VALIDATION OF ASEPTIC PROCESSING AS PER USFDA GUIDELINE
Process Simulations
To ensure the sterility of products purporting to be sterile, sterilization, aseptic filling, and closing operations must be adequately validated (§ 211.113).
The goal of even the most effective sterilization processes can fail to achieve their objective if the sterilized components of a product, such as a drug formulation, container, and closure, are combined in conditions that result in contamination of any of these elements.
An aseptic processing operation should be validated using a microbiological growth medium in place of the product. This process simulation, also known as a media fill, normally includes exposing the microbiological growth medium to product contact surfaces of equipment, container closure systems, critical environments, and process manipulations to closely simulate the same exposure that the product itself will undergo. The sealed containers filled with the medium are then incubated to detect microbial contamination. Results are then interpreted to assess the potential for a unit of drug product to become contaminated during actual operations (e.g., start-up, sterile ingredient additions, aseptic connections, filling, closing). Environmental monitoring data from the process simulation can also provide useful information for the processing line evaluation.
1. Study Design of Process Simulations
A media fill program should incorporate the contamination risk factors that occur on a production line, and accurately assess the state of process control. Media fill studies should closely simulate aseptic manufacturing operations incorporating, as appropriate, worst-case activities and conditions that pose a challenge to aseptic operations. FDA recommends that the media fill program address applicable issues such as:
- Factors associated with the longest permitted run on the processing line that can pose
contamination risk (e.g., operator fatigue) - Representative number, type, and complexity of normal interventions that occur with each run, as well as nonroutine interventions and events (e.g., maintenance, stoppages, equipment adjustments)
- Lyophilization, when applicable
- Aseptic assembly of equipment (e.g., at start-up, during processing)
- Number of personnel and their activities
- A representative number of aseptic additions (e.g., charging containers and closures as well as sterile ingredients) or transfers
- Shift changes, breaks, and gown changes (when applicable)
- Type of aseptic equipment disconnections/connections
- Aseptic sample collections
- Line speed and configuration
- Weight checks
- Container closure systems (e.g., sizes, type, compatibility with equipment)
- Specific provisions in written procedures relating to aseptic processing (e.g.,conditions permitted before line clearance is mandated)
A written batch record, documenting production conditions and simulated activities, should be prepared for each media fill run. The same level of attentiveness should be observed in both media fill and routine production runs. The firm’s rationale for the conditions and activities simulated during the media fill should be clearly defined. Media fills should not be used to justify practices that pose unnecessary contamination risks.
2. Frequency and Number of Runs
When a processing line is initially qualified, individual media fills should be repeated enough times to ensure that results are consistent and meaningful. This approach is important because a single run can be inconclusive, while multiple runs with divergent results signal a process that is not in control. We recommend that at least three consecutive separate successful runs be performed during initial line qualification.
Subsequently, routine semi-annual qualifications conducted for each processing line will evaluate the state of control of the aseptic process.
Activities and interventions representative of each shift, and shift changeover, should be incorporated into the design of the semi-annual qualification program.
For example, the evaluation of a production shift should address its unique time-related and operational features.
All personnel who are authorized to enter the aseptic processing room during manufacturing, including technicians and maintenance personnel, should participate in a media fill at least once a year. Participation should be consistent with the nature of each operator’s duties during routine production.
Each change to a product or line change should be evaluated using a written change control system. Any changes or events that have the potential to affect the ability of the aseptic process to exclude contamination from the sterilized product should be assessed through additional media fills.
For example, facility and equipment modifications, line configuration changes, significant personnel changes, anomalies in environmental testing results, container closure system changes, extended shutdowns, or end product sterility testing showing contaminated products may be cause for revalidation of the system.
When data from a media fill indicate the process may not be in control, an investigation should be conducted to determine the origin of the contamination and the scope of the problem. Once corrections are instituted, process simulation run(s) should be performed to confirm that deficiencies have been corrected and the process has returned to a state of control. When an investigation fails to reach well-supported, substantive conclusions as to the cause of the media fill failure, three consecutive successful runs in tandem with increased scrutiny of the production process may be warranted.
Duration of Process Simulations Runs
The duration required for aseptic processing activities is a major factor to consider when designing media fill design. While the most accurate simulation model would involve using the complete batch size and duration, as it closely mimics/simulates the actual production processes, alternative models can also be justified.
The duration of the media fill run should be established based on the duration required to include manipulations and interventions, along with careful consideration of the actual aseptic processing operation’s duration. Interventions that commonly occur should be routinely simulated, while those occurring rarely can be simulated periodically.
