Antibody Blockade Research Articles

A bispecific antibody targeting HLA-DQ2.5-gluten peptides potently blocks gluten-specific T cells induced by gluten ingestion in patients with celiac disease

The gluten-free diet for celiac disease (CeD) is restrictive and often fails to induce complete symptom and/or mucosal disease remission. Central to CeD pathogenesis is the gluten-specific CD4+ T cell that is restricted by HLA-DQ2.5 in over 85% of CeD patients, making HLA-DQ2.5 an attractive target for suppressing gluten-dependent immunity. Recently, a novel anti-HLA-DQ2.5 antibody that specifically recognizes the complexes of HLA-DQ2.5 and multiple gluten epitopes was developed (DONQ52). ObjectiveTo assess the ability of DONQ52 to inhibit CeD patient-derived T-cell responses to the most immunogenic gluten peptides that encompass immunodominant T cell epitopes. MethodsWe employed an in vivo gluten challenge model in patients with CeD that affords a quantitative readout of disease-relevant gluten-specific T-cell responses. HLA-DQ2.5+ CeD patients consumed food containing wheat, barley, or rye for 3 days with collection of blood before (D1) and 6 days after (D6) commencing the challenge. Peripheral blood mononuclear cells were isolated and assessed in an interferon (IFN)-γ enzyme-linked immunosorbent spot assay (ELISpot) testing responses to gluten peptides encompassing a series of immunodominant T cell epitopes. The inhibitory effect of DONQ52 (4 or 40 μg/mL) was assessed and compared to pan-HLA-DQ blockade (SPVL3 antibody). ResultsIn HLA-DQ2.5+ CeD patients, DONQ52 reduced T cell responses to all wheat gluten peptides to an equivalent or more effective degree than pan-HLA-DQ antibody blockade. It reduced T cell responses to a cocktail of the most immunodominant wheat epitopes by a median of 87% (IQR 72–92). Notably, DONQ52 also substantially reduced T-cell responses to dominant barley hordein and rye secalin derived peptides. DONQ52 had no effect on T-cell responses to non-gluten antigens. ConclusionDONQ52 can significantly block HLA-DQ2.5-restricted T cell responses to the most highly immunogenic gluten peptides in CeD. Our findings support in vitro data that DONQ52 displays selectivity and broad cross-reactivity against multiple gluten peptide:HLA-DQ2.5 complexes. This work provides proof-of-concept multi-specific antibody blockade has the potential to meaningfully inhibit pathogenic gluten-specific T-cell responses in CeD and supports ongoing therapeutic development.

Upregulation of Immune checkpoint PD-L1 in Colon cancer cell lines and activation of T cells by Leuconostoc mesenteroides

Globally colorectal cancer ranks as the third most widespread disease and the third leading cause of cancer-associated mortality. Immunotherapy treatments like PD-L1 blockade have been used to inhibit the PD-L1 legend, which boosts the activity of cytotoxic T lymphocytes. Recently, studies suggest that some probiotics could potentially enhance the effectiveness of immunotherapy treatments for cancer patients. We found that in Caco-2 and HT-29 cells, the live Leuconostoc mesenteroides treatment resulted an increase in the PD-L1 expression and this treatment stimulated interferon-gamma (IFN-γ) production in Jurkat T-cells. Due to the well-established ability of IFN-γ to enhance PD-L1 expression, the combination of IFN-γ and L. mesenteroides was used in colon cancer cell lines and a resulting remarkable increase of over tenfold in PD-L1 expression was obtained. Interestingly, when L. mesenteroides and IFN-γ are present, the blockage of PD-L1 using PD-L1 antibodies not only improved the viability of Jurkat T-cells but also significantly boosted the levels of IFN-γ and IL-2, the T-cells activation marker cytokines. In addition to upregulating PD-L1, L. mesenteroides also activated Toll-like receptors (TLRs) and NOD-like receptors (NODs) pathways, specifically through TLR2 and NOD2, while also exerting a suppressive effect on autophagy in colon cancer cell lines. In conclusion, our findings demonstrate a significant upregulation of PD-L1 expression in colon cancer cells upon co-culturing with L. mesenteroides. Moreover, the presence of PD-L1 antibodies during co-culturing activates Jurkat T cells. The observed enhancement in PD-L1 expression may be attributed to the inhibition of the Autophagy pathway or activation of the hippo pathway.Graphical abstract textThe administration of Live Lactobacillus mesenteroides on colon cancer cells leads to the elevation of PD-L1, with a further increase observed in the presence of IFN-γ. Co-cultivation of Live L. mesenteroides with colon cancer cells in conjunction with anti-PD-L1 blockade antibody results in the enhanced viability of T cells.Key PointsCo-culturing L. mesenteroides increases PD-L1 gene and protein transaction in colon cancer.L. mesenteroides existing enhances T cells viability and activity.GPCR41/42 is a possible link between L. mesenteroides, YAP-1 and PD-L1.

Herpes virus entry mediator signaling blockade produces mortality in neonatal sepsis through induced cardiac dysfunction.

