Structural basis of checkpoint blockade by monoclonal antibodies in cancer immunotherapy

Engineered ipilimumab variants that bind human and mouse CTLA-4

Testing of candidate monoclonal antibody therapeutics in preclinical models is an essential step in drug development. Identification of antibody therapeutic candidates that bind their human targets and cross-react to mouse orthologs is often challenging, especially for targets with low sequence homology. In such cases, surrogate antibodies that bind mouse orthologs must be used. The antibody 9D9, which binds mouse CTLA-4, is a commonly used surrogate for CTLA-4 checkpoint blockade studies in mouse cancer models. In this work, we reveal that 9D9 has significant biophysical dissimilarities to therapeutic CTLA-4 antibodies. The 9D9-mCTLA4 complex crystal structure was determined and shows that the surrogate antibody binds an epitope distinct from ipilimumab and tremelimumab. In addition, while ipilimumab has pH-independent binding to hCTLA-4, 9D9 loses binding to mCTLA-4 at physiologically relevant acidic pH ranges. We used phage and yeast display to engineer ipilimumab to bind mouse CTLA-4 with single-digit nM affinity from an initial state with no apparent binding. The engineered variants showed pH-independent and cross-reactive binding to both mouse and human CTLA-4. Crystal structures of a variant in complex with both mouse and human CTLA-4 confirmed that it targets an equivalent epitope as ipilimumab. These cross-reactive ipilimumab variants may facilitate improved translatability and future mechanism-of-action studies for anti-CTLA-4 targeting in murine models.

PTEN-mediated resistance in cancer: From foundation to future therapies

In cancer resistance, phosphatase and tensin homolog deleted (PTEN) has emerged as a prominent protagonist. PTEN exerts its influence by regulating crucial signaling pathways that govern cell proliferation, survival, and differentiation. This comprehensive review article investigates deeply into the complex realm of PTEN-mediated drug resistance mechanisms in cancers. Our journey begins by exploring PTEN's foundational role of PTEN, unveiling its significance as a molecular conductor that intricately coordinates vital cellular pathways. We thoroughly dissected the intricate milieu of PTEN alterations, including mutations, deletions, and epigenetic silencing, and elucidated their profound implications for fueling cancer growth and evading treatment. As we navigate the complex network of PTEN, we unravel the intricate interplay between PTEN and pivotal signaling pathways, such as PI3K/AKT, MAPK/ERK, and Wnt/β-catenin, further complicating the resistance landscape. This expedition, through these intricately intertwined signaling cascades, provides insight into the multifaceted mechanisms driving resistance, thereby revealing potential exploitable weaknesses. In our quest for therapeutic strategies, we need to explore innovative approaches to restore PTEN function, encompassing genetic therapies, pharmacological agents, and precision medicines tailored to PTEN status. The concept of combination therapy has emerged as a potent tool to overcome PTEN-associated resistance, offering promising synergistic interactions with standard treatments, targeted therapies, or immunotherapy. This review offers a comprehensive overview of PTEN-mediated drug resistance mechanisms in cancer and elucidates intricate interactions within this complex landscape. This underscores the central role of PTEN in drug resistance and provides valuable insights into promising strategies with the potential to reshape the future of cancer treatment.

Targeting immune checkpoints in hepatocellular carcinoma therapy: toward combination strategies with curative potential

Hepatocellular carcinoma (HCC) is a primary liver cancer characterized by poor immune cell infiltration and a strongly immunosuppressive microenvironment. Traditional treatments have often yielded unsatisfactory outcomes due to the insidious onset of the disease. Encouragingly, the introduction of immune checkpoint inhibitors (ICIs) has significantly transformed the approach to HCC treatment. Moreover, combining ICIs with other therapies or novel materials is considered the most promising opportunity in HCC, with some of these combinations already being evaluated in large-scale clinical trials. Unfortunately, most clinical trials fail to meet their endpoints, and the few successful ones also face challenges. This indicates that the potential of ICIs in HCC treatment remains underutilized, prompting a reevaluation of this promising therapy. Therefore, this article provides a review of the role of immune checkpoints in cancer treatment, the research progress of ICIs and their combination application in the treatment of HCC, aiming to open up avenues for the development of safer and more efficient immune checkpoint-related strategies for HCC treatment.

A New Protein-Ligand Trapping System to Rapidly Screen and Discover Small-Molecule Inhibitors of PD-L1 from Natural Products

Chinese herbal medicines have played a significant role in the development of new and effective drugs, but how to identify the active ingredients from complex extracts of traditional Chinese herbal medicines was a research difficulty. In recent years, few studies have focused on high-efficiency identification of small-molecule inhibitors of Programmed Death Ligand 1 with lower antigenicity and flexible structure tunability. In order to identify small molecule inhibitors of PD-L1 from complex Chinese herbal extracts, this study established a protein-ligand trapping system based on high-performance liquid chromatography coupled with a photo-diode array detector, ion trap/quadrupole time-of-flight tandem mass spectrometry, and a Programmed Death Ligand 1 affinity chromatography unit (ACPD-L1-HPLC-PDA-IT-TOF (Q-TOF)-MS) to rapidly screen and identify small-molecule inhibitors of Programmed Death Ligand 1 from Toddalia asiatica (L.) Lam. Fourteen components were then identified as PD-L1 binders, and surface plasmon resonance (SPR) validation results showed that six of them-magnoflorine (6), nitidine (22), chelerythrine (24), jatrorrhizine (13), toddaculin (68), and toddanol (45)-displayed PD-L1 binding activity. Laser scanning confocal microscopy results demonstrated that these compounds effectively inhibited the binding of PD-1 to PD-L1 in a dose-dependent manner. Additionally, flow cytometry analysis indicated they could promote human lung cancer cell line (A549) apoptosis when co-cultured with Peripheral Blood Mononuclear Cells (PBMCs). The system's innovation lies in its first integration of dynamic protein-ligand trapping with multi-dimensional validation, coupled with high-throughput screening capacity for structurally diverse natural products. This workflow overcomes traditional phytochemical screening bottlenecks by preserving native protein conformations during affinity capture while maintaining chromatographic resolution, offering a transformative template for accelerating natural product-derived immunotherapeutics through the PD-1/PD-L1 pathway.

Strategy to mitigate aggregation during Protein A chromatography and low pH virus inactivation for a nivolumab biosimilar candidate

Protein A chromatography represents the most prevalent methodology for the capture of monoclonal antibodies. The use of a low pH elution buffer from Protein A has been observed to contribute to product aggregation, particularly in the case of IgG4 antibodies, such as nivolumab. This paper presents a well-defined strategy for addressing this issue. Initial experiments were conducted at scale-down Protein A affinity chromatography to evaluate the use of glycine-HCL and sodium citrate as elution buffers at pH values of 3.25, 3.5, and 3.75. Subsequently, a scale-down screening was conducted to assess the efficacy of various additives in Protein A elution. These included 10 % (w/v) mannitol, 50 mM histidine, 50 mM sucrose, 10 % (v/v) sorbitol, 50 mM arginine, 50 mM trehalose, 0.02 % (v/v) polysorbate 80, 1.5 M urea, and 1 M MgCl2. The three most stabilizing additives were evaluated at the laboratory scale, and the one that demonstrated the greatest ability to maintain the minimum high molecular weight aggregate over time was selected. Lastly, the selected additive was subjected to testing at elevated IgG concentrations during purification. Nivolumab exhibits a markedly pH-dependent propensity for aggregation, and the relative efficacy of glycine-HCL and sodium citrate in mitigating anti-PD1 aggregation within the pH range of 3.25 to 3.75 is subject to variation. The use of buffer 100 mM sodium citrate, pH 3.5 was found to be beneficial. All additives evaluated contribute to reducing nivolumab aggregation, albeit in different ways and to varying degrees of effectiveness. Elution buffer with mannitol, polysorbate 80, or MgCl₂ resulted in a monomer control ratio of approximately twice that observed in the absence of additives. However, the stabilizing role of mannitol was confirmed to be particularly significant, as the ratio of aggregation formed at a low pH was reduced to ≤ 2 % from 15 % in all evaluated scales and at different protein concentrations, while maintaining high biological activity.

