Preclinical Characterization and Phase I Trial Results of a Bispecific Antibody Targeting PD-L1 and 4-1BB (GEN1046) in Patients with Advanced Refractory Solid Tumors

Multispecific Antibodies Targeting PD-1/PD-L1 in Cancer

The development of immune checkpoint inhibitors has revolutionized the treatment of patients with cancer. Targeting the programmed cell death protein 1 (PD-1)/programmed cell death 1 ligand 1(PD-L1) interaction using monoclonal antibodies has emerged as a prominent focus in tumor therapy with rapid advancements. However, the efficacy of anti-PD-1/PD-L1 treatment is hindered by primary or acquired resistance, limiting the effectiveness of single-drug approaches. Moreover, combining PD-1/PD-L1 with other immune drugs, targeted therapies, or chemotherapy significantly enhances response rates while exacerbating adverse reactions. Multispecific antibodies, capable of binding to different epitopes, offer improved antitumor efficacy while reducing drug-related side effects, serving as a promising therapeutic approach in cancer treatment. Several bispecific antibodies (bsAbs) targeting PD-1/PD-L1 have received regulatory approval, and many more are currently in clinical development. Additionally, tri-specific antibodies (TsAbs) and tetra-specific antibodies (TetraMabs) are under development. This review comprehensively explores the fundamental structure, preclinical principles, clinical trial progress, and challenges associated with bsAbs targeting PD-1/PD-L1.

Resistance to PD-1/PD-L1 immune checkpoint blockade in advanced non-small cell lung cancer

Lung cancer is one of the most common malignant tumors, of which non-small cell lung cancer (NSCLC) accounts for about 85 %. Although immune checkpoint inhibitors (ICIs), particularly PD-1/PD-L1 inhibitors, have significantly improved the prognosis of patients with NSCLC. There are still many patients do not benefit from ICIs. Primary resistance remains a major challenge in advanced NSCLC. The cancer-immunity cycle describes the process from antigen release to T cell recognition and killing of the tumor, which provides a framework for understanding anti-tumor immunity. The classical cycle consists of seven steps, and alterations at each stage can result in resistance. This review examines the current status of PD-1/PD-L1 blockade in the treatment of advanced NSCLC and explores potential mechanisms of resistance. We summarize the latest clinical trials of PD-1/PD-L1 inhibitors combined with other therapies and explore potential targets for overcoming primary resistance to PD-1/PD-L1 inhibitors.

A mechanistic quantitative systems pharmacology model platform for translational efficacy evaluation and checkpoint combination design of bispecific immuno-modulatory antibodies

Over the past 2 decades, tumor immunotherapies have witnessed remarkable advancements, especially with the emergence of immune checkpoint-targeting bispecific antibodies. However, a quantitative understanding of the dynamic cross-talking mechanisms underlying different immune checkpoints as well as the optimal dosing and target design of checkpoint-targeting bispecific antibodies still remain challenging to researchers. To address this challenge, we have here developed a multi-scale quantitative systems pharmacology (QSP) model platform that integrates a diverse array of immune checkpoints and their interactive functions. The model has been calibrated and validated against an extensive collection of multiscale experimental datasets covering 20+ different monoclonal and bispecific antibody treatments at over 60 administered dose levels. Based on high-throughput simulations, the QSP model platform comprehensively screened and characterized the potential efficacy of different bispecific antibody target combination designs, and model-based preclinical population-level simulations revealed target-specific dose-response relationships as well as alternative dosing strategies that can maintain anti-tumor treatment efficacy while reducing dosing frequencies. Model simulations also pointed out that combining checkpoint-targeting bispecific antibodies with monoclonal antibodies can lead to significantly enhanced anti-tumor efficacy. Our mechanistic QSP model can serve as an integrated precision medicine simulation platform to guide the translational research and clinical development of checkpoint-targeting immuno-modulatory bispecific antibodies.

Acasunlimab, an Fc-inert PD-L1×4-1BB bispecific antibody, combined with PD-1 blockade potentiates antitumor immunity via complementary immune modulatory effects

BACKGROUND

Next-generation cancer immunotherapies aim to improve patient outcomes by combining inhibitory signal blockade with targeted T-cell costimulation in tumor and lymphoid tissues. Acasunlimab (DuoBody-PD-L1×4-1BB) is an investigational, bispecific antibody designed to elicit an antitumor immune response via conditional 4-1BB activation strictly dependent on simultaneous programmed death-ligand 1 (PD-L1) binding. Since 4-1BB is coexpressed with programmed cell death protein-1 (PD-1) on CD8+ T cells, PD-1 blockade and simultaneous costimulation through 4-1BB may synergistically enhance T-cell effector functions. We hypothesized that combining acasunlimab with PD-1 blockade to fully disrupt PD-1 interactions with both PD-L1 and PD-L2 would amplify the depth and duration of antitumor immunity.

METHODS

The effect of acasunlimab and pembrolizumab combination was analyzed in vitro using functional immune cell assays, including mixed-lymphocyte reactions and antigen-specific T-cell proliferation and cytotoxicity assays. The antitumor activity of the combination was tested in vivo in (1) MC38, MB49, Pan02, and B16F10 syngeneic tumor models using acasunlimab and anti-PD-1 mouse-surrogate antibodies; and (2) triple knock-in mice expressing the human targets using an acasunlimab chimeric antibody (chi-acasunlimab) and pembrolizumab. The mechanism of action of the combination was investigated in the MC38 syngeneic model through immunohistochemistry, flow cytometry, and bulk RNA sequencing.

RESULTS

The combination reinvigorated dysfunctional T cells in vitro, while also potentiating T-cell expansion, interleukin (IL)-2 and interferon gamma secretion and cytotoxic activity. In vivo, the combination of chi-acasunlimab and pembrolizumab or mouse-surrogate antibodies potentiated antitumor activity and survival in the humanized knock-in and multiple syngeneic mouse models, leading to durable complete tumor regressions in the MC38 model consistent with therapeutic synergy. Mechanistically, the combination enhanced clonal expansion of tumor-specific CD8+ T cells in tumor-draining lymph nodes and increased the density of proliferating and cytotoxic CD8+ T cells in the tumor microenvironment. It also potentiated the IL-2 signaling pathway, increasing the proportion of granzyme B (GZMB+) stem-like CD8+ T cells thought to have superior effector function.

CONCLUSION

These preclinical results demonstrate that conditional 4-1BB stimulation combined with complete PD-1 blockade enhances antitumor immunity through complementary mechanisms. The acasunlimab and pembrolizumab combination is being evaluated in Phase 2 (NCT05117242) and pivotal Phase 3 (NCT06635824) trials in patients with metastatic non-small cell lung cancer after checkpoint inhibitor therapy failure.

State of the Art of Immune Checkpoint Inhibitors in Unresectable Pancreatic Cancer: A Comprehensive Systematic Review

Immune checkpoint inhibitors (ICIs) have transformed the therapeutic landscape for several malignancies, but their efficacy in unresectable pancreatic adenocarcinoma remains uncertain. This systematic review aimed to evaluate the effectiveness and safety of ICIs in this context, focusing on overall survival (OS), progression-free survival (PFS), objective response rate (ORR), disease control rate (DCR), and toxicity. A comprehensive search of MEDLINE, EMBASE, CENTRAL, and Scopus identified 34 eligible studies, including randomized controlled trials and observational cohorts. Quantitative synthesis involved 21 studies comprising 937 patients, with additional qualitative analyses on biomarker-driven subgroups and early-phase trials. The median OS across studies was 8.65 months, while the median PFS was 2.55 months. The ORR and DCR were 16.2% and 50.3%, respectively, with grade ≥3 treatment-related adverse events occurring in 22% of patients. Promising outcomes were observed in MSI-H/dMMR populations, although these represented only 1-2% of cases. Combination strategies with chemotherapy demonstrated synergistic potential but lacked definitive evidence due to heterogeneity and the absence of phase III trials. ICIs showed a manageable toxicity profile, highlighting their feasibility in selected patients. Future research should focus on overcoming tumor microenvironment barriers and identifying biomarkers to optimize responsiveness and expand the applicability of ICIs in pancreatic cancer.