Sepsis remains a major source of morbidity and mortality in neonates, and characterization of immune regulation in the neonatal septic response remains limited. HVEM is a checkpoint regulator which can both stimulate or inhibit immune responses and demonstrates altered expression after sepsis. We hypothesized that signaling via HVEM would be essential for the neonatal response to sepsis, and that therefore blockade of this pathway would improve survival to septic challenge. To explore this, neonatal mice were treated with cecal slurry (CS), CS with Anti-HVEM antibody (CS-Ab) or CS with isotype (CS-IT) and followed for 7-day survival. Mice from all treatment groups had thymus, lung, kidney and peritoneal fluid harvested, weighed, and stained for histologic evaluation, and changes in cardiac function were assessed with echocardiography. Mortality was significantly higher for CS-Ab mice (72.2%) than for CS-IT mice (22.2%). CS resulted in dysregulated alveolar remodeling, but CS-Ab lungs demonstrated significantly less dysfunctional alveolar remodeling than CS alone (MCL 121.0 CS vs. 87.6 CS-Ab), as well as increased renal tubular vacuolization. No morphologic differences in alveolar septation or thymic karyorrhexis were found between CS-Ab and CS-IT. CS-Ab pups exhibited a marked decrease in heart rate (390.3 Sh vs. 342.1 CS-Ab), stroke volume (13.08 CS-IT vs. 8.83 CS-Ab) and ultimately cardiac output (4.90 Sh vs. 3.02 CS-Ab) as well as a significant increase in ejection fraction (73.74 Sh vs. 83.75 CS-Ab) and cardiac strain (40.74 Sh vs. 51.16 CS-Ab) as compared to CS-IT or Sham animals. While receptor ligation of aspects of HVEM signaling, via antibody blockade, appears to mitigate aspects of lung injury and thymic involution, stimulatory signaling via HVEM still seems to be necessary for vascular and hemodynamic resilience and overall neonatal mouse survival in response to this experimental polymicrobial septic insult. This dissonance in the activity of anti-HVEM neutralizing antibody in neonatal animals speaks to the differences in how septic cardiac dysfunction should be considered and approached in the neonatal population.

Myeloid cell expression of CD200R is modulated in active TB disease and regulates Mycobacterium tuberculosis infection in a biomimetic model.

A robust immune response is required for resistance to pulmonary tuberculosis (TB), the primary disease caused by Mycobacterium tuberculosis (Mtb). However, pharmaceutical inhibition of T cell immune checkpoint molecules can result in the rapid development of active disease in latently infected individuals, indicating the importance of T cell immune regulation. In this study, we investigated the potential role of CD200R during Mtb infection, a key immune checkpoint for myeloid cells. Expression of CD200R was consistently downregulated on CD14+ monocytes in the blood of subjects with active TB compared to healthy controls, suggesting potential modulation of this important anti-inflammatory pathway. In homogenized TB-diseased lung tissue, CD200R expression was highly variable on monocytes and CD11b+HLA-DR+ macrophages but tended to be lowest in the most diseased lung tissue sections. This observation was confirmed by fluorescent microscopy, which showed the expression of CD200R on CD68+ macrophages surrounding TB lung granuloma and found expression levels tended to be lower in macrophages closest to the granuloma core and inversely correlated with lesion size. Antibody blockade of CD200R in a biomimetic 3D granuloma-like tissue culture system led to significantly increased Mtb growth. In addition, Mtb infection in this system reduced gene expression of CD200R. These findings indicate that regulation of myeloid cells via CD200R is likely to play an important part in the immune response to TB and may represent a potential target for novel therapeutic intervention.

PD-1 knockout on cytotoxic primary murine CD8+ T cells improves their motility in retrovirus infected mice.

Cytotoxic T lymphocyte (CTL) motility is an important feature of effective CTL responses and is impaired when CTLs become exhausted, e.g. during chronic retroviral infections. A prominent T cell exhaustion marker is programmed cell death protein 1 (PD-1) and antibodies against the interaction of PD-1 and PD-ligand 1 (PD-L1) are known to improve CTL functions. However, antibody blockade affects all PD-1/PD-L1-expressing cell types, thus, the observed effects cannot be attributed selectively to CTLs. To overcome this problem, we performed CRISPR/Cas9 based knockout of the PD-1 coding gene PDCD1 in naïve Friend Retrovirus (FV)-specific CTLs. We transferred 1,000 of these cells into mice where they proliferated upon FV-infection. Using intravital two-photon microscopy we visualized CTL motility in the bone marrow and evaluated cytotoxic molecule expression by flow cytometry. Knockout of PDCD1 improved the CTL motility at 14 days post infection and enhanced the expression of cytotoxicity markers. Our data show the potential of genetic tuning of naive antiviral CTLs and might be relevant for future designs of improved T cell-mediated therapies.

Core-shell nanomedicine based on multifunctional tetrahedral DNA nanostructures for synergistic enhancement of tumor chemodynamic/chemo-immunotherapy

Immune checkpoint blockade therapy has made great strides in cancer treatment, but conventional immune checkpoint blockade antibodies often lead to overactivation of the immune system and severe immune-related adverse effects. Herein, we report the design of a nanomedicine (denoted as CPD@M−TDN) based on multifunctional tetrahedral DNA nanostructures (M−TDN). In this system, a bimetallic metal–organic framework (Cu/ZIF-8) is synthesized as the core; doxorubicin-loaded polydopamine acts as a shell to reduce the immunogenicity of the nanomaterials in peripheral blood. Finally, the CpG oligodeoxynucleotides and PD-L1 aptamer-based M−TDN are coupled to the core–shell structure nanomedicine through the biotin-avidin-system. Under the acidic tumor microenvironment, the decomposition of Cu/ZIF-8 and the release of copper ions and doxorubicin can lead to immunogenic death of tumor cells through chemodynamic/chemotherapy. Furthermore, the M−TDN has the dual effects of weakening the immunosuppressive microenvironment with PD-L1 aptamer and promoting dendritic cell activation with the immunostimulant CpG. Overall, the developed CPD@M−TDN can effectively enhance the response rate to immunotherapy and has excellent potential in the field of integrated tumor treatment.

