CD16 polymorphisms and NK activation induced by monoclonal antibody-coated target cells

Induction of cell death in malignant cells and regulatory T cells in the tumor microenvironment by targeting CD137

Regulatory T cells (Tregs) contribute significantly to the immunosuppressive nature of the tumor microenvironment which is a main barrier for immunotherapies of solid cancers. Reducing Treg numbers enhances anti-tumor immune responses but current depletion strategies also impair effector T cells (Teffs), potentially leading to reduced anti-tumor immunity and/or autoimmune diseases. CD137 has been identified as the most differentially expressed gene between peripheral Tregs and intratumoral Tregs in virtually all solid cancers. Further, CD137 is expressed by malignant cells of certain cancers, making it a potential target for tumor immunotherapy. Here, we report the development of a fully human anti-human CD137 antibody of the IgG1 isotype, clone P1A1, that induces antibody-dependent cell-mediated cytotoxicity (ADCC) in CD137+ Tregs and cancer cells. P1A1 cross-reacts with murine CD137 which allowed testing murine chimeric P1A1 in syngeneic murine tumor models where P1A1 significantly reduced the number of CD137+ Tregs and inhibited tumor growth in a murine hepatocellular carcinoma (HCC) and a melanoma lung metastasis model. P1A1 can also be internalized thus enabling it as a carrier for drugs to target CD137+ Tregs and cancer cells. These anti-cancer properties suggest a translation of P1A1 to human immunotherapy.

Impact of Fc-gamma receptor IIIA polymorphism on late-onset neutropenia and clinical outcomes in kidney transplant recipients following rituximab induction therapy

BACKGROUND

This study aimed to investigate the association between the Fc-gamma receptor IIIA (FCGR3A) 158 polymorphism and clinical outcomes in kidney transplantation (KTx) patients. Specifically, we focused on late-onset neutropenia (LON) in ABO-incompatible (ABOi) or HLA-incompatible (HLAi) KTx recipients who underwent rituximab (RTx) desensitization therapy.

METHODS

FCGR3A 158F/V polymorphisms were identified in 85 ABOi or HLAi KTx recipients who underwent RTx desensitization at our institution between April 2008 and October 2021. We analyzed these polymorphism groups in relation to their preoperative background and incidence of LON, infection, and rejection. In addition, we examined the risk factors for LON development.

RESULTS

The following FCGR3A 158F/V polymorphisms were identified: FF genotype (n = 45); FV genotype (n = 36), and VV genotype (n = 4). LON occurred in 25 out of 85 recipients within 1 year after KTx, significantly more frequently in patients with the FCGR3A FV + VV genotype (17/40) than in those with the FF genotype (8/45) (p = 0.01). A multivariate analysis identified the V-allele as an independent risk factor for LON (OR, 4.03; 95% CI, 1.38-11.73, p = 0.01). However, there were no significant differences in the incidence rates of post-transplant infection and rejection between the FF and FV + VV genotypes.

CONCLUSION

Recipients with the FCGR3A 158 V-allele were identified as having a higher risk of developing LON following KTx with RTx desensitization therapy. However, the presence of this V-allele did not affect the safety or efficacy of RTx desensitization before KTx.

Advancements in cancer immunotherapies targeting CD20: from pioneering monoclonal antibodies to chimeric antigen receptor-modified T cells

CD20 located predominantly on the B cells plays a crucial role in their development, differentiation, and activation, and serves as a key therapeutic target for the treatment of B-cell malignancies. The breakthrough of monoclonal antibodies directed against CD20, notably exemplified by rituximab, revolutionized the prognosis of B-cell malignancies. Rituximab, approved across various hematological malignancies, marked a paradigm shift in cancer treatment. In the current landscape, immunotherapies targeting CD20 continue to evolve rapidly. Beyond traditional mAbs, advancements include antibody-drug conjugates (ADCs), bispecific antibodies (BsAbs), and chimeric antigen receptor-modified (CAR) T cells. ADCs combine the precision of antibodies with the cytotoxic potential of drugs, presenting a promising avenue for enhanced therapeutic efficacy. BsAbs, particularly CD20xCD3 constructs, redirect cytotoxic T cells to eliminate cancer cells, thereby enhancing both precision and potency in their therapeutic action. CAR-T cells stand as a promising strategy for combatting hematological malignancies, representing one of the truly personalized therapeutic interventions. Many new therapies are currently being evaluated in clinical trials. This review serves as a comprehensive summary of CD20-targeted therapies, highlighting the progress and challenges that persist. Despite significant advancements, adverse events associated with these therapies and the development of resistance remain critical issues. Understanding and mitigating these challenges is paramount for the continued success of CD20-targeted immunotherapies.

Affibody-based hBCMA x CD16 dual engagers for NK cell-mediated killing of multiple myeloma cells

We describe the development and characterization of the (to date) smallest Natural Killer (NK) cell re-directing human B Cell Maturation Antigen (hBCMA) x CD16 dual engagers for potential treatment of multiple myeloma, based on combinations of small 58 amino acid, non-immunoglobulin, affibody affinity proteins. Affibody molecules to human CD16a were selected from a combinatorial library by phage display resulting in the identification of three unique binders with affinities (KD) for CD16a in the range of 100 nM-3 µM. The affibody exhibiting the highest affinity demonstrated insensitivity towards the CD16a allotype (158F/V) and did not interfere with IgG (Fc) binding to CD16a. For the construction of hBCMA x CD16 dual engagers, different CD16a binding arms, including bi-paratopic affibody combinations, were genetically fused to a high-affinity hBCMA-specific affibody. Such 15-23 kDa dual engager constructs showed simultaneous hBCMA and CD16a binding ability and could efficiently activate resting primary NK cells and trigger specific lysis of a panel of hBCMA-positive multiple myeloma cell lines. Hence, we report a novel class of uniquely small NK cell engagers with specific binding properties and potent functional profiles.

Inhibitory receptors for HLA class I as immune checkpoints for natural killer cell-mediated antibody-dependent cellular cytotoxicity in cancer immunotherapy

Natural killer (NK) cells mediate potent anti-tumor responses, which makes them attractive targets for immunotherapy. The anti-tumor response of endogenous- or allogeneic NK cells can be enhanced through clinically available monoclonal antibodies that mediate antibody-dependent cellular cytotoxicity (ADCC). NK cell activation is regulated by interaction of inhibitory receptors with classical- and non-classical human leukocyte antigens (HLA) class I molecules. Inhibitory receptors of the killer immunoglobulin-like receptor (KIR) family interact with HLA-A, -B or -C epitopes, while NKG2A interacts with the non-classical HLA-E molecule. Both types of inhibitory interactions may influence the strength of the ADCC response. In the present review, we provide an overview of the effect of inhibitory KIRs and NKG2A on NK cell-mediated ADCC, which highlights the rationale for combination strategies with ADCC triggering antibodies and interference with the NK cell relevant inhibitory immune checkpoints, such as KIR and NKG2A.

Potent immunomodulatory and antitumor effect of anti-CD20-IL2no-alpha tri-functional immunocytokine for cancer therapy

Introduction

The anti-CD20 antibody rituximab (RTX) has substantially improved outcomes of patients with B-cell lymphomas, although more efficient therapies are needed for refractory or relapsing lymphomas. An approach to increase the clinical effectiveness of anti-tumor therapy is the use of antibody-cytokine fusion proteins (immunocytokines (ICKs)) to deliver at the tumor site the antibody effector functions and cytokines that trigger anti-tumor activities. In particular, IL-2-based ICKs have shown significant results in preclinical studies but not in clinical trials due to the toxicity profile associated to high doses IL-2 and the undesired expansion of Tregs.

Methods

To improve the efficacy of RTX therapy, we fused a murine (mIgG2a) or a human (hIgG1) version of RTX to a mutated IL-2 (no-alpha mutein), which has a disrupted affinity for the high affinity IL-2 receptor (IL-2R) to prevent the stimulation of Tregs and reduce the binding to endothelial cells expressing CD25, the α chain of high affinity IL-2R. Characterization of anti-CD20-IL2no-alpha ICKs was performed by SDS-PAGE, Western-blotting and SEC-HPLC and also by several functional in vitro techniques like T-cell proliferation assays, apoptosis, CDC and ADCC assays. The in vivo activity was assessed by using murine tumor cells expressing huCD20 in C57/Bl6 mice.

