Fc-null anti-PD-1 monoclonal antibodies deliver optimal checkpoint blockade in diverse immune environments

Impact of rheumatoid factors on the function of therapeutic monoclonals specific for PD-1/PD-L1

The efficacy of blocking antibodies against programmed death-1 (PD-1) and its ligand (PD-L1) is modulated by signalling through their Fc regions. The Fc region of anti-PD-1/PD-L1 antibodies, when cell-bound, represents a potential target for recognition by circulating rheumatoid factor (RF) autoantibodies. The resultant cell-associated immune complex may then provide different Fc signals to that of the PD-1/PD-L1 antibodies alone. However, little is known regarding the interaction of RF and therapeutic PD-1/PD-L1 antibodies. We report that PD-1 (pembrolizumab, nivolumab) and PD-L1 (avelumab) antibodies, when bound to their cellular targets, are recognised by both IgM-RF and IgA-RF components of RF+ patient serum. We further demonstrate that the presence of RF provides PD-1 antibodies with the ability to induce complement-dependent cytotoxicity (CDC) of a PD-1+ target cell line in the presence of human complement. Although RF provided avelumab with the ability to induce CDC in assays using rabbit complement, no CDC was observed in the presence of human complement. The presence of RF did not modulate the level of Fc receptor-triggered cellular cytotoxicity or neutrophil activation that was induced by PD-1/PD-L1 antibodies alone. This study demonstrates that RF has the potential to modulate the Fc-associated signals generated following binding of PD-1/PD-L1 antibodies. The impact of RF on their efficacy therefore merits further investigation.

Design of a fragment crystallizable-engineered tetravalent bispecific antibody targeting programmed cell death-1 and vascular endothelial growth factor with cooperative biological effects

Clinical studies have shown that combination therapy of PD-1 and VEGF antibodies significantly improves clinical benefit over PD-1 antibody alone in certain settings. Ivonescimab, an on-market tetravalent anti-PD-1/VEGF bispecific antibody, was designed to improve efficacy and safety over combo therapy. In this study, the mechanism of action is investigated. In the presence of VEGF, ivonescimab forms soluble complexes with VEGF dimers, leading to the enhanced binding avidity of ivonescimab to PD-1 therefore promoting its increased potency on PD-1/PD-L1-signaling blockade. Likewise, PD-1 binding enhanced ivonescimab binding to VEGF, therefore enhancing VEGF-signaling blockade. Furthermore, ivonescimab treatment demonstrated statistically significant anti-tumor response in vivo. Moreover, ivonescimab contains Fc-silencing mutations abrogating FcγRI/IIIa binding and showed significantly reduced effector function in vitro which is consistent with the better safety profile of ivonescimab in monkeys and humans. Briefly, ivonescimab displays unique cooperative binding and promotes the increased in vitro functional bioactivities with a favorable safety profile.

FcγRIIB (CD32B) antibodies enhance immune responses through activating FcγRs

Fc receptors (FcR) play a key role in coordinating responses from both the innate and adaptive immune system. The inhibitory Fc gamma receptor (FcγRIIB/CD32B; referred to as FcγRII/CD32 in mice) restrains the immune response, specifically through regulating immunoglobulin G (IgG) effector functions. FcγRII-deficient mice demonstrate elevated incidence and severity of autoimmunity and increased responses to immunization and infections. To explore the potential of FcγRIIB as a target for augmenting vaccines, we tested the ability of monoclonal antibodies (mAb) against mouse FcγRII and human FcγRIIB to enhance humoral responses in preclinical models. We used wild-type (WT), FcγR-deficient, and human FcγRIIB transgenic (Tg) mice with either a functional intracellular domain (hFcγRIIB Tg) or lacking immunoreceptor tyrosine-based inhibitory motif (ITIM) signalling capacity (NoTIM). Targeting mouse FcγRII and human FcγRIIB with antibodies significantly augmented humoral immune responses against experimental antigens and enhanced tumour clearance in vivo. Surprisingly, mAbs without a functional Fc (N297Q; referred to as Fc-null) lacked efficacy. Similarly, blocking FcγRII in mice lacking activating FcγRs failed to enhance immune responses. Conversely, blocking both signalling-competent and signalling-defective (NoTIM) FcγRIIB in Tg mice with a WT, but not Fc-null, FcγRIIB mAb equally enhanced immunity. These data indicate the redundancy of inhibitory signalling in potentiating immune responses in vivo. Collectively, our data suggest that mAb-targeting of FcγRIIB stabilizes mAb Fc and enhances immune responses via Fc-mediated crosslinking of activating FcγRs, irrespective of the inhibitory function of FcγRIIB. These findings support a strategy to boost immune responses in immunization protocols.