Although most conventional manufacturing lines are automated and operate at high speeds to minimize operator intervention, certain processes still require significant involvement from operators. For instance, in aseptic processing, when manual filling or closing, as well as extensive manual manipulations, are involved, it is recommended that the duration of the process simulation matches the length of the actual manufacturing process. This ensures a more accurate simulation of the contamination risks posed by operators.
The FDA advises that during lyophilization procedures, it is recommended that unsealed containers to a partial evacuation of the chamber, mimicking the actual process. It is important to note that vials should not be frozen, and necessary precautions should be implemented to maintain an aerobic environment for the medium, thus preventing any potential inhibition of microorganism growth.
Size of Process Simulations
The simulation run sizes must be sufficient to replicate the conditions of commercial production and accurately assess the possibility of commercial batch contamination. The number of units filled during the simulation process should be based on the risk of contamination associated with a specific process, and it should be enough to accurately simulate activities that are representative of the manufacturing process.
A generally acceptable run size is typically between 5,000 and 10,000 units. In cases where the production size falls below 5,000 units, it is recommended that the number of media-filled units be equal to or greater than the largest batch size produced on the processing line.
When the possibility of contamination is higher due to the process design, such as manually intensive filling lines, it is recommended to use a larger number of units, typically equal to or approaching the full production batch size.
On the other hand, a procedure carried out within an isolator can have a low risk of contamination due to the absence of direct human involvement and can be simulated using a smaller number of units as a proportion of the overall operation.
Media fill size is an especially important consideration because some batches are produced over
multiple shifts or yield an unusually large number of units. These factors should be carefully
evaluated when designing the simulation to adequately encompass conditions and any potential
risks associated with the larger operation.
Media fill size is an especially important consideration because some batches are produced over multiple shifts or yield an unusually large number of units. These factors should be carefully evaluated when designing the simulation to adequately encompass conditions and any potential risks associated with the larger operation.
Line Speed
The media fill program must effectively address the range of line speeds used in production. Each media fill run should assess a specific line speed, and the chosen speed should be justified. For instance, the use of high line speed is often suitable when evaluating manufacturing processes that involve frequent interventions or a significant amount of manual manipulation. On the other hand, a slow line speed is generally appropriate for evaluating manufacturing processes that involve prolonged exposure of the sterile drug product and containers/closures in the aseptic area.
Environmental Conditions
Media fills must accurately reflect the conditions in which actual manufacturing operations take place. An inaccurate assessment (making the process appear cleaner than it is) can result from conducting a media fill under extraordinary air particulate and microbial quality, or under production controls and precautions taken in preparation for the media fill.
To the extent standard operating procedures permit stressful conditions (e.g., maximum number of personnel present and elevated activity level), media must include analogous challenges to support the validity of these studies.
Stressful conditions do not include artificially created environmental extremes, such as reconfiguration of HVAC systems to operate at worst-case limits.
Media
Typically, it is recommended to use a microbiological growth medium, such as soybean casein digest medium. However, in specific situations, it is advisable to consider the use of anaerobic growth media, such as a fluid thioglycollate medium.
The media selected should be demonstrated to promote the growth of gram-positive and gram-negative bacteria, and yeast and mold (e.g., USP indicator organisms).
The QC laboratory should determine if USP indicator organisms sufficiently represent production-related isolates. Environmental monitoring and sterility test isolates can be substituted (as appropriate) or added to the growth promotion challenge. Growth promotion units should be inoculated with a <100 CFU challenge. If the growth promotion testing fails, the origin of any contamination found during the simulation should nonetheless be investigated and the media fill promptly be repeated.
The production process should be accurately simulated using media and conditions that optimize the detection of any microbiological contamination. Each unit should be filled with an appropriate quantity and type of microbial growth medium to contact the inner container closure surfaces (when the unit is inverted or thoroughly swirled) and permit visual detection of microbial growth.
Some pharmaceutical companies have raised concerns regarding the potential contamination of their facility and equipment with nutrient media during media fill runs. Nevertheless, if the medium is managed appropriately and promptly followed by thorough cleaning, sanitization, and, if required, equipment sterilization, the integrity of the subsequently processed products is unlikely to be compromised.
Incubation and Examination of Media-Filled Units
Media units need to be incubated in conditions that are suitable for detecting microorganisms that may be difficult to culture. The establishment of incubation conditions should align with the following following general guidelines:
The incubation temperature must be appropriate for the retrieval of bioburden and environmental isolates, and it should never exceed or fall below the range of 20-35ºC. Additionally, it is crucial to ensure that the incubation temperature remains within a tolerance of +2.5ºC from the desired temperature.
The minimum duration for incubation should be 14 days. In case two different temperatures are employed for incubating the media-filled units, it is necessary to incubate the units for a minimum of 7 days at each temperature, starting with the lower temperature.
