Targeting CD137 (4-1BB) towards improved safety and efficacy for cancer immunotherapy

Development of a tumor-region-selective activation monoclonal antibody targeting the 4-1BB receptor for enhanced therapeutic efficacy and safety

4-1BB is a co-stimulatory immune checkpoint receptor that triggers CD8+ T cell activation, leading to robust anti-tumor responses. Although antibodies targeting 4-1BB show promise in preclinical studies, systemic 4-1BB over-activation can cause severe hepatotoxicity, limiting their clinical use. In this study, we developed Pro-Urelumab, an engineered version of the clinical anti-4-1BB antibody (Urelumab), utilizing an autologous hinge as a spatial hindrance-based antibody lock, linked the antibody and antibody lock with a matrix metalloproteinase-2/9 (MMP-2/9) substrate. This design selectively reactivates Pro-Urelumab within the tumor microenvironment, reducing systemic toxicity. Our results demonstrated that Pro-Urelumab exhibited a 389-fold reduction in binding ability toward the 4-1BB receptor compared to Urelumab, effectively preventing pro-inflammatory cytokine secretion from T cells. After MMP-2/9 cleavage, its agonist activity was fully restored. In a human T-cell-transfer mouse model, Pro-Urelumab avoided the 4-1BB antigen sink effect without causing organ damage. Mice treated with Pro-Urelumab exhibited 100 % survival over 14 days, while all Urelumab-treated mice succumbed to treatment-related toxicity. Additionally, Pro-Urelumab achieved 77 % tumor growth inhibition (TGI), compared to 45 % with Urelumab, and significantly increased T cell activation within the tumor. This study underscores the potential of tumor-selective 4-1BB activation for enhancing both the efficacy and safety of immuno-oncology therapies.

CD19 -targeted CAR T therapy treating hematologic malignancies: hidden danger is the next neighbor to security?

CD19-targeted chimeric antigen receptor (CAR) T-cell therapy has achieved marvelous results in the treatment of patients with relapsed and/or refractory B-cell lymphomas, B-cell acute lymphoblastic leukemia, and multiple myeloma. As a new treatment method that has changed the existing treatment paradigm, there has been a short time from its emergence to FDA approval. However, with the increasing number of cases and the passage of time, hidden problems have gradually been exposed. In this review, we summarize the short- and long-term toxicity, such as secondary T-cell tumors and lethal CAR tumors, of patients with hematologic malignancies treated with CD19-CAR-T cells, including cytokine release syndrome (CRS), ICANS, and secondary malignancies with low occurrence rates but high mortality, such as secondary T cell tumors and lethal CAR tumors, which may be related to the gene modification mechanism of viral vectors currently approved for CAR-T cells. We also discuss potential investigational strategies designed to improve the safety of CAR-T-cell therapy.

Multidimensional applications of prussian blue-based nanoparticles in cancer immunotherapy

Immunotherapy holds notable progress in the treatment of cancer. However, the clinical therapeutic effect remains a significant challenge due to immune-related side effects, poor immunogenicity, and immunosuppressive microenvironment. Nanoparticles have emerged as a revolutionary tool to surmount these obstacles and amplify the potency of immunotherapeutic agents. Prussian blue nanoparticles (PBNPs) exhibit multi-dimensional immune function in cancer immunotherapy, including acting as a nanocarrier to deliver immunotherapeutic agents, as a photothermal agent to improve the efficacy of immunotherapy through photothermal therapy, as a nanozyme to regulate tumor microenvironment, and as an iron donor to induce immune events related to ferroptosis and tumor-associated macrophages polarization. This review focuses on the advances and applications of PBNPs in cancer immunotherapy. First, the biomedical functions of PBNPs are introduced. Then, based on the immune function of PBNPs, we systematically reviewed the multidimensional application of PBNPs in cancer immunotherapy. Finally, the challenges and future developments of PBNPs-based cancer immunotherapy are highlighted.

