Development of small molecule drugs targeting immune checkpoints

Immune checkpoint inhibitors(ICIs)are used to relieve and refuel anti-tumor immunity by blocking the interaction,transcription,and translation of co-inhibitory immune checkpoints or degrading co-inhibitory immune checkpoints.Thousands of small molecule drugs or biological materials,especially antibody-based ICIs,are actively being studied and antibodies are currently widely used.Limitations,such as anti-tumor efficacy,poor membrane permeability,and unneglected tolerance issues of antibody-based ICIs,remain evident but are thought to be overcome by small molecule drugs.Recent structural studies have broadened the scope of candidate immune checkpoint molecules,as well as innovative chemical inhibitors.By way of comparison,small molecule drug-based ICIs represent superior oral bioavailability and favorable pharmacokinetic features.Several ongoing clinical trials are exploring the synergetic effect of ICIs and other therapeutic strategies based on multiple ICI functions,including immune regulation,anti-angiogenesis,and cell cycle regulation.In this review we summarized the current progression of small molecule ICIs and the mechanism underlying immune checkpoint proteins,which will lay the foundation for further exploration.

Multiple Defects of Cell Cycle Checkpoints in U937-ASPI3K, an U937 Cell Mutant Stably Expressing Anti-Sense ATM Gene cDNA

(Ataxia-telangiectasia mutated gene (ATM) functions in control of cell cycle checkpoints in responding to DNA damage and protects cells from undergoing apoptosis. Knock-out within tumor cells of endogenous ATM will achieve therapeutic benefits and enable a better understanding of the decisive mechanisms of cell death or survival in response to DNA damaging agents. ) In present paper, we sought to characterize the cell cycle checkpoint profiles in U937-ASPI3K, a U937 cell mutant that was previously established with endogenous ATM knock-out phenotype. Syn- chronized U937-ASPI3K was exposed to 137Cs irradiation, G1, S. G2/M cell cycle checkpoint pro- files were evaluated by determining cell cycle kinetics, p53/p21 protein, cyclin dependent kinase 2 (CDK2) and p34CDC2 kinase activity in response to irradiation. U937-ASPI3K exhibited multiple defects in cell cycle checkpoints as defined by failing to arrest cells upon irradiation. The accumulation of cellular p53/p21 protein and inhibition of CDK kinase was also abolished in U937-ASPI3K. It was concluded that the stable expression of anti-sense PI3K cDNA fragment completely abolished multiple cell cycle checkpoints in U937-ASPI3K, and hence U937-ASPI3K with an AT-like phenotype could serves as a valuable model system for investigating the signal transduction pathway in responding to DNA damaging-based cancer therapy.

Metabolic checkpoints in neurodegenerative T helper 17（TH17） and neuroregenerative regulatory T(Treg) cells as new therapeutic targets for multiple sclerosis

The central nervous system (CNS) is an immune-privileged site with tightly-regulated immune responses, a concept proposed by Nobel Laureate Sir Peter Medawar in 1960. Under physiological conditions, only a few T lymphocytes conducting immunosurveillance can infiltrate the CNS.

NK cell checkpoints and immune therapy in fatty liver disease

Nonalcoholic fatty liver disease and nonalcoholic steatohepatitis(NAFLD and NASH,respectively)are becoming a global epidemic manifested by metabolic syndrome,hepatic fibrosis,and cirrhosis,as well as hepatocellular carcinoma(HCC).Natural killer(NK)cells play an important role in the natural history of the disease as anti-fibrotic and anti-tumor protection.NK cells directly kill activated myofibroblasts to prevent fibrosis progression.However,NK cell functional impairment develops along with insulin resistance and deterioration to cirrhosis and HCC.Metabolic checkpoints have been identified that affect NK cell function and killing.Insulin resistance has been directly identified within NK cells,as they decrease expression of insulin receptors.The normal NK cell activation by insulin is therefore effected.Furthermore,Nerologin-4(NLG4)is overexpressed in impaired NK cells from NAFLD donors with advanced fibrosis.NLG4 overexpression impairs NK cell function and contributes to fibrosis progression.Intracellular NK cell depletion of mT OR,NMDAR activation by liver environmental enrich agonists up-regulates NLG4 expression.NLG4 causes a downstream cascade of intracellular scaffolding proteins to depress the killing function via f-actin remodeling.Berra neuroxin is a defined ligand for NLG4 and is found in target cells including activated fibrotic myofibroblasts and HCC cells.This overexpression further enhanced the NLG4 effect to impair NK cell killing.Other NK cells immune checkpoints have been identified.Targeting metabolic checkpoints activate NK cells to reconstitute their killing effects as anti-fibrotic or anti-tumor.Moreover,NLG4 NK expression and an occult urea assay with myofibroblasts has been identified as a biomarker tool in fibrogenesis.

