Applying Quality by Design to Sterile Manufacturing Processes 3

By: Warren Charlton
Technology transfer
Assuming that the manufacturing process design space has been properly developed and CQAs and DOEs have been verified, technology transfer, as well as scale-up, should go smoothly. As with most typical API-manufacturing operations, process design and controls ensure a state of control. When these approaches and technologies are applied to a batch-based system, they may, in the future, lead to more continuous sterile processing due to the increased level of control.
The following sterile-process technologies are well defined in the literature: sterile filtration (F), autoclaves (A), steam cycles, dry-heat (DH) ovens and tunnels, gas sterilization (ETO), chlorine dioxide (ClO₂), ionization radiation (ebeam, gamma), and terminal sterilization (steam, gamma radiation). These technologies must be validated with the specific component, drug product, or commodity.
Sterilization technology review. Sterile filtration. Filter validation is normally done by filter manufacturers or outside laboratories but the responsibility remains with the drug manufacturer (5). Steam sterilization. Steam sterilization (i.e., autoclaves, sterilize-in-place [SIP]), is the method of choice whenever possible due to data available and capability to assure sterility. This method is used for transfers into the aseptic area, process sterilization, SIP of the product delivery system, and product contact-component sterilization. Steam sterilization is limited by its temperature and pressure impact. Many plastic items, therefore, require other methods of sterilization. Control is typically ≥121.1 °C. Product contact components must have had prior pyrogen removal steps to ensure expectation of a minimum 3-log reduction.
Dry-heat sterilization. The DH approach is mainly used for glass components because of the temperature during processing (a dry-heat oven is typically controlled ≥200–250 °F and dry-heat tunnels are typically controlled at 275–350 °F). Dry-heat sterilization can also be validated for a 3-log or greater pyrogen reduction.
ETO. Gas sterilization or ETO, is used for product contact plastics and commodity transfers. The method is not used in processes and operations due to safety issues. Product contact components require ETO degassing after the cycle is completed. ETO is a toxic and hazardous chemical. Cycle control includes ETO concentration, humidity, and pressure and similar to steam sterilization, requires prior pyrogen removal steps.
Ebeam. Ebeam is easy to define and makes it easy to control sterilization of the surface and, to some extent, the depth of exposure and microbial kill. Recently, the ebeam method has been used to sterilize the lids of syringe bulk containers before filling. Because ebeam is not currently used for product contact components, pyrogens are not an issue. The sterilization dose for radiation processes (i.e., ebeam and gamma) are 25 kGy (2.5 Mrad).
Vaporized hydrogen peroxide (VHP). VHP is currently the method of choice for isolator decontamination. Sterility is sometimes claimed. Because VHP is not a true gas, it can be affected by cold spots. VHP also can be used to sanitize transfer items into aseptic-filling operations, but cannot be used to sterilize or depyrogenate components. Cycle requires control of concentration of H₂O₂, relative humidity, and temperature. Circulation fans within an isolator are often used to help provide constant conditions within the isolator (5).
Chlorine Dioxide (CD). CD is currently the least used method throughout industry for sterilization, but provides significant opportunities because it is a true gas and can be validated for sterility. Areas of opportunity include isolators, transfers to the aseptic area, and processing equipment. CD is widely used in the food industry for sanitization and disinfection. Concentration can be monitored and controlled. Aeration is repeatable. Passivation of stainless steel may be required. Controls consists of concentration, humidity, temperature, and pressure.
Other sterilization technologies include gamma radiation, which is used for product terminal sterilization and component sterilization by contract manufacturing organizations (CMOs). Gamma-radiated presterilized syringes are a common usage of this technology in the industry. Transfer of these types of presterilized components to aseptic-filling areas can be troublesome, however, without a defined transfer sterilization method. Recently, some equipment suppliers have included ebeam sterilization to improve this transfer. Ozone (O₃) technology has potential as a sterilization method as well, but is not currently commercially available. Peracetic acid as a sterilization technology may still be used by a few companies, but most have switched to VHP. Other forms of sterilization or environmental control have limited support data and therefore represent an increased risk requiring in-house technical knowledge (e.g., high-intensity light, ultraviolet light).

