Rituximab (monoclonal anti-CD20 antibody): mechanisms of action and resistance

A versatile toolkit for overcoming AAV immunity

Recombinant adeno-associated virus (AAV) is a promising delivery vehicle for in vivo gene therapy and has been widely used in >200 clinical trials globally. There are already several approved gene therapy products, e.g., Luxturna and Zolgensma, highlighting the remarkable potential of AAV delivery. In the past, AAV has been seen as a relatively non-immunogenic vector associated with low risk of toxicity. However, an increasing number of recent studies indicate that immune responses against AAV and transgene products could be the bottleneck of AAV gene therapy. In clinical studies, pre-existing antibodies against AAV capsids exclude many patients from receiving the treatment as there is high prevalence of antibodies among humans. Moreover, immune response could lead to loss of efficacy over time and severe toxicity, manifested as liver enzyme elevations, kidney injury, and thrombocytopenia, resulting in deaths of non-human primates and patients. Therefore, extensive efforts have been attempted to address these issues, including capsid engineering, plasmapheresis, IgG proteases, CpG depletion, empty capsid decoy, exosome encapsulation, capsid variant switch, induction of regulatory T cells, and immunosuppressants. This review will discuss these methods in detail and highlight important milestones along the way.

Rituximab therapy in ROHHAD(NET) syndrome

OBJECTIVES

Rapid-onset obesity with hypoventilation, hypothalamic dysfunction, autonomic dysregulation, and neural-crest tumour (ROHHAD(NET)) is a rare syndrome presenting in early childhood associated with high morbidity and mortality. There is no specific diagnostic biomarker and diagnosis is based on clinical features. An autoimmune origin has been postulated.

CASE PRESENTATION

Management is largely supportive. We report a case of a five-year old female who presented in respiratory arrest after 6-months of rapid weight gain. She had central hypoventilation, central diabetes insipidus, growth hormone deficiency and hyperprolactinaemia. She displayed elevated interleukin-6 levels on cytokine serology which normalised after rituximab treatment. After rituximab treatment, her weight reduced significantly from greatly above the 99.6th to the 50th centile in 12 months.

CONCLUSIONS

This response possibly reflects an underlying, immune-inflammatory pathology driving excess adiposity in this condition. Potentially, other aspects of ROHHAD(NET) may be mediated through autoimmune dysregulation in which case rituximab may provide benefits for prognosis and survival.

Study of the Stability of Sandoz Rituximab Biosimilar Rixathon®/Riximyo® When Subjected for up to 21 Days to Ambient Storage

Aim

The purpose of this study was to evaluate the extended physicochemical and biological stability of Sandoz Rixathon®/Riximyo® (SDZ-RTX) after exposure to out-of-fridge (OOF) conditions.

Materials and Methods

The impact of the short-term temperature excursion on stability parameters of SDZ-RTX was simulated by subsequently exposing the three batches of SDZ-RTX (100 and 500 mg) to OOF conditions, (I) 25 ± 2 °C/60 ± 5% relative humidity (RH) and (II) 30 ± 2 °C/65 ± 5% RH, for up to 21 days after more than the claimed 36-month shelf-life storage in long-term conditions (5 ± 3 °C). Analytical methods used included the cation exchange chromatography (CEX), size exclusion chromatography (SEC), and non-reducing capillary electrophoresis-sodium dodecyl sulfate (nrCE-SDS), as well as biological activity by complement-dependent cytotoxicity (CDC)-bioactivity as well as further methods, for example, related to identity and pharmacopoeia test methods.

Results

No notable changes were observed across all batches with respect to identity (charge and primary structure), pharmaceutical tests (clarity, visible and subvisible particles analytics, container appearance, degree of coloration, pH, osmolality, extractable volume, and container closure integrity testing), protein content by UV and microbiological parameters (sterility and bacterial endotoxins) under both OOF conditions. Only minor changes were observed for parameters evaluated via SEC, CEX, and nrCE-SDS. For potency (CDC-bioactivity) only one of the batches showed a relevant change. Even for these stability-indicating test methods, all analyzed parameters complied with the shelf-life specifications.

Conclusion

SDZ-RTX is safe for use even under worst-case conditions, for example, after subjecting it for up to 21 days at OOF conditions (25 ± 2 °C/60 ± 5% RH or 30 ± 2 °C/65 ± 5% RH) after the batches had reached an age that was already beyond the claimed shelf-life.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40268-022-00393-4.

Protective effects of rituximab on puromycin-induced apoptosis, loss of adhesion and cytoskeletal alterations in human podocytes

Podocytes are highly specialized cells playing a key role in the filtration function of the kidney. A damaged podocyte ultrastructure is associated with a reorganization of the actin cytoskeleton and accompanied with a loss of adhesion to the glomerular basement membrane leading to proteinuria in many forms of glomerular diseases, e.g. nephrotic syndrome. If the first-line therapy with glucocorticoids fails, alternative immunosuppressive agents are used, which are known to have the potential to stabilize the actin cytoskeleton. A new option for preventing relapses in steroid dependent nephrotic syndrome is the monoclonal antibody rituximab, which, in addition to its B-cell depleting effect, is assumed to have direct effects on podocytes. We here provide data on the non-immunological off-target effects of the immunosuppressant rituximab on podocyte structure and dynamics in an in vitro puromycin aminonucleoside model of podocyte injury. A conditionally immortalized human podocyte cell line was used. Differentiated podocytes were treated with puromycin aminonucleoside and rituximab. Our studies focussed on analyzing the structure of the actin cytoskeleton, cellular adhesion and apoptosis using immunofluorescence staining and protein biochemistry methods. Treatment with rituximab resulted in a stabilization of podocyte actin stress fibers in the puromycin aminonucleoside model, leading to an improvement in cell adhesion. A lower apoptosis rate was observed after parallel treatment with puromycin aminonucleoside and rituximab visualized by reduced nuclear fragmentation. Consistent with this data, Western-blot analyses demonstrated that rituximab directly affects the caspase pathways by inhibiting the activation of Caspases-8, -9 and -3, suggesting that rituximab may inhibit apoptosis. In conclusion, our results indicate an important role of the immunosuppressant rituximab in terms of stability and morphogenesis of podocytes, involving apoptosis pathways. This could help to improve therapeutical concepts for patients with proteinuria mediated by diseased podocytes.

Age-associated B cells in autoimmune diseases

Age-associated B cells (ABCs) are a transcriptionally and functionally unique B cell population. In addition to arising with age and following infection, ABCs are expanded during autoimmune disease, including those with systemic lupus erythematosus, multiple sclerosis, and rheumatoid arthritis. The exact nature of how ABCs impact disease remains unclear. Here, we review what is known regarding ABC development and distribution during diseases including systemic lupus erythematosus, multiple sclerosis, and rheumatoid arthritis. We discuss possible mechanisms by which ABCs could contribute to disease, including the production of cytokines and autoantibodies or stimulation of T cells. Finally, we speculate on how ABCs might act as mediators between sex, infection, and autoimmune disease, and discuss avenues for further research.

