抗体偶联药物的技术现状和展望

抗体偶联药物（antibody drug conjugate,ADC）通常由抗体通过链接体与毒素小分子偶联而成,同时具备抗体的高靶向性和小分子药物的高活性,使之作为一种新兴的靶向治疗手段,在肿瘤治疗领域展现出了优秀的疗效和潜力,成为药物研发领域的新热点。目前全球已有14款ADC药物获批上市,处于临床研究阶段的ADC候选药物分子超过140个。为了进一步提高ADC药物的安全性和有效性,近年来涌现出了各种新颖的技术。本文对ADC药物分子的关键元素,包括抗体、链接体、毒素小分子以及偶联技术等方面的最新研究进展进行总结,并讨论其优缺点。期望这些讨论能够帮助增加对ADC药物研究和开发更加系统的理解,为研发出更加高效和安全的ADC药物带来一些思考。     

Native mass spectrometry and ion mobility characterization of trastuzumab emtansine,a lysine-linked antibody drug conjugate

Antibody–drug conjugates (ADCs) are biochemotherapeutics consisting of a cytotoxic chemical drug linked covalently to a monoclonal antibody. Two main classes of ADCs, namely cysteine and lysine conjugates, are currently available on the market or involved in clinical trials. The complex structure and heterogeneity of ADCs makes their biophysical characterization challenging. For cysteine conjugates, hydrophobic interaction chromatography is the gold standard technique for studying drug distribution, the naked antibody content, and the average drug to antibody ratio (DAR). For lysine ADC conjugates on the other hand, which are not amenable to hydrophobic interaction chromatography because of their higher heterogeneity, denaturing mass spectrometry (MS) and UV/Vis spectroscopy are the most powerful approaches. We report here the use of native MS and ion mobility (IM-MS) for the characterization of trastuzumab emtansine (T-DM1, Kadcyla®). This lysine conjugate is currently being considered for the treatment of human epidermal growth factor receptor 2 (HER2)-positive breast cancer, and combines the anti-HER2 antibody trastuzumab (Herceptin®), with the cytotoxic microtubule-inhibiting maytansine derivative, DM1. We show that native MS combined with high-resolution measurements and/or charge reduction is beneficial in terms of the accurate values it provides of the average DAR and the drug load profiles. The use of spectral deconvolution is discussed in detail. We report furthermore the use of native IM-MS to directly determine DAR distribution profiles and average DAR values, as well as a molecular modeling investigation of positional isomers in T-DM1.     

World Bispecific Antibody Summit,September 27–28, 2011, Boston,MA

With more than 30 therapeutic monoclonal antibodies (mAbs) approved and annual global sales of the products at ∼$50 billion in 2010, these products have proven to be successful in many ways. Nevertheless, there is room for improvement in performance, and substantial unmet medical needs remain. As a consequence, numerous organizations are devoting resources to engineering novel mAbs such as bispecific antibodies that have increased functionality compared with unmodified IgG molecules. The World Bispecific Antibody Summit, organized by Hanson Wade, drew over 100 participants to Boston to discuss engineering novel bispecific antibodies, generating lead candidates and clinical study and commercialization of the molecules. Approaches such as the trifunctional antibody (TRION), dual variable domain-Ig (Abbott), two-in-one (Genentech), dual affinity retargeting (MacroGenics), kappa-lambda body (NovImmune), bispecific T-cell engager (Micromet) and chemical generation (CovX/Pfizer) were discussed in detail. In addition, posters describing bispecific Affibody^® molecules for targeting of EGFR and HER2 (Affibody), T-cell receptor based bi-specifics that target HLA-peptides (Immunocore), a novel mAb-Fv bispecific antibody format utilizing Fc region (Xencore), generation of a tetravalent bispecific antibody against IL4 and IL13 for the treatment of idiopathic pulmonary fibrosis (Sanofi), Combining Affibody^® molecules and the AlbumodTM technology to create long acting multispecific protein therapeutics (Royal Institute of Technology, Affibody) and COVA301 as a highly potent bispecific inhibitor of IL-17A and TNFα (Covagen) were presented.Key words: bispecific antibodies, antibody engineering, therapeutic antibodies     

