Characterisation of a Novel Anti-CD52 Antibody with Improved Efficacy and Reduced Immunogenicity

Therapeutic potential of cis-targeting bispecific antibodies

The growing clinical success of bispecific antibodies (bsAbs) has led to rapid interest in leveraging dual targeting in order to generate novel modes of therapeutic action beyond mono-targeting approaches. While bsAbs that bind targets on two different cells (trans-targeting) are showing promise in the clinic, the co-targeting of two proteins on the same cell surface through cis-targeting bsAbs (cis-bsAbs) is an emerging strategy to elicit new functionalities. This includes the ability to induce proximity, enhance binding to a target, increase target/cell selectivity, and/or co-modulate function on the cell surface with the goal of altering, reversing, or eradicating abnormal cellular activity that contributes to disease. In this review, we focus on the impact of cis-bsAbs in the clinic, their emerging applications, and untangle the intricacies of improving bsAb discovery and development.

Evaluation of the paired-Cas9 nickase and RNA-guided FokI genome editing tools in precise integration of an anti-CD52 bicistronic monoclonal antibody expression construct at Chinese hamster ovary cells 18S rDNA locus

INTRODUCTION

The aim of this study was to compare two CRISPR/Cas9-based orthogonal strategies, paired-Cas9 nickase (paired-Cas9n) and RNA-guided FokI (RFN), in targeting 18S rDNA locus in Chinese hamster ovary (CHO) cells and precisely integrating a bicistronic anti-CD52 monoclonal antibody (mAb) expression cassette into this locus.

METHODS

T7E1 and high-resolution melt (HRM) assays were used to compare the ability of mentioned systems in inducing double-strand break (DSB) at the target site. Moreover, 5'- and 3'-junction polymerase chain reactions (PCR) were used to verify the accuracy of the targeted integration of the mAb expression cassette into the 18S rDNA locus. Finally, anti-CD52 mAb gene copy number was measured and, its expression was analyzed using ELISA and western blot assays.

RESULTS

Our results indicated that both paired-Cas9n and RFN induced DSB at the target site albeit RFN performance was slightly more efficient in HRM analysis. We also confirmed that the anti-CD52 mAb cassette was accurately integrated at the 18S rDNA locus and the mAb was expressed successfully in CHO cells.

CONCLUSION

Taken together, our findings elucidated that both paired-Cas9n and RFN genome editing tools are promising in targeting the 18S rDNA locus. Site specific integration of the bicistronic anti-CD52 mAb expression cassette at this locus in the CHO-K1 cells was obtained, using RFN. Moreover, proper expression of the anti-CD52 mAb at the 18S rDNA target site can be achieved using the bicistronic internal ribosome entry site (IRES)-based vector system.

Combining deep mutational scanning to heatmap of HLA class II binding of immunogenic sequences to preserve functionality and mitigate predicted immunogenicity

Removal of CD4 T cell epitopes from therapeutic antibody sequences is expected to mitigate their potential immunogenicity, but its application is complicated by the location of their T cell epitopes, which mainly overlap with complementarity-determining regions. We therefore evaluated the flexibility of antibody sequences to reduce the predicted affinity of corresponding peptides for HLA II molecules and to maintain antibody binding to its target in order to guide antibody engineering for mitigation of predicted immunogenicity. Permissive substitutions to reduce affinity of peptides for HLA II molecules were identified by establishing a heatmap of HLA class II binding using T-cell epitope prediction tools, while permissive substitutions preserving binding to the target were identified by means of deep mutational scanning and yeast surface display. Combinatorial libraries were then designed to identify active clones. Applied to adalimumab, an anti-TNFα human antibody, this approach identified 200 mutants with a lower HLA binding score than adalimumab. Three mutants were produced as full-length antibodies and showed a higher affinity for TNFα and neutralization ability than adalimumab. This study also sheds light on the permissiveness of antibody sequences with regard to functionality and predicted T cell epitope content.