Effect of Rituximab Compared with Natalizumab and Fingolimod in Patients with Relapsing-Remitting Multiple Sclerosis: A Cohort Study

The objective of this study was to evaluate the clinical files of patients with RRMS who started rituximab (RTX) compared with a second-line treatment (natalizumab (NTZ) or fingolimod (FTY)). This was a historical cohort study. We compared the effect according to the Expanded Disability Status Scale (EDSS) and the number of relapses in RRMS patients receiving these treatments after a mean period of 12 months. We found a statistically significant difference (p < 0.001) when comparing the EDSS scores and the annual relapse rates of patients receiving RTX with those receiving NTZ or FTY. This study is essential for our clinical practice, since patients with limited treatment options represent a challenge with regard to the management of their medical care. However, clinical trials and prospective studies with long follow-up periods are necessary to provide sufficient evidence on the efficacy of RTX and thus include this treatment in the therapeutic profile of patients with MS.

CD20-specific chimeric antigen receptor-expressing T cells as salvage therapy in rituximab-refractory/relapsed B-cell non-Hodgkin lymphoma

BACKGROUND AIMS

The infusion of chimeric antigen receptor (CAR) T cells that target specific tumor-associated antigens is a promising strategy that has exhibited encouraging results in clinical trials. However, few studies have focused on the effectiveness and safety of CD20 CAR T cells in rituximab-refractory/relapsed (R/R) B-cell non-Hodgkin lymphoma (B-NHL) patients, particularly those treated with rituximab for a short time. This prospective study aimed to assess the effectiveness and toxicity of CD20 CAR T cells in R/R B-NHL patients previously treated with rituximab.

METHODS

The authors conducted a prospective, single-center phase I study on the effectiveness and toxicity of CD20 CAR T cells in rituximab-treated R/R B-NHL patients (no. ChiCTR2000036350). A total of 15 patients with R/R B-NHL were enrolled between November 21, 2017, and December 1, 2021.

RESULTS

An overall response rate of 100% was shown in enrolled patients, with 12 (80%) achieving complete remission and three (20%) achieving partial remission for the best response. The median follow-up time was 12.4 months. Progression-free survival and overall survival were not yet reached by the data cutoff day. No patient developed grade 4 cytokine release syndrome, and only one patient had immune effector cell-associated neurotoxicity syndrome.

CONCLUSIONS

All enrolled B-NHL patients who were previously R/R to rituximab achieved different degrees of clinical response with tolerable toxicities. Notably, patients who had received rituximab within 3 months had a poorer prognosis.

Biosimilar monoclonal antibodies in China: A patent review

Biosimilars play an important role in reducing the burden on patients and increasing the market competition. Biosimilar monoclonal antibodies are currently one of the hotspots of research and development in China with policies support. With the continuous improvement of policies, the enthusiasm for the research and development of biosimilars has increased year by year. The policy requirements in different periods have different degrees of impact on the patent applications of pharmaceutical companies. This review introduces the biosimilar monoclonal antibodies market status and approval process in China, analyzes the patents in this field, and helps pharmaceutical companies protect their intellectual property rights.

Template-Assisted Crystallization Behavior in Stirred Solutions of the Monoclonal Antibody Anti-CD20: Probability Distributions of Induction Times

We present a method to determine the template crystallization behavior of proteins. This method is a statistical approach that accounts for the stochastic nature of nucleation. It makes use of batch-wise experiments under stirring conditions in volumes smaller than 0.3 mL to save material while mimicking larger-scale processes. To validate our method, it was applied to the crystallization of a monoclonal antibody of pharmaceutical interest, Anti-CD20. First, we determined the Anti-CD20 phase diagram in a PEG-400/Na₂SO₄/water system using the batch method, as, to date, no such data on Anti-CD20 solubility have been reported. Then, the probability distribution of induction times was determined experimentally, in the presence of various mesoporous silica template particles, and crystallization of Anti-CD20 in the absence of templates was compared to template-assisted crystallization. The probability distribution of induction times is shown to be a suitable method to determine the effect of template particles on protein crystallization. The induction time distribution allows for the determination of two key parameters of nucleation, the nucleation rate and the growth time. This study shows that the use of silica particles leads to faster crystallization and a higher nucleation rate. The template particle characteristics are shown to be critical parameters to efficiently promote protein crystallization.

Development of New Drugs for Autoimmune Hemolytic Anemia

Autoimmune hemolytic anemia (AIHA) is a rare disorder characterized by the autoantibody-mediated destruction of red blood cells, and treatments for it still remain challenging. Traditional first-line immunosuppressive therapy, which includes corticosteroids and rituximab, is associated with adverse effects as well as treatment failures, and relapses are common. Subsequent lines of therapy are associated with higher rates of toxicity, and some patients remain refractory to currently available treatments. Novel therapies have become promising for this vulnerable population. In this review, we will discuss the mechanism of action, existing data, and ongoing clinical trials of current novel therapies for AIHA, including B-cell-directed therapy, phagocytosis inhibition, plasma cell-directed therapy, and complement inhibition.

Coding joint: kappa-deleting recombination excision circle ratio and B cell activating factor level: predicting juvenile dermatomyositis rituximab response, a proof-of-concept study

BACKGROUND

This pilot study's primary aim was to determine if oligoclonal B cell expansion in children with Juvenile Dermatomyositis (JDM) predicts response to Rituximab therapy. We evaluated: (1) tissue B cell depletion efficacy by measuring the ratio of Coding joint (CJ) to Kappa-deleting recombination excision circle (KREC) DNA, and (2) serum BAFF level upon B cell recovery.

METHODS

CJ and KREC values were measured via qPCR assessment of serial PBMC stored (- 80 °C) in the CureJM Center's BioRepository. Serum BAFF was quantitated by Mesoscale® technology. Oligoclonal B cell expansion was defined as a CJ:KREC ≥ 8 prior to Rituximab therapy. Detection of a CJ:KREC ratio ≤ 2.5 in the first sample after Rituximab was designated as adequate B cell depletion. A significant clinical response to therapy was defined as improvement in Disease Activity Score (DAS) by at least 2 points on consecutive visits within the first 12 months of therapy.

RESULTS

Six out of nine children with JDM showed oligoclonal B cell expansion prior to Rituximab (CJ:KREC ≥ 8). Of those 6 patients, 4 had evidence of effective B cell depletion after Rituximab (CJ:KREC ≤ 2.5), and all 4 of those subjects displayed a significant clinical response to Rituximab. Serum BAFF level increased in 8/9 children after Rituximab.

CONCLUSIONS

In this proof-of-concept study, JDM patients with oligoclonal B cell expansion prior to Rituximab have more favorable clinical outcomes after Rituximab. We speculate: (1) B cell depletion post-Rituximab predicts JDM clinical response; (2) increased BAFF post-Rituximab may contribute to disease flare.

