PDA’s Library of Filtration Best Practices Grows Stronger with Revised TR-26 and TR-41 20 February, 2009

Bethesda, Md. - PDA members who work with sterilizing and viral filters will benefit from updated best practices included in the 2008 revisions of PDA Technical Report No. 26, Sterilizing Filtration of Liquids and Technical Report No. 41, Virus Filtration.

TR-26 is intended to provide a systematic approach to selecting and validating the most appropriate filter for liquid-sterilizing filtration applications. The original was published in 1998 and described the use and validation of sterilizing filtration to a generation of pharmaceutical scientists and engineers. The 2008 revision was developed in response to enhancements in filtration technologies and recent additional regulatory requirements within the pharmaceutical industry. References to regulatory documents, standards and scientific publications are provided where more detail and supportive data may be found.

The task force for revising TR-26 was composed of European and North American industry and regulatory professionals to provide a diverse perspective, thus ensuring that the methods, terminology and practices of sterilizing filtration presented are reflective of sound science and can be utilized globally. This report underwent an 11-week global technical peer review that included feedback from the Americas, Asia-Pacific and Europe. 

The 2008 revision of TR-41 comes only a few years after its original publication, yet the update is significant. The new version includes protocols for both large virus retentive filters and small virus retentive filters, whereas the original addressed only the large virus filters. The document addresses virus removal filters that retain viruses by a size-exclusion mechanism. It explains how they work, recommends how to elect the best filter for various applications, physical and biological characterization and test methods, and validation. This document should be considered as a guide; it is not intended to establish any mandatory or implied standards.

In the technical report, large-pore virus filters are classified with the rating PR772-LRF6. Small-pore virus filers are classified with the rating PP7-LRF4. To support both ratings, PDA and the U.S. FDA Center for Drug Evaluation and Research performed as part of a CRADA an extensive physical and genetic characterization of both phages as well as an evaluation of their filtration properties. Both methods were prototype tested at FDA and were found to be acceptable for testing small-scale models of filters from four manufacturers.

PDA is completing a revision of Technical Report No. 15, Validation of Tangential Flow Filtration in a Biopharmaceutical Application.

Overall, PDA offers six technical reports on filtration, cementing PDA’s reputation as a primary source of best practices for filter suppliers and users in the pharmaceutical and biopharmaceutical industry. All PDA publications can be purchased at the Association’s online bookstore: www.pda.org\bookstore.