Sterilization Process Validation Manual

Title: Sterilization Process Validation Manual Number: 039 Prepared by:

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Manual: 039 Sterilization Process Validation

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Purpose To provide guidelines for the validation of sterilization processes used in the manufacturing activities for drug products or active Pharmaceutical ingredients (API) and also to outline recommendations on how to achieve compliance.

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Scope and Applicability This Guideline is applicable to all manufacturing Operations, sites, functions and departments undertaking work, or providing support services, required to meet Good Manufacturing Practice (GMP) or, in the absence of a GMP standard, International Organization for Standardization (ISO) standards. This Guideline is applicable for sterilization processes used to produce sterile drug products, components, equipment and other ancillary items required to be sterile for use in the drug manufacturing process.

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Definitions

3.1

D value The time in minutes at a specific temperature required to reduce a surviving microbial population by 90%, i.e. a one-logarithm reduction.

3.2

F0 The time required at any given temperature between 100°C -140°C that is equivalent to the sterilization effect of steam at 121.1°C (250°F). Assumes a Z value of 10°C.

3.3

Z value The number of degrees Celsius required to change the D value by a factor of ten.

3.4

Sterile State being free from viable microorganisms. In practice no such absolute regarding the absence of microorganisms can be proven.

3.5

Sterilization Validated process used to render a product free of all forms of viable microorganisms. In a sterilization process, the nature of microbial death is described by an exponential function. Therefore, the presence of microorganisms on any individual item/container can be expressed in terms of probability. While the probability may be reduced to a very low number, it can never be reduced to zero.

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Overkill cycle A sterilization cycle that provides a 12-log reduction of a resistant Biological Indicator (BI) with a known D value of not less than 1 minute. A typical cycle would provide a minimum of 15 minutes at or above 121.1°C. This method is appropriate for heat stable products and 3

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Responsibilities All sterile manufacturing sites or its contractors are responsible for ensuring that sterilization processes used to produce items are properly validated.

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Guideline Validation of processes used to sterilize drug products and equipment are the most critical validation activities undertaken. Common elements in the validation of any sterilization process include: • Sterilization Cycle Development • Biological and Physical Measurement Controls • Empty Chamber Studies • Loaded Chamber Studies • Routine Use/Ongoing Monitoring • Validation Maintenance/Change Control/Revalidation The sterilization method chosen depends on the application. The following methods are typically available: Method Steam sterilization

Sterilization by filtration

Dry heat sterilization and Depyrogenation Radiation sterilization

5.1

Typical application For the sterilization of fluids in ampoules, vials etc, or the sterilization of processing equipment, reactors, preparation tanks, solution delivery piping, etc. In general, sterilization through the application of saturated steam under pressure is the preferred method of sterilization. The principles apply to SIP processes as well. Used for those products that cannot be sterilized due to the heat sensitivity of the product or where heat labile packaging is chosen since it provides a distinct patient benefit. Not the preferred sterilization method. Used to sterilize/depyrogenate containers (ampoules, vials, etc.), pharmaceutical raw materials and processing equipment. The use of dry heat has little application for the sterilization of pharmaceutical drug products. To sterilize packaging equipment, consumables, garments etc. that are difficult to sterilize using steam or other methods. Radiation sterilization is mostly used for medical devices.

Steam Sterilization Steam Sterilization is the most common type of sterilization employed in the pharmaceutical manufacturing environment. The principles of steam sterilization are applicable to processes conducted within autoclaves as well as sterilizationin-place (SIP) processes. For the sterilization of fluids in e.g. vials and ampoules, a fluids load autoclave cycle is used. The steam (or superheated water) is used as a heat transfer medium to heat the contents of the vials/ampoules. The moisture required for sterilization is derived from the contents in the vial/ampoule.

