The presence of protein aggregates is commonly believed to be an important risk factor for immunogenicity of therapeutic proteins. Among all types of aggregates, dimers are relatively abundant in most commercialized monoclonal antibody (mAb) products. The aim of this study was to investigate the immunogenicity of artificially created mAb dimers relative to that of unstressed and stressed mAb monomers. A monoclonal murine IgG1 (mIgG1) antibody was exposed to low pH, elevated temperature, or UV irradiation to induce dimerization. Dimers and monomers were purified via size-exclusion chromatography. Physicochemical analysis revealed that upon all stress conditions, new deamidation or oxidation or both of amino acids occurred. Nevertheless, the secondary and tertiary structures of all obtained dimers were similar to those of unstressed mIgG1. Isolated dimers were administered subcutaneously in Balb/c mice, and development of antidrug antibodies and accumulation of follicular T helper cells in draining lymph nodes and spleens were determined. None of the tested dimers or stressed monomers were found to be more immunogenic than the unstressed control in our mouse model. In conclusion, both dimers and monomers generated by using 3 different stress factors have a low immunogenicity similar to that of the unstressed monomers.

Protein aggregates are one of the several risk factors for undesired immunogenicity of biopharmaceuticals. However, it remains unclear which features determine whether aggregates will trigger an unwanted immune response. The aim of this study was to determine the effect of aggregates' size on their relative immunogenicity. A monoclonal murine IgG1 was stressed by exposure to low pH and elevated temperature followed by stirring to obtain aggregates widely differing in size. Aggregate fractions enriched in soluble oligomers, submicron size particles and micron size particles were isolated via centrifugation or size-exclusion chromatography and characterized physicochemically. The secondary and tertiary structures of aggregates were altered in a similar way for all the fractions, while no substantial chemical degradation was observed. Development of anti-drug antibodies was measured after subcutaneous administration of each enriched fraction to BALB/c mice. Among all tested fractions, the most immunogenic was the one highly enriched in submicron size particles (∼100-1000 nm). Fractions composed of micron size (>1-100 μm) particles or soluble oligomers (<100 nm) were not immunogenic under the dosing regimen studied in this work. These results show that aggregate size is an important factor for protein immunogenicity.

We propose a method for determining the criticality of residual host cell DNA, which is characterized through two attributes, namely the size and amount of residual DNA in biopharmaceutical product. By applying a mechanistic modeling approach to the problem, we establish the linkage between residual DNA and product safety measured in terms of immunogenicity, oncogenicity, and infectivity. Such a link makes it possible to establish acceptable ranges of residual DNA size and amount. Application of the method is illustrated through two real-life examples related to a vaccine manufactured in Madin Darby Canine Kidney cell line and a monoclonal antibody using Chinese hamster ovary (CHO) cell line as host cells.

Detailed monoclonal antibody (mAb) characterization tools have enabled the discovery of structural variations, including many that compromise functionality or have other undesired properties. Size, charge, glycosylation, and disulfide bonding variants; oxidized amino acid residues; and polypeptide chain truncations, extensions, and cleavage points have been identified. Product quality attributes, including detection techniques, published knowledge about the process origins, and quality impacts of these variants are summarized.

In recent years both the mechanism and applications of metal-enhanced fluorescence (MEF) have attracted significant attention, yet many fundamental aspects of MEF remain unanswered or addressed. In this study, we address a fundamental aspect of MEF. Using fluorescein-labeled different length DNA scaffolds, covalently bound to silver nanodeposits, we have experimentally measured the distance dependence of the MEF effect. The enhanced fluorescence signatures, i.e., MEF, follow quite closely the theoretical decay of the near-field of the nanoparticles, calculated using finite difference time domain approaches. This implies that the mechanisms of MEF are partially underpinned by the magnitude and distribution of the electric field around near-field nanoparticles.

Parallelism is a prerequisite for the determination of relative potency in bioactivity assays. It involves the testing of similarity between a pair of dose-response curves of reference standard and test sample. The evaluation of parallelism is a requirement listed by both the United States Pharmacopeia (USP) and European Pharmacopeia (EP). The revised USP Chapters 〈1032〉 and 〈1034〉 suggest testing parallelism using an equivalence method. However, implementation of this method can be challenging for laboratories that lack experience in statistical analysis and software development. In this paper we present a customized assay analysis template that is developed based on a fully good manufacturing practice (GMP)-compliant software package. The template allows for automation of the USP-recommended equivalence parallelism testing method for 4PLmodel in bioassays. It makes the implementation of the USP guidance both practical and feasible. Use of the analysis template is illustrated through a practical example.LAY ABSTRACT:Parallelism is a prerequisite for the determination of relative potency in bioactivity assays. It involves the testing of similarity between a pair of dose-response curves of reference standard and test sample. The evaluation of parallelism is a requirement listed by both the United States Pharmacopeia (USP) and European Pharmacopeia (EP). The revised USP Chapters 〈1032〉 and 〈1034〉 suggest testing parallelism using an equivalence method. However, implementation of this method can be challenging for laboratories that lack experience in statistical analysis and software development. In this paper we present a customized assay analysis template that is developed based on a fully good manufacturing practice (GMP)-compliant software package. The template allows for automation of the USP-recommended equivalence parallelism testing method for 4-parameter logistic model in bioassays. It makes the implementation of the USP guidance both practical and feasible. Use of the analysis template is illustrated through a practical example.

