Mechanisms of Resistance to Monoclonal Antibodies (mAbs) in Lymphoid Malignancies

Multiantigen T-Cell Hybridizers: A Two-Component T-Cell-Activating Therapy

Multispecific T-cell-engaging scaffolds have emerged as effective anticancer therapies for the treatment of hematological malignancies. Approaches that modulate cancer cell targeting and provide personalized, multispecific immunotherapeutics are needed. Here, we report on a modular, split antibody-like approach consisting of Fab' fragments modified with complementary morpholino oligonucleotides (MORFs). We synthesized a library of B-cell-targeting Fab'-MORF1 conjugates that self-assemble, via a Watson-Crick base pairing hybridization, with a complementary T-cell-engaging Fab'-MORF2 conjugate. We aptly titled our technology multiantigen T-cell hybridizers (MATCH). Using MATCH, cancer-specific T-cell recruitment was achieved utilizing four B-cell antigen targets: CD20, CD38, BCMA, and SLAMF7. The antigen expression profiles of various malignant B-cell lines were produced, and using these distinct profiles, cell-specific T-cell activation was attained on lymphoma, leukemia, and multiple myeloma cell lines in vitro. T-cell rechallenge experiments demonstrated the modular approach of MATCH by sequentially activating the same T-cell cohort against three different cancers using cancer antigen-specific Fab'-MORF1 conjugates. Furthermore, MATCH's efficacy was demonstrated in vivo by treating xenograft mouse models of human non-Hodgkin's lymphoma with CD20-directed MATCH therapy. In the pilot study, a single dose of MATCH allowed for long-term survival of all treated mice compared to saline control. In a second in vivo model, insights regarding optimal T-cell-to-target cell ratio were gleaned when a ratio of 5:1 T-cell-to-target cell MATCH-treated mice significantly delayed the onset of disease compared to higher and lower ratios.

The Evolving Paradigm of Antibody-Drug Conjugates Targeting the ErbB/HER Family of Receptor Tyrosine Kinases

Current therapies targeting the human epidermal growth factor receptor (HER) family, including monoclonal antibodies (mAbs) and tyrosine kinase inhibitors (TKIs), are limited by drug resistance and systemic toxicities. Antibody-drug conjugates (ADCs) are one of the most rapidly expanding classes of anti-cancer therapeutics with 13 presently approved by the FDA. Importantly, ADCs represent a promising therapeutic option with the potential to overcome traditional HER-targeted therapy resistance by delivering highly potent cytotoxins specifically to HER-overexpressing cancer cells and exerting both mAb- and payload-mediated antitumor efficacy. The clinical utility of HER-targeted ADCs is exemplified by the immense success of HER2-targeted ADCs including trastuzumab emtansine and trastuzumab deruxtecan. Still, strategies to improve upon existing HER2-targeted ADCs as well as the development of ADCs against other HER family members, particularly EGFR and HER3, are of great interest. To date, no HER4-targeting ADCs have been reported. In this review, we extensively detail clinical-stage EGFR-, HER2-, and HER3-targeting monospecific ADCs as well as novel clinical and pre-clinical bispecific ADCs (bsADCs) directed against this receptor family. We close by discussing nascent trends in the development of HER-targeting ADCs, including novel ADC payloads and HER ligand-targeted ADCs.

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.

Development of Plant-Derived Bispecific Monoclonal Antibody Targeting PD-L1 and CTLA-4 against Mouse Colorectal Cancer

