Increase of PD-L1 expressing B-precursor ALL cells in a patient resistant to the CD19/CD3-bispecific T cell engager antibody blinatumomab

Treatment of Relapsed Acute Lymphocytic Leukemia in Adult Patients

OPINION STATEMENT

For adult patients diagnosed with relapsed B cell-ALL (B-ALL), there have been significant improvements in available treatment options following the FDA approval of novel cellular and immunotherapy approaches - blinatumomab, chimeric antigen receptor (CAR) T therapy, and inotuzumab. For the last several years, research has focused on gaining a better understanding of the effects of specific disease and patient characteristics on long-term outcomes with each of the FDA-approved agents. In combination with the better prevention and management of unique, treatment-specific toxicities, providers can now select the best available treatment option for each individual patient diagnosed with relapsed, adult B-ALL needing therapy. This has allowed more patients to proceed to consolidative hematopoietic stem cell transplant (HSCT), and long-term data has even brought into question the need for HSCT for long-term durable remission for all patients. However, with the adoption of blinatumomab, CAR T therapy, and inotuzumab in front-line treatment regimens, it remains unclear what effects this will have on patients with relapsed B-ALL following exposure to these novel cellular and immunotherapy therapies. Unlike B-ALL, similar advances have unfortunately not yet been realized in T cell-ALL (T-ALL). Currently, new therapeutic approaches are underway to utilize similar targeting strategies that have been successful in B-ALL - monoclonal antibodies, bispecific T-cell engagers (BiTE), and CAR T therapy. Like B-ALL, the only existing approved therapy for relapsed T-ALL, nelarabine, is now used in the upfront treatment setting potentially limiting its utility in relapsed disease. Over the next several years, the hope is for patients diagnosed with T-ALL to experience the drastic improvement in outcomes as has been seen for patients diagnosed with B-ALL over the last decade.

Facile Access to Branched Multispecific Proteins

Approaches that leverage orthogonal chemical reactions to generate protein-protein conjugates have expanded access to bespoke chimeras. Although the literature is replete with examples of the semisynthesis of bispecific proteins, few methods exist for the semisynthesis of protein conjugates of higher complexity (i.e., greater than two-protein fusions). The recent emergence of trispecific cell engagers for immune cell redirection therapies necessitates the development of chemical methods for the construction of trispecific proteins that would otherwise be inaccessible via natural protein synthesis. Here, we demonstrate that 3-bromo-5-methylene pyrrolone (3Br-5MP) can be used to effect the facile chemical synthesis of trispecific peptides and proteins with exquisite control over the addition of each monomer. The multimeric complexes maintain epitope functionality both in human cells and upon immobilization. We anticipate that facile access to trispecific proteins using this 3Br-5MP will have broad utility in basic science research and will quicken the pace of research to establish novel, multimeric immune cell redirection therapies.

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.

New immune cell engagers for cancer immunotherapy

There have been major advances in the immunotherapy of cancer in recent years, including the development of T cell engagers - antibodies engineered to redirect T cells to recognize and kill cancer cells - for the treatment of haematological malignancies. However, the field still faces several challenges to develop agents that are consistently effective in a majority of patients and cancer types, such as optimizing drug dose, overcoming treatment resistance and improving efficacy in solid tumours. A new generation of T cell-targeted molecules was developed to tackle these issues that are potentially more effective and safer. In addition, agents designed to engage the antitumour activities of other immune cells, including natural killer cells and myeloid cells, are showing promise and have the potential to treat a broader range of cancers.

Stepping forward: T-cell redirecting bispecific antibodies in cancer therapy

T cell-redirecting bispecific antibodies are specifically designed to bind to tumor-associated antigens, thereby engaging with CD3 on the T cell receptor. This linkage between tumor cells and T cells actively triggers T cell activation and initiates targeted killing of the identified tumor cells. These antibodies have emerged as one of the most promising avenues within tumor immunotherapy. However, despite success in treating hematological malignancies, significant advancements in solid tumors have yet to be explored. In this review, we aim to address the critical challenges associated with T cell-redirecting bispecific antibodies and explore novel strategies to overcome these obstacles, with the ultimate goal of expanding the application of this therapy to include solid tumors.

SOHO State of the Art Updates and Next Questions | Current Evidence and Future Directions for Bispecific Antibodies in Large B-Cell Lymphoma

The CD20xCD3 bispecific antibodies (bsAb) are "off-the-shelf" T-cell re-directing therapies that demonstrate remarkable single-agent clinical activity in B-cell lymphomas. Two agents, epcoritamab (epcor) and glofitamab (glofit) have recent global approvals for patients with relapsed/refractory DLBCL (RR DLBCL) following 2 prior treatment lines. Both agents demonstrate activity in patients with prior exposure to chimeric antigen receptor T-cell (CAR-T) treatment. As multiyear follow-up data become available, it is clear that the majority of patients achieving complete remissions do not relapse and that outcomes are similar between epcor and glofit. CD20xCD3 bsAb have a safety profile that reflect their mechanism of action, with cytokine release syndrome (CRS) the key management issue. Neurotoxicity is far less common than observed with CD19-directed CAR-T. BsAbs are attractive, rapidly available, treatment options for patients with RR DLBCL, without the practical and financial challenges seen with autologous CAR-T therapies. Recent data also demonstrate the feasibility and potential efficacy of bsAb in combination with chemoimmunotherapy with large randomized trials evaluating bsAb-chemotherapy combinations underway. There are open questions about the future role of bsAB for LBCL, the optimal duration of therapy, optimal CRS risk mitigation strategies, and potential resistance mechanisms. In this review we seek to describe the current evidence for bsAb in LBCL, and offer opinion regarding these open questions.

Pentraxin 3: A Main Driver of Inflammation and Immune System Dysfunction in the Tumor Microenvironment of Glioblastoma

Brain tumors are a heterogeneous group of brain neoplasms that are highly prevalent in individuals of all ages worldwide. Within this pathological framework, the most prevalent and aggressive type of primary brain tumor is glioblastoma (GB), a subtype of glioma that falls within the IV-grade astrocytoma group. The death rate for patients with GB remains high, occurring within a few months after diagnosis, even with the gold-standard therapies now available, such as surgery, radiation, or a pharmaceutical approach with Temozolomide. For this reason, it is crucial to continue looking for cutting-edge therapeutic options to raise patients' survival chances. Pentraxin 3 (PTX3) is a multifunctional protein that has a variety of regulatory roles in inflammatory processes related to extracellular matrix (ECM). An increase in PTX3 blood levels is considered a trustworthy factor associated with the beginning of inflammation. Moreover, scientific evidence suggested that PTX3 is a sensitive and earlier inflammation-related marker compared to the short pentraxin C-reactive protein (CRP). In several tumoral subtypes, via regulating complement-dependent and macrophage-associated tumor-promoting inflammation, it has been demonstrated that PTX3 may function as a promoter of cancer metastasis, invasion, and stemness. Our review aims to deeply evaluate the function of PTX3 in the pathological context of GB, considering its pivotal biological activities and its possible role as a molecular target for future therapies.

T-Cell Engagers-The Structure and Functional Principle and Application in Hematological Malignancies

Recent advancements in cancer immunotherapy have made directing the cellular immune response onto cancer cells a promising strategy for the treatment of hematological malignancies. The introduction of monoclonal antibody-based (mAbs) targeted therapy has significantly improved the prognosis for hematological patients. Facing the issues of mAb-based therapies, a novel bispecific antibody (BsAb) format was developed. T-cell engagers (TCEs) are BsAbs, which simultaneously target tumor-associated antigens on tumor cells and CD3 molecules present on T-cells. This mechanism allows for the direct activation of T-cells and their anti-tumor features, ultimately resulting in the lysis of tumor cells. In 2014, the FDA approved blinatumomab, a TCE directed to CD3 and CD19 for treatment of acute lymphoblastic leukemia. Since then, numerous TCEs have been developed, allowing for treating different hematological malignancies such as acute myeloid leukemia, multiple myeloma, and non-Hodgkin lymphoma and Hodgkin lymphoma. As of November 2023, seven clinically approved TCE therapies are on the market. TCE-based therapies still have their limitations; however, improving the properties of TCEs, as well as combining TCE-based therapies with other forms of treatment, give hope to find the cures for currently terminal diseases. In this paper, we summarized the technical basis of the TCE technology, its application in hematology, and its current issues and prospects.