A Novel Designed Anti-PD-L1/OX40 Bispecific Antibody Augments Both Peripheral and Tumor-Associated Immune Responses for Boosting Antitumor Immunity

Bispecific antibodies (BsAb) combining simultaneous PD-L1 blockade and conditional costimulatory receptor activation have been developed to improve immune checkpoint therapy response. However, several PD-L1-based BsAbs have encountered clinical challenges, including insufficient activity or unexpected toxicity. In this study, we propose OX40 as a more suitable target partner for PD-L1-based BsAb design compared with ongoing clinical partners (CD27 and 4-1BB). We present a novel Fc-silenced tetravalent PD-L1/OX40 BsAb (EMB-09), which efficiently blocks PD-1/PD-L1 interactions and induces PD-L1-dependent OX40 activation, leading to enhanced T-cell activation. EMB-09 demonstrated improved antitumor activity compared with the anti-PD-L1 mAb. Significantly, EMB-09 activated effector memory T cells in the peripheral immune system and promoted the influx of stem-like CD8+ T cells into the tumor site, resulting in a more active phenotype of CD8+ tumor-infiltrating lymphocytes. In an ongoing first-in-human study in patients with advanced refractory solid tumors (NCT05263180), EMB-09 demonstrated a consistent pharmacodynamic response and early efficacy signals.

Targeting novel regulated cell death: disulfidptosis in cancer immunotherapy with immune checkpoint inhibitors

The battle against cancer has evolved over centuries, from the early stages of surgical resection to contemporary treatments including chemotherapy, radiation, targeted therapies, and immunotherapies. Despite significant advances in cancer treatment over recent decades, these therapies remain limited by various challenges. Immune checkpoint inhibitors (ICIs), a cornerstone of tumor immunotherapy, have emerged as one of the most promising advancements in cancer treatment. Although ICIs, such as CTLA-4 and PD-1/PD-L1 inhibitors, have demonstrated clinical efficacy, their therapeutic impact remains suboptimal due to patient-specific variability and tumor immune resistance. Cell death is a fundamental process for maintaining tissue homeostasis and function. Recent research highlights that the combination of induced regulatory cell death (RCD) and ICIs can substantially enhance anti-tumor responses across multiple cancer types. In cells exhibiting high levels of recombinant solute carrier family 7 member 11 (SLC7A11) protein, glucose deprivation triggers a programmed cell death (PCD) pathway characterized by disulfide bond formation and REDOX (reduction-oxidation) reactions, termed "disulfidptosis." Studies suggest that disulfidptosis plays a critical role in the therapeutic efficacy of SLC7A11high cancers. Therefore, to investigate the potential synergy between disulfidptosis and ICIs, this study will explore the mechanisms of both processes in tumor progression, with the goal of enhancing the anti-tumor immune response of ICIs by targeting the intracellular disulfidptosis pathway.

Resistance to immunotherapy in non-small cell lung cancer: Unraveling causes, developing effective strategies, and exploring potential breakthroughs

Over the last two decades, advancements in deciphering the intricate interactions between oncology and immunity have fueled a meteoric rise in immunotherapy for non-small cell lung cancer, typified by an explosive growth of immune checkpoint inhibitors. However, resistance to immunotherapy remains inevitable. Herein we unravel the labyrinthine mechanisms of resistance to immunotherapy, characterized by their involvement of nearly all types of cells within the body, beyond the extrinsic cancer cells, and importantly, such cells are not only (inhibitory or excitatory, or both) signal recipients but also producers, acting in a context-dependent manner. At the molecular level, these mechanisms underlie genetic and epigenetic aberrations, which are regulated by or regulate various protein kinases, growth factors, and cytokines with inherently dynamic and spatially heterogeneous properties. Additionally, macroscopic factors such as nutrition, comorbidities, and the microbiome within and around organs or tumor cells are involved. Therefore, developing therapeutic strategies combined with distinct action informed by preclinical, clinical, and real-world evidence, such as radiotherapy, chemotherapy, targeted therapy, antibody-drug conjugates, oncolytic viruses, and cell-based therapies, may stand as a judicious reality, although the ideality is to overcome resistance point-by-point through a novel drug. Notably, we highlight a realignment of treatment aims, moving the primary focus from eliminating cancer cells -- such as through chemotherapy and radiotherapy -- to promoting immune modulation and underscore the value of regulating various components within the host macro- or micro-environment, as their effects, even if seemingly minimal, can cumulatively contribute to visible clinical benefit when applied in combination with ICIs. Lastly, this review also emphasizes the current hurdles scattered throughout preclinical and clinical studies, and explores evolving directions in the landscape of immunotherapy for NSCLC.

A humanized anti-b7h3×4-1BB bispecific antibody exerts potent antitumour effects through the activation of innate and adaptive immunity

Agonistic monoclonal antibodies targeting 4-1BB have shown much preclinical promise, but their clinical development has been limited by obvious toxicity or unremarkable efficacy. Here, we generated two humanized anti-B7H3 × 4-1BB bsAbs (HK056-001/002) by fusing an anti-4-1BB scFv to the C-terminus of an anti-B7H3 with an intact Fc fragment from human IgG1 or IgG4. The two bsAbs were able to stimulate the 4-1BB signaling pathway, which was strictly dependent on B7H3 expression. In particular, HK056-001 retained Fc function and induced an ADCC effect in tumor cells, whereas HK056-002 did not. Strikingly, HK056-001 showed superior antitumour activity to HK056-002 both in vitro and in vivo. HK056-001 enhanced antitumour immunity and induced lasting antigen-specific immune memory to prevent tumor regrowth upon rechallenge, even at a dose as low as 2 mg/kg. Furthermore, HK056-001 did not induce nonspecific production of proinflammatory cytokines and had no apparent ability to induce ADA production. In addition, HK056-001 has no significant liver toxicity in human 4-1BB-KI BALB/c mice bearing CT26-B7H3 tumors. The optimal anti-B7H3 × 4-1BB bsAb HK056-001 exhibited synergistic antitumour effects by inducing an ADCC effect (innate immunity) and activating the 4-1BB signaling pathway (adaptive immunity) upon cross-bridging with B7H3 with no obvious toxicity, which could potentially provide a better therapeutic window compared to what is seen with 4-1BB agonists.

Divide and Conquer-Targeted Therapy for Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is the most aggressive and malignant type of breast cancer with limited treatment options and poor prognosis. One of the most significant impediments in TNBC treatment is the high heterogeneity of this disease, as highlighted by the detection of several molecular subtypes of TNBC. Each subtype is driven by distinct mutations and pathway aberrations, giving rise to specific molecular characteristics closely connected to clinical behavior, outcomes, and drug sensitivity. This review summarizes the knowledge regarding TNBC molecular subtypes and how it can be harnessed to devise tailored treatment strategies instead of blindly using targeted drugs. We provide an overview of novel targeted agents and key insights about new treatment modalities with an emphasis on the androgen receptor signaling pathway, cancer stem cell-associated pathways, phosphatidylinositol 3-kinase (PI3K)/AKT pathway, growth factor signaling, and immunotherapy.

First-in-human, multicenter, open-label, phase I study of ATOR-1017 (evunzekibart), a 4-1BB antibody, in patients with advanced solid malignancies

BACKGROUND

ATOR-1017 (evunzekibart) is a human agonistic immunoglobulin G4 antibody targeting the costimulatory receptor 4-1BB (CD137). ATOR-1017 activates T cells and natural killer cells in the tumor environment, leading to immune-mediated tumor cell death.

METHODS

In this first-in-human, multicenter, phase I study, ATOR-1017 was administered intravenously every 21 days as a monotherapy to patients with advanced, unresectable solid tumors having received multiple standard-of-care treatments. The study used single patient cohorts for rapid dose escalation up to 40 mg; thereafter a modified 3+3 design up to 900 mg. Escalating doses were given until disease progression, unacceptable toxicity, or withdrawal of consent. The primary objective of the study included determination of the maximum tolerated dose (MTD) via assessment of adverse events and dose-limiting toxicities (DLTs). Secondary objectives included determination of the pharmacokinetics, immunogenicity and clinical efficacy assessed with CT scans using immune Response Evaluation Criteria in Solid Tumors. Exploratory objectives included pharmacodynamic (PD) assessment of immune system biomarkers.