Checkpoint blockade immunotherapy has revolutionized cancer treatment, with monoclonal antibodies targeting immune checkpoints, yielding promising clinical benefits. However, with the advent of resistance to immune checkpoint inhibitor treatment in clinical trials, developing next-generation antibodies with potentially increased efficacy is critical. Here, we aimed to generate a recombinant bispecific monoclonal antibody for dual inhibition of programmed cell death protein 1/programmed cell death ligand 1 and cytotoxic T-lymphocyte-associated protein 4 axes. The plant system was used as an alternative platform for bispecific monoclonal antibody production. Dual variable domain immunoglobulin atezolizumab × 2C8 is a plant-derived bispecific monoclonal antibody that combines both programmed cell death ligand 1 and cytotoxic T-lymphocyte-associated protein 4 blockade into a single molecule. Dual variable domain immunoglobulin atezolizumab × 2C8 was transiently expressed in Nicotiana benthamiana and the expression level was determined to be the highest after 4 days of infiltration. The size and assembly of the purified bispecific monoclonal antibody were determined, and its function was investigated in vitro and in vivo. The molecular structures of plant-produced dual variable domain immunoglobulin atezolizumab × 2C8 are as expected, and it was mostly present as a monomer. The plant-produced dual variable domain immunoglobulin atezolizumab × 2C8 showed in vitro binding to programmed cell death ligand 1 and cytotoxic T-lymphocyte-associated protein 4 proteins. The antitumor activity of plant-produced bispecific monoclonal antibody was tested in vivo by treating humanized Balb/c mice bearing a CT26 colorectal tumor. Plant-produced dual variable domain immunoglobulin atezolizumab × 2C8 significantly inhibited tumor growth by reducing tumor volume and weight. Body weight changes indicated that the plant-produced bispecific monoclonal antibody was safe and tolerable. Overall, this proof of concept study demonstrated the viability of plants to produce functional plant-based bispecific immunotherapy.

A Kinetically Controlled Bioconjugation Method for the Synthesis of Radioimmunoconjugates and the Development of a Domain Mapping MS-Workflow for Its Characterization

Immunoconjugates exploit the high affinity of monoclonal antibodies for a recognized antigen to selectively deliver a cytotoxic payload, such as drugs or radioactive nuclides, at the site of disease. Despite numerous techniques have been recently developed for site-selective bioconjugations of protein structures, reaction of ε-amine group of lysine residues with electrophilic reactants, such as activated esters (NHS), is the main method reported in the literature as it maintains proteins in their native conformation. Since antibodies hold a high number of lysine residues, a heterogeneous mixture of conjugates will be generated, which can result in decreased target affinity. Here, we report an intradomain regioselective bioconjugation between the monoclonal antibody Trastuzumab and the N-hydroxysuccinimide ester of the chelator 2,2',2″,2‴-(1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrayl)tetraacetic acid (DOTA) by a kinetically controlled reaction adding substoichiometric quantities of the activated ester to the mAb working at slightly basic pH. Liquid chromatography-mass spectrometry (LC-MS) analyses were carried out to assess the chelator-antibody ratio (CAR) and the number of chelating moieties linked to the mAb chains. Proteolysis experiments showed four lysine residues mainly involved in bioconjugation (K188 for the light chain and K30, K293, and K417 for the heavy chain), each of which was located in a different domain. Since the displayed intradomain regioselectivity, a domain mapping MS-workflow, based on a selective domain denaturation, was developed to quantify the percentage of chelator linked to each mAb domain. The resulting immunoconjugate mixture showed an average CAR of 0.9. About a third of the heavy chains were found as monoconjugated, whereas conjugation of the chelator in the light chain was negligible. Domain mapping showed the CH3 domain bearing 13% of conjugated DOTA, followed by CH2 and VH respectively bearing 12.5 and 11% of bonded chelator. Bioconjugation was not found in the CH1 domain, whereas for the light chain, only the CL domain was conjugated (6%). Data analysis based on LC-MS quantification of different analytical levels (intact, reduced chains, and domains) provided the immunoconjugate formulation. A mixture of immunoconjugates restricted to 15 species was obtained, and the percentage of each one within the mixture was calculated. In particular, species bearing 1 DOTA with a relative abundance ranging from 4 to 20-fold, in comparison to species bearing 2DOTA, were observed. Pairing of bioconjugation under kinetic control with the developed domain mapping MS-workflow could raise the standard of chemical quality for immunoconjugates obtained with commercially available reactants.

