Antibodies to watch in 2010

Therapeutic Monoclonal Antibodies against Cancer: Present and Future

A series of monoclonal antibodies with therapeutic potential against cancer have been generated and developed. Ninety-one are currently used in the clinics, either alone or in combination with chemotherapeutic agents or other antibodies, including immune checkpoint antibodies. These advances helped to coin the term personalized medicine or precision medicine. However, it seems evident that in addition to the current work on the analysis of mechanisms to overcome drug resistance, the use of different classes of antibodies (IgA, IgE, or IgM) instead of IgG, the engineering of the Ig molecules to increase their half-life, the acquisition of additional effector functions, or the advantages associated with the use of agonistic antibodies, to allow a broad prospective usage of precision medicine successfully, a strategy change is required. Here, we discuss our view on how these strategic changes should be implemented and consider their pros and cons using therapeutic antibodies against cancer as a model. The same strategy can be applied to therapeutic antibodies against other diseases, such as infectious or autoimmune diseases.

Predicting Human Bioavailability of Subcutaneously Administered Fusion Proteins and Monoclonal Antibodies Using Human Intravenous Clearance or Antibody Isoelectric Point

There has been an increasing trend towards subcutaneous (SC) delivery of fusion proteins and monoclonal antibodies (mAbs) in recent years versus intravenous (IV) administration. The prediction of bioavailability is one of the major barriers in clinical translation of SC-administered therapeutic proteins due to a lack of reliable in vitro and preclinical in vivo predictive models. In this study, we explored the relationships between human SC bioavailability and physicochemical or pharmacokinetic properties of 19 Fc- or albumin-fusion proteins and 98 monoclonal antibodies. An inverse linear correlation was observed between human SC bioavailability and intravenous clearance (CL) or isoelectric point (pI). Multivariate regression models were developed using intravenous CL and pI of a training set (N = 59) as independent variables. The predictive models of mAbs were validated with an independent test set (N = 33). Two linear regression models resulted in 24 (73%) and 27 (82%) among 33 predictions within 0.8- to 1.2-fold deviations. Due to the small sample size of dataset, regression model validation was not conducted for fusion proteins. Overall, this study demonstrated that CL- and pI-based multivariate regression models could be used to predict human SC bioavailability of mAbs.

Antibodies to watch in 2023

In this 14th installment of the annual Antibodies to Watch article series, we discuss key events in commercial monoclonal antibody therapeutics development that occurred in 2022 and forecast events that might occur in 2023. As of mid-November, 12 antibody therapeutics had been granted first approvals in either the United States or European Union (tebentafusp (Kimmtrak), faricimab (Vabysmo), sutimlimab (Enjaymo), relatlimab (Opdualag), tixagevimab/cilgavimab (Evusheld), mosunetuzumab (Lunsumio), teclistamab (TECVAYLI), spesolimab (SPEVIGO), tremelimumab (Imjudo; combo with durvalumab), nirsevimab (Beyfortus), mirvetuximab soravtansine (ELAHERE™), and teplizumab (TZIELD)), including 4 bispecific antibodies and 1 ADC. Based on FDA action dates, several additional product candidates could be approved by the end of 2022. An additional seven were first approved in China or Japan in 2022, including two bispecific antibodies (cadonilimab and ozoralizumab). Globally, at least 24 investigational antibody therapeutics are undergoing review by regulatory agencies as of mid-November 2022. Our data show that, with antibodies for COVID-19 excluded, the late-stage commercial clinical pipeline grew by ~20% in the past year to include nearly 140 investigational antibody therapeutics that were designed using a wide variety of formats and engineering techniques. Of those in late-stage development, marketing application submissions for at least 23 may occur by the end of 2023, of which 5 are bispecific (odronextamab, erfonrilimab, linvoseltamab, zanidatamab, and talquetamab) and 2 are ADCs (datopotamab deruxtecan, and tusamitamab ravtansine).

Transmembrane stem cell factor protein therapeutics enhance revascularization in ischemia without mast cell activation

Stem cell factor (SCF) is a cytokine that regulates hematopoiesis and other biological processes. While clinical treatments using SCF would be highly beneficial, these have been limited by toxicity related to mast cell activation. Transmembrane SCF (tmSCF) has differential activity from soluble SCF and has not been explored as a therapeutic agent. We created novel therapeutics using tmSCF embedded in proteoliposomes or lipid nanodiscs. Mouse models of anaphylaxis and ischemia revealed the tmSCF-based therapies did not activate mast cells and improved the revascularization in the ischemic hind limb. Proteoliposomal tmSCF preferentially acted on endothelial cells to induce angiogenesis while tmSCF nanodiscs had greater activity in inducing stem cell mobilization and recruitment to the site of injury. The type of lipid nanocarrier used altered the relative cellular uptake pathways and signaling in a cell type dependent manner. Overall, we found that tmSCF-based therapies can provide therapeutic benefits without off target effects.

Antibodies to watch in 2022

In this 13th annual installment of the annual 'Antibodies to Watch' article series, we discuss key events in commercial antibody therapeutics development that occurred in 2021 and forecast events that might occur in 2022. Regulatory review of antibody therapeutics that target the SARS-CoV-2 coronavirus proceeded at an unprecedented pace in 2021, resulting in both emergency use authorizations and full approvals for sotrovimab, regdanvimab, REGEN-COV2, as well as others, in numerous countries. As of November 1, a total of 11 antibody therapeutics had been granted first approvals in either the United States or European Union in 2021 (evinacumab, dostarlimab loncastuximab tesirine, amivantamab, aducanumab, tralokinumab, anifrolumab, bimekizumab, tisotumab vedotin, regdanvimab, REGEN-COV2). The first global approvals of seven products, however, were granted elsewhere, including Japan (pabinafusp alfa), China (disitamab vedotin, penpulimab, zimberelimab), Australia (sotrovimab, REGEN-COV2), or the Republic of Korea (regdanvimab). Globally, at least 27 novel antibody therapeutics are undergoing review by regulatory agencies. First actions by the Food and Drug Administration on the biologics license applications for faricimab, sutimlimab, tebentafusp, relatlimab, sintilimab, ublituximab and tezepelumab are expected in the first quarter of 2022. Finally, our data show that, with antibodies for COVID-19 excluded, the late-stage commercial clinical pipeline of antibody therapeutics grew by over 30% in the past year. Of those in late-stage development, marketing applications for at least 22 may occur by the end of 2022.

Production, characterization, and epitope mapping of monoclonal antibodies of ribosomal protein S3 (rpS3)

Ribosomal protein S3 (rpS3), a member of 40S small ribosomal subunit, is a multifunctional protein with various extra-ribosomal functions including DNA repair endonuclease activity and is secreted from cancer cells. Therefore, antibodies with high specificity against rpS3 protein could be useful cancer biomarkers. In this study, polyclonal antibody (pAb) and monoclonal antibodies (mAbs) were raised against rpS3 protein and epitope mapping was performed for each antibody; the amino acid residues of rpS3 were scanned from amino acid 185 to 243 through peptide scanning to reveal the epitopes of each mAb. Results showed that pAb R2 has an epitope from amino acid 203 to 230, mAb M7 has an epitope from amino acid 213 to 221, and mAb M8 has an epitope from amino acid 197 to 219. Taken together, novel mAbs and pAb against rpS3 were raised and mapped against rpS3 with different specific epitopes.