Immunomodulatory Peptides for Tumor Treatment

Peptides exhibit various biological activities, including biorecognition, cell targeting, and tumor penetration, and can stimulate immune cells to elicit immune responses for tumor immunotherapy. Peptide self-assemblies and peptide-functionalized nanocarriers can reduce the effect of various biological barriers and the degradation by peptidases, enhancing the efficiency of peptide delivery and improving antitumor immune responses. To date, the design and development of peptides with various functionalities have been extensively reviewed for enhanced chemotherapy; however, peptide-mediated tumor immunotherapy using peptides acting on different immune cells, to the knowledge, has not yet been summarized. Thus, this work provides a review of this emerging subject of research, focusing on immunomodulatory anticancer peptides. This review introduces the role of peptides in the immunomodulation of innate and adaptive immune cells, followed by a link between peptides in the innate and adaptive immune systems. The peptides are discussed in detail, following a classification according to their effects on different innate and adaptive immune cells, as well as immune checkpoints. Subsequently, two delivery strategies for peptides as drugs are presented: peptide self-assemblies and peptide-functionalized nanocarriers. The concluding remarks regarding the challenges and potential solutions of peptides for tumor immunotherapy are presented.

Innovations in cancer immunotherapy: A comprehensive overview of recent breakthroughs and future directions

A major advance in cancer treatment has been the development and refinement of cancer immunotherapy. The discovery of immunotherapies for a wide range of cancers has revolutionized cancer treatment paradigms. Despite relapse or refractory disease, immunotherapy approaches can prolong the life expectancy of metastatic cancer patients. Multiple therapeutic approaches and agents are currently being developed to manipulate various aspects of the immune system. Oncolytic viruses, cancer vaccines, adoptive cell therapies, monoclonal antibodies, cytokine therapies, and inhibitors of immune checkpoints have all proven successful in clinical trials. There are several types of immunotherapeutic approaches available for treating cancer, and others are being tested in preclinical and clinical settings. Immunotherapy has proven successful, and many agents and strategies have been developed to improve its effectiveness. The purpose of this article is to present a comprehensive overview of current immunotherapy approaches used to treat cancer. Cancer immunotherapy advancements, emerging patterns, constraints, and potential future breakthroughs are also discussed.

High-resolution crystal structure of PD-1 in complex with retifanlimab, the FDA-approved immune checkpoint blocking antibody for treating Merkel cell carcinoma

Retifanlimab is a humanized monoclonal antibody that specifically targets programmed cell death protein 1 (PD-1), an essential immune checkpoint that modulates T-cell immune responses. Several anti-PD-1 antibodies have been market-approved, marking a significant advancement in the treatment of diverse tumor types by restoring the T-cell immune response. Recently, the US FDA approved retifanlimab for treating metastatic or recurrent locally advanced Merkel cell carcinoma. We present the crystal structure of PD-1 in complex with the retifanlimab Fab at a resolution of 1.54 Å to elucidate the structural basis for the mechanism of action of this antibody. This work clarifies the detailed interactions and conformational alterations that occur upon antibody binding. The epitope of retifanlimab partially overlaps with the ligand binding site, and its binding induced unique conformations of the flexible loops within PD-1, including BC, C'D, and FG loops, thereby optimizing interactions with the antibody. A thorough analysis of its interaction with PD-1 and other FDA-approved anti-PD-1 antibodies may provide valuable insights into the rational design of enhanced therapies to regulate immune responses in cancer treatment.

Botensilimab, an Fc-Enhanced Anti-CTLA-4 Antibody, Is Effective against Tumors Poorly Responsive to Conventional Immunotherapy

SIGNIFICANCE

This study reveals that Fc-enhanced anti-CTLA-4 harnesses novel mechanisms to overcome the limitations of conventional anti-CTLA-4, effectively treating poorly immunogenic and treatment-refractory cancers. Our findings support the development of a new class of immuno-oncology agents, capable of extending clinical benefit to patients with cancers resistant to current immunotherapies.

Immune checkpoint inhibitors rechallenge in non-small cell lung cancer: Current evidence and future directions

Immunotherapy, remarkably immune checkpoint inhibitors (ICIs), has significantly altered the treatment landscape for non-small cell lung cancer (NSCLC). Despite their success, the discontinuation of ICIs therapy may occur due to factors such as prior treatment completion, disease progression during ICIs treatment, or immune-related adverse events (irAEs). As numerous studies highlight the dynamic nature of immune responses and the sustained benefits of ICIs, ICIs rechallenge has become an attractive and feasible option. However, the decision-making process for ICIs rechallenge in clinical settings is complicated by numerous uncertainties. This review systematically analyses existing clinical research evidence, classifying ICIs rechallenge into distinct clinical scenarios, exploring methods to overcome ICIs resistance in rechallenge instances, and identifying biomarkers to select patients likely to benefit from rechallenge. By integrating recent studies and new technologies, we offer crucial recommendations for future clinical trial design and provide a practical guideline to maximize the therapeutic benefits of immunotherapy for NSCLC patients.

Residue-Specific Epitope Mapping of the PD-1/Nivolumab Interaction Using X-ray Footprinting Mass Spectrometry

X-ray footprinting coupled with mass spectrometry (XFMS) presents a novel approach in structural biology, offering insights into protein conformation and dynamics in the solution state. The interaction of the cancer-immunotherapy monoclonal antibody nivolumab with its antigen target PD-1 was used to showcase the utility of XFMS against the previously published crystal structure of the complex. Changes in side-chain solvent accessibility, as determined by the oxidative footprint of free PD-1 versus PD-1 bound to nivolumab, agree with the binding interface side-chain interactions reported from the crystal structure of the complex. The N-linked glycosylation sites of PD-1 were confirmed through an LC-MS/MS-based deglycosylation analysis of asparagine deamidation. In addition, subtle changes in side-chain solvent accessibility were observed in the C'D loop region of PD-1 upon complex formation with nivolumab.

Comprehensive assessment of TECENTRIQ® and OPDIVO®: analyzing immunotherapy indications withdrawn in triple-negative breast cancer and hepatocellular carcinoma

Atezolizumab (TECENTRIQ®) and nivolumab (OPDIVO®) are both immunotherapeutic indications targeting programmed cell death 1 ligand 1 (PD-L1) and programmed cell death 1 (PD-1), respectively. These inhibitors hold promise as therapies for triple-negative breast cancer (TNBC) and hepatocellular carcinoma (HCC) and have demonstrated encouraging results in reducing the progression and spread of tumors. However, due to their adverse effects and low response rates, the US Food and Drug Administration (FDA) has withdrawn the approval of atezolizumab in TNBC and nivolumab in HCC treatment. The withdrawals of atezolizumab and nivolumab have raised concerns regarding their effectiveness and the ability to predict treatment responses. Therefore, the current study aims to investigate the immunotherapy withdrawal of PD-1/PD-L1 inhibitors, specifically atezolizumab for TNBC and nivolumab for HCC. This study will examine both the structural and clinical aspects. This review provides detailed insights into the structure of the PD-1 receptor and its ligands, the interactions between PD-1 and PD-L1, and their interactions with the withdrawn antibodies (atezolizumab and nivolumab) as well as PD-1 and PD-L1 modifications. In addition, this review further assesses these antibodies in the context of TNBC and HCC. It seeks to elucidate the factors that contribute to diverse responses to PD-1/PD-L1 therapy in different types of cancer and propose approaches for predicting responses, mitigating the potential risks linked to therapy withdrawals, and optimizing patient outcomes. By better understanding the mechanisms underlying responses to PD-1/PD-L1 therapy and developing strategies to predict these responses, it is possible to create more efficient treatments for TNBC and HCC.

