Related Experiment Video
Updated: Oct 10, 2025

Early Viral Entry Assays for the Identification and Evaluation of Antiviral Compounds
Published on: October 29, 2015
Proceedings of the 2019 Viral Clearance Symposium, Session 1: Viral Clearance Strategies and Case Studies
Simon Reitz1, Astrid Schwantes2
1Boehringer Ingelheim Pharma GmbH & Co. KG, Birkendorfer Str. 65, 88397 Biberach an der Riss, Germany; and.
Insights
Strategies for demonstrating robust viral clearance of recombinant proteins and recombinant adeno-associated virus (rAAV) vectors were discussed. Methods for virus reduction and improved log reduction value calculations were proposed for regulatory compliance.
Area of Science:
- Biotechnology
- Virology
- Process Engineering
Background:
- Demonstrating viral clearance is critical for biotechnologically produced biologics and viral vectors.
- Current methods for viral clearance and log reduction value (LRV) calculation are subject to refinement.
- Recombinant adeno-associated virus (rAAV) vectors require specific strategies for adventitious virus reduction.
Purpose of the Study:
- To propose strategies for robust viral clearance using prior knowledge for recombinant proteins.
- To introduce methods for virus reduction applicable to rAAV vectors.
- To discuss proposals for generic viral clearance claims and refine LRV calculation methods.
Main Methods:
- Discussion of generic viral clearance claims for detergent inactivation (Triton CG-110), low pH, anion-exchange chromatography, and virus filtration.
- Presentation of ASTM standard development for retrovirus removal by small virus filters.
- Demonstration of methods for rAAV vector adventitious virus reduction including 35nm filtration, detergent/heat inactivation, and chromatography.
Main Results:
- Proposed strategies for demonstrating viral clearance and virus reduction for biologics and rAAV vectors.
- Identified areas for updating and refining conditions for retrovirus removal filters.
- Questioned current LRV calculation and proposed a modified concept.
- Demonstrated feasibility of multiple methods for rAAV adventitious virus reduction.
Conclusions:
- Prior knowledge and proposed methods can support robust viral clearance claims for recombinant proteins.
- Specific methods are feasible for reducing adventitious viruses in rAAV vectors, meeting ICH Q5A principles.
- Refinement of viral clearance strategies, filter standards, and LRV calculations is warranted.
Abstract:
Session 1 of the 2019 Viral Clearance Symposium proposed strategies to use prior knowledge for demonstrating robust viral clearance for biotechnologically produced recombinant proteins, such as monoclonal antibodies, and introduced methods for virus reduction applicable to recombinant adeno-associated virus (rAAV) vectors. Proposals for generic virus clearance claims were made for detergent inactivation with Triton CG-110, low pH inactivation, anion-exchange membrane chromatography, and virus filtration, and acceptance of these proposals were discussed. Furthermore, the development of an ASTM standard for retrovirus removal by small virus filters was presented, and it was found that updating and refining of conditions is still warranted. The current approach for log reduction value calculation by using the lower value from duplicate runs as worst case was questioned, and a modified concept was proposed. Finally, for rAAV vectors, several options for reduction of adventitious viruses were demonstrated such as 35 nm virus filtration, detergent inactivation, heat inactivation, and anion-exchange or affinity chromatography and were found to be feasible in order to satisfy the principles of ICH Q5A.
Related Concept Videos
Drug Clearance: Overview
Drug clearance is not limited to renal excretion but encompasses all organs involved in drug elimination, including...
Viral Structure
Drug Elimination: The Concept of Clearance
Drug clearance is not limited to renal excretion but encompasses all organs involved in drug elimination,...
Microorganisms in Medicine and Therapeutics
Subviral Agents
Viral Recombination

