Introduction to Validation of Biopharmaceuticals

Synthetic drugs can be well characterized by established analytical methods. Biologics on the other hand are complex, high-molecular-weight products, and analytical methods have limited abilities to completely characterize them and their impurity profiles. Regulation of biologics includes not only final product characterization but also characterization and controls on raw materials and the manufacturing process. FDA has defined process validation as "establishing documented evidence which provides a high degree of assurance that a specific process will consistently produce a product meeting its predetermined specifications and quality attributes." This involves supporting product and manufacturing process claims with documented scientific studies. Protocols, results with statistical analysis, authorizations, and approvals must be available to regulatory inspectors. Process validation is part of current good manufacturing practices (cGMP) and is required in the US and EU for a manufacturing license.

In addition to process validation, biopharmaceutical firms must conduct analytical method validation, expression system characterization, facility and equipment validation, software validation, and cleaning validation. Final product quality is assured when these elements are combined with other elements of cGMP, including lot release testing, raw material testing, vendor quality certifications, and vendor audits.

Expression system characterization is performed before Phase I studies in humans to insure safety. Concerns include the presence of contaminating organisms, tumorigenic cells, proteins, nucleic acids, retroviruses, or other pathogens. Taking tissue culture as an example, characterization includes the source, raw materials used, selection methods, number of generations, transfection or fusion methods used, procedures for establishing working cell banks, facilities, identity, homogeneity, absence of contaminating pathogens, tumorigenicity, and stability.

Analytical methods measure product characteristics important for therapeutic safety and efficacy during preclinical and early Phase I studies. Additional tests are developed for final product release and in-process sampling of the final manufacturing process. These measure characteristics such as molecular identity, purity, potency, and safety. The number of tests should be sufficient to show manufacturing consistency and the impact of manufacturing changes. Once a test is made a formal part of the manufacturing process, it is almost impossible to remove. Test methods are evaluated for different attributes such as accuracy, precision, range, selectivity, recovery, calibration (detection and quantitation limits), assay sampling, robustness, and stability.

Test method validation is needed to conduct clinical trials. Specifications should start off wide for Phase 1 and narrow to tighter values in the license application. Relaxing established specifications is very difficult.

Process validation involves the identification, monitoring, and control of sources of variation that can contribute to changes in the product. It starts with process characterization studies using scale-down models for optimization, operating range specification, extractables and leachables characterization, and clearance studies. Such work depends on validated assays and representative scale-down models.

Process development normally involves identifying critical variables, defining setpoints for each unit operation, and establishing operating ranges (deviations from the setpoint). Maximum operating range (MOR) limits are typically set during Phase II or III. If they are exceeded, an investigation is necessary to determine if product quality remains acceptable.

Normal operating range (NOR) limits are determined by run-to-run reproducibility with scale-down models and trending with control charts at production scale. NOR limits lie within MOR limits, which must allow for normal variability while maintaining acceptable operation.

Facility and equipment validation is normally divided into design qualification (DQ), installation qualification (IQ), operational qualification (OQ), and performance qualification (PQ). Equipment validation begins with pilot production of clinical materials for Phase II.

DQ provides documented evidence that the proposed design of the facilities, equipment, and systems are suitable for the intended purpose. DQ must compare the design to a set of well-defined user requirements relating to product safety, identity, strength, purity, and quality.

IQ provides documented evidence that the system is assembled, installed, plumbed, and wired according to the user's design specifications, vendor recommendations, and appropriate codes and standards. Vendors typically provide much of the hardware documentation.

OQ provides documented evidence that the system performs as expected throughout its intended operating ranges, including all the system's different functions and all its components (hardware, monitoring instruments, controls, alarms, and recorders). Elements of OQ testing and documentation may be part of the factory acceptance test at the vendor's site. Integration with plant utilities and component installation must be verified at the factory. Hardware cleanliness must also be assessed after cleaning.

PQ is documented by processing actual feedstock by trained operators using buffers and utilities at the factory. Full-scale process validation includes testing the consistency of batch production.

