Efficacy Of Immune Checkpoint Blockade Research Articles

Redox-responsive polymer micelles co-encapsulating immune checkpoint inhibitors and chemotherapeutic agents for glioblastoma therapy

Immunotherapy with immune checkpoint blockade (ICB) for glioblastoma (GBM) is promising but its clinical efficacy is seriously challenged by the blood-tumor barrier (BTB) and immunosuppressive tumor microenvironment. Here, anti-programmed death-ligand 1 antibodies (aPD-L1) are loaded into a redox-responsive micelle and the ICB efficacy is further amplified by paclitaxel (PTX)-induced immunogenic cell death (ICD) via a co-encapsulation approach for the reinvigoration of local anti-GBM immune responses. Consequently, the micelles cross the BTB and are retained in the reductive tumor microenvironment without altering the bioactivity of aPD-L1. The ICB efficacy is enhanced by the aPD-L1 and PTX combination with suppression of primary and recurrent GBM, accumulation of cytotoxic T lymphocytes, and induction of long-lasting immunological memory in the orthotopic GBM-bearing mice. The co-encapsulation approach facilitating efficient antibody delivery and combining with chemotherapeutic agent-induced ICD demonstrate that the chemo-immunotherapy might reprogram local immunity to empower immunotherapy against GBM.

POLQ identifies a better response subset to immunotherapy in muscle-invasive bladder cancer with high PD-L1.

Though programmed cell death-ligand 1 (PD-L1) has been used in predicting the efficacy of immune checkpoint blockade (ICB), it is insufficient as a single biomarker. As a key effector of an intrinsically mutagenic microhomology-mediated end joining (MMEJ) pathway, DNA polymerase theta (POLQ) was overexpressed in various malignancies, whose expression might have an influence on genomic stability, therefore altering the sensitivity to chemotherapy and immunotherapy. A total of 1304 patients with muscle-invasive bladder cancer (MIBC) from six independent cohorts were included in this study. The Zhongshan Hospital (ZSHS) cohort (n = 134), The Cancer Genome Atlas (TCGA) cohort (n = 391), and the Neo-cohort (n = 148) were included for the investigation of chemotherapeutic response. The IMvigor210 cohort (n = 234) and the UNC-108 cohort (n = 89) were used for the assessment of immunotherapeutic response. In addition, the relationship between POLQ and the immune microenvironment was assessed, and GSE32894 (n = 308) was used only for the evaluation of the immune microenvironment. We identified POLQhigh PD-L1high patients could benefit more from immunotherapy and platinum-based chemotherapy. Further analysis revealed that high POLQ expression was linked to chromosome instability and higher tumor mutational burden (TMB), which might elicit the production of neoantigens. Further, high POLQ expression was associated with an active tumor immune microenvironment with abundant infiltration of immune effector cells and molecules. The study demonstrated that high POLQ expression was correlated with chromosome instability and antitumor immune microenvironment in MIBC, and the combination of POLQ and PD-L1 could be used as a superior companion biomarker for predicting the efficacy of immunotherapy.

A Lactate-Depleting metal organic framework-based nanocatalyst reinforces intratumoral T cell response to boost anti-PD1 immunotherapy

Infiltration and activation of intratumoral T lymphocytes are critical for immune checkpoint blockade (ICB) therapy. Unfortunately, the low tumor immunogenicity and immunosuppressive tumor microenvironment (TME) induced by tumor metabolic reprogramming cooperatively hinder the ICB efficacy. Herein, we engineered a lactate-depleting MOF-based catalytic nanoplatform (LOX@ZIF-8@MPN), encapsulating lactate oxidase (LOX) within zeolitic imidazolate framework-8 (ZIF-8) coupled with a coating of metal polyphenol network (MPN) to reinforce T cell response based on a “two birds with one stone” strategy. LOX could catalyze the degradation of the immunosuppressive lactate to promote vascular normalization, facilitating T cell infiltration. On the other hand, hydrogen peroxide (H2O2) produced during lactate depletion can be transformed into anti-tumor hydroxyl radical (•OH) by the autocatalytic MPN-based Fenton nanosystem to trigger immunogenic cell death (ICD), which largely improved the tumor immunogenicity. The combination of ICD and vascular normalization presents a better synergistic immunopotentiation with anti-PD1, inducing robust anti-tumor immunity in primary tumors and recurrent malignancies. Collectively, our results demonstrate that the concurrent depletion of lactate to reverse the immunosuppressive TME and utilization of the by-product from lactate degradation via cascade catalysis promotes T cell response and thus improves the effectiveness of ICB therapy.