Bispecific mAb2 Antibodies Targeting CD59 Enhance the Complement-Dependent Cytotoxicity Mediated by Rituximab

Inhibition of complement activation via the overexpression of complement-regulatory proteins (CRPs), most notably CD46, CD55 and CD59, is an efficient mechanism of disguise of cancer cells from a host immune system. This phenomenon extends to counteract the potency of therapeutic antibodies that could lyse target cells by eliciting complement cascade. The manifold functions and ubiquitous expression of CRPs preclude their systemic specific inhibition. We selected CD59-specific Fc fragments with a novel antigen binding site (Fcabs) from yeast display libraries using recombinant antigens expressed in bacterial or mammalian cells. To produce a bispecific antibody, we endowed rituximab, a clinically applied anti-CD20 antibody, used for therapy of various lymphoid malignancies, with an anti-CD59 Fcab. This bispecific antibody was able to induce more potent complement-dependent cytotoxicity for CD20 and CD59 expressing Raji cell line measured with lactate dehydrogenase-release assay, but had no effect on the cells with lower levels of the primary CD20 antigen or CD20-negative cells. Such molecules are promising candidates for future therapeutic development as they elicit a higher specific cytotoxicity at a lower concentration and hence cause a lower exhaustion of complement components.

Safety and Efficacy of Engineered Toxin Body MT-3724 in Relapsed or Refractory B-cell Non-Hodgkin's Lymphomas and Diffuse Large B-cell Lymphoma

MT-3724, a novel engineered toxin body comprised of an anti-CD20 single-chain variable fragment genetically fused to Shiga-like Toxin A subunit, is capable of binding to and internalizing against CD20, inducing cell killing via permanent ribosomal inactivation. This study evaluated MT-3724 in patients with relapsed/refractory B-cell non-Hodgkin lymphoma (r/rNHL). This open-label, multiple-dose phase Ia/b trial included a dose escalation in patients with r/rNHL according to a standard 3+3 design. Primary objectives were to determine the MTD and pharmacokinetics/pharmacodynamics. In a dose expansion study at MTD in serum rituximab-negative patients with diffuse large B-cell lymphoma (DLBCL), primary objectives were safety, tolerability, and pharmacokinetics/pharmacodynamics. Twenty-seven patients enrolled. MTD was 50 μg/kg/dose with 6,000 μg/dose cap. Thirteen patients experienced at least one grade ≥3 treatment-related adverse events; the most common grade ≥3 event was myalgia (11.1%). Two patients (75 μg/kg/dose) experienced grade 2 treatment-related capillary leak syndrome. Overall objective response rate was 21.7%. In serum rituximab-negative patients with DLBCL or composite DLBCL (n = 12), overall response rate was 41.7% (complete response, n = 2; partial response, n = 3). In patients with detectable baseline peripheral B cells, treatment resulted in dose-dependent B-cell depletion. The proportion of patients with anti-drug antibodies (ADA) increased during treatment and the majority appeared to be neutralizing based on an in vitro assay; nevertheless, tumor regression and responses were observed. MT-3724 demonstrated efficacy at the MTD in this population of previously treated patients with r/rDLBCL, with mild-to-moderate immunogenic safety events.

Significance

This work describes the safety and efficacy of a new pharmaceutical pathway that could provide a treatment option for a subset of patients with a critical unmet therapeutic need. The study drug, MT-3724, is capable of targeting B-cell lymphomas via a unique, potent cell-killing mechanism that appears to be promising.

CD47 overexpression is common in intestinal non-GCB type diffuse large B-cell lymphoma and associated with 18q21 gain

The CD47/signal regulatory protein α pathway is an emerging immune checkpoint that is a new therapeutic target. We investigated CD47 expression in diffuse large B-cell lymphoma (DLBCL) of various subtypes and organs. Moreover, the relationship between CD47 expression and genetic alterations was analyzed using panel-based massively parallel sequencing (next-generation sequencing [NGS]). CD8, CD68, and CD47 immunohistochemical staining were performed on 238 patients with DLBCL. CD47 was scored according to intensity on a 5-level scale, and CD8 and CD68 were quantitatively evaluated using QuPath software. Panel-based NGS was performed in 37 patients. In CD8 and CD68 quantitative analyses by organs, intestinal DLBCL showed significantly lower cytotoxic T-cell infiltration than that in others (P < .001). The CD47-high group comprised 24 of 58 (41.4%) patients in the group with DLBCL from intestine and 15 of 180 (8.3%) patients in the group with DLBCL from other organs (P < .001). The 18q21 gain/amplification was found in 10 of 37 patients, and all of them were CD47-high. Intestinal CD47-high DLBCL occurred in terminal ileum to ascending colon and was restricted to nongerminal center B-cell type. In the survival analyses, the prognosis of nonintestinal CD47-high DLBCL was poorer than that of intestinal CD47-high DLBCL (P = .025). CD47-high DLBCL was closely associated with 18q21 gain/amplification and showed a high prevalence in intestine. We propose to classify CD47-high DLBCL into intestinal and nonintestinal types. Further studies are necessary to assess whether the constellation of features seen here is reproducible and sufficient to consider primary intestinal DLBCL as a distinct biological entity.

Viral Evolution and Immunology of SARS-CoV-2 in a Persistent Infection after Treatment with Rituximab

Background. Prolonged shedding of SARS-CoV-2 in immunocompromised patients has been described. Furthermore, an accumulation of mutations of the SARS-CoV-2 genome in these patients has been observed. Methods. We describe the viral evolution, immunologic response and clinical course of a patient with a lymphoma in complete remission who had received therapy with rituximab and remained SARS-CoV-2 RT-qPCR positive for 161 days. Results. The patient remained hospitalised for 10 days, after which he fully recovered and remained asymptomatic. A progressive increase in Ct-value, coinciding with a progressive rise in lymphocyte count, was seen from day 137 onward. Culture of a nasopharyngeal swab on day 67 showed growth of SARS-CoV-2. Whole genome sequencing (WGS) demonstrated that the virus belonged to the wildtype SARS-CoV-2 clade 20B/GR, but rapidly accumulated a high number of mutations as well as deletions in the N-terminal domain of its spike protein. Conclusion. SARS-CoV-2 persistence in immunocompromised individuals has important clinical implications, but halting immunosuppressive therapy might result in a favourable clinical course. The long-term shedding of viable virus necessitates customized infection prevention measures in these individuals. The observed accelerated accumulation of mutations of the SARS-CoV-2 genome in these patients might facilitate the origin of new VOCs that might subsequently spread in the general community.

Epidemiology, Impact, and Management Strategies of Anti-Glomerular Basement Membrane Disease

Anti-glomerular basement membrane (anti-GBM) disease is a rare but serious autoimmune disease, which is characterized by the development of pathogenic antibodies to type IV collagen antigens in the glomerular and alveolar basement membranes. This results in rapidly progressive glomerulonephritis (GN), alveolar hemorrhage, or both. A variety of environmental factors can trigger the disease in genetically predisposed patients. Temporal associations with influenza, SARS-CoV-2 infection, and COVID-19 vaccination have been described although there is insufficient evidence to suggest causality. Anti-GBM disease accounts for approximately 20% of the cases of rapidly progressive GN cases secondary to crescentic GN, but is an uncommon cause of end-stage kidney disease. Early diagnosis by detection of circulating antibodies, increased awareness of atypical as well as complex clinical variants of the disease, and combined therapy with immunosuppression and plasma exchange has improved the prognosis of patients with this potentially fatal disease. Progress has been hampered by the rarity of anti-GBM disease, but new agents and therapeutic regimens are emerging.