Structure-Guided and Phage-Assisted Evolution of Therapeutic Antibodies to Reverse On-Target Point Mutation-Mediated Resistance

Resistance to therapeutic antibodies caused by on-target point mutations is a major obstacle in anticancer therapy, creating an "unmet clinical need." To tackle this problem, researchers are developing new generations of antibody drugs that can overcome the resistance mechanisms of existing agents. We have previously reported a structure-guided and phage-assisted evolution (SGAPAE) approach to evolve cetuximab, a therapeutic antibody, to effectively reverse the resistance driven by EGFRS492R or EGFRG465R mutations, without changing the binding epitope or compromising the antibody efficacy. In this protocol, we provide detailed instructions on how to use the SGAPAE approach to evolve cetuximab, which can also be applied to other therapeutic antibodies for reversing on-target point mutation-mediated resistance. The protocol consists of four steps: structure preparation, computational prediction, phage display library construction, and antibody candidate selection.

Radio-immunotherapy by 188Re-antiCD20 and stable silencing of IGF-IR in Raji cells, new insight in treatment of lymphoma

Hematologic malignancies such as Non-Hodgkin's lymphoma (NHL), remain a serious threat to human health due to their heterogeneity and complexity. The inherent genetic heterogeneity of NHL B-cells, as well as the instability of lymphoma cancer cells, results in drug resistance in lymphoma, posing a fundamental challenge to NHL treatment. Burkitt lymphoma (including Raji cell line) is a rare and highly aggressive form of B-cell NHL. Since overexpression of the insulin-like growth factor-1 receptor (IGF-1R) playing a prominent role in the development and transformation of different malignancies, especially lymphoma malignancies, we have explored the role of IGF-1R in the development and progression of Raji cells and the stable silencing of IGF-1R by lentivirus-mediated RNA interference (RNAi). We have shown that stable silencing of the IGF-1R gene in Raji cells using lentivirus-mediated-RNAi have resulted in a significant reduction in Raji cell proliferation. Moreover, the results of the cell viability assays indicatedhigh resistance of Raji cells to rituximab. However, coupling rituximab to 188Re potentially leads to specific targeting of Raji cells by 188Re, improving the therapeutic efficacy. We found that the synergistic effect of using a gene therapy-based system in combination with radioimmunotherapy could be a promising therapeutic strategy in the future. To the best of our knowledge, this is the first study that reports the knock down of IGF-1R via lentiviral-mediated shRNA in Raji cells.

Bispecific antibodies in cancer therapy: Target selection and regulatory requirements

In recent years, the development of bispecific antibodies (bsAbs) has been rapid, with many new structures and target combinations being created. The boom in bsAbs has led to the successive issuance of industry guidance for their development in the US and China. However, there is a high degree of similarity in target selection, which could affect the development of diversity in bsAbs. This review presents a classification of various bsAbs for cancer therapy based on structure and target selection and examines the advantages of bsAbs over monoclonal antibodies (mAbs). Through database research, we have identified the preferences of available bsAbs combinations, suggesting rational target selection options and warning of potential wastage of medical resources. We have also compared the US and Chinese guidelines for bsAbs in order to provide a reference for their development.

Mechanisms of Action and Limitations of Monoclonal Antibodies and Single Chain Fragment Variable (scFv) in the Treatment of Cancer

Monoclonal antibodies are among the most effective tools for detecting tumor-associated antigens. The U.S. Food and Drug Administration (FDA) has approved more than 36 therapeutic antibodies for developing novel alternative therapies that have significant success rates in fighting cancer. However, some functional limitations have been described, such as their access to solid tumors and low interaction with the immune system. Single-chain variable fragments (scFv) are versatile and easy to produce, and being an attractive tool for use in immunotherapy models. The small size of scFv can be advantageous for treatment due to its short half-life and other characteristics related to the structural and functional aspects of the antibodies. Therefore, the main objective of this review was to describe the current situation regarding the mechanisms of action, applications, and limitations of monoclonal antibodies and scFv in the treatment of cancer.

