Does Pre-Use Post-Sterilization Integrity Testing (PUPSIT) Reduce Risk for Sterile Filtration

The life science business of Merck KGaA,
Darmstadt, Germany operates as
MilliporeSigma in the U.S. and Canada.
Does PUPSIT reduce
risk for sterile
filtration?
Janmeet Anant, Senior Regulatory Consultant
Andrew Koch, Sterile Filtration Technology Manager
18 March 2021

The life science business
of Merck KGaA, Darmstadt,
Germany operates as
MilliporeSigma in the U.S.
and Canada

Agenda
1
2
3
Regulatory Background of Pre-Use Post
Sterilization Integrity Test (PUPSIT)
Masking study - PUPSIT
Final Filtration Assemblies –
Design/Implementation
4 Q & A

Regulatory
Background of
PUPSIT

Why Integrity Test Critical Filters?
Filtration is required as a terminal sterilization step for biologics
Product Safety
• Sterile filtration is the most critical
step to assure microbial safety
• Pre-use: confirm manufacturer’s
specifications, confirm no damage
during sterilization
• Post-use: confirm filter provides
expected bacterial retention
Business practice
 Guidance and regulations
 Corporate practices
Does PUPSIT reduce risk for sterile filtration? | 18 March 2021
5

There is no common filtration set-up
Points to Consider to Design a Sterile Filtration Process
How
many?
Device
design
Filter
Design
Integrity
test
Flushing
In/out
isolator?
Product
recovery
Choosing the right
number of filters:
single, dual, redundant
Pre-use and post-use
filter integrity test
Filters in or out of the
isolator?
Stacked vs. pleated
Flush bag vs. barrier
filters
Downstream blow down
6

Supplier
End-User
Integrity Testing of sterilizing grade filter
A critical element of overall sterility assurance strategy
Validated sterilizing membrane
Validated sterilizing filter
Bacterial retention validation
testing (WCC)
Process Validation and Control
Batch integrity test
7

Historical Regulatory Guidance: Pre-Use Integrity Test
“Integrity testing of the filter can be performed prior to
process and should be routinely performed post-use.”
Guidance for Industry. Sterile Drug Products Produced by Aseptic
Processing - Current Good Manufacturing Practice. U.S. Department of
Health and Human Services Food and Drug Administration. September
2004. Pharmaceutical CGMPs
FDA Aseptic Processing
guidelines, 2004
“ The integrity of the sterilised filter should be verified
before use and should be confirmed immediately after
use by an appropriate method such as a bubble point,
diffusive flow or pressure hold test.”
EudraLex. The Rules Governing Medicinal Products in the European
Union. Volume 4. EU Guidelines to Good Manufacturing Practice
Medicinal Products for Human and Veterinary Use. Annex 1. Manufacture
of Sterile Medicinal Products. EUROPEAN COMMISSION. Brussels, 25
November 2008
EMA Annex 1, 2008
8

Critical Liquid Filters
When to Integrity Test?
9

Filter Integrity Testing
Protects the Patient from microbial contamination
This possibility is called “blinding” or “flaw masking”
Filter
Life
Cycle
Manufacture Sterilization Filtration
Integral Non-Integral Appears
Integral
• Is post-use filter integrity testing sufficient to detect filter failure?
• Is there a possibility that a filter pass the post-use test and have allowed bacterial penetration
during filtration?
10

Historical Positions on PUPSIT
Industry position
• Low value, flaw masking is uncommon
• PUPSIT adds risk, may compromise aseptic pathway
• Adds complexity, stresses filter
European regulatory position
• Essential: filtration is risky, flaw masking is a risk
• Industry just does not want to do it, risk assessments are
biased
FDA position
• Nothing official
• Decisions should be risk based
11