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degradation of the product does not occur. Product Specific Method The Product Specific Method (PSM) applies to sterilization cycles where an overkill approach is not possible because the product cannot withstand the temperatures and/or exposure times required for an overkill cycle. The PSM is more applicable to the validation of heat sensitive fluids, for example, where the sterilization cycle is developed to adequately destroy the microbial load and yet not result in product degradation. The PSM relies on determining the population and heat resistance of the environmental, product, or items-to-be-sterilized bioburden along with ongoing monitoring and control over the bioburden during routine operation. A PSM cycle would deliver less lethality than an overkill cycle, but would still deliver a Sterility Assurance Level of at least 10-6 (for the most heat resistant bioburden in the product). In the PSM, once the population of the overall bioburden and the heat resistance (generally only for spore-forming environmental or product/item isolates) has been determined, these values (plus additional safety margins based on professional judgment, the extent of the bioburden data, and the degree of product bioburden testing that will be conducted on an ongoing basis) are used to determine the lethality necessary to achieve a minimum SAL of 10-6.The safety margin selected inversely correlates to the frequency and magnitude of ongoing tests conducted for bioburden population and resistance. For example, if the observed worst-case product spore bioburden resistance is 0.3 minutes and, for lethality determination, a D-value of 0.4 minutes is selected, then extensive ongoing bioburden resistance testing would be necessary. However, if a D-value of 1.0 minute were selected for lethality determination, then minimal ongoing bioburden resistance testing would be necessary.Ongoing monitoring of bioburden population must be conducted. Once the bioburden data has been used to determine the lethality required for the PSM derived cycle, the attributes (population, resistance) of the BI challenge system can be determined. The semi-logarithmic survivor curve equation is used for determination of both the required cycle lethality and the attributes of the BI challenge. When the resulting log reduction for the BI challenge system is compared to the log reduction of the typical bioburden organism (whose D value is substantially less) the log reduction delivered for the actual bioburden is significantly higher than the demonstrated log reduction using the BI challenge system. The F-value for steam sterilization (F0) is a measurement tool used to demonstrate accumulated lethality and must be used in both validation and routine monitoring of cycles to demonstrate that acceptance criteria for F0 has been met. For terminally sterilized drug products validated using the PSM approach, reductions in cycle parameter set points during the validation are less common. Terminally sterilized drug product cycles generally include an upper limit for the 7

minute of the exposure stage. The difference between the control probe, recording chart probe and independent sensor (usually a thermocouple) during the exposure stage should not exceed + 1.0°C.

5.1.1.2 Loaded Chamber Temperature Distribution This study must be included to demonstrate that the equipment loading patterns do not significantly change the chamber temperature distribution within the chamber. Typically thermocouples are distributed throughout the chamber (not in contact with load items) as for the Empty Chamber Temperature Distribution study and cycles may be run using both the maximum and minimum loads. Loaded Chamber Temperature Distribution studies should meet an acceptance criteria for the temperature to be within + 1°C of the mean loaded chamber temperature after one minute of the exposure stage. The difference between the control probe, recording chart probe and independent sensor during the exposure stage should not exceed + 1.0°C. 5.1.1.3 Heat Penetration Studies Loaded chamber heat penetration studies must be performed to demonstrate that the pre-required time at temperature criteria are met for the loads being validated. The heat penetration locations to be monitored are assessed using both temperature probes and BIs. The thermocouples and the BIs should be placed at the same locations wherever possible. Special emphasis is placed on those locations identified during cycle development studies as being difficult for steam to penetrate/difficult to heat (cold spot determination). Such locations typically include the interior of hoses, filter housings, large objects, filling apparatus and items with multiple layers of protective wrapping. The placement of temperature probes and BIs within the load must not enhance the penetration of steam into the load item. Where the load includes multiple items of the same configuration in the load (e.g. bags of stoppers), BIs should be placed in a second item adjacent to that containing the thermocouple. This is to prevent the presence of the thermocouple from enhancing the penetration of steam to the BI.Where items in the load are unique, the BIs must be placed in the load item near the probe and precautions taken to prevent enhanced steam penetration. Heat penetration cycles performed, as part of an initial validation exercise must be repeated several times, e.g. three times,to demonstrate consistency. These studies should be performed using established load patterns, though a minimum and maximum load may be used to represent each particular load pattern for qualification purposes. The purpose of the heat penetration study is to document that the load items (including the cold spot) receives the minimum required pre-determined time at temperature/F0.