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

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

Antidrug Antibodies Against Biological Treatments for Multiple Sclerosis

The development of antidrug antibodies (ADAs) is a major problem in several recombinant protein therapies used in the treatment of multiple sclerosis (MS). The etiology of ADAs is multifaceted. The predisposition for a breakdown of immune tolerance is probably genetically determined, and many factors may contribute to the immunogenicity, including structural properties, formation of aggregates, and presence of contaminants and impurities from the industrial manufacturing process. ADAs may have a neutralizing capacity and can reduce or abrogate the bioactivity and therapeutic efficacy of the drug and cause safety issues. Interferon (IFN)-β was the first drug approved for the treatment of MS, and-although it is generally recognized that neutralizing antibodies (NAbs) appear and potentially have a negative effect on therapeutic efficacy-the use of routine measurements of NAbs and the interpretation of the presence of NAbs has been debated at length. NAbs appear after 9-18 months of therapy in up to 40% of patients treated with IFNβ, and the frequency and titers of NAbs depend on the IFNβ preparation. Although all pivotal clinical trials of approved IFNβ products in MS exhibited a detrimental effect of NAbs after prolonged therapy, some subsequent studies did not observe clinical effects from NAbs, which led to the claim that NAbs did not matter. However, it is now largely agreed that persistently high titers of NAbs indicate an abrogation of the biological response and, hence, an absence of therapeutic efficacy, and this observation should lead to a change of therapy. Low and medium titers are ambiguous, and treatment decisions should be guided by determination of in vivo messenger RNA myxovirus resistance protein A induction after IFNβ administration and clinical disease activity. During treatment with glatiramer acetate, ADAs occur frequently but do not appear to adversely affect treatment efficacy or result in adverse events. ADAs occur in approximately 5% of patients treated with natalizumab within 6 months of therapy, and persistent NAbs are associated with a lack of efficacy and acute infusion-related reactions and should instigate a change of therapy. When using the anti-CD20 monoclonal antibodies ocrelizumab and ofatumumab in the treatment of MS, it is not necessary to test for NAbs as these occur very infrequently. Alemtuzumab is immunogenic, but routine measurements of ADAs are not recommended as the antibodies in the pivotal 2-year trials at the population level did not influence lymphocyte depletion or repopulation, efficacy, or safety. However, in some individuals, NAbs led to poor lymphocyte depletion.

A radiologist’s guide to novel anticancer therapies in the era of precision medicine

Novel anticancer agents have replaced conventional chemotherapy as first line agents for many cancers, with continued new and expanding indications. Small molecule inhibitors act on cell surface or intracellular targets and prevent the downstream signaling that would otherwise permit tumor growth and spread. Anticancer antibodies can be directed against growth factors or may be immunotherapeutic agents. The latter act by inhibiting mechanisms that cancer cells use to evade the immune system. Hormonal agents act by decreasing levels of hormones that are necessary for the growth of certain cancer cells. Cancer therapy protocols often include novel anticancer agents and conventional chemotherapy used successively or in combination, in order to maximize survival and minimize morbidity. A working knowledge of anti-cancer drug classification will aid the radiologist in assessing response on imaging.

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Novel anticancer agents include small molecule inhibitors, antibodies and hormones.

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These agents are predominantly cytostatic and inhibit factors that provide a survival advantage to tumor cells.

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Modern cancer therapy employs a combination of novel anticancer agents and conventional chemotherapy.

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It is essential for radiologists to have a broad understanding of these agents and their mechanisms of action.

CD52-targeted depletion by Alemtuzumab ameliorates allergic airway hyperreactivity and lung inflammation

Allergic asthma is a chronic inflammatory disorder associated with airway hyperreactivity (AHR) whose global prevalence is increasing at an alarming rate. Group 2 innate lymphoid cells (ILC2s) and T helper 2 (T_H2) cells are producers of type 2 cytokines, which may contribute to development of AHR. In this study, we explore the potential of CD52-targeted depletion of type 2 immune cells for treating allergic AHR. Here we show that anti-CD52 therapy can prevent and remarkably reverse established IL-33-induced AHR by reducing airway resistance and alleviating lung inflammation. We further show that CD52 depletion prevents and treats allergic AHR induced by clinically relevant allergens such as Alternaria alternata and house dust mite. Importantly, we leverage various humanized mice models of AHR to show new therapeutic applications for Alemtuzumab, an anti-CD52 depleting antibody that is currently FDA approved for treatment of multiple sclerosis. Our results demonstrate that CD52 depletion is a viable therapeutic option for reduction of pulmonary inflammation, abrogation of eosinophilia, improvement of lung function, and thus treatment of allergic AHR. Taken together, our data suggest that anti-CD52 depleting monoclonal antibodies, such as Alemtuzumab, can serve as viable therapeutic drugs for amelioration of T_H2- and ILC2-dependent AHR.