Enhancing EV-cell communication through "External Modulation of Cell by EV" (EMCEV)

Mesenchymal stem/stromal cells (MSC) have displayed promising therapeutic potential. Nonetheless, no United States Food and Drug Administration (FDA)-approved MSC product exists due largely to the absence of a reliable potency assay based on the mechanisms of action to ensure consistent efficacy. MSCs are now thought to exert their effects primarily by releasing small extracellular vesicles (sEVs) of 50-200 nm. While non-living MSC-sEV drugs offer distinct advantages over larger, living MSC drugs, elucidating their mechanism of action to develop robust potency assays remains a challenge. A pivotal prelude to elucidating the mechanism of action for MSC-sEVs is how extracellular vesicles (EVs) engage their primary target cells. Given the inherent inefficiencies of processes such as endocytosis, endosomal escape and EV uncoating during cellular internalization, we propose an alternative EV-cell engagement: EMCEV (Extracellular Modulation of Cells by EV). This approach involves extracellular modulation by EV attributes to generate signaling/inhibitory molecules that have the potential to affect many cells within the vicinity, thereby eliciting a more widespread tissue response.

PD-1 antibody interactions with Fc gamma receptors enable PD-1 agonism to inhibit T cell activation - therapeutic implications for autoimmunity

PD-1 has emerged as a central inhibitory checkpoint receptor in maintaining immune homeostasis and as a target in cancer immunotherapies. However, targeting PD-1 for the treatment of autoimmune diseases has been more challenging. We recently showed in a phase 2a trial that PD-1 could be stimulated with the PD-1 agonist antibody peresolimab to treat rheumatoid arthritis. Here, we demonstrate that PD-1 antibodies can elicit agonism and inhibit T cell activation by co-localization of PD-1 with the T cell receptor via Fcγ receptor (FcγR) engagement. Three PD-1 agonist antibodies with different antigen binding domains, including the clinically validated PD-1 blocking antibody pembrolizumab, suppressed T cell activation to a similar degree; this finding suggests that a specific PD-1-binding epitope is not required for PD-1 agonism. We next explored whether antibody-mediated clustering was an important driver of inhibition of T cell activation; however, we found that a monovalent PD-1 antibody was not inferior to a conventional bivalent antibody in its ability to suppress T cell activation. Importantly, we found that affinity to PD-1 correlated positively with inhibition of T cell activation, with higher affinity antibodies exhibiting higher levels of inhibition. Using a series of human Fc mutants with altered affinities to various FcγRs, we dissected the contributions of FcγRs and found that multiple FcγRs rather than a single receptor contribute to agonist activity. Our work reveals an important role for FcγR binding in the activity of PD-1 antibodies, which has implications for optimizing both PD-1 agonist and antagonist antibodies.

Inhibitory Fcγ receptor deletion enhances CD8 T cell stemness increasing anti-PD-1 therapy responsiveness against glioblastoma

BACKGROUND

Certain cancers present challenges for treatment because they are resistant to immune checkpoint blockade (ICB), attributed to low tumor mutational burden and the absence of T cell-inflamed features. Among these, glioblastoma (GBM) is notoriously resistant to ICB. To overcome this resistance, the identification of T cells with heightened stemness marked by T-cell factor 1 (TCF1) expression has gained attention. Several studies have explored ways to preserve stem-like T cells and prevent terminal exhaustion. In this study, we investigate a target that triggers stem-like properties in CD8 T cells to enhance the response to ICB in a murine GBM model.

METHODS

Using Fcgr2b-/- mice and a murine GL261 GBM model, we confirmed the efficacy of anti-programmed cell death protein-1 (PD-1) immunotherapy, observing improved survival. Analysis of immune cells using fluorescence-activated cell sorting and single-cell RNA sequencing delineated distinct subsets of tumor-infiltrating CD8 T cells in Fcgr2b-/- mice. The crucial role of the stem-like feature in the response to anti-PD-1 treatment for reinvigorating CD8 T cells was analyzed. Adoptive transfer of OT-I cells into OVA-expressing GL261 models and CD8 T cell depletion in Fcgr2b-/- mice confirmed the significance of Fcgr2b-/- CD8 T cells in enhancing the antitumor response. Last, S1P1 inhibitor treatment confirmed that the main source of tumor antigen-specific Fcgr2b-/- CD8 T cells is the tumor-draining lymph nodes (TdLNs).

RESULTS

In a murine GBM model, anti-PD-1 monotherapy and single-Fc fragment of IgG receptor IIb (FcγRIIB) deletion exhibit limited efficacy. However, their combination substantially improves survival by enhancing cytotoxicity and proliferative capacity in tumor-infiltrating Fcgr2b-/- CD8 T cells. The improved response to anti-PD-1 treatment is associated with the tumor-specific memory T cells (Ttsms) exhibiting high stemness characteristics within the tumor microenvironment (TME). Ttsms in the TdLN thrives in a protective environment, maintaining stem-like characteristics and serving as a secure source for tumor infiltration. This underscores the significance of FcγRIIB ablation in triggering Ttsms and enhancing ICB therapy against GBM.

