What's fueling the biotech engine--2010 to 2011

Long-acting Parenteral Drug Delivery Systems for the Treatment of Chronic Diseases

The management of chronic conditions often requires patients to take daily medication for an extended duration. However, the need for daily dosing can lead to nonadherence to the therapy, which can result in the recurrence of the disease. Long-acting parenteral drug delivery systems have the potential to improve the treatment of chronic conditions. These systems use various technologies, such as oil-based injectables, PLGA-based microspheres, and in situ forming gel-based depots, to deliver different types of drugs. The use of long-acting parenteral formulations for the treatment of chronic infections such as HIV/AIDS and tuberculosis is a recent development in the field. Researchers are also exploring the use of long-acting parenteral formulations for the treatment of malaria, with the aim of reducing dosing frequency and improving adherence to treatment. This review discusses various aspects of long-acting formulation development, including the impact of the physicochemical properties of the drug, the type of long-acting formulation, and the route of administration. The clinical significance of long-acting formulations and recent advances in the field, such as long-acting nanoformulations and long-acting products currently in clinical trials, have also been highlighted.

Separation of charge variants of a monoclonal antibody by overloaded ion exchange chromatography

A procedure for adjusting the content of charge variants of monoclonal antibody by ion exchange chromatography has been developed. The band splitting phenomenon was utilized to split the protein load into two parts, i.e., the flowthrough and bound fractions, which were either enriched or depleted with some of variants. The phenomenon was triggered by thermodynamic effects resulting from oversaturation of the resin binding sites at high column loadings as well as from kinetic effects arising from limited rates of mass transport. Cation exchange chromatography (CEX) and anion exchange chromatography (AEX) separations were examined, with the reverse order of the variant elution: acidic, main, basic in CEX, and basic, main, acidic in AEX, and the corresponding reverse enrichment tendency in the collected fractions. The separations were performed by pH gradient, whose course was simplified to two stages: isocratic loading and washing at mild pH to load and partly elute the protein, followed by a rapid pH change towards non-binding conditions to desorb the remains of the protein load. To improve yield of the operation, possibility of recycling of waste fractions was considered. To predict the process performance, a dynamic model was developed, which accounted for both adsorption kinetics and thermodynamics.

Monodisperse and Polydisperse PEGylation of Peptides and Proteins: A Comparative Study

Although PEGylation is widely used in biomedicine with great success, it suffers from many drawbacks, such as polydispersity, nonbiodegradability, and loss of precursor potency. Recently, the search for polyethylene glycol (PEG) substitutes has attracted considerable attention. Some of the substitutes partially address the drawbacks of PEGs, but sacrifice the "stealth" effect of PEGs and bring in new issues. Herein, we developed monodisperse oligoethylene glycol (M-OEG) polyamides over 5000 Da as biodegradable and monodisperse PEGylation (M-PEGylation) agents, which provided M-PEGylated peptides and proteins with high monodispersity and a biodegradable PEG moiety. Compared to regular PEGylated proteins with a complex "stealth" cloud of PEG, the hydrogen bond interactions between the M-OEG polyamides and proteins provided the M-PEGylated protein with a biodegradable "stealth" cloak. The monodisperse and biodegradable M-PEGylation strategy as well as the peculiar protein-M-OEG polyamide interactions may shed light on many long-lasting issues during the development of PEGylated biologic drugs, such as monodispersity, biodegradability, and tunable conformation.

One-pot N-glycosylation remodeling of IgG with non-natural sialylglycopeptides enables glycosite-specific and dual-payload antibody-drug conjugates

Chemoenzymatic transglycosylation catalyzed by endo-S mutants is a powerful tool for in vitro glycoengineering of therapeutic antibodies. In this paper, we report a one-pot chemoenzymatic synthesis of glycoengineered Herceptin using an egg-yolk sialylglycopeptide (SGP) substrate. Combining this one-pot strategy with novel non-natural SGP derivatives carrying azido or alkyne tags, glycosite-specific conjugation was enabled for the development of new antibody-drug conjugates (ADCs). The site-specific ADCs and semi-site-specific dual-drug ADCs were successfully achieved and characterized with SDS-PAGE, intact antibody or ADC mass spectrometry analysis, and PNGase-F digestion analysis. Cancer cell cytotoxicity assay revealed that small-molecule drug release of these ADCs relied on the cleavable Val-Cit linker fragment embedded in the structure. These results represent a new approach for glycosite-specific and dual-drug ADC design and rapid synthesis, and also provide the structural requirement for their biologic activities.