Understanding the function and dysfunction of the immune system in lung cancer: the role of immune checkpoints

Survival rates for metastatic lung cancer, including non-small cell lung cancer （NSCLC） and small cell lung cancer （SCLC）, are poor with S-year survivals of less than 5%. The immune system has an intricate and complex relationship with tumorigenesis; a groundswell of research on the immune system is leading to greater understanding of how cancer progresses and presenting new ways to halt disease progress. Due to the extraordinary power of the immune system-- with its capacity for memory, exquisite specificity and central and universal role in human biology--immunotherapy has the potential to achieve complete, long-lasting remissions and cures, with few side effects for any cancer patient, regardless of cancer type. As a result, a range of cancer therapies are under development that work by turning our own immune cells against tumors. However deeper understanding of the complexity of immunomodulation by tumors is key to the development of effective immunotherapies, especially in lung cancer.

Myeloid checkpoints for cancer immunotherapy

Myeloid checkpoints are receptors on the myeloid cell surface which can mediate inhibitory signals to modulate anti-tumor immune activities.They can either inhibit cellular phagocytosis or suppress T cells and are thus involved in the pathogenesis of various diseases.In the tumor microenvironment,besides killing tumor cells by phagocytosis or activating anti-tumor immunity by tumor antigen presentation,myeloid cells could execute protumor efficacies through myeloid checkpoints by interacting with counter-receptors on other immune cells or cancer cells.In summary,myeloid checkpoints may be promising therapeutic targets for cancer immunotherapy.

Current state and future of co-inhibitory immune checkpoints for the treatment of glioblastoma

In the interaction between a tumor and the immune system,immune checkpoints play an important role,and in tumor immune escape,co-inhibitory immune checkpoints are important.Immune checkpoint inhibitors(ICIs)can enhance the immune system's killing effect on tumors.To date,impressive progress has been made in a variety of tumor treatments;PD1/PDL1 and CTLA4 inhibitors have been approved for clinical use in some tumors.However,glioblastoma(GBM)still lacks an effective treatment.Recently,a phase III clinical trial using nivolumab to treat recurrent GBM showed no significant improvement in overall survival compared to bevacizumab.Therefore,the use of immune checkpoints in the treatment of GBM still faces many challenges.First,to clarify the mechanism of action,how different immune checkpoints play roles in tumor escape needs to be determined;which biomarkers predict a benefit from ICIs treatment and the therapeutic implications for GBM based on experiences in other tumors also need to be determined.Second,to optimize combination therapies,how different types of immune checkpoints are selected for combined application and whether combinations with targeted agents or other immunotherapies exhibit increased efficacy need to be addressed.All of these concerns require extensive basic research and clinical trials.In this study,we reviewed existing knowledge with respect to the issues mentioned above and the progress made in treatments,summarized the state of ICIs in preclinical studies and clinical trials involving GBM,and speculated on the therapeutic prospects of ICIs in the treatment of GBM.

Intracellular checkpoints for NK cell cancer immunotherapy

Natural killer(NK)cells are key innate immune lymphocytes,which play important roles against tumors.However,tumor-infiltrating NK cells are always hypofunctional/exhaustive.On the one hand,this state is contributed by context-dependent interactions between inhibitory NK cell checkpoint receptors and their ligands,which usually vary in different tumor types and stages during tumor development.On the other hand,the inhibitory functions of intracellular checkpoint molecules of NK cells are more similar across different tumor types,representing common mechanisms limiting the potential of NK cell therapy.In this review,representative NK cell intracellular checkpoint molecules in different aspects of NK cell biology were reviewed,and therapeutic potentials were discussed by targeting these molecules to promote antitumor NK cell therapy.

