD-L1x4-1BB bispecific antibody with anti-mouse PD-1 potentiated anti-tumor activity with significant enhancement of survival (P≤0.001) and durable, complete tumor regressions (CR) in 7/10 mice compared to no CR observed with either single agent, suggesting therapeutic synergy with the combination. The combination treatment elicited long-lasting immune memory response, as animals with CR were protected from tumor outgrowth upon rechallenge with MC38 cells. Mechanistically, animals treated with the combination showed a trend for ≥1.5-fold increase in the average density of CD3+ and CD4+ tumor-infiltrating lymphocytes (TILs), as well as proliferating (Ki67+) and cytotoxic (GZMB+) CD8+ TILs relative to each single agent, consistent with an amplified anti-tumor immune response. Together, these preclinical results suggest that combining GEN1046-induced conditional 4-1BB stimulation with complete PD-1 blockade can improve the anti-tumor immune response via distinct and complementary immune modulatory effects. The combination of GEN1046 with pembrolizumab is currently being investigated in ongoing clinical studies in patients with advanced NSCLC, who are treatment-naïve (NCT03917381) or have progressed on prior CPI-containing therapy (NCT05117242).

Citation Format: Michela Capello, Angelica Sette, Theo Plantinga, Vanessa Spires, Kristina Nuermberger, Jordan Blum, Alexander Muik, Carol Costa Sa, Omar Jabado, Saskia Burm, Aras Toker, Sina Fellermeier-Kopf, Tahi Ahmadi, Brandon Higgs, Suzana Couto, Özlem Türeci, Mark Fereshteh, Ugur Sahin, Maria Jure-Kunkel, Nora Pencheva. GEN1046 (DuoBody®-PD-L1x4-1BB) in combination with PD-1 blockade potentiates anti-tumor immunity [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 3283.

Abstract 3248: Pharmacodynamic activity of epcoritamab (GEN3013; CD3xCD20) as monotherapy is maintained in combination with standard of care therapies in patients with diffuse large B-cell lymphoma

Introduction: B-cell lymphoma is a heterogeneous disease with an unmet medical need for efficacious, well tolerated, off-the-shelf therapies that can combine with standard of care (SOC) regimens. Epcoritamab is an IgG1 bispecific antibody that simultaneously binds to CD3 on T cells and CD20 on malignant B cells, inducing activation and cytotoxic activity of T cells and enabling killing of target lymphoma cells. Epcoritamab is well suited for combination therapy due to its distinct mechanism of action from that of many SOC regimens that may lead to improved clinical responses. Herein we evaluated the longitudinal pharmacodynamic (PD) effects of epcoritamab in clinical trial patients with diffuse large B-cell lymphoma (DLBCL) treated as monotherapy (EPCORE NHL-1: NCT03625037) and in combination with SOC therapies (EPCORE NHL-2: NCT04663347).

Methods: Patients with relapsed/refractory (R/R) DLBCL from EPCORE NHL-1 expansion phase received subcutaneous epcoritamab administered in 28-d cycles. Patients with newly diagnosed or R/R DLBCL from EPCORE NHL-2 received epcoritamab administered with a dosing schedule similar to that in EPCORE NHL-1, in combination with SOC therapies: R-CHOP, R-DHAX/C and GemOx. Biomarkers in fresh whole blood were assessed using validated flow cytometry assays. Cytokine levels in plasma were tested using a validated multiplex immunoassay.

Results: Epcoritamab monotherapy induced rapid (within the first cycle), sustained depletion of circulating peripheral B cells (CD19+) in patients with detectable peripheral B cells at baseline. A similar pattern of peripheral B-cell depletion was observed for epcoritamab in combination with SOC. Approximately 24 h following the first full dose, epcoritamab monotherapy induced a moderate but transient elevation of circulating cytokines IFNγ, IL-6 and IL-10. These cytokine patterns were similar for epcoritamab in combination with SOC. Within the first 8 wk of dosing, both epcoritamab monotherapy and in combination with SOC induced a transient elevation of percentages of peripheral CD8+ T cells expressing proliferation (Ki67) and activation (HLA-DR) markers. Expansion of peripheral CD8+ T cells and their effector memory subsets was observed with epcoritamab monotherapy, as well as in combination with SOC in later cycles. Peripheral CD4+ T cells demonstrated patterns similar to most of the biomarker observations in CD8+ T cells with epcoritamab as monotherapy and in combination.

Conclusion: These biomarker analyses show that the PD characteristics of epcoritamab monotherapy are maintained overall in combination with SOC therapies containing chemotherapeutic agents with or without rituximab and support the ongoing clinical studies investigating the combination of epcoritamab with SOC therapies in patients with DLBCL.

Citation Format: Jimin Zhang, Han Si, Monica Wielgos-Bonvallet, David Soong, Edith Szafer-Glusman, Herve Ghesquieres, Chan Y. Cheah, Lorenzo Falchi, Joshua Brody, Mariana Sacchi, Ali Rana, Brandon Higgs, Brian Elliot, Maria Jure-Kunkel, Christopher W. Chiu. Pharmacodynamic activity of epcoritamab (GEN3013; CD3xCD20) as monotherapy is maintained in combination with standard of care therapies in patients with diffuse large B-cell lymphoma [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 3248.

Abstract 2034: Spatial transcriptomics identifies unique pharmacodynamic effects of checkpoint inhibitor treatment on the tumor microenvironment in NSCLC

Background: Immune checkpoint inhibitor (ICI) therapy has improved outcomes in non-small cell lung cancer (NSCLC), particularly in patients with high tumor infiltrating lymphocytes (TILs). Identifying the pharmacodynamic (PD) impact of ICI on immune cells in the tumor microenvironment (TME) can inform therapeutic development for patients with progressive disease. We sought to identify PD changes in the TME from patients before and after ICI therapy using a spatial transcriptomics platform that allows highly multiplexed profiling of 1,800 genes (Nanostring Digital Spatial Profiler [DSP]).

Methods: Formalin fixed, paraffin embedded (FFPE) tumor tissue from 22 patients was sourced commercially. Patients were treated with neoadjuvant chemotherapy, then underwent a surgical tumor resection. After surgery an adjuvant chemotherapy was administered until progression; patients then received monotherapy ICI (nivolumab or pembrolizumab). Once progressed on ICI, another resection was performed. Patients were then treated with chemotherapy and followed until progression and/or death. The DSP technology was used to independently profile RNA from PanCK+ (tumor) and PanCK- (stroma) regions in the tissue based on fluorescence staining. Six circular regions of 600μm in diameter were selected for analysis using the GeoMx instrument; each area contained CD3+ cells. Additionally, immunohistochemistry for PDL1 and CD3 was performed, images were scored by a pathologist and analyzed with digital pathology algorithms.

Results: Spatial transcriptomic analysis of pre- vs post-ICI treatment in stroma revealed significant increases in T cell genes (CD3E, TCRB, NKG7), T-cell activation markers (CD69, IFNG, OX40, GZMB, ICOS), costimulatory signaling (CD28, CD80, CD86), and immune checkpoints (CTLA4, TIGIT). Ayers et al., JCI 2017 identified 28 genes predictive of ICI response, 12 were significantly upregulated in the stroma post-ICI (26 were present in the DSP panel). We identified genes in the pre-ICI stromal microenvironment that were highly expressed in patients with partial response to ICI, the most significant genes were involved in immune regulation (IFIT1) and extracellular matrix remodeling (MMP3). In contrast, stromal genes highly expressed in patients with progressive disease were associated with T-cell maintenance (ETS1, IL7R, CCL19).

Conclusions: In this study we used spatial transcriptomics to profile tissue regions where T-cells were in close proximity to tumor cells (microns). This focused, local PD analysis confirmed activated T-cells are present post-ICI. Ongoing studies in a larger cohort will be used to identify tumoral mechanisms of resistance and immune dysfunction to inform future therapeutics and combinations.

Citation Format: Li Fan, Omar Jabado, Nora Pencheva, Patricia Coutinho de Souza, Brandon Higgs, Angelo Harris, Patrick Franken, Anantharaman Muthuswamy, Maria Jure-Kunkel, Suzana Couto, Kate Sasser, Mark Fereshteh. Spatial transcriptomics identifies unique pharmacodynamic effects of checkpoint inhibitor treatment on the tumor microenvironment in NSCLC [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 2034.

DuoBody-CD40x4-1BB induces dendritic-cell maturation and enhances T-cell activation through conditional CD40 and 4-1BB agonist activity

Background

Despite the preclinical promise of CD40 and 4-1BB as immuno-oncology targets, clinical efforts evaluating CD40 and 4-1BB agonists as monotherapy have found limited success. DuoBody-CD40×4-1BB (GEN1042/BNT312) is a novel investigational Fc-inert bispecific antibody for dual targeting and conditional stimulation of CD40 and 4-1BB to enhance priming and reactivation of tumor-specific immunity in patients with cancer.

Methods

Characterization of DuoBody-CD40×4-1BB in vitro was performed in a broad range of functional immune cell assays, including cell-based reporter assays, T-cell proliferation assays, mixed-lymphocyte reactions and tumor-infiltrating lymphocyte assays, as well as live-cell imaging. The in vivo activity of DuoBody-CD40×4-1BB was assessed in blood samples from patients with advanced solid tumors that were treated with DuoBody-CD40×4-1BB in the dose-escalation phase of the first-in-human clinical trial (NCT04083599).

Results

DuoBody-CD40×4-1BB exhibited conditional CD40 and 4-1BB agonist activity that was strictly dependent on crosslinking of both targets. Thereby, DuoBody-CD40×4-1BB strengthened the dendritic cell (DC)/T-cell immunological synapse, induced DC maturation, enhanced T-cell proliferation and effector functions in vitro and enhanced expansion of patient-derived tumor-infiltrating lymphocytes ex vivo. The addition of PD-1 blocking antibodies resulted in potentiation of T-cell activation and effector functions in vitro compared with either monotherapy, providing combination rationale. Furthermore, in a first-in-human clinical trial, DuoBody-CD40×4-1BB mediated clear immune modulation of peripheral antigen presenting cells and T cells in patients with advanced solid tumors.

Conclusion

DuoBody-CD40×4-1BB is capable of enhancing antitumor immunity by modulating DC and T-cell functions and shows biological activity in patients with advanced solid tumors. These findings demonstrate that targeting of these two pathways with an Fc-inert bispecific antibody may be an efficacious approach to (re)activate tumor-specific immunity and support the clinical investigation of DuoBody-CD40×4-1BB for the treatment of cancer.