Induction of complementary immunogenic necroptosis and apoptosis cell death pathways inhibits cancer metastasis and relapse

Interactions of light-sensitive drugs and materials with Cerenkov radiation-emitting radiopharmaceuticals generate cytotoxic reactive oxygen species (ROS) to inhibit localized and disseminated cancer progression, but the cell death mechanisms underlying this radionuclide stimulated dynamic therapy (RaST) remain elusive. Using ROS-regenerative nanophotosensitizers coated with a tumor-targeting transferrin-titanocene complex (TiO2-TC-Tf) and radiolabeled 2-fluorodeoxyglucose (18FDG), we found that adherent dying cells maintained metabolic activity with increased membrane permeabilization. Mechanistic assessment of these cells revealed that RaST activated the expression of RIPK-1 and RIPK-3, which mediate necroptosis cell death. Subsequent recruitment of the nuclear factors kappa B and the executioner mixed lineage kinase domain-like pseudo kinase (MLKL) triggered plasma membrane permeabilization and pore formation, respectively, followed by the release of cytokines and immunogenic damage-associated molecular patterns (DAMPs). In immune-deficient breast cancer models with adequate stroma and growth factors that recapitulate the human tumor microenvironment, RaST failed to inhibit tumor progression and the ensuing lung metastasis. A similar aggressive tumor model in immunocompetent mice responded to RaST, achieving a remarkable partial response (PR) and complete response (CR) with no evidence of lung metastasis, suggesting active immune system engagement. RaST recruited antitumor CD11b+, CD11c+, and CD8b+ effector immune cells after initiating dual immunogenic apoptosis and necroptosis cell death pathways in responding tumors in vivo. Over time, cancer cells upregulated the expression of negative immune regulating cytokine (TGF-β) and soluble immune checkpoints (sICP) to challenge RaST effect in the CR mice. Using a signal-amplifying cancer-imaging agent, LS301, we identified latent minimal residual disseminated tumors in the lymph nodes (LNs) of the CR group. Despite increased protumor immunogens in the CR mice, RaST prevented cancer relapse and metastasis through dynamic redistribution of ROS-regenerative TiO2 from bones at the early treatment stage to the spleen and LNs, maintaining active immunity against cancer progression and migration. This study reveals the immune-mechanistic underpinnings of RaST-mediated antitumor immune response and highlights immunogenic reprogramming of tumors in response to RaST. Overcoming apoptosis resistance through complementary necroptosis activation paves the way for strategic drug combinations to improve cancer treatment.

Predictive Panel for Immunotherapy in Low-Grade Glioma

BACKGROUND

The main treatment of low-grade glioma (LGG) is still surgical resection followed by radiotherapy and/or chemotherapy, which has certain limitations, including side effects and drug resistance. Immunotherapy is a promising treatment for LGG, but it is generally hindered by the tumor microenvironment with the limited expression of tumor antigens.

METHODS

We integrated RNA sequencing data sets and clinical information and conducted consistent cluster analysis to explore the most suitable patients for immune checkpoint therapy. Gene set enrichment analysis, UMAP analysis, mutation correlation analysis, TIMER analysis, and TIDE analysis were used to identify the immune characteristics of 3 immune subtypes and the feasibility of 5 antigens as immune checkpoint markers.

RESULTS

We analyzed the isolation and mutation of homologous recombination repair genes (HRR) of the 3 immune subtypes, and the HRR genes of the 3 subtypes were obviously segregated. Among them, the IS2 subtype has a large number of HRR gene mutations, which increases the immunogenicity of tumors-this is consistent with the results of tumor mutation load analysis of 3 immune subtypes. Then we evaluated the immune cell infiltration of immune subtypes and found that IS2 and IS3 subtypes were rich in immune cells. It is worth noting that there are many Treg cells and NK cells in the IS1 subtype. In addition, when analyzing the immune checkpoint gene expression of the 3 subtypes, we found that they were upregulated most in IS2 subtypes compared with other subtypes. Then when we further confirmed the role of immune-related genes in LGG; through TIDE analysis and TISIDB analysis, we obtained 5 markers that can predict the efficacy of ICB in patients with LGG. In addition, we confirmed that they were associated with poor prognosis through survival analysis.

CONCLUSIONS

We obtained 3 reliable immune subtypes, and patients with the IS2 subtype are suitable for immunotherapy, in which NAMPT, SLC11A1, TNC, VIM, and SPP1 are predictive panel markers for ICB in the LGG group. Our findings provide a rationale for immunotherapy selection and prediction of patient prognosis in LGG patients.

Revolutionizing cancer treatment: the power of bi- and tri-specific T-cell engagers in oncolytic virotherapy

Bi- or tri-specific T cell engagers (BiTE or TriTE) are recombinant bispecific proteins designed to stimulate T-cell immunity directly, bypassing antigen presentation by antigen-presenting cells (APCs). However, these molecules suffer from limitations such as short biological half-life and poor residence time in the tumor microenvironment (TME). Fortunately, these challenges can be overcome when combined with OVs. Various strategies have been developed, such as encoding secretory BiTEs within OV vectors, resulting in improved targeting and activation of T cells, secretion of key cytokines, and bystander killing of tumor cells. Additionally, oncolytic viruses armed with BiTEs have shown promising outcomes in enhancing major histocompatibility complex I antigen (MHC-I) presentation, T-cell proliferation, activation, and cytotoxicity against tumor cells. These combined approaches address tumor heterogeneity, drug delivery, and T-cell infiltration, offering a comprehensive and effective solution. This review article aims to provide a comprehensive overview of Bi- or TriTEs and OVs as promising therapeutic approaches in the field of cancer treatment. We summarize the cutting-edge advancements in oncolytic virotherapy immune-related genetic engineering, focusing on the innovative combination of BiTE or TriTE with OVs.

Contribution of the TIME in BCP-ALL: the basis for novel approaches therapeutics

The bone marrow (BM) niche is a microenvironment where both immune and non-immune cells functionally interact with hematopoietic stem cells (HSC) and more differentiated progenitors, contributing to the regulation of hematopoiesis. It is regulated by various signaling molecules such as cytokines, chemokines, and adhesion molecules in its microenvironment. However, despite the strict regulation of BM signals to maintain their steady state, accumulating evidence in B-cell precursor acute lymphoblastic leukemia (BCP-ALL) indicates that leukemic cells can disrupt the physiological hematopoietic niche in the BM, creating a new leukemia-supportive microenvironment. This environment favors immunological evasion mechanisms and the interaction of these cells with the development and progression of BCP-ALL. With a growing understanding of the tumor immune microenvironment (TIME) in the development and progression of BCP-ALL, current strategies focused on "re-editing" TIME to promote antitumor immunity have been developed. In this review, we summarize how TIME cells are disrupted by the presence of leukemic cells, evading immunosurveillance mechanisms in the BCP-ALL model. We also explore the crosstalk between TIME and leukemic cells that leads to treatment resistance, along with the most promising immuno-therapy strategies. Understanding and further research into the role of the BM microenvironment in leukemia progression and relapse are crucial for developing more effective treatments and reducing patient mortality.