Marketing approval of mogamulizumab: A triumph for glyco-engineering

Therapeutic properties of antibodies strongly depend on the composition of their glycans. Most of the currently approved antibodies are produced in mammalian cell lines, which yield mixtures of different glycoforms that are close to those of humans, but not fully identical. Glyco-engineering is being developed as a method to control the composition of carbohydrates and to enhance the pharmacological properties of mAbs. The recent approval in Japan of mogamulizumab (POTELIGEO^®), the first glyco-engineered antibody to reach the market, is a landmark in the field of therapeutic antibodies. Mogamulizumab is a humanized mAb derived from Kyowa Hakko Kirin’s POTELLIGENT^® technology, which produces antibodies with enhanced antibody-dependent cell-mediated cytotoxicity (ADCC) activity. The approval was granted April 30, 2012 by the Japanese Ministry of Health, Labour and Welfare for patients with relapsed or refractory CCR4-positive adult T-cell leukemia-lymphoma.     

Microscale screening of antibody libraries as maytansinoid antibody-drug conjugates

Antibody-drug conjugates (ADCs) are of great interest as targeted cancer therapeutics. Preparation of ADCs for early stage screening is constrained by purification and biochemical analysis techniques that necessitate burdensome quantities of antibody. Here we describe a method, developed for the maytansinoid class of ADCs, enabling parallel conjugation of antibodies in 96-well format. The method utilizes ～100 µg of antibody per well and requires <5 µg of ADC for characterization. We demonstrate the capabilities of this system using model antibodies. We also provide multiple examples applying this method to early-stage screening of maytansinoid ADCs. The method can greatly increase the throughput with which candidate ADCs can be screened in cell-based assays, and may be more generally applicable to high-throughput preparation and screening of different types of protein conjugates.     

Methods for site-specific drug conjugation to antibodies

Antibody drug conjugates (ADCs) are an emerging class of targeted therapeutics with the potential to improve therapeutic index over traditional chemotherapy. Drugs and linkers have been the current focus of ADC development, in addition to antibody and target selection. Recently, however, the importance of conjugate homogeneity has been realized. The current methods for drug attachment lead to a heterogeneous mixture, and some populations of that mixture have poor in vivo performance. New methods for site-specific drug attachment lead to more homogeneous conjugates and allow control of the site of drug attachment. These subtle improvements can have profound effects on in vivo efficacy and therapeutic index. This review examines current methods for site-specific drug conjugation to antibodies, and compares in vivo results with their non-specifically conjugated counterparts. The apparent improvement in pharmacokinetics and the reduced off target toxicity warrant further development of this site-specific modification approach for future ADC development.     

Site-specific antibody-drug conjugation through an engineered glycotransferase and a chemically reactive sugar

Conjugation of small molecule drugs to specific sites on the antibody molecule has been increasingly used for the generation of relatively homogenous preparations of antibody-drug conjugates (ADCs) with physicochemical properties similar or identical to those of the naked antibody. Previously a method for conjugation of small molecules to glycoproteins through existing glycans by using an engineered glycotransferase and a chemically reactive sugar as a handle was developed. Here, for the first time, we report the use of this method with some modifications to generate an ADC from a monoclonal antibody, m860, which we identified from a human naïve phage display Fab library by panning against the extracellular domain of human HER2. M860 bound to cell surface-associated HER2 with affinity comparable to that of Trastuzumab (Herceptin®), but to a different epitope. The m860ADC was generated by enzymatically adding a reactive keto-galactose to m860 using an engineered glycotransferase and conjugating the reactive m860 to aminooxy auristatin F. It exhibited potent and specific cell-killing activity against HER2 positive cancer cells, including trastuzumab-resistant breast cancer cells. This unique ADC may have utility as a potential therapeutic for HER2 positive cancers alone or in combination with other drugs. Our results also validate the keto-galactose/engineered glycotransferase method for generation of functional ADCs, which could potentially also be used for preparation of ADCs targeting other disease markers.     