MD Simulation Reveals a Trimerization-Enhanced Interaction of CD137L with CD137

CD137 is a prominent costimulatory molecule of the tumor necrosis factor (TNF) receptor superfamily that activates T cells through a complex bidirectional signaling process involving CD137L. The clinical value of immunotherapies underscores the potential of CD137L/CD137 as an effective target for boosting antitumor immune responses; however, the intricate mechanisms governing these interactions have not been fully elucidated. Herein, we constructed various oligomeric states of CD137L (monomeric, dimeric, and trimeric CD137L) and explored their interactions with CD137 using molecular dynamics simulations. Our findings revealed that trimeric CD137L exhibits higher thermal stability but reduced binding affinity for CD137 compared with the dimer form, with the A'B' loop of CD137L playing a critical role in both structural stability and promoting CD137 interactions. Notably, the formation of hexameric structures enhanced the binding affinity and stability. This study provides valuable insights into the CD137L/CD137 bidirectional signaling mechanisms, which may inform the design of next-generation CD137 agonists. Ultimately, these advancements may improve cancer immunotherapy strategies, aiming to enhance therapeutic outcomes for patients through more effective and targeted therapies.

Generation and characterization of OX40-ligand fusion protein that agonizes OX40 on T-Lymphocytes

OX40, a member of the tumor necrosis factor (TNF) receptor superfamily, is expressed on the surface of activated T cells. Upon interaction with its cognate ligand, OX40L, OX40 transmits costimulatory signals to antigen-primed T cells, promoting their activation, differentiation, and survival-processes essential for the establishment of adaptive immunity. Although the OX40-OX40L interaction has been extensively studied in the context of disease treatment, developing a substitute for the naturally expressed membrane-bound OX40L, particularly a multimerized OX40L trimers, that effectively regulates OX40-driven T cell responses remains a significant challenge. In this study, we successfully engineered soluble OX40L-fusion proteins capable of robustly activating OX40 on T cells. This was achieved by incorporating functional multimerization domains into the TNF homology domain of OX40L. These OX40L proteins bound to OX40, subsequently activated NF-κB signaling, and induced cytokine production by T cells in vitro. In vivo, mice treated with one of the OX40L-fusion proteins-comprising a single-chain OX40L trimer linked to the C-terminus of the human IgG1 Fc domain, forming a dimer of trimers-exhibited significantly enhanced clonal expansion of antigen-specific CD4+ T cells during the primary phase of the immune response. A comparable antibody-fusion single-chain TNF protein incorporating 4-1BBL, CD70 (CD27L), or GITRL in place of OX40L elicited similar in vivo T cell responses. Thus, we propose that optimizing the multimerization of OX40L proteins through innovative design strategies may facilitate the development of more effective agonists for targeted immunotherapies.

Emerging druggable targets for immune checkpoint modulation in cancer immunotherapy: the iceberg lies beneath the surface

The immune system serves as a fundamental defender against the initiation and progression of cancer. Failure of the immune system augments immunosuppressive action that leading to cancer manifestation. This immunosuppressive effect causes from significant alterations in immune checkpoint expression associated with tumoral progression. The tumor microenvironment promotes immune escape mechanisms that further amplifying immunosuppressive actions. Notably, substantial targeting of immune checkpoints has been pragmatic in the advancement of cancer research. This study highlights a comprehensive review of emerging druggable targets aimed at modulating immune checkpoint co-inhibitory as well as co-stimulatory molecules in response to immune system activation. This modulation has prompted to the development of newer therapeutic insights, eventually inducing immunogenic cell death through immunomodulatory actions. The study emphasizes the role of immune checkpoints in immunogenic regulation of cancer pathogenesis and explores potential therapeutic avenues in cancer immunotherapy.Modulation of Immunosuppressive and Immunostimulatory pathways of immune checkpoints in cancer immunotherapy.