Integrating molecular dynamics simulation with small- and wide-angle X-ray scattering to unravel the flexibility, antigen-blocking, and protease-restoring functions in a hindrance-based pro-antibody

Spatial hindrance-based pro-antibodies (pro-Abs) are engineered antibodies to reduce monoclonal antibodies' (mAbs) on-target toxicity using universal designed blocking segments that mask mAb antigen-binding sites through spatial hindrance. By linking through protease substrates and linkers, these blocking segments can be removed site-specifically. Although many types of blocking segments have been developed, such as coiled-coil and hinge-based Ab locks, the molecular structure of the pro-Ab, particularly the region showing how the blocking fragment blocks the mAb, has not been elucidated by X-ray crystallography or cryo-EM. To achieve maximal effect, a pro-Ab must have high antigen-blocking and protease-restoring efficiencies, but the unclear structure limits its further optimization. Here, we utilized molecular dynamics (MD) simulations to study the dynamic structures of a hinge-based Ab lock pro-Ab, pro-Nivolumab, and validated the simulated structures with small- and wide-angle X-ray scattering (SWAXS). The MD results were closely consistent with SWAXS data (χ2 best-fit = 1.845, χ2 allMD = 3.080). The further analysis shows a pronounced flexibility of the Ab lock (root-mean-square deviation = 10.90 Å), yet it still masks the important antigen-binding residues by 57.3%-88.4%, explaining its 250-folded antigen-blocking efficiency. The introduced protease accessible surface area method affirmed better protease efficiency for light chain (33.03 Å2) over heavy chain (5.06 Å2), which aligns with the experiments. Overall, we developed MD-SWAXS validation method to study the dynamics of flexible blocking segments and introduced methodologies to estimate their antigen-blocking and protease-restoring efficiencies, which would potentially be advancing the clinical applications of any spatial hindrance-based pro-Ab.

Mitochondria-Targeted Multifunctional Nanoparticles Combine Cuproptosis and Programmed Cell Death-1 Downregulation for Cancer Immunotherapy

The combination of cuproptosis and immune checkpoint inhibition has shown promise in treating malignant tumors. However, it remains a challenge to deliver copper ions and immune checkpoint inhibitors efficiently and simultaneously to tumors. Herein, a mitochondria-targeted nanoscale coordination polymer particle, Cu/TI, comprising Cu(II), and a triphenylphosphonium conjugate of 5-carboxy-8-hydroxyquinoline (TI), for effective cuproptosis induction and programmed cell death-1 (PD-L1) downregulation is reported. Upon systemic administration, Cu/TI efficiently accumulates in tumor tissues to induce immunogenic cancer cell death and reduce PD-L1 expression. Consequently, Cu/TI promotes the intratumoral infiltration and activation of cytotoxic T lymphocytes to greatly inhibit tumor progression of colorectal carcinoma and triple-negative breast cancer in mouse models without causing obvious side effects.

An in silico investigation on the binding site preference of PD-1 and PD-L1 for designing antibodies for targeted cancer therapy

Cancer control and treatment remain a significant challenge in cancer therapy and recently immune checkpoints has considered as a novel treatment strategy to develop anti-cancer drugs. Many cancer types use the immune checkpoints and its ligand, PD-1/PD-L1 pathway, to evade detection and destruction by the immune system, which is associated with altered effector function of PD-1 and PD-L1 overexpression on cancer cells to deactivate T cells. In recent years, mAbs have been employed to block immune checkpoints, therefore normalization of the anti-tumor response has enabled the scientists to develop novel biopharmaceuticals. In vivo affinity maturation of antibodies in targeted therapy has sometimes failed, and current experimental methods cannot accommodate the accurate structural details of protein-protein interactions. Therefore, determining favorable binding sites on the protein surface for modulator design of these interactions is a major challenge. In this study, we used the in silico methods to identify favorable binding sites on the PD-1 and PD-L1 and to optimize mAb variants on a large scale. At first, all the binding areas on PD-1 and PD-L1 have been identified. Then, using the RosettaDesign protocol, thousands of antibodies have been generated for 11 different regions on PD-1 and PD-L1 and then the designs with higher stability, affinity, and shape complementarity were selected. Next, molecular dynamics simulations and MM-PBSA analysis were employed to understand the dynamic, structural features of the complexes and measure the binding affinity of the final designs. Our results suggest that binding sites 1, 3 and 6 on PD-1 and binding sites 9 and 11 on PD-L1 can be regarded as the most appropriate sites for the inhibition of PD-1-PD-L1 interaction by the designed antibodies. This study provides comprehensive information regarding the potential binding epitopes on PD-1 which could be considered as hotspots for designing potential biopharmaceuticals. We also showed that mutations in the CDRs regions will rearrange the interaction pattern between the designed antibodies and targets (PD-1 and PD-L1) with improved affinity to effectively inhibit protein-protein interaction and block the immune checkpoint.

Current application and future perspective of CRISPR/cas9 gene editing system mediated immune checkpoint for liver cancer treatment

Liver cancer, which is well-known to us as one of human most prevalent malignancies across the globe, poses a significant risk to live condition and life safety of individuals in every region of the planet. It has been shown that immune checkpoint treatment may enhance survival benefits and make a significant contribution to patient prognosis, which makes it a promising and popular therapeutic option for treating liver cancer at the current time. However, there are only a very few numbers of patients who can benefit from the treatment and there also exist adverse events such as toxic effects and so on, which is still required further research and discussion. Fortunately, the clustered regularly interspaced short palindromic repeat/CRISPR-associated nuclease 9 (CRISPR/Cas9) provides a potential strategy for immunotherapy and immune checkpoint therapy of liver cancer. In this review, we focus on elucidating the fundamentals of the recently developed CRISPR/Cas9 technology as well as the present-day landscape of immune checkpoint treatment which pertains to liver cancer. What's more, we aim to explore the molecular mechanism of immune checkpoint treatment in liver cancer based on CRISPR/Cas9 technology. At last, its encouraging and powerful potential in the future application of the clinic is discussed, along with the issues that already exist and the difficulties that must be overcome. To sum up, our ultimate goal is to create a fresh knowledge that we can utilize this new CRISPR/Cas9 technology for the current popular immune checkpoint therapy to overcome the treatment issues of liver cancer.

Engineering Dimeric EGFR-directed IgA Antibodies Reveals a Central Role of CD147 during Neutrophil-mediated Tumor Cell Killing of Head and Neck Squamous Cancer Cells

Human IgA Abs engage neutrophils for cancer immunotherapy more effectively than IgG Abs. Previous studies demonstrated that engineering approaches improved biochemical and functional properties. In this study, we report a novel, to our knowledge, IgA2 Ab against the epidermal growth factor receptor generated by protein engineering and polymerization. The resulting molecule demonstrated a covalent linkage of L and H chains and an effective polymerization by the joining chain. The engineered dimer outperformed its monomeric variant in functional experiments on Fab-mediated modes of action and binding to the Fc receptor. The capacity to engage neutrophils for Ab-dependent cell-mediated cytotoxicity (ADCC) of adherent growing target cancer cells was cell line dependent. Although the engineered dimer displayed a long-term efficacy against the vulva carcinoma cell line A431, there was a notable in-efficacy against human papillomavirus (HPV)- head and neck squamous cell carcinoma (HNSCC) cell lines. However, the highly engineered IgA Abs triggered a neutrophil-mediated cytotoxicity against HPV+ HNSCC cell lines. Short-term ADCC efficacy correlated with the target cells' epidermal growth factor receptor expression and the ability of cancer cell-conditioned media to enhance the CD147 surface level on neutrophils. Notably, the HPV+ HNSCC cell lines demonstrated a significant increment in releasing soluble CD147 and a reduced induction of membranous CD147 on neutrophils compared with HPV- cells. Although membranous CD147 on neutrophils may impair proper IgA-Fc receptor binding, soluble CD147 enhanced the IgA-neutrophil-mediated ADCC in a dose-dependent manner. Thus, engineering IgA Abs and impedance-based ADCC assays provided valuable information regarding the target-effector cell interaction and identified CD147 as a putative critical parameter for neutrophil-mediated cytotoxicity.