Generation of therapeutic protein variants with the human serum albumin binding capacity via site-specific fatty acid conjugation

Extension of the serum half-life is an important issue in developing new therapeutic proteins and expanding applications of existing therapeutic proteins. Conjugation of fatty acid, a natural human serum albumin ligand, to a therapeutic protein/peptide was developed as a technique to extend the serum half-life in vivo by taking advantages of unusually long serum half-life of human serum albumin (HSA). However, for broad applications of fatty acid-conjugation, several issues should be addressed, including a poor solubility of fatty acid and a substantial loss in the therapeutic activity. Therefore, herein we systematically investigate the conditions and components in conjugation of fatty acid to a therapeutic protein resulting in the HSA binding capacity without compromising therapeutic activities. By examining the crystal structure and performing dye conjugation assay, two sites (W160 and D112) of urate oxidase (Uox), a model therapeutic protein, were selected as sites for fatty acid-conjugation. Combination of site-specific incorporation of a clickable p-azido-L-phenylalanine to Uox and strain-promoted azide-alkyne cycloaddition allowed the conjugation of fatty acid (palmitic acid analog) to Uox with the HSA binding capacity and retained enzyme activity. Deoxycholic acid, a strong detergent, greatly enhanced the conjugation yield likely due to the enhanced solubility of palmitic acid analog.

Monoclonal Antibodies Production Platforms: An Opportunity Study of a Non-Protein-A Chromatographic Platform Based on Process Economics

Monoclonal antibodies currently dominate the biopharmaceutical market with growing sales having reached 80 billion USD in 2016. As most top-selling mAbs are approaching the end of their patent life, biopharmaceutical companies compete fiercely in the biosimilars market. These two factors present a strong motivation for alternative process strategies and process optimization. In this work a novel purification strategy for monoclonal antibodies comprising phenylboronic acid multimodal chromatography for capture followed by polishing by ion-exchange monolithic chromatography and packed bed hydrophobic interaction chromatography is presented and compared to the traditional protein-A-based process. Although the capital investment is similar for both processes, the operation cost is 20% lower for the novel strategy. This study shows that the new process is worthwhile investing in and could present a viable alternative to the platform process used by most industrial players.

Progress and biotechnological prospects in fish transgenesis

The history of transgenesis is marked by milestones such as the development of cellular transdifferentiation, recombinant DNA, genetic modification of target cells, and finally, the generation of simpler genetically modified organisms (e.g. bacteria and mice). The first transgenic fish was developed in 1984, and since then, continuing technological advancements to improve gene transfer have led to more rapid, accurate, and efficient generation of transgenic animals. Among the established methods are microinjection, electroporation, lipofection, viral vectors, and gene targeting. Here, we review the history of animal transgenesis, with an emphasis on fish, in conjunction with major developments in genetic engineering over the past few decades. Importantly, spermatogonial stem cell modification and transplantation are two common techniques capable of revolutionizing the generation of transgenic fish. Furthermore, we discuss recent progress and future biotechnological prospects of fish transgenesis, which has strong applications for the aquaculture industry. Indeed, some transgenic fish are already available in the current market, validating continued efforts to improve economically important species with biotechnological advancements.

PhiC31 integrase can improve the efficiency of different construct designs for monoclonal antibody expression in CHO cells

OBJECTIVES

Several types of expression vectors have been used for recombinant protein expression in Chinese hamster ovary cells (CHO) which usually result in variable and unstable levels of expression.

METHODS AND RESULTS

In this study, we have compared the mAb0014 expression level of single ORF/IRES vector and dual ORF vector in the presence and absence of phiC31 integrase targeting system. Both expression vectors contain an elongation factor 1α (EF1α) promoter upstream of LC and harboring an attB site. CHO-S cells were co-transfected with single ORF/IRES or dual ORF vectors along with a phiC31 integrase expression vector which can catalyze recombination between attB site and pseudo-attP sites presented in the mammalian genome. Our results demonstrated that dual ORF vector in the presence of phiC31 integrase expression vectors (+FC31 2P) generated more recombinant antibody in comparison to its negative control (-FC31 2P). Moreover, both of +FC31 2P and -FC31 2P cell pools yield higher recombinant protein in comparison to single ORF/IRES vector (FC31 IRES) cell pools. Stability of expression in phiC31 co-transfected cell pools (+FC31 2P and +FC31 IRES) had no considerable changes.

CONCLUSIONS

Our results indicated that the dual ORF vector using integrase can support the generation of cell lines with stable transgene expression at an elevated mAb relative to single ORF/IRES vector.