HP-β-CD for the formulation of IgG and Ig-based biotherapeutics

The main challenge to develop HCF for IgG and Ig-based therapeutics is to achieve essential solubility, viscosity and stability of these molecules in order to maintain product quality and meet regulatory requirement during manufacturing, production, storage, shipment and administration processes. The commonly used and FDA approved excipients for IgG and Ig -based therapeutics may no longer fulfil the challenge of HCF development for these molecules to certain extent, especially for some complex Ig-based platforms. 2-Hydroxypropyl beta-cyclodextrin (HP-β-CD) is one of the promising excipients applied recently for HCF development of IgG and Ig-based therapeutics although it has been used for formulation of small synthesized chemical drugs for more than thirty years. This review describes essential aspects about application of HP-β-CD as excipient in pharmaceutical formulation, including physico-chemical properties of HP-β-CD, supply chain, regulatory, patent landscape, marketed drugs with HP-β-CD, analytics and analytical challenges, stability and control strategies, and safety concerns. It also provides an overview of different studies, and outcomes thereof, regarding formulation development for IgGs and Ig-based molecules in liquid and solid (lyophilized) dosage forms with HP-β-CD. The review specifically highlights the challenges for formulation manufacturing of IgG and Ig-based therapeutics with HP-β-CD and identifies areas for future work in pharmaceutical and formulation development.

Antibodies to watch in 2020

This 2020 installment of the annual 'Antibodies to Watch' series documents the antibody therapeutics approved in 2019 and in regulatory review in the United States or European Union, as well as those in late-stage clinical studies, as of November 2019*. At this time, a total of 5 novel antibody therapeutics (romosozumab, risankizumab, polatuzumab vedotin, brolucizumab, and crizanlizumab) had been granted a first approval in either the US or EU, and marketing applications for 13 novel antibody therapeutics (eptinezumab, teprotumumab, enfortumab vedotin, isatuximab, [fam-]trastuzumab deruxtecan, inebilizumab, leronlimab, sacituzumab govitecan, satralizumab, narsoplimab, tafasitamab, REGNEB3 and naxituximab) were undergoing review in these regions, which represent the major markets for antibody therapeutics. Also as of November 2019, 79 novel antibodies were undergoing evaluation in late-stage clinical studies. Of the 79 antibodies, 39 were undergoing evaluation in late-stage studies for non-cancer indications, with 2 of these (ublituximab, pamrevlumab) also in late-stage studies for cancer indications. Companies developing 7 (tanezumab, aducanumab, evinacumab, etrolizumab, sutimlimab, anifrolumab, and teplizumab) of the 39 drugs have indicated that they may submit a marketing application in either the US or EU in 2020. Of the 79 antibodies in late-stage studies, 40 were undergoing evaluation as treatments for cancer, and potentially 9 of these (belantamab mafodotin, oportuzumab monatox, margetuximab, dostarlimab, spartalizumab, 131I-omburtamab, loncastuximab tesirine, balstilimab, and zalifrelimab) may enter regulatory review in late 2019 or in 2020. Overall, the biopharmaceutical industry's clinical pipeline of antibody therapeutics is robust, and should provide a continuous supply of innovative products for patients in the future. *Note on key updates through December 18, 2019: 1) the US Food and Drug Administration granted accelerated approval to enfortumab vedotin-ejfv (Padcev) on December 18, 2019, bringing the total number of novel antibody therapeutics granted a first approval in either the US or EU during 2019 to 6; 2) the European Commission approved romosozumab on December 9, 2019; 3) the European Medicines Agency issued a positive opinion for brolucizumab; 4) Sesen Bio initiated a rolling biologics license application (BLA) on December 6, 2019; 5) GlaxoSmithKline submitted a BLA for belantamab mafodotin; and 6) the status of the Phase 3 study (NCT04128696) of GSK3359609, a humanized IgG4 anti-ICOS antibody, in patients with head and neck squamous cell carcinoma was updated to recruiting from not yet recruiting.

Antibodies to watch in 2021

In this 12th annual installment of the Antibodies to Watch article series, we discuss key events in antibody therapeutics development that occurred in 2020 and forecast events that might occur in 2021. The coronavirus disease 2019 (COVID-19) pandemic posed an array of challenges and opportunities to the healthcare system in 2020, and it will continue to do so in 2021. Remarkably, by late November 2020, two anti-SARS-CoV antibody products, bamlanivimab and the casirivimab and imdevimab cocktail, were authorized for emergency use by the US Food and Drug Administration (FDA) and the repurposed antibodies levilimab and itolizumab had been registered for emergency use as treatments for COVID-19 in Russia and India, respectively. Despite the pandemic, 10 antibody therapeutics had been granted the first approval in the US or EU in 2020, as of November, and 2 more (tanezumab and margetuximab) may be granted approvals in December 2020.* In addition, prolgolimab and olokizumab had been granted first approvals in Russia and cetuximab saratolacan sodium was first approved in Japan. The number of approvals in 2021 may set a record, as marketing applications for 16 investigational antibody therapeutics are already undergoing regulatory review by either the FDA or the European Medicines Agency. Of these 16 mAbs, 11 are possible treatments for non-cancer indications and 5 are potential treatments for cancer. Based on the information publicly available as of November 2020, 44 antibody therapeutics are in late-stage clinical studies for non-cancer indications, including 6 for COVID-19, and marketing applications for at least 6 (leronlimab, tezepelumab, faricimab, ligelizumab, garetosmab, and fasinumab) are planned in 2021. In addition, 44 antibody therapeutics are in late-stage clinical studies for cancer indications. Of these 44, marketing application submissions for 13 may be submitted by the end of 2021. *Note added in proof on key events announced during December 1-21, 2020: margetuximab-cmkb and ansuvimab-zykl were approved by FDA on December 16 and 21, 2020, respectively; biologics license applications were submitted for ublituximab and amivantamab.

Antibody-Drug Conjugates and Targeted Treatment Strategies for Hepatocellular Carcinoma: A Drug-Delivery Perspective

Increased understanding of cancer biology, pharmacology and drug delivery has provided a new framework for drug discovery and product development that relies on the unique expression of specific macromolecules (i.e., antigens) on the surface of tumour cells. This has enabled the development of anti-cancer treatments that combine the selectivity of antibodies with the efficacy of highly potent chemotherapeutic small molecules, called antibody-drug conjugates (ADCs). ADCs are composed of a cytotoxic drug covalently linked to an antibody which then selectively binds to a highly expressed antigen on a cancer cell; the conjugate is then internalized by the cell where it releases the potent cytotoxic drug and efficiently kills the tumour cell. There are, however, many challenges in the development of ADCs, mainly around optimizing the therapeutic/safety benefits. These challenges are discussed in this review; they include issues with the plasma stability and half-life of the ADC, its transport from blood into and distribution throughout the tumour compartment, cancer cell antigen expression and the ADC binding affinity to the target antigen, the cell internalization process, cleaving of the cytotoxic drug from the ADC, and the cytotoxic effect of the drug on the target cells. Finally, we present a summary of some of the experimental ADC strategies used in the treatment of hepatocellular carcinoma, from the recent literature.

