The physiological interactome of TCR-like antibody therapeutics in human tissues

Selective binding of TCR-like antibodies that target a single tumour-specific peptide antigen presented by human leukocyte antigens (HLA) is the absolute prerequisite for their therapeutic suitability and patient safety. To date, selectivity assessment has been limited to peptide library screening and predictive modeling. We developed an experimental platform to de novo identify interactomes of TCR-like antibodies directly in human tissues using mass spectrometry. As proof of concept, we confirm the target epitope of a MAGE-A4-specific TCR-like antibody. We further determine cross-reactive peptide sequences for ESK1, a TCR-like antibody with known off-target activity, in human liver tissue. We confirm off-target-induced T cell activation and ESK1-mediated liver spheroid killing. Off-target sequences feature an amino acid motif that allows a structural groove-coordination mimicking that of the target peptide, therefore allowing the interaction with the engager molecule. We conclude that our strategy offers an accurate, scalable route for evaluating the non-clinical safety profile of TCR-like antibody therapeutics prior to first-in-human clinical application.

Gut Microbiota Is Associated with Onset and Severity of Type 1 Diabetes in Nonobese Diabetic Mice Treated with Anti-PD-1

Our bodies are home to individual-specific microbial ecosystems that have recently been found to be modified by cancer immunotherapies. The interaction between the gut microbiome and islet autoimmunity leading to type I diabetes (T1D) is well described and highlights the microbiome contribution during the onset and T1D development in animals and humans. As cancer immunotherapies induce gut microbiome perturbations and immune-mediated adverse events in susceptible patients, we hypothesized that NOD mice can be used as a predictive tool to investigate the effects of anti-PD-1 treatment on the onset and severity of T1D, and how microbiota influences immunopathology. In this longitudinal study, we showed that anti-PD-1 accelerated T1D onset, increased glutamic acid decarboxylase-reactive T cell frequency in spleen, and precipitated destruction of β cells, triggering high glucose levels and pancreatic islet reduction. Anti-PD-1 treatment also resulted in temporal microbiota changes and lower diversity characteristic of T1D. Finally, we identified known insulin-resistance regulating bacteria that were negatively correlated with glucose levels, indicating that anti-PD-1 treatment impacts the early gut microbiota composition. Moreover, an increase of mucin-degrading Akkermansia muciniphila points to alterations of barrier function and immune system activation. These results highlight the ability of microbiota to readily respond to therapy-triggered pathophysiological changes as rescuers (Bacteroides acidifaciens and Parabacteroides goldsteinii) or potential exacerbators (A. muciniphila). Microbiome-modulating interventions may thus be promising mitigation strategies for immunotherapies with high risk of immune-mediated adverse events.

Immune-infiltrated kidney organoid-on-chip model for assessing T cell bispecific antibodies

T cell bispecific antibodies (TCBs) are the focus of intense development for cancer immunotherapy. Recently, peptide-MHC (major histocompatibility complex)-targeted TCBs have emerged as a new class of biotherapeutics with improved specificity. These TCBs simultaneously bind to target peptides presented by the polymorphic, species-specific MHC encoded by the human leukocyte antigen (HLA) allele present on target cells and to the CD3 coreceptor expressed by human T lymphocytes. Unfortunately, traditional models for assessing their effects on human tissues often lack predictive capability, particularly for "on-target, off-tumor" interactions. Here, we report an immune-infiltrated, kidney organoid-on-chip model in which peripheral blood mononuclear cells (PBMCs) along with nontargeting (control) or targeting TCB-based tool compounds are circulated under flow. The target consists of the RMF peptide derived from the intracellular tumor antigen Wilms' tumor 1 (WT1) presented on HLA-A2 via a bivalent T cell receptor-like binding domain. Using our model, we measured TCB-mediated CD8+ T cell activation and killing of RMF-HLA-A2-presenting cells in the presence of PBMCs and multiple tool compounds. DP47, a non-pMHC-targeting TCB that only binds to CD3 (negative control), does not promote T cell activation and killing. Conversely, the nonspecific ESK1-like TCB (positive control) promotes CD8+ T cell expansion accompanied by dose-dependent T cell-mediated killing of multiple cell types, while WT1-TCB* recognizing the RMF-HLA-A2 complex with high specificity, leads solely to selective killing of WT1-expressing cells within kidney organoids under flow. Our 3D kidney organoid model offers a platform for preclinical testing of cancer immunotherapies and investigating tissue-immune system interactions.