Noncovalently particle-anchored cytokines with prolonged tumor retention safely elicit potent antitumor immunity.

Preclinical studies have shown that immunostimulatory cytokines elicit antitumor immune responses but their clinical use is limited by severe immune-related adverse events upon systemic administration. Here, we report a facile and versatile strategy for noncovalently anchoring potent Fc-fused cytokine molecules to the surface of size-discrete particles decorated with Fc-binding peptide for local administration. Following intratumoral injection, particle-anchored Fc cytokines exhibit size-dependent intratumoral retention. The 1-micrometer particle prolongs intratumoral retention of Fc cytokine for over a week and has minimal systemic exposure, thereby eliciting antitumor immunity while eliminating systemic toxicity caused by circulating cytokines. In addition, the combination of these particle-anchored cytokines with immune checkpoint blockade antibodies safely promotes tumor regression in various syngeneic tumor models and genetically engineered murine tumor models and elicits systemic antitumor immunity against tumor rechallenge. Our formulation strategy renders a safe and tumor-agnostic approach that uncouples cytokines' immunostimulatory properties from their systemic toxicities for potential clinical application.

Mesothelin CAR-T cells expressing tumor-targeted immunocytokine IL-12 yield durable efficacy and fewer side effects

Chimeric antigen receptor (CAR)-modified T cell therapy has achieved remarkable efficacy in treating hematological malignancies, but it confronts many challenges in treating solid tumors, such as the immunosuppressive microenvironment of the solid tumors. These factors reduce the antitumor activity of CAR-T cells in clinical trials. Therefore, we used the immunocytokine interleukin-12 (IL-12) to enhance the efficacy of CAR-T cell therapy. In this study, we engineered CAR-IL12R54 T cells that targeted mesothelin (MSLN) and secreted a single-chain IL-12 fused to a scFv fragment R54 that recognized a different epitope on mesothelin. The evaluation of the anti-tumor activity of the CAR-IL12R54 T cells alone or in combination with anti-PD-1 antibody in vitro and in vivo was followed by the exploration of the functional mechanism by which the immunocytokine IL-12 enhanced the antitumor activity. CAR-IL12R54 T cells had potency to lyse mesothelin positive tumor cells in vitro. In vivo studies demonstrated that CAR-IL12R54 T cells were effective in controlling the growth of established tumors in a xenograft mouse model with fewer side effects than CAR-T cells that secreted naked IL-12. Furthermore, combination of PD-1 blockade antibody with CAR-IL12R54 T cells elicited durable anti-tumor responses. Mechanistic studies showed that IL12R54 enhanced Interferon-γ (IFN-γ) production and dampened the activity of regulatory T cells (Tregs). IL12R54 also upregulated CXCR6 expression in the T cells through the NF-κB pathway, which facilitated T cell infiltration and persistence in the tumor tissues. In summary, the studies provide a good therapeutic option for the clinical treatment of solid tumors.

Abstract 6444: Assessing cytotoxic T cell responses to immune checkpoint inhibitors in murine and human tumor samples using metabolic imaging

Abstract Background Immune checkpoint inhibitors (ICI) have revolutionized cancer treatment. Unfortunately, existing FDA approved biomarkers do not accurately predict which patients will respond. The Elephas Cybrid™ platform aims to improve ICI response prediction by imaging a patient’s biopsy treated with ICI ex vivo. Multiphoton microscopy (MPM) is a powerful imaging technique to interrogate the biological changes in live tumor fragments (LTFs) following ICI treatment. MPM allows rapid visualization of biological processes in 3D living tissues in a non-destructive fashion allowing for longitudinal assessment of a sample. We and others have used label-free metabolic imaging to demonstrate that changes in T cell metabolism and activation status are correlated. Using MPM imaging we successfully demonstrated T cell activation and T cell mediated cytotoxicity in response to ICI in LTFs and tumor biopsies. Methods Tumors were cut into LTFs, sorted, and cultured using the Cybrid platform. LTF structure and metabolic status were assessed using intrinsically fluorescent NAD(P)H and FAD. Anti-CD8 nanobodies and cleaved caspase 3/7 dye were used to characterize T cell cytotoxicity. Multi-channel fluorescence intensity and lifetime were obtained over 48 hours using MPM. Results Murine CT26 LTFs generated with the Cybrid platform were treated with ICI and cytotoxicity was assessed in the intact LTFs by monitoring caspase 3/7 activity using MPM over 48 hours. We found that ICI treatment resulted in a significant increase in caspase 3/7 activity compared to control treated LTFs. By blocking the interaction of T cells with tumor cells through antibody blockade, we demonstrated that the cytotoxicity observed was T cell mediated. As additional confirmation, we measured changes in cytotoxicity in the ICI resistant LLC1 tumor model. As expected, we did not observe an increase in cytotoxicity in LLC1 LTFs treated with ICI. MPM allows for the tracking of labeled T cells and characterization of their metabolism as a means of assessing changes in their activation state. We used a CD8 nanobody to label T cells in CT26 LTFs and then characterized the shift in metabolism following ICI treatment. Finally, we applied the Cybrid platform to human biopsies treated with ICI and characterized the cytotoxicity and shifts in T cell metabolism in living tissue. These data show that the Cybrid platform can measure changes in T cell metabolism and T cell cytotoxicity in response to ICI in 3D living tissue. Conclusions The methods presented herein will advance the field of cancer diagnostics by progressing from fixed tissue imaging and genetic characterization to the assessment of clinically relevant ICI-treated biopsies. Understanding the response of biopsies to immunotherapies will allow clinicians to make more informed treatment decisions and improve the lives of those with cancer. Citation Format: Jonathan Ouellette, Janey Degnan, Anna Kellner, Evan Flietner, Lindsay Doebert, Zachary Swider, Eric Wait, Victoria Pope, Laura Hrycyniak, Sean Caenepeel, Kevin Eliceiri, T S. Ramasubramanian, Michael J. Korrer. Assessing cytotoxic T cell responses to immune checkpoint inhibitors in murine and human tumor samples using metabolic imaging [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6444.