Multivariate Optimization of the Refolding Process of an Incorrectly Folded Fc-Fusion Protein in a Cell Culture Broth

BACKGROUND

Protein misfolding is a common problem in large-scale production of recombinant proteins, which can significantly reduce the yield of the process.

OBJECTIVE

In this work, we aimed at treating a cell culture broth containing high levels (>45%) of incorrectly folded Fc-fusion proteins by a simple redox buffer system in order to increase the proportion of the protein with correct conformation.

METHODS

Multi-variable process optimization was firstly conducted at a small scale (25 mL), employing an experimental design methodology. After identifying the key variables using a resolution IV Fractional Factorial Design (FFD), the process was then optimized by the Central Composite Design (CCD).

RESULTS

The optimal conditions for the refolding reaction were 340 mM Tris-base, 6.0 mM L-cysteine, 0.5 mM L-cystine, a buffer pH of 9.0, a reaction temperature of 8.5ºC and a reaction time of 24 h. Based on the treatment conditions obtained at a small scale, the process was further scaled up to 4500- L. The misfolded content was always less than 20%. The reaction can proceed well in the absence of chemical additives, such as chaotropic agents, aggregation suppressors, stabilizers and chelators.

CONCLUSION

The refolding process increases the fraction of active protein in the original broth reducing the burden on downstream purification steps markedly.

A brief history of antibody-based therapy

Active and passive immunization have been used to treat human disease for hundreds of years and improvements in technology and knowledge is only increasing the number of therapeutic applications. The current and future use of immunization to treat neurodegenerative diseases are briefly described herein to serve as an introduction to this special issue.

Antibodies to watch in 2019

For the past 10 years, the annual 'Antibodies to watch' articles have provided updates on key events in the late-stage development of antibody therapeutics, such as first regulatory review or approval, that occurred in the year before publication or were anticipated to occur during the year of publication. To commemorate the 10th anniversary of the article series and to celebrate the 2018 Nobel Prizes in Chemistry and in Physiology or Medicine, which were given for work that is highly relevant to antibody therapeutics research and development, we expanded the scope of the data presented to include an overview of all commercial clinical development of antibody therapeutics and approval success rates for this class of molecules. Our data indicate that: 1) antibody therapeutics are entering clinical study, and being approved, in record numbers; 2) the commercial pipeline is robust, with over 570 antibody therapeutics at various clinical phases, including 62 in late-stage clinical studies; and 3) Phase 1 to approval success rates are favorable, ranging from 17-25%, depending on the therapeutic area (cancer vs. non-cancer). In 2018, a record number (12) of antibodies (erenumab (Aimovig), fremanezumab (Ajovy), galcanezumab (Emgality), burosumab (Crysvita), lanadelumab (Takhzyro), caplacizumab (Cablivi), mogamulizumab (Poteligeo), moxetumomab pasudodox (Lumoxiti), cemiplimab (Libtayo), ibalizumab (Trogarzo), tildrakizumab (Ilumetri, Ilumya), emapalumab (Gamifant)) that treat a wide variety of diseases were granted a first approval in either the European Union (EU) or United States (US). As of November 2018, 4 antibody therapeutics (sacituzumab govitecan, ravulizumab, risankizumab, romosozumab) were being considered for their first marketing approval in the EU or US, and an additional 3 antibody therapeutics developed by Chinese companies (tislelizumab, sintilimab, camrelizumab) were in regulatory review in China. In addition, our data show that 3 product candidates (leronlimab, brolucizumab, polatuzumab vedotin) may enter regulatory review by the end of 2018, and at least 12 (eptinezumab, teprotumumab, crizanlizumab, satralizumab, tanezumab, isatuximab, spartalizumab, MOR208, oportuzumab monatox, TSR-042, enfortumab vedotin, ublituximab) may enter regulatory review in 2019. Finally, we found that approximately half (18 of 33) of the late-stage pipeline of antibody therapeutics for cancer are immune checkpoint modulators or antibody-drug conjugates. Of these, 7 (tremelimumab, spartalizumab, BCD-100, omburtamab, mirvetuximab soravtansine, trastuzumab duocarmazine, and depatuxizumab mafodotin) are being evaluated in clinical studies with primary completion dates in late 2018 and in 2019, and are thus 'antibodies to watch'. We look forward to documenting progress made with these and other 'antibodies to watch' in the next installment of this article series.

Antibodies to watch in 2018

The pace of antibody therapeutics development accelerated in 2017, and this faster pace is projected to continue through 2018. Notably, the annual number of antibody therapeutics granted a first approval in either the European Union (EU) or United States (US) reached double-digits (total of 10) for the first time in 2017. The 10 antibodies granted approvals are: brodalumab, dupilumab, sarilumab, guselkumab, benralizumab, ocrelizumab, inotuzumab ozogamicin, avelumab, duvalumab, and emicizumab. Brodalumab, however, had already been approved in Japan in 2016. As of December 1, 2017, nine antibody therapeutics (ibalizumab, burosumab, tildrakizumab, caplacizumab, erenumab, fremanezumab, galcanezumab, romosozumab, mogamulizumab) were in regulatory review in the EU or US, and regulatory actions on their marketing applications are expected by the end of 2018. Based on company announcements and estimated clinical study primary completion dates, and assuming the study results are positive, marketing applications for at least 12 antibody therapeutics that are now being evaluated in late-stage clinical studies may be submitted by the end of 2018. Of the 12 candidates, 8 are for non-cancer indications (lanadelumab, crizanlizumab, ravulizumab, eptinezumab, risankizumab, satralizumab, brolucizumab, PRO140) and 4 are for cancer (sacituzumab govitecan, moxetumomab pasudotox, cemiplimab, ublituximab). Additional antibody therapeutics to watch in 2018 include 19 mAbs undergoing evaluation in late-stage studies with primary completion dates in late 2017 or during 2018. Of these mAbs, 9 are for non-cancer indications (lampalizumab, roledumab, emapalumab, fasinumab, tanezumab, etrolizumab, NEOD001, gantenerumab, anifrolumab) and 10 are for cancer indications (tremelimumab, isatuximab, BCD-100, carotuximab, camrelizumab, IBI308, glembatumumab vedotin, mirvetuximab soravtansine, oportuzumab monatox, L19IL2/L19TNF). Positive clinical study results may enable marketing application submissions in 2018. Brief summaries of these antibody therapeutics are provided in this installment of the 'Antibodies to watch' article series.