Readily available drugs and other interventions to potentially improve the efficacy of immune checkpoint blockade in cancer.

To improve the efficacy of immune checkpoint inhibitors (ICIs) for cancer treatment, various strategies, including combination therapies with repurposed drugs, are being explored. Several readily available interventions with potential to enhance programmed death 1 (PD-1) blockade have been identified. However, these interventions often remain overlooked due to the lack of financial incentives for their development, making them financial orphans. This review summarizes current knowledge regarding off-label drugs, supplements, and other readily available interventions that could improve the efficacy of PD-1 blockade. The summary of each intervention includes the proposed mechanism of action for combination with checkpoint inhibitors and data from animal and human studies. Additionally, we include summaries of common interventions to be avoided by patients on PD-1 blockade. Finally, we present approaches for conducting further studies in patients, with the aim of expediting the clinical development of these interventions. We strive to increase awareness of readily available combination therapies that may advance cancer immunotherapy and help patients today.

Multiomics characterization of pyroptosis in the tumor microenvironment and therapeutic relevance in metastatic melanoma

BackgroundPyroptosis, mediated by gasdermins with the release of multiple inflammatory cytokines, has emerged as playing an important role in targeted therapy and immunotherapy due to its effectiveness at inhibiting tumor growth. Melanoma is one of the most commonly used models for immunotherapy development, though an inadequate immune response can occur. Moreover, the development of pyroptosis-related therapy and combinations with other therapeutic strategies is limited due to insufficient understanding of the role of pyroptosis in the context of different tumor immune microenvironments (TMEs).MethodsHere, we present a computational model (pyroptosis-related gene score, PScore) to assess the pyroptosis status. We applied PScore to 1388 melanoma samples in our in-house cohort and eight other publicly available independent cohorts and then calculated its prognostic power of and potential as a predictive marker of immunotherapy efficacy. Furthermore, we performed association analysis for PScore and the characteristics of the TME by using bulk, single-cell, and spatial transcriptomics and assessed the association of PScore with mutation status, which contributes to targeted therapy.ResultsPyroptosis-related genes (PRGs) showed distinct expression patterns and prognostic predictive ability in melanoma. Most PRGs were associated with better survival in metastatic melanoma. Our PScore model based on genes associated with prognosis exhibits robust performance in survival prediction in multiple metastatic melanoma cohorts. We also found PScore to be associated with BRAF mutation and correlate positively with multiple molecular signatures, such as KRAS signaling and the IFN gamma response pathway. Based on our data, melanoma with an immune-enriched TME had a higher PScore than melanoma with an immune-depleted or fibrotic TME. Additionally, monocytes had the highest PScore and malignant cells and fibroblasts the lowest PScore based on single-cell and spatial transcriptome analyses. Finally, a higher PScore was associated with better therapeutic efficacy of immune checkpoint blockade, suggesting the potential of pyroptosis to serve as a marker of immunotherapy response.ConclusionsCollectively, our findings indicate that pyroptosis is a prognostic factor and is associated with the immune response in metastatic melanoma, as based on multiomics data. Our results provide a theoretical basis for drug combination and reveal potential immunotherapy response markers.

