Creating well-defined parameters for virus validation helps to avoid issues along the way that can delay or complicate a process.
At Cytiva, we know how important it is to select the appropriate type and format of viral filtration studies that meet goals, while decreasing cost and process time. It is important to align studies to meet all applicable regulatory requirements, which is best achieved by creating a well-defined process validation approach. In this blog series, our team offers some general guidance on ensuring successful validation of a virus filtration process in the lab. We begin with the basics of viral filtration, and a look at the regulatory guidance available.
Working together
Biologic drugs require a strict level of quality because they go into human and animal bodies. Each drug needs to be validated for the removal of viral contaminants to achieve a minimal viral load. The level of virus clearance must be several orders of magnitude greater than the maximum possible virus titer that could potentially occur in the source materials used in the production process. It should also consider any adventitious viruses added during processing or manufacturing. This begins with proper raw material sourcing, screening, and supply chain management, and carries forward into validated virus reduction in the downstream process, typically validated by contract research laboratories.
Creating well-defined parameters for virus validation helps to avoid issues along the way that can delay or complicate a process. The process development team and validation laboratories will be working together to establish targets and ensure that they are met, to avoid any non-essential repetition of validation studies to streamline time and cost. This approach also helps when creating the downscale models that demonstrate the effectiveness of the virus filtration with intentionally added (spiked) virus to demonstrate the levels of removal.
Moving downstream
In the downstream processing step, there are purposely designed virus reduction steps to decrease the potential viral load. Each step is orthogonal to the others using a different reduction mechanism focused on a unique virus property. A final virus filtration step provides a typical reduction of 4 logs or greater.
Virus filtration is a robust, dedicated virus removal step that mainly works via size exclusion filters. The filters have pores that are large enough to allow the biologic drug substance to pass through but small enough to retain viruses. Depending on the filter choice there are different considerations and risk factors for virus breakthrough.
First generation virus filters can be impacted by lower system pressures, de-pressurization, and larger volume per unit throughputs. Pore plugging is a common challenge with filters that can lead to filter fouling and flux decay, which can negatively impact validation studies by reducing validated throughput and possibly skewing removal results.
How the pressure and flow affect throughput and capacity is also important. The specific reduction target or the purity of the spike in question should be considered rather than doing something because of a previous experience. Because the level of virus removal is so important, it is critical to model spiked virus runs as close to the exact same conditions used during process development and with the current process data.
Viral filtration regulations
The goal of a virus clearance studies is to confirm that the virus filtration approach will achieve the level of virus removal necessary. Quality by design (QbD) principles should always be considered when creating a viral clearance process. The filter selection and determination of the filter design space will drive the development of the overall viral clearance validation approach.
Good laboratory practice (GLP) certified laboratories are best suited for these studies. Trained staff with knowledge of valid downscale process models, simulated process conditions (temperature, filtration time, pressure, flow rate/flux decay, throughput/volume-to-filter area ratio, etc.), and representative product characteristics (protein concentration, quantities of aggregates and contaminants, pH, conductivity, viscosity, etc.) are needed. Knowing the most relevant regulatory guidelines to apply is critical. A few of the most common include:
- Harmonized ICH Q5A (R1) offers guidelines on “Quality of biotechnological products: viral safety evaluation of biotechnology products derived from cell lines of human or animal origin”
- USP <1050.1> provides more detailed information on study design, including the desired amount of virus clearance and the number and types of viruses to use and test runs to perform
- Parenteral Drug Association (PDA) Technical Reports 41 and 47 offer best practice guidance and recommendations on validation study design
- European Medicines Agency (EMA) and FDA have published additional guidance for specific types of biologic medicinal products for Europe and the United States
Other countries also have local regulatory guidelines for validation studies, so it is essential to be aware of the various requirements.