DLBCL cell of origin typing and whole transcriptome analysis using single slides with HTG EdgeSeq

7576

Background: Diffuse large B-cell Lymphoma (DLBCL) is a highly heterogenous disease. Gene microarrays were initially used to classify DLBCL into germinal center B-cell-like (GCB) or activated B-cell-like (ABC) Cell of Origin (COO) subtypes. ABC is associated with shorter overall survival. In newly diagnosed patients, COO classification by RNA profiling is a validated prognostic. A simpler immunohistochemical (IHC) staining of CD10, MUM1 and BCL6 is a proxy used in clinical practice in lieu of transcriptomics due to its expense, complexity and tissue requirements. Recent advances in the HTG EdgeSeq platform allow genome-scale profiling with minimal tissue. We successfully applied this novel technology to perform simultaneous COO classification, immune cell enrichment and tumor pathway analysis using a single FFPE slide. Methods: Accuracy of the HTG EdgeSeq panel (19,000 genes) was assessed in a head-to-head comparison with RNAseq using FFPE tumor samples (n = 8). DLBCL resections and core needle biopsies were commercially sourced and COO typed using Han’s algorithm into GCB or non-GCB (n = 65). Tumor locations included: lymphoid organs, gastrointestinal tract, testes, and the pleural cavity. EdgeSeq was performed on single slides with an average tissue area of 40mm2. Transcriptomic COO classification was performed using a linear combination of genes as described in Wright et al., PNAS 2003, substituting HTG platform-specific weights. Validated COO gene sets from literature and commercial diagnostic assays were tested. Immune cell gene signature enrichment analysis was performed using xCell (Aran et al., Genome Biol 2017); pathway analysis was performed with GSEA (Subramanian et al., PNAS 2005). Results: Gene expression levels estimated from whole transcriptome EdgeSeq on single slides were highly correlated to whole transcriptome RNAseq. Differential expression analysis of GCB vs non-GCB showed that key prognostic genes were detectable and enriched in the expected subtypes. Using these pre-established signatures, subtyping accuracy was ̃93% on the training set and 89% on the test set. Immune cell enrichment analysis identified class-switched memory B-cells as more prevalent in non-GCB subjects. This is consistent with emerging evidence that memory B-cells are the primary source of ABC DLBCL and not plasma cells (Venturutti & Melnick, Blood 2020). Pathway analysis identified genes regulated by the oncogene ic transcription factor MYC were enriched in non-GCB samples; MYC protein was found to be overexpressed in ABC in a large study (Hu et al., Blood 2013). Conclusions: Combined COO typing and whole transcriptome analysis from a single slide efficiently uses precious patient tissue. Longitudinal core needle sampling may yield insights into tumor evolution and therapeutic mechanisms of action across the DLBCL treatment landscape.

Preclinical Characterization and Phase I Trial Results of a Bispecific Antibody Targeting PD-L1 and 4-1BB (GEN1046) in Patients with Advanced Refractory Solid Tumors

Checkpoint inhibitors (CPI) have revolutionized the treatment paradigm for advanced solid tumors; however, there remains an opportunity to improve response rates and outcomes. In preclinical models, 4-1BB costimulation synergizes with CPIs targeting the programmed cell death protein 1 (PD-1)/programmed cell death ligand 1 (PD-L1) axis by activating cytotoxic T-cell-mediated antitumor immunity. DuoBody-PD-L1×4-1BB (GEN1046) is an investigational, first-in-class bispecific immunotherapy agent designed to act on both pathways by combining simultaneous and complementary PD-L1 blockade and conditional 4-1BB stimulation in one molecule. GEN1046 induced T-cell proliferation, cytokine production, and antigen-specific T-cell-mediated cytotoxicity superior to clinically approved PD-(L)1 antibodies in human T-cell cultures and exerted potent antitumor activity in transplantable mouse tumor models. In dose escalation of the ongoing first-in-human study in heavily pretreated patients with advanced refractory solid tumors (NCT03917381), GEN1046 demonstrated pharmacodynamic immune effects in peripheral blood consistent with its mechanism of action, manageable safety, and early clinical activity [disease control rate: 65.6% (40/61)], including patients resistant to prior PD-(L)1 immunotherapy.

SIGNIFICANCE

DuoBody-PD-L1×4-1BB (GEN1046) is a first-in-class bispecific immunotherapy with a manageable safety profile and encouraging preclinical and early clinical activity. With its ability to confer clinical benefit in tumors typically less sensitive to CPIs, GEN1046 may fill a clinical gap in CPI-relapsed or refractory disease or as a combination therapy with CPIs. See related commentary by Li et al., p. 1184. This article is highlighted in the In This Issue feature, p. 1171.

An Fc-inert PD-L1×4-1BB bispecific antibody mediates potent anti-tumor immunity in mice by combining checkpoint inhibition and conditional 4-1BB co-stimulation

Immune checkpoint inhibitors (ICI) targeting the PD-1/PD-L1 axis have changed the treatment paradigm for advanced solid tumors; however, many patients experience treatment resistance. In preclinical models 4-1BB co-stimulation synergizes with ICI by activating cytotoxic T- and NK-cell-mediated anti-tumor immunity. Here we characterize the mechanism of action of a mouse-reactive Fc-inert PD-L1×4-1BB bispecific antibody (mbsAb-PD-L1×4-1BB) and provide proof-of-concept for enhanced anti-tumor activity. In reporter assays mbsAb-PD-L1×4-1BB exhibited conditional 4-1BB agonist activity that was dependent on simultaneous binding to PD-L1. mbsAb-PD-L1×4-1BB further blocked the PD-L1/PD-1 interaction independently of 4-1BB binding. By combining both mechanisms, mbsAb-PD-L1×4-1BB strongly enhanced T-cell proliferation, cytokine production and antigen-specific cytotoxicity using primary mouse cells in vitro. Furthermore, mbsAb-PD-L1×4-1BB exhibited potent anti-tumor activity in the CT26 and MC38 models in vivo, leading to the rejection of CT26 tumors that were unresponsive to PD-L1 blockade alone. Anti-tumor activity was associated with increased tumor-specific CD8⁺ T cells and reduced regulatory T cells within the tumor microenvironment and tumor-draining lymph nodes. In immunocompetent tumor-free mice, mbsAb-PD-L1×4-1BB treatment neither induced T-cell infiltration into the liver nor elevated liver enzymes in the blood. Dual targeting of PD-L1 and 4-1BB with a bispecific antibody may therefore address key limitations of first generation 4-1BB-agonistic antibodies, and may provide a novel approach to improve PD-1/PD-L1 checkpoint blockade.

786 Dose selection for DuoBody®-PD-L1×4-1BB (GEN1046) using a semimechanistic pharmacokinetics/pharmacodynamics model that leverages preclinical and clinical data

Background

DuoBody-PD-L1×4-1BB (GEN1046) is a class-defining bispecific antibody, designed to elicit an anti-tumor immune response by simultaneous and complementary blockade of PD-L1 on tumor cells and conditional stimulation of 4-1BB on T-cells and NK cells. Optimizing target engagement for a bispecific antibody is challenging, as it involves binding with two targets, and predicting trimer levels in tumors based on affinity of individual arms and target expression. Here we describe a semimechanistic, physiologically based pharmacokinetic/pharmacodynamic (PK/PD) model that predicts a dosing regimen for DuoBody-PD-L1×4-1BB, which results in the formation of maximum levels of a therapeutically active 4-1BB-bispecific antibody-PD-L1 trimolecular complex (trimer), and optimal PD-L1 receptor occupancy (RO).

Methods

An integrated semimechanistic PK/PD model that describes the distribution of DuoBody-PD-L1×4-1BB into central and peripheral compartments and partitioning into tumor/lymph nodes was developed. The model used PK/PD data and physiological parameters from the literature for parameterizations of PD-L1 and 4-1BB expression levels and T-cell trafficking. The model incorporates dynamic binding of DuoBody-PD-L1×4-1BB to its targets to predict trimer formation and RO for PD-L1 in tumors. Model parameters were calibrated to match in vitro PD studies, such as analyses of T-cell proliferation and cytokine release, as well as clinical PK data. Sensitivity to model assumptions were assessed by varying PK/PD parameters, and assessing their impact on trimer formation and PD-L1 RO. The model was subsequently used to explore in vivo trimer levels and PD-L1 RO in tumors at various dosing regimens.

Results

The model was able to adequately describe the PK of DuoBody-PD-L1×4-1BB in the central compartment. Simulations showed a bell-shaped response for average trimer levels in tumors that peaked at 100 mg every 3 weeks (Q3W), with doses >100 mg resulting in reduced trimer formation. Average PD-L1 receptor occupancy at the 100 mg dose was predicted to be approximately 70% over 21 days and increased at higher doses. Based on these model predictions, and available safety, anti-tumor activity, and PD data from the ongoing GCT1046-01 trial (NCT03917381), 100 mg Q3W was chosen as the expansion dose for further evaluation in Part 2 of the study.

Conclusions

This semimechanistic PK/PD model provides a novel approach for dose selection of bispecific antibodies such as DuoBody-PD-L1×4-1BB, by using preclinical and clinical PK/PD data to predict formation of optimal trimer levels and PD-L1 receptor occupancy.

Acknowledgements

The authors thank Friederike Gieseke and Zuzana Jirakova at BioNTech SE; Kalyanasundaram Subramanian at Applied Biomath LLC for their valuable contributions.

Trial Registration

Written informed consent, in accordance with principles that originated in the Declaration of Helsinki 2013, current ICH guidelines including ICH-GCP E6(R2), applicable regulatory requirements, and sponsor policy, was provided by the patients.

833 A scalable deep learning framework for rapid automated annotation of histologic and morphologic features from large unlabeled pan-cancer H&E datasets

Background

Recent advances in machine learning and digital pathology have enabled a variety of applications including predicting tumor grade and genetic subtypes, quantifying the tumor microenvironment (TME), and identifying prognostic morphological features from H&E whole slide images (WSI). These supervised deep learning models require large quantities of images manually annotated with cellular- and tissue-level details by pathologists, which limits scale and generalizability across cancer types and imaging platforms. Here we propose a semi-supervised deep learning framework that automatically annotates biologically relevant image content from hundreds of solid tumor WSI with minimal pathologist intervention, thus improving quality and speed of analytical workflows aimed at deriving clinically relevant features.