Regulatory -
EU GMP Annex 1 draft, 2020:
 Integrity test before use and
post-use
 “…[PUPSIT] may not always
be possible after sterilization due
to process constraints (e.g. the
filtration of very small volumes of
solution). In these cases, an
alternative approach may be taken
as long as a thorough risk
assessment has been performed
and compliance is achieved by the
implementation of appropriate
controls to navigate any risk of
non-sterility.
Industry -
PDA Technical Report 26:
“Integrity testing alone is
insufficient to assure the sterility
of the filtrate. At least two other
elements must be in place:
 The production controls and
quality assurance systems
used by the filter
manufacturer ...
 And the validation studies
used to show that a particular
combination of product,
processing conditions and
sterilizing grade filter will meet
the requirements of the
bacterial challenge test.”
Establish minimum
Bubble Point
Membrane manufacturing
and testing
Device manufacturing
and testing
Validation studies
End-user integrity test
Integrity test of "sterilizing filter” alone is insufficient
Evolving Perspective – Sterility Assurance
12

PUPSIT Consortium Initiated
• Biophorum and PDA Memo of
Understanding (Dec 2017)
• Goal: Gather data and evaluate potential
risks on the merit of PUPSIT to provide
guidance to industry
• Joint effort of filter suppliers and
drug manufacturers
14

 Flaw must be large enough to pass
microbiological contamination
 Flaw must be small enough to be
closed by clogging
 Material must be present that can
plug the defect to such an extent
that it is not detectible by post-use
integrity testing
Conditions Necessary for Masking
15

PUPSIT
Risk
Masking
Risk
• Increased complexity of the
filtration set-up
• Manipulation of the sterilized
filtrate side
• Microbial ingress of the
filtrate side
• Product dilution with wetting
fluid
• With product wetting,
unknown effects on the
product by the test gas and
time
• …
• Flawed filter will not be
detected by the post-use test
• Microbial penetration
potential not being detected
• Sterilization process
detriments are not detected
• …
The Risk Balance
We Need Data for Resolution
16

• Blocking/masking trials performed with
various filters to see whether masking is
possible
• Filter suppliers tested marginally flawed filter
elements
• Test protocol established and reviewed by
European regulators
• Results from bacterial challenge tests were
reviewed to determine if there was any
change in pre-use and post-use integrity test
values
• Results from multiple trials with abroad range
of solutions were reviewed
Masking Trials and Data Mining
Masking Trials
Data mining
The Approach
17

Problems and Solutions
Collaboration Team PDA/BPOG
What Has Been Done?
1. Masking studies: can masking occur?
2. Data mining of available bacterial challenge test data
3. Identifying known and potential failure modes of
sterilizing grade filters
Deliverables
1. Developing a risk assessment template to
determine if PUPSIT is warranted
2. Identify best practices for performing PUPSIT
3. Presenting findings to Regulatory
18

Determination of Test Parameters
Test Fluid
Ovaltine™: proteinaceous malt, cocoa extract → mimics biologics solution well
Blocking rate
Foulant concentration
24 g/L
worst
case
0.8g/L
mimic
typical
biologic
Masking Trials - Test Fluid
Typical area of
capacity use
Worst case
blockage,
commonly not
used in
terminal sterile
filtration
19

• Filter manufacturers collected marginal flawed 10” filter cartridges
Determination of Test Parameters
Masking Trials – Phase 1 Test Protocol
Filters wet and IT
(BP or diffusion)
All integrity tests were performed with
automated integrity test systems
Exposed to blocking
solution (24 g/L Ovaltine™)
at 10 psig to
>90% blocking
Filters
flushed with water (50
L/m2) and IT
(BP or diffusion)
24 g/L
Ovaltine™
>90%
blocking
>90%
24g/L
Worst Case
Scenario
Foulant
Concentration
Blocking
Rate
20

Masking trials of flawed 10” filters, tested under worst-case conditions (> 90% blocked)
24 filters tested → 2 passed (masking occurred) and 22 failed the post-use integrity test
Take-home messages
• Confirmed that ‘worst-case’ blocking rate and foulant concentrations
can mask minor flaws in 10% of cases
• Unlikely a high blocking rate would be seen at a terminal filtration
step
>90%
blocking
Masking Trials
Phase 1- Results
24 g/L
Ovaltine™
>90%
blocking
Next steps
• Phase 2 trials at different blocking rates and foulant concentrations
24 g/L
Ovaltine™
>90%
blocking
92%
8%
Masking Phase 1
Failed Pass
21

