Conference report: host cell protein workshop at the 2012 annual bioassay meeting of the biopharmaceutical emerging best practices association.

At its 2012 Annual Bioassay Meeting, the Biopharmaceutical Emerging Best Practices Association held a 1-day workshop on host cell protein assays, which reflected the recent increase in activity and interest in this field. The workshop included 13 oral presentations and five posters and was attended by 70 delegates. It provided the opportunity for experts and newcomers to the field to discuss the particular challenges presented by these assays, addressing both technical issues and the theoretical considerations for future strategies. A number of case studies illustrated various advances that have been made and the limitations in current methodology. A further workshop, covering host cell protein and residual DNA in biotechnology products, will be held jointly with the US Pharmacopeia in June 2013.

Comparison of novel methods for predicting the risk of pro-inflammatory clinical infusion reactions during monoclonal antibody therapy.

Two methods for predicting the risk of pro-inflammatory clinical infusion reactions during monoclonal antibody therapy were evaluated. In the first, the antibody of interest is immobilised by air-drying onto 96-well plates prior to the addition of human peripheral blood mononuclear cells (PBMCs). In the second, the antibody is added in aqueous phase to a co-culture of human PBMCs and human endothelium-derived cells. In both methods the cells are incubated with the antibody to allow the accumulation of pro-inflammatory cytokines, quantified by enzyme-linked immunosorbent assay (ELISA). The antibodies associated with clinical infusion reactions, Herceptin, Campath-1H and TGN1412, gave the largest responses taking into account the data for all readouts (tumour necrosis factor-α, TNF, interleukin-6, IL-6, IL-8, IL-2 and cell proliferation) for both methods. Overall, the antibodies tested could be ranked as follows: Tysabri

Endothelial cells co-stimulate peripheral blood mononuclear cell responses to monoclonal antibody TGN1412 in culture.

The failure of preclinical testing to predict the severity of the cytokine storm experienced by the recipients of the superagonistic anti-CD28 monoclonal antibody (mAb) TGN1412 during its Phase 1 clinical trial prompted the development of new in vitro experimental approaches for mimicking in vivo cytokine release and lymphoproliferation. Peripheral blood mononuclear cells (PBMC) presented to TGN1412 immobilised on plastic has previously been shown to stimulate a pro-inflammatory cytokine response. The aim of the present study was to investigate a 'co-culture' model for the detection of TGN1412-like immunomodulatory activity in which TGN1412 was presented to PBMC in the presence of monolayers of endothelium-derived cells and other cell types, followed by measurement of cytokine levels in the culture supernatants and proliferation of PBMC. Culturing PBMC with TGN1412 over primary human umbilical vein endothelial cells (HUVEC) and HUVEC-derived cell lines retaining classic endothelial markers, but not cell lines of non-endothelial origin, mediated the specific release of IL-6, IL-8 and TNFα, and proliferation of PBMC. Low levels of IL-2 and IFNγ were also detected in supernatants with most donors of PBMC. An anti-CD28 mAb agonist, i.e., not a superagonist like TGN1412, did not stimulate cytokine release or proliferation of PBMC in co-cultures. In conclusion, co-culture experiments for TGN1412-specific cytokine release required cells of endothelial origin. However, the profile of released cytokines in co-cultures did not mirror that in the clinical trial participants or the responses from PBMC exposed to TGN1412 immobilised on plastic, suggesting that TGN1412 stimulation of PBMC can occur through more than one mechanism.

Quality control and analytical techniques for biopharmaceuticals.

Biopharmaceuticals are complex products and to ensure their batch-to-batch consistency and continuing quality the use of a combination of complementary analytical tests is required. Regulatory guidelines indicate quality attributes of different product classes to be included in the specifications for product release. Whilst the continuing development of sophisticated physicochemical techniques make them increasingly powerful for defining product identity, integrity, purity and the consistency of the manufacturing process, the results generated are not easily related to the biological activity. Consequently, a bioassay is normally required in the quality control to determine the potency, that is, the quantitative measure of the product's ability to cause a specific biological effect in a defined biological system. A wide, and rapidly increasing, range of bioassay systems exist, each type with particular advantages and disadvantages.

Biopharmaceutical Emerging Best Practices Association 2009.

The Biopharmaceutical Emerging Best Practices Association is a not-for-profit association founded in 2008 with the aim of providing "an international forum for the presentation and discussion of scientific issues and problems encountered in the biopharmaceutical community … to promote development of innovative approaches and solutions thus facilitating safer and faster biopharmaceutical product development."