Software validation operates under the principle that quality should not be diminished if a manual process is replaced with an automated process. Software must be developed and tested under a quality system with defined user requirements, change-control procedures, provisions for authorization of operators for data entry and data checking, data archiving, software backup, provisions for system crashing, and procedures for monitoring and correcting software problems. 21 CFR 11 defines requirements for maintaining the integrity of data and software and handling electronic signatures for traceability.

Cleaning validation demonstrates the ability of cleaning procedures to permit reuse of processing components and equipment without a concomitant deterioration of product quality. Batch-to-batch carryover is of particular concern in multi-use plants making more than one product.

Consistency of product quality is demonstrated by showing operating consistency and product quality from batch-to-batch, processing with only buffer (blank runs) with assays for contaminants, examination of cleaned surfaces and materials, and extended scale-down clearance studies on reused materials. Disposable processing components that eliminate the need for cleaning validation are increasingly used at small scale. Herb Lutz is strategic marketing manager at Millipore Corporation, 80 Ashby Road, Bedford, MA 01730, 781.533.2366, herb_lutz@millipore.com

General Strategies for Validation Extensions

ABSTRACT

Several gaps in current regulatory guidelines that govern the analytical method life cycle for the testing of biopharmaceuticals are identified. Strategic guidance on how to monitor and control the life cycle of an analytical test method is provided in this article. Analytical method transfer, analytical method component equivalency, and analytical method comparability protocols are discussed in light of risk-based strategies for validation extensions. The use of an analytical method maintenance program is suggested to control over time the predictable risk to patients and firm.

The successful completion of analytical method transfer (AMT) is a regulatory expectation for the extension of the validation status to other laboratories. The demonstration of equivalent test results and, therefore, an acceptable level of reproducibility when testing at a different location, can limit the potential risk to the patient (hence the regulatory expectation). Acceptable reproducibility also limits the risk of failing test results for the biopharmaceutical firm as established probabilities of passing specifications can be maintained. Similar, postvalidation changes in method components should be monitored and controlled to avoid significant (negative) changes for material or product release probabilities.

Analytical method validation (AMV) guidelines exist from several recognized sources.^1–6 Detailed validation guidelines for alternative microbiological test methods also exist.^7–8 In addition, a series of practical tips and discussions for AMV and related topics was recently published.^9–15 However, some topics are currently not sufficiently covered in recognized sources. For example, how can we demonstrate method comparability for new methods, extend the validation status onto other laboratories or other test method components, and maintain this validation status over time? What are acceptable levels for differences in method performance and when is a method no longer suitable?

This two-part series focuses on all postvalidation work that may be required to ensure process and product quality over time. This article discusses practical concepts on how to ensure successful validation extensions. Part II, to be published in the October issue, will include practical tools to ensure a validation continuum (maintenance) for validated methods. The second part will also include case studies for deriving meaningful and risk-based acceptance criteria for validation extensions and validation maintenance and will, furthermore, include a case study on how to reduce analytical variability in validated systems.

When replacing approved test methods with improved ones, analytical method comparability (AMC) data should be submitted together with the method description and validation results.¹³ Once a method is approved and in routine use, it should be maintained in an analytical method maintenance (AMM) program that can be administered through the validation master plan (VMP).¹⁴ If done well, this will ensure—like all postvalidation activities—consistent (accurate and precise) production process and product quality measurements.¹⁴ What exactly are the critical elements of good validations, validation extensions, or suitable validation maintenance? The answer lies mostly in the preset acceptance criteria for method performance and, of course, the actual validation results obtained. For example, if changes in analytical method components cause a change in test results and, therefore, in process or product quality measurements, we should capture when we will have exceeded method suitability limits. In other words, if the analytical method change will cause a predictable shift or spread of results with respect to specification(s), and therefore negatively impact the probability of releasing material, we should monitor this. To monitor and possibly compensate, we must first set reasonable suitability limits, then continuously control the overall method performance. Often, the most difficult part may be to estimate the associated risk of changed results with respect to both patient and firm, and from this, to set reasonable acceptance criteria. Once we truly understand why and when there will be a need for method improvement, we will likely know what should be done to compensate for the difference.