Abstract 4074: Discovery of WTX-518, an IL-18 pro-drug that is conditionally activated within the tumor microenvironment and induces regressions in mouse tumor models

Abstract Systemic administration of proinflammatory cytokines is a promising approach to treat cancer. IL-18 has been shown to promote activation of both innate and adaptive anti-tumor responses in pre-clinical models. Specifically, IL-18 has been shown to impact macrophage suppressive function as well as drive CD4+ T cells towards a TH1 phenotype. However, IL-18 therapies have been hampered by a lack of efficacy due to the suppressive activity of IL-18 binding protein (IL-18BP), which binds to IL-18 and prevents its interaction with its receptor. Several groups have taken the approach of modifying IL-18 to render it resistant to IL-18BP as a potential strategy to enhance anti-tumor activity. To explore the therapeutic benefit of delivering a conditionally-activated IL-18 to the tumor microenvironment, we have developed inducible polypeptides (INDUKINE™ molecules) consisting of mouse IL-18 or IL-18BP resistant IL-18 (BPR IL-18) tethered via protease-sensitive linkers to a high affinity antibody blockade domain, and a half-life extension (HLE) domain which improves exposure in the tumor. IL-18 INDUKINE™ molecules are inactive until reaching the tumor microenvironment, where the linkers are cleaved by intra-tumoral proteases, releasing active IL-18. Intraperitoneal (i.p.) administration of an IL-18BP resistant IL-18 (BPR IL-18) INDUKINE™ molecule led to complete tumor regression in the MC38 tumor model. In contrast, equimolar doses of wild-type IL-18 INDUKINE™ protein were not as efficacious. Moreover, BPR IL-18 INDUKINE treatment led to increased activation and frequencies of NK cells and tumor specific CD8 T cells in MC38 tumors. WTX-518 is a novel INDUKINE™ molecule that is designed to selectively deliver active human BPR IL-18 to the tumor microenvironment. WTX-518 is inducible in vitro, either when tested using a reporter assay or primary immune cells. Importantly, the active BPR IL-18 payload is resistant to IL-18BP in reporter or primary immune cell assays. WTX-518 is also selectively inducible, as incubation ex vivo with various primary human tumors led to the release of active BPR IL-18, while WTX-518 was stable in human serum and after exposure to primary cells from healthy tissues. Pharmacological and efficacy data support continued preclinical development of this innovative and differentiated engineered IL-18 therapy. Citation Format: Kristin R. Morris, Heather Brodkin, Kyriakos Economides, Daniel J. Hicklin, Julie LePrevost, Celesztina Nagy-Domonkos, Christopher Nirschl, Andres Salmeron, Cynthia Seidel-Dugan, Cierra Spencer, Zoe Steuert, William M. Winston. Discovery of WTX-518, an IL-18 pro-drug that is conditionally activated within the tumor microenvironment and induces regressions in mouse tumor models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4074.

Abstract 7539: First-in-class anti-PVR mAb NTX1088 advancing through Phase I: Safe and potent in restoring DNAM1 expression to enhance antitumor immunity