Synthetic and biological nanoparticles for cancer immunotherapy

Cancer is becoming the main public health problem globally. Conventional chemotherapy approaches are slowly being replaced or complemented by new therapies that avoid the loss of healthy tissue, limit off-targets, and eradicate cancer cells. Immunotherapy is nowadays an important strategy for cancer treatment, that uses the host's anti-tumor response by activating the immune system and increasing the effector cell number, while, minimizing cancer's immune-suppressor mechanisms. Its efficacy is still limited by poor therapeutic targeting, low immunogenicity, antigen presentation deficiency, impaired T-cell trafficking and infiltration, heterogeneous microenvironment, multiple immune checkpoints and unwanted side effects, which could benefit from improved delivery systems, able to release immunotherapeutic agents to tumor microenvironment and immune cells. Nanoparticles (NPs) for immunotherapy (Nano-IT), have a huge potential to solve these limitations. Natural and/or synthetic, targeted and/or stimuli-responsive nanoparticles can be used to deliver immunotherapeutic agents in their native conformations to the site of interest to enhance their antitumor activity. They can also be used as co-adjuvants that enhance the activity of IT effector cells. These nanoparticles can be engineered in the natural context of cell-derived extracellular vesicles (EVs) or exosomes or can be fully synthetic. In this review, a detailed SWOT analysis is done through the comparison of engineered-synthetic and naturaly-derived nanoparticles in terms of their current and future use in cancer immunotherapy.

Fc Effector Function of Immune Checkpoint Blocking Antibodies in Oncology

Antagonistic monoclonal antibodies (mAbs) targeting inhibitory immune checkpoints have revolutionized the field of oncology. CTLA-4, PD-1, and LAG3 are three co-inhibitory receptors, which can be expressed by subsets of T cells and which play a role in the regulation of adaptive immune responses. Blocking these immune checkpoints receptors (or their ligands) with antagonistic antibodies can lead to tumor regressions and lasting remissions in some patients with cancer. Two anti-CTLA4, six anti-PD1, three anti-PD-L1, and one anti-LAG3 antibodies are currently approved by the FDA and EMA. Their mechanism of action, safety, and efficacy are linked to their affinity with Fc gamma receptors (FcγR) (so called "effector functions"). The anti-CTLA-4 antibodies ipilimumab (IgG1) and tremilimumab (IgG2a), and the anti-PD-L1 avelumab (IgG1) have isotypes with high affinity for activating FcγR and thereby can induce ADCC/ADCP. The effector function is required for the in vivo efficacy of anti-CTLA4 antibodies. For anti-PD(L)1 antibodies, where a pure antagonistic function ("checkpoint blockade") is sufficient, some mAbs are IgG1 but have been mutated in their Fc sequence (e.g., durvalumab and atezolizumab) or are IgG4 (e.g., nivolumab and pembrolizumab) to have low affinity for FcγR. Here, we review the impact of FcγR effector function on immune checkpoint blockers safety and efficacy in oncology.

Recent advances in mRNA-based cancer vaccines encoding immunostimulants and their delivery strategies

The high prevalence of drug resistance, relapse, and unfavorable response rate of conventional cancer therapies necessitate the development of more efficient treatment modalities. Immunotherapy represents a novel therapeutic approach to cancer treatment in which the immune system's potential is harnessed to recognize and eliminate tumor cells. mRNA cancer vaccines, as a burgeoning field of immunotherapy, have recently drawn particular attention, and among mRNAs encoding tumor-associated antigens, tumor-specific antigens, and immune stimulatory factors, the latter has been relatively less explored. These immunostimulatory mRNAs encode a range of proteins, including stimulatory ligands, receptors, enzymes, pro-inflammatory cytokines, and inhibitory binding proteins, which collectively augment the host immune system's ability against cancerous cells. In this review, we aimed to provide a comprehensive account of mRNA-based cancer vaccines encoding immune stimulants, encompassing their current status, mechanisms of action, delivery strategies employed, as well as recent advances in preclinical and clinical studies. The potential challenges, strategies and future perspectives have also been discussed.