Each production process has an associated probability for the rate of rejections that can be readily calculated by relating specifications and production process performance. However, instead of having to deal with only two probabilities (pass or reject) that are "visible" and monitored by statistical process control (SPC), we should consider two additional possibilities for all reported results. Therefore, there is a total of four possible cases for releasing product or material, of which three should be avoided as often as practically possible. The four cases for reported test results are illustrated here.

Measured results are within established specifications.

• Case 1A: results are true.
• Case 1B: results are not true.

Measured results are outside established specifications (OOS).

• Case 2A: results are true.
• Case 2B: results are not true.

Cases 1A and 2A are routinely monitored by SPC. Cases 1B and 2B originate from other uncertainties such as imperfect test method performance or poor sampling and are not readily visible by SPC. Cases 2A and 2B are obviously not desirable because the firm cannot process nor sell this product or material. Case 1B constitutes a risk primarily to patients, but also means a risk to the firm if adverse product-related reactions or over- or under-dosing would actually occur. Case 2B constitutes a loss solely to the firm and should also be avoided mainly for profit reasons although other problems may also arise from this situation.

For our validation extension acceptance criteria, we should primarily set acceptable protocol limits from SPC with relation to specifications. We should consider the likelihood and impact for cases 1B and 2B, and avoid as much as possible measurement errors as part of the AMM program. Inaccurate or imprecise measurements will always cause a lower than ideal probability of observing results within specifications. The acceptance criteria for AMV and its continuum requirements must, therefore, ensure the low likelihood for all cases but 1A.

To meaningfully estimate risk to patients and the firm, we must understand our process data and integrate test measurement aspects into our risk-based validation strategies. Good risk management tools will dictate how much assay performance characteristics can deviate from the ideal. This will then set limits on how much we can tolerate over time for a test method to deviate from ideal (100% accurate and precise). It should also now become apparent why it is so important to maintain our validation status with an AMM program. When this is ignored, we negatively affect all four cases. (Negative here means increased risk to patient or firm). Although undetected, negative effects will occur for the "invisible" cases 1B and 2B because measurement errors are not captured by regular SPC. This may also cause the lack of process understanding and control, and may also lead to conflicts with current regulatory expectations (process analytical technology [PAT]) and may impact a firm's profits in the long run.¹⁵

ANALYTICAL METHOD TRANSFER

Validated analytical methods can be transferred from one laboratory to another without the need for revalidation at the receiving laboratory.^9,16 A typical AMT is accomplished by testing at the sending and receiving laboratories in a round-robin format. Testing is performed on three different product lots over three days, using two operators and two instruments in each laboratory.^9,16 Reproducibility of test results, within and between laboratories, is demonstrated in Table 1 by evaluating intermediate precision (different operators, instruments, days and product lots at each site) using an analysis of variance (ANOVA) and by comparing the differences in mean results for each lot between both sites.^9,16 For each AMT, preset acceptance criteria for intermediate precision and for the absolute differences between sites are derived and justified from the validation at the sending laboratory.⁹

The AMT reports should include descriptive statistics (means, standard deviations and coefficients of variance), comparative statistics (ANOVA ρ-values) for inter-laboratory results, and the differences-of-mean values for both (or each) laboratories. Each report documents evidence that the transferred test method is suitable (qualified) for testing at the receiving laboratory.

For cases where the ANOVA ρ-value is less than 0.05, secondary acceptance criteria should be established for the comparison-of-means and variability of the results to demonstrate the overall lab-to-lab reproducibility of test results. It is advisable to include a numerical fall-back limit (or percentage) because the likelihood of observing statistical differences may increase with the precision of the test method. In addition, some differences (bias) between instruments, operator performances and days are expected.⁹ We should tailor our acceptance criteria for overall (intermediate) precision and for the maximum tolerated difference between mean laboratory results (accuracy or matching) to minimize the likelihood of obtaining OOS results (2A and 2B) or 1B results.⁹ The setting and justification of all acceptance criteria must strike a balance and is a critical part of each protocol. A detailed AMT case study was presented elsewhere.⁹