Methods for site-specific drug conjugation to antibodies

Antibody drug conjugates (ADCs) are an emerging class of targeted therapeutics with the potential to improve therapeutic index over traditional chemotherapy. Drugs and linkers have been the current focus of ADC development, in addition to antibody and target selection. Recently, however, the importance of conjugate homogeneity has been realized. The current methods for drug attachment lead to a heterogeneous mixture, and some populations of that mixture have poor in vivo performance. New methods for site-specific drug attachment lead to more homogeneous conjugates and allow control of the site of drug attachment. These subtle improvements can have profound effects on in vivo efficacy and therapeutic index. This review examines current methods for site-specific drug conjugation to antibodies, and compares in vivo results with their non-specifically conjugated counterparts. The apparent improvement in pharmacokinetics and the reduced off target toxicity warrant further development of this site-specific modification approach for future ADC development.     

Antibody-drug conjugates: recent advances in conjugation and linker chemistries

The antibody-drug conjugate (ADC), a humanized or human monoclonal antibody conjugated with highly cytotoxic small molecules (payloads) through chemical linkers, is a novel therapeutic format and has great potential to make a paradigm shift in cancer chemotherapy. Thisnewantibody-based molecular platform enables selective delivery of a potent cytotoxic payload to target cancer cells, resulting in improved efficacy, reduced systemic toxicity, and preferable pharmacokinetics (PK)/ pharmacodynamics (PD) and biodistribution compared to traditional chemotherapy. Boosted by the successes of FDA-approved Adcetris® and Kadcyla®, this drug class has been rapidly growing along with about 60 ADCs currently in clinical trials. In this article, we briefly review molecular aspects of each component (the antibody, payload, and linker) of ADCs, and then mainly discuss traditional and new technologies of the conjugation and linker chemistries for successful construction of clinically effective ADCs. Current efforts in the conjugation and linker chemistries will provide greater insights into molecular design and strategies for clinically effective ADCs from medicinal chemistry and pharmacology standpoints. The development of site-specific conjugation methodologies for constructing homogeneousADCs is an especially promising path to improving ADC design, which will open the way for novel cancer therapeutics.     

The birth pangs of monoclonal antibody therapeutics: The failure and legacy of Centoxin

This paper examines the development and termination of nebacumab (Centoxin®), a human IgM monoclonal antibody (mAb) drug frequently cited as one of the notable failures of the early biopharmaceutical industry. The non-approval of Centoxin in the United States in 1992 generated major concerns at the time about the future viability of any mAb therapeutics. For Centocor, the biotechnology company that developed Centoxin, the drug posed formidable challenges in terms of safety, clinical efficacy, patient selection, the overall economic costs of health care, as well as financial backing. Indeed, Centocor''s development of the drug brought it to the brink of bankruptcy. This article shows how many of the experiences learned with Centoxin paved the way for the current successes in therapeutic mAb development.     

In Vitro and In Vivo Evaluation of Cysteine and Site Specific Conjugated Herceptin Antibody-Drug Conjugates

Antibody drug conjugates (ADCs) are monoclonal antibodies designed to deliver a cytotoxic drug selectively to antigen expressing cells. Several components of an ADC including the selection of the antibody, the linker, the cytotoxic drug payload and the site of attachment used to attach the drug to the antibody are critical to the activity and development of the ADC.The cytotoxic drugs or payloads used to make ADCs are typically conjugated to the antibody through cysteine or lysine residues. This results in ADCs that have a heterogeneous number of drugs per antibody. The number of drugs per antibody commonly referred to as the drug to antibody ratio (DAR), can vary between 0 and 8 drugs for a IgG₁ antibody. Antibodies with 0 drugs are ineffective and compete with the ADC for binding to the antigen expressing cells. Antibodies with 8 drugs per antibody have reduced in vivo stability, which may contribute to non target related toxicities.In these studies we incorporated a non-natural amino acid, para acetyl phenylalanine, at two unique sites within an antibody against Her2/neu. We covalently attached a cytotoxic drug to these sites to form an ADC which contains two drugs per antibody.We report the results from the first direct preclinical comparison of a site specific non-natural amino acid anti-Her2 ADC and a cysteine conjugated anti-Her2 ADC. We report that the site specific non-natural amino acid anti-Her2 ADCs have superior in vitro serum stability and preclinical toxicology profile in rats as compared to the cysteine conjugated anti-Her2 ADCs. We also demonstrate that the site specific non-natural amino acid anti-Her2 ADCs maintain their in vitro potency and in vivo efficacy against Her2 expressing human tumor cell lines. Our data suggests that site specific non-natural amino acid ADCs may have a superior therapeutic window than cysteine conjugated ADCs.     