Applying Quality by Design to Sterile Manufacturing Processes 2

By: Warren Charlton
Design of experiment and risk analysis. Design of experiment (DOE) and risk analysis are recommended in the draft guidance to provide data that support process design. The emphasis should be to reveal relationships between variable inputs (e.g., component characteristics, processing parameters) and resulting outputs (e.g., in-process material, intermediates, or the final product).
Early-stage product assurance. The draft guidance states "early process design experiments do not need to be performed under CGMP conditions." Emphasis during early stage development are verification rather than validation. "Decisions and justifications of the controls should be sufficiently documented and internally reviewed," according to the draft guidance. Some examples of early-stage product assurance are outlined below (4, 5).

• Viral and impurity clearance studies are required because they have a direct impact on product quality
• Cleaning verification would replace validation during the early stages of development
• Sterility must be ensured but may not be completely validated (e.g., if performing sterile filtration on a water-based product, a filter integrity test may be performed using water-for-injection to demonstrate that the filter still meets its manufacturer's integrity test value)
• Preliminary specifications, tests, acceptance criteria, and limits should be operational.

Overall, the further along a company is in its product development, the more verification and validation are expected. Process controls that address variability can help to ensure the product's quality. Models. "It is important to understand the degree to which models represent the commercial process including differences that may exist," states the guidance (4). The significance of understanding the process increases with a model that properly reflects all the variants of the process and product. A good model can be used as a tool for process and equipment design, process control development, estimating variablity, and training personnel.
Process analytical technology and qualification. Process analytical technology (PAT) "uses timely analysis and control loops to adjust processing conditions so that the output remains constant," states the guidance (4). As a result, there is a higher degree of process control. It is unclear, however, whether maintaining the process within the design space using PAT reduces process-validation testing. The draft guidance places added emphasis on design (qualification = design plus verification). There are requirements, for example, to challenge the process under load, to test interventions, and to test stoppage and start-up routines as expected for production.
The common industry practice of testing three batches for PQ may no longer apply. Specific requirements regarding when batches can be released and the information needed to begin commercial distribution are included in the draft guidance. PQ must have a higher level of sampling, testing, and scrutiny of process performance to confirm the product's quality during batch processing.
According to the draft guidance, "In the case of PAT strategy, the approach to process qualification will be different from that for other process designs," but the agency did not explain how the process will be different (4). This difference is important because additional use of PAT leads to additional validation to verify the technology's capability. Industy will assume this means an easier validation approach because conformation of control would be readily available, but there are no examples provided in the draft guidance.
With regard to continued process verification, the goal is to ensure the process remains in a state of control during commercial operations (3, 4). The draft guidance recommends manufacturers include intra-batch as well as inter-batch variation as part of their continued verification program. PQ sampling levels should continue until variability is assessed.
The draft guidance suggests that a statistician be involved in the development of the company's data collection plan and in the selection of statistical methods to evaluate process stability and capability. Included in this review should be quantitative statistical methods where feasible. Process flow diagrams for commercial manufacturing, for example, should be completed as follows:

• Describe each unit operation and placement in the process
• Describe process monitoring and control points
• Describe components and other processing material inputs
• Describe expected outputs (e.g., in-process and finished products).

In addition, the flow diagrams should preserve a life-cycle approach to facilitate comparison and decision-making regarding their comparability.

Applying Quality by Design to Sterile Manufacturing Processes 1

By: Warren Charlton
In November 2008, the US Food and Drug Administration issued a much needed document titled, Draft Guidance for Industry on Process Validation: General Principles and Practices. The draft guidance clarifies the quality-by-design (QbD) approach to processing human and veterinary drugs, including biologics, active pharmaceutical ingredients (APIs), and medical devices. Although the document may have been better titled "process design," it has addressed many industry concerns regarding how to take a life-cycle approach and how to meet regulatory expectations with regard to validation. Many questions still remain, however, and industry must grasp and integrate the proposed guidance concepts along with the International Conference on Harmonization's guidelines Q8 Pharmaceutical Development and Q9 Quality Risk Management (1, 2).