Role of stromal PD-L1 expression in colorectal liver metastasis

Background and AimThe outcomes of immune checkpoint blockade for colorectal cancer (CRC) treatment are unsatisfactory. Furthermore, the efficacy of immune checkpoint blockade for liver metastasis of various cancer is poor. Here, we investigated the relationship between stromal programmed death-ligand 1 (PD-L1) expression and the prognosis of patients with colorectal cancer liver metastasis (CRLM).MethodsThe present study enrolled 84 CRLM patients who underwent surgery (R0) for CRC. Immunohistochemistry was performed to analyze stromal PD-L1 expression in CRLM.ResultsStromal PD-L1 was expressed in 52.3% of CRLM samples, which was associated with fewer not optimally resectable metastases (p = 0.04). Stromal PD-L1 also tended to associate with a lower tumor grade (p = 0.08). Stromal PD-L1-positive patients had longer overall survival (p = 0.003). Multivariate analysis identified stromal PD-L1 expression (p = 0.008) and poorer differentiation (p < 0.001) as independent prognostic indicators. Furthermore, stromal PD-L1 expression was correlated to a high number of tumor-infiltrating lymphocytes (TILs). Stromal PD-L1– and low TIL groups had shorter OS than stromal PD-L1 + and high TIL groups (46.6% vs. 81.8%, p = 0.05) Stromal PD-L1-positive patients had longer disease-free survival (DFS) (p = 0.03) and time to surgical failure (p = 0.001). Interestingly, stromal PD-L1 expression was positively related to the desmoplastic subtype (p = 0.0002) and inversely related to the replacement subtype of the histological growth pattern (p = 0.008).ConclusionsStromal PD-L1 expression may be a significant prognostic marker for CRLM.

Tumor-associated neutrophils suppress CD8+ T cell immunity in urothelial bladder carcinoma through the COX-2/PGE2/IDO1 Axis.

Many urothelial bladder carcinoma (UBC) patients don't respond to immune checkpoint blockade (ICB) therapy, possibly due to tumor-associated neutrophils (TANs) suppressing lymphocyte immune response. We conducted a meta-analysis on the predictive value of neutrophil-lymphocyte ratio (NLR) in ICB response and investigated TANs' role in UBC. We used RNA-sequencing, HALO spatial analysis, single-cell RNA-sequencing, and flow cytometry to study the impacts of TANs and prostaglandin E2 (PGE2) on IDO1expression. Animal experiments evaluated celecoxib's efficacy in targeting PGE2 synthesis. Our analysis showed that higher TAN infiltration predicted worse outcomes in UBC patients receiving ICB therapy. Our research revealed that TANs promote IDO1 expression in cancer cells, resulting in immunosuppression. We also found that PGE2 synthesized by COX-2 in neutrophils played a key role in upregulating IDO1 in cancer cells. Animal experiments showed that targeting PGE2 synthesis in neutrophils with celecoxib enhanced the efficacy of ICB treatment. TAN-secreted PGE2 upregulates IDO1, dampening T cell function in UBC. Celecoxib targeting of PGE2 synthesis represents a promising approach to enhance ICB efficacy in UBC.

Plasma EBV quantification is associated with the efficacy of immune checkpoint blockade and disease monitoring in patients with primary pulmonary lymphoepithelioma-like carcinoma.

Primary pulmonary lymphoepithelioma-like carcinoma (PLELC) is a subtype of lung carcinoma associated with the Epstein-Barr virus (EBV). The clinical predictive biomarkers of immune checkpoint blockade (ICB) in PLELC require further investigation. We prospectively analysed EBV levels in the blood and immune tumor biomarkers of 31 patients with ICB-treated PLELC. Viral EBNA-1 and BamHI-W DNA fragments in the plasma were quantified in parallel using quantitative polymerase chain reaction. Progression-free survival (PFS) was significantly longer in EBNA-1 high or BamHI-W high groups. A longer PFS was also observed in patients with both high plasma EBNA-1 or BamHI-W and PD-L1 ≥ 1%. Intriguingly, the tumor mutational burden was inversely correlated with EBNA-1 and BamHI-W. Plasma EBV load was negatively associated with intratumoral CD8+ immune cell infiltration. Dynamic changes in plasma EBV DNA level were in accordance with the changes in tumor volume. An increase in EBV DNA levels during treatment indicated molecular progression that preceded the imaging progression by several months. Plasma EBV DNA could be a useful and easy-to-use biomarker for predicting the clinical activity of ICB in PLELC and could serve to monitor disease progression earlier than computed tomography imaging.