ANALYTICAL METHOD COMPARABILITY

As we need to demonstrate equality or improvement whenever approved methods are replaced, which and how are method performance characteristics compared? Table 2 provides guidance on which validation characteristics to use for comparability protocols for each assay type per ICH Q2A/B. All qualitative tests should contain a comparison of hit-to-miss ratios (for "specificity") between the approved method and the new method. If a qualitative limit test is exchanged, the detection limit (DL) of the new method should be compared and should be equal or lower for the new method. For all quantitative methods, the method performance characteristics accuracy and precision (intermediate precision) should be compared.¹³It is of great regulatory concern whether results may change overall by drifting (change in "accuracy" or "matching") or by an increase in data spreading ("intermediate precision"). An increase in data spreading or lack of precision will mostly increase the likelihood of observing cases 1B or 2B and should be avoided. A drift in results or "lack of matching" may require a change in the specifications. This drift in release results can occur in two directions, lower or higher results. Both directions are not acceptable outcomes for the demonstration of accuracy, and testing for equivalence between methods is therefore correct.¹³ The goal of comparisons of other characteristics (e.g., DL) is different such that two outcomes (equal or better) are acceptable. For example, for the comparison of DLs, the two outcomes of having either an equal or lower DL would both be acceptable.¹³ A third comparison category is the demonstration of noninferiority and is usually the easiest to pass for comparability. However, we should keep in mind that the use of any of the comparability categories (noninferiority, equivalence, superiority) using ICH E9 and Committee for Proprietary Medicinal Products (CPMP) guidance documents should be properly chosen and justified.^13,17–19 In other words, noninferiority testing may be justified for the comparison of some primary characteristic such as DL if other secondary criteria (e.g., increased number of tests or test samples) can compensate for the small level of inferiority of the primary comparison characteristic.¹³

Quantitative limits (QLs) could also be compared. However, both QLs would have to be estimated by the same principle (e.g., estimated by regression analysis). A low QL is desirable as it will let us quantitatively report and monitor low-value results by SPC. There are several ways to compare QLs. For example, we could compare the regression coefficients of both linear assay response curves to estimate both QLs and would also get a general idea how accuracy and precision characteristics compare over the assay range. Table 2 constitutes a general guidance. Particular examples for noninferiority, equivalence, and superiority testing to demonstrate method comparability were provided and discussed elsewhere.¹³

No matter which comparability category we may use for a statistical comparison (with ρ = 0.05), a protocol should provide the design of experiments to be done and the pre-specified value for the allowable difference in results. The prespecified maximum allowable difference is illustrated in CPMP's Points to Consider On The Choice Of Non-Inferiority Margin.¹⁹ The allowable difference should be set similar to AMV or AMT. The difference should be set and justified by relating specifications to SPC data and considering the likelihood of observing any of the four cases (1A, 1B, 2A, and 2B).¹³

Stephan O. Krause, PhD, is the manager of QC Technical Services and Compendial Liaison at Bayer HealthCare , LLC, Berkeley, CA 94701, tel. 510.705.4191, stephan.krause.b@bayer.com

REFERENCES

1. Guideline for Industry Text on Validation of Analytical Procedures, ICH Q2A, 60, 1995. http://www.fda.gov/cder/guidance/ichq2a.pdf

2. Guidance for Industry Q2B Validation of Analytical Procedures: Methodology, ICH Q2B, 62, 1996. http://www.fda.gov/cder/guidance/1320fnl.pdf

3. The Fitness for Purpose of Analytical Method, Eurachem, Teddington, UK (1998). http://www.eurachem.ul.pt/guides/valid.pdf

4. Traceability in Chemical Measurement, Eurachem/CITAC, Teddington, UK (2003). http://www.eurachem.ul.pt/guides/EC_Trace_2003.pdf

5. Guidance for Industry, Bioanalytical Method Validation (2001). http://www.fda.gov/CDER/GUIDANCE/4252fnl.htm

6. Draft Guidance for Industry, Analytical Procedures and Methods Validation (2000). http://www.fda.gov/cder/guidance/2396dft.htm

7. Technical Report 33, Evaluation, Validation and Implementation of New Microbiological Testing Methods (PDA, Bethesda, MD, USA).