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a load cold spot due to the relatively uniform temperature rise across the load. Using defined maximum and minimum load patterns may be useful in elucidating the presence of a product load cold spot. Once the container and product load cold spots (if any) have been determined, consistency of the cycle must be demonstrated by repeat runs with temperature probes and BIs located at the container and load cold spots. The purpose of consistency study is to document that any load or container cold spot receives the minimum required pre-determined F0and/or time at temperature.

5.1.3 Demonstrating Biological Lethality of the Cycle The use of BIs to demonstrate biological lethality must be included in both porous (equipment or hard goods) cycles and fluids load cycles, whether validating using the overkill cycle method or the PSM. BIs used in steam sterilization are bacterial spores, typically Geobacillus stearothermophilus, having a defined heat resistance that is significantly greater than the native bioburden of the items/product to be sterilized. For PSM cycles, other BI challenge systems such asClostridium sporogenes, Bacillus coagulans or Bacillus atropheus may be used. BIs provide a direct measure of biological lethality and allow the targeted placement of highly heat resistant microorganisms in situ. BIs respond to both heat and moisture and therefore provide proof that the required sterilizing conditions have been achieved (temperature probes alone cannot do this).

The destruction of large numbers of these resistant organisms supports the efficacy of the sterilization process for the total destruction of any native bioburden organisms present. BIs are available commercially as pre-prepared spore strips or coupons, self- contained units, or as spore suspensions. The heat resistance of BIs is characterized by the specific Dvalue and Z-value for the preparation determined under defined conditions. Spore strips or coupons should be placed within the load at locations where steam penetration is deemed to be most difficult (sometimes referred to as the ‘cold spot’). The manufacturer of the strips, coupons or self-contained unit provides information on the number of organisms present on the inoculated carrier (population) and an expected resistance level (D-value) under defined conditions. Spore strips or coupons should only be stored, used and incubated as directed by the manufacturer. They should never be immersed in liquid or altered or abused in any way with since this may dramatically change their resistance from the labeled value. The end user should verify the population of commercially obtained spore strips or coupons. Self-contained Bis include both the organism and the culture media in a single unit. The end user positions the BI in the load, runs the cycle, recovers the unit and then incubates according to the manufacturer’s instructions. Where these units are used in accordance with the manufacturer’s instructions, the population and D-value provided may be used directly, though it is good practice to determine the population as part of the quality control of these units. Spore suspensions can be used to directly inoculate items to be sterilized. The suspension is 11

In addition, it is common to use a second sterilizing grade filter immediately before final filling. The manufacturing process must be designed to minimize the pre filtration bioburden. Products that are subject to microbial proliferation should be held for as short a time as possible. If long holding times are anticipated consider the options of sterile filtering the solution into a sterile holding tank or holding the product in either a chilled or a heated state to reduce the probability of an increased bioburden. Sterile holding tanks and any contained liquids must be held under positive pressure or appropriately sealed to prevent microbial contamination. Filtration validation should be product-specific. The use of a “matrix approach” or “family approach” allowing grouping of products or the selection of a worstcase product to represent a number of products is discouraged due to the extensive justification needed. Even with such justification, the acceptance by regulatory authorities would be on a case-by-case basis and in the absence of any official guidance for industry. All sterilizing grade filters must be integrity tested before use (preferably after sterilization) and then again following use. The integrity test parameters must be clearly defined and, along with the test limits, be correlated to the microbial validation of the filter.