Results

Both ICKs exhibited similar in vitro specific activity of their IL2no-alpha mutein moieties and kept CD20-binding capacity. Anti-CD20-IL2no-alpha (hIgG1) retained antibody effector functions as complement-dependent cytotoxicity and enhanced direct apoptosis, NK cell activation and antibody-dependent cellular cytotoxicity relative to RTX. In addition, both ICKs demonstrated a higher antitumor efficacy than parental molecules or their combination in an EL4-huCD20 tumor model in immunocompetent mice. Anti-CD20-IL2no-alpha (hIgG1) strongly expanded NK and CD8+ T cells but not Tregs in tumor-bearing mice.

Discussion

These findings suggest that anti-CD20-IL2no-alpha could represent an alternative treatment for B cell lymphoma patients, mainly those refractory to RTX therapy.

Natural Killer Cells Are Key Host Immune Effector Cells Affecting Survival in Autologous Peripheral Blood Hematopoietic Stem Cell Transplantation

The infusion of autograft immune effector cells directly impacts the clinical outcomes of patients treated with autologous peripheral blood hematopoietic stem cell transplantation, suggesting the possibility of an autologous graft-versus tumor cells. Furthermore, the early recovery of immune effector cells also affects survival post-autologous peripheral blood hematopoietic stem cell transplantation. Natural killer cells are among the immune effector cells reported to be collected, infused, and recovered early post-autologous peripheral blood hematopoietic stem cell transplantation. In this review, I attempt to give an update on the role of natural killer cells regarding improving survival outcomes on patients treated with autologous peripheral blood hematopoietic stem cell transplantation.

Factor VIII-Fc Activates Natural Killer Cells via Fc-Mediated Interactions With CD16

The most challenging complication associated with Factor VIII (FVIII) replacement therapy is the development of neutralizing anti-drug antibodies, or inhibitors, which occur in 23-35% of severe (FVIII level <1%) hemophilia A (HA) patients and are a serious hindrance to effective management of HA. Consequently, strategies that can either prevent anti-FVIII inhibitors from developing or "tolerize" individuals who develop such antibodies represent a clinically important unmet need. One intervention for patients with high-titer inhibitors is immune tolerance induction (ITI) therapy. Although ITI therapy is the only clinically proven strategy to eradicate anti-FVIII inhibitors, mechanisms of inhibitor reduction remain unknown. Factor VIII Fc-fusion (rFVIIIFc) is an enhanced half-life antihemophilic factor used in replacement therapy for HA. Fc-fusion is a successful protein bio-engineering platform technology. In addition to enhancement of plasma half-life via neonatal Fc receptor (FcRn) binding, other Fc-mediated interactions, including engagement with Fc gamma receptors (FcγR), may have immunological consequences. Several case reports and retrospective analyses suggest that rFVIIIFc offers superior outcomes with respect to ITI compared to other FVIII products. Previously we and others demonstrated rFVIIIFc interactions with activating FcγRIIIA/CD16. Here, we investigated if rFVIIIFc activates natural killer (NK) cells via CD16. We demonstrated rFVIIIFc signaling via CD16 independent of Von Willebrand Factor (VWF):FVIII complex formation. We established that rFVIIIFc potently activated NK cells in a CD16-dependent fashion resulting in IFNγ secretion and cytolytic perforin and granzyme B release. We also demonstrated an association between rFVIIIFc-mediated NK cell IFNγ secretion levels and the high-affinity (158V) CD16 genotype. Furthermore, we show that rFVIIIFc-activated CD16⁺ NK cells were able to lyse a B-cell clone (BO2C11) bearing an anti-FVIII B-cell receptor in an antibody-dependent cellular cytotoxicity (ADCC) assay. These in vitro findings provide an underlying molecular mechanism that may help explain clinical case reports and retrospective studies suggesting rFVIIIFc may be more effective in tolerizing HA patients with anti-FVIII inhibitors compared to FVIII not linked to Fc. Our in vitro findings suggest a potential use of Fc-fusion proteins acting via NK cells to target antigen-specific B-cells, in the management of unwanted immune responses directed against immunogenic self-antigens or therapeutic protein products.

Low number of KIR ligands in lymphoma patients favors a good rituximab-dependent NK cell response

The antibody-dependent cellular cytotoxicity (ADCC) effector function of natural killer (NK) cells is one of the known mechanisms of action for rituximab-based anti-cancer immunotherapy. Inhibition of the ADCC function of NK cells through interactions between inhibitory killer cell immunoglobulin-like receptors (KIRs) and HLA class I ligands is associated with resistance of cancers to rituximab. In this study, we deeply investigated the impact of KIR, HLA class I, and CD16 genotypes on rituximab-dependent NK cell responses in both an in vitro cellular model from healthy blood donors and ex vivo rituximab-treated non-Hodgkin lymphoma (NHL) patients. We highlight that an HLA environment with limited KIR ligands is beneficial to promoting a higher frequency of KIR⁺ NK cells including both educated and uneducated NK cells, two NK cell compartments that demonstrate higher rituximab-dependent degranulation than KIR⁻ NK cells. In contrast, a substantial KIR ligand environment favors a higher frequency of poorly effective KIR⁻ NK cells and numerous functional KIR/HLA inhibitions of educated KIR⁺ NK cells. These phenomena explain why NHL patients with limited KIR ligands respond better to rituximab. In this HLA environment, CD16 polymorphism appears to have a collateral effect. Furthermore, we show the synergic effect of KIR2DS1, which strongly potentiates NK cell ADCC from C2⁻ blood donors against C2⁺ target cells. Taken together, these results pave the way for stronger prediction of rituximab responses for NHL patients. HLA class I typing and peripheral blood KIR⁺ NK cell frequency could be simple and useful markers for predicting rituximab response.

T cells, particularly activated CD4+ cells, maintain anti-CD20-mediated NK cell viability and antibody dependent cellular cytotoxicity

Anti-CD20 monoclonal antibody (mAb) therapy is a mainstay of therapy for B cell malignancies, however many patients fail to respond or eventually develop resistance. The current understanding of mechanisms responsible for this resistance is limited. When peripheral blood mononuclear cells of healthy donors were cultured with Raji cells for 7 days, rituximab (RTX) induced NK cell-mediated antibody-dependent cellular cytotoxicity (ADCC), enhanced NK cell viability and increased or maintained NK expression of CD56, CD16, CD57 and KIR. T cells, mainly CD4⁺, mediated these changes in a contact-dependent manner, with local T cell production of IL2 playing a central role. Similar findings were found when autologous B cells were used as target cells demonstrating the need for T cell help was not due to allogenic reaction. Results with other anti-CD20 and anti-EGFR antibodies were consistent. Small numbers of T cells activated by anti-CD3/CD28 beads or bispecific antibody enhanced RTX-mediated NK cell ADCC, viability and phenotypical changes. Pathway analysis of bulk NK cell mRNA sequencing after activation by RTX with and without T cells was consistent with T cells maintaining the viability of the activated NK cells. These findings suggest T cell help, mediated in large part by local production of IL2, contributes to NK cell ADCC and viability, and that activating T cells in the tumor microenvironment, such as through the use of anti-CD3 based bispecific antibodies, could enhance the efficacy of anti-CD20 and other mAb therapies where NK-mediated ADCC is a primary mechanism of action.

Addition of BTK inhibitor orelabrutinib to rituximab improved anti-tumor effects in B cell lymphoma

Bruton tyrosine kinase (BTK) inhibitor ibrutinib has been validated as an effective drug to treat B cell malignancies. Combined therapies comprising ibrutinib and anti-CD20 antibodies like rituximab were designed as a backbone in many clinical trials. However, the off-target inhibition of ibrutinib on interleukin-2 (IL-2)-inducible T cell kinase (ITK) may reduce rituximab's antibody-dependent cellular cytotoxicity (ADCC) efficacy. Orelabrutinib (Orel), a novel BTK inhibitor, was designed with high selectivity to BTK. In our study, we demonstrated in preclinical models that orelabrutinib in combination with rituximab could preserve NK-cell-mediated ADCC induced by rituximab and enhanced the apoptosis of tumor cells in vitro. The addition of orelabrutinib to rituximab had produced promising combined anti-tumor effects in B cell lymphomas in vivo. Collectively, combination therapy of orelabrutinib with rituximab would benefit patients with B cell lymphoma, especially those with relapsed or refractory disease.