8. Alternative Methods For Control of Microbiological Quality, EP. Supplement 5.5 [07/2006:50106] (December 2005). http://www.pheur.org/

9. S.O. Krause, BioPharm Int. 17(3), 28–36 (2004).

10. S.O. Krause, BioPharm Int. 17(10), 52–61 (2004).

11. S.O. Krause, BioPharm Int. 17(11), 46–52 (2004).

12. S.O. Krause, BioPharm International Validation Guide, a supplement to BioPharm Int. 18(3) (2005).

13. S.O. Krause, BioPharm International Guide to Bioanalytical Advances, a supplement to BioPharm Int. 18(9) (2005).

14. S.O. Krause, BioPharm Int. 18(10), 52–59 (2005).

15. Guidance for Industry PAT — A Framework for Innovative Pharmaceutical Development, Manufacturing, and Quality Assurance (2004). http://www.fda.gov/cder/guidance/6419fnl.pdf

16. ISPE Good Practice Guide: Technology Transfer (International Society for Pharmaceutical Engineering, Tampa, FL, 2003).

17. Statistical Principles for Clinical Trials, ICH E9 (1998). http://www.emea.eu.int/pdfs/human/ich/036396en.pdf

18. Points to Consider on Switching Between Superiority and Non-Inferiority, CPMP (2000). http://www.emea.eu.int/pdfs/human/ewp/048299en.pdf

19. Points to Consider On The Choice Of Non-Inferiority Margin, CPMP (2004). home.att.ne.jp/red/akihiro/emea/215899en_ptc.pdf

Laboratory Equipment Validation and the Importance of a Manufacturer

Many types of equipment in both manufacturing and laboratory areas are critical to a properly functioning pharmaceutical process. The validation of laboratory equipment is not as clearly defined as the validation of equipment used directly in the production of pharmaceutical products, which requires thorough validation in almost all situations.

Should My Laboratory Equipment Be Validated? The evaluation should begin by determining the requirements of the end user, which are often defined in the User Requirements Specifications (URS). Additionally, it is critical to consider the laboratory applications as well as the associated equipment. Next, a risk analysis should be performed. Some types of equipment may seem less critical, but upon more thorough analysis, their real importance is revealed.

Responsibility for complying with the appropriate industry standards ultimately falls on individual companies, divisions, or departments. Failure to comply with current good manufacturing practices (cGMPs) or good laboratory practices (GLPs) can have serious consequences, including regulatory restrictions — such as the inability to sell the product.

Validation reduces the risks of non-compliance with regulatory agencies. It also can reduce compulsory in-process controls and testing. Validation is a means of improving procedures and final product quality. Rather than adding constraints imposed by regulatory bodies, validation is a process for improving efficiency and quality that ultimately can lead to cost savings.

Pharmaceutical companies are responsible for the qualification and validation of their equipment. As a result, they must be able to justify choices concerning these procedures to a regulatory agency auditor. The documented evidence supporting these choices is one of the fundamental requirements of validation. After all, validation is verifying and documenting with a high degree of assurance that specific equipment will perform consistently according to predetermined specifications. The documented evidence presented also must comply with cGMPs, incorporate preventive maintenance, and include a requalification schedule.

It is important that the pharmaceutical company works in conjunction with equipment suppliers to determine the appropriate validation protocols as well as the frequency of requalification. A manufacturer's validation capabilities can be an indicator of the quality of the equipment being supplied.

Water Purification Systems To further discuss validation principles, a single system with downstream effects on manufacturing and testing processes will be examined. The data in a laboratory is impacted by a variety of instruments, including water purification systems. If the water system does not consistently produce purified water, the validity of the data from these instruments can be compromised.