Anti-PD-L1 × anti-CD3 bispecific T-cell engager-armed T cells can overcome immunosuppression and redirect T cells to kill breast cancer cells expressing PD-L1

T cell-based immunotherapy has transformed cancer treatment. Nonetheless, T cell antitumor activity can be inhibited by an immune checkpoint molecule expressed on cancer cells, program death ligand 1 (PD-L1), which interacts with the PD-1 on T cells. We generated αPD-L1 × αCD3 bispecific T-cell engager-armed T cells (BATs) to prevent PD-L1/PD-1 interaction and hence to redirect T cells to kill cancer cells. αPD-L1 × αCD3 bispecific T-cell engagers (BTEs) were produced from Chinese hamster ovary (CHO) cells to arm human primary T cells. Flow cytometry was used to investigate BTE binding to BATs. The cytotoxicity of BATs against PD-L1-expressing breast cancer (BC) cell lines was assessed in 2-dimensional (2D) and 3-dimensional (3D) culture models. The binding stability of BTE on BATs and their efficacy after cryopreservation were also examined. The CHO cell BTE expression yield was 3.34 mg/ml. The binding ability on T cells reached 91.02 ± 4.2 %. BATs specifically lysed PD-L1-expressing BC cells, with 56.4 ± 15.3 % HCC70 cells and 70.67 ± 15.6 % MDA-MB-231 cells lysed at a 10:1 effector-to-target ratio. BATs showed slight, nonsignificant lysis of PD-L1-negative BC cells, MCF-7, and T47D. Moreover, BATs significantly disrupted MDA-MB-231 3D spheroids expressing PD-L1 after 48 and 72 h of coculture. Cryopreserved BATs maintained BTE binding stability, cell viability, and anticancer activity, comparable to fresh BATs. αPD-L1 × αCD3 BATs induced the cytolysis of PD-L1-expressing BC cells in 2D and 3D coculture assays. BATs can be prepared and preserved, facilitating their use and transportation. This study demonstrates the potential of αPD-L1 × αCD3 BATs in treating cancers with positive PD-L1 expression.

Longitudinal evaluation of the biodistribution and cellular internalization of the bispecific CD3xTRP1 antibody in syngeneic mouse tumor models

BACKGROUND

CD3 bispecific antibodies (CD3-bsAbs) require binding of both a tumor-associated surface antigen and CD3 for their immunotherapeutic effect. Their efficacy is, therefore, influenced by the tumor uptake and the extracellular dose. To optimize their currently limited efficacy in solid tumors, increased understanding of their pharmacokinetics and in vivo internalization is needed.

METHODS

Here, were studied the pharmacokinetics and in vivo internalization of CD3xTRP1, a fully murine Fc-inert bsAb, in endogenous TRP1-expressing immunocompetent male C57BL/6J mice bearing TRP1-positive and negative tumors over time. Matching bsAbs lacking TRP1-binding or CD3-binding capacity served as controls. BsAbs were radiolabeled with 111In to investigate their pharmacokinetics, target binding, and biodistribution through SPECT/CT imaging and ex vivo biodistribution analyses. Co-injection of 111In- and 125I-labeled bsAb was performed to investigate the in vivo internalization by comparing tissue concentrations of cellular residing 111In versus effluxing 125I. Antitumor therapy effects were evaluated by monitoring tumor growth and immunohistochemistry.

RESULTS

SPECT/CT and biodistribution analyses showed that CD3xTRP1 specifically targeted TRP1-positive tumors and CD3-rich lymphoid organ and uptake peaked 24 hours pi (KPC3-TRP1: 37.7%ID/g±5.3%ID/g, spleen: 29.0%ID/g±3.9%ID/g). Studies with control bsAbs demonstrated that uptake of CD3xTRP1 in TRP1-positive tumors and CD3-rich tissues was primarily receptor-mediated. Together with CD3xTRP1 in the circulation being mainly unattached, this indicates that CD3+ T cells are generally not traffickers of CD3-bsAbs to the tumor. Additionally, target-mediated clearance by TRP1-expressing melanocytes was not observed. We further demonstrated rapid internalization of CD3xTRP1 in KPC3-TRP1 tumors (24 hours pi: 54.9%±2.3% internalized) and CD3-rich tissues (spleen, 24 hours pi: 79.7%±0.9% internalized). Therapeutic effects by CD3xTRP1 were observed for TRP1-positive tumors and consisted of high tumor influx of CD8+ T cells and neutrophils, which corresponded with increased necrosis and growth delay.

CONCLUSIONS

We show that CD3xTRP1 efficiently targets TRP1-positive tumors and CD3-rich tissues primarily through receptor-mediated targeting. We further demonstrate rapid receptor-mediated internalization of CD3xTRP1 in TRP1-positive tumors and CD3-rich tissues. Even though this significantly decreases the therapeutical available dose, CD3xTRP1 still induced effective antitumor T-cell responses and inhibited tumor growth. Together, our data on the pharmacokinetics and mechanism of action of CD3xTRP1 pave the way for further optimization of CD3-bsAb therapies.

Safety and efficacy of T-cell-redirecting bispecific antibodies for patients with multiple myeloma: a systematic review and meta-analysis

BACKGROUND

In recent years, several bispecific antibodies (BsAbs) have been introduced that revolutionized the treatment approach for patients with multiple myeloma (MM). In the present study, we sought for conducting a systematic review and meta-analysis with the aim of evaluating the safety and efficacy of BsAbs in MM patients.

METHODS

PubMed, Scopus, Web of Science, and Embase databases were systematically searched on June 10, 2022. Two steps of title/abstract and full-text screening were performed for selecting the relevant articles. The primary endpoint was considered to evaluate the safety of BsAbs by examining the rate of hematologic and non-hematologic adverse effects (AEs). The secondary outcome was set at the efficacy of BsAbs through pooling objective response rate (ORR), (stringent) complete response (sCR/CR), very good partial response (VGPR), and partial response (PR).

RESULTS

Eleven publications with a total of nine evaluable BsAbs were included for qualitative and quantitative data synthesis. Hematologic AEs were more common among patients than non-hematologic events, with the most frequent events being anemia (41.4%), neutropenia (36.4%), and thrombocytopenia (26.3%). The most common non-hematological AE was infection, which occurred in 39.9% of patients, followed by dysgeusia (28.3%), fatigue (26.5%), and diarrhea (25.8%). Besides, 8.1% of patients experienced immune effector cell-associated neurotoxicity syndrome and neurotoxicity occurred in 5.1% of them. Moreover, 59.8% of patients experienced cytokine release syndrome. The pooled rate of deaths attributable to BsAbs was estimated at 0.1%. In terms of efficacy measures, the ORR was achieved in 62.6% of MM patients, and the pooled rates of sCR/CR, VGPR, and PR were 22.7%, 23.0%, and 12.1%, respectively.

CONCLUSIONS

In an era with several emerging promising treatments for MM, BsAbs have achieved a high ORR and tolerable AEs in heavily pretreated patients. However, there is still room for developing BsAbs with a lower rate of AEs and capable of bypassing tumor evasion mechanisms.

An engineered T-cell engager with selectivity for high mesothelin-expressing cells and activity in the presence of soluble mesothelin

Mesothelin (MSLN) is an attractive immuno-oncology target, but the development of MSLN-targeting therapies has been impeded by tumor shedding of soluble MSLN (sMSLN), on-target off-tumor activity, and an immunosuppressive tumor microenvironment. We sought to engineer an antibody-based, MSLN-targeted T-cell engager (αMSLN/αCD3) with enhanced ability to discriminate high MSLN-expressing tumors from normal tissue, and activity in the presence of sMSLN. We also studied the in vivo antitumor efficacy of this molecule (NM28-2746) alone and in combination with the multifunctional checkpoint inhibitor/T-cell co-activator NM21-1480 (αPD-L1/α4-1BB). Cytotoxicity and T-cell activation induced by NM28-2746 were studied in co-cultures of peripheral blood mononuclear cells and cell lines exhibiting different levels of MSLN expression, including in the presence of soluble MSLN. Xenotransplant models of human pancreatic cancer were used to study the inhibition of tumor growth and stimulation of T-cell infiltration into tumors induced by NM28-2746 alone and in combination with NM21-1480. The bivalent αMSLN T-cell engager NM28-2746 potently induced T-cell activation and T-cell mediated cytotoxicity of high MSLN-expressing cells but had much lower potency against low MSLN-expressing cells. A monovalent counterpart of NM28-2746 had much lower ability to discriminate high MSLN-expressing from low MSLN-expressing cells. The bivalent molecule retained this discriminant ability in the presence of high concentrations of sMSLN. In xenograft models, NM28-2746 exhibited significant tumor suppressing activity, which was significantly enhanced by combination therapy with NM21-1480. NM28-2746, alone or in combination with NM21-1480, may overcome shortcomings of previous MSLN-targeted immuno-oncology drugs, exhibiting enhanced discrimination of high MSLN-expressing cell activity in the presence of sMSLN.