TUBA1C orchestrates the immunosuppressive tumor microenvironment and resistance to immune checkpoint blockade in clear cell renal cell carcinoma.

Clear cell renal cell carcinoma (ccRCC) poses substantial treatment challenges, especially in advanced stages where the efficacy of immune checkpoint blockade (ICB) therapy varies significantly. Elevated expression of the oncogene TUBA1C has been correlated with poor prognosis in various cancers, however, its role in ccRCC is unclear, especially concerning ICB resistance. Single-cell analysis was used to examine gene expression variations in malignant cells post-ICB therapy. This included investigating TUBA1C expression across different ICB response groups and its relationship with CD274. A general module of action was identified through pan-cancer and pan-tissue analysis. TUBA1C expression and its association with clinical characteristics and prognosis was further validated. Multiple algorithms were employed to explore immune cell infiltration levels, and the DepMap database was utilized to assess gene dependency and mutation status in kidney cancer cell lines. The in silico knockout of TUBA1C was performed using deep learning model, complemented by immunohistochemical assays, clinical cohort and functional assays validations. TUBA1C expression is elevated in malignant cells following ICB therapy and is correlated with ICB resistance in ccRCC. High TUBA1C expression activates PI3K/AKT pathway and is associated with increased infiltration of regulatory T cells and myeloid-derived suppressor cells, which contributes to an immunosuppressive microenvironment in ccRCC. Patients with high TUBA1C expression exhibit a greater tumor mutation burden and increased genetic variation, which causes a worse prognosis. Additionally, TUBA1C dependency and its effects were evident in kidney cancer cell lines, where mutations conferred resistance to anti-PD-L1 therapy. In silico knockout analyses indicated that treatment targeting TUBA1C shifted malignant cells to a state responsive to ICB therapy. Immunohistochemistry, RT-qPCR and clinical cohort validation further confirmed that TUBA1C expression was upregulated and contributed to poorer outcome in ccRCC. Finaly, wound healing and CCK-8 assays demonstrated the potent oncogenic function of TUBA1C. TUBA1C is a pivotal regulator in ccRCC, affecting both disease progression and the effectiveness of ICB therapy by fostering an immunosuppressive microenvironment mediated by the PI3K/AKT pathway. Additionally, TUBA1C holds promise, both as a prognostic biomarker and a therapeutic target, for enhancing responsiveness to ICB.

A disulfidptosis-related glucose metabolism and immune response prognostic model revealing the immune microenvironment in lung adenocarcinoma.

Lung adenocarcinoma accounts for the majority of lung cancer cases and impact survival rate of patients severely. Immunotherapy is an effective treatment for lung adenocarcinoma but is restricted by many factors including immune checkpoint expression and the inhibitory immune microenvironment. This study aimed to explore the immune microenvironment in lung adenocarcinoma via disulfidptosis. Public datasets of lung adenocarcinoma from the TCGA and GEO was adopted as the training and validation cohort. Based on the differences in the expression of disulfidptosis -related genes, a glucose metabolism and immune response prognostic model was constructed. The prognostic value and clinical relationship of the model were further explored. Immune-related analyses were performed according to CIBERSORT, ssGSEA, TIDE, IPS. We verified that the model could accurately predict the survival expectancy of lung adenocarcinoma patients. Patients with lung adenocarcinoma and a low-risk score had better survival outcomes according to the model. Moreover, the high-risk group tended to have an immunosuppressive effect, as reflected by the immune cell components, phenotypes and functions. We also found that the clinically relevant immune checkpoint CTLA-4 was significantly higher in low-risk group (P<0.05), indicating that the high-risk group may suffer worse tumor immunotherapy efficacy. Finally, we found that this model has accurate predictive value for the efficacy of immune checkpoint blockade in non-small cell lung cancer (P<0.05). The prognostic model demonstrated the feasibility of predicting survival and immunotherapy efficacy via disulfidptosis-related genes and will facilitate the development of personalized anticancer therapy.