CONCLUSIONS

Deletion of FcγRIIB on CD8 T cells leads to the generation of a Ttsms, which is localized in TdLN and protected from the immunosuppressive TME. Incorporating these highly stemness-equipped Ttsms enhances the response to anti-PD-1 therapy in immune-suppressed brain tumors.

Preclinical comparison of prolgolimab, pembrolizumab and nivolumab

Prolgolimab is a recombinant IgG1-based anti-PD-1 antibody, whose properties were improved by the introduction of the LALA mutation, and which has demonstrated high efficacy in patients with metastatic melanoma. This paper presents the results of comparative preclinical studies of antigen-binding and effector functions involving prolgolimab and conventional IgG4 antibodies, nivolumab and pembrolizumab. None of the studied antibodies had undesirable antibody-dependent cellular cytotoxicity activity. Prolgolimab has shown higher PD-1 receptor occupancy and T-cell activation, but lower propensity to activate antibody-dependent cellular phagocytosis as compared to nivolumab and pembrolizumab. An in vivo study in mice inoculated with CT26.wt cancer cells showed that tumor growth inhibition was 16% for pembrolizumab and 56% for prolgolimab. This study warrants clinical comparison of IgG1- and IgG4-based anti-PD-1 antibodies.

Current Knowledge and Perspectives of Immunotherapies for Neuroblastoma

Neuroblastoma (NBL) cells highly express disialoganglioside GD2, which is restricted and weakly expressed in selected healthy cells, making it a desirable target of immunotherapy. Over the past two decades, application of dinutuximab, an anti-GD2 monoclonal antibody (mAb), has been one of the few new therapies to substantially improve outcomes to current levels. Given the persistent challenge of relapse and therapeutic resistance, there is an urgent need for new effective and tolerable treatment options for high-risk NBL. Recent breakthroughs in immune checkpoint inhibitor (ICI) therapeutics have not translated into high-risk NBL, like many other major pediatric solid tumors. Given the suppressed tumor microenvironment (TME), single ICIs like anti-CTLA4 and anti-PD1 have not demonstrated significant antitumor response rates. Meanwhile, emerging studies are reporting novel advancements in GD2-based therapies, targeted therapies, nanomedicines, and other immunotherapies such as adoptive transfer of natural killer (NK) cells and chimeric antigen receptors (CARs), and these hold interesting promise for the future of high-risk NBL patient care. Herein, we summarize the current state of the art in NBL therapeutic options and highlight the unique challenges posed by NBL that have limited the successful adoption of immune-modifying therapies. Through this review, we aim to direct the field's attention to opportunities that may benefit from a combination immunotherapy strategy.

Impact of isotype on the mechanism of action of agonist anti-OX40 antibodies in cancer: implications for therapeutic combinations

BACKGROUND

OX40 has been widely studied as a target for immunotherapy with agonist antibodies taken forward into clinical trials for cancer where they are yet to show substantial efficacy. Here, we investigated potential mechanisms of action of anti-mouse (m) OX40 and anti-human (h) OX40 antibodies, including a clinically relevant monoclonal antibody (mAb) (GSK3174998) and evaluated how isotype can alter those mechanisms with the aim to develop improved antibodies for use in rational combination treatments for cancer.

METHODS

Anti-mOX40 and anti-hOX40 mAbs were evaluated in a number of in vivo models, including an OT-I adoptive transfer immunization model in hOX40 knock-in (KI) mice and syngeneic tumor models. The impact of FcγR engagement was evaluated in hOX40 KI mice deficient for Fc gamma receptors (FcγR). Additionally, combination studies using anti-mouse programmed cell death protein-1 (mPD-1) were assessed. In vitro experiments using peripheral blood mononuclear cells (PBMCs) examining possible anti-hOX40 mAb mechanisms of action were also performed.

RESULTS

Isotype variants of the clinically relevant mAb GSK3174998 showed immunomodulatory effects that differed in mechanism; mIgG1 mediated direct T-cell agonism while mIgG2a acted indirectly, likely through depletion of regulatory T cells (Tregs) via activating FcγRs. In both the OT-I and EG.7-OVA models, hIgG1 was the most effective human isotype, capable of acting both directly and through Treg depletion. The anti-hOX40 hIgG1 synergized with anti-mPD-1 to improve therapeutic outcomes in the EG.7-OVA model. Finally, in vitro assays with human peripheral blood mononuclear cells (hPBMCs), anti-hOX40 hIgG1 also showed the potential for T-cell stimulation and Treg depletion.

CONCLUSIONS

These findings underline the importance of understanding the role of isotype in the mechanism of action of therapeutic mAbs. As an hIgG1, the anti-hOX40 mAb can elicit multiple mechanisms of action that could aid or hinder therapeutic outcomes, dependent on the microenvironment. This should be considered when designing potential combinatorial partners and their FcγR requirements to achieve maximal benefit and improvement of patient outcomes.