Translational advances in the treatment of childhood acute lymphoblastic leukemia: narrative review of current and emerging molecular and immunotherapies

Background and Objective

Acute lymphoblastic leukemia (ALL) is the most common hematologic malignancy of lymphoid origin in children. The prognosis for newly diagnosed ALL in the pediatric population is generally favorable, with a 5-year overall survival rate of more than 90%. Though conventional therapy has led to meaningful improvements in cure rates for new-onset pediatric ALL, one-third of patients still experience a relapse or refractory disease, contributing to a significant cause of pediatric cancer-related mortality.

Methods

An extensive literature review was undertaken via various databases of medical literature, focusing on both results of larger clinical trials, but also with evaluation of recent abstract publications at large hematologic conferences.

Key Content and Findings

Remission is achievable in most of these patients by re-induction with currently available therapies, but the long-term overall survival rate is deemed suboptimal and remains a therapeutic challenge. As part of never-ceasing efforts to improve pediatric ALL outcomes, newer modalities, including targeted molecular therapies as well as immunotherapy, and chimeric antigen receptor (CAR) T-cell therapy, are currently being employed to increase treatment effectiveness as well as lessen the side effects from conventional chemotherapy. These approaches explore the use of early genome-based disease characterization and medications developed against actionable molecular targets.

Conclusions

Additional clinical research is nonetheless required to learn more about the potentially harmful effects of targeted therapies and investigate the possibility of these agents replacing or decreasing the use of conventional chemotherapy in treating pediatric ALL.

Bispecific Antibodies in Multiple Myeloma: Opportunities to Enhance Efficacy and Improve Safety

Multiple myeloma (MM) is the second most common haematological neoplasm of adults in the Western world. Overall survival has doubled since the advent of proteosome inhibitors (PIs), immunomodulatory agents (IMiDs), and monoclonal antibodies. However, patients with adverse cytogenetics or high-risk disease as determined by the Revised International Staging System (R-ISS) continue to have poorer outcomes, and triple-refractory patients have a median survival of less than 1 year. Bispecific antibodies (BsAbs) commonly bind to a tumour epitope along with CD3 on T-cells, leading to T-cell activation and tumour cell killing. These treatments show great promise in MM patients, with the first agent, teclistamab, receiving regulatory approval in 2022. Their potential utility is hampered by the immunosuppressive tumour microenvironment (TME), a hallmark of MM, which may limit efficacy, and by undesirable adverse events, including cytokine release syndrome (CRS) and infections, some of which may be fatal. In this review, we first consider the means of enhancing the efficacy of BsAbs in MM. These include combining BsAbs with other drugs that ameliorate the effect of the immunosuppressive TME, improving target availability, the use of BsAbs directed against multiple target antigens, and the optimal time in the treatment pathway to employ BsAbs. We then discuss methods to improve safety, focusing on reducing infection rates associated with treatment-induced hypogammaglobulinaemia, and decreasing the frequency and severity of CRS. BsAbs offer a highly-active therapeutic option in MM. Improving the efficacy and safety profiles of these agents may enable more patients to benefit from these novel therapies and improve outcomes for patients with high-risk disease.

Optimal Use of Novel Immunotherapeutics in B-Cell Precursor ALL

Novel immune therapies are currently being used for patients with R/R ALL based on their ability to induce not only hematologic but also molecular remission. Despite promising results, specific clinical conditions, such as high tumor burden or extra medullary relapse, are still associated with a remarkably poor clinical outcome. Therefore, how to optimize the choice and the timing of such new treatments within different clinical settings remains a matter of debate. In addition, with the aim of increasing the rate and depth of molecular remission, clinical studies are currently evaluating the combination of these immunotherapies with chemotherapy in the contest of frontline treatment. The preliminary data suggest that this approach may increase the cure rate and perhaps reduce the use of allogeneic stem cell transplantation (alloHSCT) in first remission. In Ph-positive ALL, reproducible results are showing that frontline treatment programs, based on the combination of tyrosine kinase inhibitors and immunotherapy, can achieve unprecedented rates of hematologic and molecular remission as well as a long-term cure, even in the absence of chemotherapy and alloHSCT. The results from these studies have led to the development of potentially curative treatment modalities, even for older ALL patients who cannot be treated with conventional intensive chemotherapy. The present review examined the evidence for an appropriate use of the new immunotherapies in ALL patients and provided some appraisal of the current and future possible uses of these drugs for achieving further therapeutic improvement in the treatment of this disease.

Microenvironment-responsive anti-PD-L1 × CD3 bispecific T-cell engager for solid tumor immunotherapy

Bispecific T-cell Engager (BiTE) antibodies can redirect T-cells to tumor cells, and turn on the targeted lysis of tumor cells. However, BiTE has been challenging in solid tumors due to short plasma half-life, "off-target" effect, and immunosuppression via PD-1/PD-L1 axis. This study designed a safe, long-acting, and highly effective Protease-Activated PSTAGylated BiTE, named PAPB, which includes a shielding polypeptide domain (PSTAG), a protease-activated linker, and a BiTE core. The BiTE core consists of two scFvs targeting PD-L1 and CD3. BiTE core bound PD-L1 and CD3 in a dose-dependent manner, and PAPB can release BiTE core in response to MMP2 in the tumor microenvironment to exert antitumor activity. The plasma half-life of PAPB in mice was significantly prolonged from 2.46 h to 6.34 h of the BiTE core. In mice bearing melanoma (A375) xenografts, PAPB significantly increased infiltration of T lymphocytes in tumor tissue, and inhibited tumor proliferation without activating T-cells in the peripheral blood. Overall, the engineering protein PAPB could be a promising drug candidate for solid tumor immunotherapy.

Immunotherapy for Meningiomas

Systemic treatment approaches are urgently needed for a subset of meningioma patients who do not achieve local tumor control with surgery and radiotherapy. Classical chemotherapy or anti-angiogenic agents exert only very limited activity in these tumors. Long-term survival of patients with advanced metastatic cancer following treatment with immune checkpoint inhibitors, i.e., monoclonal antibodies designed to unleash suppressed anticancer immune responses, has fostered hopes for benefit from similar approaches in patients with meningiomas that recur after standard local therapy. Moreover, a plethora of immunotherapy approaches beyond these drugs have entered clinical development or clinical practice for other cancer entities, including (i) novel immune checkpoint inhibitors that may act independently of T cell activity, (ii) cancer peptide or dendritic cell vaccines to induce anticancer immunity utilizing cancer-associated antigens, (iii) cellular therapies utilizing genetically modified peripheral blood cells to directly target cancer cells, (iv) T cell engaging recombinant proteins that link tumor antigen-binding sites to effector cell activating or recognition domains, or to immunogenic cytokines, and (v) oncolytic virotherapy utilizing attenuated viral vectors designed to specifically infect cancer cells, seeking to elicit systemic anticancer immunity. This chapter provides an overview of the principles of immunotherapy, summarizes ongoing immunotherapy clinical trials in meningioma patients, and discusses the applicability of established and emerging immunotherapy concepts to meningioma patients.

Targeted Treatment and Immunotherapy in High-risk and Relapsed/ Refractory Pediatric Acute Lymphoblastic Leukemia

Acute lymphoblastic leukemia is the most frequent pediatric malignancy in children, comprising 30% of all pediatric malignancies; adult ALL comprises 5% of all ALL cases, which have a 186.6 per 1 million incidence. In pediatric ALL (pALL), on which this review focuses, approximately 1 in 285 children are diagnosed with cancer before the age of 20, and approximately 1 in 530 young adults between the ages of 20 and 39 years old is a childhood cancer survivor. The survival probability in pALL is now very high, approximately 80-90%. Thus, the most important is to improve supportive care and treatment based on relapse risk, optimally being based on the genetic feature of malignant cells. Improvements made by now are mainly the classifying of subgroups based on genetic characteristics such as aneuploidy or translocation and aligning them with treatment response. Relevant genetic changes in ALL pathogenesis are transcription regulators of lymphoid development (PAX5, IKZF1, EBF1, and LEF1) and/or coactivators (TBL1XR1 and ERG), lymphoid signaling (BTLA, and CD200 TOX), and tumor suppressor genes (CDKN2A, CDKN2B, RB1, and TP53). This review aims to summarize treatment strategies inhibiting tyrosine kinases, influencing different signaling pathways, BCL inhibitors, and anti-CD therapy (anti-cluster differentiation therapy) in pALL. CAR T-cell therapy (chimeric antigen receptors T-cell therapy) is under research and requires further development.

