In the 40-year history of biopharmaceuticals, there have been a few cases where the final products contained residual host cell protein (HCP) impurities at levels high enough to be of concern. This article summarizes the industry experience in these cases where HCP impurities have been presented in public forums and/or published. Regulatory guidance on HCP impurities is limited to advising that products be as pure as practical, with no specified numerical limit because the risk associated with HCP exposure often depends on the clinical setting (route of administration, dose, indication, patient population) and the particular impurity. While the overall safety and purity track record of the industry is excellent, these examples illustrate several important lessons learned about the kinds of HCPs that co-purify with products (e.g., product homologs, and HCPs that react with product), and the kinds of clinical consequences of HCP impurities (e.g., direct biological activity, immunogenicity, adjuvant). The literature on industry experience with HCP impurities is scattered, and this review draws in to one reference documented examples where the data have been presented in meetings, patents, product inserts, or press releases, in addition to peer-reviewed journal articles. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 34:828-837, 2018.

A covalent/electrostatic layer-by-layer self-assembly method was used to achieve polar ordering of a water soluble, reactive dye in the fabrication of nonlinear optical (NLO) films. We observed a quadratic relationship between the second harmonic intensity I 2ω and bilayer number for all films made with Procion Brown MX-GRN, demonstrating that the polar ordering of the chromophores is consistent in each successive bilayer. As the ionic strength of the dye deposition solution was increased to 0.5 M NaCl, the of the films increased by approximately 250% to 50 × 10-9 esu, with a corresponding average chromophore tilt angle of 38°. This was attributed to increased shielding of the dye charges which led to higher chromophore density in the bilayers. The electrooptic coefficient for films of 50 bilayers fabricated at 0.5 M NaCl was 14 ± 2 pm/V. Importantly, these films exhibited excellent thermal stability, with only a 10% decrease in (I 2ω)1/2 after 36 h at 85 °C and then 24 h at 150 °C. Furthermore, the (I 2ω)1/2 recovered completely upon cooling to room temperature. These results with a commodity textile dye point to the potential value of this class of reactive chromophores and this self-assembly method for fabrication of electrooptic materials at ambient conditions from aqueous solutions.

Appropriate glycosylation of recombinant therapeutic glycoproteins has been emphasized in biopharmaceutical industries because the carbohydrate component can affect safety, efficacy, and consistency of the glycoproteins. Reliable quantification methods are essential to ensure consistency of their products with respect to glycosylation, particularly sialylation. Mass spectrometry (MS) has become a popular tool to analyze glycan profiles and structures, showing high resolution and sensitivity with structure identification ability. However, quantification of sialylated glycans using MS is not as reliable because of the different ionization efficiency between neutral and acidic glycans. We report here that amidation in mild acidic conditions can be used to neutralize acidic N-glycans still attached to the protein. The resulting amidated N-glycans can then released from the protein using PNGase F, and labeled with permanent charges on the reducing end to avoid any modification and the formation of metal adducts during MS analysis. The N-glycan modification, digestion, and desalting steps were performed using a single-pot method that can be done in microcentrifuge tubes or 96-well microfilter plates, enabling high throughput glycan analysis. Using this method we were able to perform quantitative MALDI-TOF MS of a recombinant human glycoprotein to determine changes in fucosylation and changes in sialylation that were in very good agreement with a normal phase HPLC oligosaccharide mapping method.

Glycosylation of recombinant proteins is of particular importance because it can play significant roles in the clinical properties of the glycoprotein. In this work, the N-glycan structures of recombinant human Factor IX (tg-FIX) produced in the transgenic pig mammary gland were determined. The majority of the N-glycans of transgenic pig-derived Factor IX (tg-FIX) are complex, bi-antennary with one or two terminal N-acetylneuraminic acid (Neu5Ac) moieties. We also found that the N-glycan structures of tg-FIX produced in the porcine mammary epithelial cells differed with respect to N-glycans from glycoproteins produced in other porcine tissues. tg-FIX contains no detectable Neu5Gc, the sialic acid commonly found in porcine glycoproteins produced in other tissues. Additionally, we were unable to detect glycans in tg-FIX that have a terminal Galalpha(1,3)Gal disaccharide sequence, which is strongly antigenic in humans. The N-glycan structures of tg-FIX are also compared to the published N-glycan structures of recombinant human glycoproteins produced in other transgenic animal species. While tg-FIX contains only complex structures, antithrombin III (goat), C1 inhibitor (rabbit), and lactoferrin (cow) have both high mannose and complex structures. Collectively, these data represent a beginning point for the future investigation of species-specific and tissue/cell-specific differences in N-glycan structures among animals used for transgenic animal bioreactors.