Modified Therapeutic Antibodies: Improving Efficacy

The prosperity of the biotherapeutics market reflects the feasibility and effectiveness of therapeutic antibodies for the treatment of cancers,inflammatory disorders,and refractory infections.As drawbacks emerge in clinical trials and practice,such as impeded binding,reduced effector functions,and frequent adverse reactions,modifications of therapeutic antibodies are unprecedently burgeoning in research and development(R&D).These modifications include:①modified glycosylation;②fragment of crystallizable domain(Fc)amino acid alterations;③cross-isotype or cross-subclass exchanges;④antibody–drug conjugates(ADCs);⑤single chain of variable region fragment(scFv)for chimeric antigen receptor T(CAR-T)cells;and⑥bispecific antibodies(bsAbs)in order to promote binding affinity,half-life in circulation,effectiveness toward target cells and,ultimately,to achieve overall improved efficacy.While many achievements have been made around the world in the past decades,China has been playing an active role in this realm,with its great demand for biotherapeutics with R&D potential.This review recapitulates the international progress that has been achieved with modified therapeutic antibodies,and then focuses on that of China in an independent section.

A reporter gene assay for determining the biological activity of therapeutic antibodies targeting TIGIT

T cell immunoglobulin and ITIM domain(TIGIT)is a novel immune checkpoint that has been considered as a target in cancer immunotherapy.Current available bioassays for measuring the biological activity of therapeutic antibodies targeting TIGIT are restricted to mechanistic investigations because donor primary T cells are highly variable.Here,we designed a reporter gene assay comprising two cell lines,namely,CHO-CD112-CD3 scFv,which stably expresses CD 112(PVRL2,nectin-2)and a membranebound anti-CD3 single-chain fragment variable(scFv)as the target cell,and Jurkat-NFAT-TIGIT,which stably expresses TIGIT as well as the nuclear factor of activated T-cells(NFAT)response element-controlled luciferase gene,as the effector cell.The anti-CD3 scFv situated on the target cells activates Jurkat-NFATTIGIT cells through binding and crosslinking CD3 molecules of the effector cell,whereas interactions between CD 112 and TIGIT prevent activation.The presence of anti-TIGIT mAbs disrupts their interaction,which in turn reverses the inactivation and luciferase expression.Optimization and validation studies have demonstrated that this assay is superior in terms of specificity,accuracy,linearity,and precision.In summary,this reliable and effective reporter gene assay may potentially be utilized in lot release control,stability assays,screening,and development of novel TIGIT-targeted therapeutic antibodies.

Recent progress in the molecular imaging of therapeutic monoclonal antibodies

Therapeutic monoclonal antibodies have become one of the central components of the healthcare system and continuous efforts are made to bring innovative antibody therapeutics to patients in need.It is equally critical to acquire sufficient knowledge of their molecular structure and biological functions to ensure the efficacy and safety by incorporating new detection approaches since new challenges like individual differences and resistance are presented.Conventional techniques for determining antibody disposition including plasma drug concentration measurements using LC-MS or ELISA,and tissue distribution using immunohistochemistry and immunofluorescence are now complemented with molecular imaging modalities like positron emission tomography and near-infrared fluorescence imaging to obtain more dynamic information,while methods for characterization of antibody’s interaction with the target antigen as well as visualization of its cellular and intercellular behavior are still under development.Recent progress in detecting therapeutic antibodies,in particular,the development of methods suitable for illustrating the molecular dynamics,is described here.

Structural basis of immunosuppression by the therapeutic antibody daclizumab

Interleukin-2 （IL）-2 signaling plays a pivotal role in the activation of immune responses, and drugs that block this pathway have been shown to be effective for the immunosuppression in patients with organ transplantation to alleviate/eliminate allograft rejection. The first humanized monoclonal antibody （mAb） daclizumab falls into this category and shows high specificity and affinity against a key component of the IL-2 receptor complex, namely IL-2Ra. To reveal the molecular mechanism of the inhibition of the IL-2 signaling pathway by dacllzumab, we determined the crystal structures of the daclizumab Fab in free form and in complex with the IL-2Ra ectodomain at 2.6 and 2.8 A resolution, respectively. The daclizumab Fab adopts a similar conformation in the presence or absence of the IL- 2Ra ectodomain. The antigen-binding site of daclizumab is mainly composed of live complementarity determining regions （CDRs） that form a large positively charged surface depression and two flanking patches that are generally hydrophobic. The conformational epitope consists of several discontinuous segments of the IL-2Ru ectodomain, a large portion of which overlaps with the regions that interact with IL-2, suggesting that the binding of daclizumab to IL-2Ra would prevent the IL-2 binding to IL-2Ra and the subsequent formation of the IL-2fIL-2Ra[~/c complex, and therefore block the IL-2 signaling pathway. These results also have implications for the design and development of improved mAb drugs targeting IL-2Ra.