Novel Targets and Advanced Therapies in Diffuse Large B Cell Lymphomas

Since the introduction of rituximab in the late 1990s, significant progress has been made in advancing targeted therapies for B cell lymphomas, improving patients' chance of being cured and clinicians' therapeutic armamentarium. A better understanding of disease biology and pathogenic pathways, coupled with refinements in immunophenotypic and molecular diagnostics, have been instrumental in these achievements. While traditional chemotherapy remains fundamental in most cases, concerns surrounding chemorefractoriness and cumulative toxicities, particularly the depletion of the hemopoietic reserve, underscore the imperative for personalized treatment approaches. Integrating targeted agents, notably monoclonal antibodies, alongside chemotherapy has yielded heightened response rates and prolonged survival. A notable paradigm shift is underway with innovative-targeted therapies replacing cytotoxic drugs, challenging conventional salvage strategies like stem cell transplantation. This review examines the landscape of emerging targets for lymphoma cells and explores innovative therapies for diffuse large B cell lymphoma (DLBCL). From Chimeric Antigen Receptor-T cells to more potent monoclonal antibodies, antibody-drug conjugates, bispecific antibodies, checkpoint inhibitors, and small molecules targeting intracellular pathways, each modality offers promising avenues for therapeutic advancement. This review aims to furnish insights into their potential implications for the future of DLBCL treatment strategies.

Alginate-Chitosan Biodegradable and Biocompatible Based Hydrogel for Breast Cancer Immunotherapy and Diagnosis: A Comprehensive Review

Breast cancer is the most common type of cancer and the second leading cause of cancer-related mortality in females. There are many side effects due to chemotherapy and traditional surgery, like fatigue, loss of appetite, skin irritation, and drug resistance to cancer cells. Immunotherapy has become a hopeful approach toward cancer treatment, generating long-lasting immune responses in malignant tumor patients. Recently, hydrogel has received more attention toward cancer therapy due to its specific characteristics, such as decreased toxicity, fewer side effects, and better biocompatibility drug delivery to the particular tumor location. Researchers globally reported various investigations on hydrogel research for tumor diagnosis. The hydrogel-based multilayer platform with controlled nanostructure has received more attention for its antitumor effect. Chitosan and alginate play a leading role in the formation of the cross-link in a hydrogel. Also, they help in the stability of the hydrogel. This review discusses the properties, preparation, biocompatibility, and bioavailability of various research and clinical approaches of the multipolymer hydrogel made of alginate and chitosan for breast cancer treatment. With a focus on cases of breast cancer and the recovery rate, there is a need to find out the role of hydrogel in drug delivery for breast cancer treatment.

Navigating the landscape of PD-1/PD-L1 imaging tracers: from challenges to opportunities

Immunotherapy targeted to immune checkpoint inhibitors, such as the program cell death receptor (PD-1) and its ligand (PD-L1), has revolutionized cancer treatment. However, it is now well-known that PD-1/PD-L1 immunotherapy response is inconsistent among patients. The current challenge is to customize treatment regimens per patient, which could be possible if the PD-1/PD-L1 expression and dynamic landscape are known. With positron emission tomography (PET) imaging, it is possible to image these immune targets non-invasively and system-wide during therapy. A successful PET imaging tracer should meet specific criteria concerning target affinity, specificity, clearance rate and target-specific uptake, to name a few. The structural profile of such a tracer will define its properties and can be used to optimize tracers in development and design new ones. Currently, a range of PD-1/PD-L1-targeting PET tracers are available from different molecular categories that have shown impressive preclinical and clinical results, each with its own advantages and disadvantages. This review will provide an overview of current PET tracers targeting the PD-1/PD-L1 axis. Antibody, peptide, and antibody fragment tracers will be discussed with respect to their molecular characteristics and binding properties and ways to optimize them.

Cancer therapy with antibodies

The greatest challenge in cancer therapy is to eradicate cancer cells with minimal damage to normal cells. Targeted therapy has been developed to meet that challenge, showing a substantially increased therapeutic index compared with conventional cancer therapies. Antibodies are important members of the family of targeted therapeutic agents because of their extraordinarily high specificity to the target antigens. Therapeutic antibodies use a range of mechanisms that directly or indirectly kill the cancer cells. Early antibodies were developed to directly antagonize targets on cancer cells. This was followed by advancements in linker technologies that allowed the production of antibody-drug conjugates (ADCs) that guide cytotoxic payloads to the cancer cells. Improvement in our understanding of the biology of T cells led to the production of immune checkpoint-inhibiting antibodies that indirectly kill the cancer cells through activation of the T cells. Even more recently, bispecific antibodies were synthetically designed to redirect the T cells of a patient to kill the cancer cells. In this Review, we summarize the different approaches used by therapeutic antibodies to target cancer cells. We discuss their mechanisms of action, the structural basis for target specificity, clinical applications and the ongoing research to improve efficacy and reduce toxicity.

Electrochemical evaluation of nivolumab used in cancer treatment with differential pulse voltammetry: A novel approach with single-use pencil graphite electrode

OBJECTIVES

Nivolumab is used in a treatment called immunotherapy, which helps the immune system cells to attack cancer cells. The electrochemical properties and quantification of this drug were performed using single-use pencil tips.

EVIDENCE ACQUISITION

Here, a selective voltammetric method for the determination and electrochemical characterization of Nivolumab used in cancer therapy was developed for the first time using a disposable pencil electrode by cyclic voltammetry and differential pulse voltammetry techniques. Nivolumab exhibited an anodic signal at +0.879 V (vs. Ag/AgCl) in PBS (pH 3.0, 0.02 M NaCl) medium.

RESULTS

This procedure showed a linear response in phosphate buffer solutions (pH 3.0, 0.02 M NaCl) media within the concentration range of 0.01 mg mL-1 to 0.07 mg mL-1 and limit of detection and the limit of quantification values were determined to be 2.49 μg mL-1 and 8.30 μg mL-1, respectively.

CONCLUSIONS

The developed method offers an important analytical approach for the detection and characterization of NIVO. Precisely measuring and monitoring the levels of such drugs in real sample analyses or biological samples is critical for evaluating response to treatment, optimizing treatment strategies. Therefore, the method was applied to real sample analyses. Voltammetric results developed using PG electrode were compared with UV-Vis results. It has been determined that the results obtained are compatible with each other.

Deciphering the role of alternative splicing in neoplastic diseases for immune-oncological therapies

Alternative splicing (AS) is an important molecular biological mechanism regulated by complex mechanisms involving a plethora of cis and trans-acting elements. Furthermore, AS is tissue specific and altered in various pathologies, including infectious, inflammatory, and neoplastic diseases. Recently developed immuno-oncological therapies include monoclonal antibodies (mAbs) and chimeric antigen receptor (CAR) T cells targeting, among others, immune checkpoint (ICP) molecules. Despite therapeutic successes have been demonstrated, only a limited number of patients showed long-term benefit from these therapies with tumor entity-related differential response rates were observed. Interestingly, splice variants of common immunotherapeutic targets generated by AS are able to completely escape and/or reduce the efficacy of mAb- and/or CAR-based tumor immunotherapies. Therefore, the analyses of splicing patterns of targeted molecules in tumor specimens prior to therapy might help correct stratification, thereby increasing therapy success by antibody panel selection and antibody dosages. In addition, the expression of certain splicing factors has been linked with the patients' outcome, thereby highlighting their putative prognostic potential. Outstanding questions are addressed to translate the findings into clinical application. This review article provides an overview of the role of AS in (tumor) diseases, its molecular mechanisms, clinical relevance, and therapy response.

Variable PD-1 glycosylation modulates the activity of immune checkpoint inhibitors

Monoclonal antibodies targeting the immune checkpoint PD-1 have provided significant clinical benefit across a number of solid tumors, with differences in efficacy and toxicity profiles possibly related to their intrinsic molecular properties. Here, we report that camrelizumab and cemiplimab engage PD-1 through interactions with its fucosylated glycan. Using a combination of protein and cell glycoengineering, we demonstrate that the two antibodies bind preferentially to PD-1 with core fucose at the asparagine N58 residue. We then provide evidence that the concentration of fucosylated PD-1 in the blood of non-small-cell lung cancer patients varies across different stages of disease. This study illustrates how glycoprofiling of surface receptors and related circulating forms can inform the development of differentiated antibodies that discriminate glycosylation variants and achieve enhanced selectivity, and paves the way toward the implementation of personalized therapeutic approaches.