Multi-targeted immunotherapeutics to treat B cell malignancies

The concept of multi-targeted immunotherapeutic systems has propelled the field of cancer immunotherapy into an exciting new era. Multi-effector molecules can be designed to engage with, and alter, the patient's immune system in a plethora of ways. The outcomes can vary from effector cell recruitment and activation upon recognition of a cancer cell, to a multipronged immune checkpoint blockade strategy disallowing evasion of the cancer cells by immune cells, or to direct cancer cell death upon engaging multiple cell surface receptors simultaneously. Here, we review the field of multi-specific immunotherapeutics implemented to treat B cell malignancies. The mechanistically diverse strategies are outlined and discussed; common B cell receptor antigen targeting strategies are outlined and summarized; and the challenges of the field are presented along with optimistic insights for the future.

T-Cell Engagers in Solid Cancers-Current Landscape and Future Directions

Monoclonal antibody treatment initially heralded an era of molecularly targeted therapy in oncology and is now widely applied in modulating anti-cancer immunity by targeting programmed cell receptors (PD-1, PD-L1), cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and, more recently, lymphocyte-activation gene 3 (LAG3). Chimeric antigen receptor T-cell therapy (CAR-T) recently proved to be a valid approach to inducing anti-cancer immunity by directly modifying the host's immune cells. However, such cell-based therapy requires extensive resources such as leukapheresis, ex vivo modification and expansion of cytotoxic T-cells and current Good Manufacturing Practice (cGMP) laboratories and presents significant logistical challenges. Bi-/trispecific antibody technology is a novel pharmaceutical approach to facilitate the engagement of effector immune cells to potentially multiple cancer epitopes, e.g., the recently approved blinatumomab. This opens the opportunity to develop 'off-the-shelf' anti-cancer agents that achieve similar and/or complementary anti-cancer effects as those of modified immune cell therapy. The majority of bi-/trispecific antibodies target the tumor-associated antigens (TAA) located on the extracellular surface of cancer cells. The extracellular antigens represent just a small percentage of known TAAs and are often associated with higher toxicities because some of them are expressed on normal cells (off-target toxicity). In contrast, the targeting of intracellular TAAs such as mutant RAS and TP53 may lead to fewer off-target toxicities while still achieving the desired antitumor efficacy (on-target toxicity). Here, we provide a comprehensive review on the emerging field of bi-/tri-specific T-cell engagers and potential therapeutic opportunities.

Combined Vaccination with B Cell Peptides Targeting Her-2/neu and Immune Checkpoints as Emerging Treatment Option in Cancer

The application of monoclonal antibodies (mAbs), targeting tumor-associated (TAAs) or tumor-specific antigens or immune checkpoints (ICs), has shown tremendous success in cancer therapy. However, the application of mAbs suffers from a series of limitations, including the necessity of frequent administration, the limited duration of clinical response and the emergence of frequently pronounced immune-related adverse events. However, the introduction of mAbs has also resulted in a multitude of novel developments for the treatment of cancers, including vaccinations against various tumor cell-associated epitopes. Here, we reviewed recent clinical trials involving combination therapies with mAbs targeting the PD-1/PD-L1 axis and Her-2/neu, which was chosen as a paradigm for a clinically highly relevant TAA. Our recent findings from murine immunizations against the PD-1 pathway and Her-2/neu with peptides representing the mimotopes/B cell peptides of therapeutic antibodies targeting these molecules are an important focus of the present review. Moreover, concerns regarding the safety of vaccination approaches targeting PD-1, in the context of the continuing immune response, as a result of induced immunological memory, are also addressed. Hence, we describe a new frontier of cancer treatment by active immunization using combined mimotopes/B cell peptides aimed at various targets relevant to cancer biology.