The Tumor Microenvironment Affects Circulating Tumor Cells Metastasis and the Efficacy of Immune Checkpoint Blockade in Non-small Cell Lung Cancer

Abstract: Lung cancer is one of the most lethal malignancies, with non-small cell lung cancer (NSCLC) being the most common histologic subtype. Metastasis leads to poor prognosis for patients with cancer. Tumor cells leave the tumor lesions, invade the surrounding stroma, and enter the bloodstream as circulating tumor cells (CTCs). The development of CTCs is the beginning of metastasis. The internal environment in which tumor cells grow and survive is called the tumor microenvironment (TME). It includes tumor cells, fibroblasts, immune cells, and the extracellular matrix. The TME is complex and dynamic. Moreover, the TME plays an important role in tumor development and metastasis and significantly impacts therapeutic outcomes. Immune checkpoint blockade (ICB) aims to inhibit the interaction of ligands with their corresponding receptors. ICB has the function of restoring the anti-tumor effect of immune cells. This review examines how TME interacts with CTCs, allowing CTCs to evade immunity and facilitating CTC metastasis. TME not only affects the progression of tumor metastasis but also interacts with tumor cells, which may affect the efficacy of immunotherapy.

New Insights into the Link Between Melanoma and Obesity.

The significant increase in the incidence of obesity represents a global health crisis. Obesity is actually a multi-organ disease affecting the entire organism; hence, skin is no exception. As the functional alterations in the adipose tissue are contributing factors to many diseases, including cancer, recently, the link between the development of melanoma skin cancer and obesity gains increased attention. Besides several other factors, the increase of adipose stromal/stem cells (ASCs) impacts cancer progression. Moreover, increased production of cytokines and growth factors done by ASCs induces tumorigenesis and metastasis. The chronic inflammatory state that is sustained by this metabolic imbalance favors skin malignancies, melanoma included. Cutaneous melanoma, as an aggressive skin cancer, has both intrinsic and extrinsic risk factors where sun exposure and lifestyles are the main environmental factors inducing this skin cancer. With the advent of recent targeted and immune-based therapies in melanoma, the link between obesity and the efficacy of these therapies in melanoma remains controversial. A recent molecular relationship between the melanocortin pathway appending to both melanin synthesis and obesity was established. The biology of adipokines, molecules secreted by the adipose tissue, is linked to inflammation, and their molecular pathways can be involved in angiogenesis, migration, invasion, and proliferation of melanoma cells. In melanoma cells, among the most noticeable metabolic reprogramming characteristics is an increased rate of lipid synthesis. Lipid mediators impact classical oncogenic pathways, affecting melanoma progression. The chapter will tackle also the practical implications for melanoma prevention and treatment, namely, how metabolic manipulation can be exploited to overcome immunosuppression and support immune checkpoint blockade efficacy.

Genetic insights into carbohydrate sulfotransferase 8 and its impact on the immunotherapy efficacy of cancer

Immune checkpoint blockade (ICB) is a promising therapy for solid tumors, but its effectiveness depends on biomarkers that are not precise. Here, we utilized genome-wide association study to investigate the association between genetic variants and tumor mutation burden to interpret ICB response. We identified 16 variants (p<5×10-8) probed to 17 genes on 9 chromosomes. Subsequent analysis of one of the most significant loci in 19q13.11 suggested that the rs111308825 locus at the enhancer is causal, as its A allele impairs KLF2 binding, leading to lower carbohydrate sulfotransferase 8 (CHST8) expression. Breast cancer cells expressing CHST8 suppress Tcell activation, and Chst8 loss attenuates tumor growth in a syngeneic mouse model. Further investigation revealed that programmed death-ligand 1 (PD-L1) and its homologs could be sulfated by CHST8, resulting in M2-like macrophage enrichment in the tumor microenvironment. Finally, we confirmed that low-CHST8 tumors have better ICB response, supporting the genetic effect and clinical value of rs111308825 for ICB efficacy prediction.

Comparison of primary and metastatic site-related PD-L1 expression in predicting ORR in patients with advanced NSCLC who received ICB-based therapy.