6th Annual European Antibody Congress 2010: November 29–December 1, 2010, Geneva,Switzerland

The 6^th European Antibody Congress (EAC), organized by Terrapinn Ltd., was held in Geneva, Switzerland, which was also the location of the 4^th and 5^th EAC.^1,2 As was the case in 2008 and 2009, the EAC was again the largest antibody congress held in Europe, drawing nearly 250 delegates in 2010. Numerous pharmaceutical and biopharmaceutical companies active in the field of therapeutic antibody development were represented, as were start-up and academic organizations and representatives from the US Food and Drug Administration (FDA). The global trends in antibody research and development were discussed, including success stories of recent marketing authorizations of golimumab (Simponi^®) and canakinumab (Ilaris^®) by Johnson & Johnson and Novartis, respectively, updates on antibodies in late clinical development (obinutuzumab/GA101, farletuzumab/MORAb-003 and itolizumab/T1 h, by Glycart/Roche, Morphotek and Biocon, respectively) and success rates for this fast-expanding class of therapeutics (Tufts Center for the Study of Drug Development). Case studies covering clinical progress of girentuximab (Wilex), evaluation of panobacumab (Kenta Biotech), characterization of therapeutic antibody candidates by protein microarrays (Protagen), antibody-drug conjugates (sanofi-aventis, ImmunoGen, Seattle Genetics, Wyeth/Pfizer), radio-immunoconjugates (Bayer Schering Pharma, Université de Nantes) and new scaffolds (Ablynx, AdAlta, Domantis/GlaxoSmithKline, Fresenius, Molecular Partners, Pieris, Scil Proteins, Pfizer, University of Zurich) were presented. Major antibody structural improvements were showcased, including the latest selection engineering of the best isotypes (Abbott, Pfizer, Pierre Fabre), hinge domain (Pierre Fabre), dual antibodies (Abbott), IgG-like bispecific antibodies (Biogen Idec), antibody epitope mapping case studies (Eli Lilly), insights in FcγRII receptor (University of Cambridge), as well as novel tools for antibody fragmentation (Genovis). Improvements of antibody druggability (Abbott, Bayer, Pierre Fabre, Merrimack, Pfizer), enhancing IgG pharmacokinetics (Abbott, Chugai), progress in manufacturing (Genmab, Icosagen Cell Factory, Lonza, Pierre Fabre) and the development of biosimilar antibodies (Biocon, Sandoz, Triskel) were also discussed. Last but not least, identification of monoclonal antibodies (mAbs) against new therapeutic targets (Genentech, Genmab, Imclone/Lilly, Vaccinex) including Notch, cMet, TGFβRII, SEMA4D, novel development in immunotherapy and prophylaxis against influenza (Crucell), anti-tumor activity of immunostimulatory antibodies (MedImmune/Astra Zeneca) and translations to clinical studies including immunogenicity issues (Amgen, Novartis, University of Debrecen) were presented.Key words: therapeutic antibodies, antibody-drug conjugates, protein scaffolds, biosimilars, bioproduction