Hydrogen Therapy Reverses Cancer-Associated Fibroblasts Phenotypes and Remodels Stromal Microenvironment to Stimulate Systematic Anti-Tumor Immunity

Tumor microenvironment (TME) plays an important role in the tumor progression. Among TME components, cancer-associated fibroblasts (CAFs) show multiple tumor-promoting effects and can induce tumor immune evasion and drug-resistance. Regulating CAFs can be a potential strategy to augment systemic anti-tumor immunity. Here, the study observes that hydrogen treatment can alleviate intracellular reactive oxygen species of CAFs and reshape CAFs' tumor-promoting and immune-suppressive phenotypes. Accordingly, a controllable and TME-responsive hydrogen therapy based on a CaCO3 nanoparticles-coated magnesium system (Mg-CaCO3) is developed. The hydrogen therapy by Mg-CaCO3 can not only directly kill tumor cells, but also inhibit pro-tumor and immune suppressive factors in CAFs, and thus augment immune activities of CD4+ T cells. As implanted in situ, Mg-CaCO3 can significantly suppress tumor growth, turn the "cold" primary tumor into "hot", and stimulate systematic anti-tumor immunity, which is confirmed by the bilateral tumor transplantation models of "cold tumor" (4T1 cells) and "hot tumor" (MC38 cells). This hydrogen therapy system reverses immune suppressive phenotypes of CAFs, thus providing a systematic anti-tumor immune stimulating strategy by remodeling tumor stromal microenvironment.

Fc-Fc interactions and immune inhibitory effects of IgG4: implications for anti-PD-1 immunotherapies

BACKGROUND

The majority of anti-programmed cell-death 1 (PD-1) monoclonal antibodies (mAbs) use S228P mutation IgG4 as the structural basis to avoid the activation of immune cells or complement. However, little attention has been paid to the Fc-Fc interactions between IgG4 and other IgG Fc fragments that could result in adverse effects. Fc-null IgG1 framework is a potential safer alternative to avoid the undesirable Fc-Fc interactions and Fc receptor binding derived effects observed with IgG4. This study provides a comprehensive evaluation of anti-PD-1 mAbs of these two frameworks.

METHODS

Trastuzumab and rituximab (both IgG1), wildtype IgG1 and IgG4 were immobilized on nitrocellulose membranes, coated to microplates and biosensor chips, and bound to tumor cells as targets for Fc-Fc interactions. Wildtype IgG1 and IgG4, anti-PD-1 mAb nivolumab (IgG4 S228P), penpulimab (Fc-null IgG1), and tislelizumab (Fc-null IgG4 S228P-R409K) were assessed for their binding reactions to the immobilized IgG proteins and quantitative kinetic data were obtained. To evaluate the effects of the two anti-PD-1 mAbs on immune responses mediated by trastuzumab and rituximab in the context of combination therapy, we employed classic immune models for antibody-dependent cellular cytotoxicity, antibody-dependent cellular phagocytosis, and complement dependent cytotoxicity. Tumor-bearing mouse models, both wildtype and humanized, were used for in vivo investigation. Furthermore, we also examined the effects of IgG1 and IgG4 on diverse immune cell populations RESULTS: Experiments demonstrated that wildtype IgG4 and nivolumab bound to immobilized IgG through Fc-Fc interactions, diminishing antibody-dependent cell-mediated cytotoxicity and phagocytosis reactions. Quantitative analysis of kinetic parameters suggests that nivolumab and wildtype IgG4 exhibit comparable binding affinities to immobilized IgG1 in both non-denatured and denatured states. IgG4 exerted inhibitory effects on various immune cell types. Wildtype IgG4 and nivolumab both promoted tumor growth in wildtype mouse models. Conversely, wildtype IgG1, penpulimab, and tislelizumab did not show similar adverse effects.

CONCLUSIONS

Fc-null IgG1 represents a safer choice for anti-PD-1 immunotherapies by avoiding both the adverse Fc-Fc interactions and Fc-related immune inhibitory effects of IgG4. Fc-null IgG4 S228P-R409K and Fc-null IgG1 displayed similar structural properties and benefits. This study contributes to the understanding of immunotherapy resistance and the advancement of safer immune therapies for cancer.