Immune checkpoint inhibitors associated cardiovascular immune-related adverse events

Immune checkpoint inhibitors (ICIs) are specialized monoclonal antibodies (mAbs) that target immune checkpoints and their ligands, counteracting cancer cell-induced T-cell suppression. Approved ICIs like cytotoxic T-lymphocyte antigen-4 (CTLA-4), programmed death-1 (PD-1), its ligand PD-L1, and lymphocyte activation gene-3 (LAG-3) have improved cancer patient outcomes by enhancing anti-tumor responses. However, some patients are unresponsive, and others experience immune-related adverse events (irAEs), affecting organs like the lung, liver, intestine, skin and now the cardiovascular system. These cardiac irAEs include conditions like myocarditis, atherosclerosis, pericarditis, arrhythmias, and cardiomyopathy. Ongoing clinical trials investigate promising alternative co-inhibitory receptor targets, including T cell immunoglobulin and mucin domain-containing protein 3 (Tim-3) and T cell immunoreceptor with immunoglobulin and ITIM domain (TIGIT). This review delves into the mechanisms of approved ICIs (CTLA-4, PD-1, PD-L1, and LAG-3) and upcoming options like Tim-3 and TIGIT. It explores the use of ICIs in cancer treatment, supported by both preclinical and clinical data. Additionally, it examines the mechanisms behind cardiac toxic irAEs, focusing on ICI-associated myocarditis and atherosclerosis. These insights are vital as ICIs continue to revolutionize cancer therapy, offering hope to patients, while also necessitating careful monitoring and management of potential side effects, including emerging cardiac complications.

ICAM2 is related to good prognosis in dendritic cell immunotherapy for cancer

Objective: To evaluate the behavior of adhesion molecules ICAM-1 and ICAM-2 in dendritic cell (DC) immunotherapy. Materials & methods: 88 female Balb/c mice were divided into experimental groups. Tumors and lymph nodes were evaluated 7 and 14 days after immunotherapy. Results: Higher mean fluorescence intensity of ICAM-1 in the lymph nodes and tumors in the tumor group at 14 days was observed. Higher mean fluorescence intensity of ICAM-2 in the tumor DC vaccine group was observed after 14 days. A positive correlation was observed in the lymph nodes with ICAM-1 against tumoral volume in the tumor group. A negative correlation was found between ICAM-2 and tumoral volume in the lymph nodes of the tumor group. Conclusion: An increase in ICAM-2 in tumor DC vaccine and a decrease in ICAM-1 suggests the DC vaccine positively influences the immune system and that ICAM-2 could be a marker of good prognosis.

Design and engineering of bispecific antibodies: insights and practical considerations

Bispecific antibodies (bsAbs) have attracted significant attention due to their dual binding activity, which permits simultaneous targeting of antigens and synergistic binding effects beyond what can be obtained even with combinations of conventional monospecific antibodies. Despite the tremendous therapeutic potential, the design and construction of bsAbs are often hampered by practical issues arising from the increased structural complexity as compared to conventional monospecific antibodies. The issues are diverse in nature, spanning from decreased biophysical stability from fusion of exogenous antigen-binding domains to antibody chain mispairing leading to formation of antibody-related impurities that are very difficult to remove. The added complexity requires judicious design considerations as well as extensive molecular engineering to ensure formation of high quality bsAbs with the intended mode of action and favorable drug-like qualities. In this review, we highlight and summarize some of the key considerations in design of bsAbs as well as state-of-the-art engineering principles that can be applied in efficient construction of bsAbs with diverse molecular formats.

Long-term survival in a patient with multiple metastatic gastric cancer treated with PTX plus emvolimab and disitamab vedotin: case report and treatment experience: A case report

RATIONALE

Most Chinese patients with locally advanced gastric cancer at diagnosis have an overall 5-year survival rate of <50%. Surgical resection alone is not suitable for patients with locally advanced gastric cancer. Currently, comprehensive treatment is the focus of locally advanced gastric cancer.

PATIENTS CONCERNS

The patient, a 56-year-old female, was admitted to the hospital because of "4 + months of double hydronephrosis found during a physical examination." Who was admitted for computer tomography and gastroscopy examinations, and take pathological tissue specimens during endoscopic examination.

DIAGNOSES

Computed tomography assessment indicated ulcerative gastric cancer with an abdominal implant, bladder, and bone metastases. An endoscopic examination revealed that the ulcer of the gastric angle was huge, and through relevant auxiliary examinations, the diagnosis of this disease is gastric cancer complicated with multiple metastases to bladder, rectum, lumbar spine, and peritoneum. Clinically diagnosed as cT4bN3M1.

INTERVENTIONS

The patient is currently undergoing first, second, and third line neoadjuvant therapy, combined with immunotherapy, targeted therapy, neoadjuvant intraperitoneal systemic chemotherapy, nutritional support, and other treatment plans.

OUTCOMES

After 15 cycles of treatment, the progression-free survival had reached 15 months. The patient had an NRS2002 score of 1, an ECOG score of I, a quality of life score of 55, albumin of 35.27 g/L, and a decrease in abdominal and pelvic fluid accumulation and exudation compared to before.

LESSONS

We demonstrated high survival of almost 3 years in a patient with gastric cancer that was complicated by bone, peritoneal, rectal, and bladder metastases. The combination of immunotherapy, targeted therapy, and neoadjuvant intraperitoneal systemic chemotherapy, along with the maintenance of nutritional status and CTCs could be a valuable modality for the subsequent treatment and observation of similar patients.

Mapping the epitope of PD-L1 to the paratope of the antibody durvalumab using molecular dynamics simulation

OBJECTIVES

Durvalumab, a human monoclonal antibody that stops PD-L1 from attaching itself to CD80 and PD-1, was approved by the Food and Drug Administration for use in cancer therapy. An essential stage in antibody optimization is mapping paratope residues to epitope residues. In this study, our earlier computer-aided method based on molecular dynamics (MD) simulations was used to observe the paratope residues on durvalumab and their companions on PD-L1.

METHODS

The durvalumab/PD-L1 complex model was obtained from the Protein Data Bank and used in a rectangular box for solvation. On durvalumab, the paratope residues and their companions on PD-L1 were identified using MD simulations. The interface residues were ranked on the basis of their contributions to the binding of durvalumab and PD-L1 by assessing the stability of hydrogen bonds and salt bridges. This assessment was conducted using free and guided MD simulations.

RESULTS

Seventeen residues, including ASP26, GLU58, GLU60, ASP61, ARG113, ARG125, and THR127 on PD-L1 and H31ARG, H52LYS, H53GLN, H57GLU, H99GLU, H103PHE, H113ARG, L28ARG, L31SER, and L92TYR on durvalumab, were expected to be necessary for the binding of durvalumab to PD-L1. ASP26, ARG113, and ARG125 on PD-L1 were essential for its binding to PD-1. Eight residues (GLU60, ASP61, and THR127 on PD-L1 and L31SER, H99GLU, H53GLU, H31ARG, and H113ARG on durvalumab) were newly found, and two residues (LYS124 on PD-L1 and L94SER on durvalumab) proven nonessential for complexation, compared to the findings from the examined crystal structure.

CONCLUSIONS

The antithrombotic antibody of durvalumab's paratope may be effectively mapped to the PD-L1 epitope using the existing computer method. This information will help optimize durvalumab.

Early determination of potential critical quality attributes of therapeutic antibodies in developability studies through surface plasmon resonance-based relative binding activity assessment

Precise measurement of the binding activity changes of therapeutic antibodies is important to determine the potential critical quality attributes (CQAs) in developability assessment at the early stage of antibody development. Here, we report a surface plasmon resonance (SPR)-based relative binding activity method, which incorporates both binding affinity and binding response and allows us to determine relative binding activity of antibodies with high accuracy and precision. We applied the SPR-based relative binding activity method in multiple forced degradation studies of antibody developability assessment. The current developability assessment strategy provided comprehensive, precise characterization of antibody binding activity in the stability studies, enabling us to perform correlation analysis and establish the structure-function relationship between relative binding activity and quality attributes. The impact of a given quality attribute on binding activity could be confidently determined without isolating antibody variants. We identified several potential CQAs, including Asp isomerization, Asn deamidation, and fragmentation. Some potential CQAs affected binding affinity of antibody and resulted in a reduction of binding activity. Certain potential CQAs impaired antibody binding to antigen and led to a loss of binding activity. A few potential CQAs could influence both binding affinity and binding response and cause a substantial decrease in antibody binding activity. Specifically, we identified low abundance Asn33 deamidation in the light chain complementarity-determining region as a potential CQA, in which all the stressed antibody samples showed Asn33 deamidation abundances ranging from 4.2% to 27.5% and a mild binding affinity change from 1.76 nM to 2.16 nM.