A deimmunized and pharmacologically optimized Toll-like receptor 5 agonist for therapeutic applications

The Toll-like receptor 5 (TLR5) agonist entolimod, a derivative of Salmonella flagellin, has therapeutic potential for several indications including radioprotection and cancer immunotherapy. However, in Phase 1 human studies, entolimod induced a rapid neutralizing immune response, presumably due to immune memory from prior exposure to flagellated enterobacteria. To enable multi-dose applications, we used structure-guided reengineering to develop a next-generation, substantially deimmunized entolimod variant, GP532. GP532 induces TLR5-dependent NF-κB activation like entolimod but is smaller and has mutations eliminating an inflammasome-activating domain and key B- and T-cell epitopes. GP532 is resistant to human entolimod-neutralizing antibodies and shows reduced de novo immunogenicity. GP532 also has improved bioavailability, a stronger effect on key cytokine biomarkers, and a longer-lasting effect on NF-κB. Like entolimod, GP532 demonstrated potent prophylactic and therapeutic efficacy in mouse models of radiation-induced death and tissue damage. These results establish GP532 as an optimized TLR5 agonist suitable for multi-dose therapies and for patients with high titers of preexisting flagellin-neutralizing antibodies.

Managing the Impact of Immunogenicity in an Era of Immunotherapy: From Bench to Bedside

Biotherapeutics have revolutionized our ability to treat life-threatening diseases. Despite clinical success, the use of biotherapeutics has sometimes been limited by the immune response mounted against them in the form of anti-drug antibodies (ADAs). The multifactorial nature of immunogenicity has prevented a standardized approach for assessing this and each of the assessment methods developed so far does not exhibit high enough reliability to be used alone, due to limited predictiveness. This prompted the Roche Pharma Research and Early Development (pRED) Immunogenicity Working Group to establish an internal preclinical immunogenicity toolbox of in vitro/in vivo approaches and accompanying guidelines for a harmonized assessment and management of immunogenicity in early development. In this article, the complex factors influencing immunogenicity and their associated clinical ramifications are discussed to highlight the importance of an end-to-end approach conducted from lead optimization to clinical candidate selection. We then examine the impact of the resulting lead candidate categorization on the design and implementation of a multi-tiered ADA/immunogenicity assay strategy prior to phase I (entry into human) through early clinical development. Ultimately, the Immunogenicity Toolbox ensures that Roche pRED teams are equipped to address immunogenicity in a standardized manner, paving the way for lifesaving products with improved safety and efficacy.

A primer set for the rapid isolation of scFv fragments against cell surface antigens from immunised rats

Antibody phage display is a powerful platform for discovery of clinically applicable high affinity monoclonal antibodies against a broad range of targets. Libraries generated from immunized animals offer the advantage of in vivo affinity-maturation of V regions prior to library generation. Despite advantages, few studies have described isolation of antibodies from rats using immune phage display. In our study, we describe a novel primer set, covering the full rat heavy chain variable and kappa light chain variable regions repertoire for the generation of an unbiased immune libraries. Since the immune repertoire of rats is poorly understood, we first performed a deep sequencing analysis of the V(D)J regions of VH and VLK genes, demonstrating the high abundance of IGVH2 and IGVH5 families for VH and IGVLK12 and IGVLK22 for VLK. The comparison of gene's family usage in naïve rats have been used to validate the frequency's distribution of the primer set, confirming the absence of PCR-based biases. The primers were used to generate and assemble a phage display library from human CD160-vaccinated rats. CD160 represents a valid therapeutic target as it has been shown to be expressed on chronic lymphocytic leukaemia cells and on the surface of newly formed vessels. We utilised a novel phage display panning strategy to isolate a high affinity pool (KD range: 0.399-233 nM) of CD160 targeting monoclonal antibodies. Subsequently, identified binders were tested for function as third generation Chimeric Antigen Receptors (CAR) T cells demonstrating specific cytolytic activity. Our novel primer set coupled with a streamlined strategy for phage display panning enable the rapid isolation and identification of high affinity antibodies from immunised rats. The therapeutic utility of these antibodies was demonstrated in CAR format.