RESULTS

Of the 27 patients screened, 25 received treatment with ATOR-1017. The median time on study was 13.1 weeks (range 4.3-92.3). The MTD of ATOR-1017 was not reached. Treatment-related adverse events (TRAEs) were reported in 13 (52%) of 25 patients; most common (≥10%) were fatigue (n=4 (16.0%) patients) and neutropenia (n=3 (12.0%) patients). Five patients experienced a severe (≥ grade 3) TRAE; neutropenia (n=2), febrile neutropenia (n=1), chest pain (n=1), increased liver enzymes (n=1), and leukopenia and thrombocytopenia (n=1). No patients discontinued due to TRAEs and no DLTs were observed. Pharmacokinetic data demonstrated approximate dose-proportional kinetics. Dose-dependent increases in PD biomarkers, including soluble 4-1BB, are indicative of target-mediated biological activity. Best response was stable disease in 13 out of 25 patients (52%), maintained for 6 months or longer in six patients (24%).

CONCLUSIONS

Treatment with ATOR-1017 was safe and well tolerated at all dose levels and demonstrated biological activity. Furthermore, almost one-third of patients experienced long-lasting stable disease in this heavily pretreated population. The encouraging safety and preliminary efficacy data warrant further clinical development of ATOR-1017, possibly in combination with other anticancer agents.

Covalent Plant Natural Product that Potentiates Antitumor Immunity

Despite the unprecedented therapeutic potential of immune checkpoint antibody therapies, their efficacy is limited partly by the dysfunction of T cells within the cancer microenvironment. Combination therapies with small molecules have also been explored, but their clinical implementation has been met with significant challenges. To search for antitumor immunity activators, the present study developed a cell-based system that emulates cancer-attenuated T cells. The cell-based screening of 232 natural products containing electrophilic reactive functional groups led to the identification of arvenin I, also known as cucurbitacin B 2-O-β-d-glucoside (CuBg), as a plant natural product that activates T cells within the cancer-competitive environment. Chemoproteomic and mechanistic analyses indicated that arvenin I covalently reacts with and hyperactivates MKK3, thereby reviving the mitochondrial fitness of exhausted T cells through the activation of the p38MAPK pathway. In mice, administration of arvenin I enhanced the efficacy of cancer immunotherapy when used alone or in combination with an immune checkpoint inhibitor. These findings highlight the potential of arvenin I as a covalent kinase activator that potentiates antitumor immunity.

Dual targeting PD-L1 and 4-1BB to overcome dendritic cell-mediated lenalidomide resistance in follicular lymphoma

Immunomodulatory agent lenalidomide is effective in treating follicular lymphoma (FL). We conducted the first trial of immunotherapy rituximab plus lenalidomide in newly diagnosed FL in China (NCT03715309). One-hundred and fifteen patients were enrolled and treated with rituximab 375 mg/m2 intravenously on day 0 and lenalidomide 25 mg orally on day 1-10 for 6 cycles of induction treatment, as well as lenalidomide for 6 cycles and rituximab for 8 cycles of maintenance treatment. We found that inferior progression-free survival of the patients was significantly associated with elevated serum β2m and lymph node >6 cm, linking to decreased lymphoma cell autophagy and dendritic cell infiltration within the tumor microenvironment. PU.1 transcriptionally downregulated PD-L1 (Programmed death ligand 1) expression and upregulated 4-1BBL (4-1BB ligand) expression, increased lymphoma cell autophagy and dendritic cell maturation via PD-1/PD-L1 and 4-1BB/4-1BBL interaction. In vitro in co-culture system and in vivo in murine xenograft model, knockdown of PU.1 induced lenalidomide resistance, but sensitized FL cells to bi-specific PD-L1/4-1BB antibody or combined treatment of PD-L1 inhibitor and 4-1BB agonist. Collectively, PU.1 is essential in immunomodulatory effect of FL through PD-1/PD-L1- and 4-1BB/4-1BBL-mediated microenvironmental modulation. Dual targeting PD-L1 and 4-1BB could be an alternative immunotherapeutic strategy in the chemo-free era of FL treatment.

A First-in-Human Study of Cinrebafusp Alfa, a HER2/4-1BB Bispecific Molecule, in Patients with HER2-Positive Advanced Solid Malignancies

PURPOSE

4-1BB (CD137) is a costimulatory immune receptor expressed on activated T cells, activated B cells, NK cells, and tumor-infiltrating lymphocytes, making it a promising target for cancer immunotherapy. Cinrebafusp alfa, a monoclonal antibody-like bispecific protein targeting HER2 and 4-1BB, aims to localize 4-1BB activation to HER2-positive tumors. This study evaluated the safety, tolerability, and preliminary efficacy of cinrebafusp alfa in patients with previously treated HER2-positive malignancies.

PATIENTS AND METHODS

This was a multicenter dose-escalation study involving patients with HER2-positive malignancies who received prior treatment. The study assessed the safety and efficacy of cinrebafusp alfa across various dose levels. Patients were assigned to different cohorts, and antitumor responses were evaluated. The study aimed to determine the MTD and to observe any clinical activity at different dose levels.

RESULTS

Of 40 evaluable patients in the "active dose" efficacy cohorts, five showed an antitumor response, resulting in an overall response rate of 12.5% and a disease-control rate of 52.5%. Clinical activity was observed at the 8 and 18 mg/kg dose levels, with confirmed objective response rates of 28.6% and 25.0%, respectively. Cinrebafusp alfa was safe and tolerable, with grade ≤2 infusion-related reactions being the most frequent treatment-related adverse event. MTD was not reached during the study.

CONCLUSIONS

Cinrebafusp alfa demonstrates promising activity in patients with HER2-positive malignancies who have progressed on prior HER2-targeting regimens. Its acceptable safety profile suggests it could be a treatment option for patients not responding to existing HER2-directed therapies. See related commentary by Eguren-Santamaría et al., p. 231.

Targeting T-Cell Costimulation to the Surface of Tumor Cells

Bispecific agents targeting tumor-cell surface antigens and activating receptors on T lymphocytes are being developed for solid tumors. Effective and safe strategies depend on target specificity and at least relative tumor-tissue confinement of T-cell activation. Novel evidence suggests that constructs targeting HER2 on tumor cells with the aim of providing costimulation (signal 2) to T lymphocytes via cluster of differentiation 137 (4-1BB) are safe and can meaningfully invigorate antitumor responses in a proportion of patients. See related article by Piha-Paul et al., p. 288.

Effective cancer immunotherapy combining mRNA-encoded bispecific antibodies that induce polyclonal T cell engagement and PD-L1-dependent 4-1BB costimulation

Background

Immune checkpoint inhibitors have revolutionized cancer therapy, but many patients fail to respond or develop resistance, often due to reduced T cell activity. Costimulation via 4-1BB has emerged as a promising approach to enhance the effector function of antigen-primed T cells. Bispecific T cell-engaging (TCE) antibodies are an effective way to provide tumor-specific T cell receptor-mediated signaling to tumor-infiltrating lymphocytes. mRNA-based delivery of bispecific antibodies, offer a novel approach to enhance tumor-specific immune responses while minimizing adverse effects.

Methods

Two bispecific antibodies were generated: the EGFR x CD3 TCE antibody (LiTE) and the PD-L1 x 4-1BB costimulatory antibody (LiTCo), which was further fused to a high FcRn albumin variant (Albu-LiTCo). The mRNA encoding these bispecific antibodies contains an N1-methylpseudouridine modified nucleoside and regulatory sequences to ensure proper expression and stability. A series of in vitro assays and cell-based analyses were performed to characterize both antibodies. The in vivo efficacy of the mRNA-encoded bispecific antibodies was evaluated in xenograft tumor models expressing EGFR.