Targeting the immune microenvironment in mantle cell lymphoma: implications for current and emerging therapies

Mantle cell lymphoma (MCL) is a morphologically and phenotypically heterogeneous subtype of non-Hodgkin lymphoma, and has historically been associated with poor outcomes. However, recent advances in our understanding of this disease have yielded new targeted and immune-based therapies with promising activity. Immune-based therapies such as monoclonal antibodies, immunomodulators, and CAR T cells have significantly improved outcomes and are now standard of care in MCL. In this review, we describe our current understanding of the immune microenvironment of MCL, discuss current immunotherapeutic approaches, and highlight promising novel immune-based therapies and combination therapies that may further improve outcomes for patients with MCL.

Simultaneous crosslinking of CD20 and CD38 receptors by drug-free macromolecular therapeutics enhances B cell apoptosis in vitro and in vivo

Drug-Free Macromolecular Therapeutics (DFMT) is a new paradigm in macromolecular therapeutics that induces apoptosis in target cells by crosslinking receptors without the need of low molecular weight drugs. Programmed cell death is initiated via a biomimetic receptor crosslinking strategy using a two-step approach: i) recognition of cell surface antigen by a morpholino oligonucleotide-modified antibody Fab' fragment (Fab'-MORF1), ii) followed by crosslinking with a multivalent effector motif - human serum albumin (HSA) grafted with multiple complementary morpholino oligonucleotides (HSA-(MORF2)x). This approach is effective in vitro, in vivo, and ex vivo on cells from patients diagnosed with various B cell malignancies. We have previously demonstrated DFMT can be applied to crosslink CD20 and CD38 receptors to successfully initiate apoptosis. Herein, we show simultaneous engagement, and subsequent crosslinking of both targets ("heteroreceptor crosslinking"), can further enhance the apoptosis induction capacity of this system. To accomplish this, we incubated Raji (CD20+; CD38+) cells simultaneously with anti-CD20 and anti-CD38 Fab'-MORF1 conjugates, followed by addition of the macromolecular crosslinker, HSA-(MORF2)x to co-cluster the bound receptors. Fab' fragments from Rituximab and Obinutuzumab were employed in the synthesis of anti-CD20 bispecific engagers (Fab'RTX-MORF1 and Fab'OBN-MORF1), whereas Fab' fragments from Daratumumab and Isatuximab (Fab'DARA-MORF1 and Fab'ISA-MORF1) targeted CD38. All heteroreceptor crosslinking DFMT combinations demonstrated potent apoptosis induction and exhibited synergistic effects as determined by Chou-Talalay combination index studies (CI < 1). In vitro fluorescence resonance energy transfer (FRET) experiments confirmed the co-clustering of the two receptors on the cell surface in response to the combination treatment. The source of this synergistic therapeutic effect was further explored by evaluating the effect of combination DFMT on key apoptosis signaling events such as mitochondrial depolarization, caspase activation, lysosomal enlargement, and homotypic cell adhesion. Finally, a xenograft mouse model of CD20+/CD38+ Non Hodgkin lymphoma was employed to demonstrate in vivo the enhanced efficacy of the heteroreceptor-crosslinking DFMT design versus single-target systems.

Active immunization with a Her-2/neu-targeting Multi-peptide B cell vaccine prevents lung metastases formation from Her-2/neu breast cancer in a mouse model

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Trastuzumab and Pertuzumab extend the overall survival of breast cancer patients.

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Unlike monoclonal antibodies B cell peptides induce immunological memory.

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A multi-peptide B cell-based vaccination prevents Her-2/neu lung metastasis in mice.

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The vaccination results in Her-2/neu-negative tumors, with increased PD-L1 expression.

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A combination/alternating therapy for a total remission of metastases is suggested.