Evaluation of a Combinatorial Immunotherapy Regimen That Can Cure Mice Bearing MYCN-Driven High-Risk Neuroblastoma That Resists Current Clinical Therapy

Background: Incorporating GD2-targeting monoclonal antibody into post-consolidation maintenance therapy has improved survival for children with high-risk neuroblastoma. However, ~50% of patients do not respond to, or relapse following, initial treatment. Here, we evaluated additional anti-GD2-based immunotherapy to better treat high-risk neuroblastoma in mice to develop a regimen for patients with therapy-resistant neuroblastoma. Methods: We determined the components of a combined regimen needed to cure mice of established MYCN-amplified, GD2-expressing, murine 9464D-GD2 neuroblastomas. Results: First, we demonstrate that 9464D-GD2 is nonresponsive to a preferred salvage regimen: anti-GD2 with temozolomide and irinotecan. Second, we have previously shown that adding agonist anti-CD40 mAb and CpG to a regimen of radiotherapy, anti-GD2/IL2 immunocytokine and anti-CTLA-4, cured a substantial fraction of mice bearing small 9464D-GD2 tumors; here, we further characterize this regimen by showing that radiotherapy and hu14.18-IL2 are necessary components, while anti-CTLA-4, anti-CD40, or CpG can individually be removed, and CpG and anti-CTLA-4 can be removed together, while maintaining efficacy. Conclusions: We have developed and characterized a regimen that can cure mice of a high-risk neuroblastoma that is refractory to the current clinical regimen for relapsed/refractory disease. Ongoing preclinical work is directed towards ways to potentially translate these findings to a regimen appropriate for clinical testing.

Antibody Drug Clearance: An Underexplored Marker of Outcomes with Checkpoint Inhibitors

Immune-checkpoint inhibitor (ICI) therapy has dramatically changed the clinical landscape for several cancers, and ICI use continues to expand across many cancer types. Low baseline clearance (CL) and/or a large reduction of CL during treatment correlates with better clinical response and longer survival. Similar phenomena have also been reported with other monoclonal antibodies (mAb) in cancer and other diseases, highlighting a characteristic of mAb clinical pharmacology that is potentially shared among various mAbs and diseases. Though tempting to attribute poor outcomes to low drug exposure and arguably low target engagement due to high CL, such speculation is not supported by the relatively flat exposure-response relationship of most ICIs, where a higher dose or exposure is not likely to provide additional benefit. Instead, an elevated and/or increasing CL could be a surrogate marker of the inherent resistant phenotype that cannot be reversed by maximizing drug exposure. The mechanisms connecting ICI clearance, therapeutic efficacy, and resistance are unclear and likely to be multifactorial. Therefore, to explore the potential of ICI CL as an early marker for efficacy, this review highlights the similarities and differences of CL characteristics and CL-response relationships for all FDA-approved ICIs, and we compare and contrast these to selected non-ICI mAbs. We also discuss underlying mechanisms that potentially link mAb CL with efficacy and highlight existing knowledge gaps and future directions where more clinical and preclinical investigations are warranted to clearly understand the value of baseline and/or time-varying CL in predicting response to ICI-based therapeutics.

Antibody agonists trigger immune receptor signaling through local exclusion of receptor-type protein tyrosine phosphatases

Antibodies can block immune receptor engagement or trigger the receptor machinery to initiate signaling. We hypothesized that antibody agonists trigger signaling by sterically excluding large receptor-type protein tyrosine phosphatases (RPTPs) such as CD45 from sites of receptor engagement. An agonist targeting the costimulatory receptor CD28 produced signals that depended on antibody immobilization and were sensitive to the sizes of the receptor, the RPTPs, and the antibody itself. Although both the agonist and a non-agonistic anti-CD28 antibody locally excluded CD45, the agonistic antibody was more effective. An anti-PD-1 antibody that bound membrane proximally excluded CD45, triggered Src homology 2 domain-containing phosphatase 2 recruitment, and suppressed systemic lupus erythematosus and delayed-type hypersensitivity in experimental models. Paradoxically, nivolumab and pembrolizumab, anti-PD-1-blocking antibodies used clinically, also excluded CD45 and were agonistic in certain settings. Reducing these agonistic effects using antibody engineering improved PD-1 blockade. These findings establish a framework for developing new and improved therapies for autoimmunity and cancer.

Fcγ receptors and immunomodulatory antibodies in cancer

The discovery of both cytotoxic T lymphocyte-associated antigen 4 (CTLA4) and programmed cell death protein 1 (PD1) as negative regulators of antitumour immunity led to the development of numerous immunomodulatory antibodies as cancer treatments. Preclinical studies have demonstrated that the efficacy of immunoglobulin G (IgG)-based therapies depends not only on their ability to block or engage their targets but also on the antibody's constant region (Fc) and its interactions with Fcγ receptors (FcγRs). Fc-FcγR interactions are essential for the activity of tumour-targeting antibodies, such as rituximab, trastuzumab and cetuximab, where the killing of tumour cells occurs at least in part due to these mechanisms. However, our understanding of these interactions in the context of immunomodulatory antibodies designed to boost antitumour immunity remains less explored. In this Review, we discuss our current understanding of the contribution of FcγRs to the in vivo activity of immunomodulatory antibodies and the challenges of translating results from preclinical models into the clinic. In addition, we review the impact of genetic variability of human FcγRs on the activity of therapeutic antibodies and how antibody engineering is being utilized to develop the next generation of cancer immunotherapies.