Manufacturers' Capabilities When acquiring equipment, particular attention must be paid to the equipment suppliers' ability to provide either direct or indirect help with equipment validation and qualification — even if the qualification will be performed by internal qualification services. When choosing a water purification system that will be validated, it is important to consider more than just the specifications of the water produced. Other equally important factors should be considered, such as the level of service provided and the manufacturers' validation experience. In order to meet user requirement specifications and regulatory guidelines, an equipment manufacturer that has implemented a comprehensive program must be chosen to ensure that their products can be qualified. Evaluation should include consideration of the manufacturer's design, manufacturing process, quality controls, traceability, documented evidence, training for users and service personnel, support for periodic maintenance, qualification, requalification, and other factors (see Table 1).

Water purification systems are essential pieces of equipment in most pharmaceutical laboratories for drug production, drug testing, and quality control applications. The quality of purified water used in these processes ultimately can affect the quality of the final product. This is why organizations such as the United States Pharmacopeia (USP) and the European Pharmacopoeia (EP) frequently state that water purification systems must be validated.

As with any other equipment, it is important to work with the water purification system manufacturer to determine the appropriate qualification protocols, how to carry them out, and an appropriate requalification schedule. The manufacturer's knowledge can be crucial, especially if they have developed specific documentation to assist with validation procedures. In addition to meeting cGMP requirements, this documentation also should be applied to each qualification stage and offer users comprehensive help in conducting system qualification.

The engineers who deploy system qualification protocols should be trained in validation procedures and familiar with production processes and regulatory requirements in the pharmaceutical industry. Furthermore, preventive maintenance helps ensure that the water purification system is kept in optimal condition and prevents down-time.

Validation Parameters Since the system qualification begins at the design stage, it is important to have a qualification team involved in the development of all new systems. This enables the manufacturer to incorporate the pharmaceutical requirements for system design and specifications.

An important parameter to be considered for the qualification of water purification systems is the calibration of measuring instrumentation. The product water should be monitored continuously for conductivity and, if required, total organic carbon (TOC) levels using calibrated instrumentation. Water purification systems should be designed specifically to meet USP 28 <643> and <645> suitability test requirements for TOC and conductivity respectively. Also, as recommended by FDA, system alerts should be implemented to warn users if the system is performing outside the pre-determined specifications. Additionally, systems manufactured in an ISO 9001/ISO 14001 certified plant permit good traceability. Certificates of Conformity, Certificates of Quality, and Certificates of Calibration also should be available.

The USP specifies that operational qualification protocols be performed on-site after the system has been installed to meet USP validation requirements.

Conclusion Equipment validation is essential. Determining what equipment needs validating starts with ascertaining the requirements of the end user. It then proceeds to a risk analysis with careful attention paid to regulatory requirements. Careful choice of an equipment manufacturer that offers a comprehensive validation services program, incorporating specially-trained personnel, on-site qualification protocols, calibrated measuring instrumentation, and the relevant documentation in accordance with GMP requirements can facilitate the validation process and overall regulatory compliance.

Sean Murphy is worldwide validation product manager for the Lab Water Division of Millipore Corporation, Boîte Postale 307, 78054 St. Quentin en Yvelines Cedex, France, (33)1.3012.7232, sean_murphy@millipore.com

Making Design Validation Effective

The purpose of design validation is to demonstrate that a product performs as intended. The usual route to this goal is showing that every item on the specification has been achieved, but it is not an easy path. The specification itself can create difficulty if it includes statements like "as long as possible" or the real horror "to be decided." Verification tests can reveal so many problems that the design must change to such an extent that earlier tests are no longer relevant. And there is also the practical difficulty of obtaining sufficient samples to test when the manufacturing engineers have not completed their standard operating procedures, the product design is not fixed yet, the component suppliers are late, and the marketing department has taken all the samples to show to prospective customers.

Design validation is not just a test tacked on to the end of development. It is most successful when it is an integral part of an effective design and development process. Thorough design validation combines effective testing with a well planned development strategy. As with other types of validation, design validation is associated with jargon and technical terms that have different meanings for different people. This introduction explores general principles that must be adapted to the needs of a company, product, or team.

