Validation of Sterilizing Grade Filters - ASQ Long Island Section

Validation of Sterilizing Grade FiltersPresented byLaura Okhio-SeamanSartorius Corporation1

Sterilizing Grade FiltersThe definition of a sterilizing grade filter is one that will produce a sterileeffluent after being challenged by microorganisms at a challenge level ofgreater than or equal to 1x10 7 /cm 2 of effective filtration area.2

Filter Qualification Tests‣ Physical Tests– Flow rates, differentialpressure, throughput– Sterilizability (SIP, Auto)– Integrity tests (bubble point,diffusive flow)‣ Biological Tests– Viability– Bacterial challenge test– Bioburden studies‣ Compendial Tests (USP,EP)– Particle release– Oxidizable substances–Biosafety– Endotoxin‣ Other Tests– Non-volatile residue– Quantitative and qualitativeextractables analyses inwater and ethanol– Leachables testing3

Validation of Sterilizing Grade Filters‣ Demonstrates the filter retains microorganisms toproduce a sterile filtrate‣ Ensures the filter does not alter the product in anobjectionable way‣ Ensures the product does not adversely affect thefilter – compatibility‣ Ensures the physical parameters of the process donot adversely affect the filter or the product4

Filter Qualification TestsViability5

Filter Qualification TestsBrevundimonas diminuta (ATCC 19146)Until the late 1960’s, 0.45 μm-rated membraneswere considered “sterilizing grade” filters, and wereused successfully in the sterilizing filtration of parenterals.In the mid-1960’s Dr. Frances Bowman observed a 0.45 μm“sterile-filtered” culture medium to be contaminated with amicro-organism, subsequently shown to penetrate 0.45 μm-ratedmembranes repeatedly in small numbers.6

Viability Test‣ Evaluation of potential bactericidal effects of the productsolution‣ Viability verified by direct inoculation into product andmaking serial dilutions‣ Test exposure time should equal or exceed actual processfiltration time‣ If less than a one-log reduction (LRV) is observed, productconsidered non-bactericidal‣ Greater than one-log reduction indicates product isbactericidal and alternatives should be considered7

Viability Test Examples8

Filter Qualification TestsBacterial Challenge9

Bacterial Challenge TestFilter Qualification by SupplierChallengeDocumentBacteria/Water SuspensionStand. Cond.Process-related Filter Validation by User/External LabChallengeDocumentProcess Cond.Bacteria/Product Suspension10

Bacterial Challenge TestFactors potentially affecting microbialretention include‣ Filter Construction (structure, membranepolymer, pore size distribution)‣ Formulation components‣ Formulation properties (pH, viscosity)‣ Process conditions (time, temperature, pressuredifferential, flow-rate)11

Bacterial Challenge TestMicrobial retention studies on filter devices:‣ Brevundimonas diminuta (ATCC 19146) has been provento penetrate a 0.45 μm rated filter‣ Spiking of the drug product with Brevundimonasdiminuta according to ASTM 838-05‣ Challenge level > 10 7 CFUs / cm 2 filtration area.‣ Validation Testing should simulate worst-case processconditions e.g., pressure differential, flow-rate, time,temperature12

Bacterial Challenge Test‣ Challenge suspension should be mono-dispersed to provide‘worst-case’ challenge‣ Optical microscopy is used to detect aggregation andclumping of bacteria‣ Ultrasonic treatment reduces aggregation‣ Penetration of 0.45 μm rated membranes is indicative ofsingle-cell conditions and this membrane is used as apositive control13

Bacterial Challenge TestMicroscopic investigationCriteria: single cells, motile cells0.6-1.0 μm0.3 -0.4 μmworst-case14

Bacterial Challenge Test‣ ASTM 838-05 (2005) uses B. diminuta as the standardchallenge organism‣ 2004 Aseptic Processing Guidance suggests the use of nativebioburden isolate when appropriate15

Bacterial Challenge TestMicrobiological challenge tests using one lot of low Bubble Point(close to manufacturer’s minimum specification) membranes shouldbe used. *Example:Minimum Bubble Point Value:Release criteria of filter vendor:Low BP Range:46 psi50 psi46 – 50.6 psi* At or near filter manufacturers minimum integrity test value (10%),1999 PDA / FDA Joint conference, PDA Newsletter December 199916

Filter Medium vs. Device‣ The purpose of the test is to validate the retention efficacyof a particular membrane material. A small 47mmmembrane disc can be used‣ To more closely simulate process conditions and todetermine the integrity of process filters, a small area 150or 300 cm 2 filter device capsule can be used‣ Full sized 10” filter cartridges require large volumes ofproduct (25-30 liters) to perform the challenge testing17

Recovery Membrane Selection‣ Either 0.45 or 0.2 micron-rated filter membrane can beused for recovery membranes‣ Studies indicate that 0.45 micron-rated membranes mightbe more efficient than 0.2 for this purpose‣ Cellulose Nitrate is the preferred membrane polymer –high affinity for proteins18