Targeting NK Cells to Enhance Melanoma Response to Immunotherapies

Natural killer (NK) cells are a key component of an innate immune system. They are important not only in initiating, but also in augmenting adaptive immune responses. NK cell activation is mediated by a carefully orchestrated balance between the signals from inhibitory and activating NK cell receptors. NK cells are potent producers of proinflammatory cytokines and are also able to elicit strong antitumor responses through secretion of perforin and granzyme B. Tumors can develop many mechanisms to evade NK cell antitumor responses, such as upregulating ligands for inhibitory receptors, secreting anti-inflammatory cytokines and recruiting immunosuppressive cells. Enhancing NK cell responses will likely augment the effectiveness of immunotherapies, and strategies to accomplish this are currently being evaluated in clinical trials. A comprehensive understanding of NK cell biology will likely provide additional opportunities to further leverage the antitumor effects of NK cells. In this review, we therefore sought to highlight NK cell biology, tumor evasion of NK cells and clinical trials that target NK cells.

Immune checkpoint markers and anti-CD20-mediated NK cell activation

Anti-CD20 mAb is an effective therapy for most B-cell malignancies. Checkpoint blockade has been used to enhance T-cell-mediated antitumor response. Little is known about the biologic significance of immune checkpoints expressed by NK cells in anti-CD20-based therapy. To investigate the role of checkpoints in anti-CD20-mediated NK cell biology, Raji B-cell lymphoma cells, and PBMCs from normal donors were cocultured with rituximab (RTX), obinutuzumab (OBZ), or trastuzumab as a control mAb for between 20 h and 9 d. RTX and OBZ induced a dose-dependent NK cell up-regulation of T-cell immunoreceptor with Ig and ITIM domain (TIGIT) and T-cell immunoglobulin mucin-3 (TIM3), but not PD1, CTLA4, or LAG3. Resting CD56^dim NK had higher TIGIT and TIM3 expression than resting CD56^bright NK although TIGIT and TIM3 were up-regulated on both subsets. NK cells with the CD16 158VV single nucleotide polymorphism had greater TIM3 up-regulation than did NK from VF or FF donors. TIGIT⁺ and TIM3⁺ NK cells degranulated, produced cytokines, and expressed activation markers to a greater degree than did TIGIT^- or TIM3^- NK cells. Blockade of TIGIT, TIM3, or both had little impact on RTX-induced NK cell proliferation, degranulation, cytokine production, or activation. Taken together, TIGIT and TIM3 can serve as markers for anti-CD20-mediated NK cell activation, but may not serve well as targets for enhancing the anti-tumor activity of such therapy.

Natural Killer cells and monoclonal antibodies: Two partners for successful antibody dependent cytotoxicity against tumor cells

Monoclonal antibodies targeting tumors are one of the most important discoveries in the field of cancer. Although several effective antibodies have been developed, a relapse may occur. One of their mechanisms of action is Antibody Dependent Cell Cytotoxicity (ADCC), by engaging the Fc γ receptor CD16 expressing Natural Killer cells, innate lymphoid cells involved in cancer immunosurveillance and able to kill tumor cells. A lack of NK cells observed in many cancers may therefore be a cause of the low efficacy of antibodies observed in some clinical situations. Here we review clear evidences of the essential partnership between NK cells and antibodies showed in vitro, in vivo, and in clinical trials in different indications, describe the hurdles and ways to enhance ADCC and the evolution of monoclonal antibody therapy. NK cell adoptive immunotherapy combined with monoclonal antibodies may overcome the resistance to the treatment and enhance their efficacy.

Role of the Main Non HLA-Specific Activating NK Receptors in Pancreatic, Colorectal and Gastric Tumors Surveillance

Human NK cells can control tumor growth and metastatic spread thanks to their powerful cytolytic activity which relies on the expression of an array of activating receptors. Natural cytotoxicity receptors (NCRs) NKG2D and DNAM-1 are those non-HLA-specific activating NK receptors that are mainly involved in sensing tumor transformation by the recognition of different ligands, often stress-induced molecules, on the surface of cancer cells. Tumors display several mechanisms aimed at dampening/evading NK-mediated responses, a relevant fraction of which is based on the downregulation of the expression of activating receptors and/or their ligands. In this review, we summarize the role of the main non-HLA-specific activating NK receptors, NCRs, NKG2D and DNAM-1, in controlling tumor growth and metastatic spread in solid malignancies affecting the gastrointestinal tract with high incidence in the world population, i.e., pancreatic ductal adenocarcinoma (PDAC), colorectal cancer (CRC), and gastric cancer (GC), also describing the phenotypic and functional alterations induced on NK cells by their tumor microenvironment.

Specificity and effector functions of non-neutralizing gB-specific monoclonal antibodies isolated from healthy individuals with human cytomegalovirus infection

Human cytomegalovirus (HCMV) is the most common congenital infection. A glycoprotein B (gB) subunit vaccine (gB/MF59) is the most efficacious clinically tested to date, having achieved 50% protection against primary infection of HCMV-seronegative women. We previously identified that gB/MF59 vaccination primarily elicits non-neutralizing antibody responses, with variable binding to gB genotypes, and protection associated with binding to membrane-associated gB. We hypothesized that gB-specific non-neutralizing antibody binding breadth and function are dependent on epitope and genotype specificity, and ability to interact with membrane-associated gB. We mapped twenty-four gB-specific monoclonal antibodies (mAbs) from naturally HCMV-infected individuals for gB domain specificity, genotype preference, and ability to mediate phagocytosis or NK cell activation. gB-specific mAbs were primarily specific for Domain II and demonstrated variable binding to gB genotypes. Two mAbs facilitated phagocytosis with binding specificities of Domain II and AD2. This investigation provides novel understanding on the relationship between gB domain specificity and antigenic variability on gB-specific antibody effector functions.

Mechanism of tumor cells escaping from immune surveillance of NK cells

Natural killer (NK) cells play an important role in anti-tumor and anti-infection, and perform their immune surveillance function in various ways. However, no matter what kind of cancer, the functional activity of NK cells in the tumor microenvironment (TME) is suppressed. Understanding the relationship between tumor cells and NK cells is very critical for tumor immunotherapy. This review discusses the mechanism of tumor cells escaping the immune surveillance of NK cells. These include a variety of factors that inhibit the activity of NK cells, an imbalance of activating receptors and inhibiting receptors on NK cells, abnormal binding of receptors and ligands, cross-talk of surrounding cell groups and NK cells in the TME, and other factors that affect NK cell activity. An understanding of these factors is necessary to provide new treatment strategies for tumor immunotherapy.

Macromolecules and Antibody-Based Drugs

Macromolecule drugs particularly antibody drugs are very powerful therapies developing rapidly in the recent 20 years, providing hopes for many patients diagnosed with "incurable" diseases in the past. They also provide more effective and less side effects for many afflicting diseases, and greatly improve the survival rate and life quality of patients. In the last two decades, the proportion of US Food and Drug Administration (FDA) approved macromolecules and antibody drugs are increasing quickly, especially after the discovery of immune checkpoints. To crown all, the 2017 Nobel prize in physiology or medicine was given to immunotherapy. In this chapter, we would like to summarize the current situation of macromolecule and antibody drugs, and what effort scientists and pharmaceutical industry have made to discover and manufacture better antibody drugs.

Expression of carcinoma, apoptosis, and cell-death-related genes are determinants for sensitivity of pediatric cancer cell lines to lysis by natural killer cells

Natural killer (NK) cells have potential utility in pediatric cancer immunotherapy for their ability to lyse diverse tumor targets, lack of dependence on mutation-associated tumor antigens, and for their relative safety demonstrated so far in clinical trials. Here, we evaluate the cytotoxic potential of expanded NK cells against a well-characterized panel of pediatric cancer cell lines representing Ewing sarcoma, rhabdomyosarcoma, neuroblastoma, lymphoma, leukemia, and brain tumors. We correlate their sensitivity NK cell lysis with tumor phenotypic, transcriptomic, and genetic determinants, and correlate known immunogenetic determinants with donor NK cell potency. Although ligand expression on cell lines stratified according to hematologic versus nonhematologic cancer types, the sensitivity to NK cell lysis varied widely and did not correlate with cancer type, expression of individual activating or inhibitory ligands, gene-expression clusters of NK cell ligands, disease status (newly diagnosed or relapsed), or MYCN amplification. Rather, sensitivity to NK cell-mediated lysis was associated with a novel 96-gene cluster of predominantly carcinoma-, apoptosis-, and cell death-related pathways, and with functional p53 status. NK cell potency was strongly associated with activating KIR gene content, but not with KIR/KIR-ligand mismatch. This study suggests that adoptive immunotherapy with expanded NK cells has the potential for a wide range of pediatric cancers, identifies potential biomarkers of efficacy and response, and establishes a foundation for using this cell line panel for the preclinical evaluation of immunotherapies.