Boosting of the enhanced permeability and retention effect with nanocapsules improves the therapeutic effects of cetuximab

Objective:The introduction of therapeutic antibodies(tAbs)into clinical practice has revolutionized tumor treatment strategies,but their tumor therapy efficiency is still far below expectations because of the rapid degradation and limited tumor accumulation of tAbs.Methods:We developed a nanocapsule-based delivery system to induce the self-augmentation of the enhanced permeability and retention(EPR)effect.This system constantly penetrated across the blood-tumor barrier into the tumor while avoiding the attack of tAbs by the immune system.The biodistribution and therapeutic effect were tested with single dose administration of nanocapsule-tAbs in vivo.Results:The accumulation of Nano(cetuximab)within subcutaneous PC9 tumors was gradually enhanced over 6 days after single dose administration,which was contrary to the biodistribution of native cetuximab.Nano(cetuximab)accumulated in tumor tissues via the EPR effect and released cetuximab.The released cetuximab acted on vascular endothelial cells to destroy the blood-tumor barrier and induce self-augmentation of the EPR effect,which in turn contributed to further tumor accumulation of long-circulating Nano(cetuximab).Compared with single dose administration of native cetuximab,Nano(cetuximab)showed an effective tumor suppressive effect for 3 weeks.Conclusions:The nanocapsule-based delivery system efficiently delivered tAbs to tum or tissues and released them to boost the EPR effect,which facilitated further tumor accumulation of the tAbs.This novel self-augmentation of the EPR effect facilitated by the biological characteristics of tAbs and nanotechnology contributed to the improvement of the therapeutic effect of tAbs,and stimulated new ideas for antibody-based tumor therapy.

Monoclonal antibodies-a proven and rapidly expanding therapeutic modality for human diseases

The study of antibodies has been a focal point in modern biology and medicine since the early 1900s.However,progress in therapeutic antibody development was slow and intermittent until recently.The first antibody therapy,murine-derived murononab OKT3 for acute organ rejection,was approved by the US Food and Drug Administration(FDA)in 1986,more than a decade after César Milstein and Georges Köhler developed methods for the isolation of mouse monoclonal antibodies from hybridoma cells in 1975.As a result of the scientific,technological,and clinical breakthroughs in the 1980s and 1990s,the pace of therapeutic antibody discovery and development accelerated.Antibodies are becoming a major drug modality with more than two dozen therapeutic antibodies in the clinic and hundreds more in development.Despite the progress,need for improvement exists at every level.Antibody therapeutics provides fertile ground for protein scientists to fulfill the dream of personalized medicine through basic scientific discovery and technological innovation.

Antibody to El peptide of hepatitis C virus genotype 4 inhibits virus binding and entry to HepG2 cells in vitro

AIM： To analyze the neutralizing activity of antibodies against E1 region of hepatitis C virus （HCV）. Specific polydonal antibody was raised via immunization of New Zealand rabbits with a synthetic peptide that had been derived from the E1 region of HCV and was shown to be highly conserved among HCV published genotypes. METHODS： Hyper-immune HCV E1 antibodies were incubated over night at 4 ℃ with serum samples positive for HCV RNA, with viral loads ranging from 615 to 3.2 million IU/mL. Treated sera were incubated with HepG2 cells for 90 min. Blocking of viral binding and entry into cells by anti E1 antibody were tested by means of RTPCR and flow cytometry. RESULTS： Direct immunostaining using FITC conjugated E1 antibody followed by Flow cytometric analysis showed reduced mean fluorescence intensity in samples pre-incubated with E1 antibody compared with untreated samples. Furthermore, 13 out of 18 positive sera （72%） showed complete inhibition of infectivity as detected by RT-PCR. CONCLUSION： In house produced E1 antibody, blocks binding and entry of HCV virion infection to target cells suggesting the involvement of this epitope in virus binding and entry. Isolation of these antibodies that block virus attachment to human cells are useful as therapeutic reagents.