Specificity of the T Cell Response to Protein Biopharmaceuticals

The anti-drug antibody (ADA) response is an undesired humoral response raised against protein biopharmaceuticals (BPs) which can dramatically disturb their therapeutic properties. One particularity of the ADA response resides in the nature of the immunogens, which are usually human(ized) proteins and are therefore expected to be tolerated. CD4 T cells initiate, maintain and regulate the ADA response and are therefore key players of this immune response. Over the last decade, advances have been made in characterizing the T cell responses developed by patients treated with BPs. Epitope specificity and phenotypes of BP-specific T cells have been reported and highlight the effector and regulatory roles of T cells in the ADA response. BP-specific T cell responses are assessed in healthy subjects to anticipate the immunogenicity of BP prior to their testing in clinical trials. Immunogenicity prediction, also called preclinical immunogenicity assessment, aims at identifying immunogenic BPs and immunogenic BP sequences before any BP injection in humans. All of the approaches that have been developed to date rely on the detection of BP-specific T cells in donors who have never been exposed to BPs. The number of BP-specific T cells circulating in the blood of these donors is therefore limited. T cell assays using cells collected from healthy donors might reveal the weak tolerance induced by BPs, whose endogenous form is expressed at a low level. These BPs have a complete human sequence, but the level of their endogenous form appears insufficient to promote the negative selection of autoreactive T cell clones. Multiple T cell epitopes have also been identified in therapeutic antibodies and some other BPs. The pattern of identified T cell epitopes differs across the antibodies, notwithstanding their humanized, human or chimeric nature. However, in all antibodies, the non-germline amino acid sequences mainly found in the CDRs appear to be the main driver of immunogenicity, provided they can be presented by HLA class II molecules. Considering the fact that the BP field is expanding to include new formats and gene and cell therapies, we face new challenges in understanding and mastering the immunogenicity of new biological products.

Genome-wide analysis highlights contribution of immune system pathways to the genetic architecture of asthma

Asthma is a chronic and genetically complex respiratory disease that affects over 300 million people worldwide. Here, we report a genome-wide analysis for asthma using data from the UK Biobank and the Trans-National Asthma Genetic Consortium. We identify 66 previously unknown asthma loci and demonstrate that the susceptibility alleles in these regions are, either individually or as a function of cumulative genetic burden, associated with risk to a greater extent in men than women. Bioinformatics analyses prioritize candidate causal genes at 52 loci, including CD52, and demonstrate that asthma-associated variants are enriched in regions of open chromatin in immune cells. Lastly, we show that a murine anti-CD52 antibody mimics the immune cell-depleting effects of a clinically used human anti-CD52 antibody and reduces allergen-induced airway hyperreactivity in mice. These results further elucidate the genetic architecture of asthma and provide important insight into the immunological and sex-specific relevance of asthma-associated risk variants.

Asthma is a common disease of the airways for which numerous genetic loci have been identified. Here, Han et al. carry out a genome-wide analysis for asthma to identify additional loci, report sex-stratified and genetic risk score analyses, and functionally follow-up one locus using a murine model of airway hyperreactivity.

A cell-based assay for the detection of neutralizing antibodies against alemtuzumab

Aim:

The humanized anti-CD52 monoclonal antibody alemtuzumab depletes lymphocytes and is currently used to treat relapsing multiple sclerosis. During treatment, anti-alemtuzumab antibodies may develop and reduce effective lymphocyte depletion in future treatment cycles.