A method using a combination of asymmetric flow field-flow fractionation (AFFFF) and multiangle light scattering (MALS) techniques has been shown to improve the estimation of virus particle counts and the amount of aggregated virus in laboratory samples. The method is based on the spherical particle counting approach given by Wyatt and Weida in 2004, with additional modifications. The new method was tested by analyzing polystyrene beads and adenovirus samples, both having a well-characterized particle size and concentration. Influenza virus samples were analyzed by the new AFFFF-MALS technique, and particle size and aggregate state were compared with results from atomic force microscopy analysis. The limitations and source of possible errors for the new AFFFF-MALS analysis are discussed.

level: interMediate C osponsored by CASSS (an International Separation Science Society) and the US FDA, the 17th CMC Strategy Forum was designed to explore the relationships between higher-order molecular structure and quality of therapeutic proteins and peptides, vaccines, and blood-derived products. Understanding those relationships is important to defining and controlling the critical quality attributes (CQAs) of biopharmaceutical products. The forum program highlighted the current state of the art for analytical tools used to monitor higher-order structure. Case studies demonstrating the effects of changes to higher-order structure on biological function illustrated approaches to defining correlations. Presentations by experts from regulatory agencies, academia, and industry were followed by discussions focused on correlating data derived from analytical tools to biological functions of molecules. A predefined set of questions helped focus the discussions (see “Structure of the Forum”).

The Fc (crystallizable fragment) region of therapeutic antibodies can have an important role in their safety and efficacy. Although much is known about the structure-activity relationship of antibodies and the factors that influence Fc effector functions, a process has not yet been defined to clearly delineate how Fc functionality should be assessed and controlled during antibody development and manufacturing. In this article, we summarize the current knowledge of antibody Fc functionality, provide a strategy for assessing the effector functions of different classes of therapeutic antibodies (including Fc fusion proteins) and propose a path for routine testing and controls for manufacturers of antibody products.

This report describes the development of a potency ELISA using a peptide derived from the motavizumab binding epitope of respiratory syncytial virus (RSV) F-protein. Motavizumab is an antibody therapeutic studied for the prevention of RSV disease. It binds to the RSV glycoprotein F (F-protein), blocking the ability of RSV to fuse with target cells. This binding is the basis for a potency ELISA, however, due to inefficient F-protein production, development of an alternative ligand for the potency ELISA was investigated. A series of synthetic peptides spanning the motavizumab epitope on F-protein were evaluated for motavizumab binding activity. A 26-mer peptide was identified with desirable motavizumab binding kinetics, as shown by ELISA and surface plasmon resonance. The peptide corresponds to a portion of the motavizumab binding domain on the F-protein, and is referred to as F-peptide. The binding of motavizumab to the F-peptide is used in a new motavizumab potency ELISA, which was shown to be robust and statistically comparable to the F-protein ELISA. In addition, based on a qualitative observation, this new ELISA may be able to detect motavizumab degradation with greater sensitivity compared to the F-protein ELISA.

The International Conference on Harmonization (ICH) Q8(R2), Q9, and Q10 guidelines provide the foundation for implementing Quality by Design (QbD). Applying those concepts to the manufacture of biotech products, however, involves some nuances and complexities. Therefore, this paper offers guidance and interpretation for implementing QbD for biopharmaceuticals, from early-phase development steps such as identifying critical quality attributes and setting specifications, followed by the development of the design space and establishing the process control strategy; to later stages, including incorporating QbD into a regulatory filing and facilitating efficient commercial processes and manufacturing change flexibility post licensure.