• MAbs. 2011 Mar-Apr; 3(2): 111–132.
»
• Day 1: November 29, 2010

2011 Mar-Apr; 3(2): 111–132. Published online 2011 Mar 1. doi: 10.4161/mabs.3.2.14788

Day 1: November 29, 2010

Alain Beck Copyright and License information DisclaimerCopyright notice The EAC chairman, Alain Beck (Centre d''Immunologie Pierre Fabre), opened the meeting with a presentation on strategies and challenges for the next generation of therapeutic antibodies.³ By analyzing the regulatory approvals of IgG-based biotherapeutic agents in the past ten years, we can gain insights into the successful strategies used by pharmaceutical companies so far to bring innovative drugs to the market. Strategies to optimize the structure of IgG antibodies and to design related or new structures with additional functions were presented. A detailed knowledge of antibody structure and activity now allows researchers to engineer primary antibodies on a more rational basis. Most approved antibodies are chimeric, humanized or human IgGs with similar constant domains. Numerous studies looking at the structure-function relationships of these antibodies have been published in the past five years with the aim of identifying antibody microvariants⁴ and investigating the influence of these variants on antigen binding, stability, pharmacokinetics (PK) and pharmacodynamics (PD). This knowledge is now being used to increase homogeneity and mitigate the chemistry, manufacture and control (CMC) liabilities of preclinical antibody candidates by genetic engineering. The removal by mutation of instability or aggregation hot spots in the antibody complementarity-determining regions (CDRs), and the use of hinge-stabilized or aglycosylated IgG4, are just a few examples of antibodies with improved pharmacological properties, including decreased heterogeneity, that are currently in development.Dr. Beck explained that the variable fragment (Fv) of an antibody is responsible for interactions with antigens and dictates essential properties such as binding affinity and target specificity. The origin of the Fv in therapeutic antibodies can be diverse, e.g., hybridomas, human antibody libraries, rodents with a human antibody repertoire or primatized or humanized antibodies from various species. Affinity maturation allows the binding affinity of the Fv to be improved or target selectivity to be modulated. The constant fragment (Fc) of an antibody is responsible for interactions with immune cells, and the associated properties of the Fc can also be modulated by engineering at several levels:⁵ altering the glycosylation status to regulate anti- and pro-inflammatory properties, modulating antibody-dependent cellular cytotoxicity (ADCC) by site-directed mutagenesis to alter binding to Fc receptors, increasing the serum half-life by Fc engineering to increase binding to the neonatal Fc receptor (FcRn), thereby preventing IgG degradation, and increasing complement activation by isotype chimerism. Additional functions can be endowed on antibodies by conjugation to other drugs. To date, the clinical success of antibody-drug conjugates (ADCs) has been limited. Nevertheless, promising new ADCs that include linkers with optimized properties (e.g., hydrolysable in the cytoplasm, resistant or susceptible to proteases or resistant to multi-drug resistance efflux pumps) and highly cytotoxic drugs are being studied in advanced clinical trials (e.g., trastuzumab emtansine, inotuzumab ozogamicin and brentuximab vedotin).⁶ IgGs have also been engineered to contain unique drug conjugation positions to obtain uniform and more homogeneous drug conjugates, such as ThioMab-drug conjugates, which have a uniform stoichiometry of approximately two coupled drugs per antibody molecule. Collectively, these advances should open new therapeutic avenues to deliver highly cytotoxic drugs with increased tolerability.     

Effects of antibody,drug and linker on the preclinical and clinical toxicities of antibody-drug conjugates

Antibody-drug conjugates (ADCs) represent a new class of cancer therapeutics. Their design involves a tumor-specific antibody, a linker and a cytotoxic payload. They were designed to allow specific targeting of highly potent cytotoxic agents to tumor cells whilst sparing normal cells. Frequent toxicities that may be driven by any of the components of an ADC have been reported. There are currently more than 50 ADCs in active clinical development, and a further ～20 that have been discontinued. For this review, the reported toxicities of ADCs were analysed, and the mechanisms for their effects are explored in detail. Methods to reduce toxicities, including dosing strategies and drug design, are discussed. The toxicities reported for active and discontinued drugs are important to drive the rational design and improve the therapeutic index of ADCs of the future.     