Results:

Alemtuzumab–Alexa Fluor 488 conjugate binding to the CHO-CD52 cell surface was inhibited by anti-alemtuzumab antibodies.

Conclusion:

In this proof-of-concept study, a CHO-CD52 cell line has been developed and used to detect the presence of anti-alemtuzumab neutralizing antibodies. This platform provides the basis of an assay for routine screening of serum for neutralizing antibodies from patients treated with alemtuzumab.

We developed a competition assay between alemtuzumab and neutralizing antibodies to adherent CD52-expressing cells. The anti-alemtuzumab antibodies inhibit alemtuzumab–Alexa Fluor 488 binding to cell surface CD52. Reduction in the fluorescence signal is proportional the amount of antidrug antibody in the serum sample.

Therapeutic monoclonal antibodies are currently used for the treatment of numerous diseases and conditions, including relapsing multiple sclerosis, and are the most advanced targeted therapies available. However, they all have the potential to cause immunogenic reactions and generate antibodies that bind to the drug and reduce its therapeutic efficacy. As a result, patients do not receive the expected benefit from treatment, and the effect is cumulative with repeat dosing. The timely detection of antidrug antibodies has the potential to avoid these major risks. Here we describe a cell-based method for detecting anti-alemtuzumab neutralizing antibodies.

The Irony of Humanization: Alemtuzumab, the First, But One of the Most Immunogenic, Humanized Monoclonal Antibodies

Alemtuzumab was designed to reduce the immunogenicity of the parent CD52-specific rat immunoglobulin. Although originally marketed for use in cancer (Mabcampath®), alemtuzumab is currently licensed and formulated for the treatment of relapsing multiple sclerosis (Lemtrada®). Perhaps due to its history as the first humanized antibody, the potential of immunogenicity of the molecule has been considered inconsequential, and anti-drug antibodies (ADA) responses were similarly reported as being clinically insignificant. Nonetheless, despite humanization and depletion of peripheral T and B cells, alemtuzumab probably generates the highest frequency of binding and neutralizing ADA of all humanized antibodies currently in clinical use, and they occur rapidly in a large majority of people with MS (pwMS) on alemtuzumab treatment. These ADA appear to be an inherent issue of the biology of the molecule-and more importantly, the target-such that avoidance of immunogenicity-related effects has been facilitated by the dosing schedule used in clinical practice. At the population level this enables the drug to work in most pwMS, but in some individuals, as we show here, antibody neutralization appears to be sufficiently severe to reduce efficacy and allow disease breakthrough. It is therefore imperative that efficacy of lymphocyte depletion and the anti-drug response is monitored in people requiring additional cycles of treatment, notably following disease breakthrough. This may help inform whether to re-treat or to switch to another disease-modifying treatment.

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.

Early identification of unusually clustered mutations and root causes in therapeutic antibody development

This study reports findings of an unusual cluster of mutations spanning 22 bp (base pairs) in a monoclonal antibody expression vector. It was identified by two orthogonal methods: mass spectrometry on expressed protein and next-generation sequencing (NGS) on the plasmid DNA. While the initial NGS analysis confirmed the designed sequence modification, intact mass analysis detected an additional mass of the antibody molecule expressed in CHO cells. The extra mass was eventually found to be associated with unmatched nucleotides in a distal region by checking full-length sequence alignment plots. Interestingly, the complementary sequence of the mutated sequence was a reverse sequence of the original sequence and flanked by two 10-bp reverse-complementary sequences, leading to an undesirable DNA recombination. The finding highlights the necessity of rigorous examination of expression vector design and early monitoring of molecule integrity at both DNA and protein levels to prevent clones from having sequence variants during cell line development.

Interpreting Lymphocyte Reconstitution Data From the Pivotal Phase 3 Trials of Alemtuzumab

Importance

Alemtuzumab, a CD52-depleting monoclonal antibody, effectively inhibits relapsing multiple sclerosis (MS) but is associated with a high incidence of secondary B-cell autoimmunities that limit use. These effects may be avoided through control of B-cell hyperproliferation.

