Test Process and Results of Potential Masking of Sterilizing-Grade Filters.

Pre-use/post-sterilization integrity testing (PUPSIT) has been a widely debated topic for the last several years. To a large extent, the debate is because of the fact that scientific data were not available to provide additional clarity that could inform appropriate risk-based judgements and commensurate actions. To gain clarity, the Parenteral Drug Association (PDA) and BioPhorum Organizations Group (BioPhorum) formed the Sterile Filtration Quality Risk Management (SFQRM) consortium in late 2017. The consortium goals have been to fill existing gaps in scientific data as adequately as possible with studies and industry guidance that would provide professionals and license holders with the ability to make informed decisions about appropriate risk-management strategies. This paper is one in a series of publications that are the result of the collaboration, and these should be considered together and viewed holistically in order to determine the best course of action with regard to PUPSIT. In total, the four papers cover the following areas: (1) data mining to determine the influence of fluid properties on integrity test values, (2) filter masking studies and results (this publication), (3) risk assessment and management from filter production to end use, and (4) points to consider in the best practice of the use of PUPSIT. In total, 25 manufacturers and filter suppliers have contributed to the work of the Consortium, deploying their filtration experts and pooling their collective knowledge and applied science experience to address these questions. This effort has also been supported by many independent experts currently available who have contributed to and driven the Filtration Interest Group in the PDA for many years. Both PDA and BioPhorum have prioritized this program and combined their approaches to deliver this comprehensive body of work. We hope that collectively the publications aid decision making and create greater certainty and confidence and above all alignment between suppliers, manufacturers, and regulators alike on these important questions.

Data Mining to Determine the Influence of Fluid Properties on the Integrity Test Values.

Eudralex volume 4, Annex 1, the European Union Good Manufacturing Practice for sterile products, requires that "The integrity of the sterilised filter should be verified before use" (1). Implicit in this requirement for a PUPSIT is the rationale that the sterilizing filter could sustain damage during sterilization or use (i.e., subsequent to any pre-use test conducted prior to sterilization), causing a defect which would not be detected by the post-use integrity ("masked" during filtration). To assess whether a filter defect could be masked by partial filter plugging, we evaluated the impact of the bacterial challenge test (BCT) on the bubble point (BP) of the test filters. The BP tests that are conducted before and after the BCT have been collected and compared for 2086 filters (1571 × test filters and 515 × control filters), representing 531 BCTs on 518 different pharmaceutical products, buffers, and in-process fluids. These tests comprise a cross section of fluids from multiple firms spanning the pharmaceutical and biotechnology industry. A posttest to pretest BP ratio was calculated for each filter and the distribution of these ratios examined to determine whether there were cases of elevation of the BP because of bacterial loading to the point where masking of a filter defect could occur; that is, if a defective filter could pass integrity testing due to apparent reduction in filter pore size because of the bacteria retained during the BCT. Ratios were averaged across all tests for the same test fluid. The mean average ratio was 1.00 ± 0.15, indicating that on the average, elevation of the BP does not occur. To assess the risk of masking a filter defect, observed BP ratios were compared to the ratio of the minimum BP specification of a 0.2 µm filter to that of a 0.45 µm filter of the same membrane type. The lowest such ratio for any membrane type was 1.33. A BP ratio equal to or higher than this ratio was considered a risk for masking, because a 0.45 µm filter could appear to meet the specifications of a 0.2 µm filter. Out of 518 average BP ratios, only eight fluids (1.5%) produced BP ratios meeting this criterion for a masking risk. Potential risk factors associated with these cases are discussed. We conclude that filtration processes producing BP changes sufficient to present a risk of masking defects are not common, and are detectable during the routine BCT. The BP ratios observed during routine BCT are one means to assess the potential of a given filtration process to mask defects and can be considered when determining whether a PUPSIT should be implemented.

The Development of a Microbial Challenge Test with Acholeplasma laidlawii To Rate Mycoplasma-Retentive Filters by Filter Manufacturers.

Mycoplasma are bacteria that can penetrate 0.2 and 0.22 µm rated sterilizing-grade filters and even some 0.1 µm rated filters. Primary applications for mycoplasma filtration include large scale mammalian and bacterial cell culture media and serum filtration. The Parenteral Drug Association recognized the absence of standard industry test parameters for testing and classifying 0.1 µm rated filters for mycoplasma clearance and formed a task force to formulate consensus test parameters. The task force established some test parameters by common agreement, based upon general industry practices, without the need for additional testing. However, the culture medium and incubation conditions, for generating test mycoplasma cells, varied from filter company to filter company and was recognized as a serious gap by the task force. Standardization of the culture medium and incubation conditions required collaborative testing in both commercial filter company laboratories and in an Independent laboratory (Table I). The use of consensus test parameters will facilitate the ultimate cross-industry goal of standardization of 0.1 µm filter claims for mycoplasma clearance. However, it is still important to recognize filter performance will depend on the actual conditions of use. Therefore end users should consider, using a risk-based approach, whether process-specific evaluation of filter performance may be warranted for their application. LAY ABSTRACT: Mycoplasma are small bacteria that have the ability to penetrate sterilizing-grade filters. Filtration of large-scale mammalian and bacterial cell culture media is an example of an industry process where effective filtration of mycoplasma is required. The Parenteral Drug Association recognized the absence of industry standard test parameters for evaluating mycoplasma clearance filters by filter manufacturers and formed a task force to formulate such a consensus among manufacturers. The use of standardized test parameters by filter manufacturers, including the preparation of the culture broth, will facilitate the end user's evaluation of the mycoplasma clearance claims provided by filter vendors. However, it is still important to recognize filter performance will depend on the actual conditions of use; therefore end users should consider, using a risk-based approach, whether process-specific evaluation of filter performance may be warranted for their application.