Results

We investigated the combined effect of two mRNA-encoded Fc-free bispecific antibodies with complementary mechanisms of action: an EGFR-targeting TCE and a half-life extended PD-L1 x 4-1BB costimulatory antibody. The mRNAs encoding both bispecific LiTERNA and Albu-LiTCoRNA, showed similar binding specificity and in vitro function to their protein analogues. Pharmacokinetic studies demonstrated sustained expression of both bispecific antibodies following intravenous administration of the mRNAs formulated using a polymer/lipid-based nanoparticle (LNP) but different pharmacokinetic profiles, shorter for the TCE and longer for the PD-L1 x 4-1BB. When administered as a mRNA-LNP combination (ComboRNA), the growth of EGFR-positive tumors in immunocompetent mice was significantly inhibited, resulting in tumor regression in 20% of cases with no associated toxicity. Histological analysis confirmed increased T cell infiltration in the tumors treated with LITERNA and ComboRNA. Repeated administration resulted in sustained production of bispecific antibodies with different exposure cycles and potent antitumor activity with a favorable safety profile.

Conclusions

These results highlight the potential of combining two mRNA-encoded bispecific antibodies with different mechanisms of action and programmable half-life for cancer immunotherapy.

Bispecific therapeutics: a state-of-the-art review on the combination of immune checkpoint ‎inhibition with costimulatory and non-checkpoint targeted therapy

INTRODUCTION

Immune checkpoint inhibitors (ICIs) have revolutionized the field of cancer immunotherapy and have enhanced the survival of patients with malignant tumors. However, the overall efficacy of ICIs remains unsatisfactory and is faced with two major concerns of resistance development and occurrence of immune-related adverse events (irAEs). Bispecific antibodies (bsAbs) have emerged as promising strategies with unique mechanisms of action to achieve a better efficacy and safety than monoclonal antibodies (mAbs) or even their combination. BsAbs along with other bispecific platforms such as bispecific fusion proteins, nanobodies, and CAR-T cells may help to avoid development of resistance and reduce irAEs caused by on-target/off-tumor binding effects of mAbs.

AREAS COVERED

A literature search was performed using PubMed for English-language articles to provide a comprehensive overview of preclinical and clinical studies on bsAbs specified for both immune checkpoints and non-checkpoint molecules as a well-enhanced class of therapeutics.

EXPERT OPINION

Identifying suitable targets and selecting effective engineering platforms enhance the potential of bsAbs to address the challenges associated with conventional therapies such as ICIs, positioning them as a promising class of therapeutics in the landscape of cancer immunotherapy.

Targeting the TNF and TNFR superfamilies in autoimmune disease and cancer

The first anti-tumour necrosis factor (TNF) monoclonal antibody, infliximab (Remicade), celebrated its 25th anniversary of FDA approval in 2023. Inhibitors of TNF have since proved clinically efficacious at reducing inflammation associated with several autoimmune diseases, including rheumatoid arthritis, psoriasis and Crohn's disease. The success of TNF inhibitors raised unrealistic expectations for targeting other members of the TNF superfamily (TNFSF) of ligands and their receptors, with difficulties in part related to their more limited, variable expression and potential redundancy. However, there has been a resurgence of interest and investment, with many of these cytokines or their cognate receptors now under clinical investigation as targets for modulation of autoimmune and inflammatory diseases, as well as cancer. This Review assesses TNFSF-targeted biologics currently in clinical development for immune system-related diseases, highlighting ongoing challenges and future directions.

Progress on angiogenic and antiangiogenic agents in the tumor microenvironment

The development of tumors and their metastasis relies heavily on the process of angiogenesis. When the volume of a tumor expands, the resulting internal hypoxic conditions trigger the body to enhance the production of various angiogenic factors. These include vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF), platelet-derived growth factor (PDGF), and transforming growth factor-α (TGF-α), all of which work together to stimulate the activation of endothelial cells and catalyze angiogenesis. Antiangiogenic therapy (AAT) aims to normalize tumor blood vessels by inhibiting these angiogenic signals. In this review, we will explore the molecular mechanisms of angiogenesis within the tumor microenvironment, discuss traditional antiangiogenic drugs along with their limitations, examine new antiangiogenic drugs and the advantages of combination therapy, and consider future research directions in the field of antiangiogenic drugs. This comprehensive overview aims to provide insights that may aid in the development of more effective anti-tumor treatments.

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.

Tislelizumab: An effective anti-PD-1 antibody for the treatment of advanced basal cell carcinoma of the prostate

Basal cell carcinoma (BCC) of the prostate is a rare and enigmatic tumor with uncertain biological behavior and treatment modalities. Some studies suggest that BCC exhibits invasive characteristics and a high degree of malignancy, necessitating proactive management and vigilant monitoring. Notably, there is a lack of reported effective treatment utilizing programmed cell death protein-1 (PD-1) inhibitors for advanced BCC of the prostate. This study explores the efficacy of tislelizumab, as a single-agent therapy, in the successful treatment of advanced prostate BCC.

Novel Immunotherapeutics for the Treatment of Non-Small Cell Lung Cancer (NSCLC) Resistant to PD-1/PD-L1 Inhibitors

Immunotherapy with PD-1/PD-L1 inhibitors is the standard method of care for the treatment of newly diagnosed advanced or metastatic NSCLC, with or without chemotherapy. Many tumors, however, develop resistance to these immunotherapy agents. There is a need to develop more effective therapies for patients with metastatic NSCLC in the second-line setting and beyond. In this review, we present an overview of novel immunotherapies being investigated regarding the treatment of these patients. We summarize completed, as well as ongoing, trials investigating these therapies as monotherapy or in combination with PD-1/PD-L1 inhibitors. These include immune co-stimulatory antibodies, T-cell agonists, oncolytic viruses, vaccines, TIL therapies, and CAR-T therapies.

Combining mathematical modeling, in vitro data and clinical target expression to support bispecific antibody binding affinity selection: a case example with FAP-4-1BBL

The majority of bispecific costimulatory antibodies in cancer immunotherapy are capable of exerting tumor-specific T-cell activation by simultaneously engaging both tumor-associated targets and costimulatory receptors expressed by T cells. The amount of trimeric complex formed when the bispecific antibody is bound simultaneously to the T cell receptor and the tumor-associated target follows a bell-shaped curve with increasing bispecific antibody exposure/dose. The shape of the curve is determined by the binding affinities of the bispecific antibody to its two targets and target expression. Here, using the case example of FAP-4-1BBL, a fibroblast activation protein alpha (FAP)-directed 4-1BB (CD137) costimulator, the impact of FAP-binding affinity on trimeric complex formation and pharmacology was explored using mathematical modeling and simulation. We quantified (1) the minimum number of target receptors per cell required to achieve pharmacological effect, (2) the expected coverage of the patient population for 19 different solid tumor indications, and (3) the range of pharmacologically active exposures as a function of FAP-binding affinity. A 10-fold increase in FAP-binding affinity (from a dissociation constant [KD] of 0.7 nM-0.07 nM) was predicted to reduce the number of FAP receptors needed to achieve 90% of the maximum pharmacological effect from 13,400 to 4,000. Also, the number of patients with colon cancer that would achieve 90% of the maximum effect would increase from 6% to 39%. In this work, a workflow to select binding affinities for bispecific antibodies that integrates preclinical in vitro data, mathematical modeling and simulation, and knowledge on target expression in the patient population, is provided. The early implementation of this approach can increase the probability of success with cancer immunotherapy in clinical development.

Developing combination therapies with biologics in triple-negative breast cancer

INTRODUCTION

Novel compounds have entered the triple-negative breast cancer (TNBC) treatment algorithm, namely immune checkpoints inhibitors (ICIs), PARP inhibitors and antibody-drug conjugates (ADCs). The optimization of treatment efficacy can be enhanced with the use of combination treatments, and the incorporation of novel compounds. In this review, we discuss the combination treatments under development for the treatment of TNBC.

AREAS COVERED

The development of new drugs occurring in recent years has boosted the research for novel combinations to target TNBC heterogeneity and improve outcomes. ICIs, ADCs, tyrosine kinase inhibitors (TKIs), and PARP inhibitors have emerged as leading players in this new landscape, while other compounds like novel intracellular pathways inhibitors or cancer vaccines are drawing more and more interest. The future of TNBC is outlined in combination approaches, and based on new cancer targets, including many chemotherapy-free treatments.

EXPERT OPINION

A large number of TNBC therapies have either proved clinically ineffective or weighted by unacceptable safety profiles. Others, however, have provided promising results and are currently in late-stage clinical trials, while a few have actually changed clinical practice in recent years. As novel, more and more selective drugs come up, combination strategies focusing the concept of synergy are fully warranted for the future.