Methods

The dataset consisted of >200 H&E images across >10 solid tumor types (e.g. breast, lung, colorectal, cervical, and urothelial cancers) from advanced disease patients. WSI were first partitioned into small tiles of 128μm for feature extraction using a 50-layer convolutional neural network pre-trained on the ImageNet database. Dimensionality reduction and unsupervised clustering were applied to the resultant embeddings and image clusters were identified with enriched histological and morphological characteristics. A random subset of representative tiles (<0.5% of whole slide tissue areas) from these distinct image clusters was manually reviewed by pathologists and assigned to eight histological and morphological categories: tumor, stroma/connective tissue, necrotic cells, lymphocytes, red blood cells, white blood cells, normal tissue and glass/background. This dataset allowed the development of a multi-label deep neural network to segment morphologically distinct regions and detect/quantify histopathological features in WSI.

Results

As representative image tiles within each image cluster were morphologically similar, expert pathologists were able to assign annotations to multiple images in parallel, effectively at 150 images/hour. Five-fold cross-validation showed average prediction accuracy of 0.93 [0.8–1.0] and area under the curve of 0.90 [0.8–1.0] over the eight image categories. As an extension of this classifier framework, all whole slide H&E images were segmented and composite lymphocyte, stromal, and necrotic content per patient tumor was derived and correlated with estimates by pathologists (p<0.05).

Conclusions

A novel and scalable deep learning framework for annotating and learning H&E features from a large unlabeled WSI dataset across tumor types was developed. This automated approach accurately identified distinct histomorphological features, with significantly reduced labeling time and effort required for pathologists. Further, this classifier framework was extended to annotate regions enriched in lymphocytes, stromal, and necrotic cells – important TME contexture with clinical relevance for patient prognosis and treatment decisions.

915 Molecular characterization of AXL in solid tumor malignancies using real-world data

Background

The receptor tyrosine kinase AXL is aberrantly expressed in many cancer types and associated with epithelial-to-mesenchymal transition (EMT), poor prognosis, and therapy resistance. To better understand the expression of this gene across specific disease subtypes, correlated pathways, and how certain therapies potentially modulate AXL expression, we investigated real-world clinical and molecular data across five solid tumor types before and after chemotherapy or immune checkpoint inhibitor (CPI) therapy.

Methods

Whole transcriptome and exome sequencing were derived from patient tumor specimens obtained either prior to treatment or following chemotherapy or CPI therapies. RNA reads were mapped using STAR and data was normalized using transcripts per million. DNA reads were mapped using Novoalign and variants were called using Freebayes and Pindel. Clinical data was curated from multiple sources, QC’d and deidentified according to standard protocols. Five diseases were included: non-small cell lung cancer (NSCLC, n=1181), ovarian cancer (OV, n=300), urothelial carcinoma (UC, n=140), pancreatic ductal adenocarcinoma (PDAC, n=942), and skin cutaneous melanoma (SKCM, n=157). PD-L1 positivity was defined as ≥1% tumor cells with PD-L1 immunohistochemical staining at any intensity.

Results

AXL mRNA levels were highest in PDAC followed by NSCLC, SKCM, UC and OV. Within OV, AXL expression levels were higher in tumors pre-treated with chemotherapy relative to untreated. For other tumor types, chemotherapy or CPI pre-treated tumors had AXL mRNA levels comparable to untreated tumors. Copy number amplifications of AXL were rare across all tumor types (<3%) and did not associate with mRNA expression. Distinct molecular subtypes in several cancers displayed relatively high AXL mRNA levels, including the mesenchymal subtype in OV and the stromal rich subtypes in PDAC. AXL levels also correlated with an EMT mRNA signature across all tumors (rho=0.67). Further, higher AXL expression was associated with PD-L1 positivity in NSCLC, UC and PDAC (p<0.01), but not OV where only a few tumors were PD-L1 positive.Oncogenic KRAS mutations were associated with higher AXL expression in NSCLC and PDAC (p<0.001) and lower AXL expression in OV (p=0.01). Loss of KDM6A, known to induce tumorigenesis in PDAC, was associated with higher AXL expression in PDAC (p<0.01). Loss-of-function mutations in ARID1A, previously implicated as CPI sensitizing, were associated with lower AXL mRNA levels in OV tumors (p<0.001).

Conclusions

Analyses of real-world mRNA datasets showed that AXL was upregulated in specific tumor and treatment settings as well as in patient populations with specific mutations and disease subtypes. Findings here should be validated with independent datasets.

516 Peripheral and tumoral immune activity in the expansion part of the first-in-human DuoBody®-PD-L1×4–1BB (GEN1046) trial

Background

DuoBody-PD-L1×4-1BB (GEN1046) is a class-defining, bispecific immunotherapy designed to induce an antitumor immune response by simultaneous and complementary PD-L1 blockade and conditional 4-1BB stimulation. Encouraging clinical activity and manageable safety were observed during dose escalation in the ongoing phase 1/2a trial in patients with advanced solid tumors (NCT03917381). We report exploratory pharmacodynamic analyses and potential biomarkers of response in an expansion cohort of patients with PD-(L)1–R/R NSCLC.

Methods

Patients with metastatic/unresectable NSCLC who had multiple lines of prior systemic therapy, including a checkpoint inhibitor, received flat-dose DuoBody-PD-L1×4-1BB (100 mg) intravenously every 3 weeks. Immunophenotyping of peripheral blood and measurements of soluble immune mediators were evaluated in serial blood samples in cycles 1–2. Tumor PD-L1 and 4-1BB expression and additional immune markers were evaluated by immunohistochemistry in core needle tumor biopsy specimens collected before treatment and at cycle 2.

Results

As of May 2021, 40 patients with PD-(L)1–R/R NSCLC were enrolled (median age, 63 years). Treatment with DuoBody-PD-L1×4-1BB elicited pharmacodynamic modulation of immune endpoints within the first 2 cycles. Induction of peripheral IFN-y, CXCL9/10, and expansion of peripheral CD8+ effector memory T cells and activated NK cells were observed starting at cycle 1 (>2-fold from baseline) and maintained or increased through cycle 2. Based on 9 paired tumor biopsy samples, increased PD-L1 and 4-1BB expression and cytotoxic CD8+/GZMB+ cell density were detected following treatment. In a subset of patients with clinical response (n=5 confirmed PRs), a trend of greater induction of IFN-y, CXCL9/10, and activated NK cells was observed vs nonresponders. Disease control rates were higher in patients who had progressed on prior anti–PD-1 therapy within 8 months (64% [16/25]) from the first dose of DuoBody-PD-L1×4-1BB. As expected, among patients with evaluable baseline tumors (n=26), most with any degree of tumor reduction (best change, <0%) harbored PD-L1+ tumors (≥1% tumor positive score; 7/10) and showed close spatial proximity between PD-L1+ and 4-1BB+ cells. Conversely, most patients without any degree of tumor reduction presented with PD-L1− tumors (12/16).

Conclusions

In patients with NSCLC who progressed on PD-(L)1 therapy, DuoBody-PD-L1×4-1BB elicited pharmacodynamic effects consistent with its proposed mechanism of action. Relationships between disease control and PD-L1 tumoral expression, as well as time from last prior anti–PD-1 therapy, were observed. These findings support that patient selection and/or anti–PD-1 combination therapy may lead to improved clinical efficacy. Further analyses are ongoing and updated results will be presented.

Acknowledgements

The authors thank Hrefna Kristin Johannsdottir, Lei Pang, and Kate Sasser at Genmab A/S and Friederike Gieseke at BioNTech SE for their valuable contributions. This trial was funded by Genmab A/S and BioNTech SE.

Trial Registration

NCT03917381

Ethics Approval

This trial is undertaken following full approval of the final protocol, amendments, informed consent form, applicable recruiting materials, and subject compensation programs by the Independent Ethics Committee/Institutional Review Board.

Consent

Written informed consent, in accordance with principles that originated in the Declaration of Helsinki 2013, current ICH guidelines including ICH-GCP E6(R2), applicable regulatory requirements, and sponsor policy, was provided by the patients.

Resistance to durvalumab and durvalumab plus tremelimumab is associated with functional STK11 mutations in non-small-cell lung cancer patients and is reversed by STAT3 knockdown

Mutations in the STK11 (LKB1) gene regulate resistance to PD-1/PD-L1 blockade. This study evaluated this association in patients with nonsquamous non-small-cell lung cancer enrolled in three Phase 1/2 trials. STK11 mutations were associated with resistance to the anti-PD-L1 antibody durvalumab (alone/with the anti-CTLA-4 antibody tremelimumab) independently of KRAS mutational status, highlighting STK11 as a potential driver of resistance to checkpoint blockade. Retrospective assessments of tumor tissue, whole blood and serum revealed a unique immune phenotype in patients with STK11 mutations, with increased expression of markers associated with neutrophils (i.e. CXCL2, IL6), Th17 contexture (i.e. IL17A) and immune checkpoints. Associated changes were observed in the periphery. Reduction of STAT3 in the tumor microenvironment using an antisense oligonucleotide reversed immunotherapy resistance in preclinical STK11 knockout models. These results suggest that STK11 mutations may hinder response to checkpoint blockade through mechanisms including suppressive myeloid cell biology, which could be reversed by STAT3-targeted therapy.