Patient parameters and response after administration of rituximab in pediatric mature B-cell non-Hodgkin lymphoma

BACKGROUND

Mature aggressive B-cell lymphomas are heterogenous malignancies that make up more than half of all diagnosed non-Hodgkin lymphoma in children and adolescents. The overall survival rate increased over the last decades to 80%-90% due to fine tuning of polychemotherapy. However, new therapeutic implications are needed to further increase the overall survival. Current clinical trials analyze the therapeutic effect of rituximab in pediatric patients, while the mechanism of action in vivo is still not fully understood.

METHODS

Effector molecules important for tumor defense were analyzed before and at day 5 after rituximab treatment via flow cytometry. Serum rituximab levels were measured with an ELISA.

RESULTS

We evaluated patient parameters that may affect treatment response in relation to rituximab administration and serum rituximab levels. We indeed found a reduction of Fcγ receptor (FcγR) II levels after rituximab treatment in monocyte subtypes, whereas FcγRI expression was significantly increased. Serum levels of proinflammatory marker proteins S100A8/A9 and S100A12 significantly decreased after treatment to normal levels from an overall proinflammatory state before treatment. CD57, perforin, and granzyme B expression decreased after treatment, comprising a less cytolytic natural killer (NK) cell population.

CONCLUSION

The highlighted effects of rituximab treatment on patient's immune response help in understanding the biology behind tumor defense mechanisms and effector function. After subsequent studies, these novel insights might be translated into patient care and could contribute to improve treatment of pediatric patients with mature aggressive B-cell lymphoma.

Resemblance-Ranking Peptide Library to Screen for Binders to Antibodies on a Peptidomic Scale

A novel resemblance-ranking peptide library with 160,000 10-meric peptides was designed to search for selective binders to antibodies. The resemblance-ranking principle enabled the selection of sequences that are most similar to the human peptidome. The library was synthesized with ultra-high-density peptide arrays. As proof of principle, screens for selective binders were performed for the therapeutic anti-CD20 antibody rituximab. Several features in the amino acid composition of antibody-binding peptides were identified. The selective affinity of rituximab increased with an increase in the number of hydrophobic amino acids in a peptide, mainly tryptophan and phenylalanine, while a total charge of the peptide remained relatively small. Peptides with a higher affinity exhibited a lower sum helix propensity. For the 30 strongest peptide binders, a substitutional analysis was performed to determine dissociation constants and the invariant amino acids for binding to rituximab. The strongest selective peptides had a dissociation constant in the hundreds of the nano-molar range. The substitutional analysis revealed a specific hydrophobic epitope for rituximab. To show that conformational binders can, in principle, be detected in array format, cyclic peptide substitutions that are similar to the target of rituximab were investigated. Since the specific binders selected via the resemblance-ranking peptide library were based on the hydrophobic interactions that are widespread in the world of biomolecules, the library can be used to screen for potential linear epitopes that may provide information about the cross-reactivity of antibodies.

Epitope Mapping of the Anti-CD20 Monoclonal Antibodies (C20Mab-11 and 2H7) Using HisMAP Method

CD20, which is expressed on B lymphocytes, has been studied as a therapeutic target for B cell lymphomas and autoimmune disorders. Identifying the binding epitopes of monoclonal antibodies (mAbs) can contribute to our understanding of their functions. We have previously developed an anti-CD20 mAb (clone C₂₀Mab-11) using a Cell-Based Immunization and Screening (CBIS) method. In this study, we aimed to determine the binding epitopes of anti-CD20 mAbs, such as C₂₀Mab-11 and 2H7, using the His-tag insertion for epitope mapping (HisMAP). The results showed that ₁₇₁-NPSE-₁₇₄ and ₁₆₈-EPANPSE-₁₇₄ in the second loop of CD20 were essential for C₂₀Mab-11 binding and 2H7 binding, respectively. Although we developed many mAbs that recognize conformational epitopes using the CBIS method, there are many difficulties in epitope mapping for these mAbs. HisMAP could be useful for determining the conformational epitopes of other mAbs against membrane proteins.

Epitope Mapping of Rituximab Using HisMAP Method

CD20 is expressed in the B lymphocyte, and an effective target for the detection and treatment of B cell lymphomas. Therefore, CD20 has been studied as a therapeutic target of B cell lymphomas and autoimmune disorders. Specific anti-CD20 monoclonal antibodies (mAbs), such as rituximab, ofatumumab, veltuzumab, and ocaratuzumab, have been developed. Revealing the recognition mechanism of antigen by mAbs could contribute to understanding the function of mAbs and could be useful for the development of vaccine. Rituximab is a mouse-human chimeric anti-CD20 mAb, which was developed and approved for the treatment of the B cell malignancies. Hence, the binding epitope of rituximab for CD20 has been studied. Some reports show that ₁₇₀-ANPS-₁₇₃, especially Ala170 and Pro172 of CD20 are important for rituximab binding. However, only phage display results showed that ₁₈₂-YCYSI-₁₈₆ of CD20 is also important for rituximab binding to CD20. In this study, we tried to determine the binding epitope of rituximab for CD20 using histidine-tag insertion for epitope mapping (HisMAP) method. The results showed that two regions of CD20 (₁₆₉-PANPSE-₁₇₄ and ₁₈₃-CYSIQ-₁₈₇) are important for rituximab-binding for CD20.

Longitudinal analysis of urinary proteins in lupus nephritis - A pilot study

Approximately 30% of adult-onset systemic lupus erythematosus (SLE) patients develop lupus nephritis (LN). The gold standard for LN detection involves renal biopsies, invasive procedures not suitable for routine disease monitoring. A urinary biomarker panel comprised of lipocalin-like prostaglandin D synthase (LPGDS), transferrin, alpha-1-acid glycoprotein (AGP-1), ceruloplasmin, monocyte chemoattractant protein 1 (MCP-1) and soluble vascular cell adhesion molecule-1 (sVCAM-1) has shown promise to predict LN and response to rituximab at baseline. Whether these proteins predict LN during longitudinal sampling, however, remained unknown. Here, we quantified aforementioned urinary proteins at baseline (N = 25), six and twelve months (N = 17 each) after rituximab treatment. Urine MCP-1 (at six and twelve months) and AGP-1 (at twelve months) levels varied between patients with active vs mildly active/inactive LN. Findings support the use of urinary proteins to detect active LN in ongoing disease monitoring in adult-onset SLE patients, but need to be validated in larger cohorts.

CD19-Targeted Immunotherapies for Diffuse Large B-Cell Lymphoma

Surgical resection, chemotherapy and radiotherapy were, for many years, the only available cancer treatments. Recently, the use of immune checkpoint inhibitors and adoptive cell therapies has emerged as promising alternative. These cancer immunotherapies are aimed to support or harness the patient's immune system to recognize and destroy cancer cells. Preclinical and clinical studies, based on the use of T cells and more recently NK cells genetically modified with chimeric antigen receptors retargeting the adoptive cell therapy towards tumor cells, have already shown remarkable results. In this review, we outline the latest highlights and progress in immunotherapies for the treatment of Diffuse Large B-cell Lymphoma (DLBCL) patients, focusing on CD19-targeted immunotherapies. We also discuss current clinical trials and opportunities of using immunotherapies to treat DLBCL patients.