Anti-4-1BB×PDL1 Bispecific Antibody Reinvigorates Tumor-Specific Exhausted CD8+ T Cells and Enhances the Efficacy of Anti-PD1 Blockade

PURPOSE

To overcome the limited efficacy of immune checkpoint blockade, there is a need to find novel cancer immunotherapeutic strategies for the optimal treatment of cancer. The novel anti-4-1BB×PDL1 bispecific antibody-ABL503 (also known as TJ-L14B)-was designed to simultaneously target PDL1 and 4-1BB and demonstrated strong antitumor T-cell responses without considerable toxicity. In this study, we investigated the mechanisms by which the combination of ABL503 and anti-PD1 blockade affected the reinvigoration of exhausted tumor-infiltrating CD8+ T cells (CD8+ TIL) and antitumor efficacy.

EXPERIMENTAL DESIGN

Single-cell suspensions of hepatocellular carcinoma and ovarian cancer tissues from treatment-naïve patients were used for immunophenotyping of CD8+ TILs and in vitro functional assays. Humanized hPD1/hPDL1/h4-1BB triple-knock-in mice were used to evaluate the effects of ABL503 and anti-PD1 blockade in vivo.

RESULTS

We observed that ABL503 successfully restored the functions of 4-1BB+ exhausted CD8+ TILs, which were enriched for tumor-specific T cells but unresponsive to anti-PD1 blockade. Importantly, compared with anti-PD1 blockade alone, the combination of ABL503 and anti-PD1 blockade further enhanced the functional restoration of human CD8+ TILs in vitro. Consistently, the combination of ABL503 with anti-PD1 in vivo significantly alleviated tumor growth and induced enhanced infiltration and activation of CD8+ TILs.

CONCLUSIONS

ABL503, a PDL1 and 4-1BB dual-targeting bispecific antibody, elicits pronounced additive tumor growth inhibition, with increased infiltration and functionality of exhausted CD8+ T cells, which in turn enhances the anticancer effects of anti-PD1 blockade. These promising findings suggest that ABL503 (TJ-L14B) in combination with PD1 inhibitors will likely further enhance therapeutic benefit in clinical trials. See related commentary by Molero-Glez et al., p. 3971.

CD137 (4-1BB) and T-Lymphocyte Exhaustion

CD137 (4-1BB) costimulation results in the potent activation of antitumor T lymphocytes and elicits antitumor efficacy that is synergistic with anti-PD(L)1 checkpoint inhibitors, especially when using bispecific constructs. Emerging experimental evidence indicates that 4-1BB ligation prevents and may revert T-cell exhaustion. See related article by Jeon et al., p. 4155.

Reversal of T-cell exhaustion: Mechanisms and synergistic approaches

T cells suffer from long-term antigen stimulation and insufficient energy supply, leading to a decline in their effector functions, memory capabilities, and proliferative capacity, ultimately resulting in T cell exhaustion and an inability to perform normal immune functions in the tumor microenvironment. Therefore, exploring how to restore these exhausted T cells to a state with effector functions is of great significance. Exhausted T cells exhibit a spectrum of molecular alterations, such as heightened expression of inhibitory receptors, shifts in transcription factor profiles, and modifications across epigenetic, metabolic, and transcriptional landscapes. This review provides a comprehensive overview of various strategies to reverse T cell exhaustion, including immune checkpoint blockade, and explores the potential synergistic effects of combining multiple approaches to reverse T cell exhaustion. It offers new insights and methods for achieving more durable and effective reversal of T cell exhaustion.

Short-term cultured tumor fragments to study immunotherapy combinations based on CD137 (4-1BB) agonism

Biomarkers for cancer immunotherapy are an unmet medical need. The group of Daniela Thommen at the NKI recently reported on novel methodologies based on short-term cultures of patient-derived tumor fragments whose cytokine concentrations in the supernatants and activation markers on infiltrating T cells were associated with clinical response to PD-1 blockade. We set up a similar culture technology with tumor-derived fragments using mouse tumors transplanted into syngeneic immunocompetent mice to test an agonist anti-CD137 mAb and its combinations with anti-PD-1 and/or anti-TGF-β. Increases in IFNγ concentrations in the tissue culture supernatants were detected upon in-culture activation with the anti-CD137 and anti-PD-1 mAb combinations or concanavalin A as a positive control. No other cytokine from a wide array was informative of stimulation with these mAbs. Interestingly, increases in Ki67 and other activation markers were substantiated in lymphocytes from cell suspensions gathered at the end of 72 h cultures. In mice bearing bilateral tumors in which one was excised prior to in vivo anti-CD137 + anti-PD-1 treatment to perform the fragment culture evaluation, no association was found between IFNγ production from the fragments and the in vivo therapeutic outcome in the non-resected contralateral tumors. The experimental system permitted freezing and thawing of the fragments with similar functional outcomes. Using a series of patient-derived tumor fragments from excised solid malignancies, we showed IFNγ production in a fraction of the studied cases, that was conserved in frozen/thawed fragments. The small tumor fragment culture technique seems suitable to preclinically explore immunotherapy combinations.

Bispecific and multispecific antibodies in oncology: opportunities and challenges

Research into bispecific antibodies, which are designed to simultaneously bind two antigens or epitopes, has advanced enormously over the past two decades. Owing to advances in protein engineering technologies and considerable preclinical research efforts, bispecific antibodies are constantly being developed and optimized to improve their efficacy and to mitigate toxicity. To date, >200 of these agents, the majority of which are bispecific immune cell engagers, are in either preclinical or clinical evaluation. In this Review, we discuss the role of bispecific antibodies in patients with cancer, including history and development, as well as innovative targeting strategies, clinical applications, and adverse events. We also discuss novel alternative bispecific antibody constructs, such as those targeting two antigens expressed by tumour cells or cells located in the tumour microenvironment. Finally, we consider future research directions in this rapidly evolving field, including innovative antibody engineering strategies, which might enable more effective delivery, overcome resistance, and thus optimize clinical outcomes.

Efficacy and safety of anti-PD-1/PD-L1-based dual immunotherapies versus PD-1/PD-L1 inhibitor alone in patients with advanced solid tumor: a systematic review and meta-analysis

INTRODUCTION

Numerous randomized controlled trials (RCTs) have investigated PD-1/PD-L1 inhibitor-based combination therapies. The debate surrounding the potential additive clinical benefits of combination of two immune-oncology (IO) therapies for cancer patients persists.

METHODS

Both published and grey sources of randomized clinical trials that compared anti-PD-1/PD-L1-based immunotherapy combinations with monotherapy in patients with advanced or metastatic solid tumors were encompassed. The primary outcome was progression-free survival (PFS), and secondary outcomes included objective response rate (ORR), overall survival (OS) and treatment-related adverse events (TRAEs).

RESULTS

Our analysis encompassed 31 studies comprising 10,341 patients, which covered 12 distinct immune-oncology combination regimens. Across all patients, the immunotherapy combinations exhibited the capability to enhance the ORR (OR = 1.23 [95% CI 1.13-1.34]) and extend PFS (HR = 0.91 [95% CI 0.87-0.95]). However, the observed enhancement in OS (HR = 0.96 [95% CI 0.91-1.01]) was of no significance. Greater benefits in terms of PFS (HR = 0.82 [95% CI 0.72 to 0.93]) and OS (HR = 0.85 [95% CI 0.73 to 0.99]) may be particularly pronounced in cases where PD-L1 expression is negative. Notably, despite a heightened risk of any-grade TRAEs (OR = 1.72 [95% CI 1.40-2.11]) and grade greater than or equal to 3 TRAEs (OR = 2.01 [95% CI 1.67-2.43]), toxicity was generally manageable.

CONCLUSIONS

This study suggests that incorporating an additional immunotherapy agent with PD-1/PD-L1 inhibitors can elevate the response rate and reduce the risk of disease progression, all while maintaining manageable toxicity. However, there remains a challenge in translating these primary clinical benefits into extended overall survival.