Construction of Macaque Immune-Libraries

Rapidly after the clinical success of the first murine therapeutic antibody licensed in 1985 (muromomab-CD3), the first limits of the therapeutic use of antibodies deriving from hybridoma technology appeared. Indeed, the nonhuman nature of these therapeutic antibodies makes them immunogenic when administrated to patients, which develop anti-drug antibodies (ADA). If repeated drug-administrations are needed, the immune response will accelerate the elimination of the drug, leading to a therapeutic failure, or in the worst case to an anaphylactic reaction against the murine protein. Several antibody generations were then developed to obtain better-tolerated molecules: chimeric, humanized, and fully human antibodies. The first antibody generation is fully based on cellular technology (mice hybridoma technology), but the next generations are improved by molecular engineering. Immune antibody phage-display libraries are one successful approach to isolating such engineered antibodies. One strategy to isolate high-affinity and well-tolerated antibodies when no immunized patients are available is based on the phage-display-screening of immune libraries deriving from immunized nonhuman primates, which are phylogenetically close to humans. This chapter presents the strategy for the construction of macaque antibody immune-libraries.

Introduction to Cancer Stem Cells: Past, Present, and Future

The Cancer Stem Cell (CSC) hypothesis postulates the existence of a small population of cancer cells with intrinsic properties allowing for resistance to conventional radiochemotherapy regiments and increased metastatic potential. Clinically, the aggressive nature of CSCs has been shown to correlate with increased tumor recurrence, metastatic spread, and overall poor patient outcome across multiple cancer subtypes. Traditionally, isolation of CSCs has been achieved through utilization of cell surface markers, while the functional differences between CSCs and remaining tumor cells have been described through proliferation, differentiation, and limiting dilution assays. The generated insights into CSC biology have further highlighted the importance of studying intratumoral heterogeneity through advanced functional assays, including CRISPR-Cas9 screens in the search of novel targeted therapies. In this chapter, we review the discovery and characterization of cancer stem cells populations within several major cancer subtypes, recent developments of novel assays used in studying therapy resistant tumor cells, as well as recent developments in therapies targeted at cancer stem cells.

A recombinant avian antibody against VP2 of infectious bursal disease virus protects chicken from viral infection

A stable cell-line was established that expressed the recombinant avian antibody (rAb) against the infectious bursal disease virus (IBDV). rAb exhibited neutralization activity to IBDV-B87 strain in DF1 cells. The minimum rAb concentration required for inhibition of the cytopathic effect (CPE) was 1.563μg/mL. To test the efficacy of rAb, a 168-h cohabitation challenge experiment was performed to transmit the disease from the chickens challenged with vvIBDV (HLJ0504 strain) to three test groups of chickens, i.e. (1) chickens treated with rAb, (2) chickens treated with yolk antibody, and (3) non-treatment chickens. The survival rates of chickens treated with rAb, yolk antibody and without treatment were 73%, 67% and 20%, respectively. Another batch of chickens was challenged with IBDV (BC6/85 strain) and then injected with rAb (1.0mg/kg) 6, 24 and 36h post-challenge. Non-treatment chickens had 100% morbidity, whereas those administered with rAb exhibited only 20% morbidity. Morbidity was evaluated using clinical indicators and bursal histopathological section. This study provides a new approach to treating IBDV and the rAb represents a promising candidate for this IBDV therapy.

Computational Tools for Aiding Rational Antibody Design

Antibodies are a group of proteins responsible for mediating immune reactions in vertebrates. They are able to bind a variety of structural motifs on noxious molecules tagging them for elimination from the organism. As a result of their versatile binding properties, antibodies are currently one of the most important classes of biopharmaceuticals. In this chapter, we discuss how knowledge-based computational methods can aid experimentalists in the development of potent antibodies. When using common experimental methods for antibody development, we often know the sequence of an antibody that binds to our molecule, antigen, of interest. We may also have a structure or model of the antigen. In these cases, computational methods can help by both modeling the antibody and identifying the antibody-antigen contact residues. This information can then play a key role in the rational design of more potent antibodies.

Antibodies to watch in 2017

Over 50 investigational monoclonal antibody (mAb) therapeutics are currently undergoing evaluation in late-stage clinical studies, which is expected to drive a trend toward first marketing approvals of at least 6–9 mAbs per year in the near-term. In the United States (US), a total of 6 and 9 mAbs were granted first approvals during 2014 and 2015, respectively; all these products are also approved in the European Union (EU). As of December 1, 2016, 6 mAbs (atezolizumab, olaratumab, reslizumab, ixekizumab, bezlotoxumab, oblitoxaximab) had been granted first approvals during 2016 in either the EU or US. Brodalumab, was granted a first approval in Japan in July 2016. Regulatory actions on marketing applications for brodalumab in the EU and US are not expected until 2017. In 2017, first EU or US approvals may also be granted for at least nine mAbs (ocrelizumab, avelumab, Xilonix, inotuzumab ozogamicin, dupilumab, sirukumab, sarilumab, guselkumab, romosozumab) that are not yet approved in any country. Based on announcements of company plans for regulatory submissions and the estimated completion dates for late-stage clinical studies, and assuming the study results are positive, marketing applications for at least 6 antibody therapeutics (benralizumab, tildrakizumab, emicizumab, galcanezumab, ibalizumab, PRO-140) that are now being evaluated in late-stage clinical studies may be submitted during December 2016* or 2017. Other ‘antibodies to watch' in 2017 include 20 mAbs are undergoing evaluation in pivotal studies that have estimated primary completion dates in late 2016 or during 2017. Of these, 5 mAbs are for cancer (durvalumab, JNJ-56022473, ublituximab, anetumab ravtansine, glembatumumab vedotin) and 15 mAbs are for non-cancer indications (caplacizumab, lanadelumab, roledumab, tralokinumab, risankizumab, SA237, emapalumab, suptavumab, erenumab, eptinezumab, fremanezumab, fasinumab, tanezumab, lampalizumab, brolucizumab). Positive results from these studies may enable submission of marketing applications in 2017 or 2018, or provide justification for additional studies. *See note added in proof for update through December 31, 2016.

Antibodies to watch in 2016

The number of novel antibody therapeutics that received first marketing approvals in 2015 met expectations, with 6 (alirocumab (Praluent®), evolocumab (Repatha®), daratumumab (Darzalex®), dinutuximab (Unituxin®), idarucizumab (Praxbind®), mepolizumab (Nucala®)) granted first approvals as of mid-November*. Seven novel antibody therapeutics (begelomab, brodalumab, elotuzumab, ixekizumab, necitumumab, obiltoxaximab, reslizumab) are in regulatory review, and thus a similar number, if not more, are projected to gain first approvals in 2016. Commercial late-stage antibody therapeutics development exceeded expectations by increasing from 39 candidates in Phase 3 studies as of late 2014 to 53 as of late 2015. Of the 53 candidates, transitions to regulatory review by the end of 2016 are projected for 8 (atezolizumab, benralizumab, bimagrumab, durvalumab, inotuzumab ozogamicin, lebrikizumab, ocrelizumab, tremelimumab). Other "antibodies to watch" include 15 candidates (bavituximab, bococizumab, dupilumab, fasinumab, fulranumab, gevokizumab, guselkumab, ibalizumab, LY2951742, onartuzumab, REGN2222, roledumab, romosozumab, sirukumab, Xilonix) undergoing evaluation in Phase 3 studies that have estimated primary completion dates in 2016. As evidenced by the antibody therapeutics discussed in this perspective, the biopharmaceutical industry has a highly active late-stage clinical pipeline that may deliver numerous new products to the global market in the near future. *See Note added in proof for updates through December 31, 2015.