In pre-clinical and clinical settings, active immunization with a Her-2/neu vaccine (HerVaxx), comprising B-cell peptide from Trastuzumab binding site, has been shown to reduce primary tumor growth via induction of polyclonal anti-tumor immune responses and immunological memory. Here, we tested the combination of HerVaxx and the recently identified B-cell epitope/mimotope of Pertuzumab, i.e. a multi-peptide B-cell vaccine, for preventing Her-2/neu lung metastases formation in a mouse model. Active immunization with the multi-peptide vaccine was associated with decreased lung weights, and histological evaluation of the lungs showed that the significant reduction of lung metastases was associated with increased CD4⁺ and CD8⁺ T cell infiltration. Notably, along with the overall reduction of lungs weights and Her-2 positive metastases, a formation of Her-2/neu-negative tumors but with increased PD-L1 expression was observed. Our results might pave the way to a multi-peptide B-cell Her-2/neu vaccine serving as a secondary intervention in adjuvant settings to prevent tumor recurrence and spread. Moreover, combination therapy targeting PD-L1 may result in total remission of metastases. Such a therapy may be used clinically to alternately target Her-2/neu and PD-L1 in metastatic breast cancer.

Immunotherapeutic Strategies in Chronic Lymphocytic Leukemia: Advances and Challenges

Immune-based therapeutic strategies have drastically changed the landscape of hematological disorders, as they have introduced the concept of boosting immune responses against tumor cells. Anti-CD20 monoclonal antibodies have been the first form of immunotherapy successfully applied in the treatment of CLL, in the context of chemoimmunotherapy regimens. Since then, several immunotherapeutic approaches have been studied in CLL settings, with the aim of exploiting or eliciting anti-tumor immune responses against leukemia cells. Unfortunately, despite initial promising data, results from pilot clinical studies have not shown optimal results in terms of disease control - especially when immunotherapy was used individually - largely due to CLL-related immune dysfunctions hampering the achievement of effective anti-tumor responses. The growing understanding of the complex interactions between immune cells and the tumor cells has paved the way for the development of new combined approaches that rely on the synergism between novel agents and immunotherapy. In this review, we provide an overview of the most successful and promising immunotherapeutic modalities in CLL, including both antibody-based therapy (i.e. monoclonal antibodies, bispecific antibodies, bi- or tri- specific killer engagers) and adoptive cellular therapy (i.e. CAR T cells and NK cells). We also provide examples of successful new combination strategies and some insights on future perspectives.

IRF8 is a transcriptional activator of CD37 expression in diffuse large B-cell lymphoma

IRF8 is a transcriptional regulator of CD37 expression in DLBCL, which may have implications for anti-CD37 therapies.

Patients with poor prognostic CD37-negative DLBCL show significantly lower IRF8 expression compared with patients with CD37-positive DLBCL.

Diffuse large B-cell lymphoma (DLBCL) represents the most common form of non-Hodgkin lymphoma (NHL) that is still incurable in a large fraction of patients. Tetraspanin CD37 is highly expressed on mature B lymphocytes, and multiple CD37-targeting therapies are under clinical development for NHL. However, CD37 expression is nondetectable in ∼50% of DLBCL patients, which correlates with inferior treatment outcome, but the underlying mechanisms for differential CD37 expression in DLBCL are still unknown. Here, we investigated the regulation of the CD37 gene in human DLBCL at the (epi-)genetic and transcriptional level. No differences were observed in DNA methylation within the CD37 promoter region between CD37-positive and CD37-negative primary DLBCL patient samples. On the contrary, CD37-negative DLBCL cells specifically lacked CD37 promoter activity, suggesting differential regulation of CD37 gene expression. Using an unbiased quantitative proteomic approach, we identified transcription factor IRF8 to be significantly higher expressed in nuclear extracts of CD37-positive as compared with CD37-negative DLBCL. Direct binding of IRF8 to the CD37 promoter region was confirmed by DNA pulldown assay combined with mass spectrometry and targeted chromatin immunoprecipitation (ChIP). Functional analysis indicated that IRF8 overexpression enhanced CD37 protein expression, while CRISPR/Cas9 knockout of IRF8 decreased CD37 levels in DLBCL cell lines. Immunohistochemical analysis in a large cohort of primary DLBCL (n = 206) revealed a significant correlation of IRF8 expression with detectable CD37 levels. Together, this study provides new insight into the molecular mechanisms underlying differential CD37 expression in human DLBCL and reveals IRF8 as a transcriptional regulator of CD37 in B-cell lymphoma.