PAX5 epigenetically orchestrates CD58 transcription and modulates blinatumomab response in acute lymphoblastic leukemia

Blinatumomab is an efficacious immunotherapeutic agent in B cell acute lymphoblastic leukemia (B-ALL). However, the pharmacogenomic basis of leukemia response to blinatumomab is unclear. Using genome-wide CRISPR, we comprehensively identified leukemia intrinsic factors of blinatumomab sensitivity, i.e., the loss of CD58 as a top driver for resistance, in addition to CD19. Screening 1639 transcription factor genes, we then identified PAX5 as the key activator of CD58. ALL with the PAX5 P80R mutation also expressed the lowest level of CD58 among 20 ALL molecular subtypes in 1988 patients. Genome editing confirmed the effects of this mutation on CD58 expression and blinatumomab sensitivity in B-ALL, with validation in patient leukemic blasts. We described a PAX5-driven enhancer at the CD58 locus, which was disrupted by PAX5 P80R, and the loss of CD58 abolished blinatumomab-induced T cell activation with global changes in transcriptomic/epigenomic program. In conclusion, we identified previously unidentified genetic mechanisms of blinatumomab resistance in B-ALL, suggesting strategies for genomics-guided treatment individualization.

Targeting TGF-β signaling in the multiple myeloma microenvironment: Steering CARs and T cells in the right direction

Multiple myeloma (MM) remains a lethal hematologic cancer characterized by the expansion of transformed plasma cells within the permissive bone marrow (BM) milieu. The emergence of relapsed and/or refractory MM (RRMM) is provoked through clonal evolution of malignant plasma cells that harbor genomic, metabolic and proteomic perturbations. For most patients, relapsed disease remains a major cause of overall mortality. Transforming growth factors (TGFs) have pleiotropic effects that regulate myelomagenesis as well as the emergence of drug resistance. Moreover, TGF-β modulates numerous cell types present with the tumor microenvironment, including many immune cell types. While numerous agents have been FDA-approved over the past 2 decades and significantly expanded the treatment options available for MM patients, the molecular mechanisms responsible for drug resistance remain elusive. Multiple myeloma is uniformly preceded by a premalignant state, monoclonal gammopathy of unknown significance, and both conditions are associated with progressive deregulation in host immunity characterized by reduced T cell, natural killer (NK) cell and antigen-presenting dendritic cell (DC) activity. TGF-β promotes myelomagenesis as well as intrinsic drug resistance by repressing anti-myeloma immunity to promote tolerance, drug resistance and disease progression. Hence, repression of TGF-β signaling is a prerequisite to enhance the efficacy of current and future immunotherapeutics. Novel strategies that incorporate T cells that have been modified to express chimeric antigen receptor (CARs), T cell receptors (TCRs) and bispecific T cell engagers (BiTEs) offer promise to block TGF-β signaling, overcome chemoresistance and enhance anti-myeloma immunity. Here, we describe the effects of TGF-β signaling on immune cell effectors in the bone marrow and emerging strategies to overcome TGF-β-mediated myeloma growth, drug resistance and survival.

Factors Affecting the Cancer Immunotherapeutic Efficacy of T Cell Bispecific Antibodies and Strategies for Improvement

T-cell bispecific antibodies (T-BsAbs) are a new class of cancer immunotherapy drugs that can simultaneously bind to tumor-associated antigens on target cells and to the CD3 subunit of the T-cell receptor (TCR) on T cells. In the last decade, numerous T-BsAbs have been developed for the treatment of both hematological malignancies and solid tumors. Among them, blinatumomab has been successfully used to treat CD19 positive malignancies and has been approved by the FDA as standard care for acute lymphoblastic leukemia (ALL). However, in many clinical scenarios, the efficacy of T-BsAbs remains unsatisfactory. To further improve T-BsAb therapy, it will be crucial to better understand the factors affecting treatment efficacy and the nature of the T-BsAb-induced immune response. Herein, we first review the studies on the potential mechanisms by which T-BsAbs activate T-cells and how they elicit efficient target killing despite suboptimal costimulatory support. We focus on analyzing reports from clinical trials and preclinical studies, and summarize the factors that have been identified to impact the efficacy of T-BsAbs. Lastly, we review current and propose new approaches to improve the clinical efficacy of T-BsAbs.

Immunotherapeutic progress and application of bispecific antibody in cancer

Bispecific antibodies (bsAbs) are artificial antibodies with two distinct antigen-binding sites that can bind to different antigens or different epitopes on the same antigen. Based on a variety of technology platforms currently developed, bsAbs can exhibit different formats and mechanisms of action. The upgrading of antibody technology has promoted the development of bsAbs, which has been effectively used in the treatment of tumors. So far, 7 bsAbs have been approved for marketing in the world, and more than 200 bsAbs are in clinical and preclinical research stages. Here, we summarize the development process of bsAbs, application in tumor treatment and look forward to the challenges in future development.

CUL3/SPOP complex prevents immune escape and enhances chemotherapy sensitivity of ovarian cancer cells through degradation of PD-L1 protein

BACKGROUND

Cancer immune escape is a main obstacle in designing effective anticancer therapeutic approaches. Our work was aimed to explore the function of cullin 3 (CUL3) in ovarian cancer cell immune escape and chemosensitivity.

METHOD

Gain and loss of function assays were conducted to investigate the interactions among CUL3, speckle type POZ protein (SPOP) and programmed death ligand-1 (PD-L1) as well as their effects on ovarian cell malignant phenotypes and chemosensitivity. A mouse model of xenografted ovarian cells was further established for in vivo substantiation.

RESULT

Poorly-expressed CUL3 and SPOP were found in ovarian cancer. Overexpression of CUL3 reduced malignant features as well as immune escape of ovarian cancer cells but enhanced chemosensitivity. Functionally, CUL3 degraded PD-L1 protein by forming complex with SPOP. Overexpression of CUL3 inhibited tumor formation and enhanced chemosensitivity of ovarian cancer cells in mice by degrading PD-L1 protein.

CONCLUSION

All in all, CUL3/SPOP formed a complex to promote PD-L1 degradation to inhibit ovarian cancer cell immune escape and increase chemosensitivity, offering a therapeutic target for ovarian cancer treatment.

Reprogramming the tumor microenvironment to improve the efficacy of cancer immunotherapies

The immunotherapeutic approaches based on checkpoint inhibitors, tumor vaccination, immune cell-based therapy, and cytokines were developed to engage the patient's immune system against cancer and better survival of them. While potent, however, preclinical and clinical data have identified that abnormalities in the tumor microenvironment (TME) can affect the efficacy of immunotherapies in some cancers. It is therefore imperative to develop new therapeutic interventions that will enable to overcome tumor-supportive TME and restrain anti-tumor immunity in patients that acquire resistance to current immunotherapies. Therefore, recognition of the essential nature of the tolerogenic TME may lead to a shift from the immune-suppressive TME to an immune-stimulating phenotype. Here, we review the composition of the TME and its effect on tumor immunoediting and then present how targeted monotherapy or combination therapies can be employed for reprogramming educated TME to improve current immunotherapies outcomes or elucidate potential therapeutic targets.

Recent Advances in Glioma Cancer Treatment: Conventional and Epigenetic Realms

Glioblastoma (GBM) is the most typical and aggressive form of primary brain tumor in adults, with a poor prognosis. Successful glioma treatment is hampered by ineffective medication distribution across the blood-brain barrier (BBB) and the emergence of drug resistance. Although a few FDA-approved multimodal treatments are available for glioblastoma, most patients still have poor prognoses. Targeting epigenetic variables, immunotherapy, gene therapy, and different vaccine- and peptide-based treatments are some innovative approaches to improve anti-glioma treatment efficacy. Following the identification of lymphatics in the central nervous system, immunotherapy offers a potential method with the potency to permeate the blood-brain barrier. This review will discuss the rationale, tactics, benefits, and drawbacks of current glioma therapy options in clinical and preclinical investigations.