Antibodies to watch in 2015

The commercial pipeline of recombinant antibody therapeutics is robust and dynamic. As of early December 2014, a total of 6 such products (vedolizumab, siltuximab, ramucirumab, pembrolizumab, nivolumab, blinatumomab) were granted first marketing approvals in 2014. As discussed in this perspective on antibodies in late-stage development, the outlook for additional approvals, potentially still in 2014 and certainly in 2015, is excellent as marketing applications for 7 antibody therapeutics (secukinumab, evolocumab, mepolizumab, dinutuximab, nivolumab, blinatumomab, necitumumab) are undergoing a first regulatory review in the EU or US. Of the 39 novel mAbs currently in Phase 3 studies, a marketing application for one (alirocumab) may be submitted in late 2014, and marketing application submissions for at least 4 (reslizumab, ixekizumab, ocrelizumab, obiltoxaximab) are expected in 2015. Other 'antibodies to watch' are those in Phase 3 studies with estimated primary completion dates in late 2014 or 2015, which includes 13 for non-cancer indications (brodalumab, bimagrumab, bococizumab, MABp1, gevokizumab, dupilumab, sirukumab, sarilumab, tildrakizumab, guselkumab, epratuzumab, combination of actoxumab + bezlotoxumab, romosozumab) and 2 (racotumomab and clivatuzumab tetraxetan) undergoing evaluation as treatments for cancer. In addition to the novel antibody therapeutics mentioned, biosimilar infliximab and biosimilar trastuzumab are 'antibodies to watch' in 2015 because of their potential for entry into the US market and regulatory review, respectively.

LAPS-FSH: a new and effective long-acting follicle-stimulating hormone analogue for the treatment of infertility

Although several long-acting follicle-stimulating hormone (FSH) therapies have been developed to enhance the ovarian response, a disadvantage of FSH therapy is its relatively short half-life, which requires women to receive one to two injections per day for almost 2 weeks. In the present study, we developed a novel FSH analogue by conjugating recombinant human FSH (rhFSH) and the constant region of the human immunoglobulin G4 fragment via non-peptidyl linkers. The efficacy of the FSH analogue was evaluated in vitro by cAMP level assessments, pharmacokinetic studies and a determination of ovarian weight and by comparing these findings with the results from other FSH analogues. In addition, the total number of antral and Graafian follicles was determined after 7 days of treatment with control, 6µgkg(-1) follitropin β, 6, 12 or 42µgkg(-1) corifollitropin α or 3, 6 or 12µgkg(-1) long acting protein/peptide discovery-follicle-stimulating hormone (LAPS-FSH). As a result, the animals treated with 12µgkg(-1) LAPS-FSH produced additional and larger healthy follicles. These data demonstrate that LAPS-FSH promotes growth and inhibits atresia of the ovarian follicle compared with other available drugs, suggesting that our new drug enhances the efficacy and duration of treatment. It is expected that our new FSH analogue will result in a higher chance of pregnancy in patients who are unresponsive to other drugs.

Fc-fusion proteins and FcRn: structural insights for longer-lasting and more effective therapeutics

Nearly 350 IgG-based therapeutics are approved for clinical use or are under development for many diseases lacking adequate treatment options. These include molecularly engineered biologicals comprising the IgG Fc-domain fused to various effector molecules (so-called Fc-fusion proteins) that confer the advantages of IgG, including binding to the neonatal Fc receptor (FcRn) to facilitate in vivo stability, and the therapeutic benefit of the specific effector functions. Advances in IgG structure-function relationships and an understanding of FcRn biology have provided therapeutic opportunities for previously unapproachable diseases. This article discusses approved Fc-fusion therapeutics, novel Fc-fusion proteins and FcRn-dependent delivery approaches in development, and how engineering of the FcRn-Fc interaction can generate longer-lasting and more effective therapeutics.

Application of AMOR in craniofacial rabbit bone bioengineering

Endogenous molecular and cellular mediators modulate tissue repair and regeneration. We have recently described antibody mediated osseous regeneration (AMOR) as a novel strategy for bioengineering bone in rat calvarial defect. This entails application of anti-BMP-2 antibodies capable of in vivo capturing of endogenous osteogenic BMPs (BMP-2, BMP-4, and BMP-7). The present study sought to investigate the feasibility of AMOR in other animal models. To that end, we examined the efficacy of a panel of anti-BMP-2 monoclonal antibodies (mAbs) and a polyclonal Ab immobilized on absorbable collagen sponge (ACS) to mediate bone regeneration within rabbit calvarial critical size defects. After 6 weeks, de novo bone formation was demonstrated by micro-CT imaging, histology, and histomorphometric analysis. Only certain anti-BMP-2 mAb clones mediated significant in vivo bone regeneration, suggesting that the epitopes with which anti-BMP-2 mAbs react are critical to AMOR. Increased localization of BMP-2 protein and expression of osteocalcin were observed within defects, suggesting accumulation of endogenous BMP-2 and/or increased de novo expression of BMP-2 protein within sites undergoing bone repair by AMOR. Considering the ultimate objective of translation of this therapeutic strategy in humans, preclinical studies will be necessary to demonstrate the feasibility of AMOR in progressively larger animal models.

Adhiron: a stable and versatile peptide display scaffold for molecular recognition applications

We have designed a novel non-antibody scaffold protein, termed Adhiron, based on a phytocystatin consensus sequence. The Adhiron scaffold shows high thermal stability (T_m ca. 101°C), and is expressed well in Escherichia coli. We have determined the X-ray crystal structure of the Adhiron scaffold to 1.75 Å resolution revealing a compact cystatin-like fold. We have constructed a phage-display library in this scaffold by insertion of two variable peptide regions. The library is of high quality and complexity comprising 1.3 × 10¹⁰ clones. To demonstrate library efficacy, we screened against the yeast Small Ubiquitin-like Modifier (SUMO). In selected clones, variable region 1 often contained sequences homologous to the known SUMO interactive motif (V/I-X-V/I-V/I). Four Adhirons were further characterised and displayed low nanomolar affinities and high specificity for yeast SUMO with essentially no cross-reactivity to human SUMO protein isoforms. We have identified binders against >100 target molecules to date including as examples, a fibroblast growth factor (FGF1), platelet endothelial cell adhesion molecule (PECAM-1; CD31), the SH2 domain Grb2 and a 12-aa peptide. Adhirons are highly stable and well expressed allowing highly specific binding reagents to be selected for use in molecular recognition applications.