Development and evaluation of neutralizing antibodies for cross-protection against West Nile virus and Japanese encephalitis virus

Background:West Nile virus is a severe zoonotic pathogen that can cause severe central nervous system symptoms in humans and horses,and is fatal for birds,chickens and other poultry.With no specific drugs or vaccines available,antibody-based therapy is a promising treatment.This study aims to develop neutralizing antibodies against West Nile virus and assess their cross-protective potential against Japanese encephalitis virus.Methods:Monoclonal antibodies against WNV and JEV were isolated by hybridoma technology.The therapeutic efficacy of these antibodies was evaluated using a mouse model,and a humanized version of the monoclonal antibody was generated for potential human application.Results:In this study,we generated eight monoclonal antibodies that exhibit neutralizing activity against WNV.Their therapeutic effects against WNV were validated both in vivo and in vitro.Among these antibodies,C9-G11-F3 also exhibited cross-protective activity against JEV.We also humanized the antibody to ensure that it could be used for WNV infection treatment in humans.Conclusion:This study highlights the importance of neutralizing antibodies as a promising approach for pro-tection against West Nile virus infection and suggests their potential utility in the development of therapeutic interventions.

Crystal clear： visualizing the intervention mechanism of the PD-1/PD-L1 interaction by two cancer therapeutic monoclonal antibodies

Antibody-based PD-IIPD-L1 blockade therapies have taken center stage in immunotherapies for cancer, with multiple clinical successes. PD-1 signaling plays pivotal roles in tumor-driven T-cell dysfunction. In contrast to prior approaches to generate or boost tumor-specific T-cell responses, antibody-based PD-1/PD-L1 blockade targets tumor-induced T-cell defects and restores pre- existing T-cell function to modulate antitumor immunity. in this review, the fundamental knowledge on the expression regulations and inhibitory functions of PD-1 and the present understanding of antibody-based PD-1/ PD-L1 blockade therapies are briefly summarized. We then focus on the recent breakthrough work concerning the structural basis of the PD-IIPD-Ls interaction and how therapeutic antibodies, pembrolizumab targeting PD-1 and avelumab targeting PD-L1, compete with the binding of PD-1/PD-L1 to interrupt the PD-1/PD-L1 interaction. We believe that this structural informationwill benefit the design and improvement of therapeutic antibodies targeting PD-1 signaling.

ANTITUMOR EFFECTS OF MONOCLONAL ANTIBODY FAB’FRAGMENT—CONTAINING IMMUNOCONJUGATES

Objective.Using monoclonal antibody (mAb) Fab′ fragment to develop mAb immunoconjugates for cancer. Methods.Fab′ fragment of mAb 3A5 was prepared by digestion of the antibody with pepsin and then reduced by dithiothreitol (DTT),while Fab′ fragment of mAb 3D6 was obtained by digestion of the antibody with ficin and subsequently reduced by β mercaptoethanol.The conjugation between Fab′ fragment and pingyangmycin (PYM),an antitumor antibiotic,was mediated by dextran T 40.Immunoreactivity of Fab′ PYM conjugates with cancer cells was determined by ELISA,and the cytotoxicity of those conjugates to cancer cells was determined by clonogenic assay.Antitumor effects of the Fab′ PYM conjugates were evaluated by subcutaneously transplanted tumors in mice. Results.The molecular weight of Fab′ fragment was approximately 53 kD,while the average molecular weight of Fab′ PYM conjugate was 170 kD.The Fab′ PYM conjugates showed immunoreactivity with antigen relevant cancer cells and selective cytotoxicity against target cells.Administered intravenously,Fab′ PYM conjugates were more effective against the growth of tumors in mice than free PYM and PYM conjugated with intact mAb. Conclusion.Fab′ PYM conjugate may be capable of targeting cancer cells and effectively inhibiting tumor growth,suggesting its therapeutic potential in cancer treatment.

Phase I Dose Escalation Study with the Lewis Y Carbohydrate Specific Humanized Antibody IGN311

Purpose: Investigation of safety, tolerability, pharmacokinetics, and anti-tumor activity of the Lewis Y-specific, fully humanized monoclonal antibody (mAb) IGN311 in patients with Lewis Y positive tumors in a Phase I clinical trial. Experimental Design: Twelve patients (pts) were enrolled in an open-label, uncontrolled, dose escalating Phase I study. Three pts received 50 mg, three pts 100 mg and six pts 200 mg IGN311 by i.v. infusion on days 1 and 15. Blood samples were taken immediately before infusion, and 0.5, 4, 8, 24 hours post infusion, as well as on days 3, 5 and 8 after the first and second infusion, respectively, and day 29. A final visit was scheduled for day 43. Results: No drug related adverse events were observed in the 50 mg and 100 mg dose groups. Three out of six patients in the 200 mg dose group showed drug related adverse reactions with nausea, vomiting and hypotension in one patient (NCI CTC grade 3) being the dose limiting toxicities. t1/2 of IGN311 was ~20 days after second infusion of IGN311. Sera of patients receiving IGN311 were capable of lysing Lewis Y positive tumor cells in vitro by both, complement-dependent cytotoxicity (CDC) and antibody-dependent cellular cytotoxicity (ADCC). Circulating tumor cells found in the peripheral blood in two out of twelve pts prior to treatment were reduced after treatment to below the quantification limit of the detection method. None of the patients showed an increase in the number of disseminated tumor cells during treatment period. Conclusions: The good safety and PK profile, the biological activity regarding CDC and ADCC mediated tumor cell lysis, and the elimination of circulating tumor cells warrant further clinical investigation of IGN311.