A novel in vitro assay to predict neonatal Fc receptor-mediated human IgG half-life

Immunoglobulin G (IgG) has an unusually long serum half-life in comparison to proteins of a similar size. It is well-known that this phenomenon is due to IgG's ability to bind the neonatal Fc receptor (FcRn) in a pH-dependent manner. FcRn binding properties can vary among IgGs, resulting in altered in vivo half-lives, and therefore it would be beneficial to accurately predict the FcRn binding properties of therapeutic IgG monoclonal antibodies (mAbs). Here we describe the development of an in vitro model capable of predicting the in vivo half-life of human IgG. Using a high-throughput biolayer interferometry (BLI) platform, the human FcRn association rate at acidic pH and subsequent dissociation rate at physiological pH was determined for 5 human IgG1 mAbs. Comparing the combined FcRn association and dissociation rates to the Phase 1 clinical study half-lives of the mAbs resulted in a strong correlation. The correlation was also verified in vivo using mice transgenic for human FcRn. The model was used to characterize various factors that may influence FcRn-mAb binding, including mAb variable region sequence differences and constant region glycosylation patterns. Results indicated that the complementarity-determining regions of the heavy chain significantly influence the mAb's FcRn binding properties, while the absence of glycosylation does not alter mAb-FcRn binding. Development of this high-throughput FcRn binding model could potentially predict the half-life of therapeutic IgGs and aid in selection of lead candidates while also serving as a screening tool for the development of mAbs with desired pharmacokinetic properties.

Biochemical Characterization of Human Anti-Hepatitis B Monoclonal Antibody Produced in the Microalgae Phaeodactylum tricornutum

Monoclonal antibodies (mAbs) represent actually the major class of biopharmaceuticals. They are produced recombinantly using living cells as biofactories. Among the different expression systems currently available, microalgae represent an emerging alternative which displays several biotechnological advantages. Indeed, microalgae are classified as generally recognized as safe organisms and can be grown easily in bioreactors with high growth rates similarly to CHO cells. Moreover, microalgae exhibit a phototrophic lifestyle involving low production costs as protein expression is fueled by photosynthesis. However, questions remain to be solved before any industrial production of algae-made biopharmaceuticals. Among them, protein heterogeneity as well as protein post-translational modifications need to be evaluated. Especially, N-glycosylation acquired by the secreted recombinant proteins is of major concern since most of the biopharmaceuticals including mAbs are N-glycosylated and it is well recognized that glycosylation represent one of their critical quality attribute. In this paper, we assess the quality of the first recombinant algae-made mAbs produced in the diatom, Phaeodactylum tricornutum. We are focusing on the characterization of their C- and N-terminal extremities, their signal peptide cleavage and their post-translational modifications including N-glycosylation macro- and microheterogeneity. This study brings understanding on diatom cellular biology, especially secretion and intracellular trafficking of proteins. Overall, it reinforces the positioning of P. tricornutum as an emerging host for the production of biopharmaceuticals and prove that P. tricornutum is suitable for producing recombinant proteins bearing high mannose-type N-glycans.

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.

Chemical and chemoenzymatic synthesis of glycoproteins for deciphering functions

Glycoproteins are an important class of biomolecules involved in a number of biological recognition processes. However, natural and recombinant glycoproteins are usually produced as mixtures of glycoforms that differ in the structures of the pendent glycans, which are difficult to separate in pure glycoforms. As a result, synthetic homogeneous glycopeptides and glycoproteins have become indispensable probes for detailed structural and functional studies. A number of elegant chemical and biological strategies have been developed for synthetic construction of tailor-made, full-size glycoproteins to address specific biological problems. In this review, we highlight recent advances in chemical and chemoenzymatic synthesis of homogeneous glycoproteins. Selected examples are given to demonstrate the applications of tailor-made, glycan-defined glycoproteins for deciphering glycosylation functions.

Cell factories for insulin production

The rapid increase in the number of diabetic patients globally and exploration of alternate insulin delivery methods such as inhalation or oral route that rely on higher doses, is bound to escalate the demand for recombinant insulin in near future. Current manufacturing technologies would be unable to meet the growing demand of affordable insulin due to limitation in production capacity and high production cost. Manufacturing of therapeutic recombinant proteins require an appropriate host organism with efficient machinery for posttranslational modifications and protein refolding. Recombinant human insulin has been produced predominantly using E. coli and Saccharomyces cerevisiae for therapeutic use in human. We would focus in this review, on various approaches that can be exploited to increase the production of a biologically active insulin and its analogues in E. coli and yeast. Transgenic plants are also very attractive expression system, which can be exploited to produce insulin in large quantities for therapeutic use in human. Plant-based expression system hold tremendous potential for high-capacity production of insulin in very cost-effective manner. Very high level of expression of biologically active proinsulin in seeds or leaves with long-term stability, offers a low-cost technology for both injectable as well as oral delivery of proinsulin.