T he first CMC Strategy Forum that focused on quality by design (QbD) was held in July 2007, and it helped establish a general understanding of the various aspects of QbD. Topics discussed included the process for developing a design space for cell culture and purification of a biopharmaceutical product, strategies for filing the design space with regulatory authorities, and potential regulatory hurdles of using QbD data. Continuing with the success of that first QbD forum, the second in July 2008 was designed to provide a venue to discuss progress made by the biopharmaceutical industry in development of QbD concepts and to present updates from regulatory agencies regarding how they propose to review and approve QbD filings. Case studies were provided by biopharmaceutical companies on the development of design space, PAT applications, comparability protocols, and the proposed use of QbD for routine manufacturing. Regulatory agencies likewise described how they have been approaching QbD filings and potential avenues to regulatory relief for the sponsors. In addition, open forums were held to discuss and obtain consensus on the following issues: • Based on companies’ design space studies, how have validation studies been conducted? • How have design space data been implemented into process ranges for routine manufacturing? • Do biopharmaceutical companies see a path for regulatory relief based on design space data? Has QbD been a worthwhile effort? • Have regulatory agencies made further progress in formalizing their review of QbD data? Those and other relevant questions were discussed at the 2008 interactive forum, 16–17 July 2008 in Bethesda, MD. This forum was divided into four workshop sessions, each involving two to four presentations followed by an interactive discussion with a panel and moderator as well as questions and comments from the audience.

Adequate biophysical characterization of influenza virions is important for vaccine development. The influenza virus vaccines are produced from the allantoic fluid of developing chicken embryos. The process of viral replication produces a heterogeneous mixture of infectious and non-infectious viral particles with varying states of aggregation. The study of the relative distribution and behavior of different subpopulations and their inter-correlation can assist in the development of a robust process for a live virus vaccine. This report describes a field flow fractionation and multiangle light scattering (FFF-MALS) method optimized for the analysis of size distribution and total particle counts. The FFF-MALS method was compared with several other methods such as transmission electron microscopy (TEM), atomic force microscopy (AFM), size exclusion chromatography followed by MALS (SEC-MALS), quantitative reverse transcription polymerase chain reaction (RT Q-PCR), median tissue culture dose (TCID(50)), and the fluorescent focus assay (FFA). The correlation between the various methods for determining total particle counts, infectivity and size distribution is reported. The pros and cons of each of the analytical methods are discussed.

We have identified a single tryptophan (Trp) residue responsible for loss of binding and biological activity upon ultraviolet (UV) light irradiation in MEDI-493, a humanized monoclonal antibody (MAb) against respiratory syncytial virus (RSV). This finding provides a better understanding of structure-function relationship in a 150-kDa protein. Irradiation of MEDI-493 with UV light resulted in spectral changes typical of Trp photoproducts and in a progressive loss of MEDI-493 binding and biological activity as measured by ELISA, Biacore, and cell-based assays. Mass spectrometric characterization of the proteolytic peptides generated from the UV irradiated MEDI-493 confirmed that most methionine (Met) and a few Trp residues were oxidized to various extents upon exposure to UV light. Among Trp residues, only Trp-105, containing the most solvent-exposed indole moiety in MEDI-493 and residing in a complementary-determining region (CDR) of the heavy chain, was significantly oxidized. When bound to a synthetic antigenic peptide, MEDI-493 showed significant resistance toward binding activity loss during UV irradiation. A second MAb (MEDI-524) with Trp-105 replaced by phenylalanine (Phe) showed a similar pattern of Met oxidation, but no loss of binding and biological activity following irradiation. Treatment of both MAbs with Met- and Trp-specific oxidizing reagents showed that oxidation of Trp-105 correlated with the activity loss, whereas Met oxidation did not affect the activity. These results demonstrate that Trp-105 in MEDI-493 is responsible for the UV light-induced effects.

LEVEL: INTERMEDIATE T he objective of the WellCharacterized Biotechnology Pharmaceutical (WCBP) CMC Strategy Forum is to provide an environment for the development of technical and regulatory consensus positions regarding topics of interest to WCBP. The January 2005 forum was devoted to a discussion of live virus vaccines and viral vectors used for gene therapy. The purpose of that meeting was to determine whether consensus positions could be reached among the delegates regarding lot release, stability, characterization, and comparability testing. The overarching questions posed were • What is the required testing for lot release and stability of vaccines? • What is the required testing for lot release and stability of viral vectors for genetic therapy? • What are the acceptable attributes of a “potency” test? • What is the best means of quantifying total and infectious viral particles? • What analytical parameters (obviously including those above) would be considered essential to support “comparability” of a viral product made by a modified process to that of the original process? In Part 1 (BioProcess International, April 2006) we described factors influencing the choices of lot-release and stability assays for vaccines and gene-therapy products. Part 2 presents case studies to illustrate potency testing (for a multivalent vaccine), characterization (for influenza), and comparability studies (for an adenovirus). The article concludes here by summarizing the panel discussion.