Masking Trials, 47 mm discs, laser drilled flaw
44 integrity tests were performed at 0.8 g/L
→ 2 passed the post use integrity test (masked) (81% and 97%
blockage) and 42 failed the post use integrity test
8 integrity tests were performed at 24 g/L
→ very difficult to filter through a 47 mm disk; all failed post use integrity
test
Take-home messages
• We verified, using Ovaltine, that only at very high blocking rates filter flaws
may be masked: no passing post-use integrity tests (masking) on blockage
rates less than 75% irrespective of fouling solution concentration
• Filter masking does not always happen as 16 out of 18 47 mm disc filters at a
blockage rate >80% failed the post-use test (no masking)
• Filter flaw masking is highly dependent on the product and process
conditions.
Masking Trials
Phase 2- Test Protocol
96%
4%
Masking Phase 2
Failed Pass
22

✓Masking of sterilizing grade filter flaws may occur under extreme circumstances of fouling and blocking.
➢All filters with blocking below 75% failed the post use integrity test (no masking occurred).
➢The few filters that passed the post use integrity test (i.e. masked) were blocked more than 80%
✓Masking of defects in filters pore blocking is highly dependent on the process, product and filter capacity
conditions
Masking Trials
Summary of trials with flawed filters
PUPSIT
Risk
Masking
Risk
23

✓Filterability trials and understanding product and process conditions could be used to determine whether
masking is a possibility or not
➢Prefilters can be used to reduce fouling of sterilizing filters will minimize the risk of filter masking
✓Decisions should balance the risks of PUPSIT implementation vs possibility of filter masking
✓More information on the Masking Studies, Data Mining Studies, Risk Assessments, and PUSPIT
Implementation Considerations are available in publications from the Task Force
Task Force Conclusions
PUPSIT
Risk
Masking
Risk
24

Final Filtration
Assemblies –
Design/Implementation

PUPSIT Best Practices-Things I Have Learned Along the Way…
SURF Design Considerations
26

Process Design Considerations
Designed for PUPSIT
Not Designed for PUPSIT
•Number of filters in system
•Single stage
•Dual stage
•Redundant
•Flushing
•Flush bag (catch can) or barrier
filter
•Product Recovery
•Blow down through filter
•Downstream blow down
27

Redesigned Port Minimizes Contamination Risk
Aseptic actuation
PUPSIT & product
recovery
Aseptic sampling
Aseptic Multi-
Purpose Port
(AMPP)
28

Number of Filters in the System
Designs for final filtration systems
Single Filter Dual Filter Redundant
✓ Compliance with regulatory guidance
for <10 CFU/100 ml
✓ Minimizes plugging risk for secondary filter
BENEFITS
 No back-up in the event of primary
filter failure
 Higher hold-up volume
 Higher cost
 Higher system complexity
CONSIDERATIONS
✓Minimum hold-up volume
✓Minimum flushing requirements
✓Ease of handling and operation
✓Lower filter cost
BENEFITS
 No back-up in the event of primary filter failure
 Minimal feed bioburden control
 High probability of filter plugging
CONSIDERATIONS
✓Compliance with regulatory guidance for
<10 CFU/100 ml
✓Low plugging risk for primary filter
✓Potential batch recovery if one filter fails
integrity test
BENEFITS
 Higher hold-up volume
 Higher cost
 Higher system complexity
CONSIDERATIONS
Bulk
Product
Sterile
Filter
Bulk
Product
Sterile
Filter
Sterile
Filter
Intermediate
Product Hold
Bulk
Product
Sterile
Filter
Sterile
Filter
Bulk Product
Bioburden
Reduction
Filter
Sterile
Filter
29