Evaluation of antibody–chemokine fusion proteins for tumor-targeting applications

There is an increasing biotechnological interest in the ‘arming’ of therapeutic antibodies with bioactive payloads. While many antibody–cytokine fusion proteins have been extensively investigated in preclinical and clinical studies, there are only few reports related to antibody–chemokine fusion proteins (‘immunochemokines’). Here, we describe the cloning, expression, and characterization of 10 immunochemokines based on the monoclonal antibody F8, specific to the alternatively spliced extra domain A (EDA) of fibronectin, a marker of angiogenesis. Among the 10 murine chemokines tested in our study, only CCL19, CCL20, CCL21, and CXCL10 could be expressed and isolated at acceptable purity levels as F8-based fusion proteins. The immunochemokines retained the binding characteristics of the parental antibody, but could not be characterized by gel-filtration analysis, an analytical limitation which had previously been observed in our laboratory for the unconjugated chemokines. When radioiodinated preparations of CCL19-F8, CCL20-F8, CCL21-F8, and CXCL10-F8 were tested in quantitative biodistribution studies in tumor-bearing mice, the four fusion proteins failed to preferentially accumulate at the tumor site, while the unconjugated parental antibody displayed a tumor:blood ratio >20:1, 24 h after intravenous (i.v.) administration. The tumor-targeting ability of CCL19-F8 could be rescued only in part by preadministration of unlabeled CCL19-F8, indicating that a chemokine trapping mechanism may hinder pharmacodelivery strategies. While this article highlights expression, analytical, and biodistribution challenges associated with the antibody-based in vivo delivery of chemokines at sites of disease, it provides the first comprehensive report in this field and may facilitate future studies with immunochemokines.

Proteins improving recombinant antibody production in mammalian cells

Mammalian cells have been successfully used for the industrial manufacture of antibodies due to their ability to synthesize antibodies correctly. Nascent polypeptides must be subjected to protein folding and assembly in the ER and the Golgi to be secreted as mature proteins. If these reactions do not proceed appropriately, unfolded or misfolded proteins are degraded by the ER-associated degradation (ERAD) pathway. The accumulation of unfolded proteins or intracellular antibody crystals accompanied by this failure triggers the unfolded protein response (UPR), which can considerably attenuate the levels of translation, folding, assembly, and secretion, resulting in reduction of antibody productivity. Accumulating studies by omics-based analysis of recombinant mammalian cells suggest that not only protein secretion processes including protein folding and assembly but also translation are likely to be the rate-limiting factors for increasing antibody production. Here, this review describes the mechanism of antibody folding and assembly and recent advantages which could improve recombinant antibody production in mammalian cells by utilizing proteins such as ER chaperones or UPR-related proteins.

CHO microRNA engineering is growing up: recent successes and future challenges

microRNAs with their ability to regulate complex pathways that control cellular behavior and phenotype have been proposed as potential targets for cell engineering in the context of optimization of biopharmaceutical production cell lines, specifically of Chinese Hamster Ovary cells. However, until recently, research was limited by a lack of genomic sequence information on this industrially important cell line. With the publication of the genomic sequence and other relevant data sets for CHO cells since 2011, the doors have been opened for an improved understanding of CHO cell physiology and for the development of the necessary tools for novel engineering strategies. In the present review we discuss both knowledge on the regulatory mechanisms of microRNAs obtained from other biological models and proof of concepts already performed on CHO cells, thus providing an outlook of potential applications of microRNA engineering in production cell lines.

Complementary MS methods assist conformational characterization of antibodies with altered S-S bonding networks

As therapeutic monoclonal antibodies (mAbs) become a major focus in biotechnology and a source of the next-generation drugs, new analytical methods or combination methods are needed for monitoring changes in higher order structure and effects of post-translational modifications. The complexity of these molecules and their vulnerability to structural change provide a serious challenge. We describe here the use of complementary mass spectrometry methods that not only characterize mutant mAbs but also may provide a general framework for characterizing higher order structure of other protein therapeutics and biosimilars. To frame the challenge, we selected members of the IgG2 subclass that have distinct disulfide isomeric structures as a model to evaluate an overall approach that uses ion mobility, top-down MS sequencing, and protein footprinting in the form of fast photochemical oxidation of proteins (FPOP). These three methods are rapid, sensitive, respond to subtle changes in conformation of Cys → Ser mutants of an IgG2, each representing a single disulfide isoform, and may be used in series to probe higher order structure. The outcome suggests that this approach of using various methods in combination can assist the development and quality control of protein therapeutics.