Abstract 1846: DuoBody-CD40×4-1BB (GEN1042) induces dendritic-cell maturation and enhances T-cell activation and effector functions in vitro by conditional CD40 and 4-1BB agonist activity

The clinical success of immune checkpoint inhibitor monoclonal antibodies (mAbs) has demonstrated potential for re-activation of anti-tumor immunity in cancer treatment. DuoBody®-CD40×4-1BB (GEN1042) is a first-in-class bispecific agonistic antibody that combines targeting of costimulatory molecules CD40 and 4-1BB, resulting in priming and (re-)activation of tumor-specific immunity. We previously showed that DuoBody-CD40×4-1BB induces CD40 and 4-1BB agonist activity that is conditional, i.e., dependent on crosslinking of CD40- and 4-1BB-expressing cells. Here we further elucidate the preclinical mechanism of action of DuoBody-CD40×4-1BB in a broad range of functional immune cell assays. Fixed cell microscopy and live cell imaging of the immune synapse was performed using co-cultures of activated T cells and monocyte-derived dendritic cells (DC). DuoBody-CD40×4-1BB co-localized with LFA-1 at the interface between DC and activated T cells. By binding to both targets, DuoBody-CD40×4-1BB enhanced DC/T cell interactions and increased the contact duration between these cells compared to the combination of monovalent CD40- and 4-1BB-specific antibodies. In mixed lymphocyte reactions (MLR) comprised of naïve CD8+ T cells co-cultured with immature (iDC) or LPS-matured monocyte-derived DCs (mDC), DuoBody-CD40×4-1BB induced DC maturation and increased T cell functionality, shown by a dose-dependent increase in HLA-DR/CD86 expression and production of IFNγ, CXCL10 and granzyme B. DC maturation induced by DuoBody-CD40×4-1BB was also observed in monocultures of iDCs expressing both targets, and was associated with a concurrent dose-dependent increase in TNFα production. Furthermore, in antigen-specific T-cell assays (CLDN6-TCR+CD8+ T cells co-cultured with CLDN6+CD40+ DCs), DuoBody-CD40×4-1BB conditionally enhanced T-cell proliferation and production of IFNγ and TNFα, and induced upregulation of the degranulation marker CD107a and granzyme B. Finally, DuoBody-CD40×4-1BB enhanced clonal expansion of human TILs derived from non-small cell lung and colon cancer patients ex vivo in a dose-dependent manner. In conclusion, by enhancing the formation of the immune synapse between CD40+ DC and 4-1BB+ T cells, DuoBody-CD40×4-1BB induced conditional activation of both cell types, resulting in DC maturation, T-cell activation and effector functions in vitro. Thereby, DuoBody-CD40×4-1BB provides a unique combination of priming and enhancing existing anti-tumor immunity. DuoBody-CD40×4-1BB is currently being evaluated in patients with advanced solid tumors in a first-in-human trial (NCT04083599).

Citation Format: Alexander Muik, Rachelle Kosoff, Friederike Gieseke, Isil Altintas, Kristina Schödel, Saskia Burm, Eliana Stanganello, Fulvia Vascotto, Aras Toker, Homer Adams, III, Esther Breij, Mustafa Diken, Tahamtan Ahmadi, Kate Sasser, Özlem Türeci, Mark Fereshteh, Ugur Sahin, Maria Jure-Kunkel. DuoBody-CD40×4-1BB (GEN1042) induces dendritic-cell maturation and enhances T-cell activation and effector functions in vitro by conditional CD40 and 4-1BB agonist activity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1846.

Abstract 1574: Preclinical evaluation of epcoritamab combined with standard of care therapies for the treatment of B-cell lymphomas

B-cell non-Hodgkin lymphoma (B-NHL) is a heterogeneous disease with an unmet medical need for new efficacious, well tolerated, off-the-shelf therapies that can combine with standard of care (SOC) regimens. Epcoritamab (GEN3013; DuoBody®-CD3×CD20) is a novel subcutaneously administered bispecific antibody with a manageable safety profile and promising preliminary anti-tumor activity in both aggressive and indolent B-NHL. Epcoritamab simultaneously binds to CD3 on T cells and to CD20-expressing tumor cells to induce potent T-cell-mediated killing. SOC treatments for B-NHL include rituximab in combination with chemotherapy regimens such as CHOP (cyclophosphamide, doxorubicin, vincristine and prednisone), bendamustine, or immunomodulatory agents such as lenalidomide. These therapies have mechanisms of action distinct from that of epcoritamab, and mostly non-overlapping adverse event profiles. Previous preclinical studies demonstrated that epcoritamab can induce effective anti-tumor activity in the presence of a rituximab analog, supporting the combination of the two in clinical trials. Here, we present in vitro studies conducted to evaluate whether epcoritamab can be used in combination with current SOC therapies for B-NHL.

Healthy donor T cells as effector cells and/or CD20-expressing B-NHL tumor cell lines were pre-treated with each individual SOC component (lenalidomide, cyclophosphamide, doxorubicin, vincristine, prednisone) to evaluate the impact on T cells and target cell lines. Next, co-cultures of pre-treated T and B-NHL cells were incubated with the same SOC component in the presence of epcoritamab, and T-cell mediated cytotoxicity and associated T-cell activation were assessed by flow cytometry. Bendamustine was added together with epcoritamab during the T-cell activation and cytotoxicity assay to assess potential antagonizing effect.

Lenalidomide enhanced T-cell activation induced by CD3 crosslinking with immobilized anti-CD3 or epcoritamab, resulting in higher potency of these T cells to exert epcoritamab-induced cytotoxicity of CD20-expressing tumor cells. T cells pre-treated with individual CHOP components were capable of mediating epcoritamab-induced cytotoxicity. Finally, bendamustine did not antagonize T-cell activation and had an additive effect on T-cell-mediated cytotoxicity by epcoritamab. These preclinical data indicate that epcoritamab-can be combined with these SOC agents.

In conclusion, these data warrant clinical evaluation of epcoritamab combinations with multiple SOC therapies. Given the promising single-agent activity of epcoritamab, these combinations may lead to deep and durable responses that can translate into improved long-term outcomes for B-NHL patients. Epcoritamab combination therapies are planned to be evaluated in a clinical trial sponsored by Genmab and Abbvie.

Citation Format: Christopher W. Chiu, Ida H. Hiemstra, Wessel ten Hagen, Rajaa Snijdewint-Nkairi, Bart de Jong, Roberto S. Oliveri, Brian Elliot, Edith Szafer-Glusman, Danita Schuurhuis, Julie Blaedel, Tahamatan Ahmadi, Esther Breij, A. Kate Sasser, Maria Jure-Kunkel. Preclinical evaluation of epcoritamab combined with standard of care therapies for the treatment of B-cell lymphomas [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1574.

Cooperative Targeting of Immunotherapy-Resistant Melanoma and Lung Cancer by an AXL-Targeting Antibody-Drug Conjugate and Immune Checkpoint Blockade

Although immune checkpoint blockade (ICB) has shown remarkable clinical benefit in a subset of patients with melanoma and lung cancer, most patients experience no durable benefit. The receptor tyrosine kinase AXL is commonly implicated in therapy resistance and may serve as a marker for therapy-refractory tumors, for example in melanoma, as we previously demonstrated. Here, we show that enapotamab vedotin (EnaV), an antibody-drug conjugate targeting AXL, effectively targets tumors that display insensitivity to immunotherapy or tumor-specific T cells in several melanoma and lung cancer models. In addition to its direct tumor cell killing activity, EnaV treatment induced an inflammatory response and immunogenic cell death in tumor cells and promoted the induction of a memory-like phenotype in cytotoxic T cells. Combining EnaV with tumor-specific T cells proved superior to either treatment alone in models of melanoma and lung cancer and induced ICB benefit in models otherwise insensitive to anti-PD-1 treatment. Our findings indicate that targeting AXL-expressing, immunotherapy-resistant tumors with EnaV causes an immune-stimulating tumor microenvironment and enhances sensitivity to ICB, warranting further investigation of this treatment combination. SIGNIFICANCE: These findings show that targeting AXL-positive tumor fractions with an antibody-drug conjugate enhances antitumor immunity in several humanized tumor models of melanoma and lung cancer.

Abstract A68: A casein kinase 2 inhibitor disorders myeloid cell differentiation by blocking CCAAT/enhancer-binding protein-alpha signaling pathway in tumor microenvironment

Myeloid cells are major components of the tumor microenvironment, which are known to suppress antitumor immunity. Casein kinase 2 (CK2), a serine/threonine protein kinase with diverse intracellular protein substrates, regulates several signaling pathways involved in tumor progression and cell differentiation. We examined the efficacy of a novel CK2 inhibitor on modulating the myeloid cells in the tumor microenvironment. Although CK2 inhibitors BMS-595 and BMS-211 moderately inhibited the tumor growth in LLC, 4T1, MC38 and CT26 tumor-bearing mice, these inhibitors drastically enhanced the antitumor efficacy of anti-CTLA4 antibody with 60% to 90% of complete rejection. Polymorphonuclear myeloid-derived suppressor cells (PMN-MDSC) and macrophages in spleens, and tumor-associated macrophages (TAM) were found to be decreased in LLC tumor-bearing mice treated with BMS-595 for 2 weeks. Murine hematopoietic progenitor cells (HPC) from bone marrow and human progenitor cells from cord blood were cultured with BMS-595 to evaluate the differentiation. BMS-595 treatment dramatically decreased the proportion of granulocytic cells, and this decrease was not caused by the direct killing nor apoptosis. Therefore, the genes regulated by transcription factors, IRF8, C/EBPα and C/EBPβ, which are involved in PMN-MDSC differentiation, were evaluated. Many genes controlled by C/EBPα were downregulated by the BMS-595 treatment in HPCs. Active p42 subunit of C/EBPα was revealed to be reduced by the BMS-595 treatment in HPCs, which are inversely correlated with the increased level of dominant negative p30 subunit of C/EBPα, in both the cytoplasm and nucleus of HPCs. Our results suggest that CK2 inhibition leads to a reduction of immune-suppressive PMN-MDSC and TAM by inhibiting C/EBPα activity, resulting in an enormous augmentation of antitumor efficacy of immunotherapy.

Citation Format: Ayumi Hashimoto, Chan Gao, Jerome Mastio, Andrew Kossenkov, Scott I. Abrams, Ashok V. Purandare, Heshani Desilva, Susan Wee, John Hunt, Maria Jure-Kunkel, Dmitry I. Gabrilovich. A casein kinase 2 inhibitor disorders myeloid cell differentiation by blocking CCAAT/enhancer-binding protein-alpha signaling pathway in tumor microenvironment [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2018 Nov 27-30; Miami Beach, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(4 Suppl):Abstract nr A68.

Anti-NKG2A mAb Is a Checkpoint Inhibitor that Promotes Anti-tumor Immunity by Unleashing Both T and NK Cells

Checkpoint inhibitors have revolutionized cancer treatment. However, only a minority of patients respond to these immunotherapies. Here, we report that blocking the inhibitory NKG2A receptor enhances tumor immunity by promoting both natural killer (NK) and CD8⁺ T cell effector functions in mice and humans. Monalizumab, a humanized anti-NKG2A antibody, enhanced NK cell activity against various tumor cells and rescued CD8⁺ T cell function in combination with PD-x axis blockade. Monalizumab also stimulated NK cell activity against antibody-coated target cells. Interim results of a phase II trial of monalizumab plus cetuximab in previously treated squamous cell carcinoma of the head and neck showed a 31% objective response rate. Most common adverse events were fatigue (17%), pyrexia (13%), and headache (10%). NKG2A targeting with monalizumab is thus a novel checkpoint inhibitory mechanism promoting anti-tumor immunity by enhancing the activity of both T and NK cells, which may complement first-generation immunotherapies against cancer.