Abstract NTX1088, a first-in-class anti-PVR (CD155) mAb, is currently evaluated in a Phase 1, open-label, multi-center study (NCT05378425). The trial initiated at MD Anderson Cancer Center, and was expanded into additional sites, including City of Hope, Ochsner Health, Sheba Medical Center and Hadassah Medical Center. Study objectives are safety, dose-finding, and efficacy with focus on pharmacokinetics, pharmacodynamics, and biomarker discovery. NTX1088 is investigated as a single agent and in combination with the anti-PD1 mAb, pembrolizumab (Keytruda) in patients with advanced solid malignancies. Ongoing dose escalation demonstrates a safe profile across ascending dose levels. NTX1088 is a high affinity humanized IgG4-S228P mAb that binds PVR and blocks all known interacting receptors at a single nM EC50. PVR, is a highly upregulated membrane protein on numerous tumor cells. PVR expression has been associated with worse patient outcome, due to its central role in immune suppression. PVR’s impact is mediated through interaction with the key stimulatory receptor, DNAM1 (CD226), on T and NK cells, leading to internalization and degradation of DNAM1. PVR also interacts with the inhibitory immune checkpoint receptors, TIGIT, CD96 and KIR2DL5A. Blocking PVR by NTX1088 has multiple immune-stimulating roles, through restoration of DNAM1 immune activation function, while simultaneously neutralizing TIGIT, CD96 and KIR2DL5A inhibitory signals in immune cells. Importantly, DNAM1 downmodulation was recently identified as a key resistance mechanism to approved immune checkpoint inhibitors, and its restoration by NTX1088 is a novel MoA, not demonstrated previously by other therapies.In vitro, as a monotherapy, NTX1088 significantly increased immune cell activation, superior to TIGIT, CD112R, and PD1 antibody blockade, leading to a greater immune-mediated tumor cell killing, IFNγ secretion, and CD137 induction. Importantly, only NTX1088 was able to restore DNAM1 to the surface of immune cells. Synergy was obtained when NTX1088 was combined with PD1 blockers, or with the anti-CD112R mAb, NTX2R13.Syngeneic models of PVRK.O, demonstrated a complete immune-mediated tumor regression. Numerous humanized murine xenograft models were investigated whereby NTX1088 exhibited robust tumor growth inhibition as a standalone and in combination with PD1 blockade.In conclusion, PVR blockade by NTX1088 has a remarkable pre-clinical efficacy, suggesting a potential clinical breakthrough, based on its ability to simultaneously overcome multiple tumor escape mechanisms. First-in-human (FIH) trial is currently ongoing and biomarker analysis is showing initial mechanistic proof of concept for NTX1088 mode of action, including the restoration of DNAM1 surface expression on patients’ immune cells. This is the first case of surface DNAM1 elevation in clinical settings. Citation Format: Anas Atieh, Akram Obeidat, Alon Vitenshtein, Guy Cinamon, Keren Paz, Tihana Roviš, Paola Brilc, Ofer Mandelboim, Stipan Jonjic, Pini Tsukerman. First-in-class anti-PVR mAb NTX1088 advancing through Phase I: Safe and potent in restoring DNAM1 expression to enhance antitumor immunity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7539.

Abstract 3716: Enhancing anti-tumor responses in triple-negative breast cancer by combining SIRPα inhibition with immunogenic chemotherapy or antibody-drug conjugates

Abstract Background: Triple-negative breast cancer (TNBC) is a subtype of breast cancer defined by the absence of hormone receptors and HER2 receptor on tumor cells. Because of a lack of targetable receptors and poor response to PD1/PDL1 immunotherapy, TNBC has limited systemic treatment options. In previous work using a genomic screen (Shuptrine et al., 2017), we identified CD47 as one of the leading factors that contributes to TNBC immune evasion. The CD47-SIRPα axis is an innate immune checkpoint that primarily regulates myeloid cells. In the context of cancer, tumor cells upregulate CD47 to engage SIRPα inhibitory signaling to block phagocytosis. While CD47 or SIRPα blockade alone show limited antitumor effect, therapies that combine blockade of this axis with other treatment agents, such as tumor-antigen specific antibodies, show superior tumor inhibition. Thus, we hypothesize that the addition of SIRPα inhibition to existing TNBC treatments (chemotherapy and Trop2-antibody drug conjugates (ADC)) will improve their treatment efficacy. Methods: To ascertain the impact of SIRPα inhibition combined with chemotherapy and Trop2-ADC, we utilized and validated a novel SIRPα KO mouse, along with SIRPα mAbs, in our previously utilized models of Triple-Negative Breast Cancer (TNBC) (Crosby et al., 2018). Using both in vitro and in vivo tumor models, we tested the therapeutic impact of SIRPα inhibition/blockade combined with different immunogenic chemotherapies (doxorubicin/cyclophosphamide) and Sacituzumab govitecan (SG) in TNBC. Results: After validating the loss of SIRPα in KO mice, we found that E0771 TNBC cells had comparable growth rates in WT and SIRPα KO mice. Similarly, we did not observe different anti-tumor responses to Doxorubicin between WT and SIRPα-KO mice. However, we observed more profound suppression of E0771 tumors after cyclophosphamide treatment in SIRPα KO mice than in WT mice. To evaluate the efficacy of SG in inducing antibody-dependent cellular phagocytosis (ADCP), we co-cultured SIRPα KO and WT mouse macrophages with a syngeneic mouse TNBC model (MM3MG-Trop2-WT). We found that SG promotes ADCP in WT macrophages, and SIRPα loss further increased this ADCP, suggesting the potential importance of antibody-mediated phagocytosis as a mechanism of action for SG. In vivo, we implanted human TNBC cells (MDA-MB-468) in mice and treated them with SG with and without SIRPα antibody blockade. These studies demonstrated an anti-tumor effect from SG that was potentially enhanced by SIRPα blockade, suggesting the clinical potential of this combination in TNBC. Conclusion: Our study demonstrates that the addition of SIRPα inhibition to chemotherapy or SG may promote tumor phagocytosis and stimulate stronger antitumor immunity in TNBC. These results support further investigation of SIRPα-targeting combination therapies for TNBC. Citation Format: Xingru Ma, Li-Chung Tsao, Tao Wang, Cong-Xiao Liu, Melissa Gajda, Xiao Yang, Gangjun Lei, Junping Wei, Zachary Hartman. Enhancing anti-tumor responses in triple-negative breast cancer by combining SIRPα inhibition with immunogenic chemotherapy or antibody-drug conjugates [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3716.