Vaccination against Her-2/neu, with focus on peptide-based vaccines

Immunotherapy has been a milestone in combatting cancer, by complementing or even replacing classic treatments like surgery, chemotherapy, radiation, and anti-hormonal therapy. In 15%-30% of breast cancers, overexpression of the human epidermal growth factor receptor 2 (Her-2/neu) is associated with more aggressive tumor development. Passive immunization/immunotherapy with the recombinantly produced Her-2/neu-targeting monoclonal antibodies (mAbs) pertuzumab and trastuzumab has been shown to effectively treat breast cancer and lead to a significantly better prognosis. However, allergic and hypersensitivity reactions, cardiotoxicity, development of resistance, lack of immunological memory which results in continuous application over a long period, and cost-intensiveness are among the drawbacks associated with this treatment. Furthermore, intrinsic or acquired resistance is associated with the application of therapeutic mAbs, leading to the disease recurrence. Conversely, these drawbacks could be potentially overcome by vaccination, i.e. an active immunization/immunotherapy approach by activating the patient’s own immune system to target cancer, along with inducing immunological memory. This review aims to summarize the main approaches investigated and undertaken for the production of Her-2/neu vaccine candidates, with the main focus on peptide-based vaccines and their evaluation in clinical settings.

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Her-2/neu is overexpressed in 10%-30% of breast and gastric cancer patients and this correlates with poor clinical outcomes.

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Passive application of trastuzumab and pertuzumab has outstandingly improved the Her-2/neu-related clinical outcomes.

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Treatment with mAbs is associated with frequent administration, cost-intensiveness, and resistance.

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Vaccination against Her-2/neu with e.g. mimotope- or peptide-based vaccines can alternatively overcome the mAbs’ drawbacks.

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Such alternatives may pave the way to therapeutics which could be used as monotherapy or in combination therapies with mAbs.

Remodeling the Tumor Myeloid Landscape to Enhance Antitumor Antibody Immunotherapies

Among the diverse tumor resident immune cell types, tumor-associated macrophages (TAMs) are often the most abundant, possess an anti-inflammatory phenotype, orchestrate tumor immune evasion and are frequently associated with poor prognosis. However, TAMs can also be harnessed to destroy antibody-opsonized tumor cells through the process of antibody-dependent cellular phagocytosis (ADCP). Clinically important tumor-targeting monoclonal antibodies (mAb) such as Rituximab, Herceptin and Cetuximab, function, at least in part, by inducing macrophages to eliminate tumor cells via ADCP. For IgG mAb, this is mediated by antibody-binding activating Fc gamma receptors (FcγR), with resultant phagocytic activity impacted by the level of co-engagement with the single inhibitory FcγRIIb. Approaches to enhance ADCP in the tumor microenvironment include the repolarization of TAMs to proinflammatory phenotypes or the direct augmentation of ADCP by targeting so-called 'phagocytosis checkpoints'. Here we review the most promising new strategies targeting the cell surface molecules present on TAMs, which include the inhibition of 'don't eat me signals' or targeting immunostimulatory pathways with agonistic mAb and small molecules to augment tumor-targeting mAb immunotherapies and overcome therapeutic resistance.

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.

Down-regulation of cylindromatosis protein phosphorylation by BTK inhibitor promotes apoptosis of non-GCB-diffuse large B-cell lymphoma

BACKGROUND

Non-germinal center B-cell-like diffuse large B-cell lymphoma (non-GCB-DLBCL) has worse clinical outcome than GCB-DLBCL, and some relapsed/refractory non-GCB-DLBCL (R/R non-GCB-DLBCL) are even resistant to CD20 monoclonal antibody (rituximab). Bruton's tyrosine kinase inhibitors (BTKis) are new drugs for B-cell lymphoma. BTKis can promote apoptosis of DLBCL by inactivating nuclear transcription factor κB (NFκB) signaling pathway. Cylindromatosis (CYLD) is a tumor suppressor and ubiquitinase. CYLD can inactivate NFκB signaling pathway through ubiquitination and regulate the apoptosis of hematological tumors. The ubiquitination of CYLD can be regulated by phosphorylation, suggesting that the regulation of CYLD phosphorylation can be a potential mechanism to promote the apoptosis of hematological tumors. Therefore, we hypothesized that BTKis could promote the apoptosis of non-GCB-DLBCL by regulating the phosphorylation of CYLD, especially in rituximab resistant cases, and we proved this hypothesis through both in vivo and in vitro experiments.