Advances in nano-immunotherapy for hematological malignancies

Hematological malignancies (HMs) encompass a diverse group of blood neoplasms with significant morbidity and mortality. Immunotherapy has emerged as a validated and crucial treatment modality for patients with HMs. Despite notable advancements having been made in understanding and implementing immunotherapy for HMs over the past decade, several challenges persist. These challenges include immune-related adverse effects, the precise biodistribution and elimination of therapeutic antigens in vivo, immune tolerance of tumors, and immune evasion by tumor cells within the tumor microenvironment (TME). Nanotechnology, with its capacity to manipulate material properties at the nanometer scale, has the potential to tackle these obstacles and revolutionize treatment outcomes by improving various aspects such as drug targeting and stability. The convergence of nanotechnology and immunotherapy has given rise to nano-immunotherapy, a specialized branch of anti-tumor therapy. Nanotechnology has found applications in chimeric antigen receptor T cell (CAR-T) therapy, cancer vaccines, immune checkpoint inhibitors, and other immunotherapeutic strategies for HMs. In this review, we delineate recent developments and discuss current challenges in the field of nano-immunotherapy for HMs, offering novel insights into the potential of nanotechnology-based therapeutic approaches for these diseases.

ATG-101 Is a Tetravalent PD-L1×4-1BB Bispecific Antibody That Stimulates Antitumor Immunity through PD-L1 Blockade and PD-L1-Directed 4-1BB Activation

Immune checkpoint inhibitors (ICI) have transformed cancer treatment. However, only a minority of patients achieve a profound response. Many patients are innately resistant while others acquire resistance to ICIs. Furthermore, hepatotoxicity and suboptimal efficacy have hampered the clinical development of agonists of 4-1BB, a promising immune-stimulating target. To effectively target 4-1BB and treat diseases resistant to ICIs, we engineered ATG-101, a tetravalent "2+2″ PD-L1×4-1BB bispecific antibody. ATG-101 bound PD-L1 and 4-1BB concurrently, with a greater affinity for PD-L1, and potently activated 4-1BB+ T cells when cross-linked with PD-L1-positive cells. ATG-101 activated exhausted T cells upon PD-L1 binding, indicating a possible role in reversing T-cell dysfunction. ATG-101 displayed potent antitumor activity in numerous in vivo tumor models, including those resistant or refractory to ICIs. ATG-101 greatly increased the proliferation of CD8+ T cells, the infiltration of effector memory T cells, and the ratio of CD8+ T/regulatory T cells in the tumor microenvironment (TME), rendering an immunologically "cold" tumor "hot." Comprehensive characterization of the TME after ATG-101 treatment using single-cell RNA sequencing further revealed an altered immune landscape that reflected increased antitumor immunity. ATG-101 was well tolerated and did not induce hepatotoxicity in non-human primates. According to computational semimechanistic pharmacology modeling, 4-1BB/ATG-101/PD-L1 trimer formation and PD-L1 receptor occupancy were both maximized at around 2 mg/kg of ATG-101, providing guidance regarding the optimal biological dose for clinical trials. In summary, by localizing to PD-L1-rich microenvironments and activating 4-1BB+ immune cells in a PD-L1 cross-linking-dependent manner, ATG-101 safely inhibits growth of ICI resistant and refractory tumors.

SIGNIFICANCE

The tetravalent PD-L1×4-1BB bispecific antibody ATG-101 activates 4-1BB+ T cells in a PD-L1 cross-linking-dependent manner, minimizing the hepatotoxicity of existing 4-1BB agonists and suppressing growth of ICI-resistant tumors. See related commentary by Ha et al., p. 1546.

Striking the Balance with a PD-L1×4-1BB Bispecific Antibody

Antibody-based immune checkpoint blockade therapy has revolutionized the field of cancer immunotherapy, yet its efficacy remains limited in immunologically cold tumors. Combining checkpoint inhibitors with costimulatory agonists improves tumoricidal activity of T cells but also can lead to off-target hepatotoxicity. Although bispecific antibodies confer tumor selectivity to alleviate undesirable adverse effects, toxicity concerns persist with increased dosing. In this issue of Cancer Research, Yuwen and colleagues introduce ATG-101, a tetravalent PD-L1×4-1BB bispecific antibody with high programmed death ligand 1 (PD-L1) affinity and low 4-1BB affinity, aiming to mitigate hepatotoxicity. ATG-101 demonstrates PD-L1-dependent 4-1BB activation, leading to selective T-cell activation within the tumor microenvironment. ATG-101 exhibits potent antitumor activity, even in large, immunologically cold, and monotherapy-resistant tumor models. Single-cell RNA sequencing reveals significant shifts of immune cell populations in the tumor microenvironment from protumor to antitumor phenotypes following ATG-101 treatment. In cynomolgus monkeys, no serious cytokine storm and hepatotoxicity are observed after ATG-101 treatment, indicating a broad therapeutic window for ATG-101 in cancer treatment. This study highlights the potential of tetravalent bispecific antibodies in cancer immunotherapy, with implications for various antibody-based treatment modalities across different fields. See related article by Yuwen et al., p. 1680.

Agonist Antibodies for Cancer Immunotherapy: History, Hopes, and Challenges

Immunotherapy is among the most promising new treatment modalities to arise over the last two decades; antibody drugs are delivering immunotherapy to millions of patients with many different types of cancer. Initial success with antibody therapeutics came in the form of direct targeting or cytotoxic antibodies, such as rituximab and trastuzumab, which bind directly to tumor cells to elicit their destruction. These were followed by immunomodulatory antibodies that elicit antitumor responses by either stimulating immune cells or relieving tumor-mediated suppression. By far the most successful approach in the clinic to date has been relieving immune suppression, with immune checkpoint blockade now a standard approach in the treatment of many cancer types. Despite equivalent and sometimes even more impressive effects in preclinical models, agonist antibodies designed to stimulate the immune system have lagged behind in their clinical translation. In this review, we document the main receptors that have been targeted by agonist antibodies, consider the various approaches that have been evaluated to date, detail what we have learned, and consider how their anticancer potential can be unlocked.

When will the immune-stimulating antibody conjugates (ISACs) be transferred from bench to bedside?

Immunostimulatory antibody conjugates (ISACs) as a promising new generation of targeted therapeutic antibody-drug conjugates (ADCs), that not only activate innate immunity but also stimulate adaptive immunity, providing a dual therapeutic effect to eliminate tumor cells. However, several ISACs are still in the early stages of clinical development or have already failed. Therefore, it is crucial to design ISACs more effectively to overcome their limitations, including high toxicity, strong immunogenicity, long development time, and poor pharmacokinetics. This review aims to summarize the composition and function of ISACs, incorporating current design considerations and ongoing clinical trials. Additionally, the review delves into the current issues with ISACs and potential solutions, such as adjusting the drug-antibody ratio (DAR) to improve the bioavailability of ISACs. By leveraging the affinity and bioavailability-enhancing properties of bispecific antibodies, the utility between antibodies and immunostimulatory agents can be balanced. Commonly used immunostimulatory agents may induce systemic immune reactions, and BTK (Bruton's tyrosine kinase) inhibitors can regulate immunogenicity. Finally, the concept of grafting ADC's therapeutic principles is simple, but the combination of payload, linker, and targeted functional molecules is not a simple permutation and combination problem. The development of conjugate drugs faces more complex pharmacological and toxicological issues. Standing on the shoulders of ADC, the development and application scenarios of ISAC are endowed with broader space.

Characterization of a Trispecific PD-L1 Blocking Antibody That Exhibits EGFR-Conditional 4-1BB Agonist Activity

Immune checkpoint blockade has changed the treatment paradigm for advanced solid tumors, but the overall response rates are still limited. The combination of checkpoint blockade with anti-4-1BB antibodies to stimulate tumor-infiltrating T cells has shown anti-tumor activity in human trials. However, the further clinical development of these antibodies has been hampered by significant off-tumor toxicities. Here, we generated an anti-4-1BB/EGFR/PD-L1 trispecific antibody consisting of a triple-targeting tandem trimerbody (TT) fused to an engineered silent Fc region. This antibody (IgTT-4E1-S) was designed to combine the blockade of the PD-L1/PD-1 axis with conditional 4-1BB costimulation specifically confined to the tumor microenvironment (TME). The antibody demonstrated simultaneous binding to purified EGFR, PD-L1, and 4-1BB in solution, effective blockade of the PD-L1/PD1 interaction, and potent 4-1BB-mediated costimulation, but only in the presence of EGFR-expressing cells. These results demonstrate the feasibility of IgTT-4E1-S specifically blocking the PD-L1/PD-1 axis and inducing EGFR-conditional 4-1BB agonist activity.