Abstract 6584: Aberrant TRIM7 expression potentiates RACO-1 mediated proliferation and dysregulated interferon responsiveness in the setting of anti-PD-1 acquired resistance in cancer

Abstract While checkpoint inhibitor treatment has extended the survival of many cancer patients, most initial responders will later develop disease progression through a variety of poorly understood acquired resistance mechanisms (CPI-AR). One such recently described mechanism involves the transcriptional hyperactivation of genes associated with interferon (IFN) signaling, JAK/STAT, and antigen processing/presentation pathways. Aberrant IFN regulation in the setting of AR suggests that tumor cell intrinsic mechanisms have conferred a growth advantage despite the presence of immune-mediated pressure unleashed by PD-1/L1 antibody blockade. Analysis of transcripts progressively upregulated during acquisition of AR in vivo and transcripts upregulated by IFN exposure of isolated AR cell lines in vitro identified the E3 ubiquitin ligase TRIM7 as a candidate mediator of the AR phenotype. A specific pocket on the PRY/SPRY domain of TRIM7 has been shown to bind viral peptides, resulting in ubiquitination and degradation as a mechanism to mitigate viral propagation. Here we describe the evaluation of small molecule inhibitors (SMI) designed to the TRIM7 PRY/SPRY viral-pocket domain, where binding specificity was confirmed using mass spec analysis. These SMI competitively inhibited TRIM7 mediated stabilization of RACO-1, resulting in decreased cancer cell proliferation which was associated with altered c-Jun/AP-1 transcription. TRIM7 SMI also disrupted STING and MAVS ubiquitination and restored IFN responsiveness and sensitivity to PD-1 inhibitor treatment. Finally, given the position of TRIM7 downstream of growth factor receptor and kras signaling, combination of TRIM7 inhibitors with kras, braf, and/or MEK inhibitors was shown to additively suppress proliferation of tumor cells with kras mutations. These results provide evidence that upregulation of TRIM7 mediates both a pro-proliferative and IFN resistant phenotype in the setting of CPI-AR, and that inhibition of TRIM7 with small molecule inhibitors may prevent or reverse AR to PD-1/L1 blockade. Citation Format: Thuy-Ai Tran Nguyen, Marc Morra, Kevin Li, Ulhas Bhatt, Joseph Mwangi, Yisel Rivera-Molina, Nathan Oien, Julio Medina, Taylor H. Schreiber, George Fromm. Aberrant TRIM7 expression potentiates RACO-1 mediated proliferation and dysregulated interferon responsiveness in the setting of anti-PD-1 acquired resistance in cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6584.

Abstract 7174: Pharmacokinetics and immunogenicity of anti-PD-1 antibody in humanized FcRn mouse models compared to immunocompetent mouse models

Abstract Introduction: The development and use of therapeutic antibodies in cancer therapy has increased significantly in recent years, led by the success of approved immune checkpoint blockade antibodies targeting PD-1 and PD-L1 axis. However, obtaining more clinically relevant pharmacokinetics (PK), safety and efficacy data for antibodies is still challenging in preclinical phase. Humanized FcRn (hFcRn) transgenic mouse model has a more faithful catabolism compared to WT mice, providing more accurate and predictable PK data of innovative antibody-based therapeutics at discovery stage[1]. In this study, we sought to investigate pharmacokinetics and immunogenicity characteristics of anti-PD-1 antibody in hFcRn transgenic mice and provide guidance for its differentiation of prediction value for drug PK and safety by comparing to WT mice. Methods: Non-tumor bearing hFcRn mice and wild type C57BL/6 mice were divided into 2 groups, 5 mice were enrolled into each group. Mice were administered anti-PD-1(Nivolumab) at 10 mg/kg single dose after grouping by intravenous (IV) injection. Blood samples at 12 timepoints (15min, 6h, 1, 2, 4, 7, 10, 14, 21, 28, 35, 42 days) post-dosing were collected for PK and Anti-Drug Antibody (ADA) analysis by MSD and ELISA. Results: Nivolumab clearance in hFcRn mice followed a typical linear profile with rapid distribution phase and slow elimination phase (t1/2 = 350 to 400 h). While the PK profile in C57BL/6 mice displayed non-linear clearance and very short elimination phase (t1/2 = 45 to 50 h). This data demonstrated that hFcRn mice have better correlated half-life with human (Nivolumab single dose by IV with 10mg/kg, t1/2 = 595 h) [2]. ADA analysis revealed that it was produced starting from Day 10 in wild type C57BL/6 mice and the frequency of ADA induced by Nivolumab in wild type mice (2/5) was higher than hFcRn mice (0/5). The variation of Nivolumab level was correlated with ADA production in wild type mice. This suggested hFcRn shows lower immunogenicity than wild type mice for human IgG drug and can potentially improve negative effect of ADA interference on PK evaluation. Conclusion: The result of this study demonstrated that the PK data in hFcRn mouse model was more predictive of human PK profile compared to wild type C57BL/6 mice. This advances innovation in antibody-based therapeutics and translational applications, with improved PK, safety and efficacy evaluation for preclinical human IgG drug development in cancer therapy.