Neuroblastoma: an ongoing cold front for cancer immunotherapy

Neuroblastoma is the most frequent extracranial childhood tumour but effective treatment with current immunotherapies is challenging due to its immunosuppressive microenvironment. Efforts to date have focused on using immunotherapy to increase tumour immunogenicity and enhance anticancer immune responses, including anti-GD2 antibodies; immune checkpoint inhibitors; drugs which enhance macrophage and natural killer T (NKT) cell function; modulation of the cyclic GMP-AMP synthase-stimulator of interferon genes pathway; and engineering neuroblastoma-targeting chimeric-antigen receptor-T cells. Some of these strategies have strong preclinical foundation and are being tested clinically, although none have demonstrated notable success in treating paediatric neuroblastoma to date. Recently, approaches to overcome heterogeneity of neuroblastoma tumours and treatment resistance are being explored. These include rational combination strategies with the aim of achieving synergy, such as dual targeting of GD2 and tumour-associated macrophages or natural killer cells; GD2 and the B7-H3 immune checkpoint; GD2 and enhancer of zeste-2 methyltransferase inhibitors. Such combination strategies provide opportunities to overcome primary resistance to and maximize the benefits of immunotherapy in neuroblastoma.

Levels and in vitro functional effects of circulating anti-hinge antibodies in melanoma patients receiving the immune checkpoint inhibitor pembrolizumab

The efficacy of PD-1 monoclonals such as pembrolizumab can be modulated by the signals delivered via their Fc region. Tumour/inflammation associated proteases can generate F(ab')2 fragments of therapeutic monoclonals, and subsequent recognition of F(ab')2 epitopes by circulating anti-hinge antibodies (AHA) can then, potentially, link F(ab')2 binding to the target antigen with novel Fc signalling. Although elevated in inflammatory diseases, AHA levels in cancer patients have not been investigated and functional studies utilising the full repertoire of AHA present in sera have been limited. AHA levels in pembrolizumab treated melanoma patients (n = 23) were therefore compared to those of normal donors and adalimumab treated patients. A subset of melanoma patients and the majority of adalimumab patients had elevated levels of AHA reactive with F(ab')2 fragments of IgG4 anti-PD-1 monoclonals (nivolumab, pembrolizumab) and IgG1 therapeutic monoclonals (rituximab, adalimumab). Survival analysis was restricted by the small patient numbers but those melanoma patients with the highest levels (>75% percentile, n = 5) of pembrolizumab-F(ab')2 reactive AHA had significantly better overall survival post pembrolizumab treatment (p = 0.039). In vitro functional studies demonstrated that the presence of AHA+ sera restored the neutrophil activating capacity of pembrolizumab to its F(ab')2 fragment. Neither pembrolizumab nor its F(ab')2 fragments can induce NK cell or complement dependent cytotoxicity (CDC). However, AHA+ sera in combination with pembrolizumab-F(ab')2 provided Fc regions that could activate NK cells. The ability of AHA+ sera to restore CDC activity was more restricted and observed using only one pembrolizumab and one adalimumab patient serum in combination with rituximab- F(ab')2. This study reports the presence of elevated AHA levels in pembrolizumab treated melanoma patients and highlight the potential for AHA to provide additional Fc signaling. The issue of whether tumour associated proteolysis of PD-1 mAbs and subsequent AHA recognition impacts on treatment efficacy requires further study.

Effect of posttranslational modifications and subclass on IgG activity: from immunity to immunotherapy

Humoral immune responses are characterized by complex mixtures of polyclonal antibody species varying in their isotype, target epitope specificity and affinity. Posttranslational modifications occurring during antibody production in both the antibody variable and constant domain create further complexity and can modulate antigen specificity and antibody Fc-dependent effector functions, respectively. Finally, modifications of the antibody backbone after secretion may further impact antibody activity. An in-depth understanding of how these posttranslational modifications impact antibody function, especially in the context of individual antibody isotypes and subclasses, is only starting to emerge. Indeed, only a minute proportion of this natural variability in the humoral immune response is currently reflected in therapeutic antibody preparations. In this Review, we summarize recent insights into how IgG subclass and posttranslational modifications impact IgG activity and discuss how these insights may be used to optimize therapeutic antibody development.