Quality-by-Design overview

Individuals working in pharmaceutical sterile development and manufacturing will undoubtedly be the most affected by regulations associated with QbD because of the unique associated technologies, processes, and products currently in use and development (see sidebar, "Quality-by-Design Overview"). Many of these technologies require new manufacturing processes that support existing traditional fill-finish operations. Many facilities, utilities, processes, and equipment may need to be modified (e.g., improving controls to reduce variability). This article provides an overview of FDA's draft guidance on process validation and QbD's impact on sterile manufacturing operations. Manufacturing process

Figure 1. (ALL FIGURES ARE COURTESY OF THE AUTHOR)

The following sections discuss how the draft guidance may influence the manufacturing process and product development. Processes addressed include manufacturing, aseptic manufacturing, lyophilization (freeze drying), and others that depend on multiple-unit operations (see Figure 1). Process design is typically the biggest challenge for a company's process development team and has tremendous impact on the success of the product. Sterile manufacturing has become increasingly more complex because of the increase in the number of poorly stable compounds, new technologies, unit operations, and controls. Numerous biotechnology companies, for example, use unique freeze–thaw systems to support dispensing and bulk-drug storage at temperatures often ≤ –80 °C that provide complete control of bulk-drug thawing, dispensing , freezing, and storage.
FDA's draft guidance suggests that the process development team design a process suitable for routine commercial manufacturing that can consistently deliver a product that meets its critical quality attributes (CQAs). The team's objectives are to: understand the sources of variation, detect presence and degree of variations, understand the impact of variation on the process and product attributes, and control variation in a manner that is commensurate and proportionate to the risks presented to the process and product. FDA further recommends an integrated team approach, with members representing multiple disciplines. The team should have solid project-management skills and archiving capabilities, be able to capture scientific knowledge and maintain project plans, and have full senior-management support. The latter may involve regular reports or presentations to senior management (3, 4).
In addition, the draft guidance calls for process decisions and justifications of control to be documented, internally reviewed, and preserved for later use in the product life cycle. Verification and mapping of the process design through to commercial documentation is required and planned changes should be documented and justified. Finally, after the performance qualification (PQ), a report documenting and cross-referencing results, data, issues, nonconformances, corrective actions, and overall conclusions regarding whether the process is in an adequate state of control must undergo management review and approval.

Cleaning Verification: Method Development and Validation Using Ion Mobility Spectrometry2

By: Elizabeth Galella, Scott Jennings, Madhavi Srikoti, Elizabeth Bonasso
IMS distinguishes ions of a given compound on the basis of their velocities through a drift tube under the influence of a weak electric field. Ion velocity (v) is proportional to the applied electric field (E)
in which K is the ion mobility in units of cm² /Vs. Drift time t is proportional to 1/K , ion mass m, and collisional cross section C. Reduced mobility K_o for an analyte is calculated by normalizing its drift time to that of the internal calibrant as in the following equation: in which (K_o^C ) is the reduced mobility of the calibrant and t C is the drift time of the calibrant.

Figure 3: Illustration of ions of varying sizes migrating toward the detector through a constant flow of air.

These velocities, or ion mobilities, are determined and selective for a given compound. The high sensitivity of the instrument (nanogram to picogram range) provides for an excellent technique to quickly verify equipment cleanliness. Figure 3 illustrates the separation process described in the theory above. This technique allows for positive or negative mode of detection. Each mode has a unique internal calibrant used for calculation of the K_o. In the positive mode the internal calibrant is nicotinamide. In the negative mode the internal calibrant is methyl salicylate. 
Advantages of IMS

Figure 4: Efficiency gained by ion mobility spectrometry (IMS) versus high-performance liquid chromatography (HPLC).

Ion mobility has unique advantages over the conventional HPLC technique for cleaning verification. Although the principles of IMS technology have been well established, its uses in the pharmaceutical industry have, until recently, been limited. This has been changed by the development of easy-to-use commercial instruments of moderate cost, with small footprint and high sensitivity (4). As shown in Figure 4, when compared with the typical HPLC method, the IMS technique can save a significant amount of time in the analyzing cleaning verification samples. Furthermore, a quick response time in getting results can reduce down time of key manufacturing and packaging equipment, ultimately leading to significant cost savings and increased productivity for the company (1,3). Method development
As with most analytical methods, the IMS instrument parameters must be examined and optimized for each compound as part of method development. These parameters include ionization mode, desorber temperature, injection volume, post-injection delay, drift flow velocity, and analysis time. The development process begins by examining the selectivity of the target compound in both positive and negative modes. In the authors' experience, most pharmaceutical compounds respond better in the positive mode because of the presence of basic functional groups within the molecule. The desorber temperature for compounds analyzed in the positive mode is typically set at ~290 °C. This temperature should be hot enough to effectively desorb the sample off the substrate but not so hot as to thermally degrade the compound. Typical sample volumes are 1 µL, injected using a 10-µL syringe. The post-injection delay is dependent on this volume and the type of solvent being used. A large injection volume of a solvent of low volatility requires a longer post-injection delay because it will take more time for the solvent to evaporate. Finally, the analysis time and drift flow velocity settings are dependent on the IMS response. A sufficient analysis time and drift flow are necessary to ensure depletion of all sample ions in the drift tube. In a case where the analysis time is too short, or drift flow velocity is too low, sample carryover may be an issue.