Antibody engineering and therapeutics, The Annual Meeting of the Antibody Society: December 8-12, 2013, Huntington Beach, CA

The 24^th Antibody Engineering & Therapeutics meeting brought together a broad range of participants who were updated on the latest advances in antibody research and development. Organized by IBC Life Sciences, the gathering is the annual meeting of The Antibody Society, which serves as the scientific sponsor. Preconference workshops on 3D modeling and delineation of clonal lineages were featured, and the conference included sessions on a wide variety of topics relevant to researchers, including systems biology; antibody deep sequencing and repertoires; the effects of antibody gene variation and usage on antibody response; directed evolution; knowledge-based design; antibodies in a complex environment; polyreactive antibodies and polyspecificity; the interface between antibody therapy and cellular immunity in cancer; antibodies in cardiometabolic medicine; antibody pharmacokinetics, distribution and off-target toxicity; optimizing antibody formats for immunotherapy; polyclonals, oligoclonals and bispecifics; antibody discovery platforms; and antibody-drug conjugates.

Nanoscale imaging and mechanical analysis of Fc receptor-mediated macrophage phagocytosis against cancer cells

Fc receptor-mediated macrophage phagocytosis against cancer cells is an important mechanism in the immune therapy of cancers. Traditional research about macrophage phagocytosis was based on optical microscopy, which cannot reveal detailed information because of the 200-nm-resolution limit. Quantitatively investigating the macrophage phagocytosis at micro- and nanoscale levels is still scarce. The advent of atomic force microscopy (AFM) offers an excellent analytical instrument for quantitatively investigating the biological processes at single-cell and single-molecule levels under native conditions. In this work, we combined AFM and fluorescence microscopy to visualize and quantify the detailed changes in cell morphology and mechanical properties during the process of Fc receptor-mediated macrophage phagocytosis against cancer cells. Lymphoma cells were discernible by fluorescence staining. Then, the dynamic process of phagocytosis was observed by time-lapse optical microscopy. Next, AFM was applied to investigate the detailed cellular behaviors during macrophage phagocytosis under the guidance of fluorescence recognition. AFM imaging revealed the distinct features in cellular ultramicrostructures for the different steps of macrophage phagocytosis. AFM cell mechanical property measurements indicated that the binding of cancer cells to macrophages could make macrophages become stiffer. The experimental results provide novel insights in understanding the Fc-receptor-mediated macrophage phagocytosis.

Ustekinumab: moving the target from psoriasis to Crohn's disease

Crohn's disease (CD) is an inflammatory bowel disease whose precise etiology is still unknown, and therefore a causal therapy is not yet available. Studies showing the overexpression of IL-12 and IL-23, polymorphisms in genes encoding those cytokines and their receptors and genome-wide association studies have linked Crohn's pathogenesis with IL-12/23 pathway. Ustekinumab is a novel therapeutic IgG₁ kappa monoclonal antibody that modulates Th1 and Th17 function, by blocking the p40 subunit of both IL-12 and IL-23 and preventing the interaction with their receptors on T cells, natural killer cells and antigen-presenting cells with established efficacy in psoriasis. This review will mainly focus on the available evidence on the role of ustekinumab in moderate-to-severe CD. The potential role of this biologic in the armamentarium of CD therapy is discussed.

Stability of monoclonal antibodies at high-concentration: head-to-head comparison of the IgG1 and IgG4 subclass

Few studies have so far directly compared the impact of antibody subclass on protein stability. This case study investigates two mAbs (one IgG1 and one IgG4 ) with identical variable region. Investigations of mAbs that recognize similar epitopes are necessary to identify possible differences between the IgG subclasses. Both physical and chemical stability were evaluated by applying a range of methods to measure formation of protein aggregates [size-exclusion chromatography (SEC)-HPLC and UV340 nm], structural integrity (circular dichroism and FTIR), thermodynamic stability (differential scanning calorimetry), colloidal interactions (dynamic light scattering), and fragmentation and deamidation (SEC-HPLC and capillary isoelectric focusing). The impact of pH (4-9) and ionic strength (10 and 150 mM) was investigated using highly-concentrated (150 mg/mL) mAb formulations. Lower conformational stability was identified for the IgG4 resulting in increased levels of soluble aggregates. The IgG1 was chemically less stable as compared with the IgG4 , presumably because of the higher flexibility in the IgG1 hinge region. The thermodynamic stability of individual mAb domains was also addressed in detail. The stability of our mAb molecules is clearly affected by the IgG framework, and this study suggests that subclass switching may alter aggregation propensity and aggregation pathway and thus potentially improve the overall formulation stability while retaining antigen specificity.

Antibodies to watch in 2014

Since 2010, mAbs has documented the biopharmaceutical industry's progress in transitioning antibody therapeutics to first Phase 3 clinical studies and regulatory review, and its success at gaining first marketing approvals for antibody-based products. This installment of the "Antibodies to watch" series outlines events anticipated to occur between December 2013 and the end of 2014, including first regulatory actions on marketing applications for vedolizumab, siltuximab, and ramucirumab, as well as the Fc fusion proteins Factor IX-Fc and Factor VIII-Fc; and the submission of first marketing applications for up to five therapeutics (secukinumab, ch14.18, onartuzumab, necitumumab, gevokizumab). Antibody therapeutics in Phase 3 studies are described, with an emphasis on those with study completion dates in 2014, including antibodies targeting interleukin-17a or the interleukin-17a receptor (secukinumab, ixekizumab, brodalumab), proprotein convertase subtilisin/kexin type 9 (alirocumab, evolocumab, bococizumab), and programmed death 1 receptor (lambrolizumab, nivolumab). Five antibodies with US Food and Drug Administration's Breakthrough Therapy designation (obinutuzumab, ofatumumab, lambrolizumab, bimagrumab, daratumumab) are also discussed.

With or without sugar? (A)glycosylation of therapeutic antibodies

Antibodies and antibody-based drugs are currently the fastest-growing class of therapeutics. Over the last three decades, more than 30 therapeutic monoclonal antibodies and derivatives thereof have been approved for and successfully applied in diverse indication areas including cancer, organ transplants, autoimmune/inflammatory disorders, and cardiovascular disease. The isotype of choice for antibody therapeutics is human IgG, whose Fc region contains a ubiquitous asparagine residue (N297) that acts as an acceptor site for N-linked glycans. The nature of these glycans can decisively influence the therapeutic performance of a recombinant antibody, and their absence or modification can lead to the loss of Fc effector functions, greater immunogenicity, and unfavorable pharmacokinetic profiles. However, recent studies have shown that aglycosylated antibodies can be genetically engineered to display novel or enhanced effector functions and that favorable pharmacokinetic properties can be preserved. Furthermore, the ability to produce aglycosylated antibodies in lower eukaryotes and bacteria offers the potential to broaden and simplify the production platforms and avoid the problem of antibody heterogeneity, which occurs when mammalian cells are used for production. In this review, we discuss the importance of Fc glycosylation focusing on the use of aglycosylated and glyco-engineered antibodies as therapeutic proteins.