Patient-derived micro-organospheres enable clinical precision oncology

Patient-derived xenografts (PDXs) and patient-derived organoids (PDOs) have been shown to model clinical response to cancer therapy. However, it remains challenging to use these models to guide timely clinical decisions for cancer patients. Here, we used droplet emulsion microfluidics with temperature control and dead-volume minimization to rapidly generate thousands of micro-organospheres (MOSs) from low-volume patient tissues, which serve as an ideal patient-derived model for clinical precision oncology. A clinical study of recently diagnosed metastatic colorectal cancer (CRC) patients using an MOS-based precision oncology pipeline reliably assessed tumor drug response within 14 days, a timeline suitable for guiding treatment decisions in the clinic. Furthermore, MOSs capture original stromal cells and allow T cell penetration, providing a clinical assay for testing immuno-oncology (IO) therapies such as PD-1 blockade, bispecific antibodies, and T cell therapies on patient tumors.

Micro-organospheres retain patient tumor microenvironment for precision immuno-oncology

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Background: Current patient-derived organoid (PDO) models are largely devoid of immune components. We developed a precision microfluidic and membrane platform to generate patient-derived micro-organospheres (MOS) that retain tumor-resident immune and stromal components for personalized immuno-oncology (IO) assays. Methods: MOS were generated from lung, kidney, and colorectal cancer patients. The composition and function of patient tumor-resident immune cells in MOS were characterized by flow cytometry, single-cell RNA-seq, antibody staining, and TCR-seq. High-content and longitudinal imaging with AI analyses were used to quantify tumor cell death and immune cell dynamics inside MOS in response to IO therapies including checkpoint inhibitors, T cell bispecific antibodies, and adoptive tumor infiltrating lymphocyte (TIL) therapies, followed by single-cell analyses. Results: Tumor and stromal cells quickly form tissue niches inside MOS to sustain the viability and function of encapsulated immune cells. MOS derived from lung and kidney cancer patients respond to Nivolumab, indicated by the Annexin V apoptosis marker. ESK1* (TCB antibody targeting HLA-A2/WT1) induces killing in eight lung tumor patients derived MOS. We further developed a MOS T-cell potency assay as autologous TILs or PBMC efficiently infiltrate MOS from lung, kidney and CRC patients and induce tumor cell apoptosis. Adjunctive therapies combining TCB with TILs enhanced the potency of adoptive cell therapy against lung tumor. Based on the data, three ongoing and upcoming personalize IO clinical trials will further validate the ability of the MOS assay to predict patient response to TCB, checkpoint combinations, and adoptive cell therapy. Conclusions: MOS provide a rapid and scalable personalized platform for developing and testing IO therapies such as checkpoint inhibitors, bispecific antibodies, and T cell therapies on patient tumor models that still retain the original tumor microenvironments.

Src/lck inhibitor dasatinib reversibly switches off cytokine release and T cell cytotoxicity following stimulation with T cell bispecific antibodies

Background

T cell engagers are bispecific antibodies recognizing, with one moiety, the CD3ε chain of the T cell receptor and, with the other moiety, specific tumor surface antigens. Crosslinking of CD3 upon simultaneous binding to tumor antigens triggers T cell activation, proliferation and cytokine release, leading to tumor cell killing. Treatment with T cell engagers can be associated with safety liabilities due to on-target on-tumor, on-target off-tumor cytotoxic activity and cytokine release syndrome (CRS). Tyrosine kinases such as SRC, LCK or ZAP70 are involved in downstream signaling pathways after engagement of the T cell receptor and blocking these kinases might serve to abrogate T cell activation when required (online supplemental material 1). Dasatinib was previously identified as a potent kinase inhibitor that switches off CAR T cell functionality.