CB307: A Dual Targeting Costimulatory Humabody VH Therapeutic for Treating PSMA-Positive Tumors

PURPOSE

CD137 is a T- and NK-cell costimulatory receptor involved in consolidating immunologic responses. The potent CD137 agonist urelumab has shown clinical promise as a cancer immunotherapeutic but development has been hampered by on-target off-tumor toxicities. A CD137 agonist targeted to the prostate-specific membrane antigen (PSMA), frequently and highly expressed on castration-resistant metastatic prostate cancer (mCRPC) tumor cells, could bring effective immunotherapy to this immunologically challenging to address disease.

EXPERIMENTAL DESIGN

We designed and manufactured CB307, a novel half-life extended bispecific costimulatory Humabody VH therapeutic to elicit CD137 agonism exclusively in a PSMA-high tumor microenvironment (TME). The functional activity of CB307 was assessed in cell-based assays and in syngeneic mouse antitumor pharmacology studies. Nonclinical toxicology and toxicokinetic properties of CB307 were assessed in a good laboratory practice (GLP) compliant study in cynomolgus macaques.

RESULTS

CB307 provides effective CD137 agonism in a PSMA-dependent manner, with antitumor activity both in vitro and in vivo, and additional activity when combined with checkpoint inhibitors. A validated novel PSMA/CD137 IHC assay demonstrated a higher prevalence of CD137-positive cells in the PSMA-expressing human mCRPC TME with respect to primary lesions. CB307 did not show substantial toxicity in nonhuman primates and exhibited a plasma half-life supporting weekly clinical administration.

CONCLUSIONS

CB307 is a first-in-class immunotherapeutic that triggers potent PSMA-dependent T-cell activation, thereby alleviating toxicologic concerns against unrestricted CD137 agonism.

The enhanced antitumor activity of bispecific antibody targeting PD-1/PD-L1 signaling

The programmed cell death 1 (PD-1) signaling pathway, a key player in immune checkpoint regulation, has become a focal point in cancer immunotherapy. In the context of cancer, upregulated PD-L1 on tumor cells can result in T cell exhaustion and immune evasion, fostering tumor progression. The advent of PD-1/PD-L1 inhibitor has demonstrated clinical success by unleashing T cells from exhaustion. Nevertheless, challenges such as resistance and adverse effects have spurred the exploration of innovative strategies, with bispecific antibodies (BsAbs) emerging as a promising frontier. BsAbs offer a multifaceted approach to cancer immunotherapy by simultaneously targeting PD-L1 and other immune regulatory molecules. We focus on recent advancements in PD-1/PD-L1 therapy with a particular emphasis on the development and potential of BsAbs, especially in the context of solid tumors. Various BsAb products targeting PD-1 signaling are discussed, highlighting their unique mechanisms of action and therapeutic potential. Noteworthy examples include anti-TGFβ × PD-L1, anti-CD47 × PD-L1, anti-VEGF × PD-L1, anti-4-1BB × PD-L1, anti-LAG-3 × PD-L1, and anti-PD-1 × CTLA-4 BsAbs. Besides, we summarize ongoing clinical studies evaluating the efficacy and safety of these innovative BsAb agents. By unraveling the intricacies of the tumor microenvironment and harnessing the synergistic effects of anti-PD-1/PD-L1 BsAbs, there exists the potential to elevate the precision and efficacy of cancer immunotherapy, ultimately enabling the development of personalized treatment strategies tailored to individual patient profiles.

CD8+ T cell priming that is required for curative intratumorally anchored anti-4-1BB immunotherapy is constrained by Tregs

Although co-stimulation of T cells with agonist antibodies targeting 4-1BB (CD137) improves antitumor immune responses in preclinical studies, clinical success has been limited by on-target, off-tumor activity. Here, we report the development of a tumor-anchored ɑ4-1BB agonist (ɑ4-1BB-LAIR), which consists of a ɑ4-1BB antibody fused to the collagen-binding protein LAIR. While combination treatment with an antitumor antibody (TA99) shows only modest efficacy, simultaneous depletion of CD4+ T cells boosts cure rates to over 90% of mice. Mechanistically, this synergy depends on ɑCD4 eliminating tumor draining lymph node regulatory T cells, resulting in priming and activation of CD8+ T cells which then infiltrate the tumor microenvironment. The cytotoxic program of these newly primed CD8+ T cells is then supported by the combined effect of TA99 and ɑ4-1BB-LAIR. The combination of TA99 and ɑ4-1BB-LAIR with a clinically approved ɑCTLA-4 antibody known for enhancing T cell priming results in equivalent cure rates, which validates the mechanistic principle, while the addition of ɑCTLA-4 also generates robust immunological memory against secondary tumor rechallenge. Thus, our study establishes the proof of principle for a clinically translatable cancer immunotherapy.

Preclinical characterization and phase 1 results of ADG106 in patients with advanced solid tumors and non-Hodgkin's lymphoma

ADG106, a ligand-blocking agonistic antibody targeting CD137 (4-1BB), exhibits promising results in preclinical studies, demonstrating tumor suppression in various animal models and showing a balanced profile between safety and efficacy. This phase 1 study enrolls 62 patients with advanced malignancies, revealing favorable tolerability up to the 5.0 mg/kg dose level. Dose-limiting toxicity occurs in only one patient (6.3%) at 10.0 mg/kg, resulting in grade 4 neutropenia. The most frequent treatment-related adverse events include leukopenia (22.6%), neutropenia (22.6%), elevated alanine aminotransferase (22.6%), rash (21.0%), itching (17.7%), and elevated aspartate aminotransferase (17.7%). The overall disease control rates are 47.1% for advanced solid tumors and 54.5% for non-Hodgkin's lymphoma. Circulating biomarkers suggest target engagement by ADG106 and immune modulation of circulating T, B, and natural killer cells and cytokines interferon γ and interleukin-6, which may affect the probability of clinical efficacy. ADG106 has a manageable safety profile and preliminary anti-tumor efficacy in patients with advanced cancers (this study was registered at ClinicalTrials.gov: NCT03802955).

From glioma gloom to immune bloom: unveiling novel immunotherapeutic paradigms-a review

In tumor therapeutics, the transition from conventional cytotoxic drugs to targeted molecular therapies, such as those targeting receptor tyrosine kinases, has been pivotal. Despite this progress, the clinical outcomes have remained modest, with glioblastoma patients' median survival stagnating at less than 15 months. This underscores the urgent need for more specialized treatment strategies. Our review delves into the progression toward immunomodulation in glioma treatment. We dissect critical discoveries in immunotherapy, such as spotlighting the instrumental role of tumor-associated macrophages, which account for approximately half of the immune cells in the glioma microenvironment, and myeloid-derived suppressor cells. The complex interplay between tumor cells and the immune microenvironment has been explored, revealing novel therapeutic targets. The uniqueness of our review is its exhaustive approach, synthesizing current research to elucidate the intricate roles of various molecules and receptors within the glioma microenvironment. This comprehensive synthesis not only maps the current landscape but also provides a blueprint for refining immunotherapy for glioma, signifying a paradigm shift toward leveraging immune mechanisms for improved patient prognosis.

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.

A model-based approach leveraging in vitro data to support dose selection from the outset: A framework for bispecific antibodies in immuno-oncology

FAP-4-1BBL is a bispecific antibody exerting 4-1BB-associated T-cell activation only while simultaneously bound to the fibroblast activation protein (FAP) receptor, expressed on the surface of cancer-associated fibroblasts. The trimeric complex formed when FAP-4-1BBL is simultaneously bound to FAP and 4-1BB represents a promising mechanism to achieve tumor-specific 4-1BB stimulation. We integrated in vitro data with mathematical modeling to characterize the pharmacology of FAP-4-1BBL as a function of trimeric complex formation when combined with the T-cell engager cibisatamab. This relationship was used to prospectively predict a range of clinical doses where trimeric complex formation is expected to be at its maximum. Depending on the dosing schedule and FAP-4-1BBL plasma: tumor distribution, doses between 2 and 145 mg could lead to maximum trimeric complex formation in the clinic. Due to the expected variability in both pharmacokinetic and FAP expression in the patient population, we predict that detecting a clear dose-response relationship would remain difficult without a large number of patients per dose level, highlighting that mathematical modeling techniques based on in vitro data could aid dose selection.