Expression of recombinant antibodies

Recombinant antibodies are highly specific detection probes in research, diagnostics, and have emerged over the last two decades as the fastest growing class of therapeutic proteins. Antibody generation has been dramatically accelerated by in vitro selection systems, particularly phage display. An increasing variety of recombinant production systems have been developed, ranging from Gram-negative and positive bacteria, yeasts and filamentous fungi, insect cell lines, mammalian cells to transgenic plants and animals. Currently, almost all therapeutic antibodies are still produced in mammalian cell lines in order to reduce the risk of immunogenicity due to altered, non-human glycosylation patterns. However, recent developments of glycosylation-engineered yeast, insect cell lines, and transgenic plants are promising to obtain antibodies with "human-like" post-translational modifications. Furthermore, smaller antibody fragments including bispecific antibodies without any glycosylation are successfully produced in bacteria and have advanced to clinical testing. The first therapeutic antibody products from a non-mammalian source can be expected in coming next years. In this review, we focus on current antibody production systems including their usability for different applications.

Bispecific antibodies and trispecific immunocytokines for targeting the immune system against cancer: preparing for the future

Monoclonal anti-tumor antibodies (mAbs) that are clinically effective usually recruit, via their constant fragment (Fc) domain, Fc receptor (FcR)-positive accessory cells of the immune system and engage these additionally against the tumor. Since T cells are FcR negative, these important cells are not getting involved. In contrast to mAbs, bispecific antibodies (bsAbs) can be designed in such a way that they involve T cells. bsAbs are artificially designed molecules that bind simultaneously to two different antigens, one on the tumor cell, the other one on an immune effector cell such as CD3 on T cells. Such dual antibody constructs can cross-link tumor cells and T cells. Many such bsAb molecules at the surface of tumor cells can thus build a bridge to T cells and aggregate their CD3 molecules, thereby activating them for cytotoxic activity. BsAbs can also contain a third binding site, for instance a Fc domain or a cytokine that would bind to its respective cytokine receptor. The present review discusses the pros and cons for the use of the Fc fragment during the development of bsAbs using either cell-fusion or recombinant DNA technologies. The recombinant antibody technology allows the generation of very efficient bsAbs containing no Fc domain such as the bi-specific T-cell engager (BiTE). The strong antitumor activity of these molecules makes them very interesting new cancer therapeutics. Over the last decade, we have developed another concept, namely to combine bsAbs and multivalent immunocytokines with a tumor cell vaccine. The latter are patient-derived tumor cells modified by infection with a virus. The virus-Newcastle Disease Virus (NDV)-introduces, at the surface of the tumor cells, viral molecules that can serve as general anchors for the bsAbs. Our strategy aims at redirecting, in an Fc-independent fashion, activities of T cells and accessory cells against autologous tumor antigens. It creates very promising perspectives for a new generation of efficient and safe cancer therapeutics that should confer long-lasting anti-tumor immunity.

Antibodies to watch in 2013: Mid-year update

The transitions of antibody therapeutics to late-stage clinical development, regulatory review and the market are proceeding at a rapid pace in 2013. Since late 2012, two monoclonal antibody (mAb) therapeutics (itolizumab, trastuzumab emtansine) received their first approvals, first marketing applications for three mAbs (vedolizumab, ramucirumab, obinutuzumab) were submitted to regulatory agencies, and five mAbs (brodalumab, MABp1, moxetumomab pasudotox, tildrakizumab, rilotumumab) entered their first Phase 3 studies. The current total of commercially-sponsored antibody therapeutics undergoing evaluation in late-stage studies is 30. Recently announced study results for farletuzumab, naptumomab estafenatox, and tabalumab indicate that clinical endpoints were not met in some Phase 3 studies of these product candidates.

Comparison of the in vitro and in vivo stability of a succinimide intermediate observed on a therapeutic IgG1 molecule

Deamidation of asparagine residues, a post-translational modification observed in proteins, is a common degradation pathway in monoclonal antibodies (mAbs). The kinetics of deamidation is influenced by primary sequence as well as secondary and tertiary folding. Analytical hydrophobic interaction chromatography (HIC) is used to evaluate hydrophobicity of candidate mAbs and uncover post-translational modifications. Using HIC, we discovered atypical heterogeneity in a highly hydrophobic molecule (mAb-1). Characterization of the different HIC fractions using LC/MS/MS revealed a stable succinimide intermediate species localized to an asparagine-glycine motif in the heavy chain binding region. The succinimide intermediate was stable in vitro at pH 7 and below and increased on storage at 25°C and 40°C. Biacore evaluation showed a decrease in binding affinity of the succinimide intermediate compared with the native asparagine molecule. In vivo studies of mAb-1 recovered from a pharmacokinetic study in cynomolgus monkeys revealed an unstable succinimide species and rapid conversion to aspartic/iso-aspartic acid. Mutation from asparagine to aspartic acid led to little loss in affinity. This study illustrates the importance of evaluating modifications of therapeutic mAbs both in vitro and in serum, the intended environment of the molecule. Potential mechanisms that stabilize the succinimide intermediate in vitro are discussed.

The structure of dual-variable-domain immunoglobulin molecules alone and bound to antigen

A dual-specific, tetravalent immunoglobulin G-like molecule, termed dual variable domain immunoglobulin (DVD-Ig™), is engineered to block two targets. Flexibility modulates Fc receptor and complement binding, but could result in undesirable cross-linking of surface antigens and downstream signaling. Understanding the flexibility of parental mAbs is important for designing and retaining functionality of DVD-Ig™ molecules. The architecture and dynamics of a DVD-Ig™ molecule and its parental mAbs was examined using single particle electron microscopy. Hinge angles measured for the DVD-Ig™ molecule were similar to the inner antigen parental mAb. The outer binding domain of the DVD-Ig™ molecule was highly mobile and three-dimensional (3D) analysis showed binding of inner antigen caused the outer domain to fold out of the plane with a major morphological change. Docking high-resolution X-ray structures into the 3D electron microscopy map supports the extraordinary domain flexibility observed in the DVD-Ig™ molecule allowing antigen binding with minimal steric hindrance.

Cells and cell lysates: a direct approach for engineering antibodies against membrane proteins using yeast surface display

Membrane proteins (MPs) are often desirable targets for antibody engineering. However, the majority of antibody engineering platforms depend implicitly on aqueous solubility of the target antigen which is often problematic for MPs. Recombinant, soluble forms of MPs have been successfully employed as antigen sources for antibody engineering, but heterologous expression and purification of soluble MP fragments remains a challenging and time-consuming process. Here we present a more direct approach to aid in the engineering of antibodies to MPs. By combining yeast surface display technology directly with whole cells or detergent-solubilized whole-cell lysates, antibody libraries can be screened against MP antigens in their near-native conformations. We also describe how the platform can be adapted for antibody characterization and antigen identification. This collection of compatible methods serves as a basis for antibody engineering against MPs and it is predicted that these methods will mature in parallel with developments in membrane protein biochemistry and solubilization technology.