Human NK cells: surface receptors, inhibitory checkpoints, and translational applications

NK cells play important roles in innate defenses against viruses and in the control of tumor growth and metastasis.The regulation/induction of NK cell function is mediated by an array of activating or inhibitory surface receptors.In humans,major activating receptors involved in target cell killing are the natural cytotoxicity receptors(NCRs)and NKG2D.Activating receptors recognize ligands that are overexpressed or expressed de novo upon cell stress,viral infection,or tumor transformation.The HLA-class I-specific inhibitory receptors,including KIRs recognizing HLA-class I allotypic determinants and CD94/NKG2A recognizing the class-Ib HLA-E,constitute a fail-safe mechanism to avoid unwanted NK-mediated damage to healthy cells.Other receptors such as PD-1,primarily expressed by activated T lymphocytes,are important inhibitory checkpoints of immune responses that ensure T-cell tolerance.PD-1 also may be expressed by NK cells in cancer patients.Since PD-1 ligand(PD-L1)may be expressed by different tumors,PD-1/PD-L1 interactions inactivate both T and NK cells.Thus,the reliable evaluation of PD-L1 expression in tumors has become a major issue to select patients who may benefit from therapy with mAbs disrupting PD-1/PD-L1 interactions.Recently,NKG2A was revealed to be an important checkpoint controlling both NK and T-cell activation.Since most tumors express HLA-E,mAbs targeting NKG2A has been used alone or in combination with other therapeutic mAbs targeting PD-1 or tumor antigens(e.g.,EGFR),with encouraging results.The translational value of NK cells and their receptors is evidenced by the extraordinary therapeutic success of haploidentical HSCT to cure otherwise fatal high-risk leukemias.

Myeloid immunosuppression and immune checkpoints in the tumor microenvironment

Tumor-promoting inflammation and the avoidance of immune destruction are hallmarks of cancer.While innate immune cells,such as neutrophils,monocytes,and macrophages,are critical mediators for sterile and nonsterile inflammation,persistent inflammation,such as that which occurs in cancer,is known to disturb normal myelopoiesis.This disturbance leads to the generation of immunosuppressive myeloid cells,such as myeloid-derived suppressor cells(MDSCs)and tumor-associated macrophages(TAMs).Due to their potent suppressive activities against effector lymphocytes and their abundance in the tumor microenvironment,immunosuppressive myeloid cells act as a major barrier to cancer immunotherapy.Indeed,various therapeutic approaches directed toward immunosuppressive myeloid cells are actively being tested in preclinical and clinical studies.These include antiinflammatory agents,therapeutic blockade of the mobilization and survival of myeloid cells,and immunostimulatory adjuvants.More recently,immune checkpoint molecules expressed on tumor-infiltrating myeloid cells have emerged as potential therapeutic targets to redirect these cells to eliminate tumor cells.In this review,we discuss the complex crosstalk between cancer-related inflammation and immunosuppressive myeloid cells and possible therapeutic strategies to harness antitumor immune responses.

Immune checkpoints in targetedi-mmunotherapy of pancreatic cancer:New hope for clinical development

Immunotherapy has been recently considered as a promising alternative for cancer treatment.Indeed,targeting of immune checkpoint(ICP)strategies have shown significant success in human malignancies.However,despite remarkable success of cancer immunotherapy in pancreatic cancer(PCa),many of the developed immunotherapy methods show poor therapeutic outcomes in PCa with no or few effective treatment options thus far.In this process,immunosuppression in the tumor microenvironment(TME)is found to be the main obstacle to the effectiveness of antitumor immune response induced by an immunotherapy method.In this paper,the latest findings on the ICPs,which mediate immunosuppression in the TME have been reviewed.In addition,different approaches for targeting ICPs in the TME of PCa have been discussed.This review has also synopsized the cutting-edge advances in the latest studies to clinical applications of ICP-targeted therapy in PCa.

Tumor immune checkpoints and their associated inhibitors

Immunological evasion is one of the defining characteristics of cancers,as the immune modification of an immune checkpoint(IC)confers immune evasion capabilities to tumor cells.Multiple ICs,such as programmed cell death protein-1(PD-1)and cytotoxic T-lymphocyte-associated antigen-4(CTLA-4),can bind to their respective receptors and reduce tumor immunity in a variety of ways,including blocking immune cell activation signals.IC blockade(ICB)therapies targeting these checkpoint molecules have demonstrated significant clinical benefits.This is because antibody-based IC inhibitors and a variety of specific small molecule inhibitors can inhibit key oncogenic signaling pathways and induce durable tumor remission in patients with a variety of cancers.Deciphering the roles and regulatory mechanisms of these IC molecules will provide crucial theoretical guidance for clinical treatment.In this review,we summarize the current knowledge on the functional and regulatory mechanisms of these IC molecules at multiple levels,including epigenetic regulation,transcriptional regulation,and post-translational modifications.In addition,we provide a summary of the medications targeting various nodes in the regulatory pathway,and highlight the potential of newly identified IC molecules,focusing on their potential implications for cancer diagnostics and immunotherapy.

