Virus safety of plasma products using 20 nm instead of 15 nm filtration as virus removing step

Serial virus filtration: A case study evaluating the product-dependent impact of control strategies on process efficiency

The production of biopharmaceutical products carries an inherent risk of contamination by adventitious viruses. Historically, these manufacturing processes have incorporated a dedicated virus filtration step to ensure product safety. However, challenging process conditions can lead to passage of small viruses to the permeate pool and an overall decrease in the desired virus logarithmic reduction value (LRV) for the process. The implementation of serial virus filtration has improved the robustness of such processes, albeit concerns about increased operating times and process complexity have limited its implementation. This work focused on optimizing a serial filtration process and identifying process control strategies to provide maximum efficiency while ensuring proper controls for process complexity. Constant TMP was identified as the optimal control strategy, which combined with the optimal filter ratio, resulted in a robust and faster virus filtration process. To demonstrate this hypothesis, data with two filters connected in series (1:1 filter ratio) are presented for a representative non-fouling molecule. Similarly, for a fouling product, the optimal setup was a combination of a filter connected in series to two filters operated in parallel (2:1 filter ratio). The optimized filter ratios bring cost- and time-savings benefits to the virus filtration step, thereby offering improved productivity. The results of risk and cost analyses performed as part of this study combined with the control strategy, offer companies a toolbox of strategies to accommodate products with different filterability profiles in their downstream processes. This work demonstrates that the safety advantages of performing filters in series can be achieved with minimal increases in time, cost, and risk.

Nanofiltration as a robust method contributing to viral safety of plasma-derived therapeutics: 20 years' experience of the plasma protein manufacturers

BACKGROUND

Nanofiltration entails the filtering of protein solutions through membranes with pores of nanometric sizes that have the capability to effectively retain a wide range of viruses.

STUDY DESIGN AND METHODS

Data were collected from 754 virus validation studies (individual data points) by Plasma Protein Therapeutics Association member companies and analyzed for the capacity of a range of nanofilters to remove viruses with different physicochemical properties and sizes. Different plasma product intermediates were spiked with viruses and filtered through nanofilters with different pore sizes using either tangential or dead-end mode under constant pressure or constant flow. Filtration was performed according to validated scaled-down laboratory conditions reflecting manufacturing processes. Effectiveness of viral removal was assessed using cell culture infectivity assays or polymerase chain reaction (PCR).

RESULTS

The nanofiltration process demonstrated a high efficacy and robustness for virus removal. The main factors affecting nanofiltration efficacy are nanofilter pore size and virus size. The capacity of nanofilters to remove smaller, nonenveloped viruses was dependent on filter pore size and whether the nanofiltration process was integrated and designed with the intention to provide effective parvovirus retention. Volume filtered, operating pressure, and total protein concentration did not have a significant impact on the effectiveness of virus removal capacity within the investigated ranges.

CONCLUSIONS

The largest and most diverse nanofiltration data collection to date substantiates the effectiveness and robustness of nanofiltration in virus removal under manufacturing conditions of different plasma-derived proteins. Nanofiltration can enhance product safety by providing very high removal capacity of viruses including small non-enveloped viruses.

Two-Step Size-Exclusion Nanofiltration of Prothrombin Complex Concentrate Using Nanocellulose-Based Filter Paper

Coagulation Factor IX-rich protrhombin complex concentrate (FIX-PCC) is a therapeutic biologic product that consists of a mixture of several human plasma-derived proteins, useful for treating hemophilia B. Due to its complex composition, FIX-PCC is very challenging to bioprocess through virus removing nanofilters in order to ensure its biosafety. This article describes a two-step filtration process of FIX-PCC using a nanocellulose-based filter paper with tailored porosity. The filters were characterized with scanning electron microscopy (SEM), cryoporometry with differential scanning calorimetry, and nitrogen gas sorption. Furthermore, in order to probe the filter's cut-off size rejection threshold, removal of small- and large-size model viruses, i.e., ΦX174 (28 nm) and PR772 (70 nm), was evaluated. The feed, pre-filtrate, and permeate solutions were characterized with mass-spectrometric proteomic analysis, dynamic light scattering (DLS), sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and analytical size-exclusion high-performance liquid chromatography (SEHPLC). By sequential filtration through 11 μm pre-filter and 33 μm virus removal filter paper, it was possible to achieve high product throughput and high virus removal capacity. The presented approach could potentially be applied for bioprocessing other protein-based drugs.