Mimotope peptide modified pompon mum-like magnetic microparticles for precise recognition,capture and biotransformation analysis of rituximab in biological fluids

Due to low immobilized ligand density,limited binding capacity,and severe interference from serum proteins,developing ideal peptide-based biomaterials for precise recognition and in vivo analysis of biopharmaceuticals remains a huge challenge.In this study,mimotope peptide modified pompon mum-like biomimetic magnetic microparticles(MMPs,3.8μm)that mimic the specific functionalities of CD20 on malignant B cells were developed for the first time.Benefit from the numerous ligand binding sites(Ni^(2+))on the pompon mum-like MMPs,these novel materials achieved≥10 times higher peptide ligand densities(>2300 mg/g)and antibody binding capacities(1380 mg/g)compared to previous reported biomaterials.Leveraging the high specificity of the mimotope peptide,rituximab can be precisely recognized and enriched from cell culture media or serum samples.We also established an LC-MS/MS method using the MMPs for tracking rituximab biotransformation in patient serum.Intriguingly,deamidation of Asn55 and Asn33,as well as oxidation of Met81 and Met34 were observed at the key complementarity determining regions of rituximab,which could potentially influence antibody function and require careful monitoring.Overall,these versatile biomimetic MMPs demonstrate superior recognition and enrichment capabilities for target antibodies,offering interesting possibilities for biotransformation analysis of biopharmaceuticals in patient serum.

Therapeutic ACPA inhibits NET formation: a potential therapy for neutrophil-mediated inflammatory diseases

Excessive release of neutrophil extracellular traps(NETs)is associated with disease severity and contributes to tissue injury,followed by severe organ damage.Pharmacological or genetic inhibition of NET release reduces pathology in multiple inflammatory disease models,indicating that NETs are potential therapeutic targets.Here,we demonstrate using a preclinical basket approach that our therapeutic anti-citrullinated protein antibody(tACPA)has broad therapeutic potential.Treatment with tACPA prevents disease symptoms in various mouse models with plausible NET-mediated pathology,including inflammatory arthritis(IA),pulmonary fibrosis,inflammatory bowel disease and sepsis.We show that citrulline residues in the N-termini of histones 2A and 4 are specific targets for therapeutic intervention,whereas antibodies against other N-terminal post-translational histone modifications have no therapeutic effects.Because citrullinated histones are generated during NET release,we investigated the ability of tACPA to inhibit NET formation.tACPA suppressed NET release from human neutrophils triggered with physiologically relevant human disease-related stimuli.Moreover,tACPA diminished NET release and potentially initiated NET uptake by macrophages in vivo,which was associated with reduced tissue damage in the joints of a chronic arthritis mouse model of IA.To our knowledge,we are the first to describe an antibody with NET-inhibiting properties and thereby propose tACPA as a drug candidate for NET-mediated inflammatory diseases,as it eliminates the noxious triggers that lead to continued inflammation and tissue damage in a multidimensional manner.

A non-human primate derived anti-P-selectin glycoprotein ligand-1 antibody curtails acute pancreatitis by alleviating the inflammatory responses

Acute pancreatitis(AP)is a devastating disease characterized by an inflammatory disorder of the pancreas.P-selectin glycoprotein ligand-1(PSGL-1)plays a crucial role in the initial steps of the adhesive at process to inflammatory sites,blockade of PSGL-1 might confer potent anti-inflammatory effects.In this study,we generated two non-human primate derived monoclonal antibodies capable of efficiently targeting human PSGL-1,RH001-6 and RH001-22,which were screened from immunized rhesus macaques.We found that RH001-6,can effectively block the binding of P-selectin to PSGL-1,and abolish the adhesion of leukocytes to endothelial cells in vitro.In vivo,we verified that RH001-6 relieved inflammatory responses and pancreatic injury in both caerulein and L-arginine induced AP models.We also evaluated the safety profile after RH001-6 treatment in mice,and verified that RH001-6 did not cause any significant pathological damages in vivo.Taken together,we developed a novel non-human primate derived PSGL-1 blocking antibody with high-specificity,named RH001-6,which can interrupt the binding of PSGL-1 and P-selectin and attenuate inflammatory responses during AP.Therefore,RH001-6 is highly potential to be further developed into therapeutics against acute inflammatory diseases,such as AP.