Immunotherapy for Pediatric Acute Lymphoblastic Leukemia: Recent Advances and Future Perspectives

Pediatric acute lymphoblastic leukemia (ALL) is the most common subtype of childhood leukemia, which is characterized by the abnormal proliferation and accumulation of immature lymphoid cell in the bone marrow. Although the long-term survival rate for pediatric ALL has made significant progress over years with the development of contemporary therapeutic regimens, patients are still suffered from relapse, leading to an unsatisfactory outcome. Since the immune system played an important role in the progression and relapse of ALL, immunotherapy including bispecific T-cell engagers and chimeric antigen receptor T cells has been demonstrated to be capable of enhancing the immune response in pediatric patients with refractory or relapsed B-cell ALL, and improving the cure rate of the disease and patients’ quality of life, thus receiving the authorization for market. Nevertheless, the resistance and toxicities associated with the current immunotherapy remains a huge challenge. Novel therapeutic options to overcome the above disadvantages should be further explored. In this review, we will thoroughly discuss the emerging immunotherapeutics for the treatment of pediatric ALL, as well as side-effects and new development.

[Preparation of CD33 targeted bispecific- and trispecific-T cell engagers and their cytotoxicity on leukemia cells]

Objective: To investigate the effect of CD33-targeted bi-specific and tri-specific T-cell engagers on T-cell proliferation and explore their cytotoxicity on leukemia cells. Methods: The CD33-targeted bi-specific T-cell engager (CD33-BiTE) and tri-specific T-cell engager (CD33-TriTE) expression vectors were successfully constructed and expressed through a eukaryotic cell expression system. CD33-BiTE and CD33-TriTE were purified by affinity chromatography. The effects of CD33-BiTE and CD33-TriTE on T cells were analyzed through in vitro experiments. Results: ① CD33-BiTE and CD33-TriTE were successfully constructed and purified and could compete with flow cytometry antibodies for binding to the target cells. ② After 12 days of co-culture with CD33-BiTE and CD33-TriTE, the number of human T cells were expanded to 33.89±19.46 and 81.56±23.62 folds, respectively. CD33-TriTE induced a stronger proliferation of T cells than CD33-BiTE (P<0.05) . ③ Both CD33-BiTE and CD33-TriTE induced specific dose-dependent cytotoxicity on CD33(+) leukemia cells. ④ Compared to CD33-TriTE, leukemia cells were prone to express PD-L1 when co-cultured with T cells and CD33-BiTE. CD33-TriTE induced powerful cytotoxicity on leukemia cells with high PD-L1 expression. Conclusion: CD33-BiTE and CD33-TriTE expression vectors were constructed, and fusion proteins were expressed in eukaryotic cells. Our results support the proliferative and activating effects of BiTE and TriTE on T cells. Compared to that of CD33-BiTE, CD33-TriTE induced a stronger proliferative effect on T cells and a more powerful cytotoxicity on leukemia cells with high PD-L1 expression.

Oncogenic magnesium transporter 1 upregulates programmed death-1-ligand 1 expression and contributes to growth and radioresistance of glioma cells through the ERK/MAPK signaling pathway

Radiotherapy has been established as a major therapeutic modality for glioma, whereas new therapeutic targets are needed to prevent tumor recurrence. This study intends to explore the regulatory role of magnesium transporter 1 (MAGT1) in radiotherapy resistance of glioma through modulating ERK and programmed death-1-ligand 1 (PD-L1). Our bioinformatics analysis identified differentially expressed MAGT1 in glioma, expression of which was subsequently determined in cohort data of TCGA database and microarray dataset as well as glioma cell lines. Artificial modulation of MAGT1, ERK, and PD-L1 expression was performed to examine their effects on glioma cell proliferation and radioresistance, as reflected by MTT and colony formation assays under irradiation. Mouse glioma cells with manipulated MAGT1 and ERK inhibitors were further injected into mice to assess the in vivo tumor formation ability of glioma cells. It was noted that MAGT1 expression was highly expressed in glioma tissues of TCGA data and microarray dataset, which was then validated in glioma cell lines. Ectopic expression of MAGT1 was revealed to promote the proliferation and radioresistance of glioma cells, which was attributed to the MAGT1-mediated activation of the ERK/MAPK signaling pathway. It was illuminated that MAGT1 stimulated PD-L1 expression through the ERK/MAPK pathway and thus facilitated glioma cell growth. Additionally, MAGT1 overexpression accelerated the in vivo tumor formation of glioma cells, while the ERK inhibitor negated its effect. In conclusion, MAGT1 enhances the growth and radioresistance of glioma cells through the ERK/MAPK signaling pathway-mediated upregulation of PD-L1 expression.

T-cell redirecting bispecific antibodies in multiple myeloma: a revolution?

Bispecific antibodies are designed to link a surface target molecule on the malignant plasma cells to CD3 on T-cells and thereby redirect activated T-cells to induce tumor cell death. Early-phase clinical trials targeting B-cell maturation antigen, GPRC5D or FcRH5, have demonstrated a favorable safety profile and promising efficacy data in triple-class refractory multiple myeloma. This novel immunotherapeutic modality will likely change the treatment paradigm in the coming years.

Evaluation of Programmed Death Ligand-1 Immunohistochemical Expression and Tumor-Infiltrating Lymphocytes in Different Types of Endometrial Carcinoma

BACKGROUND: Endometrial cancer (EC) identified at an early stage is successfully treated in a majority of patients with surgery with or without radiotherapy or chemotherapy. For patients with advanced disease, however, the prognosis is poor; 5-year survival rates are less than 50% in patients with lymph node metastases and less than 20% with peritoneal or distant metastases. Previous studies proved that programmed death-1/programmed death ligand-1 (PD1-/PD-L1) blockers are currently effectively used as immunotherapies in a number of tumors such as melanoma and non-small cell lung cancer. AIM: This study was conducted to determine the expression of PD L1 in endometrial carcinoma and to assess its potential role as a biomarker for different types that can be used to screen candidates fit for immunotherapy. MATERIALS AND METHODS: This cross-sectional study was carried out on 32 cases of endometrial carcinoma cases that underwent endometrial biopsies, dilatation, and curettage or radical hysterectomies at Ain Shams University Hospitals Pathology Units from 2018 to 2020 with their clinical and radiological assessments. Correlation between hematoxylin and eosin-stained histopathological sections and PD-L1 immunohistochemical staining of the same sections, mainly emphasizing the tumor-infiltrating lymphocytes, was done. RESULTS: PDL-1-positive expression of both tumor cells and TILs was significantly more frequent in type II endometrial carcinoma (p = 0.04 and 0.03, respectively) using a cut-off value 10%, compared to type I. Moreover, Grade III tumors showed significantly more frequent PDL-1 expression in both tumor cells and TILs than Grade I and II tumors, using 5% and 10% cut-off values indicating that PDL-1 is overexpressed in aggressive tumors. CONCLUSION: PD-L1 staining is significantly related to high-grade tumors and type II endometrial carcinomas, the aggressive types, which support their probable benefit from immunotherapy. Separate assessment of PD-L1-positive staining in both tumor cells or TILs with a cut-off value 10% can significantly reflect the aggressiveness of the tumor and its probable benefit from immunotherapy.

Cancer immunomodulation using bispecific aptamers

Evasion of immune destruction is a major hallmark of cancer. Recent US Food and Drug Administration (FDA) approvals of various immunomodulating therapies underline the important role that reprogramming the immune system can play in combating this disease. However, a wide range of side effects still limit the therapeutic potential of immunomodulators, suggesting a need for more precise reagents with negligible off-target and on-target/off-tumor effects. Aptamers are single-chained oligonucleotides that bind their targets with high specificity and affinity owing to their three-dimensional (3D) structures, and they are one potential way to address this need. In particular, bispecific aptamers (bsApts) have been shown to induce artificial immune synapses that promote T cell activation and subsequent tumor cell lysis in various in vitro and in vivo pre-clinical models. We discuss these advances here, along with gaps in bsApt biology at both the cellular and resident tissue levels that should be addressed to accelerate their translation into the clinic. The broad application, minimal production cost, and relative lack of immunogenicity of bsApts give them some ideal qualities for manipulating the immune system. Building upon lessons from other novel therapies, bsApts could soon provide clinicians with an immunomodulating toolbox that is not only potent and efficacious but exercises a wide therapeutic index.