Structural and functional characterization of the trifunctional antibody catumaxomab

The Triomab^® family of trifunctional, bispecific antibodies that maintain an IgG-like shape are novel tumor targeting agents. These chimeras consist of two half antibodies, each with one light and one heavy chain, that originate from parental mouse IgG2a and rat IgG2b isotypes. This combination allows cost-effective biopharmaceutical manufacturing at an industrial scale since this specific mouse/rat isotype combination favors matching of corresponding antibody halves during production by means of quadroma technology. Whereas every Triomab^® family member is composed of an anti-CD3 rat IgG2b half antibody for Tcell recognition, the antigen binding site presented by the mouse IgG2a isotype is exchangeable. Several Triomab^® antibodies have been generated that bind to tumor-associated antigens, e.g., EpCAM (catumaxomab), HER2/neu (ertumaxomab), CD20 (FBTA05), gangliosides GD2/GD3 (Ektomun^®), on appropriate tumor target cells associated with carcinomas, lymphomas or melanomas. Catumaxomab (Removab^®) was launched in Europe for treatment of malignant ascites in April 2009. Here, we report the structural and functional characterization of this product. Mass spectrometry revealed an intact mass of 150511 Dalton (Da) and 23717 Da, 24716 Da, 51957 Da and 52019 Da of the reduced and alkylated rat light chain, mouse light chain, rat heavy chain, mouse heavy chain chains, respectively. The observed masses were in agreement with the expected masses based on the amino acid sequence obtained from cDNA sequencing. The glycosylation profile was similar to other human IgG consisting of biantennary oligosaccharides with different numbers of terminal galactose. CD spectroscopy showed mainly β-sheets secondary structure that is typical for IgG antibodies. Binding measurement revealed the unique trifunctional features of catumaxomab. Other analytical tools were used to evaluate characteristics of catumaxomab preparations, including the presence of isoforms and aggregates.     

World Antibody Drug Conjugate Summit Europe: February 21–23, 2011; Frankfurt,Germany

The World Antibody Drug Conjugate Summit Europe, organized by Biorbis/Hanson Wade was held in Frankfurt, Germany February 21–23, 2011. Antibody drug conjugates (ADCs), also called immunoconjugates, are becoming an increasingly important class of therapeutics as demonstrated by the attendance of nearly 100 delegates at this highly focused meeting. Updates on three ADCs that are in late-stage clinical development, trastuzumab emtansine (T-DM1), brentuximab vedotin (SGN-35) and inotuzumab ozogamicin (CMC-544), were presented by speakers from ImmunoGen, Genentech, Roche, Seattle Genetics and Pfizer. These ADCs have shown encouraging therapeutic effects against solid tumors (T-DM1) and hematological malignancies (SGN-35, CMC-544). The key feature of the new generation of ADCs is the effective combination of the cytotoxicity of natural or synthetic highly potent antineoplastic agents, tumor selective monoclonal antibodies and blood-stable optimized linkers. Early clinical data for ADCs were showcased by Progenics Pharmaceuticals (PSMA ADC), Celldex (CDX-011) and Biotest (BT-062). Takeda, MedImmune and sanofi-aventis outlined their strategies for process development and analytical characterization. In addition, presentations on duocarmycin based-ADCs, α emitting immunoconjugates and antibody-conjugated nanoparticles were given by representatives from Syntarga, Algeta and the University of Stuttgart, respectively.Key words: antibody drug conjugates, immunoconjugates, trastuzumab emtansine, brentuximab vedotin, inotuzumab ozogamicin, oncology, cancer     

Fourth World Antibody-Drug Conjugate Summit: February 29–March 1, 2012, Frankfurt,Germany