Comprehensive physicochemical and functional analysis of pembrolizumab based on controlled degradation studies: Impact on antigen-antibody binding

Monoclonal antibodies-based medicines are widely used in the treatment of different diseases. These medicines are very sensitive to exposure to different environmental conditions and their handling in hospitals may affect their safety and efficacy. This is the case for pembrolizumab (Keytruda®, 25 mg/mL), for which there is not yet much information on its risk behaviour associated with routine handling or unintentional mishandling. Here we performed a wider physicochemical and functional analysis of pembrolizumab medicine including controlled degradation studies: heat, freeze/thaw, agitation, accelerated light exposure and high hypertonic solution. After that, the samples were analysed by a set of analytical techniques to evaluated critical quality attributes: Far-UV CD, IT-FS, DLS, RP/UHPLC(UV)-MS, SE/UHPLC(UV), RP/UHPLC(UV)-MS/MS and ELISA. The results provide an in-depth understanding of the biochemical and biophysical properties of pembrolizumab, showing that the medicine is affected by accelerated light exposure and temperature of 60 °C, demonstrated by the detection of non-natural dimers and HMWS. Light exposure also revealed different isoform profile and increase in oxidations. Regarding functionality by means of the interaction antigen-antibody binding, all the stressors promoted a decrease in pembrolizumab capacity to bind to PD-1 receptor, although the biological activity remained still high for all of them, being 60 °C and accelerated light exposure the most affected.

Explainable machine learning for profiling the immunological synapse and functional characterization of therapeutic antibodies

Therapeutic antibodies are widely used to treat severe diseases. Most of them alter immune cells and act within the immunological synapse; an essential cell-to-cell interaction to direct the humoral immune response. Although many antibody designs are generated and evaluated, a high-throughput tool for systematic antibody characterization and prediction of function is lacking. Here, we introduce the first comprehensive open-source framework, scifAI (single-cell imaging flow cytometry AI), for preprocessing, feature engineering, and explainable, predictive machine learning on imaging flow cytometry (IFC) data. Additionally, we generate the largest publicly available IFC dataset of the human immunological synapse containing over 2.8 million images. Using scifAI, we analyze class frequency and morphological changes under different immune stimulation. T cell cytokine production across multiple donors and therapeutic antibodies is quantitatively predicted in vitro, linking morphological features with function and demonstrating the potential to significantly impact antibody design. scifAI is universally applicable to IFC data. Given its modular architecture, it is straightforward to incorporate into existing workflows and analysis pipelines, e.g., for rapid antibody screening and functional characterization.

Aptamers Targeting the PD-1/PD-L1 Axis: A Perspective

Aptamers have emerged in recent years as alternatives to antibodies or small molecules to interfere with the immune check points by blocking the PD-1/PD-L1 interactions and represent an interesting perspective for immuno-oncology. Aptamers are RNA or DNA nucleotides able to bind to a target with high affinity, with the target ranging from small molecules to proteins and up to cells. Aptamers are identified by the SELEX method that can be modified for specific purposes. The range of applications of aptamers covers therapy as well as new alternative assay technologies similar to ELISA. Aptamers' limited plasma stability can be managed using delivery strategies. The goal of this Perspective is to give an overview of the current development of aptamers targeting the most studied immune checkpoint modulators, PD-1 and PD-L1, and analogous strategies with aptamers for other immuno-related targets.

Progress in programmed cell death-1/programmed cell death-ligand 1 pathway inhibitors and binding mode analysis

Programmed cell death protein 1 (PD-1)/programmed cell death protein ligand 1 (PD-L1) plays an important role in negative regulating immunity. The search for effective PD-1/PD-L1 inhibitors has been at the cutting-edge of academic and industrial medicinal chemistry, leading to the emergence of 16 clinical candidate drugs and the launch of six monoclonal antibodies (mAbs) drugs. However, due to the unclear mechanism of the interaction between drugs and substances in vivo, the screening of preclinical drugs often takes a long time. In order to shorten the time of drug development as much as possible, the binding mode analysis that can simulate the interaction between drugs and substances in vivo at the molecular level can significantly shorten the drug development process. This paper reviews the mechanism of PD-1/PD-L1 signaling pathway at the molecular level, as well as the research progress and obstacles of inhibitors. Besides, we analyzed the binding mode of recently reported PD-1/PD-L1 inhibitors with PD-1 or PD-L1 protein in detail in order to provide ideas for the development of PD-1/PD-L1 inhibitors.

Complete Metabolic Response to Combined Immune Checkpoint Inhibition after Progression of Metastatic Colorectal Cancer on Pembrolizumab: A Case Report

DNA mismatch repair deficient (dMMR) and microsatellite instable (MSI) metastatic colorectal cancer (mCRC) can be successfully treated with FDA- and EMA-approved immune checkpoint inhibitors (ICI) pembrolizumab and nivolumab (as single agents targeting the anti-programmed cell death protein-1 (PD-1)) or combinations of a PD-1 inhibitor with ipilimumab, a cytotoxic T-lymphocyte-associated protein 4 (CTLA-4)-targeting antibody. The best treatment strategy beyond progression on single-agent ICI therapy remains unclear. Here, we present the case of a 63-year-old male with Lynch-syndrome-associated, microsatellite instability-high (MSI-H) mCRC who achieved a rapid normalization of his tumor markers and a complete metabolic remission (CMR), currently lasting for ten months, on sequential ICI treatment with the combination of nivolumab and ipilimumab followed by nivolumab maintenance therapy after progression on single-agent anti-PD-1 ICI therapy. The therapy was well-tolerated, and no immune-related adverse events occurred. To the best of our knowledge, this is the first case of a sustained metabolic complete remission in an MSI-H mCRC patient initially progressing on single-agent anti-PD-1 therapy. Thus, dMMR mCRC patients might benefit from sequential immune checkpoint regimens even with long-term responses. However, further sophistication of clinical algorithms for treatment beyond progression on single-agent ICI therapy in MSI-mCRC is urgently needed.

The Effectiveness of Cancer Immune Checkpoint Inhibitor Retreatment and Rechallenge-A Systematic Review

Despite a great success of immunotherapy in cancer treatment, a great number of patients will become resistant. This review summarizes recent reports on immune checkpoint inhibitor retreatment or rechallenge in order to overcome primary resistance. The systematic review was performed according to PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. The search was performed using PubMed, Web of Science and Scopus. In total, 31 articles were included with a total of 812 patients. There were 16 retreatment studies and 13 rechallenge studies. We identified 15 studies in which at least one parameter (overall response rate or disease control rate) improved or was stable at secondary treatment. Interval treatment, primary response to and the cause of cessation for the first immune checkpoint inhibitors seem to be promising predictors of secondary response. However, high heterogeneity of investigated cohorts and lack of reporting guidelines are limiting factors for current in-depth analysis.

Evaluation of therapeutic PD-1 antibodies by an advanced single-molecule imaging system detecting human PD-1 microclusters

With recent advances in immune checkpoint inhibitors (ICIs), immunotherapy has become the standard treatment for various malignant tumors. Their indications and dosages have been determined empirically, taking individually conducted clinical trials into consideration, but without a standard method to evaluate them. Here we establish an advanced imaging system to visualize human PD-1 microclusters, in which a minimal T cell receptor (TCR) signaling unit co-localizes with the inhibitory co-receptor PD-1 in vitro. In these microclusters PD-1 dephosphorylates both the TCR/CD3 complex and its downstream signaling molecules via the recruitment of a phosphatase, SHP2, upon stimulation with the ligand hPD-L1. In this system, blocking antibodies for hPD-1-hPD-L1 binding inhibits hPD-1 microcluster formation, and each therapeutic antibody (pembrolizumab, nivolumab, durvalumab and atezolizumab) is characterized by a proprietary optimal concentration and combinatorial efficiency enhancement. We propose that our imaging system could digitally evaluate PD-1-mediated T cell suppression to evaluate their clinical usefulness and to develop the most suitable combinations among ICIs or between ICIs and conventional cancer treatments.