The immunologic balance: three cases of rituximab-associated melanoma

Currently, there is no known clinical evidence that rituximab increases the rate of subsequent primary malignancies; however, some studies have raised the question of increased melanoma risk following rituximab treatment for non-Hodgkin lymphoma. We report three interesting cases of suspected rituximab-induced melanoma. We hypothesize that this association is secondary to rituximab-driven shifts in the immunologic balance. Based on these cases, it is possible that the number of post-rituximab melanoma cases is underreported. Further mechanistic research into individual cases and population-level studies are required to better define association and risk; however, given the increasing prevalence of oncologic and nononcologic rituximab use, awareness across all fields is essential.

2021 update on thyroid-associated ophthalmopathy

PURPOSE

Our understanding of thyroid-associated ophthalmopathy (TAO, A.K.A Graves' orbitopathy, thyroid eye disease) has advanced substantially, since one of us (TJS) wrote the 2010 update on TAO, appearing in this journal.

METHODS

PubMed was searched for relevant articles.

RESULTS

Recent insights have resulted from important studies conducted by many different laboratory groups around the World. A clearer understanding of autoimmune diseases in general and TAO specifically emerged from the use of improved research methodologies. Several key concepts have matured over the past decade. Among them, those arising from the refinement of mouse models of TAO, early stage investigation into restoring immune tolerance in Graves' disease, and a hard-won acknowledgement that the insulin-like growth factor-I receptor (IGF-IR) might play a critical role in the development of TAO, stand out as important. The therapeutic inhibition of IGF-IR has blossomed into an effective and safe medical treatment. Teprotumumab, a β-arrestin biased agonist monoclonal antibody inhibitor of IGF-IR has been studied in two multicenter, double-masked, placebo-controlled clinical trials demonstrated both effectiveness and a promising safety profile in moderate-to-severe, active TAO. Those studies led to the approval by the US FDA of teprotumumab, currently marketed as Tepezza for TAO. We have also learned far more about the putative role that CD34⁺ fibrocytes and their derivatives, CD34⁺ orbital fibroblasts, play in TAO.

CONCLUSION

The past decade has been filled with substantial scientific advances that should provide the necessary springboard for continually accelerating discovery over the next 10 years and beyond.

Vaccine-induced thrombotic thrombocytopenia following coronavirus vaccine: A narrative review

The novel coronavirus pandemic has taken a toll on the global healthcare systems and economy. Safety precautions, along with vaccination, are the most effective preventive measures. The global vaccination program against COVID-19 has dramatically reduced the number of deaths and cases. However, the incidence of thrombotic events and thrombocytopenia post-COVID-19 vaccination known as vaccine-induced thrombotic thrombocytopenia has raised safety concerns. This has led to an element of vaccine hesitancy. The exact mechanism for vaccine-induced thrombotic thrombocytopenia is unknown. Although the incidence of thrombosis associated with COVID-19 vaccination is low, it still requires attention, especially in older people, smokers, and people with preexisting comorbidities. This study aims to review the pathophysiology, diagnosis, and management of vaccine-induced thrombotic thrombocytopenia, to provide a concise and comprehensive update.

New Indications and platforms for CAR-T therapy in lymphomas beyond DLBCL

CD19 directed chimeric antigen receptor T-cell therapy (CAR-T) represents a significant advancement for patients with relapsed/refractory large B-cell lymphoma (LBCL). Long term follow-up confirms durable remissions in nearly half of the patients, a population which was previously estimated to have a median survival of around 6 months with standard salvage therapy. This initial success of CAR-T has led to significant expansion across other lymphoma histologies resulting in the recent regulatory approval of CAR-T in mantle cell lymphoma and follicular lymphoma. Additionally, multiple novel platforms of CAR-T therapy are under development to improve efficacy and limit toxicity such dual antigen targeting, allogeneic and natural killer CAR's. In this review, we focus on the new indications of CAR-T in lymphomas beyond LBCL as well as emerging platforms of CAR-T therapy.

Molecular Therapy in Myasthenia Gravis

Myasthenia gravis (MG) is an autoimmune disorder caused by antibodies that act against the myoneural junction. Conventional immunosuppressants such as corticosteroids, azathioprine and mycophenolate are associated with long-term side effects and many patients do not achieve remission and may become refractory. Thus, there is an unmet need for target-specific therapies that act faster, have fewer side effects and lead to stable disease remission. However, many of the novel therapeutic agents being described are not meeting their primary endpoints. We reviewed the current status of novel immunotherapies for MG, their mechanisms of action, along with the side effect profiles. Fast onset of action, sustained disease remission and relatively low frequency of side effects of the new agents are attractive. However, the unknown long-term safety and high cost are precluding factors. Better preclinical studies and more randomized trials are needed before novel agents are routinely employed.

The molecular ontogeny of follicular lymphoma: gene mutations succeeding the BCL2 translocation define common precursor cells

Relapsed follicular lymphoma (FL) can arise from common progenitor cells (CPCs). Conceptually, CPC-defining mutations are somatic alterations shared by the initial and relapsed tumours, mostly B-cell leukaemia/lymphoma 2 (BCL2)/immunoglobulin heavy locus (IGH) translocations and other recurrent gene mutations. Through complementary approaches for highly sensitive mutation detection, we do not find CPC-defining mutations in highly purified BCL2/IGH-negative haematopoietic progenitor cells in clinical remission samples from three patients with relapsed FL. Instead, we find cells harbouring the same BCL2/IGH translocation but lacking CREB binding protein (CREBBP), lysine methyltransferase 2D (KMT2D) and other recurrent gene mutations. Thus, (i) the BCL2/IGH translocation can precede CPC-defining mutations in human FL, and (ii) BCL2/IGH-translocated cells can persist in clinical remission.

Epitope Mapping of an Anti-CD20 Monoclonal Antibody (C20Mab-60) Using the HisMAP Method

CD20 is one of the B-lymphocyte antigens and an effective target for the detection and treatment of B cell lymphomas; specific and sensitive monoclonal antibodies (mAbs) are required thus for their diagnosis. Recently, we developed a novel anti-CD20 mAb (clone C₂₀Mab-60), which is not only useful for flow cytometry but also for Western blot and immunohistochemical analyses. However, the epitope of C₂₀Mab-60 has not been determined. To clarify the binding region of mAbs against their target molecules, it is essential to understand the pharmacological function of each mAb. In this study, we aimed to identify the epitope of C₂₀Mab-60 for CD20 using the novel histidine tag (His-tag) insertion for epitope mapping (HisMAP) method. We first established an anti-His-tag mAb, HisMab-1 (mouse IgG_2b, kappa), by immunizing mice with recombinant proteins containing an N-terminal His-tag. Although HisMab-1 detected the 4x, 5x, and 6xHis tag-inserted CD20 proteins using flow cytometry, 5xHis tag was selected. While HisMab-1 recognized all the 5xHis tag-inserted CD20 from the 142nd to the 183rd amino acid (aa), C₂₀Mab-60 did not react with the 5xHis tag-inserted CD20 from the 171st to the 174th aa. These results indicate that the main epitope of C₂₀Mab-60 for CD20 is a peptide from 171st to 174th aa of CD20. HisMAP method could be advantageous in the determination of the critical epitope of functional mAbs against many target molecules.