METHODS

The baseline expression levels of CYLD phosphorylation in non-GCB-DLBCL patients and cell lines were detected by Western Blotting. The non-GCB-DLBCL cell lines were treated with BTKis, and apoptosis induced by BTKis treatment was detected by Western blotting, cell viability assay and Annexin V assay. To verify whether the effect of BTKis on apoptosis in non-GCN-DLBCL cells is CYLD dependent, the expression of CYLD was knocked down by lentiviral shRNAs. To verify the effect of BTKis on the phosphorylation of CYLD and the apoptosis in vivo and in rituximab resistant non-GCB-DLBCL, the xeograft model and rituximab resistant non-GCB-DLBCL cells were generated by tumor cell inoculation and escalation of drug concentrations, respectively.

RESULTS

BTKis induced apoptosis by down-regulating CYLD phosphorylationin in non GCB-DLBCL, xenograft mouse model, and rituximab-resistant cells, and this effect could be enhanced by rituximab. Knocking-down CYLD reversed apoptosis which was induced by BTKis. BTKis induced CYLD-dependent apoptosis in non-GCB-DLBCL including in rituximab-resistant cells.

CONCLUSIONS

The present results indicated that CYLD phosphorylation is a potential clinical therapeutic target for non-GCB-DLBCL, especially for rituximab-resistant relapsed/refractory cases.

The role of autophagy in resistance to targeted therapies

Autophagy is a self-degradative cellular process, involved in stress response such as starvation, hypoxia, and oxidative stress. This mechanism balances macro-molecule recycling to regulate cell homeostasis. In cancer, autophagy play a role in the development and progression, while several studies describe it as one of the key processes in drug resistance. In the last years, in addition to standard anti-cancer treatments such as chemotherapies and irradiation, targeted therapy became one of the most adopted strategies in clinical practices, mainly due to high specificity and reduced side effects. However, similar to standard treatments, drug resistance is the main challenge in most patients. Here, we summarize recent studies that investigated the role of autophagy in drug resistance after targeted therapy in different types of cancers. We highlight positive results and limitations of pre-clinical and clinical studies in which autophagy inhibitors are used in combination with targeted therapies.

Genetically engineered mesenchymal stem cells: targeted delivery of immunomodulatory agents for tumor eradication

Cancer immunotherapy emerged as a novel therapeutic option that employs enhanced or amended native immune system to create a robust response against malignant cells. The systemic therapies with immune-stimulating cytokines have resulted in substantial dose-limiting toxicities. Targeted cytokine immunotherapy is being explored to overcome the heterogeneity of malignant cells and tumor cell defense with a remarkable reduction of systemic side effects. Cell-based strategies, such as dendritic cells (DCs), fibroblasts or mesenchymal stem cells (MSCs) seek to minimize the numerous toxic side effects of systemic administration of cytokines for extended periods of time. The usual toxicities comprised of a vascular leak, hypotension, and respiratory insufficiency. Natural and strong tropism of MSCs toward malignant cells made them an ideal systemic delivery vehicle to direct the proposed therapeutic genes to the vicinity of a tumor where their expression could evoke an immune reaction against the tumor. Compared with other methods, the delivery of cytokines via engineered MSCs is safer and renders a more practical, and promising strategy. Large numbers of genes code for cytokines have been utilized to reengineer MSCs as therapeutic cells. This review highlights the recent findings on the cytokine gene therapy for human malignancies by focusing on MSCs application in cancer immunotherapy.