Systemic and Intra-Nodal Activation of NK Cells After Rituximab Monotherapy for Follicular Lymphoma

Monotherapy with the anti-CD20 monoclonal antibody rituximab can induce complete responses (CR) in patients with follicular lymphoma (FL). Resting FcRγIII⁺ (CD16⁺) natural killer (NK) cells respond strongly to rituximab-coated target cells in vitro. Yet, the contribution of NK cells in the therapeutic effect in vivo remains unknown. Here, we followed the NK cell repertoire dynamics in the lymph node and systemically during rituximab monotherapy in patients with FL. At baseline, NK cells in the tumor lymph node had a naïve phenotype albeit they were more differentiated than NK cells derived from control tonsils as determined by the frequency of CD56^dim NK cells and the expression of killer cell immunoglobulin-like receptors (KIR), CD57 and CD16. Rituximab therapy induced a rapid drop in NK cell numbers coinciding with a relative increase in the frequency of Ki67⁺ NK cells both in the lymph node and peripheral blood. The Ki67⁺ NK cells had slightly increased expression of CD16, CD57 and higher levels of granzyme A and perforin. The in vivo activation of NK cells was paralleled by a temporary loss of in vitro functionality, primarily manifested as decreased IFNγ production in response to rituximab-coated targets. However, patients with pre-existing NKG2C⁺ adaptive NK cell subsets showed less Ki67 upregulation and were refractory to the loss of functionality. These data reveal variable imprints of rituximab monotherapy on the NK cell repertoire, which may depend on pre-existing repertoire diversity.

In Situ Modification of the Tumor Cell Surface with Immunomodulating Nanoparticles for Effective Suppression of Tumor Growth in Mice

Current cancer immunotherapies including chimeric antigen receptor (CAR)-based therapies and checkpoint immune inhibitors have demonstrated significant clinical success, but always suffer from immunotoxicity and autoimmune disease. Recently, nanomaterial-based immunotherapies are developed to precisely control in vivo immune activation in tumor tissues for reducing immune-related adverse events. However, little consideration has been put on the spatial modulation of interactions between immune cells and cancer cells to optimize the efficacy of cancer immunotherapies. Herein, a rational design of immunomodulating nanoparticles is demonstrated that can in situ modify the tumor cell surface with natural killer cell (NK cell)-activating signals to achieve in situ activation of tumor-infiltrating NK cells, as well as direction of their antitumor immunity toward tumor cells. Using these immunomodulating nanoparticles, the remarkable inhibition of tumor growth is observed in mice without noticeable side effects. This study provides an accurate immunomodulation strategy that achieves safe and effective antitumor immunity through in situ NK cell activation in tumors. Further development by constructing interactions with various immune cells can potentially make this nanotechnology become a general platform for the design of advanced immunotherapies for cancer treatments.

Anti-CD137 monoclonal antibody enhances trastuzumab-induced, natural killer cell-mediated cytotoxicity against pancreatic cancer cell lines with low human epidermal growth factor-like receptor 2 expression

Because human epidermal growth factor-like receptor (HER) 2 is expressed on the surface of human pancreatic carcinoma cells to varying degrees, trastuzumab, an anti-HER2 monoclonal antibody (mAb), is expected to exert antibody-dependent, natural killer (NK) cell-mediated cytotoxicity (ADCC) against the cells. However, some reports found that the effect of trastuzumab against human pancreatic carcinoma cells was limited because most express only limited HER2. We examined whether anti-CD137 stimulating mAb could enhance trastuzumab-mediated ADCC against Panc-1, a human pancreatic cancer cell line with low HER2 expression, in vitro. Supplementation of anti-CD137 mAb could improve trastuzumab-mediated ADCC against Panc-1 which was insufficient without this stimulating antibody. The ADCC differed in individual cells, and this was related to the expression of CD137 on the surface of NK cells after trastuzumab stimulation in association with the Fcγ-RIIIA polymorphism. NK cells with Fcγ-RIIIA-VV/VF showed high levels of ADCC against Panc-1, but those with Fcγ-RIIIA-FF did not show optimal ADCC. In addition, trastuzumab-mediated ADCC against the human pancreatic cancer cell line Capan-1 with high HER2 expression was generally high and not affected by the Fcγ-RIIIA polymorphism. These results demonstrated that in Fcγ-RIIIA-VV/VF-carrying healthy individuals, trastuzumab plus αCD137 mAb could induce effective ADCC against HER2-low-expressing pancreatic cancer cell lines, and that such an approach may result in similar findings in patients with pancreatic cancer.

A comprehensive overview of FCGR3A gene variability by full-length gene sequencing including the identification of V158F polymorphism

The FCGR3A gene encodes for the receptor important for antibody-dependent natural killer cell-mediated cytotoxicity. FCGR3A gene polymorphisms could affect the success of monoclonal antibody therapy. Although polymorphisms, such as the FcγRIIIA-V158F and -48L/R/H, have been studied extensively, an overview of other polymorphisms within this gene is lacking. To provide an overview of FCGR3A polymorphisms, we analysed the 1000 Genomes project database and found a total of 234 polymorphisms within the FCGR3A gene, of which 69%, 16%, and 15% occur in the intron, UTR, and exon regions respectively. Additionally, only 16% of all polymorphisms had a minor allele frequency (MAF) > 0.01. To facilitate (full-length) analysis of FCGR3A gene polymorphism, we developed a FCGR3A gene-specific amplification and sequencing protocol for Sanger sequencing and MinION (Nanopore Technologies). First, we used the Sanger sequencing protocol to study the presence of the V158F polymorphism in 76 individuals resulting in frequencies of 38% homozygous T/T, 7% homozygous G/G and 55% heterozygous. Next, we performed a pilot with both Sanger sequencing and MinION based sequencing of 14 DNA samples which showed a good concordance between Sanger- and MinION sequencing. Additionally, we detected 13 SNPs listed in the 1000 Genome Project, from which 11 had MAF > 0.01, and 10 SNPs were not listed in 1000 Genome Project. In summary, we demonstrated that FCGR3A gene is more polymorphic than previously described. As most novel polymorphisms are located in non-coding regions, their functional relevance needs to be studied in future functional studies.

Anti-CD20 Blocker Rituximab in Kidney Transplantation

Rituximab is a chimeric anti-CD20 monoclonal protein used in various clinical scenarios in kidney transplant recipients. However, its evidence-based use there remains limited due to lack of controlled studies, limited sample size, short follow-up and poorly defined endpoints. Rituximab is indicated for CD20+ posttransplant lymphoproliferative disorder. It may be beneficial for treating recurrent membranous nephropathy and recurrent allograft antineutrophilic cytoplasmic antibody vasculitis and possibly for recurrent focal segmental glomerulosclerosis. Rituximab, in combination with IVIg/plasmapheresis, appears to decrease antibody level and increase the odds of transplantation in sensitized recipients. The role of Rituximab in ABOi transplant remains unclear, as similar outcomes are achieved without its use. Rituximab is not efficacious in antibody-mediated rejection/chronic antibody-mediated rejection. Strict randomized control trials are necessary to elucidate its true role in these settings.

FcγRIIIa-dependent IFN-γ release in whole blood assay is predictive of therapeutic IgG1 antibodies safety

Immunomodulatory monoclonal IgG1 antibodies developed for cancer and autoimmune disease have an inherent risk of systemic release of pro-inflammatory cytokines. In vitro cytokine release assays are currently used to predict cytokine release syndrome (CRS) risk, but the validation of these preclinical tools suffers from the limited number of characterized CRS-inducing IgG1 antibodies and the poor understanding of the mechanisms regulating cytokine release. Here, we incubated human whole blood from naïve healthy volunteers with four monoclonal IgG1 antibodies with different proven or predicted capacity to elicit CRS in clinic and measured cytokine release using a multiplex assay. We found that, in contrast to anti-CD52 antibodies (Campath-1H homolog) that elicited high level of multiple inflammatory cytokines from human blood cells in vitro, other IgG1 antibodies with CRS-inducing potential consistently induced release of a single tested cytokine, interferon (IFN)-γ, with a smaller magnitude than Campath. IFN-γ expression was observed as early as 2-4 h after incubation, mediated by natural killer cells, and dependent upon tumor necrosis factor and FcγRIII. Importantly, the magnitude of the IFN-γ response elicited by IgG1 antibodies with CRS-inducing potential was determined by donor FcγRIIIa-V158F polymorphism. Overall, our results highlight the importance of FcγRIIIa-dependent IFN-γ release in preclinical cytokine release assay for the prediction of CRS risk associated with therapeutic IgG1 antibodies.