Development of an antibody that neutralizes soluble IgE and eliminates IgE expressing B cells

Immunoglobulin E （IgE） plays a key role in allergic asthma and is a clinically validated target for monoclonal antibodies. Therapeutic anti-lgE antibodies block the interaction between IgE and the Fc epsilon （Fcε） receptor, which eliminates or minimizes the allergic phenotype but does not typically curtail the ongoing production of IgE by B cells. We generated high-affinity anti-lgE antibodies （MEDI4212） that have the potential to both neutralize soluble IgE and eliminate IgE-expressing B-cells through antibody-dependent cell-mediated cytotoxicity. MEDI4212 variants were generated that contain mutations in the Fc region of the antibody or alterations in fucosylation in order to enhance the antibody＇s affinity for FcyRIIla. All MEDI4212 variants bound to human IgE with affinities comparable to the wild-type （WT） antibody. Each variant was shown to inhibit the interaction between IgE and FcεRI, which translated into potent inhibition of FcyRI-mediated function responses. Importantly, all variants bound similarly to IgE at the surface of membrane IgE expressing cells. However, MEDI4212 variants demonstrated enhanced affinity for FcyRIIla including the polymorphic variants at position 158. The improvement in FcyRIIla binding led to increased effector function in cell based assays using both engineered cell lines and class switched human IgE B cells. Through its superior suppression of IgE, we anticipate that effector function enhanced MEDI4212 may be able to neutralize high levels of soluble IgE and provide increased long-term benefit by eliminating the IgE expressing B cells before they differentiate and become IgE secreting plasma cells.

nvolvement of collagen-binding heat shock protein 47 in scleroderma-associated fibrosis

Uncontrolled fibrosis of skin and internal organs is the main characteristic of scleroderma, and collagen is a major extracellular matrix protein that deposits in the fibrotic organs. As the chaperone of collagen, heat shock protein 47 （HSP47） is closely related with the development of fbrosis. To explore the potential func- tion of HSP47 in the pathogenesis of scleroderma, the clinical, in vivo and in vitro studies were performed. In clinical, the increased mRNA level of HSP47 was observed in the skin fibroblasts and PBMC from scle- roderma patients, and the enhanced protein level of HSP47 was also detected in the skin biopsy and plasma of the above patients. Unexpectedly, the enhanced levels of HSP47 were positively correlated with the presence of anti-centromere antibody in scleroderma patients. Moreover, a high expression of HSP47 was found in the skin lesion of BLM-induced scleroderma mouse model. Further in vitro studies demonstrated that HSP47 knockdown could block the intracellular and extracellular collagen over-productions induced by exogenous TGF-13. Therefore, the results in this study provide direct evidence that HSP47 is involved in the pathogenesis of scleroderma. The high expression of HSP47 can be detected in the circulatory system of scleroderma patients, indicating that HSP47 maybecome a pathological marker to assess the progres- sion of scleroderma, and also explain the systemic fibrosis of scleroderma. Meanwhile, collagen over-ex- pression is blocked by HSP47 knockdown, suggesting the possibility that HSP47 can be a potential therapeutic target for scleroderma.

Streamlined human antibody generation and optimization by exploiting designed immunoglobulin loci in a B cell line

Monoclonal antibodies(mAbs)are widely utilized as therapeutic drugs for various diseases,such as cancer,autoimmune diseases,and infectious diseases.Using the avian-derived B cell line DT40,we previously developed an antibody display technology,namely,the ADLib system,which rapidly generates antigen-specific mAbs.Here,we report the development of a human version of the ADLib system and showcase the streamlined generation and optimization of functional human mAbs.Tailored libraries were first constructed by replacing endogenous immunoglobulin genes with designed human counterparts.From these libraries,clones producing full-length human IgGs against distinct antigens can be isolated,as exemplified by the selection of antagonistic mAbs.Taking advantage of avian biology,effective affinity maturation was achieved in a straightforward manner by seamless diversification of the parental clones into secondary libraries followed by single-cell sorting,quickly affording mAbs with improved affinities and functionalities.Collectively,we demonstrate that the human ADLib system could serve as an integrative platform with unique diversity for rapid de novo generation and optimization of therapeutic or diagnostic antibody leads.Furthermore,our results suggest that libraries can be constructed by introducing exogenous genes into DT40 cells,indicating that the ADLib system has the potential to be applied for the rapid and effective directed evolution and optimization of proteins in various fields beyond biomedicine.