Epitope Mapping of an Anti-CD20 Monoclonal Antibody (C20Mab-60) Using Enzyme-Linked Immunosorbent Assay

CD20 is a glycosylated transmembrane protein and is expressed on normal B cells and B cell malignancies. Therapeutic antibodies against CD20 are developed and used in clinic. The understanding of antibody-antigen binding by revealing the epitope is essential for future application to antibody technology. Previously, we developed an anti-human CD20 monoclonal antibody, C₂₀Mab-60 (IgG_2a, kappa), using the Cell-Based Immunization and Screening (CBIS). C₂₀Mab-60 can be used for flow cytometry, Western blot, and immunohistochemical analyses. In this study, we examined the critical epitope of C₂₀Mab-60 using enzyme-linked immunosorbent assay (ELISA) with synthesized peptides. We performed ELISA with deletion mutants, and C₂₀Mab-60 reacted to the 160-179 amino acids sequence of CD20. Next, we analyzed the reaction to 20 point mutants, and C₂₀Mab-60 did not recognize the alanine-substituted peptides of N171A, P172A, S173A, and E174A. The results indicate that the binding epitope of C₂₀Mab-60, developed by CBIS, includes Asn171, Pro172, Ser173, and Glu174 of CD20.

Use of Rituximab for persistent EBV DNAemia, and Its effect on donor-specific antibody development in pediatric renal transplant recipients: A case series

INTRODUCTION

Persistent EBV DNAemia (PEBV) is associated with late-onset PTLD. The efficacy of rituximab in PEBV is not conclusive. We monitored PEBV and DSA in pediatric kidney transplant patients with or without rituximab.

METHODS

13 PEBV patients received standard treatment with immunosuppression reduction and valganciclovir, with or without IVIG; 5/13 were further treated with rituximab.

RESULTS

All Rituximab-treated and 6/7 No-Rituximab patients were EBV seronegative at transplant and seroconverted post-transplant. Peak EBV PCR levels were lower in No-Rituximab than Rituximab patients and all No-Rituximab patients cleared PEBV after standard treatment. Additional 1-2 doses of rituximab reduced EBV PCR levels in all 5 Rituximab patients, 3 cleared PEBV. One No-Rituximab patient developed localized PLTD. None of Rituximab patients developed de novo DSA, while 4/8 No-Rituximab patients did: 2/4 had ABMR. 1/5 Rituximab and 5/8 No-Rituximab patients had acute rejection. There was no change in eGFR between pre-EBV DNAemia and follow-up in Rituximab patients, while reduction in No-Rituximab patients was found. There was no difference in graft and patient survival.

CONCLUSIONS

While early intervention with rituximab in pediatric patients with PEBV may reduce viral load and PTLD, we observed a slower development of de novo DSA, and rejection and maintenance of eGFR.

Predictors of relapse and preventative strategies in immune thrombotic thrombocytopenic purpura

INTRODUCTION

Immune-mediated thrombotic thrombocytopenic purpura (iTTP) is a rare autoimmune blood disorder, which presents with microangiopathic hemolytic anemia, thrombocytopenia, and microvascular thrombosis and is caused by severe deficiency of ADAMTS13. iTTP may result in both acute and chronic complications and is rapidly fatal without expedient treatment. Life-time risk of relapse is approximately 40%.

AREAS COVERED

A number of predictors of relapse has been described in the literature. The most well-studied predictor of relapse is persistent ADAMTS13 deficiency; however, it is not a perfect marker. Relapse can be prevented by treatment with immunosuppressive medications, with rituximab being the most studied.

EXPERT OPINION

Patients who recover from iTTP should be regularly assessed, including with ADAMTS13 activity testing. The optimal frequency of assessments has not been established, but every 3 months is recommended. Considering the potential for significant organ damage and mortality associated with iTTP relapse, patients in remission and with persistent ADAMTS13 activity of 10-20% should be prophylactically treated with immunosuppression. Additional markers to precisely identify patients at higher risk of relapse are needed.

Rituximab Administration during the 2nd Trimester of Pregnancy for Systemic Lupus Erythematosus: Case Report and Review of the Literature in Rheumatic Disease

Rituximab is an anti-CD20 monoclonal antibody that is used in the treatment of many rheumatic diseases, for both licensed and unlicensed indications. Due to concerns regarding foetal B cell depletion and possible infection, there is conflicting advice about whether the drug should be administered during pregnancy, with some organizations advising administration if the potential benefit to the mother outweighs the risk to the foetus and some advising stopping rituximab six months prior to conception. Caution in particular is advised about administering rituximab in later trimesters when maternal IgG is transported across the placenta. There has been little literature thus far examining the safety of administering rituximab from the second trimester onwards in rheumatic diseases. We present a case where rituximab was used during the second trimester for the treatment of refractory systemic lupus erythematosus, without adverse effect on the neonate.

Born to survive: how cancer cells resist CAR T cell therapy

Although chimeric antigen receptor T cells demonstrated remarkable efficacy in patients with chemo-resistant hematologic malignancies, a significant portion still resist or relapse. This immune evasion may be due to CAR T cells dysfunction, a hostile tumor microenvironment, or resistant cancer cells. Here, we review the intrinsic resistance mechanisms of cancer cells to CAR T cell therapy and potential strategies to circumvent them.

Comparison of CD20 Binding Affinities of Rituximab Produced in Nicotiana benthamiana Leaves and Arabidopsis thaliana Callus

Plants are promising drug-production platforms with high economic efficiency, stability, and convenience in mass production. However, studies comparing the equivalency between the original antibodies and those produced in plants are limited. Amino acid sequences that constitute the Fab region of an antibody are diverse, and the post-transcriptional modifications that occur according to these sequences in animals and plants are also highly variable. In this study, rituximab, a blockbuster antibody drug used in the treatment of non-Hodgkin's lymphoma, was produced in Nicotiana benthamiana leaves and Arabidopsis thaliana callus, and was compared to the original rituximab produced in CHO cells. Interestingly, the epitope recognition and antigen-binding abilities of rituximab from N. benthamiana leaves were almost lost. In the case of rituximab produced in A. thaliana callus, the specific binding ability and CD20 capping activity were maintained, but the binding affinity was less than 50% of that of original rituximab from CHO cells. These results suggest that different plant species exhibit different binding affinities. Accordingly, in addition to the differences in PTMs between mammals and plants, the differences between the species must also be considered in the process of producing antibodies in plants.

Diving into the mechanism of action of tumor immunotherapies with intravital imaging

The clinical successes and tremendous hopes raised by tumor immunotherapies such as tumor-targeting monoclonal antibodies, immune checkpoint blockers, or CAR T cells demand that we better understand how these treatments precisely act in the patient body. Such a detailed knowledge is indeed essential to optimize therapeutical efficacy and maximize the number of cancer patients that could benefit from these therapies. This review aims to illustrate that intravital two-photon imaging is providing unique insights into the mode of action of tumor immunotherapies and is helping identify their critical bottlenecks in vivo. Moreover, this article discusses how spatiotemporal observations of immune cells, tumor subclones, and cytokine dynamics in the tumor microenvironment may contribute to the emergence of new concepts in anti-tumor immune responses.

