Validation of viral clearance robustness
An important aspect of viral clearance is how well the virus reducing steps will tolerate variations outside the limits set of the process parameters. This is referred to as robustness and is increasingly emphasized by the authorities. It should be performed in a separate set of experiments where virus reduction is measured under conditions that deviate from the original limits. The robustness studies should also be performed with several viruses with different properties.
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Chromatography steps can have virus removal capacity. To show that this is a valid viral clearance step, the chromatography resin should be tested for its virus removal capacity both as a freshly packed column and after the final approved cycle.
The kinetics of inactivation are important since the rapid kill of large amounts of virus is indicative of a robust virucidal step.