Whether the value of PD-L1 expression from metastatic sites to predict the efficacy of immune checkpoint blockade (ICB)-based treatment is equivalent to that from a primary tumor is uncertain. This study aimed to compare the utility of PD-L1 TPS from a primary lung tumor and metastatic sites to predict the overall response rate (ORR) of first-line ICB-based treatment. This study included 249 patients with advanced non-small cell lung cancer (NSCLC) who received first-line ICB-based treatment. All subjects underwent PD-L1 testing prior to ICB-based treatment and were divided into two cohorts corresponding to the different biopsy sites: lung primary site-sampled cohort (PT cohort, n = 167) and metastatic site-sampled cohort (MT cohort, n = 82). There was no statistical significance in PD-L1 TPS distribution between the two cohorts (p = 0.742). PD-L1 TPS ≥50% was also related to high ORR compared with PD-L1 < 50% in the PT cohort (34.3% vs. 14.1%, p = 0.004). In contrast, ICB-based therapy could bring comparable ORR (35.1% vs. 33.3%, p = 0.871) in the MT cohort regardless of PD-L1 TPS status (≥50%, or <50%). As supported, when the cutoff value of TPS was selected as 50%, it was suggested that PT-related PD-L1 was the independent predictor of ORR (OR 2.870, 95% CI: 1.231-6.694, p = 0.015) rather than MT-related PD-L1 (OR 0.689, 95% CI: 0.236-2.013, p = 0.495). Furthermore, ROC proved that PT-related PD-L1 expression manifested a better AUC of 0.621 (p = 0.026) than that of MT-related PD-L1 (AUC = 0.565, p = 0.362). Compared with PT-related PD-L1 expression, MT-related PD-L1 expression showed limited value in predicting ORR in patients with advanced NSCLC receiving ICB-based therapy. It was concluded that even patients with low MT-related PD-L1 expression could benefit from ICB-based therapy.

Protein kinase C delta regulates mononuclear phagocytes and hinders response to immunotherapy in cancer.

Mononuclear phagocytes (MPs) play a crucial role in tissue homeostasis; however, MPs also contribute to tumor progression and resistance to immune checkpoint blockade (ICB). Targeting MPs could be an effective strategy to enhance ICB efficacy. We report that protein kinase C delta (PKCδ), a serine/threonine kinase, is abundantly expressed by MPs in human and mouse tumors. PKCδ-/- mice displayed reduced tumor progression compared to wild types, with increased response to anti-PD-1. Tumors from PKCδ-/- mice demonstrated TH1-skewed immune response including increased antigen presentation and T cell activation. Depletion of MPs in vivo altered tumor growth in control but not PKCδ-/- mice. Coinjection of PKCδ-/- M2-like macrophages with cancer cells into wild-type mice markedly delayed tumor growth and significantly increased intratumoral T cell activation compared to PKCδ+/+ controls. PKCδ deficiency reprogrammed MPs by activating type I and type II interferon signaling. Thus, PKCδ might be targeted to reprogram MPs to augment ICB efficacy.

Harnessing p53 to Improve Immunotherapy for Lung Cancer Treatment.

Immunotherapy, especially immune checkpoint blockade (ICB), has become a critical therapy for lung cancer treatment in recent years. Tumor mutational burden (TMB) is one of the decisive biomarkers for predicting ICB effect. Writing in Cancer Cell, Zhu and colleagues use autochthonous and syngeneic mouse models to show that p53 mutation and tumor heterogeneity may be responsible for resistance in patients with lung cancer. Pole-induced high TMB shows enhanced immunogenicity in KrasG12D mice, however, loss of p53 in KrasG12D PoleP286/+ mice can lead to an immune suppressive profile of lung tumors, which diminishes immune response to ICB. Moreover, high TMB causes high shared mutations, which helps promote immune protection and immune memory. Heterogeneity can drive immune escape to tumor cells causing resistance to ICB. Decreased cGAS/STING signaling may explain possible resistance to ICB. On the basis of the new model found by Zhu and colleagues for lung cancer, combined ICB with STING agonists or p53 inducers may be new therapeutic options to improve the efficacy of ICB for patients with lung cancer with high TMB.