5.3.1 Validation of Filtration Process The validation of sterile filtration processes must demonstrate microbial retention as well as filter compatibility and filter extractable relative to the solution being sterilized. The microbial retention studies required are highly specialized and the industry in general, contract this work out to the laboratories of the filter manufacturers. Filtration validation is process specific and process parameters must be provided to the filter manufacturer in order to assure that the laboratorybased validation conditions reflect both actual and elements of worst-case use conditions in our facilities. Filters must never be subjected to conditions beyond those mandated by the filter manufacturer. Process parameters such as pressures, maximum use time, hydraulic shock, flow rates etc. as well as product solution characteristics such as pH, temperature, osmolarity, etc. are some of the parameters that must be factored into the validation exercise. While the actual work to validate microbial retention may be contracted out, the responsibility for the validation lies with the sponsor company .A copy of the validation documentation must be held at the sponsor site.

5.3.2 Microbial Retention Test Sterilizing grade filters must pass a microbial retention test using Brevundimonas diminuta as the challenge organism. The requirements for culturing the organism as well as the conditions of the test are rigorous and highly specialized. It is particularly important to perform this test by directly inoculating 13

5.4

Dry Heat Sterilization and Depyrogenation Dry heat sterilization processes are typically used for equipment parts while dry heat-based depyrogenation processes are used for glass containers for drug products. Dry heat sterilization and depyrogenation can be performed in ‘batch’ dry heat ovens or continuous sterilizing tunnels. Rubber closures are also subject to a validated depyrogenation process using a washing/rinsing process - See section 5.3.4 below). There is limited use for dry heat in sterilizing drug products, though raw materials are sometimes sterilized using dry heat. The validation of these dry heat based cycles follows many of the general principles outlined for steam sterilization. Concepts such as equilibration time, temperature mapping, heat penetration, biological lethality and worst-case cycle parameters (shortened times, lower temperatures, faster belt speeds, etc.) are relevant, though in a different context. It is common practice to determine FH values for dry heat processes in a similar manner to F0 for steam sterilization. However, most applications of dry heat are to depyrogenate and not just to sterilize. The depyrogenation process is not as well understood as the sterilization process. Some evidence indicates that inactivation of endotoxin is a second-order reaction whereas the standard use of FH, D and Z values assumes a single-order reaction. Therefore for depyrogenation cycles there is even more reliance on the biological proof (inactivation of endotoxin) as opposed to only the accumulation of physical data. Even with these limitations it is valuable to collect the FH data to demonstrate reproducibility. The temperature range allowed in both empty and loaded chamber studies for dry heat cycles is significantly greater than for steam sterilization. In particular, for empty chamber studies, USP 29 states that ± 15ºC is a typical acceptable temperature range when the oven is operating at not less than 250ºC. For loaded chamber studies, a ± 5ºC temperature range is generally achievable. Depyrogenation processes must be validated to achieve a minimum 3-log reduction of bacterial endotoxin. The endotoxin must be spiked onto the item in a liquid state and allowed to air dry prior to being subject to the depyrogenation cycle. Recovery studies and appropriate controls are a necessary part of these studies.

5.4.1 Dry Heat Ovens The validation of a dry heat process in an oven, whether it is used for sterilization or depyrogenation, is similar to the validation of a steam sterilization process. Biological indicators, typically Bacillus atrophaeus spores (for sterilization processes) or bacterial endotoxin (for depyrogenation processes) must be used in conjunction with temperature measurements. A successful endotoxin challenge in the validation of a depyrogenation process assures that sterilization has also occurred and there is no need for additional studies with bacterial spores. The load size and configuration are very important in dry heat processing. These must be carefully designed and duplicated between the validation studies and routine operation.

