Product Characterization

Glycosylation of Therapeutic Proteins: Current Understanding of Structure–Function Relationships

A CMC Strategy Forum held in Washington, DC, on Sunday 28 January 2007 focused on two topics related to protein structure and function (1). First, analytical techniques used in the glycan analysis characterization included recent advances and correlations among the various tools. And second, current understanding of glycosylation’s functional relevance to therapeutic proteins was discussed in the context of its effects on biological activity, pharmacokinetics, and Fc effector functions (for monoclonal antibodies, MAbs). Progress has been made in the field…

Analysis and Structure Characterization of Monoclonal Antibodies

On 6 January 2003, 129 attendees participated in the second Well-Characterized Biotechnology Product (WCBP) Chemistry and Manufacturing Controls (CMC) strategy forum, titled “Analysis and Structure Characterization of Monoclonal Antibodies (MAbs),” held in San Francisco to discuss lot release and characterization test issues specific to MAbs (1). The objective of the meeting was twofold: to identify a “core” set of assays most useful for lot-release testing of MAbs and to define a mechanism for selecting appropriate potency tests. Two separate workshops…

Lot Release and Characterization Testing of Live-Virus–Based Vaccines and Gene Therapy Products

The January 2005 CMC Strategy Forum was devoted to a discussion of live virus vaccines and viral vectors used for gene therapy. The purpose of the meeting was to determine whether consensus positions could be reached among the delegates regarding lot release, stability, characterization, and comparability testing. Part 1 of this two-part report on that meeting describes factors influencing the choices of lot-release assays for vaccines and gene-therapy products (1). Part 2 presents potency testing, characterization, and comparability studies, including…

Biophysical Analysis: A Paradigm Shift in the Characterization of Protein-Based Biological Products

Generating a stable environment for a biopharmaceutical drug substance is a critical step for ensuring a long drug-product shelf life (1–6). This process begins early in development with preformulation screening. Some of the most critical parameters to maintaining potency and activity are protein conformation (tertiary or three-dimensional (3-D) structure), folding (secondary structure), and proper subunit association (quaternary structure). Collectively, those are known as higher-order structure (HOS) and can be highly influenced by the formulation environment of a protein drug product.…

Extracellular Vesicles Commercial Potential As Byproducts of Cell Manufacturing for Research and Therapeutic Use

Extracellular vesicles (EVs) are emerging as a potential alternative to some stem-cell–derived therapeutics (1, 2). Sometimes called exosomes, they are small, secreted vesicles that can possess similar therapeutic mechanisms to whole cells, possibly representing the active pharmaceutical ingredient. In the past 15 years, academic and industry interest in EVs has exponentially increased as mounting evidence demonstrates their role in physiology and pathology as well as their therapeutic potential. In light of growing efforts in using EVs for research and therapy,…

Hamster Phospholipase B-Like 2 (PLBL2): A Host-Cell Protein Impurity in Therapeutic Monoclonal Antibodies Derived from Chinese Hamster Ovary Cells

All recombinant protein biotherapeutics must be tested for the presence of residual host-cell protein (HCP) impurities (1–3). The most common analytical method for doing so is a polyclonal sandwich immunoassay. Polyclonal anti-HCP antibodies are selected to recognize the broadest population of HCPs possible. The immunogen and analytical standard are produced from a blank-run fermentation that mimics the production run but lacks the specific biotherapeutic protein. Because of the large number of impurities present in harvested cell-culture fluid (HCCF) that might…

Building a Robust Biological Assay for Potency Measurement

Potency is a critical quality attribute of a biological product and is often determined by a biological assay (also called bioassay or biopotency assay). Specifically, potency is the biological activity or capacity of a product directly linked to its clinical efficacy. Potency tests are performed as part of product release, comparability studies, and stability testing. Nonbiological methods — which measure a product’s molecular or biochemical characteristics (e.g., ligand-binding assay) — have gained interest as replacements for often troublesome bioassays. Even…

Unwanted Immunogenicity: From Risk Assessment to Risk Management

Although vaccines and immunotherapies are designed to engage the human immune system in fighting disease, unwanted immunogenicity can be a major problem for protein-based therapeutics. Some patients produce antidrug antibodies (ADAs), which might lead to drug inactivation or adverse effects. Even human and humanized proteins have proven to be surprisingly immunogenic in some cases, suggesting that immune tolerance requires careful consideration in biologic product design. In rushing to deliver new drugs to market, some biotherapeutics developers have overlooked factors that…

Predicting Aggregation Propensity and Monitoring Aggregates in ADCs

Antibody–drug conjugates (ADCs) are monoclonal antibodies coupled to cytotoxic agents with stable linkers. ADCs travel to target cells, where the antibody binds to its antigen expressed on the cell surface. Upon binding, the full ADC can be internalized by a process called receptor-mediated endocytosis. That process is followed by lysosomal degradation of ADC complexes, which ultimately leads to release of the cytotoxic agent and apoptosis of the target cell. Drugs used in ADCs can be up to a thousand times…

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UV-Vis Based Determination of Protein Concentration: Validating and Implementing Slope Measurements Using Variable Pathlength Technology

No longer are scientists bound to the time-consuming, error-prone use of dilution factors and fixed-pathlength measurements in determining the concentration of an analyte in solution. Using the slope spectroscopy technique, the Solo VPE system (from C Technologies) offers a new method of determining analyte concentration based on the Beer–Lambert law and slope derived from absorbance measurements made at multiple pathlengths (1). Mathematics: The Beer–Lambert law is expressed as A = αlc, where A is the measured absorbance, α is the…