Host cell protein networks as a novel co-elution mechanism during protein A chromatography.

Host cell proteins (HCPs) are process-related impurities of therapeutic proteins produced in for example, Chinese hamster ovary (CHO) cells. Protein A affinity chromatography is the initial capture step to purify monoclonal antibodies or Fc-based proteins and is most effective for HCP removal. Previously proposed mechanisms that contribute to co-purification of HCPs with the therapeutic protein are either HCP-drug association or leaching from chromatin heteroaggregates.

Using enhanced development tools offered by analytical Quality by Design to support switching of a quality control method.

Quality by Design (QbD) principles play an increasingly important role in the pharmaceutical industry. Here, we used an analytical QbD (AQbD) approach to develop a capillary electrophoresis sodium dodecyl sulfate under reducing conditions (rCE-SDS), with the aim of replacing SDS-polyacrylamide gel electrophoresis (SDS-PAGE) as release and stability test method for a commercialized monoclonal antibody product. Method development started with defining analytical method performance requirements as part of an analytical target profile, followed by a systematic risk assessment of method input parameters and their relation to defined method outputs.

Best practices on critical reagent characterization, qualification, and life cycle management for HCP immunoassays.

The performance of immunoassays for the detection and quantification of host-cell proteins (HCPs) in biopharmaceuticals depends on the quality of the critical assay reagents. Not only their preparation, but also a stringent life-cycle management, including reagent qualification, requalification, and replacement, plays a crucial role in ensuring consistent and reliable results. To provide a cross-industry perspective on HCP reagent management, we conducted a survey on common practices among several pharmaceutical and biotech companies.

Host Cell Protein Profiling in Biopharmaceutical Harvests.

Biopharmaceuticals contain residual host cell protein (HCP) impurities, a complex mixture of endogenous proteins from production cell lines such as Chinese hamster ovary (CHO) cells. The composition of HCP impurities at harvest hinges on multiple factors, e.g.

Development of a novel affinity chromatography resin for platform purification of lambda fabs.

Antigen-binding fragments (Fabs) are novel formats in the growing pipeline of biotherapeutics. Sharing similar features to monoclonal antibodies (mAbs) with regard to expression, Fabs are considered as unchallenging for upstream development. Yet for downstream processing, the mature mAb downstream purification platform is not directly applicable.

Direct demonstration of half-of-the-sites reactivity in the dimeric cytochrome bc1 complex: enzyme with one inactive monomer is fully active but unable to activate the second ubiquinol oxidation site in response to ligand binding at the ubiquinone reduction site.

We previously proposed that the dimeric cytochrome bc(1) complex exhibits half-of-the-sites reactivity for ubiquinol oxidation and rapid electron transfer between bc(1) monomers (Covian, R., Kleinschroth, T., Ludwig, B.

Surf1, associated with Leigh syndrome in humans, is a heme-binding protein in bacterial oxidase biogenesis.

Biogenesis of mitochondrial cytochrome c oxidase (COX) relies on a large number of assembly factors, among them the transmembrane protein Surf1. The loss of human Surf1 function is associated with Leigh syndrome, a fatal neurodegenerative disorder caused by severe COX deficiency. In the bacterium Paracoccus denitrificans, two homologous proteins, Surf1c and Surf1q, were identified, which we characterize in the present study.

Biophysical characterization of the interaction between hepatic glucokinase and its regulatory protein: impact of physiological and pharmacological effectors.

Glucokinase (GK) is a key enzyme of glucose metabolism in liver and pancreatic beta-cells, and small molecule activators of GK (GKAs) are under evaluation for the treatment of type 2 diabetes. In liver, GK activity is controlled by the GK regulatory protein (GKRP), which forms an inhibitory complex with the enzyme. Here, we performed isothermal titration calorimetry and surface plasmon resonance experiments to characterize GK-GKRP binding and to study the influence that physiological and pharmacological effectors of GK have on the protein-protein interaction.

Characterization of mutations in crucial residues around the Q(o) binding site of the cytochrome bc complex from Paracoccus denitrificans.

The protonation state of residues around the Q(o) binding site of the cytochrome bc(1) complex from Paracoccus denitrificans and their interaction with bound quinone(s) was studied by a combined electrochemical and FTIR difference spectroscopic approach. Site-directed mutations of two groups of conserved residues were investigated: (a) acidic side chains located close to the surface and thought to participate in a water chain leading up to the heme b(L) edge, and (b) residues located in the vicinity of this site. Interestingly, most of the mutants retain a high degree of catalytic activity.

Thermodynamic characterization of allosteric glycogen phosphorylase inhibitors.

Glycogen phosphorylase (GP) is a validated target for the treatment of type 2 diabetes. Here we describe highly potent GP inhibitors, AVE5688, AVE2865, and AVE9423. The first two compounds are optimized members of the acyl urea series.

The Rieske protein from Paracoccus denitrificans is inserted into the cytoplasmic membrane by the twin-arginine translocase.

The Rieske [2Fe-2S] protein (ISP) is an essential subunit of cytochrome bc(1) complexes in mitochondrial and bacterial respiratory chains. Based on the presence of two consecutive arginines, it was argued that the ISP of Paracoccus denitrificans, a Gram-negative soil bacterium, is inserted into the cytoplasmic membrane via the twin-arginine translocation (Tat) pathway. Here, we provide experimental evidence that membrane integration of the bacterial ISP indeed relies on the Tat translocon.

Assembly of respiratory complexes I, III, and IV into NADH oxidase supercomplex stabilizes complex I in Paracoccus denitrificans.

Stable supercomplexes of bacterial respiratory chain complexes III (ubiquinol:cytochrome c oxidoreductase) and IV (cytochrome c oxidase) have been isolated as early as 1985 (Berry, E. A., and Trumpower, B.

Electrochemical and FTIR spectroscopic characterization of the cytochrome bc1 complex from Paracoccus denitrificans: evidence for protonation reactions coupled to quinone binding.

The cytochrome bc(1) complex from Paracoccus denitrificans and soluble fragments of its cytochrome c(1) and Rieske ISP subunits are characterized by a combined approach of protein electrochemistry and FTIR difference spectroscopy. The FTIR difference spectra provide information about alterations in the protein upon redox reactions: signals from the polypeptide backbone, from the cofactors, and from amino acid side chains. We describe typical modes for conformational changes in the polypeptide and contributions of different secondary structure elements.