Combination CD200R/PD-1 blockade in a humanised mouse model

There is an increasing number of immune-checkpoint inhibitors being developed and approved for cancer immunotherapy. Most of the new therapies aim to reactivate tumour-infiltrating T cells, which are responsible for tumour killing. However, in many tumours, the most abundant infiltrating immune cells are macrophages and myeloid cells, which can be tumour-promoting as well as tumouricidal. CD200R was initially identified as a myeloid-restricted, inhibitory immune receptor, but was subsequently also found to be expressed within the lymphoid lineage. Using a mouse model humanised for CD200R and PD-1, we investigated the potential of a combination therapy comprising nivolumab, a clinically approved PD-1 blocking antibody, and OX108, a CD200R antagonist. We produced nivolumab as a murine IgG1 antibody and validated its binding activity in vitro as well as ex vivo. We then tested the combination therapy in the immunogenic colorectal cancer model MC38 as well as the PD-1 blockade-resistant lung cancer model LLC1, which is characterised by a large number of infiltrating myeloid cells, making it an attractive target for CD200R blockade. No significant improvement of overall survival was found in either model, compared to nivolumab mIgG1 monotherapy. There was a trend for more complete responses in the MC38 model, but investigation of the infiltrating immune cells failed to account for this. Importantly, MC38 cells expressed low levels of CD200, whereas LLC1 cells were CD200-negative. Further investigation of CD200R-blocking antibodies in tumours expressing high levels of CD200 could be warranted.

Fc glycoengineering of a PD-L1 antibody harnesses Fcγ receptors for increased antitumor efficacy

FDA-approved anti-PD-L1 monoclonal antibodies (mAbs) bear the IgG1 isotype, whose scaffolds are either wild-type (e.g., avelumab) or Fc-mutated and lacking Fcγ receptor (FcγR) engagement (e.g., atezolizumab). It is unknown whether variation in the ability of the IgG1 Fc region to engage FcγRs renders mAbs with superior therapeutic activity. In this study, we used humanized FcγR mice to study the contribution of FcγR signaling to the antitumor activity of human anti-PD-L1 mAbs and to identify an optimal human IgG scaffold for PD-L1 mAbs. We observed similar antitumor efficacy and comparable tumor immune responses in mice treated with anti-PD-L1 mAbs with wild-type and Fc-mutated IgG scaffolds. However, in vivo antitumor activity of the wild-type anti-PD-L1 mAb avelumab was enhanced by combination treatment with an FcγRIIB-blocking antibody, which was co-administered to overcome the suppressor function of FcγRIIB in the tumor microenvironment (TME). We performed Fc glycoengineering to remove the fucose subunit from the Fc-attached glycan of avelumab to enhance its binding to the activating FcγRIIIA. Treatment with the Fc-afucosylated version of avelumab also enhanced antitumor activity and induced stronger antitumor immune responses compared with the parental IgG. The enhanced effect by afucosylated PD-L1 antibody was dependent on neutrophils and associated with decreased frequencies of PD-L1⁺ myeloid cells and increased infiltration of T cells in the TME. Our data reveal that the current design of FDA-approved anti-PD-L1 mAbs does not optimally harness FcγR pathways and suggest two strategies to enhance FcγR engagement to optimize anti-PD-L1 immunotherapy.

Cyclophosphamide depletes tumor infiltrating T regulatory cells and combined with anti-PD-1 therapy improves survival in murine neuroblastoma

The outcome for children with high-risk neuroblastoma is poor despite intensive multi-modal treatment protocols. Toxicity from current treatments is significant, and novel approaches are needed to improve outcome. Cyclophosphamide (CPM) is a key component of current chemotherapy regimens and is known to have immunomodulatory effects. However, this has not been investigated in the context of tumor infiltrating lymphocytes in neuroblastoma. Using murine models of neuroblastoma, the immunomodulatory effects of low-dose CPM were investigated using detailed immunophenotyping. We demonstrated that CPM resulted in a specific depletion of intratumoral T regulatory cells by apoptosis, and when combined with anti-PD-1 antibody therapy, this resulted in improved therapeutic efficacy. CPM combined with anti-PD-1 therapy was demonstrated to be an effective combinational therapy, with metronomic CPM found to be more effective than single dosing in more resistant tumor models. Overall, this pre-clinical data strongly support clinical evaluation of such combination strategies in neuroblastoma.

Penpulimab, an Fc-Engineered IgG1 Anti-PD-1 Antibody, With Improved Efficacy and Low Incidence of Immune-Related Adverse Events

Background

IgG4 anbibodies are deficient in stability and may contribute to tumor-associated escape from immune surveillance. We developed an IgG1 backbone anti-programmed cell death protein-1 (PD-1) antibody, penpulimab, which is designed to remove crystallizable fragment (Fc) gamma receptor (FcγR) binding that mediates antibody-dependent cell-mediated cytotoxicity (ADCC), antibody-dependent cellular phagocytosis (ADCP) and proinflammatory cytokine release.

Methods

Aggregation of different anti-PD-1 antibodies was tested by size exclusion chromatography, and melting temperature midpoint (Tm) and aggregation temperature onset (Tagg) were also determined. The affinity constants of penpulimab for PD-1 and human FcγRs were measured by surface plasmon resonance and biolayer interferometry. ADCC and ADCP were determined in cellular assays and antibody-dependent cytokine release (ADCR) from human macrophages was detected by ELISA. Binding kinetics of penpulimab to human PD-1 was determined by Biacore, and epitope/paratope mapping of PD-1/penpulimab was investigated using x-ray crystallography. Additionally, patients from six ongoing trials were included for analysis of immune-related adverse events (irAEs).