Integrated analysis of phase 1a and 1b randomized controlled trials; Treg-targeted cancer immunotherapy with the humanized anti-CCR4 antibody, KW-0761, for advanced solid tumors

INTRODUCTION

Regulatory T cells (Tregs) have attracted attention as a novel therapeutic target to augment the clinical efficacy of immunotherapy. We conducted phase Ia and Ib trials to examine the safety and efficacy of the anti-CCR4 antibody, KW-0761 (mogamulizumab), which may eliminate effector Tregs (eTregs). We herein overviewed the results of these trials, presented cases with a durable clinical response, and investigated factors associated with the clinical effects of KW-0761.

METHODS

Forty-nine patients with CCR4-negative solid cancers were enrolled in the phase Ia and Ib trials on KW-0761. An integral analysis of safety, clinical responses, prognosis, blood laboratory data, and cancer testis antigen-specific immune responses was performed.

RESULTS

Grade 3-4 treatment-related adverse events were reported in 21 (42.9%) out of 49 patients, all of which were manageable. A partial response and stable disease were observed in 1 and 9 patients, respectively. A durable clinical response was noted in 2 esophageal and 2 lung cancer patients. eTreg depletion in peripheral blood was confirmed in most patients, and eTreg depletion was sustained during the KW-0761 treatment. High lymphocyte levels at baseline and 2 weeks after the initiation of KW-0761 were associated with a favorable clinical outcome.

CONCLUSIONS

A durable clinical response was noted in some patients, and high lymphocyte levels before treatment initiation may be a biomarker for the efficacy of KW-0761. The synergistic effect of KW-0761 for depleting Tregs and other immunotherapies is expected in the future.

Reconciling intrinsic properties of activating TNF receptors by native ligands versus synthetic agonists

The extracellular domain of tumor necrosis factor receptors (TNFR) generally require assembly into a homotrimeric quaternary structure as a prerequisite for initiation of signaling via the cytoplasmic domains. TNF receptor homotrimers are natively activated by similarly homo-trimerized TNF ligands, but can also be activated by synthetic agonists including engineered antibodies and Fc-ligand fusion proteins. A large body of literature from pre-clinical models supports the hypothesis that synthetic agonists targeting a diverse range of TNF receptors (including 4-1BB, CD40, OX40, GITR, DR5, TNFRSF25, HVEM, LTβR, CD27, and CD30) could amplify immune responses to provide clinical benefit in patients with infectious diseases or cancer. Unfortunately, however, the pre-clinical attributes of synthetic TNF receptor agonists have not translated well in human clinical studies, and have instead raised fundamental questions regarding the intrinsic biology of TNF receptors. Clinical observations of bell-shaped dose response curves have led some to hypothesize that TNF receptor overstimulation is possible and can lead to anergy and/or activation induced cell death of target cells. Safety issues including liver toxicity and cytokine release syndrome have also been observed in humans, raising questions as to whether those toxicities are driven by overstimulation of the targeted TNF receptor, a non-TNF receptor related attribute of the synthetic agonist, or both. Together, these clinical findings have limited the development of many TNF receptor agonists, and may have prevented generation of clinical data which reflects the full potential of TNF receptor agonism. A number of recent studies have provided structural insights into how different TNF receptor agonists bind and cluster TNF receptors, and these insights aid in deconvoluting the intrinsic biology of TNF receptors with the mechanistic underpinnings of synthetic TNF receptor agonist therapeutics.

Intratumoral immunotherapy with mRNAs encoding chimeric protein constructs encompassing IL-12, CD137 agonists, and TGF-β antagonists

Intratumoral immunotherapy strategies for cancer based on interleukin-12 (IL-12)-encoding cDNA and mRNA are under clinical development in combination with anti-PD-(L)1 monoclonal antibodies. To make the most of these approaches, we have constructed chimeric mRNAs encoding single-chain IL-12 fused to single-chain fragment variable (scFv) antibodies that bind to transforming growth factor β (TGF-β) and CD137 (4-1BB). Several neutralizing TGF-β agents and CD137 agonists are also undergoing early-phase clinical trials. To attain TGF-β and CD137 binding by the constructions, we used bispecific tandem scFv antibodies (taFvs) derived from the specific 1D11 and 1D8 monoclonal antibodies (mAbs), respectively. Transfection of mRNAs encoding the chimeric constructs achieved functional expression of the proteins able to act on their targets. Upon mRNA intratumoral injections in the transplantable mouse cancer models CT26, MC38, and B16OVA, potent therapeutic effects were observed following repeated injections into the tumors. Efficacy was dependent on the number of CD8+ T cells able to recognize tumor antigens that infiltrated the malignant tissue. Although the abscopal effects on concomitant uninjected lesions were modest, such distant effects on untreated lesions were markedly increased when combined with systemic PD-1 blockade.

4-1BB Targeting Immunotherapy: Mechanism, Antibodies, and Chimeric Antigen Receptor T

4-1BB (CD137, TNFRSF9) is a type I transmembrane protein which binds its natural ligand, 4-1BBL. This interaction has been exploited to improve cancer immunotherapy. With ligand binding by 4-1BB, the nuclear factor-kappa B signaling pathway is activated, which results in transcription of corresponding genes such as interleukin-2 and interferon-γ, as well as the induction of T cell proliferation and antiapoptotic signals. Moreover, monoclonal antibodies that target-4-1BB, for example, Urelumab and Utomilumab, are widely used in the treatments of B cell non-Hodgkin lymphoma, lung cancer, breast cancer, soft tissue sarcoma, and other solid tumors. Furthermore, 4-1BB as a costimulatory domain, for chimeric antigen receptor T (CAR-T) cells, improves T cell proliferation and survival as well as reduces T cell exhaustion. As such, a deeper understanding of 4-1BB will contribute to improvements in cancer immunotherapy. This review provides a comprehensive analysis of current 4-1BB studies, with a focus on the use of targeting-4-1BB antibodies and 4-1BB activation domains in CAR-T cells for the treatment of cancer.

The screening, identification, design and clinical application of tumor-specific neoantigens for TCR-T cells

Recent advances in neoantigen research have accelerated the development of tumor immunotherapies, including adoptive cell therapies (ACTs), cancer vaccines and antibody-based therapies, particularly for solid tumors. With the development of next-generation sequencing and bioinformatics technology, the rapid identification and prediction of tumor-specific antigens (TSAs) has become possible. Compared with tumor-associated antigens (TAAs), highly immunogenic TSAs provide new targets for personalized tumor immunotherapy and can be used as prospective indicators for predicting tumor patient survival, prognosis, and immune checkpoint blockade response. Here, the identification and characterization of neoantigens and the clinical application of neoantigen-based TCR-T immunotherapy strategies are summarized, and the current status, inherent challenges, and clinical translational potential of these strategies are discussed.

CD137 (4-1BB) requires physically associated cIAPs for signal transduction and antitumor effects

CD137 (4-1BB) is a member of the TNFR family that mediates potent T cell costimulatory signals upon ligation by CD137L or agonist monoclonal antibodies (mAbs). CD137 agonists attain immunotherapeutic antitumor effects in cancer mouse models, and multiple agents of this kind are undergoing clinical trials. We show that cIAP1 and cIAP2 are physically associated with the CD137 signaling complex. Moreover, cIAPs are required for CD137 signaling toward the NF-κB and MAPK pathways and for costimulation of human and mouse T lymphocytes. Functional evidence was substantiated with SMAC mimetics that trigger cIAP degradation and by transfecting cIAP dominant-negative variants. Antitumor effects of agonist anti-CD137 mAbs are critically dependent on the integrity of cIAPs in cancer mouse models, and cIAPs are also required for signaling from CARs encompassing CD137's cytoplasmic tail.