Protein-polyanion interactions for the controlled release of monoclonal antibodies

The objective of the present study was to investigate ionic interactions between alginate and a monoclonal antibody (mAb1) and to utilize those interactions for the sustained release of mAb1. The existence of ionic interactions between alginate and mAb1 was strongly reflected by their rheological behavior. A 3-4 times increase in storage modulus (G') was observed by addition of 30 mg/mL mAb1 to a 20 mg/mL alginate solution. This increase was strongly dependent on pH and ionic strength. In vitro release studies revealed a marked pH-dependence of release rates and the reversibility of alginate-mAb1 complexation under physiological conditions. Two alginate-mAb1 sustained release formulations were developed by an internal gelation technique using CaCO(3) and CaHPO(4) as calcium sources for physical cross-linking. The CaCO(3) formulation provided a stable pH-environment, optimally suited for pH-sensitive proteins. CaHPO(4) led to a lower pH and stronger alginate-mAb1 interactions. The CaHPO(4) cross-linked alginate released mAb1 over a period of 10-15 days. The long release period and changes in viscoelastic properties of alginate, when being mixed with mAb1, indicate the incorporation of mAb1 molecules into a mixed network with alginate. The results of this study demonstrate that ionic interactions between polyanions and mAb1 are present and that they can be exploited for sustained release delivery of mAb1.

Characterization and comparison of commercially available TNF receptor 2-Fc fusion protein products

Because of rapidly increasing market demand and rising cost pressure, the innovator of etanercept (Enbrel®) will inevitably face competition from biosimilar versions of the product. In this study, to elucidate the differences between the reference etanercept and its biosimilars, we characterized and compared the quality attributes of two commercially available, biosimilar TNF receptor 2-Fc fusion protein products. Biosimilar 1 showed high similarity to Enbrel® in critical quality attributes including peptide mapping, intact mass, charge variant, purity, glycosylation and bioactivity. In contrast, the intact mass and MS/MS analysis of biosimilar 2 revealed a mass difference indicative of a two amino acid residue variance in the heavy chain (Fc) sequences. Comprehensive glycosylation profiling confirmed that biosimilar 2 has significantly low sialylated N-oligosaccharides. Biosimilar 2 also displayed significant differences in charge attributes compared with the reference product. Interestingly, biosimilar 2 exhibited similar affinity and bioactivity levels compared with the reference product despite the obvious difference in primary structure and partial physiochemical properties. For a biosimilar development program, comparative analytical data can influence decisions about the type and amount of animal and clinical data needed to demonstrate biosimilarity. Because of the limited clinical experience with biosimilars at the time of their approval, a thorough knowledge surrounding biosimilars and a case-by-case approach are needed to ensure the appropriate use of these products.

A high throughput capillary electrophoresis method to obtain pharmacokinetics and quality attributes of a therapeutic molecule in circulation

Therapeutic proteins circulating in blood are in a highly crowded, redox environment at high temperatures of ~37°C. These molecules circulate in the presence of enzymes and other serum proteins making it difficult to predict from in vitro studies the stability, aggregation or pharmacokinetics of a therapeutic protein in vivo. Here, we describe use of a high throughput capillary electrophoresis based microfluidic device (LabChip GXII) to obtain pharmacokinetics (PK) of a fluorescently labeled human mAb directly from serum. The non-labeled and labeled mAbs were evaluated in single dose rat PK studies using a traditional ELISA method or LabChip GXII, respectively. The fluorescent dye did not significantly alter clearance of this particular mAb, and PK parameters were comparable for labeled and unlabeled molecules. Further, from the CE profile we concluded that the mAb was resistant to fragmentation or aggregation during circulation. In a follow-up experiment, dimers were generated from the mAb using photo-induced cross-linking of unmodified proteins (PICUP) and labeled with the same fluorophore. The extent of dimerization was incomplete and some monomer and higher molecular weight species were found in the preparation. In rat PK studies, the serum concentration-time profile of the three entities present in the dimer preparation could be followed simultaneously with the GXII technology. While further studies are warranted, we believe this method could be adapted to obtain PK of different forms of antibodies (oxidized, deamidated or various glycosylated species) and other proteins.

Avidity confers FcγR binding and immune effector function to aglycosylated immunoglobulin G1

Immunoglobulin G (IgG) antibodies are an integral part of the adaptive immune response that provide a direct link between humoral and cellular components of the immune system. Insights into relationships between the structure and function of human IgGs have prompted molecular engineering efforts to enhance or eliminate specific properties, such as Fc-mediated immune effector functions. Human IgGs have an N-glycosylation site at Asn297, located in the second heavy chain constant region (CH2). The composition of the Fc glycan can have substantial impacts on Fc gamma receptor(FcγR) binding. The removal of the glycan through enzymatic deglycosylation or mutagenesis of the N-linked glycosylation site has been reported to "silence" FcγR-binding and effector functions, particularly with assays that measure monomeric binding. However, interactions between IgGs and FcγRs are not limited to monomeric interactions but can be influenced by avidity, which takes into account the sum of multimeric interactions between antigen-engaged IgGs and FcγRs. We show here that under in vitro conditions, which allowed avidity binding, aglycosylated IgGs can bind to one of the FcγRs, FcγRI, and mediate effector functions. These studies highlight how the valency of a molecular interaction (monomeric binding versus avidity binding) can influence antibody/FcγR interactions such that avidity effects can translate very low intrinsic affinities into significant functional outcomes.

Highly aggregated antibody therapeutics can enhance the in vitro innate and late-stage T-cell immune responses

Aggregation of biotherapeutics has the potential to induce an immunogenic response. Here, we show that aggregated therapeutic antibodies, previously generated and determined to contain a variety of attributes (Joubert, M. K., Luo, Q., Nashed-Samuel, Y., Wypych, J., and Narhi, L. O. (2011) J. Biol. Chem. 286, 25118–25133), can enhance the in vitro innate immune response of a population of naive human peripheral blood mononuclear cells. This response depended on the aggregate type, inherent immunogenicity of the monomer, and donor responsiveness, and required a high number of particles, well above that detected in marketed drug products, at least in this in vitro system. We propose a cytokine signature as a potential biomarker of the in vitro peripheral blood mononuclear cell response to aggregates. The cytokines include IL-1β, IL-6, IL-10, MCP-1, MIP-1α, MIP-1β, MMP-2, and TNF-α. IL-6 and IL-10 might have an immunosuppressive effect on the long term immune response. Aggregates made by stirring induced the highest response compared with aggregates made by other methods. Particle size in the 2–10 μm range and the retention of some folded structure were associated with an increased response. The mechanism of aggregate activation at the innate phase was found to occur through specific cell surface receptors (the toll-like receptors TLR-2 and TLR-4, FcγRs, and the complement system). The innate signal was shown to progress to an adaptive T-cell response characterized by T-cell proliferation and secretion of T-cell cytokines. Investigating the ability of aggregates to induce cytokine signatures as biomarkers of immune responses is essential for determining their risk of immunogenicity.