Microscopic visualization of virus removal by dedicated filters used in biopharmaceutical processing: Impact of membrane structure and localization of captured virus particles

Virus filtration with nanometer size exclusion membranes (“nanofiltration”) is effective for removing infectious agents from biopharmaceuticals. While the virus removal capability of virus removal filters is typically evaluated based on calculation of logarithmic reduction value (LRV) of virus infectivity, knowledge of the exact mechanism(s) of virus retention remains limited. Here, human parvovirus B19 (B19V), a small virus (18–26 nm), was spiked into therapeutic plasma protein solutions and filtered through Planova™ 15N and 20N filters in scaled‐down manufacturing processes. Observation of the gross structure of the Planova hollow fiber membranes by transmission electron microscopy (TEM) revealed Planova filter microporous membranes to have a rough inner, a dense middle and a rough outer layer. Of these three layers, the dense middle layer was clearly identified as the most functionally critical for effective capture of B19V. Planova filtration of protein solution containing B19V resulted in a distribution peak in the dense middle layer with an LRV >4, demonstrating effectiveness of the filtration step. This is the first report to simultaneously analyze the gross structure of a virus removal filter and visualize virus entrapment during a filtration process conducted under actual manufacturing conditions. The methodologies developed in this study demonstrate that the virus removal capability of the filtration process can be linked to the gross physical filter structure, contributing to better understanding of virus trapping mechanisms and helping the development of more reliable and robust virus filtration processes in the manufacture of biologicals.

Cellulose-based virus-retentive filters: a review

Viral filtration is a critical step in the purification of biologics and in the monitoring of microbiological water quality. Viral filters are also essential protection elements against airborne viral particles. The present review first focuses on cellulose-based filter media currently used for size-exclusion and/or adsorptive filtration of viruses from biopharmaceutical and environmental water samples. Data from spiking studies quantifying the viral filtration performance of cellulosic filters are detailed, i.e., first, the virus reduction capacity of regenerated cellulose hollow fiber filters in the manufacturing process of blood products and, second, the efficiency of virus recovery/concentration from water samples by the viradel (virus adsorption-elution) method using charge modified, electropositive cellulosic filters or conventional electronegative cellulose ester microfilters. Viral analysis of field water samples by the viradel technique is also surveyed. This review then describes cellulose-based filter media used in individual protection equipment against airborne viral pathogens, presenting innovative filtration media with virucidal properties. Some pros and cons of cellulosic viral filters and perspectives for cellulose-based materials in viral filtration are underlined in the review.

Anti-Human Platelet Antigen-1a Immunoglobulin G Preparation Intended to Prevent Fetal and Neonatal Alloimmune Thrombocytopenia

Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is a severe disease that is caused by maternal alloantibodies generated during pregnancy or at delivery as a result of incompatibility between maternal and fetal human platelet antigens (HPAs) inherited from the father. Antibody-mediated immune suppression using anti-HPA-1a immunoglobulins is thought to be able to prevent FNAIT caused by HPA-1a. A fractionation process to prepare anti-HPA-1a immunoglobulin (Ig) G (IgG) from human plasma was therefore developed. Anti-HPA-1a plasma was obtained from volunteer mothers who underwent alloimmunization against HPA-1a during a previous pregnancy. Plasma was cryoprecipitated and the supernatant treated with caprylic acid and solvent/detergent (S/D), purified by chromatography, nanofiltered, concentrated, and sterile-filtered. The anti-HPA-1a immunoglobulin fraction was characterized for purity and safety. PAK12 and quantitative monoclonal antibody immobilization of platelet antigen (MAIPA) assays were used to detect anti-HPA-1a IgG. Hepatitis C virus (HCV) removal during nanofiltration was assessed by spiking experiments, using cell culture-derived reporter HCV and luciferase analysis. The caprylic acid treatment precipitated non-Ig proteins yielding a 90% pure Ig supernatant. S-HyperCel chromatography of the S/D-treated supernatant followed by HyperCel STAR AX provided high IgG recovery (>80%) and purity (>99.5%), and efficient IgA and IgM removal. Concentrations of complement factors C3 and C4 were < 0.5 and < 0.4 mg/dL, respectively. The final IgG could be nanofiltered on Planova 20N under conditions removing more than 3 log HCV infectivity to baseline mock infection level, and concentrated to ca. 30 g/L. Proteolytic activity and thrombin generation were low in the final fraction. The Pak12 and MAIPA assays showed good recovery of anti-HPA-1a throughout the process. Clinical-grade HPA-1a IgG can be prepared using a process compliant with current quality requirements opening perspectives for the prevention of FNAIT.