Abstract 3595: A retrospective analysis of the clinical characteristics of metastastic solid cancer patients with cytokine-induced killer cells combined immune checkpoint inhibitor immunotherapy

Abstract Background: Cytokine-induced killer cells (CIKs), obtained through ex vivo expasion from peripheral blood mononuclear cells, are phenotypically and functionally shared with both T and NK cells. Within the T cell group, it can be classified into a group that simultaneously expresses CD3 and CD56 molecules (range: 30% to 70%) and a group representing CD3+ CD56- phenotype (range: 20% to 60%). It also contains a small population (< 30%) of CD3 CD56+ NK cells. They can exhibit potent MHC-unrestricted cytotoxicity for both hematologic and solid tumors, but they are not harmful in hematopoietic precursors and normal tissues. Anti-programmed death-1 (PD-1) antibodies reinvigorate T cell-mediated antitumor immunity. PD-1 blockade antibody might significantly increase the cytotoxic potency of CIK cells via increasing proliferative capacity and IFN-r secretion. This retrospective study is the first to combine CIK cells with PD-1/PD-L1/CTLA-4 blockade(Immune checkpoint inhibitors, ICIs) in patients with metastatic solid cancers. Methods: We analyzed 225 heavily treated metastastic solid cancer patients receiving CIK cell (Immunecell-LC, GC cell inc provide.) and with ICIs. Blood Sampling for CIK cells production was performed after 3 days after ICIs administration. Patients received a single intravenous infusion of activated autologous CIK cells every 2 weeks. ICIs was administered according to the protocol of each drug regardless of the CIK cells administration date. The primary end points were safety and adverse event (AE) profiles. Objective responses, overall survival (OS), progression-free survival (PFS), and diseae control rate were secondary end points. Results: Treatment-related AEs occurred in 154/225 patients. Grade 3 or 4 toxicities, including fever and chills, were observed in 28 patients. All treatment-related AEs were tolerable and no death due to autoimmune disease. When administration ICIs, CIK cells exhibited excellent antitumor properties and increased IFN-γ secretion. Objective responses (complete or partial responses) were observed in 67 of the 225 patients. One patients with hepatocellular carcionma had complete response. In most patients who showed an objective response, the effectiveness was maintained for more than 6 months. The overall disease control rate in the patients was 58.9%. At the time of this report, the median OS and PFS were 18.6 and 7.1 months in hepatocellular carcinoma patients and were 13.1 and 6.5 months in triple negative breast cancer patients, respectively. Conclusion: Treatment with activated autologous CIK cells and ICIs was safe and exerted encouraging antitumor activity in metastastic solid cancers. Phase 2 clinical studies for each tumor type will be conducted. Keywords: Cytokine-induced killer cells, Immune check inhibitors, Safety, Objective response Citation Format: Jonggwon Choi, Jong Yeup Kim, Dong Won Yang, Gun He Nam. A retrospective analysis of the clinical characteristics of metastastic solid cancer patients with cytokine-induced killer cells combined immune checkpoint inhibitor immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3595.

Anti-CD99 Antibody Therapy Triggers Macrophage-Dependent Ewing Cell Death In Vitro and Myeloid Cell Recruitment In Vivo.

Ewing sarcoma is a rare tumor of the bone or soft tissues characterized by diffuse membranous staining for CD99. As this tumor remains incurable in the metastatic, relapsed, and refractory settings, we explored the downstream immune implications of targeting CD99. We discovered a human anti-CD99 antibody (NOA2) by phagemid panning and investigated NOA2 immune cell-mediated cytotoxicity in vitro and in vivo focusing on the myeloid cell compartment, given that M2 macrophages are present in human tumors and associated with a poor prognosis. NOA2 is capable of inducing immune effector cell-mediated Ewing death in vitro via engagement of macrophages. Mice with metastatic Ewing tumors, treated with NOA2, experience tumor growth arrest and an associated increase in intratumoral macrophages. Further, incubation of macrophages and Ewing cells with NOA2, in conjunction with anti-PILRα antibody blockade in vitro, results in the reactivation of previously dormant macrophages possibly due to interrupted binding of Ewing CD99 to macrophage PILRα. These studies are the first to demonstrate the role of human immune effector cells in anti-CD99-mediated Ewing tumor death. We propose that the engagement of CD99 by NOA2 results in the recruitment of intratumoral macrophages. In addition, interruption of the CD99:PILRα checkpoint axis may be a relevant therapeutic approach to activate tumor-associated macrophages.

HBV DNA polymerase upregulates the transcription of PD-L1 and suppresses T cell activity in hepatocellular carcinoma

BackgroundIn HBV-associated HCC, T cells often exhibit a state of functional exhaustion, which prevents the immune response from rejecting the tumor and allows HCC to progress. Moreover, polymerase-specific T cells exhibit more severe T-cell exhaustion compared to core-specific T cells. However, whether HBV DNA polymerase drives HBV-specific CD8+ T cell exhaustion in HBV-related HCC remains unclear.MethodsWe constructed a Huh7 cell line stably expressing HA-HBV-DNA-Pol and applied co-culture systems to clarify its effect on immune cell function. We also examined how HBV-DNA-Pol modulated PD-L1 expression in HCC cells. In addition, HBV-DNA-Pol transgenic mice were used to elucidate the underlying mechanism of HBV-DNA-Pol/PD-L1 axis-induced T cell exhaustion.ResultsBiochemical analysis showed that Huh7 cells overexpressing HBV-DNA-Pol inhibited the proliferation, activation, and cytokine secretion of Jurkat cells and that this effect was dependent on their direct contact. A similar inhibitory effect was observed in an HCC mouse model. PD-L1 was brought to our attention during screening. Our results showed that the overexpression of HBV-DNA-Pol upregulated PD-L1 mRNA and protein expression. PD-L1 antibody blockade reversed the inhibitory effect of Huh7 cells overexpressing HBV-DNA-Pol on Jurkat cells. Mechanistically, HBV-DNA-Pol interacts with PARP1, thereby inhibiting the nuclear translocation of PARP1 and further upregulating PD-L1 expression.ConclusionsOur findings suggest that HBV-DNA-Pol can act as a regulator of PD-L1 in HCC, thereby directing anti-cancer immune evasion, which further provides a new idea for the clinical treatment of liver cancer.