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Blocking NKG2A unleashes both T and NK cell effector functions

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Combined blocking of the NKG2A and the PD-1 axis promotes anti-tumor immunity

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Blocking NKG2A and triggering CD16 illustrates the efficacy of dual checkpoint therapy

Inhibition of Casein Kinase 2 Disrupts Differentiation of Myeloid Cells in Cancer and Enhances the Efficacy of Immunotherapy in Mice

The role of myeloid cells as regulators of tumor progression that significantly impact the efficacy of cancer immunotherapies makes them an attractive target for inhibition. Here we explore the effect of a novel, potent, and selective inhibitor of serine/threonine protein kinase casein kinase 2 (CK2) on modulating myeloid cells in the tumor microenvironment. Although inhibition of CK2 caused only a modest effect on dendritic cells in tumor-bearing mice, it substantially reduced the amount of polymorphonuclear myeloid-derived suppressor cells and tumor-associated macrophages. This effect was not caused by the induction of apoptosis, but rather by a block of differentiation. Our results implicated downregulation of CCAAT-enhancer binding protein-α in this effect. Although CK2 inhibition did not directly affect tumor cells, it dramatically enhanced the antitumor activity of immune checkpoint receptor blockade using anti-CTLA-4 antibody. These results suggest a potential role of CK2 inhibitors in combination therapies against cancer.Significance: These findings demonstrate the modulatory effects of casein kinase 2 inhibitors on myeloid cell differentiation in the tumor microenvironment, which subsequently synergize with the antitumor effects of checkpoint inhibitor CTLA4. Cancer Res; 78(19); 5644-55. ©2018 AACR.

Interleukin-21 combined with PD-1 or CTLA-4 blockade enhances antitumor immunity in mouse tumor models

Recent advances in cancer treatment with checkpoint blockade of receptors such as CTLA-4 and PD-1 have demonstrated that combinations of agents with complementary immunomodulatory effects have the potential to enhance antitumor activity as compared to single agents. We investigated the efficacy of immune-modulatory interleukin-21 (IL-21) combined with checkpoint blockade in several syngeneic mouse tumor models. After tumor establishment, mice were administered recombinant mouse IL-21 (mIL-21) alone or in combination with blocking monoclonal antibodies against mouse PD-1 or CTLA-4. In contrast to monotherapy, IL-21 enhanced antitumor activity of mCTLA-4 mAb in four models and anti-PD-1 mAb in two models, with evidence of synergy for one or both of the combination treatments in the EMT-6 and MC38 models. The enhanced efficacy was associated with increased intratumoral CD8+ T cell infiltrates, CD8+ T cell proliferation, and increased effector memory T cells, along with decreased frequency of central memory CD8+ T cells. In vivo depletion of CD8+ T cells abolished the antitumor activities observed for both combination and monotherapy treatments, further supporting a beneficial role for CD8+ T cells. In all studies, the combination therapies were well tolerated. These results support the hypothesis that the combination of recombinant human IL-21 with CTLA-4 or PD-1 monoclonal antibodies could lead to improved outcomes in cancer patients.

Deubiquitinases A20 and CYLD modulate costimulatory signaling via CD137 (4-1BB)

TRAF2 dependent K63-polyubiquitinations have been recently shown to connect CD137 (4-1BB) stimulation to NF-κB activation. In a search of deubiquitinase enzymes (DUBs) that could regulate such a signaling route, A20 and CYLD were found to coimmunoprecipitate with CD137 and TRAF2 complexes. Indeed, overexpression of A20 or CYLD downregulated CD137-elicited ubiquitination of TRAF2 and TAK1 upon stimulation with agonist monoclonal antibodies. Moreover, overexpression of A20 or CYLD downregulated CD137-induced NF-κB activation in cultured cells and in gene-transferred hepatocytes in vivo, while silencing these deubiquitinases enhanced CD137 costimulation of primary human CD8 T cells. Therefore A20 and CYLD directly downregulate the signaling from a T and NK-cell costimulatory receptor under exploitation for cancer immunotherapy in clinical trials.

Results from an Integrated Safety Analysis of Urelumab, an Agonist Anti-CD137 Monoclonal Antibody

Purpose: Urelumab is an agonist antibody to CD137 with potential application as an immuno-oncology therapeutic. Data were analyzed to assess safety, tolerability, and pharmacodynamic activity of urelumab, including the dose selected for ongoing development in patients with advanced solid tumors and lymphoma.Experimental Design: A total of 346 patients with advanced cancers who had progressed after standard treatment received at least one dose of urelumab in one of three dose-escalation, monotherapy studies. Urelumab was administered at doses ranging from 0.1 to 15 mg/kg. Safety analyses included treatment-related and serious adverse events (AEs), as well as treatment-related AEs leading to discontinuation and death, with a focus on liver function test abnormalities and hepatic AEs.Results: Urelumab doses between 1 and 15 mg/kg given every 3 weeks resulted in a higher frequency of treatment-related AEs than 0.1 or 0.3 mg/kg every 3 weeks. Dose was the single most important factor contributing to transaminitis development, which was more frequent and severe at doses ≥1 mg/kg. At the MTD of 0.1 mg/kg every 3 weeks, urelumab was relatively well tolerated, with fatigue (16%) and nausea (13%) being the most common treatment-related AEs, and was associated with immunologic and pharmacodynamic activity demonstrated by the induction of IFN-inducible genes and cytokines.Conclusions: Integrated evaluation of urelumab safety data showed significant transaminitis was strongly associated with doses of ≥1 mg/kg. However, urelumab 0.1 mg/kg every 3 weeks was demonstrated to be safe, with pharmacodynamic activity supporting continued clinical evaluation of this dose as monotherapy and in combination with other immuno-oncology agents. Clin Cancer Res; 23(8); 1929-36. ©2016 AACR.

Abscopal Effects of Radiotherapy Are Enhanced by Combined Immunostimulatory mAbs and Are Dependent on CD8 T Cells and Crosspriming

Preclinical and clinical evidence indicate that the proimmune effects of radiotherapy can be synergistically augmented with immunostimulatory mAbs to act both on irradiated tumor lesions and on distant, nonirradiated tumor sites. The combination of radiotherapy with immunostimulatory anti-PD1 and anti-CD137 mAbs was conducive to favorable effects on distant nonirradiated tumor lesions as observed in transplanted MC38 (colorectal cancer), B16OVA (melanoma), and 4T1 (breast cancer) models. The therapeutic activity was crucially performed by CD8 T cells, as found in selective depletion experiments. Moreover, the integrities of BATF-3-dependent dendritic cells specialized in crosspresentation/crosspriming of antigens to CD8⁺ T cells and of the type I IFN system were absolute requirements for the antitumor effects to occur. The irradiation regimen induced immune infiltrate changes in the irradiated and nonirradiated lesions featured by reductions in the total content of effector T cells, Tregs, and myeloid-derived suppressor cells, while effector T cells expressed more intracellular IFNγ in both the irradiated and contralateral tumors. Importantly, 48 hours after irradiation, CD8⁺ TILs showed brighter expression of CD137 and PD1, thereby displaying more target molecules for the corresponding mAbs. Likewise, PD1 and CD137 were induced on tumor-infiltrating lymphocytes from surgically excised human carcinomas that were irradiated ex vivo These mechanisms involving crosspriming and CD8 T cells advocate clinical development of immunotherapy combinations with anti-PD1 plus anti-CD137 mAbs that can be synergistically accompanied by radiotherapy strategies, even if the disease is left outside the field of irradiation. Cancer Res; 76(20); 5994-6005. ©2016 AACR.

Abstract 4012: Improving radiotherapy abscopal effects with anti-PD1 and anti-CD137-based immunotherapy

Radiotherapy is considered an efficacious local tool to erradicate or at least control cancer progression. However, recent lines of preclinical and clinical evidence indicate that proimmune effects of radiotherapy can be synergistically augmented with immunostimulatory monoclonal antibodies (mAb) to act both on irradiated tumor lessions and on distant, non-irradiated tumor sites. The combination of radiotherapy with immunostimulatory anti-PD1 and anti-CD137 mAbs was conducive to favourable effects on distant non-irradiated tumor lesions as observed on transplanted MC38 (colorectal cancer), B16OVA (melanoma) and 4T1 (breast cancer) models. Immunotherapy and radiotherapy synergized both when irradiation was given using external beams or provided with brachytherapy. The therapeutic activity was crucially performed by CD8 T cells, as found in selective depletion experiments. The irradiation regimen induced immune infiltrate changes in the irradiated and non-irradiated lesions featured by reductions in the content of effector T cells, Tregs, and myeloid-derived supresor cells (MDSC), while effector T cells were expressing more intracellular IFN gamma in both the irradiated and contralateral tumors. Importantly, 48h following irradiation CD8+ TILs showed brighter expression of CD137 and PD-1 thereby displaying more target molecules for the activity of the corresponding monoclonal antibodies. Likewise, PD-1 and CD137 were induced on tumor infiltrating lymphocytes from surgically excised of human carcinoma lessions that were irradiated ex-vivo. These findings advocate for clinical development of immunotherapy combinations with anti-PD1 plus anti-CD137 mAbs that can be synergistically accompained by radiotherapy strategies on treatable lesions, even if leaving disease outside the irradiation field.

Citation Format: MariaE. Rodríguez-Ruiz, Inmaculada Rodriguez, Saray Garasa, Benigno Barbes, Jose Luis Solorzano, Jose Luis Perez Gracia, Sara Labiano, Arantza Azpilikueta, Elixabet Bolanos, Alfonso R. Sanchez-Paulete, M. Angela Aznar, Ana Rouzaut, Maria Jure-Kunkel, Iñaki Etxeberria, Carlos Alfaro, Carmen Oñate, Mariano Ponz, Ignacio Melero. Improving radiotherapy abscopal effects with anti-PD1 and anti-CD137-based immunotherapy. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4012.

Immunomodulatory Activity of Nivolumab in Metastatic Renal Cell Carcinoma

PURPOSE

Nivolumab, an anti-PD-1 immune checkpoint inhibitor, improved overall survival versus everolimus in a phase 3 trial of previously treated patients with metastatic renal cell carcinoma (mRCC). We investigated immunomodulatory activity of nivolumab in a hypothesis-generating prospective mRCC trial.