T Cell Bispecific Antibodies: An Antibody-Based Delivery System for Inducing Antitumor Immunity

As a breakthrough immunotherapy, T cell bispecific antibodies (T-BsAbs) are a promising antibody therapy for various kinds of cancer. In general, T-BsAbs have dual-binding specificity to a tumor-associated antigen and a CD3 subunit forming a complex with the TCR. This enables T-BsAbs to crosslink tumor cells and T cells, inducing T cell activation and subsequent tumor cell death. Unlike immune checkpoint inhibitors, which release the brake of the immune system, T-BsAbs serve as an accelerator of T cells by stimulating their immune response via CD3 engagement. Therefore, they can actively redirect host immunity toward tumors, including T cell recruitment from the periphery to the tumor site and immunological synapse formation between tumor cells and T cells. Although the low immunogenicity of solid tumors increases the challenge of cancer immunotherapy, T-BsAbs capable of immune redirection can greatly benefit patients with such tumors. To investigate the detailed relationship between T-BsAbs delivery and their T cell redirection activity, it is necessary to determine how T-BsAbs deliver antitumor immunity to the tumor site and bring about tumor cell death. This review article discusses T-BsAb properties, specifically their pharmacokinetics, redirection of anticancer immunity, and local mechanism of action within tumor tissues, and discuss further challenges to expediting T-BsAb development.

Rejuvenation of tumour-specific T cells through bispecific antibodies targeting PD-L1 on dendritic cells

Bispecific T-cell engagers (BiTEs) preferentially targeting tumour-associated antigens and stimulating CD3-mediated signalling are being used in patients to treat acute B-cell lymphoblastic leukemia. However, the potency of BiTEs in solid tumours is limited by their short half-life and their severe toxicity at relevant therapeutic doses. Here we report the design and in vivo performance of a bispecific antibody that simultaneously targets the murine T-cell co-receptor CD3ε and the murine immune checkpoint programmed-death ligand 1 (PD-L1). In multiple syngeneic tumour models, the bispecific antibody generated higher antitumour immune responses than conventional BiTEs targeting tumour-associated antigens and CD3ε. We found that the durable antigen-specific T-cell responses resulted from the rejuvenation of CD8 T cells, owing to the blockade of PD-L1 on dendritic cells (but not on tumour cells) and co-stimulation by B7-1&2 (a peripheral membrane protein on dendritic cells). Bispecific T-cell engagers targeting dendritic cells rather than tumour cells may represent a general means of T-cell rejuvenation for durable cancer immunotherapy.

Alteration of the immune environment in bone marrow from children with recurrent B cell precursor acute lymphoblastic leukemia

Due to the considerable success of cancer immunotherapy for leukemia, the tumor immune environment has become a focus of intense research; however, there are few reports on the dynamics of the tumor immune environment in leukemia. Here, we analyzed the tumor immune environment in pediatric B cell precursor acute lymphoblastic leukemia by analyzing serial bone marrow samples from nine patients with primary and recurrent disease by mass cytometry using 39 immunophenotype markers, and transcriptome analysis. High‐dimensional single‐cell mass cytometry analysis elucidated a dynamic shift of T cells from naïve to effector subsets, and clarified that, during relapse, the tumor immune environment comprised a T helper 1‐polarized immune profile, together with an increased number of effector regulatory T cells. These results were confirmed in a validation cohort using conventional flow cytometry. Furthermore, RNA transcriptome analysis identified the upregulation of immune‐related pathways in B cell precursor acute lymphoblastic leukemia cells during relapse, suggesting interaction with the surrounding environment. In conclusion, a tumor immune environment characterized by a T helper 1‐polarized immune profile, with an increased number of effector regulatory T cells, could contribute to the pathophysiology of recurrent B cell precursor acute lymphoblastic leukemia. This information could contribute to the development of effective immunotherapeutic approaches against B cell precursor acute lymphoblastic leukemia relapse.

Microenvironmental IL-6 inhibits anti-cancer immune responses generated by cytotoxic chemotherapy

Cytotoxic chemotherapeutics primarily function through DNA damage-induced tumor cell apoptosis, although the inflammation provoked by these agents can stimulate anti-cancer immune responses. The mechanisms that control these distinct effects and limit immunogenic responses to DNA-damage mediated cell death in vivo are currently unclear. Using a mouse model of BCR-ABL⁺ B-cell acute lymphoblastic leukemia, we show that chemotherapy-induced anti-cancer immunity is suppressed by the tumor microenvironment through production of the cytokine IL-6. The chemotherapeutic doxorubicin is curative in IL-6-deficient mice through the induction of CD8⁺ T-cell-mediated anti-cancer responses, while moderately extending lifespan in wild type tumor-bearing mice. We also show that IL-6 suppresses the effectiveness of immune-checkpoint inhibition with anti-PD-L1 blockade. Our results suggest that IL-6 is a key regulator of anti-cancer immune responses induced by genotoxic stress and that its inhibition can switch cancer cell clearance from primarily apoptotic to immunogenic, promoting and maintaining durable anti-tumor immune responses.

Bispecific Immunomodulatory Antibodies for Cancer Immunotherapy

The recent advances in the field of immuno-oncology have dramatically changed the therapeutic strategy against advanced malignancies. Bispecific antibody-based immunotherapies have gained momentum in preclinical and clinical investigations following the regulatory approval of the T cell-redirecting antibody blinatumomab. In this review, we focus on emerging and novel mechanisms of action of bispecific antibodies interacting with immune cells with at least one of their arms to regulate the activity of the immune system by redirecting and/or reactivating effector cells toward tumor cells. These molecules, here referred to as bispecific immunomodulatory antibodies, have the potential to improve clinical efficacy and safety profile and are envisioned as a second wave of cancer immunotherapies. Currently, there are more than 50 bispecific antibodies under clinical development for a range of indications, with promising signs of therapeutic activity. We also discuss two approaches for in vivo secretion, direct gene delivery, and infusion of ex vivo gene-modified cells, which may become instrumental for the clinical application of next-generation bispecific immunomodulatory antibodies.

BL-01, an Fc-bearing, tetravalent CD20 × CD5 bispecific antibody, redirects multiple immune cells to kill tumors in vitro and in vivo

BACKGROUND AIMS

The authors describe here a novel therapeutic strategy combining a bispecific antibody (bsAb) with cytokine-induced killer (CIK) cells.

METHODS

The authors have designed, produced and purified a novel tetravalent IgG1-like CD20 × CD5 bsAb called BL-01. The bsAb is composed of a fused heavy chain and two free light chains that pair correctly to the heavy chain sequences thanks to complementary mutations in the monoclonal antibody 2 CH1/CL sequences.

RESULTS

The authors show that BL-01 can bind specifically to CD20 and CD5 with an affinity of 4-6 nM, demonstrating correct pairing of two light chains to the fused heavy chain. The CD20 × CD5 BL-01 bsAb has a functional human IgG1 Fc and can induce up to 65% complement-dependent cytotoxicity of a CD20⁺ lymphoma cell line in the presence of human complement, similar to anti-CD20 rituximab. The bsAb also induces significant natural killer cell activation and antibody-dependent cytotoxicity of up to 25% as well as up to 65% phagocytosis by human macrophages in the presence of CD20⁺ tumor cells. The BL-01 bsAb binds to CD20 and CD5 simultaneously and can redirect CIK cells in vitro to kill CD20⁺ targets, increasing the cytotoxicity of CIK cells by about 3-fold. The authors finally show that the CD20 × CD5 BL-01 bsAb synergizes with CIK cells in vivo in controlling tumor growth and prolonging survival of nonobese diabetic/severe combined immunodeficiency mice inoculated with a patient-derived, aggressive diffuse large B-cell lymphoma xenograft.

CONCLUSIONS

The authors suggest that the efficacy of bsAb in vivo is due to the combined activation of innate immunity by Fc and redirection of CIK cells to kill the tumor target.