Structure-based redesign of proteins for minimal T-cell epitope content

The protein universe displays a wealth of therapeutically relevant activities, but T-cell driven immune responses to non-"self" biological agents present a major impediment to harnessing the full diversity of these molecular functions. Mutagenic T-cell epitope deletion seeks to mitigate the immune response, but can typically address only a small number of epitopes. Here, we pursue a "bottom-up" approach that redesigns an entire protein to remain native-like but contain few if any immunogenic epitopes. We do so by extending the Rosetta flexible-backbone protein design software with an epitope scoring mechanism and appropriate constraints. The method is benchmarked with a diverse panel of proteins and applied to three targets of therapeutic interest. We show that the deimmunized designs indeed have minimal predicted epitope content and are native-like in terms of various quality measures, and moreover that they display levels of native sequence recovery comparable to those of non-deimmunized designs.

CHO cell engineering to prevent polypeptide aggregation and improve therapeutic protein secretion

The ability to efficiently produce recombinant proteins in a secreted form is highly desirable and cultured mammalian cells such as CHO cells have become the preferred host as they secrete proteins with human-like post-translational modifications. However, attempts to express high levels of particular proteins in CHO cells may consistently result in low yields, even for non-engineered proteins such as immunoglobulins. In this study, we identified the responsible faulty step at the stage of translational arrest, translocation and early processing for such a "difficult-to-express" immunoglobulin, resulting in improper cleavage of the light chain and its precipitation in an insoluble cellular fraction unable to contribute to immunoglobulin assembly. We further show that proper processing and secretion were restored by over-expressing human signal receptor protein SRP14 and other components of the secretion pathway. This allowed the expression of the difficult-to-express protein to high yields, and it also increased the production of an easy-to-express protein. Our results demonstrate that components of the secretory and processing pathways can be limiting, and that engineering of the secretory pathway may be used to improve the secretion efficiency of therapeutic proteins from CHO cells.

Analysis of the landscape of biologically-derived pharmaceuticals in Europe: dominant production systems, molecule types on the rise and approval trends

A thorough sort of the human drugs approved by the European Medicines Agency (EMA) between its establishment in 1995 until June 2012 is presented herein with a focus on biologically-derived pharmaceuticals. Over 200 (33%) of the 640 approved therapeutic drugs are derived from natural sources, produced via recombinant DNA technology, or generated through virus propagation. A breakdown based on production method, type of molecule and therapeutic category is presented. Current EMA approvals demonstrate that mammalian cells are the only choice for glycoprotein drugs, with Chinese hamster ovary cells being the dominant hosts for their production. On the other hand, bacterial cells and specifically Escherichia coli are the dominant hosts for protein-based drugs, followed by the yeast Saccharomyces cerevisiae. The latter is the dominant host for recombinant vaccine production, although egg-based production is still the main platform of vaccine provision. Our findings suggest that the majority of biologically-derived drugs are prescribed for cancer and related conditions, as well as the treatment of diabetes. The approval rate for biologically-derived drugs shows a strong upward trend for monoclonal antibodies and fusion proteins since 2009, while hormones, antibodies and growth factors remain the most populous categories. Despite a clear pathway for the approval of biosimilars set by the EMA and their potential to drive sales growth, we have only found approved biosimilars for three molecules. In 2012 there appears to be a slow-down in approvals, which coincides with a reported decline in the growth rate of biologics sales.

Biosimilars: company strategies to capture value from the biologics market

Patents for several biologic blockbusters will expire in the next few years. The arrival of biosimilars, the biologic equivalent of chemical generics, will have an impact on the current biopharmaceuticals market. Five core capabilities have been identified as paramount for those companies aiming to enter the biosimilars market: research and development, manufacturing, supporting activities, marketing, and lobbying. Understanding the importance of each of these capabilities will be key to maximising the value generated from the biologics patent cliff.

Production of biopharmaceutical proteins by yeast: advances through metabolic engineering

Production of recombinant proteins for use as pharmaceuticals, so-called biopharmaceuticals, is a multi-billion dollar industry. Many different cell factories are used for the production of biopharmaceuticals, but the yeast Saccharomyces cerevisiae is an important cell factory as it is used for production of several large volume products. Insulin and insulin analogs are by far the dominating biopharmaceuticals produced by yeast, and this will increase as the global insulin market is expected to grow from USD12B in 2011 to more than USD32B by 2018. Other important biopharmaceuticals produced by yeast are human serum albumin, hepatitis vaccines and virus like particles used for vaccination against human papillomavirus. Here is given a brief overview of biopharmaceutical production by yeast and it is discussed how the secretory pathway can be engineered to ensure more efficient protein production. The involvement of directed metabolic engineering through the integration of tools from genetic engineering, systems biology and mathematical modeling, is also discussed.