Regulatory Guidance – Redundant Filters
FDA Aseptic Processing Guidelines, 2004
“Use of redundant sterilizing filters should be considered in
many cases”
•Guidance for Industry. Sterile Drug Products Produced by Aseptic Processing -
Current Good Manufacturing Practice. U.S. Department of Health and Human
Services Food and Drug Administration. September 2004. Pharmaceutical
CGMPs
EMA Annex 1, 2008
“Due to the potential additional risks of the filtration method
as compared with other sterilization processes, a second
filtration via a further sterilised micro-organism retaining
filter, immediately prior to filling, may be advisable. The
final sterile filtration should be carried out as close as
possible to the filling point.”
•EudraLex. The Rules Governing Medicinal Products in the European
Union. Volume 4. EU Guidelines to Good Manufacturing Practice Medicinal
Products for Human and Veterinary Use. Annex 1. Manufacture of Sterile
Medicinal Products. EUROPEAN COMMISSION. Brussels, 25 November 2008
30

Sterilizing
Filter
Vent Filter
Sterilizing
Filter
Redundant sterile filtration may be done in:
− Conventional hardware such as stainless
steel
− Single-use pre-sterilized systems
− Hybrid (mix of stainless steel and
single-use) systems
Three key criteria
1. The space between the two sterilizing filters must be kept sterile
during the entire operation
2. Each sterilizing filter must be capable of being integrity tested
independently in compliance with the relevant regulations or
guidelines
3. Both sterile filters must be traceable to a relevant filter validation
Criteria for a Redundant Filtration System
31

Remove –
 Wetting Liquid
 Test Gas
While
Maintaining
downstream
 Sterility
 Atmospheric pressure
(test)
Practical Challenges when Performing PUPSIT
Class C
Filling Line
Sterilizing
Product
Filter
Water Gas
32

Current Practice 2
Pre-use test: to flush derivation tank
B
C
Filling Line
Sterilizing
Product
Filter
A
Catch can or
flush volume
tank
Option 1: Catch Can
✓ Extractables are removed
from filtration line
❖ Wetting volume to re-wet
and re-test is limited by flush
tank capacity
❖ Flush tank handling and
preparation is cumbersome
❖ Carboy or flush tank vent
filter to be tested
Points to consider
33

B
C
Filling Line
Sterilizing
Product
Filter
A
Phobic/Philic
Hybrid filter
Option 2: Barrier Filter
✓ Unlimited flush volumes
✓ Line blowdown
✓ Passive draining
✓ Lowest filtrate line complexity
✓ One filters to test off-line with
IPA/water wetting solution
❖ Breathing capacity profile linked
to Phobic material and chemistry
Points to consider
Barrier filters contain hydrophilic and hydrophobic sterilizing
membranes
34

What is a Barrier Filter?
One disk
pair
3 x Hydrophilic
membranes
1 x Hydrophobic
membrane
Gas
Liquid
Condensate
Barrier filters can pass both
liquid and gas.
35

36

Recovery: Post Process Product Recovery
• During processing the entire system is flooded
with product
• Gas will not pass through the wet membrane
below the bubble point pressure
• To displace downstream liquid with gas requires
either exceeding the bubble point OR applying low
pressure through the vent between the product
filters
• Displaces downstream liquid
Or Low pressure
gas
High pressure
gas
37

Blow-down through final
filter
(Exceed filter bubble
point > 50 psi)
Blow-down after final
filter
(Air introduced
downstream)
Post Process Product Recovery
+ No added downstream
fittings
+ No downstream
manipulations
− Requires proper validation
− Risks product foaming
− Downstream component
pressure limits
+ Low pressure
+ Low shear/foaming
+ No added filter validation
concern
− Requires sterile gas filter
• That will require testing
− Requires downstream
fittings and manipulations
38

▪ Filter mix-up – which filter did I test ?
▪ Clamp Sequence
 For every step, you need to make sure you know where the
liquid is going and where the air is going
▪ Make sure vent filter does not get wet. Keep it elevated
▪ Make sure vents on filters are closed at the start
▪ Make sure vents are at the high point
Learn From My Mistakes
39