Figure 5: Second-order polynomial calibration curve.

The generally accepted practice is that an analytical method must exhibit sufficient sensitivity to measure the concentration at the ARL of the active agent or degradants being investigated in the swab and rinse samples. Typically, a limit test is used to establish a pass–fail criterion for swab samples and determine whether the manufacturing equipment is clean. Determining the pass–fail limit is accomplished by evaluating the instrument response curve and the system's precision. It allows analysts to capture the ARL within a linear calibration range, therefore providing an accurate means of determining the cleanliness of equipment parts. In the response curve, the "target level" represents the highest point within linear range (see Figure 5). The "action level" represents the resulting pass–fail level after adjusting the target level for instrument response variability. Any sample that responds above this action level registers as a failure. Any sample that responds below this action level registers as passing. Consequently, there is an area of uncertainty between the target and action level within which false-positive results may occur. However, these are generally infrequent occurrences. 
Method validation
Typical IMS method validation parameters to be considered include selectivity, linearity, reproducibility, recovery and solution stability. Selectivity of the analyte is determined based on evaluation of the molecular structure dictating the mode of detection. Selectivity from the sample matrix is based on minimizing the interference from product excipients and cleaning detergents, and should be examined before performing the recovery experiment. In addition, the linearity is based on a second-order polynomial curve obtained from the response versus the amount introduced, as described previously. Reproducibility must be used to determine the action level. Therefore, these parameters must be considered during method development and verified during validation.

Table I: Recovery of active from factory-finished, stainless-steel plates.

Recovery. After determination of the action level, sample recovery is determined from a 10-in.² stainless-steel coupon. A stock sample solution is prepared at 100% of the API concentration at the target level. The solution is then spiked onto three separate stainless steel coupons. The surfaces are allowed to dry before swabbing with a clean Texwipe alpha polyester swab. According to industry guidelines, the swabbing technique includes horizontal strokes to swab the entire designated area with one side of the swab head and then vertical strokes with the other side of the swab head. Each swab is then placed back into the vial containing sample diluent, extracted, and later analyzed for active content. Table I shows the recovery values from stainless-steel surfaces and corresponding percent relative standard deviation (%RSD) at the action level for a novel pharmaceutical compound under development. Table I shows the recovery results, which are typical of those generated by swabbing three different stainless-steel coupons. The observed variation is primarily a result of the inherent variability in the surface finish of the coupon. These values are independent of the analysis technique and may be optimized by adjusting the swabbing procedure and/or materials. However, application of a predetermined correction factor to swab assay results can be used to compensate for recovery values as low as 50% during method validation. Solution stability. Sample and standard solution stability studies are typically performed to cover 24 h at room temperature. Additional validation studies, such as robustness and intermediate precision, are not included in the authors' validation plan for a limit test. All of the parameters described previously must meet pre-established criteria as defined in the validation protocol. The criteria and validation protocol must conform to International Conference on Harmonization guidelines as well as internal standard operating procedures.
Conclusion
The ease of use and the small footprint of ion mobility spectrometry instrument allows for the system to be implemented in various work environments, such as quality control, and to report results with great sensitivity (nanogram to picogram range). Moreover, data reduction software package upgrade ensures 21 CFR Part 11 compliance. The use of this software, in addition to a limit test, has simplified the process of data manipulation, resulting in high-confidence passes for each clean sample analyzed.
Elizabeth Galella* is a research scientist, Scott Jennings is a senior research scientist, Madhavi Srikoti is an associate research scientist, Elizabeth Bonasso is a research scientist, all at the analytical research and development unit of the Pharmaceutical Research Institute, Bristol-Myers Squibb, One Squibb Drive, New Brunswick, NJ 08903, elizabeth.galella@bms.com
References
1. G. Walia et al., "Using Ion Mobility Spectrometry for Cleaning Verification in Pharmaceutical Manufacturing," Pharm. Technol. 27 (4), 72–78 (2002).
2. G. Walia et al., "Implementing Ion Mobility Spectrometry as a Cleaning Verification Method," Pharm. Technol.27 (3), 22–25 (2002).
3. D. Brand, X. Li, and T. Wortley, "Ion Trap Mobility Spectrometry: Reducing Downtime in Cleaning Validation and Verification," GE Sensing, http://www.gesensing.com/toolsupport/whitepaper.htm accessed June 16, 2009.
4. D. Brand et al., "Direct Swabbing and Surface Recovery with Ion Trap Mobility Spectrometry," GE Sensing, http://www.gesensing.com/products/resources/datasheets/GEsensing_whitepaperfinal.pdf accessed June 2, 2009.
5. R. DeBono, "Ion Mobility Spectrometry: A Fast, Sensitive, and Robust HPLC Alternative," Appl. in Chrom. March, 20–23 (2002), http://trace.smithsdetection.com/Documents/LifeSciences/LE203sBarringer.pdf.
6. G.A. Eiceman, "Advances in Ion Mobility Spectrometry," Crit. Rev. Anal. Chem.22 (1, 2), 471–490 (1990).