Promise and pitfalls of allogeneic chimeric antigen receptor therapy in plasma cell and lymphoid malignancies

Chimeric antigen receptor (CAR) T-cell therapy is a promising immunotherapy in haematological malignancies. However, the currently approved products are generated from autologous T cells that require orchestration of several logistically complex steps, which include patient eligibility, apheresis capability, complex manufacturing processes and shipping logistics. Use of third-party donor-derived (allogeneic) effector cells that allows the generation of 'off-the-shelf" CAR T cells (allo-CAR) could circumvent many of the problems associated with autologous CAR T-cell therapy. Several allogeneic products are entering clinical trials, and though early, the results look promising. The recognised potential benefits of allo-CAR do not come without significant challenges, that must be overcome for their widespread use. Alloreactivity, i.e. graft-versus-host disease (GVHD), and rejection of donor T cells is one of the major barriers, while other potential barriers include immunogenicity, unknown in vivo persistence, and CAR T-cell yield. In the present review, we provide a comprehensive review of the challenges associated with autologous CAR, the benefits and potential challenges associated with allo-CAR. Finally, we review the available platforms for allo-CAR for B-cell and plasma cell malignancies.

Anti-osteosarcoma effect of antiserum against cross antigen TPD52 between osteosarcoma and Trichinella spiralis

BACKGROUND

Trichinella spiralis (T. spiralis) is a parasite occurring worldwide that has been proven to have antitumour ability. However, studies on the antitumour effects of cross antigens between the tumour and T. spiralis or antibodies against cross antigens between tumours and T. spiralis are rare.

METHODS

To study the role of cross antigens between osteosarcoma and T. spiralis, we first screened the cDNA expression library of T. spiralis muscle larvae to obtain the cross antigen gene tumour protein D52 (TPD52), and prepared fusion protein TPD52 and its antiserum. The anti-osteosarcoma effect of the anti-TPD52 antiserum was studied using cell proliferation and cytotoxicity assays as well as in vivo animal models; preliminary data on the mechanism were obtained using western blot and immunohistochemistry analyses.

RESULTS

Our results indicated that TPD52 was mainly localized in the cytoplasm of MG-63 cells. Anti-TPD52 antiserum inhibited the proliferation of MG-63 cells and the growth of osteosarcoma in a dose-dependent manner. The tumour inhibition rate in the 100 μg treatment group was 61.95%. Enzyme-linked immunosorbent assay showed that injection of anti-TPD52 antiserum increased the serum levels of IFN-γ, TNF-α, and IL-12 in nude mice. Haematoxylin and eosin staining showed that anti-TPD52 antiserum did not cause significant pathological damage. Apoptosis of osteosarcoma cells was induced by anti-TPD52 antiserum in vivo and in vitro.

CONCLUSIONS

Anti-TPD52 antiserum exerts an anti-osteosarcoma effect by inducing apoptosis without causing histopathological damage.

The Effect of Immunomodulatory Treatments on Anti-Dystrophin Immune Response After AAV Gene Therapy in Dystrophin Deficient mdx Mice

BACKGROUND

AAV-based gene therapy is an attractive approach to treat Duchenne muscular dystrophy (DMD) patients. Although the long-term consequences of a gene therapy approach for DMD are unknown, there is evidence in both DMD patients and animal models that dystrophin replacement by gene therapy leads to an anti-dystrophin immune response that is likely to limit the long-term use of these therapeutic strategies.

OBJECTIVE

Our objective is to test whether the anti-dystrophin immune response is affected by immunomodulatory drugs in mdx mice after rAAV gene therapy.

METHODS

mdx mice were treated with rAAV microdystrophin alone or in combination with immunomodulatory drugs. Dystrophin expression in skeletal muscle was assessed by mass spectrometry. Immune responses were assessed by immunophenotyping, western blot for anti-dystrophin antibodies and flow cytometry assays for antigen-specific T-cell cytokine expression. The impact on muscle was measured by grip strength assessment, in vivo torque, optical imaging for inflammation and H&E staining of sections to assess muscle damage.

RESULTS

We found that AAV-9-microdystrophin gene therapy induced expression of microdystrophin, anti-dystrophin antibodies, and T-cell cytokine responses. Immunomodulatory treatments, rituximab and VBP-6 completely abrogated the anti-dystrophin antibody response. Prednisolone, CTLA4-Ig, and Eplerenone showed variable efficacy in blocking the anti-dystrophin immune response. In contrast, none of the drugs completely abrogated the antigen specific IFN-γ response. AAV-microdystrophin treatment significantly reduced inflammation in both forelimbs and hindlimbs, and the addition of prednisolone and VBP6 further reduced muscle inflammation. Treatment with immunomodulatory drugs, except eplerenone, enhanced the beneficial effects of AAV-microdystrophin therapy in terms of force generation.

CONCLUSIONS

Our data suggest that AAV-microdystrophin treatment results in anti-dystrophin antibody and T-cell responses, and immunomodulatory treatments have variable efficacy on these responses.

ABO incompatibility in renal transplantation

ABO blood group incompatibility (ABO-I) was historically considered an absolute contraindication to kidney transplantation due to the significant risk of acute antibody-mediated rejection and early graft loss. Nevertheless, the urge to minimize the gap between the candidates’ number on the waitlist for kidney transplants and the available kidney donors encourage investigation into finding ways to use organs from ABO-I kidney donors, especially in the era of using more potent immunosuppression therapies. This review aims to discuss a general overview of ABO-I kidney transplantation and the different protocols adopted by some transplant centers to meaningfully overcome this barrier.

Bi-specific and Tri-specific NK Cell Engagers: The New Avenue of Targeted NK Cell Immunotherapy

Natural killer (NK) cell-mediated cancer immunotherapy has grown significantly over the past two decades. More recently, multi-specific engagers have been developed as cancer therapeutics to effectively arm endogenous NK cells to more potently induce specific cytolytic responses against tumor targets. This review explores the bi- and tri-specific NK/tumor engagers that are emerging as a new generation of immunotherapeutics. These molecules vary in configuration, but they typically have small molecular weights and domains that engage specific tumor antigens and NK cell-activating receptors such as CD16, NKp30, NKp46, and NKG2D. They have demonstrated compelling potential in boosting NK cell cytotoxicity against specific tumor targets. This highly adaptable off-the-shelf platform, which in some formats also integrates cytokines, is poised to revolutionize targeted NK cell immunotherapy, either as a monotherapy or in combination with other effective anti-cancer therapies.

The evolution of commercial drug delivery technologies

Drug delivery technologies have enabled the development of many pharmaceutical products that improve patient health by enhancing the delivery of a therapeutic to its target site, minimizing off-target accumulation and facilitating patient compliance. As therapeutic modalities expanded beyond small molecules to include nucleic acids, peptides, proteins and antibodies, drug delivery technologies were adapted to address the challenges that emerged. In this Review Article, we discuss seminal approaches that led to the development of successful therapeutic products involving small molecules and macromolecules, identify three drug delivery paradigms that form the basis of contemporary drug delivery and discuss how they have aided the initial clinical successes of each class of therapeutic. We also outline how the paradigms will contribute to the delivery of live-cell therapies.