Tumor-infiltrating lymphocytes predict prognosis of breast cancer patients treated with anti-Her-2 therapy

PURPOSE

Infiltration of tumor associated lymphocytes and count of its different phenotypes are potentially new independent predictor of prognosis in breast cancer. However, research related to it is less reported in breast cancer patients treated with anti-Her-2 therapy. Thus, we evaluated the relationship between survival and tumor infiltrating lymphocytes including its different phenotypes in tumors of such patients.

METHODS

Between 1999 and 2010, 98 patients diagnosed with primary breast cancer and treated with anti-Her-2 therapy at Sun-Yat-Sen University Cancer Center were included in the study. Biopsy specimens were collected post-operation but before chemotherapy. Tumor infiltrating lymphocytes as well as its FOXP3+, CD68+, IL-17+ phenotypes in both intratumoral and stromal sites and expression of FOXP3 in cancer cells were assessed.

RESULTS

Median follow-up time of 98 patients was 83.3 months (range 7.4-201 months). It suggested that patients with high stromal infiltration of TILs, lower count of FOXP3+ Tregs and CD68+ Mφ in stromal site, and high expression of FOXP3 in cancer cells had longer survival of OS. In multivariate Cox regression analysis, high count of intratumoral CD68+ Mφ [HR: 2.70 (1.00-7.31); p=0.050] and high expression of FOXP3 in cancer cells [HR: 0.29 (0.09-0.91); p=0.034] were independent prognostic factors for overall survival.

CONCLUSIONS

Tumor infiltrating lymphocytes as well as its FOXP3+, CD68+ phenotypes in stromal site, and expression of FOXP3 in cancer cells were significantly associated with OS, suggesting that they can be used as important pathological factor predicting prognosis of breast cancer patients treated with anti-Her-2 therapy.

FOXO1 promotes resistance of non-Hodgkin lymphomas to anti-CD20-based therapy

Diminished overall survival rate of non-Hodgkin lymphoma (NHL) patients treated with a combination regimen of rituximab, cyclophosphamide, doxorubicin, vincristine and prednisone (R-CHOP) has been recently linked to recurrent somatic mutations activating FOXO1. Despite of the clinical relevance of this finding, the molecular mechanism driving resistance to R-CHOP therapy remains largely unknown. Herein, we investigated the potential role of FOXO1 in the therapeutic efficacy of rituximab, the only targeted therapy included in the R-CHOP regimen. We found CD20 transcription is negatively regulated by FOXO1 in NHL cell lines and in human lymphoma specimens carrying activating mutations of FOXO1. Furthermore, both the expression of exogenous mutants of FOXO1 and the inhibition of AKT led to FOXO1 activation in lymphoma cells, increased binding to MS4A1 promoter and diminished CD20 expression levels. In contrast, a disruption of FOXO1 with CRISPR/Cas9 genome-editing (sgFOXO1) resulted in CD20 upregulation, improved the cytotoxicity induced by rituximab and the survival of mice with sgFOXO1 tumors. Accordingly, pharmacological inhibition of FOXO1 activity in primary samples upregulated surface CD20 levels. Importantly, FOXO1 was required for the downregulation of CD20 levels by the clinically tested inhibitors of BTK, SYK, PI3K and AKT. Taken together, these results indicate for the first time that the AKT-unresponsive mutants of FOXO1 are important determinant of cell response to rituximab-induced cytotoxicity, and suggest that the genetic status of FOXO1 together with its transcriptional activity need further attention while designing anti-CD20 antibodies based regimens for the therapy of pre-selected lymphomas.

Frequency analysis of the g.7081T>G/A and g.10872T>G polymorphisms in the FCGR3A gene (CD16A) using nested PCR and their functional specific effects

Polymorphic variants p.66L>R/H (g.7081T>G/A; rs10127939) and p.176F>V (g.10872T>G; rs396991) in FCGR3A (CD16A) have been associated with defects in cytotoxic function of natural killer (NK) cells in humans. Genotyping of these variants in genomic DNA has been ambiguous because of high degree of homology between FCGR3A and FCGR3B. We designed a strategy to genotype these polymorphisms and to evaluate their effects on NK cells' cytotoxic activity. One hundred and fifteen individuals from different geographical regions of Colombia were included. Specific primers were designed to amplify FCGR3A exons 4 and 5 encompassing g.7081T>G/A and g.10872T>G by long-range and nested polymerase chain reaction and sequencing. The binding of different monoclonal antibodies to CD16A and NK antibody-dependent cellular cytotoxicity (ADCC) were evaluated. We demonstrate that amplifying and sequencing FCGR3A allows genotyping of g.7081T>G/A and g.10872T>G without interference from FCGR3B. Allele frequencies in our population were as follows: 7081T = 0.895, 7081G = 0.065, 7081 A = 0.039, 10872T = 0.673, and 10872G = 0.326. We also observed linkage disequilibrium between variants 7081T and 10872G. Interestingly, 176FF variant affected the reactivity of MEM154 monoclonal antibody against CD16A, but it did not affect ADCC. Our studies aimed to determine whether clinical association exists between these polymorphisms and NK cell function defects in patients with compatible phenotypes.

An exploratory, open-label, randomized, multicenter study to investigate the pharmacodynamics of a glycoengineered antibody (imgatuzumab) and cetuximab in patients with operable head and neck squamous cell carcinoma

BACKGROUND

In addition to inhibiting epidermal growth factor receptor (EGFR) signaling, anti-EGFR antibodies of the IgG1 'subtype' can induce a complementary therapeutic effect through the induction of antibody-dependent cell-mediated cytotoxicity (ADCC). Glycoengineering of therapeutic antibodies increases the affinity for the Fc-gamma receptor, thereby enhancing ADCC.

PATIENTS AND METHODS

We investigated the changes in immune effector cells and EGFR pathway biomarkers in 44 patients with operable, advanced stage head and neck squamous cell carcinoma treated with two preoperative doses of either glycoengineered imgatuzumab (GA201; 700 or 1400 mg) or cetuximab (standard dosing) in a neoadjuvant setting with paired pre- and post-treatment tumor biopsies.

RESULTS

Significant antitumor activity was observed with both antibodies after just two infusions. Metabolic responses were seen in 23 (59.0%) patients overall. One imgatuzumab-treated patient (700 mg) achieved a 'pathological' complete response. An immediate and sustained decrease in peripheral natural killer cells was consistently observed with the first imgatuzumab infusion but not with cetuximab. The functionality of the remaining peripheral natural killer cells was maintained. Similarly, a pronounced increase in circulating cytokines was seen following the first infusion of imgatuzumab but not cetuximab. Overall, tumor-infiltrating CD3+ cell counts increased following treatment with both antibodies. A significant increase from baseline in CD3+/perforin+ cytotoxic T cells occurred only in the 700-mg imgatuzumab group (median 95% increase, P < 0.05). The most prominent decrease of EGFR-expressing cells was recorded after treatment with imgatuzumab (700 mg, -34.6%; 1400 mg, -41.8%). The post-treatment inflammatory tumor microenvironment was strongly related to baseline tumor-infiltrating immune cell density, and baseline levels of EGFR and pERK in tumor cells most strongly predicted therapeutic response.

CONCLUSIONS

These pharmacodynamic observations and relationship with efficacy are consistent with the proposed mode of action of imgatuzumab combining efficient EGFR pathway inhibition with ADCC-related immune antitumor effects.

CLINICAL TRIAL REGISTRATION NUMBER

NCT01046266 (ClinicalTrials.gov).