EXPERIMENTAL DESIGN

Nivolumab was administered intravenously every 3 weeks at 0.3, 2, or 10 mg/kg to previously treated patients and 10 mg/kg to treatment-naïve patients with mRCC. Baseline and on-treatment biopsies and blood were obtained. Clinical activity, tumor-associated lymphocytes, PD-L1 expression (Dako immunohistochemistry; ≥5% vs. <5% tumor membrane staining), tumor gene expression (Affymetrix U219), serum chemokines, and safety were assessed.

RESULTS

In 91 treated patients, median overall survival [95% confidence interval (CI)] was 16.4 months [10.1 to not reached (NR)] for nivolumab 0.3 mg/kg, NR for 2 mg/kg, 25.2 months (12.0 to NR) for 10 mg/kg, and NR for treatment-naïve patients. Median percent change from baseline in tumor-associated lymphocytes was 69% (CD3⁺), 180% (CD4⁺), and 117% (CD8⁺). Of 56 baseline biopsies, 32% had ≥5% PD-L1 expression, and there was no consistent change from baseline to on-treatment biopsies. Transcriptional changes in tumors on treatment included upregulation of IFNγ-stimulated genes (e.g., CXCL9). Median increases in chemokine levels from baseline to C2D8 were 101% (CXCL9) and 37% (CXCL10) in peripheral blood. No new safety signals were identified.

CONCLUSIONS

Immunomodulatory effects of PD-1 inhibition were demonstrated through multiple lines of evidence across nivolumab doses. Biomarker changes from baseline reflect nivolumab pharmacodynamics in the tumor microenvironment. These data may inform potential combinations. Clin Cancer Res; 22(22); 5461-71. ©2016 AACR.

Deciphering CD137 (4-1BB) signaling in T-cell costimulation for translation into successful cancer immunotherapy

CD137 (4-1BB, TNF-receptor superfamily 9) is a surface glycoprotein of the TNFR family which can be induced on a variety of leukocyte subsets. On T and NK cells, CD137 is expressed following activation and, if ligated by its natural ligand (CD137L), conveys polyubiquitination-mediated signals via TNF receptor associated factor 2 that inhibit apoptosis, while enhancing proliferation and effector functions. CD137 thus behaves as a bona fide inducible costimulatory molecule. These functional properties of CD137 can be exploited in cancer immunotherapy by systemic administration of agonist monoclonal antibodies, which increase anticancer CTLs and enhance NK-cell-mediated antibody-dependent cell-mediated cytotoxicity. Reportedly, anti-CD137 mAb and adoptive T-cell therapy strongly synergize, since (i) CD137 expression can be used to select the T cells endowed with the best activities against the tumor, (ii) costimulation of the lymphocyte cultures to be used in adoptive T-cell therapy can be done with CD137 agonist antibodies or CD137L, and (iii) synergistic effects upon coadministration of T cells and antibodies are readily observed in mouse models. Furthermore, the signaling cytoplasmic tail of CD137 is a key component of anti-CD19 chimeric antigen receptors that are used to redirect T cells against leukemia and lymphoma in the clinic. Ongoing phase II clinical trials with agonist antibodies and the presence of CD137 sequence in these successful chimeric antigen receptors highlight the importance of CD137 in oncoimmunology.

Cancer Immunotherapy with Immunomodulatory Anti-CD137 and Anti-PD-1 Monoclonal Antibodies Requires BATF3-Dependent Dendritic Cells

Weak and ineffective antitumor cytotoxic T lymphocyte (CTL) responses can be rescued by immunomodulatory mAbs targeting PD-1 or CD137. Using Batf3(-/-) mice, which are defective for cross-presentation of cell-associated antigens, we show that BATF3-dependent dendritic cells (DC) are essential for the response to therapy with anti-CD137 or anti-PD-1 mAbs. Batf3(-/-) mice failed to prime an endogenous CTL-mediated immune response toward tumor-associated antigens, including neoantigens. As a result, the immunomodulatory mAbs could not amplify any therapeutically functional immune response in these mice. Moreover, administration of systemic sFLT3L and local poly-ICLC enhanced DC-mediated cross-priming and synergized with anti-CD137- and anti-PD-1-mediated immunostimulation in tumor therapy against B16-ovalbumin-derived melanomas, whereas this function was lost in Batf3(-/-) mice. These experiments show that cross-priming of tumor antigens by FLT3L- and BATF3-dependent DCs is crucial to the efficacy of immunostimulatory mAbs and represents a very attractive point of intervention to enhance their clinical antitumor effects.

SIGNIFICANCE

Immunotherapy with immunostimulatory mAbs is currently achieving durable clinical responses in different types of cancer. We show that cross-priming of tumor antigens by BATF3-dependent DCs is a key limiting factor that can be exploited to enhance the antitumor efficacy of anti-PD-1 and anti-CD137 immunostimulatory mAbs.

Abstract 261: Nivolumab and urelumab enhance antitumor activity of human T lymphocytes engrafted in Rag2-/-IL2Rγnull immunodeficient mice

To evaluate the pharmacodynamics effects and antitumor activities of immunostimulatory mAb, we have developed a “humanized” murine model in which the receptors targeted by such mAbs become expressed. Human lymphocytes transferred into immunodeficient mice undergo activation and redistribute to organs with surface expression of hCD137 and hPD-1. Systemic lymphocyte infiltrations result in lethal xenograft-versus-host disease, which is aggravated when mice are given clinical-grade anti-hCD137 (urelumab) and anti-hPD-1 (nivolumab) mAbs. In mice engrafted with either a human colorectal carcinoma cell line (HT-29) and allogeneic human PBMCs or a primary gastric carcinoma and PBMCs from the patient, urelumab and nivolumab significantly slowed tumor growth (p&lt;0.01). Increased activated human T lymphocytes producing IFN-ϒ and decreased human regulatory T lymphocytes in the xenografted tumors may explain such therapeutic activities. These mouse models permit surrogate analyses to test and make predictions on immunotherapy strategies encompassing immunostimulatory mAbs and their combinations.

Citation Format: Miguel F. Sanmamed, Inmaculada Rodriguez, Carmen Oñate, Arantza Azpilikueta, Maria E. Rodriguez-Ruiz, Aizea Morales-Kastresana, Sara Labiano, Jose L. Perez-Gracia, Salvador Martín-Algarra, Carlos Alfaro, Kurt A. Schalper, Guillermo Mazzolini, Francesca Sarno, Manuel Hidalgo, Alan J. Korman, Maria Jure-Kunkel, Ignacio Melero. Nivolumab and urelumab enhance antitumor activity of human T lymphocytes engrafted in Rag2-/-IL2Rγnull immunodeficient mice. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 261. doi:10.1158/1538-7445.AM2015-261

Abstract 4058: Hypoxia-induced soluble CD137 in malignant cells blocks CD137L-costimulation as an immune escape mechanism

Hypoxia is a common feature in solid tumors that has been implicated in immune-evasion. In this study, we show that exposure of mouse and human tumor cell lines to hypoxic conditions (1% O2) promotes CD137 transcription. Previous studies from our group have shown that hypoxia up-regulates the co-stimulatory receptor CD137 on activated T lymphocytes and on vascular endothelial cells. However, our results show that the CD137 transcript upregulated under hypoxia in tumor cell lines is predominantly an alternatively spliced form that encodes for a soluble variant, which lacks the transmembrane domain. Accordingly, soluble CD137 (sCD137) is detectable by ELISA in the supernatant of hypoxia-exposed cell lines and in the serum of tumor-bearing mice. sCD137, as secreted by tumor cells, is able to bind to CD137-Ligand (CD137L). Our studies on primed T lymphocytes in co-culture with stable transfectants for CD137L demonstrate that tumor-secreted sCD137 prevents co-stimulation of T lymphocytes. Such an effect results from preventing the interaction of CD137L with the transmembrane forms of CD137 expressed on T lymphocytes undergoing activation. This mechanism is interpreted as a molecular strategy deployed by tumors to repress lymphocyte co-stimulation via CD137/CD137L.

Citation Format: Sara Labiano, Asís Palazón, José I. Quetglas, Elixabet Bolaños, Arantza Azpilicueta, Aizea Morales-Kastresana, Alfonso Rodriguez, Maria Rodriguez-Ruiz, Alfonso Gurpide, M Angela Aznar, Maria Jure-Kunkel, Ignacio Melero. Hypoxia-induced soluble CD137 in malignant cells blocks CD137L-costimulation as an immune escape mechanism. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4058. doi:10.1158/1538-7445.AM2015-4058

Abstract 1306: Biomarker results from a clinical trial of nivolumab in patients (pts) with metastatic renal cell carcinoma (mRCC) (CA209-009): Gene expression, serum profiling for immune markers, and multiplex tissue immunohistochemistry (IHC)

Background. A prospective study of the programmed death-1 (PD-1) inhibitor nivolumab, which shows clinical activity in mRCC (Motzer RJ, et al. JCO, 2014), reported changes in serum chemokines (CXCL9, CXCL10) and tumor T cell infiltrates consistent with PD-1 inhibition (Choueiri TK, et al. ASCO 2014; abstract 5012). Here we expand on these findings to report on immune biomarkers in tumor biopsies and peripheral blood.

Methods. Ninety-one eligible pts who had RCC with a clear cell component and measurable disease received nivolumab intravenously on day 1 of each 3 week treatment cycle. Previously treated pts were randomized to 0.3 (n = 22), 2 (n = 22), or 10 mg/kg (n = 23) nivolumab; treatment-naïve pts (n = 24) received 10 mg/kg. IHC was performed on tumor biopsies obtained at baseline (BL) and at cycle 2 day 8 (C2D8) to quantify cells bearing T cell markers (CD3/CD4/CD8/FoxP3/PD1); matched specimens were available for 53 pts. Gene expression (18,562 loci; Affymetrix) was analyzed in biopsies and peripheral whole blood obtained at BL and on treatment. Pharmacodynamic effects on transcription were evaluated for connection to immune cell lineages (Abbas AR, et al. Genes and Immunity, 2005) and for biological impact (MetaCore). Serum at BL and time points through C4D1 was analyzed for markers of inflammation (53 analytes; Myriad RBM) and antibodies against tumor antigens (30 antigens; Serametrix).