Emerging predictors of the response to the blockade of immune checkpoints in cancer therapy

Checkpoint blockade-based immunotherapy offers new options and powerful weapons for the treatment of cancer,but its efficacy varies greatly among different types of cancer and across individual patients.Thus,the development of the right tools that can be used to identify patients who could benefit from this therapy is of utmost importance in order to maximize the therapeutic benefit,minimize risk of toxicities,and guide combination approaches.Multiple predictors have emerged that are based on checkpoint receptor ligand expression,tumor mutational burden,neoantigen and microsatellite instability,tumor-infiltrating immune cells,and peripheral blood biomarkers.In this review,we discuss the current state and progress of predictors as aids in checkpoint blockadebased immunotherapy in cancer.

Targeting immune checkpoints:how to use natural killer cells for fighting against solid tumors

Natural killer(NK)cells are unique innate immune cells that mediate antiviral and anti-tumor responses.Thus,they might hold great potential for cancer immunotherapy.NK cell adoptive immunotherapy in humans has shown modest efficacy.In particular,it has failed to demonstrate therapeutic efficiency in the treatment of solid tumors,possibly due in part to the immunosuppressive tumor microenvironment(TME),which reduces NK cell immunotherapy’s efficiencies.It is known that immune checkpoints play a prominent role in creating an immunosuppressive TME,leading to NK cell exhaustion and tumor immune escape.Therefore,NK cells must be reversed from their dysfunctional status and increased in their effector roles in order to improve the efficiency of cancer immunotherapy.Blockade of immune checkpoints can not only rescue NK cells from exhaustion but also augment their robust anti-tumor activity.In this review,we discussed immune checkpoint blockade strategies with a focus on chimeric antigen receptor(CAR)-NK cells to redirect NK cells to cancer cells in the treatment of solid tumors.

The combination of novel immune checkpoints HHLA2 and ICOSLG:A new system to predict survival and immune features in esophageal squamous cell carcinoma

Studies on immune checkpoint inhibitors targeting B7-CD28 family pathways in esophageal squamous cell carcinoma(ESCC)have shown promising results.However,a comprehensive understanding of B7-CD28 family members in ESCC is still limited.This study aimed to construct a novel B7-CD28 family-based prognosis system to predict survival in patients with ESCC.We collected 179 cases from our previously published microarray data and 86 cases with qPCR data.Specifically,119 microarray data(GSE53624)were used as a training set,whereas the remaining 60 microarray data(GSE53622),all 179 microarray data(GSE53625)and an independent cohort with 86 qPCR data were used for validation.The underlying mechanism and immune landscape of the system were also explored using bioinformatics and immunofluorescence.We examined 13 well-defined B7-CD28 family members and identified 2 genes(ICSOLG and HHLA2)with the greatest prognostic value.A system based on the combination HHLA2 and ICOSLG(B7-CD28 signature)was constructed to distinguish patients as high-or low-risk of an unfavorable outcome,which was further confirmed as an independent prognostic factor.As expected,the signature was well validated in the entire cohort and in the independent cohort,as well as in different clinical subgroups.The signature was found to be closely related to immune-specific biological processes and pathways.Additionally,high-risk group samples demonstrated high infiltration of Tregs and fibroblasts and distinctive immune checkpoint panels.Collectively,we built the first,practical B7-CD28 signature for ESCC that could independently identify high-risk patients.Such information may help inform immunotherapy-based treatment decisions for patients with ESCC.

Immune checkpoints and immunotherapy for colorectal cancer

Colorectal cancer(CRC)remains one of the major causes of death worldwide,despite steady improvement in early detection and overall survival over the past decade.Current treatment paradigms,with chemotherapy and biologics,appear to have reached their maximum benefit.Immunotherapy,especially with checkpoint inhibitors,has shown considerable clinical benefit in various cancers,including mismatch-repair-deficient CRC.This has led to the planning and initiation of several clinical trials evaluating novel immunotherapy agents—as single agents,combinations and in conjunction with chemotherapy—in patients with CRC.This article reviews biological and preclinical data for checkpoint inhibitors and discusses various immunotherapy trials in CRC,as well as current efforts in CRC immunotherapy.