Novel Drugs and Radiotherapy in Relapsed Lymphomas: Abscopal Response and Beyond

Combined modality has represented a mainstay of treatment across many lymphoma histologies, given their sensitivity to both multi-agent chemotherapy and intermediate-dose radiotherapy. More recently, several new agents, including immunotherapies, have reshaped the therapeutic panorama of some lymphomas. In parallel, radiotherapy techniques have witnessed substantial improvement, accompanied by a growing understanding that radiation itself comes with an immune-mediated effect. Six decades after a metastatic lesion regression outside the irradiated field was first described, there is increasing evidence that a combination of radiotherapy and immunotherapy could boost an abscopal effect. This review focuses on the mechanisms underlying this interaction in the setting of lymphomas, and on the results of pivotal prospective studies. Furthermore, the available evidence on the concomitant use of radiotherapy and small molecules (i.e., lenalidomide, venetoclax, and ibrutinib), as well as brentuximab vedotin, and chimeric antigen receptor (CAR) T-cell therapy, is summarized. Currently, combining radiotherapy with new agents in patients who are affected by lymphomas appears feasible, particularly as a bridge to anti-CD19 autologous CAR T-cell infusion. However, more studies are required to assess these combinations, and preliminary data suggest only a synergistic rather than a curative effect.

Inside PD-1/PD-L1,2 with their inhibitors

This review summarizes current knowledge in the development of immune checkpoint inhibitors, including antibodies and small molecules.

Mechanisms of action of monoclonal antibodies in oncology integrated in IMGT/mAb-DB

Background

Cancer cells activate different immune checkpoint (IC) pathways in order to evade immunosurveillance. Immunotherapies involving ICs either block or stimulate these pathways and enhance the efficiency of the immune system to recognize and attack cancer cells. In this way, the development of monoclonal antibodies (mAbs) targeting ICs has significant success in cancer treatment. Recently, a systematic description of the mechanisms of action (MOA) of the mAbs has been introduced in IMGT/mAb-DB, the IMGT® database dedicated to mAbs for therapeutic applications. The characterization of these antibodies provides a comprehensive understanding of how mAbs work in cancer.

Methods

In depth biocuration taking advantage of the abundant literature data as well as amino acid sequence analyses from mAbs managed in IMGT/2Dstructure-DB, the IMGT® protein database, allowed to define a standardized and consistent description of the MOA of mAbs targeting immune checkpoints in cancer therapy.

Results

A fine description and a standardized graphical representation of the MOA of selected mAbs are integrated within IMGT/mAb-DB highlighting two main mechanisms in cancer immunotherapy, either Blocking or Agonist. In both cases, the mAbs enhance cytotoxic T lymphocyte (CTL)-mediated anti-tumor immune response (Immunostimulant effect) against tumor cells. On the one hand, mAbs targeting co-inhibitory receptors may have a functional Fc region to increase anti-tumor activity by effector properties that deplete T_reg cells (Fc-effector function effect) or may have limited FcγR binding to prevent T_eff cells depletion and reduce adverse events. On the other hand, agonist mAbs targeting co-stimulatory receptors may bind to FcγRs, resulting in antibody crosslinking (FcγR crosslinking effect) and substantial agonism.

Conclusion

In IMGT/mAb-DB, mAbs for cancer therapy are characterized by their chains, domains and sequence and by several therapeutic metadata, including their MOA. MOAs were recently included as a search criterion to query the database. IMGT® is continuing standardized work to describe the MOA of mAbs targeting additional immune checkpoints and novel molecules in cancer therapy, as well as expanding this study to other clinical domains.

Passive Membrane Permeability of Sizable Acyclic β-Hairpin Peptides

The recent shift toward increasingly larger drug modalities has created a significant demand for novel classes of compounds with high membrane permeability that can inhibit intracellular protein-protein interactions (PPIs). While major advances have been made in the design of cell-permeable helices, stapled β-sheets, and cyclic peptides, the development of large acyclic β-hairpins lags far behind. Therefore, we investigated a series of 26 β-hairpins (MW > 1.6 kDa) belonging to a chemical space far beyond the Lipinski "rule of five" (fbRo5) and showed that, in addition to their innate plasticity, the lipophilicity of these peptides (log D 7.4 ≈ 0 ± 0.7) can be tuned to drastically improve the balance between aqueous solubility and passive membrane permeability.

Rational design of a Nivolumab-based ANTI-PD-1 single chain variable fragment that blocks the interaction between PD-1 expressed on T-CELLS and PD-L1 ON CHO cells

Antibodies that block the interaction between PD-1 expressing T-cells and cancer cells expressing PD-L1 play a central role in contemporary immunotherapy regimes [1-3]. We previously reported the isolation of a single chain variable fragment (scFv) of the monoclonal anti-PD-1 antibody Nivolumab, that binds to purified PD-1 and blocked its interaction with PD-L1 [4]. This anti-PD-1 scFv did not, however, function in a cell-based assay designed to detect the disruption of the PD-1/PD-L1 interaction, a result likely due to its poor solubility in tissue culture media. Herein we report that following a series of structure-based rational design analyses, including Aggreescan3D, we have isolated a variant of the anti-PD-1 scFv having significantly improved solubility in tissue culture medium. Moreover, this soluble anti-PD-1 scFv variant disrupted the interaction between PD-1 expressed on Jurkat Cells and PD-L1 expressed on CHO cells. These findings are discussed in terms of the related observation that the residues mutated to form the anti-PD-1 variant are conserved in many other scFvs; thus, the properties of a range of scFvs will likely be enhanced by similar mutations of the conserved residues.

Characterization of the high-affinity anti-CTLA-4 monoclonal antibody JS007 for immune checkpoint therapy of cancer

Cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) is a critical inhibitory checkpoint molecule, and monoclonal antibodies (mAbs) targeting CTLA-4 that restore anti-tumor T cell immunity have achieved clinical success. Here, we report a humanized IgG1 mAb, namely JS007, with high binding affinity to CTLA-4. JS007 shows superior binding affinity and T-cell activating efficiency over ipilimumab. Moreover, it demonstrates substantial in vivo tumor suppression efficacy at low doses. The crystal structure of JS007/CTLA-4 complex (PDB: 8HIT) shows JS007 adopts a heavy-chain-dominant binding mode, and mainly contacts the BC loop, DE loop and FG loop of CTLA-4. Notably, two Tyr residues (VH-Y100 and VL-Y32) from the complementarity-determining region loops insert into the two cavities formed by the residues from the loops of CTLA-4, which may contribute to the stabilization of the binding. Comparative analysis with other anti-CTLA-4 mAbs indicates that the double "wedge-into-hole" binding mode is unique for JS007 and may be responsible for the high-affinity binding to CTLA-4. These findings have provided an important molecular understanding of the high-affinity CTLA-4 blockade mAbs and shed light on future development of agents targeting CTLA-4.

A Potential Off-Target Effect of the Wnt/β-Catenin Inhibitor KYA1797K: PD-L1 Binding and Checkpoint Inhibition

Introduction

The quest for small molecule inhibitors of the PD-1/PD-L1 checkpoint continues in parallel to the extensive development of monoclonal antibodies directed against this immune checkpoint. Drug screening strategies are being set up to identify novel PD-L1 inhibitors.

Methods

A virtual screening based on molecular docking with the PD-L1 protein dimer has been performed to identify a new binder. Binding of the identified ligand to PD-L1 has been validated experimentally using a microscale thermophoresis (MST) assay. The cellular effect of the compound was evidenced using a fluorescence resonance energy transfer (FRET) assay based on activation of tyrosine phosphatase SHP-2.