Each media-filled unit should be examined for contamination by personnel with appropriate education, training, and experience in inspecting media-fill units for microbiological contamination. If QC personnel do not perform the inspection, there should be QC unit oversight throughout any such examination. All suspect units identified during the examination should be brought to the immediate attention of the QC microbiologist.
To allow for visual detection of microbial growth, we recommend substituting clear containers (with otherwise
identical physical properties) for amber or other opaque containers. If appropriate, other methods can also be considered to ensure visual detection.
When a firm performs a final product inspection of units immediately following the media fill run, all integral units should proceed to incubation. Units found to have defects not related to integrity (e.g., cosmetic defect) should be incubated; units that lack integrity should be rejected. Erroneously rejected units should be returned promptly for incubation with the media fill lot.
After incubation is underway, any unit found to be damaged should be included in the data for the media fill run, because the units can be representative of drug products released to the market.
Any decision to exclude such incubated units (i.e., non-integral) from the final run tally should be fully justified and the deviation explained in the media fill report. If a correlation emerges between difficult-to-detect damage and microbial contamination, a thorough investigation should be conducted to determine its cause.
Written procedures regarding aseptic interventions should be clear and specific (e.g., intervention type; quantity of units removed), providing for consistent production practices and assessment of these practices during media fills. If written procedures and batch documentation are adequate to describe an associated clearance, the intervention units removed during media fills do not need to be incubated.
Where procedures lack specificity, there would be insufficient justification for the exclusion of units removed during an intervention from incubation. For example, if a production procedure requires the removal of 10 units after intervention at the stoppering station infeed, batch records (i.e., for production and media fills) should clearly document conformance with this procedure. In no case should more units be removed during a media fill intervention than would be cleared during a production run.
The ability of a media fill run to detect potential contamination from a given simulated activity should not be compromised by a large-scale line clearance. We recommend incorporating appropriate study provisions to avoid and address a large line clearance that results in the removal of a unit possibly contaminated during an unrelated event or intervention.
Appropriate criteria should be established for yield16 and accountability (reconciliation of filled units). Media fill record reconciliation documentation should include a full accounting and description of units rejected from a batch.
Also read -Air Filtration by Membrane
Interpretation of Test Results
The process simulation run should be observed by the QC Unit, and contaminated units should be reconcilable with the approximate time and the activity being simulated during the media fill.
Video recording of a media fill may serve as a useful aid in identifying personnel practices that could negatively affect the aseptic process.
Any contaminated unit should be considered objectionable and investigated. The microorganisms should be identified at the species level. The investigation should survey the possible causes of contamination. In addition, any failure investigation should assess the impact on commercial drugs produced on the line since the last media fill.
Whenever contamination exists in a media fill run, it should be considered indicative of a potential sterility assurance problem, regardless of run size. The number of contaminated units should not be expected to increase in a directly proportional manner to the number of vials in the media fill run.
Test results should reliably and reproducibly show that the units produced by an aseptic processing operation are sterile. Modern aseptic processing operations suitably designed facilities have demonstrated a capability of meeting contamination levels approaching zero and should normally yield no media fill contamination. Recommended criteria for assessing the state of aseptic line control are as follows:
When filling fewer than 5000 units, no contaminated units should be detected.
One (1) contaminated unit is considered a cause for revalidation, following an investigation.
When filling from 5,000 to 10,000 units:
One (1) contaminated unit should result in an investigation, including consideration of a repeat media fill.
Two (2) contaminated units are considered cause for revalidation, following investigation.
When filling more than 10,000 units:
One (1) contaminated unit should result in an investigation.
Two (2) contaminated units are considered cause for revalidation, following investigation.
For any run size, intermittent incidents of microbial contamination in media-filled runs can be indicative of a persistent low-level contamination problem that should be investigated.
Accordingly, recurring incidents of contaminated units in media fill for an individual line, regardless of acceptance criteria, would be a signal of an adverse trend in the aseptic processing line that should lead to problem identification, correction, and revalidation.
A firm’s use of media fill acceptance criteria allowing infrequent contamination does not mean that a distributed lot of drug product purporting to be sterile may contain a nonsterile unit. The purpose of an aseptic process is to prevent any contamination.
A manufacturer is fully liable for the shipment of any nonsterile unit, an act that is prohibited under the FD&C Act (Section 301(a) 21 U.S.C. 331(a)). FDA also recognizes that there might be some scientific and technical
limitations on how precisely and accurately process simulations can characterize a system of controls intended to exclude contamination.
As with any process validation run, it is important to note that invalidation of a media fill run should be a rare occurrence. A media fill run should be aborted only under circumstances in which written procedures require commercial lots to be equally handled. Supporting documentation and justification should be provided in such cases.