Effect of diabetes mellitus on pharmacokinetic and pharmacodynamic properties of drugs

The effects of diabetes mellitus on the pharmacokinetics and pharmacodynamics of drugs have been well described in experimental animal models; however, only minimal data exist for humans and the current knowledge regarding the effects of diabetes on these properties remains unclear. Nevertheless, it has been observed that the pharmacokinetics and pharmacodynamics of drugs are changed in subjects with diabetes. It has been reported that diabetes may affect the pharmacokinetics of various drugs by affecting (i) absorption, due to changes in subcutaneous adipose blood flow, muscle blood flow and gastric emptying; (ii) distribution, due to non-enzymatic glycation of albumin; (iii) biotransformation, due to regulation of enzymes/transporters involved in drug biotransformation; and (iv) excretion, due to nephropathy. Previously published data also suggest that diabetes-mediated changes in the pharmacokinetics of a particular drug cannot be translated to others. Although clinical studies exploring the effect of diabetes on pharmacodynamics are still very limited, there is evidence that disease-mediated effects are not limited only to pharmacokinetics but also alter pharmacodynamics. However, for many drugs it remains unclear whether these influences reflect diabetes-mediated changes in pharmacokinetics rather than pharmacodynamics. In addition, even though diabetes-mediated pharmacokinetics and pharmacodynamics might be anticipated, it is important to study the effect on each drug and not generalize from observed data. The available data indicate that there is a significant variability in drug response in diabetic subjects. The discrepancies between individual clinical studies as well as between ex vivo and clinical studies are probably due to (i) the restricted and focused population of subjects in clinical studies; (ii) failure to consider type, severity and duration of the disease; (iii) histopathological characteristics generally being missing; and (iv) other factors such as varying medication use, dietary protein intake, age, sex and obesity. The obesity epidemic in the developed world has also inadvertently influenced the directions of pharmacological research. This review attempts to map new information gained since Gwilt published his paper in Clinical Pharmacokinetics in 1991. Although a large body of research has been conducted and significant progress has been made, we still have to conclude that the available information regarding the effect of diabetes on pharmacokinetics and pharmacodynamics remains unclear and further clinical studies are required before we can understand the clinical significance of the effect. An understanding of diabetes-mediated changes as well as of the source of the variability should lead to the improvement of the medical management and clinical outcomes in patients with this widespread disease.

Recent advances in technology supporting biopharmaceutical production from mammalian cells

The demand for production of glycoproteins from mammalian cell culture continues with an increased number of approvals as biopharmaceuticals for the treatment of unmet medical needs. This is particularly the case for humanized monoclonal antibodies which are the largest and fastest growing class of therapeutic pharmaceuticals. This demand has fostered efforts to improve the efficiency of production as well as to address the quality of the final product. Chinese hamster ovary cells are the predominant hosts for stable transfection and high efficiency production on a large scale. Specific productivity of recombinant glycoproteins from these cells can be expected to be above 50 pg/cell/day giving rise to culture systems with titers of around 5 g/L if appropriate fed-batch systems are employed. Cell engineering can delay the onset of programmed cell death to ensure prolonged maintenance of productive viable cells. The clinical efficacy and quality of the final product can be improved by strategic metabolic engineering. The best example of this is the targeted production of afucosylated antibodies with enhanced antibody-dependent cell cytotoxicity, an important function for use in cancer therapies. The development of culture media from non-animal sources continues and is important to ensure products of consistent quality and without the potential danger of contamination. Process efficiencies may also be improved by employing disposable bioreactors with the associated minimization of downtime. Finally, advances in downstream processing are needed to handle the increased supply of product from the bioreactor but maintaining the high purity demanded of these biopharmaceuticals.

A survey of applications of biological products for drug interference of immunogenicity assays

PURPOSE

Biological drugs in circulation can interfere with anti-drug antibody (ADA) assays and cause false ADA negatives. We surveyed the applications of biological products approved by FDA during 2005-2011 for prevalence of drug interferences and proposed approaches to address this issue scientifically.

METHODS

The immunogenicity assay drug tolerance, steady-state drug concentrations, and immunogenicity rates were reviewed for 26 BLA/NDA and 2 sBLA.

RESULTS

Many FDA approved biologics had higher steady-state drug concentrations than the drug tolerance of ADA assays, by 1.2- to 800-fold. Reported immunogenicity rates may be negatively impacted. Some sponsors triaged immunogenicity samples according to the drug tolerance, leaving some samples un-assayed or reporting them as inconclusive ADA; but these samples were interpreted as ADA- for calculating immunogenicity rates.