Re-"Formate" T-cell Antitumor Responses.

Rowe and colleagues discover that one-carbon (1C) metabolism rewiring occurs upon T-cell activation to support proliferation and cytolytic activity in CD8+ T cells and that supplementation of 1C donor formate rescues the dysfunctional T cells and their responsiveness to anti-PD-1 in selective tumor-infiltrated T-cell subsets. This finding represents an attractive strategy to overcome a metabolic vulnerability in the tumor microenvironment and improve the efficacy of immune checkpoint blockade. See related article by Rowe et al., p. 2566 (8).

CHEK2 deficiency increase the response to PD-1 inhibitors by affecting the tumor immune microenvironment

Immune checkpoint blockade (ICB) therapy has improved treatment effects in multiple cancers. Gene mutations in the DNA damage repair pathway (DDR) may cause genomic instability and may relate to the efficacy of ICB. Checkpoint kinase 2 (CHEK2) and polymerase epsilon (POLE) are important genes in the DDR. In this study, we aimed to study the impact of CHEK2 deficiency mutations on the response to ICB. We found that tumors with CHEK2 mutations had a significantly higher tumor mutational burden (TMB) compared to those with CHEK2-WT in a pancancer database. We noted that CHEK2 deficiency mutations potentiated the anti-tumor effect of anti-PD-1 therapy in MC38 and B16 tumor-bearing mice with the decrease of tumor volume and tumor weight after anti-PD-1 treatment. Mechanistically, CHEK2 deficiency tumors were with the increased cytotoxic CD8+ T-cell infiltration, especially cytotoxic CD8+ T cells, and modulated the tumor-immune microenvironment with an upregulated immune inflammatory pathway and antigen presentation pathway after anti-PD-1 treatment. Furthermore, murine models with POLE mutations confirmed that CHEK2 deficiency shaped similar mutational and immune landscapes as POLE mutations after anti-PD-1 treatment. Taken together, our results demonstrated that CHEK2 deficiency mutations may increase the response to ICB (eg. anti-PD-1) by influencing the tumor immune microenvironment. This indicated that CHEK2 deficiency mutations were a potentially predictive biomarker and CHEK2 deficiency may potentiate response to immunotherapy.

TLR9 plus STING Agonist Adjuvant Combination Induces Potent Neopeptide T Cell Immunity and Improves Immune Checkpoint Blockade Efficacy in a Tumor Model.

Immune checkpoint blockade (ICB) immunotherapies have emerged as promising strategies for the treatment of cancer; however, there remains a need to improve their efficacy. Determinants of ICB efficacy are the frequency of tumor mutations, the associated neoantigens, and the T cell response against them. Therefore, it is expected that neoantigen vaccinations that boost the antitumor T cell response would improve ICB therapy efficacy. The aim of this study was to develop a highly immunogenic vaccine using pattern recognition receptor agonists in combination with synthetic long peptides to induce potent neoantigen-specific T cell responses. We determined that the combination of the TLR9 agonist K-type CpG oligodeoxynucleotides (K3 CpG) with the STING agonist c-di-AMP (K3/c-di-AMP combination) significantly increased dendritic cell activation. We found that immunizing mice with 20-mer of either an OVA peptide, low-affinity OVA peptides, or neopeptides identified from mouse melanoma or lung mesothelioma, together with K3/c-di-AMP, induced potent Ag-specific T cell responses. The combined K3/c-di-AMP adjuvant formulation induced 10 times higher T cell responses against neopeptides than the TLR3 agonist polyinosinic:polycytidylic acid, a derivative of which is the leading adjuvant in clinical trials of neoantigen peptide vaccines. Moreover, we demonstrated that our K3/c-di-AMP vaccine formulation with 20-mer OVA peptide was capable of controlling tumor growth and improving survival in B16-F10-OVA tumor-bearing C57BL/6 mice and synergized with anti-PD-1 treatment. Together, our findings demonstrate that the K3/c-di-AMP vaccine formulation induces potent T cell immunity against synthetic long peptides and is a promising candidate to improve neoantigen vaccine platform.