Engineered lactococcus lactis intrapleural therapy promotes regression of malignant pleural effusion by enhancing antitumor immunity

Intrapleural immunotherapies have emerged as a prominent field in treating malignant pleural effusion (MPE). Among these, bacteria-based intrapleural therapy has exerted an anti-MPE effect by immuno-stimulating or cytotoxic properties. We previously engineered a probiotic Lactococcus lactis (FOLactis) expressing a fusion protein of Fms-like tyrosine kinase 3 and co-stimulator OX40 ligands. FOLactis activates tumor antigen-specific immune responses and displays systemic antitumor efficacy via intratumoral delivery. However, no available lesions exist in the pleural cavity of patients with MPE for intratumoral administration. Therefore, we further optimize FOLactis to treat MPE through intrapleural injection. Intrapleural administration of FOLactis (I-Pl FOLactis) not only distinctly suppresses MPE and pleural tumor nodules, but also significantly extends noticeable survival in MPE-bearing murine models. The proportion of CD103+ dendritic cells (DCs) in tumor-draining lymph nodes increases three-fold in FOLactis group, compared to the wild-type bacteria group. The enhanced DCs recruitment promotes the infiltration of effector memory T and CD8+ T cells, as well as the activation of NK cells and the polarization of macrophages to M1. Programmed death 1 blockade antibody combination further enhances the antitumor efficacy of I-Pl FOLactis. In summary, we first develop an innovative intrapleural strategy based on FOLactis, exhibiting remarkable efficacy and favorable biosafety profiles. These findings suggest prospective clinical translation of engineered probiotics for managing MPE through direct administration into the pleural cavity.

A redox-responsive prodrug for tumor-targeted glutamine restriction

Modulating the metabolism of cancer cells, immune cells, or both is a promising strategy to potentiate cancer immunotherapy in the nutrient-competitive tumor microenvironment. Glutamine has emerged as an ideal target as cancer cells highly rely on glutamine for replenishing the tricarboxylic acid cycle in the process of aerobic glycolysis. However, non-specific glutamine restriction may induce adverse effects in unconcerned tissues and therefore glutamine inhibitors have achieved limited success in the clinic so far. Here we report the synthesis and evaluation of a redox-responsive prodrug of 6-Diazo-5-oxo-L-norleucine (redox-DON) for tumor-targeted glutamine inhibition. When applied to treat mice bearing subcutaneous CT26 mouse colon carcinoma, redox-DON exhibited equivalent antitumor efficacy but a greatly improved safety profile, particularly, in spleen and gastrointestinal tract, as compared to the state-of-the-art DON prodrug, JHU083. Furthermore, redox-DON synergized with checkpoint blockade antibodies leading to durable cures in tumor-bearing mice. Our results suggest that redox-DON is a safe and effective therapeutic for tumor-targeted glutamine inhibition showing promise for enhanced metabolic modulatory immunotherapy. The approach of reversible chemical modification may be generalized to other metabolic modulatory drugs that suffer from overt toxicity.

Enhanced potency of immunotherapy against B-cell precursor acute lymphoblastic leukemia by combination of an Fc-engineered CD19 antibody and CD47 blockade.

CD19-directed immunotherapy has become a cornerstone in the therapy of B-cell precursor acute lymphoblastic leukemia (BCP-ALL). CD19-directed cellular and antibody-based therapeutics have entered therapy of primary and relapsed disease and contributed to improved outcomes in relapsed disease and lower therapy toxicity. However, efficacy remains limited in many cases due to a lack of therapy response, short remission phases, or antigen escape. Here, BCP-ALL cell lines, patient-derived xenograft (PDX) samples, human macrophages, and an in vivo transplantation model in NOD.Cg-PrkdcscidIl2rgtm1Wjl/SzJ (NSG) mice were used to examine the therapeutic potency of a CD19 antibody Fc-engineered for improved effector cell recruitment (CD19-DE) and antibody-dependent cellular phagocytosis (ADCP), in combination with a novel modified CD47 antibody (Hu5F9-IgG2σ). For the in vivo model, only samples refractory to CD19-DE monotherapy were chosen. Hu5F9-IgG2σ enhanced ADCP by CD19-DE in various BCP-ALL cell line models with varying CD19 surface expression and cytogenetic backgrounds, two of which contained the KMT2A-AFF1 fusion. Also, the antibody combination was efficient in inducing ADCP by human macrophages in pediatric PDX samples with and adult samples with and without KMT2A-rearrangement in vitro. In a randomized phase 2-like PDX trial using seven KMT2A-rearranged BCP-ALL samples in NSG mice, the CD19/CD47 antibody combination proved highly efficient. Our findings support that the efficacy of Fc-engineered CD19 antibodies may be substantially enhanced by a combination with CD47 blockade. This suggests that the combination may be a promising therapy option for BCP-ALL, especially in relapsed patients and/or patients refractory to CD19-directed therapy.