Physicochemical and biological assays for quality control of biopharmaceuticals: interferon alpha-2 case study.

A selection of physicochemical and biological assays were investigated for their utility in detecting changes in preparations of Interferon alpha-2a and Interferon alpha-2b (IFN-alpha 2a, IFN-alpha 2b), which had been subjected to stressed conditions, in order to create models of biopharmaceutical products containing product-related impurities. The stress treatments, which included oxidation of methionine residues and storage at elevated temperatures for different periods of time, were designed to induce various degrees of degradation, aggregation or oxidation of the interferon. Biological activity of the stressed preparations was assessed in three different in vitro cell-based bioassay systems: a late-stage anti-proliferative assay and early-stage assays measuring reporter gene activation or endogenous gene expression by quantitative real time Reverse Transcription-Polymerase Chain Reaction (qRT-PCR). Relevant physicochemical methods such as SDS-PAGE, reverse phase (RP) chromatography, size-exclusion chromatography (SEC) and dynamic light scattering (DLS), proved their complementarity in detecting structural changes in the stressed preparations which were reflected by reductions in biological activity.

Quantitative RT-PCR as an alternative to late-stage bioassays for vascular endothelial growth factor.

We have investigated the use of quantitative reverse transcription-polymerase chain reaction (qRT-PCR) as an alternative to a selection of late-stage functional bioassays for determination of the potency of preparations of vascular endothelial growth factor (VEGF). Responses were measured in cultures of human umbilical vein endothelial cells (HUVECs). Late-stage responses measured were cell survival and proliferation, and production of interleukin-8 (IL-8), interleukin-6 (IL-6), and tissue factor. The dose-response range was similar across the assays, increasing from 2 ng/mL VEGF and reaching a maximum between 30 ng/mL and 125 ng/mL VEGF. A number of VEGF-induced mRNA species demonstrated dose-response curves suitable for VEGF potency determination. IL-8 mRNA induction after 45 min incubation with VEGF, which showed maximal responses between 15.6 ng/mL and 62.5 ng/mL VEGF, was selected for further characterization. This gene-expression bioassay was robust across a range of cell seeding densities and could be used for samples processed immediately following incubation with VEGF and for cell lysates stored at -80 degrees C for 3 months. We also compared this gene-expression bioassay and the assays of late-stage responses in the potency measurement of the inhibitors of VEGF activity, anti-VEGF monoclonal antibody MAB293, and a VEGF soluble receptor VEGFsR1 preparation. We present a critical evaluation of the use of qRT-PCR in assaying the potency of VEGF and its inhibitors, and of the potential of this platform for measuring the potency of other biological therapeutics.

The World Health Organization reference reagent for keratinocyte growth factor, KGF.

Preparations of human sequence recombinant keratinocyte growth factor (KGF), fibroblast growth factor-7 (FGF-7) synthesized in E. coli were formulated and lyophilized at National Institute for Biological Standards and Control (NIBSC) and evaluated in a collaborative study using in vitro bioassays and immunoassays. One candidate standard was the full-length mature KGF molecule and the two others were different formulations of a truncated form of the molecule, KGF (24-163). The study demonstrated the difficulty of performing interlaboratory comparison of assays without a common reference standard and differences in dose-response relationships between molecular variants. On the basis of the results reported here, the World Health Organization (WHO) established the preparation coded 03/150 as the WHO reference reagent for human KGF, with an assigned unitage of 4000 units of KGF per ampoule and the preparation coded 03/148 as the WHO reference reagent for human KGF (24-163), with an assigned unitage of 9000 units of KGF(24-163) per ampoule.

The World Health Organization reference reagent for vascular endothelial growth factor, VEGF165.

Preparations of human sequence recombinant vascular endothelial growth factor-165 (VEGF165) synthesized in Escherichia coli were formulated and lyophilized at NIBSC. Following evaluation at NIBSC, the first preparation, 01/424, has been distributed since 2002 as a NIBSC research reagent, but shows variation between ampoules in the volume and crystalline appearance of the lyophilized plug. A second preparation, 02/286, was subsequently lyophilized in a different formulation. Preparation 02/286 has now been evaluated in a collaborative study for its suitability to serve as a reference standard, and compared with preparation 01/424, by five laboratories using in vitro bioassays or immunoassays. On the basis of the results reported here, the World Health Organization (WHO) established the preparation coded 02/286 as the WHO reference reagent (RR) for human VEGF165, with an assigned unitage of 13,000 units per ampoule.