Methods

Using an in vitro model of target cell killing by human peripheral blood mononuclear cells, we assessed the effects of dasatinib combined with 2+1 T cell bispecific antibodies (TCBs) including CEA-TCB, CD19-TCB or HLA-A2 WT1-TCB on T cell activation, proliferation and target cell killing measured by flow cytometry and cytokine release measured by Luminex. To determine the effective dose of dasatinib, the Incucyte system was used to monitor the kinetics of TCB-mediated target cell killing in the presence of escalating concentrations of dasatinib. Last, the effects of dasatinib were evaluated in vivo in humanized NSG mice co-treated with CD19-TCB. The count of CD20⁺ blood B cells was used as a readout of efficacy of TCB-mediated killing and cytokine levels were measured in the serum.

Results

Dasatinib concentrations above 50 nM prevented cytokine release and switched off-target cell killing, which were subsequently restored on removal of dasatinib. In addition, dasatinib prevented CD19-TCB-mediated B cell depletion in humanized NSG mice. These data confirm that dasatinib can act as a rapid and reversible on/off switch for activated T cells at pharmacologically relevant doses as they are applied in patients according to the label.

Conclusion

Taken together, we provide evidence for the use of dasatinib as a pharmacological on/off switch to mitigate off-tumor toxicities or CRS by T cell bispecific antibodies.

Cytokine Release Syndrome By T-cell-Redirecting Therapies: Can We Predict and Modulate Patient Risk?

T-cell-redirecting therapies are promising new therapeutic options in the field of cancer immunotherapy, but the development of these modalities is challenging. A commonly observed adverse event in patients treated with T-cell-redirecting therapies is cytokine release syndrome (CRS). Its clinical manifestation is a burden on patients, and continues to be a big hurdle in the clinical development of this class of therapeutics. We review different T-cell-redirecting therapies, discuss key factors related to cytokine release and potentially leading to CRS, and present clinical mitigation strategies applied for those modalities. We propose to dissect those risk factors into drug-target-disease-related factors and individual patient risk factors. Aiming to optimize the therapeutic intervention of these modalities, we illustrate how the knowledge on drug-target-disease-related factors, such as target expression, binding affinity, and target accessibility, can be leveraged in a model-based framework and highlight with case examples how modeling and simulation is applied to guide drug discovery and development. We draw attention to the current gaps in predicting the individual patient's risk towards a high-grade CRS, which requires further considerations of risk factors related, but not limited to, the patient's demographics, genetics, underlying pathologies, treatment history, and environmental exposures. The drug-target-disease-related factors together with the individual patient's risk factors can be regarded as the patient's propensity for developing CRS in response to therapy. As an outlook, we suggest implementing a risk scoring system combined with mechanistic modeling to enable the prediction of an individual patient's risk of CRS for a given therapeutic intervention.

CD25-Treg-depleting antibodies preserving IL-2 signaling on effector T cells enhance effector activation and antitumor immunity

Intratumoral regulatory T cell (Treg) abundance associates with diminished anti-tumor immunity and poor prognosis in human cancers. Recent work demonstrates that CD25, the high affinity receptor subunit for IL-2, is a selective target for Treg depletion in mouse and human malignancies; however, anti-human CD25 antibodies have failed to deliver clinical responses against solid tumors due to bystander IL-2 receptor signaling blockade on effector T cells, which limits their anti-tumor activity. Here we demonstrate potent single-agent activity of anti-CD25 antibodies optimized to deplete Tregs whilst preserving IL-2-STAT5 signaling on effector T cells, and demonstrate synergy with immune checkpoint blockade in vivo. Pre-clinical evaluation of an anti-human CD25 (RG6292) antibody with equivalent features demonstrates, in both non-human primates and humanized mouse models, efficient Treg depletion with no overt immune-related toxicities. Our data supports the clinical development of RG6292 and evaluation of novel combination therapies incorporating non-IL-2 blocking anti-CD25 antibodies in clinical studies.