Example of Valve Sequencing
Clamp # Clamp Location
Description
Flushing Filter
F 1
Flushing
Filter F 2
Integrity
Test F1
Integrity
Test F2
F1
Blowdow
n
F2
Blowdown
Processing
1 Process Inlet OPEN OPEN CLOSED CLOSED CLOSED CLOSED OPEN
2 F1 Airline CLOSED CLOSED OPEN CLOSED OPEN CLOSED CLOSED
3 Downstream of
F1
CLOSED OPEN CLOSED CLOSED CLOSED CLOSED OPEN
4 F1 Millipak
®
Barrier filter
CLOSED CLOSED OPEN CLOSED OPEN CLOSED CLOSED
5 F2 Airline CLOSED CLOSED CLOSED OPEN CLOSED OPEN CLOSED
6 F2 Millipak
®
Barrier filter
CLOSED CLOSED CLOSED OPEN CLOSED OPEN CLOSED
7 Process Outlet CLOSED CLOSED CLOSED CLOSED CLOSED CLOSED OPEN
Monitoring fluid and air
is complicated. Developing a detailed
SOP will reduce risk.
Utilizing a transparent or translucent
filter will help reduce operator error
40

A high number of PUPSIT failures are due to insufficient
wetting:
• Indicated by a marginal failure
• Bubble point that up is up to 30% lower than the
specification
• Diffusional flow rate that is up to 50% higher than the
specification
Check Manufacturer’s recommendations:
• Flush volumes
• Wetting pressure / flow rate
• Pressure hold for static soaking
Filter Wetting Best Practices
41

Handling Single-use Assemblies:
Implementation
• Consider the fixture of the assemblies in relation to the
filling line
• A support frame is recommended
• Frames need to be custom-made
• Assembly is unique to the needs of each end-user
• Designs will vary from plant to plant and even from
process to process
• Difficult to have a ‘one size fits all’ approach to
assemblies
• Frames are usually stainless steel
• Easily designed and fabricated
• Creates a familiar feel for the operator
42

1. Flaw masking is possible with severely blocked filters
• PUPSIT mitigates the impact of masking
• For the majority of filtration operations, flaw masking is unlikely to occur
2. Users should assess the risk of flaw masking based on their fluid stream and process
conditions
3. If there is a reasonable risk of flaw masking, the default should be to perform PUPSIT
4. If there is negligible risk of flaw masking, it is recommended users consider a risk-based
approach to the implementation of PUPSIT
5. Improving the design of the final filtration assembly can simplify PUPSIT and product recovery
Conclusions
43

Document Acceptance/Publication
Data mining to Determine the Influence of
Fluid Properties on the Integrity Test Values
Published in the PDA
https://journal.pda.org/content/early/2020/05/28/pdajpst.2019.011387
Test Process and Results of Potential
Masking of Sterilizing Grade Filters
https://journal.pda.org/content/early/2020/05/28/pdajpst.2019.011189
PDA Points to Consider for Risks Associated
with Sterilizing Grade Filters and Sterilizing
Filtration
https://www.pda.org/bookstore/product-detail/5748-points-to-consider-
pupsit1
PDA Points to Consider for Implementation of
Pre-Use Post Sterilization Integrity Testing
(PUPSIT)
https://www.pda.org/bookstore/product-detail/5790-points-to-consider-
pupsit2
Capstone Article Published in the PDA Letter June 2020
https://www.pda.org/pda-letter-portal/home/full-article/the-use-of-
scientific-data-to-assess-and-control-risks-associated-with-sterilizing-
filtration
Publications
https://www.biophorum.com/resource/sterile-filtration-qrm-
pupsit/
44

Andrew Koch
Janmeet Anant
Andrew.Koch@EMDgroup.com
Janmeet.Anant@EMDgroup.com
Contact
© 2021 Merck KGaA, Darmstadt, Germany and/or its affiliates. All Rights Reserved.
Millipore, the vibrant M, and Millipak are trademarks of Merck KGaA, Darmstadt, Germany or its affiliates.
All other trademarks are the property of their respective owners. Detailed information on trademarks is available via publicly accessible
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