Recent revisions to EU manufacturing guidelines are changing how drug makers test processing technologies, according to the author of a new study, who cites growing use of an approach known as PUPSIT as an example.
PUPSIT, or pre-use post-sterilization integrity testing, is used to verify the integrity of sterilizing-grade filters after they have been sterilized, but before they have been used in a biopharmaceutical manufacturing process.
The idea is to make sure the filter has not been compromised during handling or sterilization and is still capable of retaining microorganisms, according to lead author Martin Glanz, Dr. rer. nat., senior principal scientist at Cytiva.
“Operationally, this typically involves wetting the membrane, venting the system, and then carrying out an integrity test such as a bubble point or forward-flow test. These methods essentially measure gas flow through the wetted membrane and confirm whether the filter meets its defined specifications,” he tells GEN.
Conventional verification processes focus on testing filters after they have been used, which, Glanz says, means that faults can be missed.
“The main benefit of PUPSIT compared to older approaches, which often relied heavily on post-use testing, is that you detect any potential defects before product exposure.
“That’s quite important, because defects can sometimes be masked during filtration— for example, due to fouling or plugging—and might not show up afterward. PUPSIT helps close that gap and strengthens overall sterility assurance,” he says.
The biopharmaceutical industry’s use of PUPSIT has increased since 2022, when EU GMP Annex 1, which covers the manufacture of sterile drugs, was revised to include stricter environmental monitoring and quality control requirements.
Glanz adds, “Even though PUPSIT isn’t always an absolute requirement, it is generally expected unless there is a well-justified, risk-based rationale not to perform it. Through PIC/S, this expectation is spreading beyond Europe as well.”
Adoption challenges
Switching from post-use verification strategies has significant potential benefits. However, implementing the approach can be challenging because, compared with traditional approaches, PUPSIT requires some additional steps, Glanz says.
“Companies often run into issues such as increased process complexity: you’re adding steps like wetting, venting, and testing that need to be controlled carefully.
“Additional connections can also introduce contamination risks, especially downstream of the sterilizing filter. In more manual setups, operator dependency becomes a real factor, and achieving reliable wetting can be trickier than it sounds.
“On top of that,” he continues, “more complex assemblies come with typical engineering challenges: dead legs, hold-up volumes, or simply designs that are harder to keep compliant. So, while the regulatory acceptance is clearly there, many organizations are still refining how to implement PUPSIT in a robust and efficient way.”
And technology—specifically single-use systems—is key to this refining process.
“There’s a clear trend toward single-use, preassembled flow paths, which help reduce handling and variability. At the same time, integrity testing technologies are evolving, both in terms of sensitivity and integration.
“Solutions that can assess not just the filter, but the system as a whole, are becoming increasingly relevant. Ultimately, it comes down to combining good engineering with reliable, well-validated procedures,” Glanz says.
Future
The emergence of automated testing systems is also likely to increase biopharma industry use of PUPSIT, according to Glanz.
“The benefits are quite tangible: automated wetting, venting, and testing steps; tighter control over process parameters; fewer manual interventions, particularly on the sterile side; and improved repeatability.
“Automation also enables better documentation, with electronic records and audit trails integrated directly into the system. In a way, this shifts the focus from operator execution to system design and validation, which aligns well with current regulatory thinking,” he says.