Results

We have identified the potent Wnt/β-catenin inhibitor KYA1797K as a weak PD-L1 binder. Molecular docking suggested that the compound can bind to the interface of a PD-L1 dimer, with a geometry superimposable to that of the reference PD-L1 inhibitor BMS-202. The atypical 2-thioxo-4-thiazolidinone motif of KYA1797K, derived from the natural product rhodanine, plays a major role in the interaction with PD-L1. Binding of KYA1797K to recombinant hPD-L1 was validated experimentally, using MST. The drug was found to bind modestly but effectively to hPD-L1. The FRET assay confirmed the weak capacity of KYA1797K to interfere with the activation of SHP-2 upon its interaction with human PD-1.

Discussion

Collectively, the data show that KYA1797K could function as a weak modulator of the PD-1/PD-L1 checkpoint. This effect may contribute, at least partially, to the reported capacity of the β-catenin inhibitor to downregulate PD-L1 in cancer cells. The work also underlines the interest to further consider the rhodanine moiety as a chemical motif for the design of new PD-L1 binders.

Epitope mapping of monoclonal antibodies: a comprehensive comparison of different technologies

Monoclonal antibodies have become an important class of therapeutics in the last 30 years. Because the mechanism of action of therapeutic antibodies is intimately linked to their binding epitopes, identification of the epitope of an antibody to the antigen plays a central role during antibody drug development. The gold standard of epitope mapping, X-ray crystallography, requires a high degree of proficiency with no guarantee of success. Here, we evaluated six widely used alternative methods for epitope identification (peptide array, alanine scan, domain exchange, hydrogen-deuterium exchange, chemical cross-linking, and hydroxyl radical footprinting) in five antibody-antigen combinations (pembrolizumab+PD1, nivolumab+PD1, ipilimumab+CTLA4, tremelimumab+CTLA4, and MK-5890+CD27). The advantages and disadvantages of each technique are demonstrated by our data and practical advice on when and how to apply specific epitope mapping techniques during the drug development process is provided. Our results suggest chemical cross-linking most accurately identifies the epitope as defined by crystallography.

Cutting-edge mass spectrometry strategy based on imaged capillary isoelectric focusing (icIEF) technology for characterizing charge heterogeneity of monoclonal antibody

Imaging capillary isoelectric focusing (icIEF) technology has been becoming the gold criteria of monitoring monoclonal antibody (mAb) charge heterogeneity that is one of the major product-related variants in recombinant biopharmaceuticals, since the first commercial instrument developed twenty years ago. However, the protein identification in icIEF separation is just based on isoelectric point (pI) measurement of protein. Although high resolution mass spectrometry (HRMS) is currently the most powerful means of qualitative protein analysis, traditional icIEF cannot compatibly be used in conjunction with MS due to the use of less volatile reagents. In addition, protein heterogeneity characterization in depth such as peptide mapping by high performance liquid chromatography (HPLC) requires the focused protein bands to be collected as fractions after the icIEF separation, which is a great challenge in biopharmaceutical discovery. In this work, pembrolizumab was employed as targeting mAb (a highly selective anti-PD-1 humanized mAb), an integrated icIEF platform was developed including analytical profiling, MS coupling and fraction collections for charged variant preparation. Multiple operation modes can be rapidly and flexibly switched just by changing customized capillary separation cartridges without more configurations. Main component, four acidic variants (A1-A4) and three basic variants (B1-B3) were baseline separated then directly detected by icIEF-HRMS online coupling for rapid screening of intact protein heterogeneity where reliable and accurate molecular weight of protein charged variants were obtained. Next, by installing preparative capillary separation cartridge, fractions of major charge variants (A2-3 and B1-2) and main component were collected for following LC-MS peptide mapping characterization. The whole workflow of icIEF-based MS strategy for protein heterogeneity is straight forward, reliable and accurate, which provides a comprehensive and revolutionary technology for protein drug quality control (QC) monitoring, MS coupling for fingerprinting intact protein and HPLC-MS peptide mapping in depth.

Advances in the structural characterization of complexes of therapeutic antibodies with PD-1 or PD-L1

Antibody-based immune checkpoint blockade (ICB)-based therapeutics have become effective clinical applications for cancers. Applications of monoclonal antibodies (mAbs) to de-activate the PD-1-PD-L1 pathway could effectively reverse the phenotype of depleted activated thymocytes (T cells) to recover their anti-tumoral activities. High-resolution structures of the complexes of the therapeutic monoclonal antibodies with PD-1 or PD-L1 have revealed the key inter-molecular interactions and provided valuable insights into the fundamental mechanisms by which these antibodies inhibit PD-L1-PD-1 binding. Each anti-PD-1 mAb exhibits a unique blockade mechanism, such as interference with large PD-1-PD-L1 contacting interfaces, steric hindrance by overlapping a small area of this site, or binding to an N-glycosylated site. In contrast, all therapeutic anti-PD-L1 mAbs bind to a similar area of PD-L1. Here, we summarized advances in the structural characterization of the complexes of commercial mAbs that target PD-1 or PD-L1. In particular, we focus on the unique characteristics of those mAb structures, epitopes, and blockade mechanisms. It is well known that the use of antibodies as anti-tumor drugs has increased recently and both PD-1 and PD-L1 have attracted substantial attention as target for antibodies derived from new technologies. By focusing on structural characterization, this review aims to aid the development of novel antibodies targeting PD-1 or PD-L1 in the future.

The High-Resolution Structure Reveals Remarkable Similarity in PD-1 Binding of Cemiplimab and Dostarlimab, the FDA-Approved Antibodies for Cancer Immunotherapy

Multiple tumors have responded well to immunotherapies, which use monoclonal antibodies to block the immune checkpoint proteins and reactivate the T-cell immune response to cancer cells. Significantly, the anti-PD-1 antibodies pembrolizumab and nivolumab, which were approved in 2014, have revolutionized cancer therapy, demonstrating dramatic improvement and longer duration. The US FDA authorized the third anti-PD-1 medication, cemiplimab, in 2018 for use in patients with cutaneous squamous cell carcinoma. To further understand the molecular mechanism of the antibody drug, we now reveal the intricate structure of PD-1 in complex with the cemiplimab Fab at a resolution of 1.98 Å. The cemiplimab-PD-1 interaction preoccupies the space for PD-L1 binding with a greater binding affinity than the PD-1/PD-L1 interaction, which is the basis for the PD-1 blocking mechanism. The structure reveals that cemiplimab and dostarlimab are significantly similar in PD-1 binding, although the precise interactions differ. A comparative investigation of PD-1 interactions with the four FDA-approved antibodies reveals that the BC, C'D, and FG loops of PD-1 adopt distinct conformations for optimal interaction with the antibodies. The structural characteristics in this work could be helpful information for developing more potent anti-PD-1 biologics against cancer.

Novel phthalimides regulating PD-1/PD-L1 interaction as potential immunotherapy agents

Programmed cell death 1(PD-1)/programmed cell death ligand 1(PD-L1) have emerged as one of the most promising immune checkpoint targets for cancer immunotherapy. Despite the inherent advantages of small-molecule inhibitors over antibodies, the discovery of small-molecule inhibitors has fallen behind that of antibody drugs. Based on docking studies between small molecule inhibitor and PD-L1 protein, changing the chemical linker of inhibitor from a flexible chain to an aromatic ring may improve its binding capacity to PD-L1 protein, which was not reported before. A series of novel phthalimide derivatives from structure-based rational design was synthesized. P39 was identified as the best inhibitor with promising activity, which not only inhibited PD-1/PD-L1 interaction (IC₅₀ = 8.9 nmol/L), but also enhanced killing efficacy of immune cells on cancer cells. Co-crystal data demonstrated that P39 induced the dimerization of PD-L1 proteins, thereby blocking the binding of PD-1/PD-L1. Moreover, P39 exhibited a favorable safety profile with a LD₅₀ > 5000 mg/kg and showed significant in vivo antitumor activity through promoting CD8⁺ T cell activation. All these data suggest that P39 acts as a promising small chemical inhibitor against the PD-1/PD-L1 axis and has the potential to improve the immunotherapy efficacy of T-cells.