The Synergistic Anti-Tumor Activity of EZH2 Inhibitor SHR2554 and HDAC Inhibitor Chidamide through ORC1 Reduction of DNA Replication Process in Diffuse Large B Cell Lymphoma

Simple Summary

The EZH2-targeted drugs have demonstrated notable therapeutic effects in EZH2 mutant B-cell lymphoma patients. In this study, we demonstrated that the combination of EZH2 inhibitor SHR2554 and HDAC inhibitor HBI8000 exert synergistic anti-proliferative activity in both EZH2 wide-type and mutation B-cell lymphoma. More importantly, gene expression profile analysis revealed simultaneous treatment with these agents led to dramatic inhibition of DNA replication initiator protein ORC1, which might contribute to great efficacy of combination strategy. The combination of EZH2 inhibitor and HDAC inhibitor could provide a potential therapeutic treatment for both EZH2 wide-type and mutation B-cell lymphoma patients.

Abstract

Background: Upregulation of H3K27me3 induced by EZH2 overexpression or somatic heterozygous mutations were implicated in lymphomagenesis. It has been demonstrated that several EZH2-target agents have notable therapeutic effects in EZH2-mutant B-cell lymphoma patients. Here we present a novel highly selective EZH2 inhibitor SHR2554 and possible combination strategy in diffuse large B-cell lymphoma (DLBCL). Methods: Cell proliferation, cell cycle and apoptosis were analyzed by CellTiter-Glo Luminescent Cell Viability Assay and flow cytometry. Western Blot was used to detect the expression of related proteins. The gene expression profiling post combination treatment was analyzed by RNA-Seq. Finally, CDX and PDX models were used to evaluate the synergistic anti-tumor effects of the combination treatment in vivo. Results: The novel EZH2 inhibitor SHR2554 inhibited proliferation and induced G1 phase arrest in EZH2-mutant DLBCL cell lines. The combination of EZH2 inhibitor SHR2554 with histone deacetylase (HDAC) inhibitor chidamide (hereafter referred to as HBI8000) exerted synergistic anti-proliferative activity in vitro and in vivo. Gene expression profile analysis revealed dramatic inhibition of the DNA replication process in combined treatment. Conclusions: SHR2554, a potent, highly selective small molecule inhibitor of EZH2, inhibited EZH2-mutant DLBCL more significantly in vitro and in vivo. The combination of HDAC inhibitor HBI8000 with EZH2 inhibitor SHR2554 exhibited dramatic anti-tumor activity in both mutant and wild-type DLBCL, which may become a potential therapeutic modality for the treatment of DLBCL patients.

Incidence, clinical presentation, relapses and outcome of SARS-CoV-2 infection in patients treated with anti-CD20 monoclonal antibodies

BACKGROUND

Our objective is to describe the presentation and complications, including relapses, of COVID-19 in patients under anti-CD20 treatments. In addition, to describe viral clearance and determine the safety of reintroducing anti-CD20 treatment.

METHODS

Retrospective cohort study of 422 patients under anti-CD20 treatment that was administered from January 1, 2019, to December 31, 2020.

RESULTS

Fifty-seven patients were diagnosed of COVID-19 (13.5%). 25 patients (43.9%) required hospital admission. 5 patients died (8.8%), 10 developed severe COVID-19 and acute respiratory distress syndrome. Mortality rate was higher among patients infected during the first 3 months following the last dose of anti-CD20 (14.7% vs 0%, p=0,046).The median time of persistence of positive RT-PCR was 22 days (IQR 13-40). Nine out of 52 survivors (17.3%) presented relapses. All of them received the last dose of anti-CD20 less than 6 months before the COVID-19 episode. Clinical presentation was fever (n=8; 88.9%), dyspnea (n=7; 77.8%), cough (n=7; 77.8%), worsening of previous infiltrates (n=5; 55.6%) and new pulmonary infiltrates (n=8; 88.9%). An increase in lymphocytes with CD4/CD8 ratio inversion was observed in all cases. Among the 25 patients who resumed anti-CD20 drug, 4 (16.0%) presented relapses vs 5/28 among those who did not (17.9%), (p=0.857).

CONCLUSION

Patients infected with SARS-CoV-2 during the 6 months after anti-CD20 administration had a worse outcome and a higher mortality rate. The duration of infectivity may be longer. Relapses of COVID-19 occurred in more than 15% and were associated with viral replication. Once the infection is resolved, it is safe to restart treatment with anti-CD20.

Pyruvate dehydrogenase kinase 4-mediated metabolic reprogramming is involved in rituximab resistance in diffuse large B-cell lymphoma by affecting the expression of MS4A1/CD20

Diffuse large B cell lymphoma (DLBCL) heterogeneity promotes recurrence and anti‐CD20‐based therapeutic resistance. Previous studies have shown that downregulation of MS4A1/CD20 expression after chemoimmunotherapy with rituximab leads to rituximab resistance. However, the mechanisms of CD20 loss remain unknown. We identified that pyruvate dehydrogenase kinase 4 (PDK4) is markedly elevated in DLBCL cells derived from both patients and cell lines with R‐CHOP (rituximab plus cyclophosphamide, doxorubicin, vincristine, and prednisone) resistance. We found that overexpression of PDK4 in DLBCL cells resulted in cell proliferation and resistance to rituximab in vitro and in vivo. Furthermore, loss of PDK4 expression or treatment with the PDK4 inhibitor dichloroacetate was able to significantly increase rituximab‐induced cell apoptosis in DLBCL cells. Further studies suggested PDK4 mediates a metabolic shift, in that the main energy source was changed from oxidative phosphorylation to glycolysis, and the metabolic changes could play an important role in rituximab resistance. Importantly, by knocking down or overexpressing PDK4 in DLBCL cells, we showed that PDK4 has a negative regulation effect on MS4A1/CD20 expression. Collectively, this is the first study showing that targeting PDK4 has the potential to overcome rituximab resistance in DLBCL.

Non-clinical similarity of biosimilar ABP 798 with rituximab reference product

ABP 798 is a biosimilar to Rituxan® (rituximab reference product [RP]). Non-clinical assessments relevant to the primary and secondary mechanisms of action (MOA) contribute to the totality of the evidence (TOE) in supporting biosimilarity and are critical in providing scientific evidence for extrapolation of indications. Similarity of ABP 798 with rituximab RP was investigated across a range of biological activities which have potential impact on pharmacokinetics and clinical efficacy with non-clinical assessments relevant to MOA such as CD20 internalization, trogocytosis, binding to primary human natural killer (NK) cells as well as the ability to induce antibody-dependent cellular phagocytosis (ADCP) in peripheral blood mononuclear cells. Additionally, in vitro synergy of ABP 798 or RP with chemotherapeutic agents, in vivo xenograft studies in mice, and toxicological assessments in cynomolgus monkeys (including B cell depletion and toxicokinetics) were also conducted. Results from these non-clinical assessments contribute to the TOE supporting the biosimilarity between ABP 798 and rituximab RP across a range of primary and secondary MOAs and support justification for extrapolation to all indications of use for ABP 798 for which the RP is approved.