Pressure Differential and Flow Rate‣ Maximum process pressure differentials (P) across the filtershould be used in the challenge studies‣ Process flow-rate should be achieved in challenge studies‣ If pressure and flow rate cannot be simultaneously achieved,the user should determine which is more relevant and developa rationale to support the decision‣ Regulators tend to prefer higher pressure data rather thanflow-rate19

Manual BCT Set-uppressure gaugeventing valveventing valvevalvestest filtercapsulesanalyticaldisc filtersperistaltic pumpsyringe /sample collection20test solution /Brevundimonas diminutasuspension

BCT Set-up for Small Scale Pleated Filters21

22“Big Bertha” rigSartorius AG

Possible BCT StrategiesDetermine & Document viability of B. diminutain Product under Process ConditionsDirect inoculation of B. diminutain product under process conditionsVIABLEIsB. diminutaviable in product underprocess conditions?NOT VIABLEModify process(adjust temperatures, etc.)Modify formulation(adjust pH, remove bactericidalcomponent or product surrogate)Change from B. diminutaUse bacteria isolated fromformulation or environmentUse product for time period that thechallenge organism is viablePrecondition filter with Product– followed by Microbial Challenge23

BCT Strategies – Method 1(Direct Inoculation)Determine & Document viability of B. diminutain Product under Process ConditionsDirect inoculation of B. diminutain product under process conditionsVIABLEIsB. diminutaviable in product underprocess conditionsDirect inoculation of B. diminutain product under process conditions24

BCT Strategies – Method 1(Direct Inoculation)BCT by direct inoculation25

BCT Method 2(Process Modification)Determine & Document viability of B. diminutain Product under Process ConditionsDirect inoculation of B. diminutain product under process conditionsVIABLEIsB. diminutaviable in product underprocess conditions?NOT VIABLEModify process(adjust temperatures, etc.)Modify formulation(adjust pH, remove bactericidalcomponent or product surrogate)Change from B. diminutaUse bacteria isolated fromformulation or environmentUse product for time period that thechallenge organism is viablePrecondition filter with Product– followed by Microbial Challenge26

BCT Strategies – Method 2(Process Modification)‣ Temperature of ≥ 40°C supports mortalityrate of B. diminuta‣ Check viability of test bacteria in theproduct solution at lower temperatureDirect inoculation into product solutionmight be possible at 35°C27

BCT Strategies Method 3(Time Period Challenge)Determine & Document viability of B. diminutain Product under Process ConditionsDirect inoculation of B. diminutain product under process conditionsVIABLEIsB. diminutaviable in product underprocess conditions?NOT VIABLEModify process(adjust temperatures, etc.)Modify formulation(adjust pH, remove bactericidalcomponent or product surrogate)Change from B. diminutaUse bacteria isolated fromformulation or environmentUse product for time period that thechallenge organism is viablePrecondition filter with Product– followed by Microbial Challenge28

BCT Strategies – Method 3(Time Period Challenge)BCT by direct inoculation29Contact time bacteria / test solutionmax. 30 min.

BCT Strategies –Method 4(Formulation Modification)Determine & Document viability of B. diminutain Product under Process ConditionsDirect inoculation of B. diminutain product under process conditionsVIABLEIsB. diminutaviable in product underprocess conditions?NOT VIABLEModify process(adjust temperatures, etc.)Modify formulation(adjust pH, remove bactericidalcomponent or product surrogate)Change from B. diminutaUse bacteria isolated fromformulation or environmentUse product for time period that thechallenge organism is viablePrecondition filter with Product– followed by Microbial Challenge30

BCT Strategies –Method 5(Preconditioning)Determine & Document viability of B. diminutain Product under Process ConditionsDirect inoculation of B. diminutain product under process conditionsVIABLEIsB. diminutaviable in product underprocess conditions?NOT VIABLEModify process(adjust temperatures, etc.)Modify formulation(adjust pH, remove bactericidalcomponent or product surrogate)Change from B. diminutaUse bacteria isolated fromformulation or environmentUse product for time period that thechallenge organism is viablePrecondition filter with Product– followed by Microbial Challenge31

BCT Strategies – Method 5(Preconditioning)Indirect BCT by separate filtration oftest solution and bacteria32

BCT Strategies –Method 6(Bioburden Isolate)Determine & Document viability of B. diminutain Product under Process ConditionsDirect inoculation of B. diminutain product under process conditionsVIABLEIsB. diminutaviable in product underprocess conditions?NOT VIABLEModify process(adjust temperatures, etc.)Modify formulation(adjust pH, remove bactericidalcomponent or product surrogate)Change from B. diminutaUse bacteria isolated fromformulation or environmentUse product for time period that thechallenge organism is viablePrecondition filter with Product– followed by Microbial Challenge33