Enavatuzumab, a Humanized Anti-TWEAK Receptor Monoclonal Antibody, Exerts Antitumor Activity through Attracting and Activating Innate Immune Effector Cells

Enavatuzumab is a humanized IgG1 anti-TWEAK receptor monoclonal antibody that was evaluated in a phase I clinical study for the treatment of solid malignancies. The current study was to determine whether and how myeloid effector cells were involved in postulated mechanisms for its potent antitumor activity in xenograft models. The initial evidence for a role of effector cells was obtained in a subset of tumor xenograft mouse models whose response to enavatuzumab relied on the binding of Fc of the antibody to Fcγ receptor. The involvement of effector cells was further confirmed by immunohistochemistry, which revealed strong infiltration of CD45⁺ effector cells into tumor xenografts in responding models, but minimal infiltration in nonresponders. Consistent with the xenograft studies, human effector cells preferentially migrated toward in vivo-responsive tumor cells treated by enavatuzumab in vitro, with the majority of migratory cells being monocytes. Conditioned media from enavatuzumab-treated tumor cells contained elevated levels of chemokines, which might be responsible for enavatuzumab-triggered effector cell migration. These preclinical studies demonstrate that enavatuzumab can exert its potent antitumor activity by actively recruiting and activating myeloid effectors to kill tumor cells. Enavatuzumab-induced chemokines warrant further evaluation in clinical studies as potential biomarkers for such activity.

Sudan ebolavirus long recovered survivors produce GP-specific Abs that are of the IgG1 subclass and preferentially bind FcγRI

Ebolavirus is a highly lethal pathogen, causing a severe hemorrhagic disease with a high fatality rate. To better understand immune correlates of protection by virus specific IgG, we investigated the evolution of the Fcγ receptors (FcγRs)-activating capabilities of antiviral IgG in serum samples of long recovered survivors. To this end, longitudinal serum samples from survivors of Sudan ebolavirus (SUDV) infection, studied over years, were examined for the presence of Ebola-GP specific IgG subclasses, and for their binding to FcγRs. We developed a cell-based reporter system to quantitate pathogen-specific antibody binding to FcγRIIIA, FcγRIIA, FcγRIIB and FcγRI. With this system, we demonstrate that anti-GP-specific stimulation of the FcγRI reporter by survivors’ sera was substantially high one year after acute infection, with a slight reduction in activity over a decade post infection. We further demonstrate that GP-specific IgG1 is by far the seroprevalent subclass that retained and even enhanced its presence in the sera, over ten years post infection; the prevalence of other GP-specific IgG subclasses was considerably reduced over time. In accordance, GP-specific FcγRI reporter response and GP-specific total IgG1 subclass correlated in the studied group of Ebola survivors. These observations are important for further informing Ebola vaccine and therapeutic development.

Nimotuzumab Induces NK Cell Activation, Cytotoxicity, Dendritic Cell Maturation and Expansion of EGFR-Specific T Cells in Head and Neck Cancer Patients

Survival benefit and long-term duration of clinical response have been seen using the epidermal growth factor receptor (EGFR)-targeted monoclonal antibody (mAb) nimotuzumab. Blocking EGFR signaling may not be the only mechanism of action underlying its efficacy. As an IgG1 isotype mAb, nimotuzumab's capacity of killing tumor cells by antibody dependent cellular cytotoxicity (ADCC) and to induce an immune response in cancer patients have not been studied. ADCC-induced by nimotuzumab was determined using a ⁵¹Cr release assay. The in vitro effect of nimotuzumab on natural killer (NK) cell activation and dendritic cell (DC) maturation and the in vivo frequency of circulating regulatory T cells (Tregs) and NK cells were assessed by flow cytometry. Cytokine levels in supernatants were determined by ELISA. ELISpot was carried out to quantify EGFR-specific T cells in nimotuzumab-treated head and neck cancer (HNSCC) patients. Nimotuzumab was able to kill EGFR+ tumor cells by NK cell-mediated ADCC. Nimotuzumab-activated NK cells promoted DC maturation and EGFR-specific CD8+ T cell priming. Interestingly, nimotuzumab led to upregulation of some immune checkpoint molecules on NK cells (TIM-3) and DC (PD-L1), to a lower extent than another EGFR mAb, cetuximab. Furthermore, circulating EGFR-specific T cells were identified in nimotuzumab-treated HNSCC patients. Notably, nimotuzumab combined with cisplatin-based chemotherapy and radiation increased the frequency of peripheral CD4+CD39+FOXP3+Tregs which otherwise were decreased to baseline values when nimotuzumab was used as monotherapy. The frequency of circulating NK cells remained constant during treatment. Nimotuzumab-induced, NK cell-mediated DC priming led to induction of anti-EGFR specific T cells in HNSCC patients. The association between EGFR-specific T cells and patient clinical benefit with nimotuzumab treatment should be investigated.

PD-1 blockade enhances elotuzumab efficacy in mouse tumor models

Elotuzumab, a humanized monoclonal antibody that binds human signaling lymphocytic activation molecule F7 (hSLAMF7) on myeloma cells, was developed to treat patients with multiple myeloma (MM). Elotuzumab has a dual mechanism of action that includes the direct activation of natural killer (NK) cells and the induction of NK cell-mediated antibody-dependent cellular cytotoxicity. This study aimed to characterize the effects of elotuzumab on NK cells in vitro and in patients with MM and to determine whether elotuzumab antitumor activity was improved by programmed death receptor-1 (PD-1) blockade. Elotuzumab promoted NK cell activation when added to a coculture of human NK cells and SLAMF7-expressing myeloma cells. An increased frequency of activated NK cells was observed in bone marrow aspirates from elotuzumab-treated patients. In mouse tumor models expressing hSLAMF7, maximal antitumor efficacy of a murine immunoglobulin G2a version of elotuzumab (elotuzumab-g2a) required both Fcγ receptor-expressing NK cells and CD8⁺ T cells and was significantly enhanced by coadministration of anti-PD-1 antibody. In these mouse models, elotuzumab-g2a and anti-PD-1 combination treatment promoted tumor-infiltrating NK and CD8⁺ T-cell activation, as well as increased intratumoral cytokine and chemokine release. These observations support the rationale for clinical investigation of elotuzumab/anti-PD-1 combination therapy in patients with MM.

Anti-CD20-interleukin-21 fusokine targets malignant B cells via direct apoptosis and NK-cell–dependent cytotoxicity

Delivering IL-21 to tumor B cells by fusion with anti-CD20 antibody (αCD20-IL-21 fusokine) is a potent antilymphoma therapeutic strategy. αCD20-IL-21 fusokine demonstrated superior antilymphoma activity compared with its individual components.

Obinutuzumab-mediated high-affinity ligation of FcγRIIIA/CD16 primes NK cells for IFNγ production

Natural killer (NK) cell-mediated antibody-dependent cellular cytotoxicity (ADCC), based on the recognition of IgG-opsonized targets by the low-affinity receptor for IgG FcγRIIIA/CD16, represents one of the main mechanisms by which therapeutic antibodies (mAbs) mediate their antitumor effects. Besides ADCC, CD16 ligation also results in cytokine production, in particular, NK-derived IFNγ is endowed with a well-recognized role in the shaping of adaptive immune responses. Obinutuzumab is a glycoengineered anti-CD20 mAb with a modified crystallizable fragment (Fc) domain designed to increase the affinity for CD16 and consequently the killing of mAb-opsonized targets. However, the impact of CD16 ligation in optimized affinity conditions on NK functional program is not completely understood. Herein, we demonstrate that the interaction of NK cells with obinutuzumab-opsonized cells results in enhanced IFNγ production as compared with parental non-glycoengineered mAb or the reference molecule rituximab. We observed that affinity ligation conditions strictly correlate with the ability to induce CD16 down-modulation and lysosomal targeting of receptor-associated signaling elements. Indeed, a preferential degradation of FcεRIγ chain and Syk kinase was observed upon obinutuzumab stimulation independently from CD16-V158F polymorphism. Although the downregulation of FcεRIγ/Syk module leads to the impairment of cytotoxic function induced by NKp46 and NKp30 receptors, obinutuzumab-experienced cells exhibit an increased ability to produce IFNγ in response to different stimuli. These data highlight a relationship between CD16 aggregation conditions and the ability to promote a degradative pathway of CD16-coupled signaling elements associated to the shift of NK functional program.