Objective

To investigate whether the data describing the effect of alemtuzumab on lymphocyte subsets collected during the phase 3 trial program reveal mechanisms explaining efficacy and the risk for secondary autoimmunity with treatment of MS.

Design, Setting, and Participants

Lymphocyte reconstitution data from regulatory submissions of the pivotal Comparison of Alemtuzumab and Rebif Efficacy in Multiple Sclerosis I and II (CARE-MS I and II) trials were obtained from the European Medicines Agency via Freedom of Information requests. Data used in this study were reported from June 22 to October 12, 2016.

Main Outcomes and Measures

Tabulated data from T- and B-lymphocyte subset analysis and antidrug antibody responses were extracted from the supplied documents.

Results

Alemtuzumab depleted CD4+ T cells by more than 95%, including regulatory cells (-80%) and CD8+ T cells (>80% depletion), which remained well below reference levels throughout the trials. However, although CD19+ B cells were initially also depleted (>85%), marked (180% increase) hyperrepopulation of immature B cells occurred with conversion to mature B cells over time. These lymphocyte kinetics were associated with rapid development of alemtuzumab-binding and -neutralizing antibodies and subsequent occurrence of secondary B-cell autoimmunity. Hyperrepopulation of B cells masked a marked, long-term depletion of CD19+ memory B cells that may underpin efficacy in MS.

Conclusions and Relevance

Although blockade of memory T and B cells may limit MS, rapid CD19+ B-cell subset repopulation in the absence of effective T-cell regulation has implications for the safety and efficacy of alemtuzumab. Controlling B-cell proliferation until T-cell regulation recovers may limit secondary autoimmunity, which does not occur with other B-cell-depleting agents.

Changes to International Nonproprietary Names for antibody therapeutics 2017 and beyond: of mice, men and more

Active pharmaceutical substances require an International Nonproprietary Name (INN) assigned by the World Health Organization (WHO) to obtain market authorization as a medicinal product. INNs are selected to represent a unique, generic name for a drug enabling unambiguous identification by stakeholders worldwide. INNs may be requested after initiating clinical development of an investigational drug. Pharmaceutical classes are indicated by a common stem or suffix. Currently, INNs for monoclonal antibody-based drugs are recognized by the suffix, -mab, preceded by a source infix such as -xi- (chimeric), -zu- (humanized) or -u- (human) designating the species from which the antibody was derived. However, many technological advances have made it increasingly difficult to accurately capture an antibody's source in its name. In 2014, the WHO and the United States Adopted Names (USAN) Council approached this challenge by implementing changes to antibody source infix definitions. Unfortunately, gaps and ambiguities in the definitions and procedures resulted in inconsistent source category assignments and widespread confusion. The Antibody Society, extensively supported by academic and industry scientists, voiced concerns leading to constructive dialog during scheduled consultations with WHO and USAN Council representatives. In June 2017, the WHO announced that use of the source infix will be discontinued for new antibody INNs effective immediately. We fully support this change as it better aligns antibody INNs with current and foreseeable future innovations in antibody therapeutics. Here we review the changes implemented. Additionally, we analyzed antibody INNs recently assigned under the previous 2014 definitions and provide recommendations for further alignment.

CD52, CD22, CD26, EG5 and IGF-1R expression in thymic malignancies

BACKGROUND

Thymic epithelial tumours are rare cancers for which new treatment options are required. Identification of putative predictive markers is important for developing clinical trials. We studied the expression of five putative predictive biomarkers, potentially actionable by approved experimental drugs.

METHODS

CD52, CD22, CD26, EG5, and IGF-1R expression were investigated by immunohistochemistry in formalin-fixed surgical samples of thymic epithelial tumour patients. All samples containing 10% positive epithelial tumour cells, independent of tumour cell intensity, were considered as positive. Correlation with histological subtype was performed.

