Strategies for Setting Patient-Centric Commercial Specifications for Biotherapeutic Products

Commercial specifications for a new biotherapeutic product are a critical component of the product's overall control strategy that ensures safety and efficacy. This paper describes strategies for setting commercial specifications as proposed by a consortium of industry development scientists. The specifications for some attributes are guided by compendia and regulatory guidance. For other product quality attributes (PQAs), product knowledge and the understanding of attribute criticality built throughout product development should drive specification setting. The foundation of PQA knowledge is an understanding of potential patient impact through an assessment of potency, PK, immunogenicity and safety. In addition to PQA knowledge, the ability of the manufacturing process to consistently meet specifications, typically assessed through statistical analyses, is an important consideration in the specification-setting process. Setting acceptance criteria that are unnecessarily narrow can impact the ability to supply product or prohibit consideration of future convenient dosage forms. Patient-centric specifications enable appropriate control over higher risk PQAs to ensure product quality for the patient, and flexibility for lower risk PQAs for a sustainable supply chain. This paper captures common strategic approaches for setting specifications for standard biotherapeutic products such as monoclonal antibodies and includes considerations for ensuring specifications are patient centric.

NIST Interlaboratory Study on Glycosylation Analysis of Monoclonal Antibodies: Comparison of Results from Diverse Analytical Methods

Glycosylation is a topic of intense current interest in the development of biopharmaceuticals because it is related to drug safety and efficacy. This work describes results of an interlaboratory study on the glycosylation of the Primary Sample (PS) of NISTmAb, a monoclonal antibody reference material. Seventy-six laboratories from industry, university, research, government, and hospital sectors in Europe, North America, Asia, and Australia submitted a total of 103 reports on glycan distributions. The principal objective of this study was to report and compare results for the full range of analytical methods presently used in the glycosylation analysis of mAbs. Therefore, participation was unrestricted, with laboratories choosing their own measurement techniques. Protein glycosylation was determined in various ways, including at the level of intact mAb, protein fragments, glycopeptides, or released glycans, using a wide variety of methods for derivatization, separation, identification, and quantification. Consequently, the diversity of results was enormous, with the number of glycan compositions identified by each laboratory ranging from 4 to 48. In total, one hundred sixteen glycan compositions were reported, of which 57 compositions could be assigned consensus abundance values. These consensus medians provide community-derived values for NISTmAb PS. Agreement with the consensus medians did not depend on the specific method or laboratory type. The study provides a view of the current state-of-the-art for biologic glycosylation measurement and suggests a clear need for harmonization of glycosylation analysis methods.

Galactosyltransferase 4 is a major control point for glycan branching in N-linked glycosylation

Protein N-glycosylation is a common post-translational modification that produces a complex array of branched glycan structures. The levels of branching, or antennarity, give rise to differential biological activities for single glycoproteins. However, the precise mechanism controlling the glycan branching and glycosylation network is unknown. Here, we constructed quantitative mathematical models of N-linked glycosylation that predicted new control points for glycan branching. Galactosyltransferase, which acts on N-acetylglucosamine residues, was unexpectedly found to control metabolic flux through the glycosylation pathway and the level of final antennarity of nascent protein produced in the Golgi network. To further investigate the biological consequences of glycan branching in nascent proteins, we glycoengineered a series of mammalian cells overexpressing human chorionic gonadotropin (hCG). We identified a mechanism in which galactosyltransferase 4 isoform regulated N-glycan branching on the nascent protein, subsequently controlling biological activity in an in vivo model of hCG activity. We found that galactosyltransferase 4 is a major control point for glycan branching decisions taken in the Golgi of the cell, which might ultimately control the biological activity of nascent glycoprotein.

Synergizing metabolic flux analysis and nucleotide sugar metabolism to understand the control of glycosylation of recombinant protein in CHO cells

BACKGROUND

The glycosylation of recombinant proteins can be altered by a range of parameters including cellular metabolism, metabolic flux and the efficiency of the glycosylation process. We present an experimental set-up that allows determination of these key processes associated with the control of N-linked glycosylation of recombinant proteins.

RESULTS

Chinese hamster ovary cells (CHO) were cultivated in shake flasks at 0 mM glutamine and displayed a reduced growth rate, glucose metabolism and a slower decrease in pH, when compared to other glutamine-supplemented cultures. The N-linked glycosylation of recombinant human chorionic gonadotrophin (HCG) was also altered under these conditions; the sialylation, fucosylation and antennarity decreased, while the proportion of neutral structures increased. A continuous culture set-up was subsequently used to understand the control of HCG glycosylation in the presence of varied glutamine concentrations; when glycolytic flux was reduced in the absence of glutamine, the glycosylation changes that were observed in shake flask culture were similarly detected. The intracellular content of UDP-GlcNAc was also reduced, which correlated with a decrease in sialylation and antennarity of the N-linked glycans attached to HCG.

CONCLUSIONS

The use of metabolic flux analysis illustrated a case of steady state multiplicity, where use of the same operating conditions at each steady state resulted in altered flux through glycolysis and the TCA cycle. This study clearly demonstrated that the control of glycoprotein microheterogeneity may be examined by use of a continuous culture system, metabolic flux analysis and assay of intracellular nucleotides. This system advances our knowledge of the relationship between metabolic flux and the glycosylation of biotherapeutics in CHO cells and will be of benefit to the bioprocessing industry.

Carbohydrate analysis of bacterial polysaccharides by high-pH anion-exchange chromatography and online polarimetric determination of absolute configuration

A significant problem in structure determination of complex carbohydrates, especially for bacterial polysaccharides, is determination of the absolute configuration of the component monosaccharides. A number of analytical methods have been used for this purpose but, as a result of the wide variety of chemical properties of sugars found in complex polysaccharides, no single method is universally applicable. High-resolution gas chromatography of volatile derivatives with chiral reagents is the most widely used method. Optical activity, although direct and simple, lacks sensitivity generally requiring a large quantity of pure monosaccharide. We report a combination of high-performance anion-exchange chromatography (HPAEC) with combined electrochemical pulsed amperometric detection and in-line detection of optical rotation with an in-line laser polarimeter for analysis of a number of sugars found in complex polysaccharides. We show that application of the method for analysis of capsular polysaccharides of several gram-positive and gram-negative pathogenic bacteria provides useful information simultaneously on carbohydrate composition and the enantiomeric configuration of component sugars.

Structural analysis and chemical depolymerization of the capsular polysaccharide of Streptococcus pneumoniae type 1

NMR spectroscopy can be used to characterize bacterial polysaccharides such as that of Streptococcus pneumoniae type 1 which is a component of the 23-valent pneumococcal vaccine in clinical use. This particular polysaccharide gives NMR spectra with wide lines apparently due to restricted molecular mobility and chain flexibility which leads to rapid dipolar T(2) relaxation limiting the possibility of detailed spectral analysis. Removal of O-acetyl groups found on approximately two thirds of the repeating subunits of pneumococcal type 1 capsule leads to narrower NMR lines facilitating a complete assignment of the 1H and 13C NMR spectra. Degradation of the polysaccharide by periodate oxidation followed by base treatment leads to an oligosaccharide fragment of approximately three repeating trisaccharide units. This oligosaccharide has narrow NMR lines and 1H and 13C assignments very similar to those of the O-deacetylated polysaccharide. In the native polysaccharide, O-acetyl groups are located on the 2- and 3-positions of the 4-linked galacturonic acid residue providing protection against periodate oxidation. Analysis of NOESY spectra combined with molecular modeling of the oligosaccharide shows that flexibility occurs in certain of the saccharide linkages.