Antibody-Based Cancer Therapy: Successful Agents and Novel Approaches

Since their discovery, antibodies have been viewed as ideal candidates or "magic bullets" for use in targeted therapy in the fields of cancer, autoimmunity, and chronic inflammatory disorders. A wave of antibody-dedicated research followed, which resulted in the clinical approval of a first generation of monoclonal antibodies for cancer therapy such as rituximab (1997) and cetuximab (2004), and infliximab (2002) for the treatment of autoimmune diseases. More recently, the development of antibodies that prevent checkpoint-mediated inhibition of T cell responses invigorated the field of cancer immunotherapy. Such antibodies induced unprecedented long-term remissions in patients with advanced stage malignancies, most notably melanoma and lung cancer, that do not respond to conventional therapies. In this review, we will recapitulate the development of antibody-based therapy, and detail recent advances and new functions, particularly in the field of cancer immunotherapy. With the advent of recombinant DNA engineering, a number of rationally designed molecular formats of antibodies and antibody-derived agents have become available, and we will discuss various molecular formats including antibodies with improved effector functions, bispecific antibodies, antibody-drug conjugates, antibody-cytokine fusion proteins, and T cells genetically modified with chimeric antigen receptors. With these exciting advances, new antibody-based treatment options will likely enter clinical practice and pave the way toward more successful control of malignant diseases.

An Fc-optimized CD133 antibody for induction of NK cell reactivity against myeloid leukemia

Antibody-dependent cellular cytotoxicity (ADCC) of natural killer (NK) cells largely contributes to the success of monoclonal antibody (mAb) treatment in cancer. As no antibodies are clinically available for immunotherapy of myeloid leukemias (MLs), we aimed to develop an Fc-optimized CD133 mAb for induction of NK ADCC against MLs. When comparing different available CD133 mAbs, no difference was observed with regard to binding to primary chronic myeloid leukemia cells. However, clone 293C3 recognized acute myeloid leukemia (AML) cells in a substantially higher percentage of patient cases and was thus chosen to generate chimeric mAbs with either wild-type Fc part (293C3-WT) or a variant containing amino-acid exchanges (S239D/I332E) to enhance affinity to CD16 on NK cells (293C3-SDIE). In vitro, treatment with 293C3-SDIE significantly enhanced activation, degranulation and lysis of primary CD133-positive AML cells by allogeneic and autologous NK cells as compared with its wild-type counterpart. In line with the observed lower expression levels of CD133 on healthy cells compared with malignant hematopoietic cells, 293C3-SDIE caused no relevant toxicity towards committed hematopoietic progenitor cells. In a NOD.Cg-PrkdcscidIL2rgtmWjl/Sz xenotransplantation model, 293C3-SDIE facilitated elimination of patient AML cells by human NK cells. Thus, 293C3-SDIE constitutes an attractive immunotherapeutic compound, in particular for elimination of minimal residual disease in the context of allogeneic stem cell transplantation in AML.

Natural Killer Cell Receptors and Cytotoxic Activity in Phosphomannomutase 2 Deficiency (PMM2-CDG)

Background

PMM2-CDG is the most common N-glycosylation defect and shows an increased risk of recurrent and/or severe, sometimes fatal, infections in early life. We hypothesized that natural killer (NK) cells, as important mediators of the immune response against microbial pathogens and regulators of adaptive immunity, might be affected in this genetic disorder.

Objective

To evaluate possible defects on PMM2-CDG NK peripheral blood cell number, killing activity and expression of membrane receptors.

Methods

We studied fresh and activated NK cells from twelve PMM2-CDG cells. The number and expression of lymphoid surface receptors were studied by flow cytometry. The NK responsiveness (frequency of degranulated NK cells) and killing activity against K562 target cells was determined in the NK cytotoxicity assay.

Results

We found an increase of blood NK cells in three patients with a severe phenotype. Two of them, who had suffered from moderate/severe viral infections during their first year of life, also had reduced T lymphocyte numbers. Patient activated NK cells showed increased expression of CD54 adhesion molecule and NKG2D and NKp46 activating receptors. NKp46 and 2B4 expression was inversely correlated with the expression of NKG2D in activated PMM2-CDG cells. Maximal NK activity against K562 target cells was similar in control and PMM2-CDG cells. Interestingly, the NK cell responsiveness was higher in patient cells. NKG2D and specially CD54 increased surface expression significantly correlated with the increased NK cell cytolytic activity according to the modulation of the killer activity by expression of triggering receptors and adhesion molecules.

Conclusions

Our results indicate that hypoglycosylation in PMM2-CDG altered NK cell reactivity against target cells and the expression of CD54 and NKG2D, NKp46 and 2B4 activating receptors during NK cell activation. This suggests a defective control of NK cell killing activity and the overall anti-viral immune response in PMM2-CDG patients. The present work improves our understanding of the immunological functions in PMM2-CDG and possibly in other CDG-I types.

NK cells lacking FcεRIγ are associated with reduced liver damage in chronic hepatitis C virus infection

A novel subset of human natural killer (NK) cells, which displays potent and broad antiviral responsiveness in concert with virus-specific antibodies, was recently uncovered in cytomegalovirus (CMV)+ individuals. This NK-cell subset (g-NK) was characterized by a deficiency in the expression of FcεRIγ adaptor protein and the long-lasting memory-like NK-cell phenotype, suggesting a role in chronic infections. This study investigates whether the g-NK-cell subset is associated with the magnitude of liver disease during chronic hepatitis C virus (HCV) infection. Analysis of g-NK-cell proportions and function in the PBMCs of healthy controls and chronic HCV subjects showed that chronic HCV subjects had slightly lower proportions of the g-NK-cell subset having similarly enhanced antibody-dependent cellular cytotoxicity responses compared to conventional NK cells. Notably, among CMV+ chronic HCV patients, lower levels of liver enzymes and fibrosis were found in those possessing g-NK cells. g-NK cells were predominant among the CD56(neg) NK cell population often found in chronic HCV patients, suggesting their involvement in immune response during HCV infection. For the first time, our findings indicate that the presence of the g-NK cells in CMV+ individuals is associated with amelioration of liver disease in chronic HCV infection, suggesting the beneficial roles of g-NK cells during a chronic infection.

Update on Mucin-1 immunotherapy in cancer: a clinical perspective

INTRODUCTION

Mucin 1 (MUC1) is particularly well suited as a cancer immunotherapy target due to the elevated protein expression and aberrant forms associated with malignancy. A variety of therapeutic strategies have been explored, including antibodies intended to induce cancer cell destruction, and vaccinations with peptides, tumor extracts, and gene expression systems.

AREAS COVERED

MUC1 immunotherapeutic strategies have included vaccination with peptide sequences, glycan molecules, viruses, and dendritic cells, monoclonal antibodies and monoclonal antibody conjugates. Here we review the relevant clinical trials in each field of immunotherapy with particular focus on large and recently published trials.

EXPERT OPINION

Long clinical experience in the trial setting has reduced concerns of immunotherapy associated toxicities and inappropriate immune responses, with the main limitation (common to many experimental approaches) being a lack of clinical efficacy. However, there have been sufficient treatment-associated responses to justify continued pursuit of MUC1 targeted immunotherapies. The focus now should be on application to the relevant cancers under appropriate circumstances and combination with the emerging non-specific immunotherapy approaches such as the PD-1 pathway inhibitors.

The c.503T>C Polymorphism in the Human KLRB1 Gene Alters Ligand Binding and Inhibitory Potential of CD161 Molecules

Studying genetic diversity of immunologically relevant molecules can improve our knowledge on their functional spectrum in normal immune responses and may also uncover a possible role of different variants in diseases. We characterized the c.503T>C polymorphism in the human KLRB1 gene (Killer cell lectin-like receptor, subfamily B, member 1) coding for the cell surface receptor CD161. CD161 is expressed by subsets of CD4⁺ and CD8⁺ T cells and the great majority of CD56⁺ natural killer (NK) cells, acting as inhibitory receptor in the latter population. Genotyping a cohort of 118 healthy individuals revealed 40% TT homozygotes, 46% TC heterozygotes, and 14% carriers of CC. There was no difference in the frequency of CD161 expressing CD4⁺ and CD8⁺ T cells between the different genotypes. However, the frequency of CD161⁺ NK cells was significantly decreased in CC carriers as compared to TT homozygotes. c.503T>C causes an amino acid exchange (p.Ile168Thr) in an extracellular loop of the CD161 receptor, which is regarded to be involved in binding of its ligand Lectin-like transcript 1 (LLT1). Binding studies using soluble LLT1-Fc on 293 transfectants over-expressing CD161 receptors from TT or CC carriers suggested diminished binding to the CC variant. Furthermore, triggering of CD161 either by LLT1 or anti-CD161 antibodies inhibited NK cell activation less effectively in cells from CC individuals than cells from TT carriers. These data suggest that the c.503T>C polymorphism is associated with structural alterations of the CD161 receptor. The regulation of NK cell homeostasis and activation apparently differs between carriers of the CC and TT variant of CD161.