CONCLUSIONS

Implementation of ADA assays that can tolerate therapeutic drug concentrations is imperative. Given drug interferences, we propose in this paper the following practices: (i) to measure drug concentrations in ADA samples, (ii) to explicitly list all ADA status, including inconclusive ADA and un-assayed samples, (iii) to calculate population immunogenicity rates based on only subjects with confirmed ADA+ and ADA-, and (iv) to make available ADA assay specifics relevant to the use of ADA data in disease management.

Design and analysis of immune-evading enzymes for ADEPT therapy

The unparalleled specificity and activity of therapeutic proteins has reshaped many aspects of modern clinical practice, and aggressive development of new protein drugs promises a continued revolution in disease therapy. As a result of their biological origins, however, therapeutic proteins present unique design challenges for the biomolecular engineer. For example, protein drugs are subject to immune surveillance within the patient's body; this anti-drug immune response can compromise therapeutic efficacy and even threaten patient safety. Thus, there is a growing demand for broadly applicable protein deimmunization strategies. We have recently developed optimization algorithms that integrate computational prediction of T-cell epitopes and bioinformatics-based assessment of the structural and functional consequences of epitope-deleting mutations. Here, we describe the first experimental validation of our deimmunization algorithms using Enterobacter cloacae P99 β-lactamase, a component of antibody-directed enzyme prodrug cancer therapies. Compared with wild-type or a previously deimmunized variant, our computationally optimized sequences exhibited significantly less in vitro binding to human type II major histocompatibility complex immune molecules. At the same time, our globally optimal design exhibited wild-type catalytic proficiency. We conclude that our deimmunization algorithms guide the protein engineer towards promising immunoevasive candidates and thereby have the potential to streamline biotherapeutic development.

Glyco-engineering in plants to produce human-like N-glycan structures

It is now possible to produce complex human proteins, largely correctly folded and N-glycosylated, in plants. Much effort has been invested in engineering expression technologies to develop products with superior characteristics. The results have begun to show success in controlling important posttranslational modifications such as N-glycosylation. With the emerging data increasingly indicating the significance of proper N-glycosylation for the efficacy of a drug, glyco-engineering has become an important issue not only for academia but also for the biopharmaceutical industry. Plants have demonstrated a high degree of tolerance to changes in the N-glycosylation pathway, allowing recombinant proteins to be modified into human-like structures in a specific and controlled manner. Frequently the results are a largely homogeneously glycosylated product, currently unrivalled by that of any other expression platforms. This review provides a comprehensive analysis of recent advances in plant N-glyco-engineering in the context of the expression of therapeutically relevant proteins, highlighting both the challenges and successes in the application of such powerful technologies.

Chemoenzymatic glycoengineering of intact IgG antibodies for gain of functions

The fine structures of Fc N-glycans can modulate the effector functions of IgG antibodies. It has been demonstrated that lack of the core fucose on the Fc N-glycans leads to drastic enhancement of antibody-dependent cellular cytotoxicity (ADCC), while terminal α2,6-sialylation of Fc glycan plays a critical role for the anti-inflammatory activity of human intravenous immunoglobulin (IVIG). We describe in this paper a highly efficient chemoenzymatic method for site-selective Fc glycoengineering of intact monoclonal antibody and IVIG. Two new glycosynthase mutants (EndoS-D233A and D233Q) were generated by site-directed mutagenesis of EndoS (an endoglycosidase from Streptococcus pyogenes ) and were found to be capable of efficiently transferring predefined N-glycans from corresponding glycan oxazolines to the Fc-deglycosylated intact IgGs without product hydrolysis. As a model study, rituximab (a therapeutic monoclonal antibody) was successfully transformed from mixtures of G0F, G1F, and G2F glycoforms to well-defined homogeneous glycoforms, including a fully sialylated (S2G2F) glycoform that may gain anti-inflammatory activity, a nonfucosylated G2 glycoform that showed significantly enhanced FcγIIIa receptor-binding activity, and an azido-tagged glycoform that can be further transformed into other glycoforms. We also found that EndoS could selectively remove the Fc N-glycans in the presence of FAB glycosylation. This finding, coupled with the remarkable transglycosylation activity of the EndoS glycosynthase mutants, permitted a highly selective glycoengineering of the IVIG's Fc glycans into a fully sialylated Fc glycoform, which may possess significantly enhanced anti-inflammatory activity. The glycoengineering approach described here provides a general platform to modulate the effector functions of IgG antibodies, enabling the optimization of therapeutic efficacy and gain of new functions of monoclonal antibodies and IVIG.