BCT Strategies –Method 6(Bioburden Isolate)BCT with bioburden isolate‣ Reproducible growth and size of bacteriais required‣ Growth in required concentration forBCT must be possible34

Filter Qualification TestsFilter Integrity35

Integrity Test CorrelationDestructive MethodsFor producers; applied todetermined limits:Bacteria-Challenge-Test(according to ASTM)Non-Destructive MethodsFor users; applied to everysterilizing filter before andafter each filtration:• Bubble Point Test• Diffusion Test• Multipoint Diffusion Test• Pressure Decay Test• Water Intrusion Test (WIT)Direct correlation of diffusion,bubble point, and intrusion-limitvalues to bacteria-challenge test.36

Integrity Test Correlation37

Bacterial Challenge Test38

Product Wet Integrity TestingBubble PointFilter membrane is wetted with the product. Pressure is applied on the upstreamside of the filter. The pressure at which a stream of air bubbles is detecteddownstream of the filter is known as the Minimum Bubble Point of the filter.INLET TUBING FROMPRESSURE SOURCEBP TESTPressure increase45.000 PSIPOWERCORDSARTOCHECK 3OUTLET TUBING45.000 psiN.I.S.T. TRACEABLEREFERENCEGAUGE BLIND END CAP39

Product Specific Integrity Test – Bubble Pointe.g.a b c46 psiPBPmin = 46 psi x 0.73PBPmin = 33.79 psixPBPavg/WBPavg36 psi/49 psiFlush with WaterTest a, b, cCalculate average, WBP avgFlush with ProductTest a, b, cPBPmin = WBPmin x Correction FactorCalculate average, PBP avg40

Product Wet Integrity TestingDiffusive FlowDepends mainly on the solubility of the test gas in the wetting fluid in additionto temperature and test pressure. The filter membrane pores are wetted withfluid and a gas pressure less than the BP is applied. Due to differential pressure,gas diffuses through the fluid in the pores and is quantified as downstream flowin mL/min.INLET TUBING FROMPRESSURE SOURCEPOWERCORDBP TESTPressure increase45.000 PSISARTOCHECK 3OUTLET TUBING45.000 psiGRADUATEDBURETTEN.I.S.T. TRACEABLEREFERENCEGAUGE BLIND END CAPNOTE: BEAKER AND INVERTEDBURETTE MAY BE SUBSTITUTEDWITH A N.I.S.T. TRACEABLE MASSFLOWMETER OR ROTAMETER.41

Product Specific Integrity Test – Diffusive Flowa b cFlush with Watere.g.15 ml/minDFL PW = 15 ml/min x 1.77xDFL PW = 26.5 ml/minDF PW /DF WW16 ml/min/9/9 ml/minTest a, b, c with MTP WWTP PW= MTP WWx PBP avg/WBP avgCalculate average, DF WWFlush with ProductTest a, b, c with TP PWCalculate average, DF PWDFL PW = DFL WW x Correction Factor42

Integrity Test FailureTR #26 includes a Trouble Shooting Guidein case of Integrity Test Failures:Determines when a filter has to be classified as failedFilter fails first time Measurements & ActionsFilter fails second time Wetting with solventFilter fails third time = Filter failed43

44Guidance

FDA Guidance on Aseptic Processing — CGMPFinal Guidance released onSeptember 29, 2004, whichreplaces the 1987 GuidanceDescribes the integrity testrequirements of liquid and airfilters, as well as the validationrequirements of liquid filters45

FDAPost approval Change Guidancefor chemical entities (Revision).Describes which changes infiltration steps are consideredmoderate (CBE 30) or major(Post Approval Supplement)changes.46

FDAWarning letters and inspectionguides are always good toreview – learn from themistakes and from the trainingListings are posted on FDA websiteas prescribed by the FOI Act.47

EC Guide to GMP of Sterile Medicinal ProductsEC cGMP Guidance,Revision of Annex 1.Describes sterilization byfiltration, integrity testneeds, some validationtopics.Important document to knowfor exporting.48

ISO: AP of Health Care Products — FiltrationReleased ISO Guidance, part 2. onfiltration.Describes filtration requirements,validation and integrity testneeds thoroughly for liquidand air filters.A good document to have, withthorough descriptions.49

PDAPDA Technical Report #26.The most thorough anddescriptive document onthe topic of liquidsterilizing filtration.This document is a must have,must read and mustunderstand as it is used byQC and regulatorsworldwide.50

ConclusionRegulatoryRequirementIndustryRequirementFilterValidationViability TestingBacterial Challenge TestingChemical CompatibilityAnalysis of ExtractablesProduct Integrity TestingPlant and Process SurveysSystems and Integrity TesterValidationProcess Related Validation Studies51

Validation of Sterilizing Grade FiltersEND52