Pyrosequencing for classification of human FcγRIIIA allotypes: a comparison with PCR-based techniques

BACKGROUND

Surface-specific antigens expressed by hematopoietic cells are attractive targets for antibody-mediated immunotherapy. Monoclonal antibodies (mAbs) involve various mechanisms to eliminate target cells, including antibody-dependent cellular cytotoxicity (ADCC)- and phagocytosis (ADCP)-mediated killing through natural killer (NK) and macrophage effector cells bearing FcγRIIIA (CD16). The clinical efficacy of ADCC is particularly impacted by a single nucleotide polymorphism (SNP) found in the gene encoding FcγRIIIA (FCGR3A), which generates a variable distribution of the 158 V/V, F/V or F/F CD16 allotypes (F = phenylalanine, V = valine) in the normal human population. Currently, most patients are not screened for CD16 allotypes, creating the potential to include in their treatment a mAb-based therapy that may have limited benefit. Therefore, it is important to identify CD16 allotypes when considering mAb therapies that require ADCC/ADCP.

OBJECTIVE

The objective of this study was to develop a reliable PCR-based assay for classification of human FcγRIIIA allotypes.

METHODS

We studied 42 normal human subjects for the incidence of FcγRIIIA-158 polymorphisms using comparative molecular approaches.

RESULTS

The results of our study showed 100% accuracy in genotyping by pyrosequencing. In contrast, nested PCR-based allele-specific restriction assay and quantitative PCR techniques proved to be relatively less sensitive and less specific in distinguishing variant genotypes.

CONCLUSION

Since the efficacy of the mAb-based targeted immunotherapy may be highly dependent upon the CD16 polymorphism in a given individual, we recommend pyrosequencing for CD16 allotype testing.

Natural killer (NK) cells and anti-tumor therapeutic mAb: unexplored interactions

Tumor-targeting mAb are widely used in the treatment of a variety of solid and hematopoietic tumors and represent the first immunotherapeutic approach successfully arrived to the clinic. Nevertheless, the role of distinct immune mechanisms in contributing to their therapeutic efficacy is not completely understood and may vary depending on tumor- or antigen/antibody-dependent characteristics. Availability of next-generation, engineered, tumor-targeting mAb, optimized in their capability to recruit selected immune effectors, re-enforces the need for a deeper understanding of the mechanisms underlying anti-tumor mAb functionality. NK cells participate with a major role to innate anti-tumor responses, by exerting cytotoxic activity and producing a vast array of cytokines. As the CD16 (low-affinity FcγRIIIA)-activating receptor is expressed on the majority of NK cells, its effector functions can be ideally recruited against therapeutic mAb-opsonized tumor cells. The exact role of NK cells in determining therapeutic efficacy of tumor-targeting mAb is still unclear and much sought after. This knowledge will be instrumental to design innovative combination schemes with newly validated immunomodulatory agents. We will summarize what is known about the role of NK cells in therapeutic anti-tumor mAb therapy, with particular emphasis on RTX chimeric anti-CD20 mAb, the first one used in clinical practice for treating B cell malignancies.

Building better monoclonal antibody-based therapeutics

For 20 years, monoclonal antibodies (mAbs) have been a standard component of cancer therapy, but there is still much room for improvement. Efforts continue to build better cancer therapeutics based on mAbs. Anticancer mAbs function through various mechanisms, including directly targeting the malignant cells, modifying the host response, delivering cytotoxic moieties and retargeting cellular immunity towards the malignant cells. Characteristics of mAbs that affect their efficacy include antigen specificity, overall structure, affinity for the target antigen and how a mAb component is incorporated into a construct that can trigger target cell death. This Review discusses the various approaches to using mAb-based therapeutics to treat cancer and the strategies used to take advantage of the unique potential of each approach, and provides examples of current mAb-based treatments.

Ceramide participates in lysosome-mediated cell death induced by type II anti-CD20 monoclonal antibodies

Considering the variable and often modest therapeutic efficacy of rituximab for a substantial proportion of patients suffering from non-Hodgkin lymphomas (NHLs), various type II anti-CD20 monoclonal antibodies (mAbs) with excellent ability in inducing programmed cell death (PCD) are currently being developed for their enhanced therapeutic index. Although homotypic adhesion (HA) and lysosome leakage are proven to be of vital importance in type II mAb-induced PCD in NHL cells, the detailed relationship between them remains unclear. Herein, for the first time we discovered that improved intracellular ceramide level is an important mediator between HA and lysosome leakage in tositumomab-induced cell death. Further experimental results revealed that the generation of intracellular ceramide acts as the outcome of HA and major cause of lysosome leakage. The clarification of ceramide involvement in type II anti-CD20 mAb-induced PCD may provide new ideas on CD20-based immunotherapy against NHLs.

Analyses of CD20 monoclonal antibody-mediated tumor cell killing mechanisms: rational design of dosing strategies

Since approval of rituximab for treatment of B cell non-Hodgkin lymphoma, development of monoclonal antibodies (mAbs) for cancer treatment and elucidation of their cytotoxic mechanisms have been subject to intense investigations. Compelling evidence indicates that rituximab and another CD20 mAb, ofatumumab, must use the body's cellular and humoral immune effector functions to kill malignant cells. Other U.S. Food and Drug Administration-approved mAbs, including obinutuzumab, cetuximab, and trastuzumab, require, in part, these effector mechanisms to eliminate tumor cells. Although gram quantities of mAbs can be administered to patients, our investigations of CD20 mAb-based therapies for chronic lymphocytic leukemia (CLL), including correlative measurements in clinical trials and studies with primary cells and cell lines, indicate that effector mechanisms necessary for mAb activity can be saturated or exhausted if tumor burdens are high, thus substantially compromising the efficacy of high-dose mAb therapy. Under these conditions, another reaction (trogocytosis) predominates in which bound CD20 mAb and CD20 are removed from targeted cells by effector cells that express Fcγ receptors, thereby allowing malignant cells to escape unharmed and continue to promote disease pathology. To address this problem, we propose that a low-dose strategy, based on administering 30-50 mg of CD20 mAb three times per week, may be far more effective for CLL than standard dosing because it will minimize effector function saturation and reduce trogocytosis. This approach may have general applicability to other mAbs that use immune effector functions, and could be formulated into a subcutaneous treatment strategy that would be more accessible and possibly more efficacious for patients.

Chemoimmunotherapy for relapsed/refractory and progressive 17p13-deleted chronic lymphocytic leukemia (CLL) combining pentostatin, alemtuzumab, and low-dose rituximab is effective and tolerable and limits loss of CD20 expression by circulating CLL cells

Chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL) patients with purine analog refractory disease or TP53 dysfunction still have limited treatment options and poor survival. Alemtuzumab-containing chemoimmunotherapy regimens can be effective but frequently cause serious infections. We report a Phase II trial testing the efficacy and tolerability of a short-duration regimen combining pentostatin, alemtuzumab, and low-dose high-frequency rituximab designed to decrease the risk of treatment-associated infections and to limit the loss of CD20 expression by CLL cells. The study enrolled 39 patients with progressive CLL that was either relapsed/refractory (n = 36) or previously untreated with 17p13 deletion (17p13-) (n = 3). Thirteen (33%) patients had both 17p13- and TP53 mutations predicted to be dysfunctional, and eight patients had purine analog refractory CLL without TP53 dysfunction. Twenty-six (67%) patients completed therapy, with only five (13%) patients having treatment-limiting toxicity and no treatment-related deaths. Twenty-two (56%) patients responded to treatment, with 11 (28%) complete responses (four with incomplete bone marrow recovery). Median progression-free survival was 7.2 months, time to next treatment was 9.1 months, and overall survival was 34.1 months. The majority of deaths (82%) were caused by progressive disease, including transformed diffuse large B-cell lymphoma (n = 6). Correlative studies showed that low-dose rituximab activates complement and natural killer cells without a profound and sustained decrease in expression of CD20 by circulating CLL cells. We conclude that pentostatin, alemtuzumab, and low-dose high-frequency rituximab is a tolerable and effective therapy for CLL and that low-dose rituximab therapy can activate innate immune cytotoxic mechanisms without substantially decreasing CD20 expression.