Cytokine release syndrome induced by anti-programmed death-1 treatment in a psoriasis patient:A dark side of immune checkpoint inhibitors

In recent years,cancer immunotherapy has introduced novel treatments,such as monoclonal antibodies,which have facilitated targeted therapies against tumor cells.Programmed death-1(PD-1)is an immune checkpoint expressed in T cells that regulates the immune system’s activity to prevent over-activation and tissue damage caused by inflammation.However,PD-1 is also expressed in tumor cells and functions as an immune evasion mechanism,making it a therapeutic target to enhance the immune response and eliminate tumor cells.Consequently,immune checkpoint inhibitors(ICIs)have emerged as an option for certain tumor types.Nevertheless,blocking immune checkpoints can lead to immune-related adverse events(irAEs),such as psoriasis and cytokine release syndrome(CRS),as exemp-lified in the clinical case presented by Zhou et al involving a patient with adva-nced gastric cancer who received sintilimab,a monoclonal antibody targeting PD-1.Subsequently,the patient experienced exacerbation of psoriasis and CRS.The objective of this editorial article is to elucidate potential immunologic mechanisms that may contribute to the development of CRS and psoriasis in patients receiving ICIs.It is crucial to acknowledge that while ICIs offer superior safety and efficacy compared to conventional therapies,they can also manifest irAEs affecting the skin,gastrointestinal tract,or respiratory system.In severe cases,these irAEs can lead to life-threatening complications such as circulatory shock or multiorgan failure.Consequently,it is recommended that patients receiving ICIs undergo regular monitoring to identify and manage these adverse events effectively.

Prognostic characterization of copper death-related immune checkpoint genes and analysis of immunologic and pharmacologic therapy in bladder cancer

Objective:Copper death-induced tumor cell death and immune checkpoint blockade therapy are highly selective.Combining their advantages and understanding their characteristics in bladder cancer is very important for the development of new targeted therapy.The identification of bladder cancer by screening the characteristic genes of copper death-related immune checkpoints provide a theoretical basis for the selection of adjuvant treatment options and the application of new targets.Methods:The expression samples of normal bladder tissue and bladder cancer were obtained from TCGA and GEO databases,and 13 cop-per death genes and 79 immune checkpoint genes were extracted from previous studies.The mRNA expression of prognostic genes was verified by qPCR.The copper death-related immune checkpoint genes were screened by correlation analysis to construct a prognostic model,and the differences in the efficacy of immunotherapy and chemotherapy between the high-risk group and the low-risk group were evaluated.Results:A prognostic model consisting of BTNL9,CD160,TNFRSF14 and TNFRSF18 was constructed.Its reliable predictive ability was proved in both databases,and qPCR showed that the expression levels of the four genes were significantly different between the normal group and the cancer cell group.The effect of immunotherapy in the lowrisk group was better than that in the high-risk group.Patients in the high-risk group had better chemotherapy efficacy.Conclusion:The copper death-related immune checkpoint gene model can accurately predict the prognosis of patients.Drug and immune analysis provide a basis for clinical treatment,and the discovery of potential targets provides a new solution for clinical decision-making.

Pembrolizumab autoimmune related diabetes:Moving forward,keep learning

Immune checkpoint inhibitors(and more specifically programmed cell death 1/programmed cell death ligand 1 inhibitors as Pembrolizumab)initiated a revolution in the field of melanoma and have now expanded to several tumor subtypes and in increasingly broader clinical contexts,including the adjuvant and neoadjuvant setting,with potentially curable patients and prolonged survival.The side effects related to these drugs include a wide spectrum of manifestations,with endocrinological adverse events being some of the most frequent.Pembrolizumab-induced type 1 diabetes mellitus is an infrequent but potentially serious and not clearly reversible side effect that possesses characteristic clinical features and has high morbidity and mortality,with a chronic impact on quality of life.The etiopathogenesis of this phenomenom needs to be further investigated and a collaborative effort through the involvement of oncologists and other medical specialists is necessary for the correct identification and management of patients at risk.

Immune checkpoint inhibitor-associated gastritis:Patterns and management

Immune checkpoint inhibitors(ICIs)are widely used due to their effectiveness in treating various tumors.Immune-related adverse events(irAEs)are defined as adverse effects resulting from ICI treatment.Gastrointestinal irAEs are a common type of irAEs characterized by intestinal side effects,such as diarrhea and colitis,which may lead to the cessation of ICIs.Although irAE gastritis is rarely reported,it may lead to serious complications such as gastrorrhagia.Furthermore,irAE gastritis is often difficult to identify early due to its diverse symptoms.Although steroid hormones and immunosuppressants are commonly used to reverse irAEs,the best regimen and dosage for irAE gastritis remains uncertain.In addition,the risk of recurrence of irAE gastritis after the reuse of ICIs should be considered.In this editorial,strategies such as early identification,pathological diagnosis,mana-gement interventions,and immunotherapy rechallenge are discussed to enable clinicians to better manage irAE gastritis and improve the prognosis of these patients.