Cleaning Verification: Method Development and Validation Using Ion Mobility Spectrometry1

The cleanliness of manufacturing and packaging equipment in the pharmaceutical industry is critical to ensure product efficacy, personal safety, and the absence of unwanted active pharmaceutical ingredient (API) before the introduction of a different compound. Upon completion of processing a drug substance or tablet formulation, a detergent cleans each part of the pharmaceutical equipment. The cleaning verification process in the pharmaceutical industry involves several steps. First, the clinical supply or manufacturing unit of a company submits samples for analysis following the equipment cleaning process. The sample analysis is completed by an analytical department or quality control (QC) personnel. The results are reported back to the clinical supply unit, and the process is repeated until all samples have met the acceptable residual limit (ARL). The subject exposure limit (SEL) (in units of mg/subject/day) for a given compound is provided by a drug-safety evaluation group and is an industry-wide practice. The ARL of the API in each swab sample is a set at one-tenth of the SEL.
These types of samples have been analyzed by high-performance liquid chromatography (HPLC). In an effort to significantly reduce sample turnaround time, which can take as long as several days, ion mobility spectrometry (IMS) has been evaluated as an alternative method for analysis (1–4). The time taken for analysis is important because the faster that cleaning can be confirmed, the faster the plant can return to operation. This article discusses the theory of IMS, the benefit of IMS over HPLC analysis, and experimental considerations for method development and validation.
Theory

Figure 1: The IonScan-LS ion mobility spectometer with the Cobra autosampler.(FIGURES COURTESY OF THE AUTHORS)

IMS is a type of separation technique, similar to time-of-flight mass spectrometry, that distinguishes ions of a given compound based on their velocities through a drift tube under the influence of a weak electric field. The technique characterizes chemical substances based on their gas-phase ion mobilities and provides detection and quantitation of trace analytes (1). There are several IMS instrument vendors. Figure 1 shows the IonScan-LS ion mobility spectrometer with the Cobra autosampler (Smiths Detection, Warren, NJ), which was used in the studies described in this article.

Figure 2: Cross-sectional view of the ion mobility spectrometer sample inlet, ionization chamber, drift tube, and detector.

To perform the IMS analysis, a sample solution containing a compound of interest is injected by the autosampler onto a PTFE substrate and allowed to dry. Figure 2 shows the sample inlet, ionization chamber, drift tube, and detector (5). Sample is introduced by heating the substrate to ~290 °C, which results in desorption or vaporization of the sample into an inlet tube. Primary ion formation occurs through atmospheric pressure chemical ionization (APCI) using nickel-63 as the radioactive source. Following many collisions, product ions are formed and gated into the drift tube. These ions-based on size, shape, and charge-travel through the drift tube toward the detector at different velocities. In contrast to mass spectrometers, separation of ions is based on a size–charge relationship rather than the mass–charge ratio (6).