Results. IHC (n = 53 pairs) revealed a significant (P &lt; 0.01) increase in CD8+ T cells while median levels of FoxP3+/PD1+ CD4+ T cells remained &lt; 1%. Tumor expression profiling also demonstrated an on-treatment increase (&gt; 1.3-fold; P &lt; 0.01) for activated CD8+ T cell transcripts (CD8A/B, CD3D/E/G/Z, CTLA-4) and indicated enrichment for both lymphoid and myeloid lineages. Pathway analysis identified an impact on interferon signaling and on multiple components of MHC class I antigen presentation, including the antigen processing factors TAP1 and PSMB9. In peripheral blood, transcripts for T cell markers (TRAC, TRBC2, CD3G) showed significant decreases (&gt; 1.2-fold, P &lt; 0.01) at C1D2, while multiple IFNγ-responsive genes were up-regulated. Few (&lt; 30) substantive differences in pharmacodynamic effects on transcription were detected between treatment arms. At C2D8 (n = 70), serum levels of the immune markers IL8, IL18, TNFR2, MIP1β, and CD25 had increased by &gt; 30%. By C4D1, 22/61 (36%) pts demonstrated increased seroconversion against ≥ 5 tumor antigens.

Conclusions. In this first biomarker-based study of an immune checkpoint inhibitor in mRCC, immunomodulatory effects consistent with PD-1 inhibition were seen in peripheral blood and the tumor microenvironment. Ongoing phase 3 studies will provide additional evidence of the effect of nivolumab on these biomarkers (NCT01668784, NCT02231749).

Citation Format: Toni K. Choueiri, Mayer N. Fishman, Bernard Escudier, Walter M. Stadler, Scott Chasalow, Petra Ross-Macdonald, Maria Jure-Kunkel, Mario Sznol, Jason S. Simon. Biomarker results from a clinical trial of nivolumab in patients (pts) with metastatic renal cell carcinoma (mRCC) (CA209-009): Gene expression, serum profiling for immune markers, and multiplex tissue immunohistochemistry (IHC). [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1306. doi:10.1158/1538-7445.AM2015-1306

Nivolumab and Urelumab Enhance Antitumor Activity of Human T Lymphocytes Engrafted in Rag2-/-IL2Rγnull Immunodeficient Mice

A current pressing need in cancer immunology is the development of preclinical model systems that are immunocompetent for the study of human tumors. Here, we report the development of a humanized murine model that can be used to analyze the pharmacodynamics and antitumor properties of immunostimulatory monoclonal antibodies (mAb) in settings where the receptors targeted by the mAbs are expressed. Human lymphocytes transferred into immunodeficient mice underwent activation and redistribution to murine organs, where they exhibited cell-surface expression of hCD137 and hPD-1. Systemic lymphocyte infiltrations resulted in a lethal CD4(+) T cell-mediated disease (xenograft-versus-host disease), which was aggravated when murine subjects were administered clinical-grade anti-hCD137 (urelumab) and anti-hPD-1 (nivolumab). In mice engrafted with human colorectal HT-29 carcinoma cells and allogeneic human peripheral blood mononuclear cells (PBMC), or with a patient-derived gastric carcinoma and PBMCs from the same patient, we found that coadministration of urelumab and nivolumab was sufficient to significantly slow tumor growth. Correlated with this result were increased numbers of activated human T lymphocytes producing IFNγ and decreased numbers of human regulatory T lymphocytes in the tumor xenografts, possibly explaining the efficacy of the therapeutic regimen. Our results offer a proof of concept for the use of humanized mouse models for surrogate efficacy and histology investigations of immune checkpoint drugs and their combinations.

Hypoxia-induced soluble CD137 in malignant cells blocks CD137L-costimulation as an immune escape mechanism

Hypoxia is a common feature in solid tumors that has been implicated in immune evasion. Previous studies from our group have shown that hypoxia upregulates the co-stimulatory receptor CD137 on activated T lymphocytes and on vascular endothelial cells. In this study, we show that exposure of mouse and human tumor cell lines to hypoxic conditions (1% O₂) promotes CD137 transcription. However, the resulting mRNA is predominantly an alternatively spliced form that encodes for a soluble variant, lacking the transmembrane domain. Accordingly, soluble CD137 (sCD137) is detectable by ELISA in the supernatant of hypoxia-exposed cell lines and in the serum of tumor-bearing mice. sCD137, as secreted by tumor cells, is able to bind to CD137-Ligand (CD137L). Our studies on primed T lymphocytes in co-culture with stable transfectants for CD137L demonstrate that tumor-secreted sCD137 prevents co-stimulation of T lymphocytes. Such an effect results from preventing the interaction of CD137L with the transmembrane forms of CD137 expressed on T lymphocytes undergoing activation. Indeed, silencing CD137 with shRNA renders more immunogenic tumor-cell variants upon inoculation to immunocompetent mice but which readily grafted on immunodeficient or CD8⁺ T-cell-depleted mice. These mechanisms are interpreted as a molecular strategy deployed by tumors to repress lymphocyte co-stimulation via CD137/CD137L.

Multimodal imaging analysis of an orthotopic head and neck cancer mouse model and application of anti-CD137 tumor immune therapy

BACKGROUND

Recent technical progress makes sophisticated noninvasive imaging methods available for murine models. For the first time, in this study, we applied fluorodeoxyglucose (FDG)-positron emission tomography (PET)-CT and FDG-PET-MRI to a murine orthotopic model of head and neck cancer immunotherapy.

METHODS

Tumor growth of floor of the mouth tumors was evaluated by multimodal small-animal imaging using FDG-PET-CT and FDG-PET-MRI. The immunotherapeutic effects of anti-CD137 antibody therapy were examined on body weight, tumor growth, and tumor-infiltrating immune cells in longitudinal imaging studies and immunohistochemical analyses.

RESULTS

Imaging revealed aggressive, fast-growing tumors without evidence of local or distant metastases. CD137 immunotherapy decreased tumor take and growth and stabilized body weight over time. A clear case of tumor regression was demonstrated by longitudinal PET-CT.

CONCLUSION

The murine model mimics the characteristics of head and neck cancer in humans and offers excellent opportunities to investigate immunomodulatory anticancer drugs. The CD137 antibody showed antitumor effects in some therapy-responsive mice.

Agonists of Co-stimulation in Cancer Immunotherapy Directed Against CD137, OX40, GITR, CD27, CD28, and ICOS

T and natural killer (NK) lymphocytes are considered the main effector players in the immune response against tumors. Full activation of T and NK lymphocytes requires the coordinated participation of several surface receptors that meet their cognate ligands through structured transient cell-to-cell interactions known as immune synapses. In the case of T cells, the main route of stimulation is driven by antigens as recognized in the form of short polypeptides associated with major histocompatibility complex (MHC) antigen-presenting molecules. However, the functional outcome of T-cell stimulation towards clonal expansion and effector function acquisition is contingent on the contact of additional surface receptor-ligand pairs and on the actions of cytokines in the milieu. While some of those interactions are inhibitory, others are activating and are collectively termed co-stimulatory receptors. The best studied belong to either the immunoglobulin superfamily or the tumor necrosis factor-receptor (TNFR) family. Co-stimulatory receptors include surface moieties that are constitutively expressed on resting lymphocytes such as CD28 or CD27 and others whose expression is induced upon recent previous antigen priming, ie, CD137, GITR, OX40, and ICOS. Ligation of these glycoproteins with agonist antibodies actively conveys activating signals to the lymphocyte. Those signals, acting through a potentiation of the cellular immune response, give rise to anti-tumor effects in mouse models. Anti-CD137 antibodies are undergoing clinical trials with evidence of clinical activity and anti-OX40 monoclonal antibodies (mAbs) induce interesting immunomodulation effects in humans. Antibodies anti-CD27 and GITR have recently entered clinical trials. The inherent dangers of these immunomodulation strategies are the precipitation of excessive systemic inflammation or/and invigorating silent autoimmunity. Agonist antibodies, recombinant forms of the natural ligands, and polynucleotide-based aptamers constitute the pharmacologic tools to manipulate such receptors. Preclinical data suggest that the greatest potential of these agents is achieved in combined treatment strategies.

Paradoxical activation of T cells via augmented ERK signaling mediated by a RAF inhibitor

RAF inhibitors selectively block ERK signaling in BRAF-mutant melanomas and have defined a genotype-guided approach to care for this disease. RAF inhibitors have the opposite effect in BRAF wild-type tumor cells, where they cause hyperactivation of ERK signaling. Here, we predict that RAF inhibitors can enhance T cell activation, based upon the observation that these agents paradoxically activate ERK signaling in BRAF wild-type cells. To test this hypothesis, we have evaluated the effects of the RAF inhibitor BMS908662 on T cell activation and signaling in vitro and in vivo. We observe that T cell activation is enhanced in a concentration-dependent manner and that this effect corresponds with increased ERK signaling, consistent with paradoxical activation of the pathway. Furthermore, we find that the combination of BMS908662 with CTLA-4 blockade in vivo potentiates T cell expansion, corresponding with hyperactivation of ERK signaling in T cells detectable ex vivo. Lastly, this combination demonstrates superior anti-tumor activity, compared to either agent alone, in two transplantable tumor models. This study provides clear evidence that RAF inhibitors can modulate T cell function by potentiating T cell activation in vitro and in vivo. Paradoxical activation of ERK signaling in T cells offers one mechanism to explain the enhanced antitumor activity seen when RAF inhibitors are combined with CTLA-4 blockade in preclinical models.

Combined immunostimulatory monoclonal antibodies extend survival in an aggressive transgenic hepatocellular carcinoma mouse model

PURPOSE

Immunostimulatory monoclonal antibodies (ISmAb) that unleash antitumor immune responses are showing efficacy in cancer clinical trials. Anti-B7-H1 (PD-L1) monoclonal antibodies (mAb) block a critical inhibitory pathway in T cells, whereas anti-CD137 and OX40 mAbs provide T-cell costimulation. A combination of these ISmAbs (anti-CD137 + anti-OX40 + anti-B7-H1) was tested using a transgenic mouse model of multifocal and rapidly progressing hepatocellular carcinoma, in which c-myc drives transformation and cytosolic ovalbumin (OVA) is expressed in tumor cells as a model antigen.

EXPERIMENTAL DESIGN

Flow-cytometry and immunohistochemistry were used to quantify tumor-infiltrating lymphocytes (TIL) elicited by treatment and assess their activation status and cytolytic potential. Tolerance induction and its prevention/reversal by treatment with the combination of ISmAbs were revealed by in vivo killing assays.