CD137 expression and signal function drive pleiotropic γδ T-cell effector functions that inhibit intracellular M. tuberculosis growth

Co-activation signal that induces/sustains pleiotropic effector functions of antigen-specific γδ T cells remains unknown. Here, Mycobacteria tuberculosis (Mtb) tuberculin administration during tuberculosis (TB) skin test resulted in rapid expression of co-activation signal molecules CD137 and CD107a by fast-acting Vγ2Vδ2 T cells in TB-resistant subjects (Resisters), but not patients with active TB. And, anti-CD137 agonistic antibody treatment experiments showed that CD137 signaling enabled Vγ2Vδ2 T cells to produce more effector cytokines and inhibit intracellular Mtb growth in macrophages (Mɸ). Consistently, Mtb antigen (Ag) HMBPP stimulation induced sustainable high-level CD137 expression in fresh and activated Vγ2Vδ2 T cells from uninfected subjects, but not TB patients. CD137+Vγ2Vδ2 T-cell subtype predominantly displayed central memory phenotype and mounted better proliferative responses than CD137-Vγ2Vδ2 T-cells. In response to HMBPP, CD137+Vγ2Vδ2 T-cell subtype rapidly differentiated into greater numbers of pleiotropic effector cells producing anti-Mtb cytokines compared to CD137-Vγ2Vδ2 T subtype, with the non-canonical NF-κB pathway involved. CD137 expression in Vγ2Vδ2 T cells appeared to signal anti-Mtb effector functions leading to intracellular Mtb growth inhibition in Mɸ, and active TB disrupted such CD137-driven anti-Mtb effector functions. CD137+Vγ2Vδ2 T-cells subtype exhibited an epigenetic-driven high-level expression of GM-CSF and de novo production of GM-CSF critical for Vγ2Vδ2 T-cell controlling of Mtb growth in Mϕ. Concurrently, exosomes produced by CD137+Vγ2Vδ2 T cells potently inhibited intracellular mycobacterial growth. Furthermore, adoptive transfer of human CD137+Vγ2Vδ2 T cells to Mtb-infected SCID mice conferred protective immunity against Mtb infection. Thus, our data suggest that CD137 expression/signaling drives pleiotropic γδ T-cell effector functions that inhibit intracellular Mtb growth.

Modeling T cell temporal response to cancer immunotherapy rationalizes development of combinatorial treatment protocols

Successful immunotherapy relies on triggering complex responses involving T cell dynamics in tumors and the periphery. Characterizing these responses remains challenging using static human single-cell atlases or mouse models. To address this, we developed a framework for in vivo tracking of tumor-specific CD8+ T cells over time and at single-cell resolution. Our tools facilitate the modeling of gene program dynamics in the tumor microenvironment (TME) and the tumor-draining lymph node (tdLN). Using this approach, we characterize two modes of anti-programmed cell death protein 1 (PD-1) activity, decoupling induced differentiation of tumor-specific activated precursor cells from conventional type 1 dendritic cell (cDC1)-dependent proliferation and recruitment to the TME. We demonstrate that combining anti-PD-1 therapy with anti-4-1BB agonist enhances the recruitment and proliferation of activated precursors, resulting in tumor control. These data suggest that effective response to anti-PD-1 therapy is dependent on sufficient influx of activated precursor CD8+ cells to the TME and highlight the importance of understanding system-level dynamics in optimizing immunotherapies.

4-1BB immunotherapy: advances and hurdles

Since its initial description 35 years ago as an inducible molecule expressed in cytotoxic and helper T cells, 4-1BB has emerged as a crucial receptor in T-cell-mediated immune functions. Numerous studies have demonstrated the involvement of 4-1BB in infection and tumor immunity. However, the clinical development of 4-1BB agonist antibodies has been impeded by the occurrence of strong adverse events, notably hepatotoxicity, even though these antibodies have exhibited tremendous promise in in vivo tumor models. Efforts are currently underway to develop a new generation of agonist antibodies and recombinant proteins with modified effector functions that can harness the potent T-cell modulation properties of 4-1BB while mitigating adverse effects. In this review, we briefly examine the role of 4-1BB in T-cell biology, explore its clinical applications, and discuss future prospects in the field of 4-1BB agonist immunotherapy.