RESULTS

106 surgical samples (89 thymomas, 12 thymic carcinoma, and 5 thymic neuroendocrine tumours) were evaluated. Overall, CD52, CD22, CD26, EG5 and IGF-1R expression was observed in 7%, 42%, 25%, 42% and 77% of samples, respectively. CD52 expression was more frequent in B2 and B3 thymoma. All TET subtypes stained for CD22, mainly AB thymoma (68%). CD26 expression also correlated with AB thymoma (68%), and A thymoma (50%) subtype, while IGFR1 was the most common marker expressed by thymic carcinoma samples (92%), followed by EG5 (60%). Only EG5 expression was significantly higher in thymic carcinomas than in thymomas (75% vs. 38%, p=0.026).

CONCLUSIONS

Our data were consistent with a previous study of IGF-1R expression. Based on their expression, activity of agents targeting CD52, CD 22, CD26 and EG5 could be further explored in TET patients.

The INNs and outs of antibody nonproprietary names

An important step in drug development is the assignment of an International Nonproprietary Name (INN) by the World Health Organization (WHO) that provides healthcare professionals with a unique and universally available designated name to identify each pharmaceutical substance. Monoclonal antibody INNs comprise a –mab suffix preceded by a substem indicating the antibody type, e.g., chimeric (-xi-), humanized (-zu-), or human (-u-). The WHO publishes INN definitions that specify how new monoclonal antibody therapeutics are categorized and adapts the definitions to new technologies. However, rapid progress in antibody technologies has blurred the boundaries between existing antibody categories and created a burgeoning array of new antibody formats. Thus, revising the INN system for antibodies is akin to aiming for a rapidly moving target. The WHO recently revised INN definitions for antibodies now to be based on amino acid sequence identity. These new definitions, however, are critically flawed as they are ambiguous and go against decades of scientific literature. A key concern is the imposition of an arbitrary threshold for identity against human germline antibody variable region sequences. This leads to inconsistent classification of somatically mutated human antibodies, humanized antibodies as well as antibodies derived from semi-synthetic/synthetic libraries and transgenic animals. Such sequence-based classification implies clear functional distinction between categories (e.g., immunogenicity). However, there is no scientific evidence to support this. Dialog between the WHO INN Expert Group and key stakeholders is needed to develop a new INN system for antibodies and to avoid confusion and miscommunication between researchers and clinicians prescribing antibodies.

A deimmunised form of the ribotoxin, α-sarcin, lacking CD4+ T cell epitopes and its use as an immunotoxin warhead

Fungal ribotoxins that block protein synthesis can be useful warheads in the context of a targeted immunotoxin. α-Sarcin is a small (17 kDa) fungal ribonuclease produced by Aspergillus giganteus that functions by catalytically cleaving a single phosphodiester bond in the sarcin–ricin loop of the large ribosomal subunit, thus making the ribosome unrecognisable to elongation factors and leading to inhibition of protein synthesis. Peptide mapping using an ex vivo human T cell assay determined that α-sarcin contained two T cell epitopes; one in the N-terminal 20 amino acids and the other in the C-terminal 20 amino acids. Various mutations were tested individually within each epitope and then in combination to isolate deimmunised α-sarcin variants that had the desired properties of silencing T cell epitopes and retention of the ability to inhibit protein synthesis (equivalent to wild-type, WT α-sarcin). A deimmunised variant (D9T/Q142T) demonstrated a complete lack of T cell activation in in vitro whole protein human T cell assays using peripheral blood mononuclear cells from donors with diverse HLA allotypes. Generation of an immunotoxin by fusion of the D9T/Q142T variant to a single-chain Fv targeting Her2 demonstrated potent cell killing equivalent to a fusion protein comprising the WT α-sarcin. These results represent the first fungal ribotoxin to be deimmunised with the potential to construct a new generation of deimmunised immunotoxin therapeutics.

Design and engineering of deimmunized biotherapeutics

Therapeutic proteins are powerful next-generation drugs able to effectively treat diverse and devastating diseases, but the development and use of biotherapeutics entails unique challenges and risks. In particular, protein drugs are subject to immune surveillance in the human body, and ensuing antidrug immune responses can cause a wide range of problems including altered pharmacokinetics, loss of efficacy, and even life-threating complications. Here we review recent progress in technologies for engineering deimmunized biotherapeutics, placing particular emphasis on deletion of immunogenic antibody and T cell epitopes via experimentally or computationally guided mutagenesis.