Abstract 6135: Tumor-bearing non-human primates: An unrivaled model for translational cancer immunology research

The translatability of mouse models for the clinical development of cancer immunotherapies remains limited because of substantial differences between the murine and the human immune systems, as well as dissimilarities in the tumor biology. Non-human primates (NHPs) display good homologies towards the human immune system, based on the development of vaccines to several human pathogens. Tumor-bearing monkeys (TBMs) are NHPs that spontaneously developed cancer with progression patterns similar to humans, potentially bridging the experimental gap between early preclinical models and cancer patients treated with immunotherapeutic agents.

TBMs are prevalently rhesus macaques (Macaca mulata) and the most common cancer types are of gastrointestinal, urogenital and endocrine origin. Rhesus macaques are genetically similar to humans and share many characteristics of aging. In both, humans and rhesus macaques, cancer incidence increases with age with the greatest incidence in those over 60 years of age and 20 years, respectively.

TBMs were recently employed to assess the tumor targeting and the pharmacodynamics of the FAP-expressing tumor stroma-targeted immunocytokine FAP-IL2v (Evers et al, AACR 2014, Abstract 2592) and costimulatory agonist FAP-4-1BBL (Claus et al, Science translational Medicine, 2019). In the latter study, we could show targeting of FAP-4-1BBL to FAP-expressing tumor stroma and lymph nodes in a colorectal cancer-bearing rhesus monkey. These data were the basis to investigate tumor targeting of FAP-4-1BBL in an on-going clinical imaging study.

In the present work, we validated further TBMs as translational models for cancer immunotherapy, by performing an imaging/biomarker study in animals exposed to a second FAP-targeted TNFRSF agonist. Two breast cancer-bearing rhesus monkeys (one triple-negative and one Luminal A) were first pre-immunized with a diphtheria/pertussis/tetanus (DTP) vaccine, and then exposed to a single injection of the TNFRSF agonist. In both animals, we could measure a strong systemic immune activation, induction of the TNFRSF agonist in T cells and also tumor regression. These observations validated the applied pre-immunization strategy to induce the TNFRSF protein expression, and confirmed the target to be pursued in the clinical setting.

In conclusion, we consider TBMs as valuable translational animal models to generate proof-of-mechanism evidence in small “signal-seeking” preclinical studies. Tumor targeting, biodistribution, peripheral and intra-tumoral pharmacodynamic activity, pharmacokinetics, immunogenicity, intra-tumoral metabolic activity and tumor regression can all be assessed in TBMs. Because of the similar tumor stroma biology shared between humans and rhesus macaques, TBMs are particularly well suited to test FAP-targeting agents. We anticipate that testing cancer immunotherapy compounds in TBMs could be of high predictability for clinical behavior.

Citation Format: Maurizio Ceppi, Michael Hettich, Volker Teichgräber, Wouter Driessen, Dietrich Tuerck, Estelle Marrer-Berger, Stefan Evers, Flavio Crameri, Bruno Gomes, Jürgen Bachl, Christian Klein, Christina Claus, Maria Amann, Oliver Krieter, Greg Dugan, David Caudell, Jason Grayson, Sai Kumar Solingapuram Kiran, Mark Cline. Tumor-bearing non-human primates: An unrivaled model for translational cancer immunology research [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 6135.

Abstract 4553: The CD25 antibody RG6292 selectively depletes Tregs while preserving IL-2 signaling and CTL activity for tumor control