The 4th World Antibody Drug Conjugate (WADC) Summit, organized by Hanson Wade was held on February 29‑March 1, 2012 in Frankfurt, Germany, which was also the location for the Antibody Drug Conjugate Summit Europe held in February 2011. During the one year between these meetings, antibody drug conjugates (ADCs) have confirmed their technological maturity and their clinical efficacy in oncology. Brentuximab vedotin (ADCETRIS^TM) gained approval by the US Food and Drug Administration in August 2011 and trastuzumab emtansine (T-DM1) confirmed impressive clinical efficacy responses in a large cohort of breast cancer patients. During the 4th WADC meeting, antibody-maytansinoid conjugates were showcased by representatives of ImmunoGen (T-DM1, SAR3419, lorvotuzumab mertansine/IMGN801, IMGN529 and IMG853) and Biotest (BT-062). Data on antibody-auristatin conjugates were presented by scientists and clinicians from Seattle Genetics and Takeda (brentuximab vedotin), Pfizer (5T4-MMAF), Agensys/Astella (AGS-16M8F), Progenics (PSMA-ADC) and Genmab (anti-TF ADCs). Alternative payloads such as calicheamicins and duocarmycin used for preparation of ADCs were discussed by Pfizer and Synthon representatives, respectively. In addition, emerging technologies, including site-directed conjugation (Ambrx), a protein toxin as payload (Viventia), hapten-binding bispecific antibodies (Roche), and use of light activated drugs (Photobiotics), were also presented. Last but not least, progresses in solving Chemistry Manufacturing and Control, and pharmacokinetic issues were addressed by scientists from Genentech, Pfizer, Novartis and Pierre Fabre.     

Physicochemical characterization of Remsima?

Remsima® (infliximab) was recently approved as the world''s first biosimilar monoclonal antibody (mAb) in both the European Union and Korea. To achieve this, extensive physicochemical characterization of Remsima® in relation to Remicade® was conducted in order to demonstrate the highly similar properties between the two molecules. A multitude of state-of-the-art analyses revealed that Remsima® has identical primary as well as indistinguishable higher order structures compared with the original product. Monomer and aggregate contents of Remsima® were also found to be comparable with those of Remicade®. In terms of charge isoforms, although Remsima® was observed to contain slightly less basic variants than the original antibody, the difference was shown to be largely due to the presence of C-terminal lysine. On the other hand, this lysine was found to be rapidly clipped inside serum in vitro and in vivo, suggesting it has no effect on the biological potency or safety of the drug. Analysis of the glycan contents of the antibodies showed comparable glycan types and distributions. Recent results of clinical studies have further confirmed that the two antibody products are highly similar to each other. Based on this research as well as previous clinical and non-clinical comparability studies, Remsima® can be considered as a highly similar molecule to Remicade® in terms of physicochemical properties, efficacy, and safety for its final approval as a biosimilar product to Remicade®.     

The discovery and development of brentuximab vedotin for use in relapsed Hodgkin lymphoma and systemic anaplastic large cell lymphoma

Progress has been made recently in developing antibody-drug conjugates (ADCs) that can selectively deliver cancer drugs to tumor cells. In principle, the idea is simple: by attaching drugs to tumor-seeking antibodies, target cells will be killed and nontarget cells will be spared. In practice, many parameters needed to be addressed to develop safe and effective ADCs, including the expression profiles of tumor versus normal tissues, the potency of the drug, the linker attaching the drug and placement of the drug on the antibody, and the pharmacokinetic and stability profiles of the resulting ADC. All these issues had been taken into account in developing brentuximab vedotin (Adcetris), an ADC that recently received accelerated approval by the US Food and Drug Administration for the treatment of relapsed Hodgkin lymphoma and systemic anaplastic large cell lymphoma (ALCL). Research is under way to extend the applications of brentuximab vedotin and to advance the field by developing other ADCs with new linker and conjugation strategies.     

Therapeutic antibodies directed at G protein-coupled receptors

G protein-coupled receptors (GPCRs) are one of the most important classes of targets for small molecule drug discovery, but many current GPCRs of interest are proving intractable to small molecule discovery and may be better approached with bio-therapeutics. GPCRs are implicated in a wide variety of diseases where antibody therapeutics are currently used. These include inflammatory diseases such as rheumatoid arthritis and Crohn disease, as well as metabolic disease and cancer. Raising antibodies to GPCRs has been difficult due to problems in obtaining suitable antigen because GPCRs are often expressed at low levels in cells and are very unstable when purified. A number of new developments in over-expressing receptors, as well as formulating stable pure protein, are contributing to the growing interest in targeting GPCRs with antibodies. This review discusses the opportunities for targeting GPCRs with antibodies using these approaches and describes the therapeutic antibodies that are currently in clinical development.