LC-MS-based metabolic characterization of high monoclonal antibody-producing Chinese hamster ovary cells

The selection of suitable mammalian cell lines with high specific productivities is a crucial aspect of large-scale recombinant protein production. This study utilizes a metabolomics approach to elucidate the key characteristics of Chinese hamster ovary (CHO) cells with high monoclonal antibody productivities (q(mAb)). Liquid chromatography-mass spectrometry (LC-MS)-based intracellular metabolite profiles of eight single cell clones with high and low q(mAb) were obtained at the mid-exponential phase during shake flask batch cultures. Orthogonal projection to latent structures discriminant analysis (OPLS-DA) subsequently revealed key differences between the high and low q(mAb) clones, as indicated by the variable importance for projection (VIP) scores. The mass peaks were further examined for their potential association with q(mAb) across all clones using Pearson's correlation analysis. Lastly, the identities of metabolites with high VIP and correlation scores were confirmed by comparison with standards through LC-MS-MS. A total of seven metabolites were identified-NADH, FAD, reduced and oxidized glutathione, and three activated sugar precursors. These metabolites are involved in key cellular pathways of citric acid cycle, oxidative phosphorylation, glutathione metabolism, and protein glycosylation. To our knowledge, this is the first study to identify metabolites that are associated closely with q(mAb). The results suggest that the high producers had elevated levels of specific metabolites to better regulate their redox status. This is likely to facilitate the generation of energy and activated sugar precursors to meet the demands of producing more glycosylated recombinant monoclonal antibodies.

Protein particulate detection issues in biotherapeutics development--current status

Formation of aggregates and particulates in biopharmaceutical formulation continues to be one of the major quality concerns in biotherapeutics development. The presence of large quantities of aggregates is believed to be one of the causes of unwanted immunogenic responses. Protein particulates can form in a wide range of sizes and shapes. Therefore, a comprehensive characterization of particulates in biologics formulation continues to be challenging. The quantity of small size aggregates (e.g., dimer) in a stable biologics formulation is well controlled using precision analytical techniques (e.g., high-performance liquid chromatography). Particulate in clinical and commercial formulations is monitored using visual inspection and subvisible particulate counting assays. While visual inspection (by human eye or automated systems) is intended to detect particulates (intrinsic and extrinsic) of ~100 μm or larger, the subvisible counting methods cover smaller size ranges down to 10 μm. It is well recognized that research of particulates in the submicron (<1 μm) and low-micron (1-10 μm) ranges may provide important clues to understand the mechanism of particulate formation. The recent years have seen a significant increase in the development of newer technologies for more comprehensive characterization of particulates. This is attributed to increased awareness in this field of research over the past 5 years, stimulated by scholarly articles, commentaries, and robust discussions in various forums. This article provides an overview of emerging detection technologies that provide complementary characterization data encompassing a wider size range of particulates. It also discusses their advantages and limitations in the context of applications in biotherapeutics development.

Pharmaceutical protein production by yeast: towards production of human blood proteins by microbial fermentation

Since the approval of recombinant insulin from Escherichia coli for its clinical use in the early 1980s, the amount of recombinant pharmaceutical proteins obtained by microbial fermentations has significantly increased. The recent advances in genomics together with high throughput analysis techniques (the so-called-omics approaches) and integrative approaches (systems biology) allow the development of novel microbial cell factories as valuable platforms for large scale production of therapeutic proteins. This review summarizes the main achievements and the current situation in the field of recombinant therapeutics using yeast Saccharomyces cerevisiae as a model platform, and discusses the future potential of this platform for production of blood proteins and substitutes.

ADME of biologics-what have we learned from small molecules?

Thorough characterization and in-depth understanding of absorption, distribution, metabolism, and elimination (ADME) properties of a drug candidate have been well recognized as an important element in small molecule (SM) drug discovery and development. This has been the area of focus for drug metabolism and pharmacokinetics (DMPK) scientists, whose role has been evolving over the past few decades from primarily being involved in the development space after a preclinical candidate was selected to extending their involvement into the discovery stage prior to candidate selection. This paradigm shift has ensured the entry into development of the best candidates with optimal ADME properties, and thus has greatly impacted SM drug development through significant reduction of the failure rate for pharmacokinetics related reasons. In contrast, the sciences of ADME and DMPK have not been fully integrated into the discovery and development processes for large molecule (LM) drugs. In this mini-review, we reflect on the journey of DMPK support of SM drug discovery and development and highlight the key enablers that have allowed DMPK scientists to make such impacts, with the aim to provide a perspective on relevant lessons learned from SM drugs that are applicable to DMPK support strategies for LMs.