Despite the advances in cancer immunotherapy, in particular in the field of checkpoint inhibitors (CPI), many patients fail to respond (primary resistance) or initially benefit but then progress upon treatment (secondary resistance). High regulatory T-cell (Treg) counts correlate with poor prognosis and reduced responsiveness to CPI therapy in humans, underscoring their potential as an immunotherapy target. Clinical attempts aiming to lower Treg counts, however, either failed to deliver convincing Treg reduction or lacked specificity for Treg over tumor antigen specific cytotoxic T cells (CTL). CD25 (the interleukin-2 receptor alpha (IL-2Ra) chain) is a recently revisited target for Treg depletion. For privileged access to IL-2, activated CTL up-regulate CD25 expression only transiently during clonal expansion. Further confirmation of an > 20 fold higher cell surface expression of CD25 on Tregs versus CTLs in human malignancies is provided. The novel compound RG6292 was developed as an ADCC and ADCP competent monoclonal antibody of human IgG1 isotype with afucosylated glycans in the Fc region. RG6292 binds with low monovalent affinity (KD 250 nM) to the extracellular domain of CD25 antigen. A high density of CD25 receptors promotes bivalent avidity of RG6292 increasing its binding strength to CD25 by at least 100 fold (KD 2-3 nM). RG6292 selectively favors the depletion of CD25 high Tregs over CD25 low activated CTLs, here shown in comparison to ipilimumab and mogamulizumab in human αCD3 activated PBMC, human tumor explants and immunopharmacodynamic studies in tumor bearing (BxPC-3), stem cell humanized mice and cynomolgus monkeys. IL-2 is an essential prerequisite for clonal expansion of CTLs, which is necessary to generate effective anti-tumor responses. Earlier immunosuppressant anti-CD25 antibodies (e.g. daclizumab and basiliximab) interfered with the formation of the high affinity IL-2R complex. Their evidenced lack of therapeutic activity in immunoncology tempered enthusiasm and highlights the pivotal role of IL-2. RG6292 is the first anti-human CD25 antibody developed to deplete Tregs selectively while fully preserving IL-2 signaling and CTL activity. Pre-clinically, a single administration of the RG6292 surrogate effectively promoted eradication of established tumors in several tumor mouse models and synergized with CPI in models of CPI resistance. RG6292 is expected to unleash the potential of selective Treg depletion while allowing for unrestricted access of IL 2 to CTLs and could therefore result in clinically superiority compared to other Treg depleting antibodies. RG6292 provides a novel therapeutic approach to alleviate a major mechanism of immune suppression in the tumor microenvironment. Clinical testing is currently ongoing to evaluate the safety and tolerability of RG6292 in patients with advanced solid tumors (NCT04158583).

Citation Format: Maria Amann, Gabriel Schnetzler, Kolben Theresa, Isabelle Solomon, Christophe Boetsch, Estelle Marrer-Berger, Reto Flury, Claudio Murgia, Vaios Karanikas, Johannes Sam, Roger Sutmuller, Jan Eckmann, Hans Koll, Sara Belli, Frederic Arce Vargas, Dimitrios Zervas, Chen Qing, Mark A. Brown, Josephine Salimu, Anne Goubier, Sebastian Neumann, Karl S. Peggs, Sergio A. Quezada. The CD25 antibody RG6292 selectively depletes Tregs while preserving IL-2 signaling and CTL activity for tumor control [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 4553.

Safety testing of monoclonal antibodies in non-human primates: Case studies highlighting their impact on human risk assessment

Monoclonal antibodies (mAbs) are improving the quality of life for patients suffering from serious diseases due to their high specificity for their target and low potential for off-target toxicity. The toxicity of mAbs is primarily driven by their pharmacological activity, and therefore safety testing of these drugs prior to clinical testing is performed in species in which the mAb binds and engages the target to a similar extent to that anticipated in humans. For highly human-specific mAbs, this testing often requires the use of non-human primates (NHPs) as relevant species. It has been argued that the value of these NHP studies is limited because most of the adverse events can be predicted from the knowledge of the target, data from transgenic rodents or target-deficient humans, and other sources. However, many of the mAbs currently in development target novel pathways and may comprise novel scaffolds with multi-functional domains; hence, the pharmacological effects and potential safety risks are less predictable. Here, we present a total of 18 case studies, including some of these novel mAbs, with the aim of interrogating the value of NHP safety studies in human risk assessment. These studies have identified mAb candidate molecules and pharmacological pathways with severe safety risks, leading to candidate or target program termination, as well as highlighting that some pathways with theoretical safety concerns are amenable to safe modulation by mAbs. NHP studies have also informed the rational design of safer drug candidates suitable for human testing and informed human clinical trial design (route, dose and regimen, patient inclusion and exclusion criteria and safety monitoring), further protecting the safety of clinical trial participants.