Results

Penpulimab demonstrated better stability and a lower level of host-cell protein residue compared with IgG4 backbone anti-PD-1 antibodies. As expected, penpulimab exhibited no apparent binding to FcγRIa, FcγRIIa_H131, FcγRIIIa_V158 and FcγRIIIa_F158, elicited no apparent ADCC and ADCP activities, and induced no remarkable IL-6 and IL-8 release by activated macrophages in vitro. Penpulimab was shown in the co-crystal study to bind to human PD-1 N-glycosylation site at N58 and had a slower off-rate from PD-1 versus nivolumab or pembrolizumab. Four hundred sixty-five patients were analyzed for irAEs. Fifteen (3.2%) patients had grade 3 or above irAEs. No death from irAEs was reported.

Conclusions

IgG1 backbone anti-PD1 antibody penpulimab has a good stability and reduced host cell protein residue, as well as potent binding to the antigen. Fc engineering has eliminated Fc-mediated effector functions of penpulimab including ADCC, ADCP and reduced ADCR, which may contribute to its more favorable safety profile.

Clinical Trial Registration

www.ClinicalTrials.gov, identifier: AK105-101: NCT03352531, AK105-201: NCT03722147, AK105-301: NCT03866980, AK105-202:NCT03866967, AK105-203: NCT04172571, AK105-204: NCT04172506.

Relevance of Fc Gamma Receptor Polymorphisms in Cancer Therapy With Monoclonal Antibodies

Therapeutic monoclonal antibodies (mAbs), including immune checkpoint inhibitors (ICIs), are an important breakthrough for the treatment of cancer and have dramatically changed clinical outcomes in a wide variety of tumours. However, clinical response varies among patients receiving mAb-based treatment, so it is necessary to search for predictive biomarkers of response to identify the patients who will derive the greatest therapeutic benefit. The interaction of mAbs with Fc gamma receptors (FcγR) expressed by innate immune cells is essential for antibody-dependent cellular cytotoxicity (ADCC) and this binding is often critical for their in vivo efficacy. FcγRIIa (H131R) and FcγRIIIa (V158F) polymorphisms have been reported to correlate with response to therapeutic mAbs. These polymorphisms play a major role in the affinity of mAb receptors and, therefore, can exert a profound impact on antitumor response in these therapies. Furthermore, recent reports have revealed potential mechanisms of ICIs to modulate myeloid subset composition within the tumour microenvironment through FcγR-binding, optimizing their anti-tumour activity. The purpose of this review is to highlight the clinical contribution of FcγR polymorphisms to predict response to mAbs in cancer patients.

Tumor-Associated Macrophages Regulate PD-1/PD-L1 Immunosuppression

Anti-programmed cell death 1 (PD-1) or anti-PD-ligand (L) 1 drugs, as classic immune checkpoint inhibitors, are considered promising treatment strategies for tumors. In clinical practice, some cancer patients experience drug resistance and disease progression in the process of anti-PD-1/PD-L1 immunotherapy. Tumor-associated macrophages (TAMs) play key roles in regulating PD-1/PD-L1 immunosuppression by inhibiting the recruitment and function of T cells through cytokines, superficial immune checkpoint ligands, and exosomes. There are several therapies available to recover the anticancer efficacy of PD-1/PD-L1 inhibitors by targeting TAMs, including the inhibition of TAM differentiation and re-education of TAM activation. In this review, we will summarize the roles and mechanisms of TAMs in PD-1/PD-L1 blocker resistance. Furthermore, we will discuss the therapies that were designed to deplete TAMs, re-educate TAMs, and intervene with chemokines secreted by TAMs and exosomes from M1 macrophages, providing more potential options to improve the efficacy of PD-1/PD-L1 inhibitors.

An affinity threshold for maximum efficacy in anti-PD-1 immunotherapy

Monoclonal antibodies targeting the programmed cell death protein 1 (PD-1) remain the most prevalent cancer immunotherapy both as a monotherapy and in combination with additional therapies. Despite the extensive success of anti-PD-1 monoclonal antibodies in the clinic, the experimental relationship between binding affinity and functional potency for anti-PD-1 antibodies in vivo has not been reported. Anti-PD-1 antibodies with higher and lower affinity than nivolumab or pembrolizumab are entering the clinic and show varied preclinical efficacy. Here, we explore the role of broad-ranging affinity variation within a single lineage in a syngeneic immunocompetent mouse model. By developing a panel of murine anti-PD-1 antibodies with varying affinity (ranging from KD = 20 pM - 15 nM), we find that there is a threshold affinity required for maximum efficacy at a given dose in the treatment of the MC38 adenocarcinoma model with anti-PD-1 immunotherapy. Physiologically based pharmacokinetic modeling complements interpretation of the experimental results and highlights the direct relationship between dose, affinity, and PD-1 target saturation in the tumor.