The evolving status of immunotherapies in multiple myeloma: the future role of bispecific antibodies

Treatment outcomes in multiple myeloma (MM) have improved dramatically over the past 10 years. However, patients with high-risk disease such as those with Stage III disease by the Revised International Staging System, the presence of adverse cytogenetics, or who are refractory to proteosome inhibitors, immunomodulatory drugs and monoclonal antibodies may have dismal outcomes. These patients represent an urgent ongoing need in MM. One of the hallmarks of MM is immune dysfunction and a tumour-permissive immune microenvironment. Ameliorating the immune-paresis could lead to improved outcomes. The role of immunotherapies has been growing at an exponential pace with numerous agents under development in clinical trials. In the present review, we provide an overview of immunotherapies in MM, focussing on bispecific antibodies (BsAbs). We review efficacy outcomes from the published clinical trials and consider the important safety aspects of these therapies, in particular the risk of cytokine-release syndrome and immune effector cell-associated neurotoxicity syndrome, and how these compare with patients receiving chimeric antigen receptor T cells. We discuss the MM epitopes being targeted by BsAbs, either in clinical or preclinical stages, and we consider where these therapies might best fit within the future ever-changing paradigm of MM treatment.

Efficacy and tolerability of a modified pediatric-inspired intensive regimen for acute lymphoblastic leukemia in older adults

Although acute lymphoblastic leukemia (ALL) is most common in pediatric and adolescent and young adult (AYA) patients, 20% of cases are diagnosed in patients ≥ 55 years old. Use of intensive pediatric regimens in AYA populations has demonstrated excellent tolerability and significant improvements in event-free survival (EFS) and overall survival (OS). The backbone of pediatric regimens includes asparaginase and corticosteroids, both of which are associated with more toxicity in older patients and those with body mass index (BMI) ≥ 30 kg/m which leads to poor tolerance of these regimens. We tested the safety and efficacy of a dose-modified The Cancer and Leukemia Group B 10403 regimen using reduced doses of pegylated (PEG)-asparaginase (ASP) and corticosteroids (RD-10403) in 30 patients with Philadelphia-chromosome negative ALL who were ≥50-year-old and younger adults with significant metabolic or hepatic co-morbidities. The complete remission rate on day 28 was 77%, 3-year EFS was 54%, and estimated 3-year OS was 55%. Grade 3+ toxicity was noted in 40% of patients during induction, and induction-related mortality was 3%. Additional prospective evaluation of RD-10403 is merited to determine efficacy and safety of this regimen and to serve as a framework for chemoimmunotherapy combination therapy.

Blinatumomab for HLA loss relapse after haploidentical hematopoietic stem cell transplantation

Loss of patient-specific HLA after haploidentical hematopoietic stem cell transplantation (haplo-HSCT) is considered as a relapse mechanism for lacking the incompatible molecule to elicit alloreactivity, which extensively diminishing graft-versus-leukemia (GVL) effects. Blinatumomab, as a CD3/CD19 bispecific antibody, can yield a profound response via redirecting T cells towards malignant lymphoblasts in B-cell acute lymphoblastic leukemia (B-ALL). We aimed to assess the feasibility of blinatumomab in treating patients with HLA loss relapse after haplo-HSCT. Four eligible patients undergoing HLA loss relapse after haplo-HSCT were enrolled in the study. Four patients achieved a complete remission/complete remission with partial he-matologic recovery (CR/CRh) with three minimal residual disease (MRD)-negative response within the first cycle of treatment. Three of the four met a primary endpoint with CR/CRh and MRD-negative response within 2 cycles of treatment. One patient developed new extramedullary sites of skin after the first cycle. Cytokine release syndrome was observed in one patient. Cytopenias, as well as elevated alanine aminotransferase and aspartate aminotransferase, were two common adverse effects during treatment. By redirecting lysis of CD19-positive lymphoblast who losing the incompatible HLA, blinatumomab is a potential strategy to eradicate malignant cells via restoring GVL effects. A randomized clinical trial assessing blinatumomab in patients with HLA loss relapse after HSCT is warranted.

The landscape of bispecific T cell engager in cancer treatment

T cell-based immunotherapies have revolutionized treatment paradigms in various cancers, however, limited response rates secondary to lack of significant T-cell infiltration in the tumor site remain a major problem. To address this limitation, strategies for redirecting T cells to treat cancer are being intensively investigated, while the bispecific T cell engager (BiTE) therapy constitutes one of the most promising therapeutic approaches. BiTE is a bispecific antibody construct with a unique function, simultaneously binding an antigen on tumor cells and a surface molecule on T cells to induce tumor lysis. BiTE therapy represented by blinatumomab has achieved impressive efficacy in the treatment of B cell malignancies. However, major mechanisms of resistance to BiTE therapy are associated with antigen loss and immunosuppressive factors such as the upregulation of immune checkpoints. Thus, modification of antibody constructs and searching for combination strategies designed to further enhance treatment efficacy as well as reduce toxicity has become an urgent issue, especially for solid tumors in which response to BiTE therapy is always poor. In particular, immunotherapies focusing on innate immunity have attracted increasing interest and have shown promising anti-tumor activity by engaging innate cells or innate-like cells, which can be used alone or complement current therapies. In this review, we depict the landscape of BiTE therapy, including clinical advances with potential response predictors, challenges of treatment toxicity and resistance, and developments of novel immune cell-based engager therapy.

AMG 701 induces cytotoxicity of multiple myeloma cells and depletes plasma cells in cynomolgus monkeys

Multiple myeloma (MM) is a hematologic malignancy that is characterized by the accumulation of abnormal plasma cells (PCs) in the bone marrow (BM). Patient outcome may be improved with BiTE (bispecific T-cell engager) molecules, which redirect T cells to lyse tumor cells. B-cell maturation antigen (BCMA) supports PC survival and is highly expressed on MM cells. A half-life extended anti-BCMA BiTE molecule (AMG 701) induced selective cytotoxicity against BCMA-expressing MM cells (average half-maximal effective concentration, 18.8 ± 14.8 pM), T-cell activation, and cytokine release in vitro. In a subcutaneous mouse xenograft model, at all doses tested, AMG 701 completely inhibited tumor formation (P < .001), as well as inhibited growth of established tumors (P ≤ .001) and extended survival in an orthotopic MM model (P ≤ .01). To evaluate AMG 701 bioactivity in cynomolgus monkeys, a PC surface phenotype and specific genes were defined to enable a quantitative digital droplet polymerase chain reaction assay (sensitivity, 0.1%). Dose-dependent pharmacokinetic and pharmacodynamic behavior was observed, with depletion of PC-specific genes reaching 93% in blood and 85% in BM. Combination with a programmed cell death protein 1 (PD-1)-blocking antibody significantly increased AMG 701 potency in vitro. A model of AMG 701 binding to BCMA and CD3 indicates that the distance between the T-cell and target cell membranes (ie, the immunological synapse) is similar to that of the major histocompatibility complex class I molecule binding to a T-cell receptor and suggests that the synapse would not be disrupted by the half-life extending Fc domain. These data support the clinical development of AMG 701.

Bispecific T cell engagers: an emerging therapy for management of hematologic malignancies

Harnessing the power of immune cells, especially T cells, to enhance anti-tumor activities has become a promising strategy in clinical management of hematologic malignancies. The emerging bispecific antibodies (BsAbs), which recruit T cells to tumor cells, exemplified by bispecific T cell engagers (BiTEs), have facilitated the development of tumor immunotherapy. Here we discussed the advances and challenges in BiTE therapy developed for the treatment of hematologic malignancies. Blinatumomab, the first BiTE approved for the treatment of acute lymphocytic leukemia (ALL), is appreciated for its high efficacy and safety. Recent studies have focused on improving the efficacy of BiTEs by optimizing treatment regimens and refining the molecular structures of BiTEs. A considerable number of bispecific T cell-recruiting antibodies which are potentially effective in hematologic malignancies have been derived from BiTEs. The elucidation of mechanisms of BiTE action and neonatal techniques used for the construction of BsAbs can improve the treatment of hematological malignancies. This review summarized the features of bispecific T cell-recruiting antibodies for the treatment of hematologic malignancies with special focus on preclinical experiments and clinical studies.