Abstract C167: An SN38 dendrimer nanoparticle, DEP irinotecan (SN38-SPL9111), demonstrates efficacy in mouse models of gastrointestinal cancer and augments anti-tumor effects of immune checkpoint blockade and PARP inhibition

Abstract Background: Irinotecan is a topoisomerase 1 inhibitor pro-drug used to treat gastrointestinal (GI) cancers including as first line for colorectal cancer (CRC) as part of the FOLFIRI plus monoclonal antibody (mAb) regimen, and for pancreatic cancer in the FOLFIRINOX regimen. However, irinotecan causes severe and dose-limiting side effects, including diarrhea and neutropenia. Starpharma has developed a highly optimized polylysine dendrimer enhanced (DEP) nanoparticle conjugate of the irinotecan active metabolite, SN38 (DEP SN38 or DEP irinotecan). DEP SN38 avoids the need for liver conversion of irinotecan to SN38 and achieves preferential tumor targeting. DEP SN38 is in phase 2 clinical investigation as monotherapy or combination therapy in patients with solid tumors (EudraCT no: 2019-001318-40). SN38 is known to enhance the efficacy of immune checkpoint blockade (ICB) via effects on immune cells in the tumor microenvironment. Here, we evaluated the anti-tumor effects of DEP SN38 alone or in combination with either ICB (anti- programmed cell death-1 [PD1] mAb) or poly adenosine diphosphate (ADP) ribose polymerase (PARP) inhibition (olaparib) in mouse models of GI cancer. Methods: HT29 (human CRC) and CAPAN-1 (human pancreatic cancer) cell line xenografts were established subcutaneously in BALB/c nude or NOD-scid-Gamma immunodeficient mice, respectively. Three doses of DEP SN38 (at 5-10mg/kg SN38) or irinotecan (35-80 mg/kg) were administered intravenously (IV) on days 1, 8, 15. Olaparib (50 mg/kg) was delivered by daily IV injection for 5 days/week over 3 weeks. DEP SN38 (IV on days 1, 8, 15 at 18-35 mg/kg SN38) or irinotecan (75 mg/kg) plus rat anti-PD1 mAb therapy or control mAb (intraperitoneally, 100 mg/kg then 50 mg/kg on days 5, 8, 12) was evaluated in both MC38 (C57BL/6) and CT26 (BALB/c) allograft models of CRC. Toleration of drug was bodyweight loss ≤15%. Results: DEP SN38 treatment of HT29 or CAPAN-1 xenografts led to tumor regressions, prolonged control of tumor growth and improved survival. In contrast, conventional irinotecan had minimal effect on tumor growth versus vehicle control. DEP SN38 was well tolerated by mice with minimal bodyweight loss. Administration of anti-PD1 mAb alone confirmed the known modest sensitivity of MC38, and resistance of CT26 syngeneic tumors, to ICB. DEP SN38 plus anti-PD1 mAb, enhanced anti-tumor responses in the MC38 model beyond those seen for each agent alone and also resulted in tumor eradication and prolonged survival. In the CT26 model, anti-PD1 mAb was also augmented by addition of DEP SN38 but not irinotecan alone, despite resistance of CT26 tumors to anti-PD1 mAb alone. The HT29 CRC model was resistant to Olaparib alone. In contrast, anti-tumor effects and prolonged survival were observed with olaparib plus DEP SN38. Conclusions: DEP SN38 demonstrated superior efficacy compared to irinotecan when used in models of GI cancer. The anti-tumor efficacy of both ICB and PARP inhibition was augmented by DEP SN38 in models of CRC, and these combinations should be investigated clinically. Citation Format: Benjamin J Blyth, Brian D Kelly, Michael Giannis, Anne Cargill, Aynaz Seta, Graham P Heery, Anthony Eglezos, Cameron N Johnstone, Jeremy R A Paull. An SN38 dendrimer nanoparticle, DEP irinotecan (SN38-SPL9111), demonstrates efficacy in mouse models of gastrointestinal cancer and augments anti-tumor effects of immune checkpoint blockade and PARP inhibition [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr C167.