RESULTS

The triple combination of ISmAbs extended survival of mice bearing hepatocellular carcinomas in a CD8-dependent fashion and synergized with adoptive T-cell therapy using activated OVA-specific TCR-transgenic OT-1 and OT-2 lymphocytes. Mice undergoing therapy showed clear increases in tumor infiltration by activated and blastic CD8(+) and CD4(+) T lymphocytes containing perforin/granzyme B and expressing the ISmAb-targeted receptors on their surface. The triple combination of ISmAbs did not result in enhanced OVA-specific cytotoxic T lymphocyte (CTL) activity but other antigens expressed by cell lines derived from such hepatocellular carcinomas were recognized by endogenous TILs. Adoptively transferred OVA-specific OT-1 lymphocytes into tumor-bearing mice were rendered tolerant, unless given the triple mAb therapy.

CONCLUSION

Extension of survival and dense T-cell infiltrates emphasize the translational potential of combinational immunotherapy strategies for hepatocellular carcinoma. Clin Cancer Res; 19(22); 6151-62. ©2013 AACR.

Synergy between chemotherapeutic agents and CTLA-4 blockade in preclinical tumor models

Ipilimumab, a cytotoxic T-lymphocyte antigen-4 (CTLA-4) binding agent, has proven to be an effective monotherapy for metastatic melanoma and has shown antitumor activity in trials when administered with other therapeutic agents. We hypothesized that the combination of ipilimumab with chemotherapeutic agents, such as ixabepilone, paclitaxel, etoposide, and gemcitabine, may produce therapeutic synergy based on distinct but complementary mechanisms of action for each drug and unique cellular targets. This concept was investigated using a mouse homolog of ipilimumab in preclinical murine tumor models, including SA1N fibrosarcoma, EMT-6 mammary carcinoma, M109 lung carcinoma, and CT-26 colon carcinoma. Results of CTLA-4 blockade in combination with one of various chemotherapeutic agents demonstrate that synergy occurs in settings where either agent alone was not effective in inducing tumor regression. Furthermore, when combined with CTLA-4 blockade, ixabepilone, etoposide, and gemcitabine elicited prolonged antitumor effects in some murine models with induction of a memory immune response. Future investigations are warranted to determine which specific chemo-immunotherapy combinations, if any, will produce synergistic antitumor effects in the clinical setting.

Nonclinical evaluation of the combination of mouse IL-21 and anti- mouse CTLA-4 or PD-1 blocking antibodies in mouse tumor models

3019

Background: Interleukin 21 (IL-21), a γc chain family cytokine, is produced primarily by CD4+ T cells and has many effects on immune cells, including enhancing CD8+ T cell and NK cell proliferation and cytotoxicity. Recombinant IL-21 (rIL-21) therapy resulted in objective responses in ~20% of melanoma and renal cell carcinoma patients. In mouse models, monoclonal antibody (mAb) blockade of CTLA-4 prolongs antigen-specific T cell responses, while blockade of programmed death 1 (PD-1) reverses tumor induced T cell suppression. Ipilimumab, a CTLA-4 blocking mAb, significantly improved overall survival in patients with metastatic melanoma in 2 phase III trials, and in phase I studies a PD-1 blocking mAb (nivolumab) has antitumor activity in various cancers. Side effect profiles for each mAb have been related to their mechanism and are generally manageable. It was hypothesized that combination of IL-21 plus CTLA-4 or PD-1 blockade may enhance antitumor responses, potentially leading to improved clinical activity. Methods: Preclinical studies were conducted to test the antitumor activity of mouse IL-21 (mIL-21) in combination with an anti-mouse PD-1 (mPD-1) mAb (4H2-IgG1) or with an anti-mCTLA-4 blocking mAb (9D9-IgG2b) in syngeneic mouse tumor models, including MC38, CT-26, EMT-6, and B16F10. mIL-21 was tested at doses ranging from 50-200 μg/dose, administered up to 3d/wk. mCTLA-4 mAb or mPD-1 mAb were administered 3-4x total at 200-300 μg/dose. Results: Combination treatments produced enhanced antitumor activity vs. monotherapy. In the MC38 model, mIL-21 treatment led to 30% median tumor growth inhibition (TGI) by d29, while mPD-1 mAb produced 60% median TGI and 1/10 tumor-free mice. Combination of both agents led to synergistic antitumor activity, with complete regressions (CR) in 7/10 mice and 99.9% median TGI (p=0.046). CTLA-4 mAb + mIL-21 also produced synergistic activity in the MC38 model. By d21, mIL-21 monotherapy induced 34% TGI while CTLA-4 mAb resulted in 28% TGI, with no CR in either group. Combination resulted in 6/8 mice with CR and 86% TGI (p<0.05). Conclusions: These results support the use of rIL-21+nivolumab and rIL-21+ipilimumab in recently initiated clinical trials.

Peripheral and tumor immune correlates in patients with advanced melanoma treated with combination nivolumab (anti-PD-1, BMS-936558, ONO-4538) and ipilimumab

3003^

Background: Nivolumab and ipilimumab are fully human monoclonal antibodies that block the immune checkpoint receptors PD-1 and CTLA-4, respectively. In a multi-cohort, phase I study of nivolumab/ipilimumab combination therapy in melanoma patients (pts), objective response rates up to 47% were observed (NCT01024231). Putative predictive biomarkers from peripheral blood (PB) or tumor, including tumor PD-L1 expression, absolute lymphocyte count (ALC) and PB myeloid derived suppressor cells (MDSC) were evaluated. Pharmacodynamic changes in activated and effector T cells were also assessed. Methods: Tumor PD-L1 membrane expression was assessed in archival FFPE specimens by immunohistochemistry (28-8 PD-L1 antibody). ALC was measured in serial PB samples; changes in the percentage, number and phenotype of activated CD4+ and CD8+T cells and MDSC were characterized by flow cytometry. Results: PD-L1 expression was seen in 37% (10/27) of pts, using a cut-off of 5% tumor cell membrane staining. Objective responses (OR) were seen in pts with both PD-L1 negative (8/17) and PD-L1 positive (4/10) tumors. Relative to baseline, a rise in ALC was not detected, but phenotypic changes in PB T-cell subsets, including increases in the percentage of CD4 and CD8 expressing HLA-DR, ICOS and/or Ki67 were seen with combination therapy. Low ALC (<1.0 at wk 6-7) did not preclude OR as 3 of 12 pts with low ALC responded. Of pts evaluated, OR with ≥80% reduction in tumor burden at 12 wk were seen in pts with a low frequency of pretreatment PB MDSC (3/7) but no OR were seen in pts with high MDSC (0/6). Conclusions: In this small subset of pts,OR were seen independent of PD-L1 or ALC status in contrast to prior observations with nivolumab or ipilimumab, respectively. Thus, the immune response generated by combination therapy may have unique features compared to either monotherapy. The relationship between frequency of PB MDSC and reduction in tumor burden will be further explored. Further efforts in this study and in future phase III randomized studies will investigate these and other phenotypic changes in immune cell populations and their relationship to patterns of clinical activity. Clinical trial information: NCT01024231.

Association of tumor PD-L1 expression and immune biomarkers with clinical activity in patients (pts) with advanced solid tumors treated with nivolumab (anti-PD-1; BMS-936558; ONO-4538)

3016

Background: The immune checkpoint receptor programmed death-1 (PD-1) negatively regulates T-cell activation. In a phase I study, nivolumab, a PD-1 receptor blocking antibody, demonstrated durable clinical activity. Evaluation of the expression of the PD-1 ligand, PD-L1, by IHC with the 5H1 Ab suggested a correlation between pretreatment tumor PD-L1 expression and clinical response (Topalian et al, NEJM 2012). Methods: 304 pts with non-small cell lung cancer (NSCLC, n=127), melanoma (MEL, n=107), renal cell (RCC, n=34), colorectal (n=19) or prostate cancer (n=17) received nivolumab between 2008-2012 (0.1−10 mg/kg IV Q2W) during dose escalation and/or cohort expansion. Formalin-fixed paraffin-embedded tumor tissue and peripheral blood mononuclear cells (PBMC) were analyzed to explore potential pharmacodynamic/ predictive biomarkers associated with nivolumab therapy. Tumor surface PD-L1 expression was evaluated by IHC using an automated assay based on a sensitive and specific PD-L1 mAb (28-8) distinct from 5H1. PD-L1 positivity (PD-L1+) was defined as ≥5% cell membrane staining of any intensity. Lymphocyte subsets in PBMC were measured using flow cytometry. Results: Tumor membrane PD-L1 was measured in 101 MEL and NSCLC pts. 17/38 (45%) of MEL and 31/63 (49%) of NSCLC biopsies were PD-L1+. A numerically higher objective response rate (ORR), longer progression-free survival (PFS), and overall survival (OS) was seen with PD-L1+ in MEL pts (Table).Analysis of the association of PD-L1 expression with ORR, PFS and OS in NSCLC is ongoing. A correlative analysis of pt response with pre-/post-dose levels of lymphocytes will be presented. Conclusions: These data, using a novel, automated PD-L1 IHC assay and mAb, support the hypothesis of tumor PDL1+ predicting activity of nivolumab in advanced cancer, which is being prospectively assessed in phase III trials. Clinical trial information: NCT00730639. [Table: see text]

T cell costimulation with anti-CD137 monoclonal antibodies is mediated by K63-polyubiquitin-dependent signals from endosomes

Agonist anti-CD137 (4-1BB) mAbs enhance CD8-mediated antitumor immunity. Agonist anti-human CD137 mAbs binding to four distinct epitopes on the CD137 glycoprotein costimulated T cell activation irrespective of the engaged epitope or its interference with CD137L binding. CD137 perturbation with all these agonist mAbs resulted in Ag and Ab internalization toward an endosomal vesicular compartment. Internalization was observed in activated T lymphocytes from humans and mice, not only in culture but also in Ab-injected living animals. These in vivo experiments were carried out upon systemic i.v. injections with anti-CD137 mAbs and showed CD137 internalization in tumor-infiltrating lymphocytes and in activated human T cells transferred to immunodeficient mice. Efficient CD137 internalization required K63 polyubiquitination and endocytosed CD137-containing vesicles recruited TNFR-associated factor (TRAF) 2 and were decorated with K63 polyubiquitins. CD137 stimulation activates NF-κB through a K63-linked polyubiquitination-dependent route, and CD137-associated TRAF2 becomes K63 polyubiquitinated. Consistent with a role for TRAF2 in CD137 signaling, transgenic mice functionally deficient in TRAF2 showed delayed immunotherapeutic activity of anti-CD137 mAbs. As a whole, these findings advance our knowledge of the mechanisms of action of anti-CD137 immunostimulatory mAbs such as those currently undergoing clinical trials in cancer patients.