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Blowers/Fans - for proper air balance and the differential pressure between the tunnel and the room environment Room pressure differentials 5.4.2.1 Empty Tunnel Temperature Distribution Temperature probes (thermocouples) are distributed across the width of the tunnel and a temperature profile is produced across the conveyor and along the tunnel during operation. A reasonably uniform temperature profile is expected. A probe needs to be located next to the controlling sensor. Note the come-up time to temperature and cool-down times, as these should be consistent in an empty tunnel. 5.4.2.2 Loaded Chamber Heat Penetration In dry heat tunnel applications heat penetration studies must be performed. Thermocouples must be placed in contact with vials distributed across the tunnel. The temperature of the vial is usually lower than the air temperature. Test should be performed with all vial sizes. Endotoxin spiked vials should be located adjacent to the penetration thermocouples. Heat penetration studies, conducted as part of the initial validation, must be repeated several times (e.g. three times) to demonstrate consistency. Consider the loading arrangement of the tunnel i.e. at the start, middle and end of a run. The temperature profile for a specific load should show good reproducibility. 5.4.3 Demonstrating Biological Lethality The use of BIs to demonstrate biological lethality must be included in the validation approach. For dry heat sterilization the indicator of choice is Bacillus atrophaeusspores. However, dry heat is also used to depyrogenate. In this case endotoxin (E. coli) is used to validate the depyrogenation activity. If endotoxin is used then Bacillus atrophaeusspore strips are not required as endotoxin is more heat resistant than Bacillus atrophaeus. These biological studies can be performed at the same time as the loaded chamber temperature mapping. If this is done the carriers should be located as close as possible to the thermocouples. 5.4.4 Washing Process for Depyrogenation In some cases, the depyrogenation of items that cannot be dry heat sterilised (e.g. rubber stoppers) is carried out in a washing/rinsing process. It must be demonstrated that a 3-log reduction in the endotoxin concentration on spiked stoppers can be achieved. Recovery studies on the spiked stoppers must be performed. The stoppers must be subsequently sterilized using a validated steam sterilization cycle.

5.5

Radiation Sterilization

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5.6

Validation Maintenance/Change Control/Revalidation Validation of sterilization processes is not a one-time exercise. Validation maintenance is a phrase that describes a number of activities that support the ongoing validated state of a process. In the case of sterilization processes, routine bioburden monitoring, preventive maintenance, calibration, cycle review and approval and annual reviews are activities that make up validation maintenance. Bioburden monitoring must take place for every batch of aseptically produced drug product. The preventive maintenance program should provide clear instructions on reporting any unusual observations or equipment breakdowns/mechanical failures so that an evaluation can be made on impact to the validated state. Cycle review and approval should be in accordance with detailed SOPs that have a direct traceability to the qualification and validation activities, set point parameters and acceptance ranges. Chamber vacuum leak testing, air detector device performance (if so equipped), Bowie-Dick type testing for steam penetration, thermometric testing for small loads, and other types of testing or review that may be required by local regulatory authority expectation or requirement should be understood and implemented as appropriate. For example, steam quality testing is a requirement of the UK authorities. These tests are also mentioned in the PDA Technical Monograph #1 and FDA’s Guideline on Drug Products Produced By Aseptic Processing. The change control program should ensure that technical experts and the Quality Assurance Function assess any planned changes to the equipment, process, loads, procedures or documentation as to whether the qualified or validated state may be impacted by the change. Any additional work necessary to demonstrate the ongoing validated state should be reviewed and approved as part of the change control process. Sterilization processes are critical processes. Be vigilant in assuring that any changes or repairs are fully assessed for potential impact via the change control process. Perform a periodic assessment of the potential cumulative effect of changes that individually may not be significant enough to prompt revalidation but, taken together, indicate a need to re qualify or revalidate. Sterilization processes must be revalidated at least annually in the absence of any change-driven revalidation. The revalidation can be a subset of the original validation work. Some acceptable approaches include: • • •

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Single runs rather than 3 consecutive runs are sufficient in the absence of recurring problems The selection of a worst case load pattern for revalidation The revalidation of each type of cycle (e.g. cycle for stoppers, cycle for filling parts, cycle for products, etc.) but not the revalidation of each cycle loading pattern. The revalidation of the worst case loading pattern and one selected loading pattern, with the rotation of the remaining loading patterns at subsequent annual revalidations. The revalidation of the empty chamber, maximum and minimum loading 19