Product Specification The product specification is the foundation of design validation. It is vital that it is clear and well-structured since the validation must show that everything it contains has been achieved. A hierarchical, top-down specification that begins with the needs of the users and ends with process tolerances is recommended.

Benefits to the user. The specification should contain a statement that the product delivers the right amount of drug in the right form to the right place. It also often includes statements about ease of use, environmental conditions, labeling, and cleaning. The critical issue is quantifying these statements; otherwise it is not possible to validate them. For example, "easy to use" is no help at all. Strict validation requires that customers (or at least representative people) attempt to use the product and their success and opinions are documented. Performance. Product performance specifications begin to convert the user needs into engineering values. For example, specifications for a self-injection device would include the depth of penetration of a needle, the toughness and hardness of the skin, and the delivery time for the drug.

Reliability. Reliability is a huge topic in its own right and a difficult one. A product that is used over a long period will have an expected lifetime, a failure rate during use, and a failure proportion for early-life defects. A one-shot device is characterized by a success probability after a given storage time. Environmental conditions for use, storage, and transport affect reliability. Some products can use the "Martini specification" — any time, any place, any where.

4. How it works. This part of the specification describes the product's specific characteristics and defines the engineering parameters that ensure the product meets its performance specification. During the design and development process, this part of the specification grows to include details of critical components, dimensional tolerances, and process conditions.

The Design Validation ProcessPrevention of problems. Failure modes and effects analysis (FMEA) is a standard tool for risk assessment. It should be used early in the development process at the system level to try to foresee problems such as those a user might experience.

FMEA should also be used during development to anticipate design errors that could have serious consequences but which are unlikely to be discovered before manufacture commences. Critical factors could be the choice of plastic for a component, corrosion resistance of a spring, or estimates of mechanical loads on a specific part.

Development trials. Exploratory development trials used to improve a designer's understanding of how the product works are an essential part of the development process but have no value for validation. However, development trials that follow a protocol and are written up in a report may save work later. When early drafts of a specification include phrases like "to be decided," feasibility trials may show what performance levels can be expected — for example, the lifetime of a hinge, the number of operations before cleaning is needed, and the fluid pressure at the tip of a needle.

Design reviews Formal design reviews are conducted by the design team with assistance from others who can bring a fresh view and challenge assumptions. One meeting may be enough for a simple product but reviews for mechanical, electrical, software, and system design can take up many days. The design review considers the FMEA, development trials, design calculations, and decisions that have been made, all with a particularly critical eye.

Verification tests. These are the principal element of design validation. Some of these tests are performed on complete product, but others may be done on components or sub-assemblies. This is especially relevant to long-term reliability where a pump or motor may be tested in isolation to demonstrate that its lifetime is sufficient. The tests should include the effects of variation on performance, including variation which comes from tolerances in manufacture and from the product's environment. The variation can be allowed to occur naturally by using many people as test subjects, or it may be simulated by deliberate control of key characteristics, such as the viscosity of a drug or the storage temperature.

If development tests have already established that the product's performance is satisfactory, it may be possible to write a simple "substantial equivalence report." This justifies using the results in lieu of a verification test. A substantial equivalence report can be used if the protocol for the verification test would be little different from the development tests and if the design has not changed significantly.

The test protocols and pass limits are approved before the tests commence. Any deviations from the protocol must be agreed upon, and a list of discrepancies or failures must be maintained. If the development work was thorough, there should be few discrepancies; the purpose of the tests is confirming that the performance is within specification.

Discrepancies can be resolved with design changes, but this must be accompanied by an analysis showing how other elements of the performance specification might be affected. In many cases, this analysis must be followed by repeating some verification tests. If the number of discrepancies and design changes increases, it may be necessary to redefine the verification tests as development trials and commence a new verification.

Some discrepancies can be resolved by simply amending the specification. In theory this should not happen if a top-down approach was taken in creating the specification. In reality, part of the performance specification often is written after feasibility studies, which were performed under ideal conditions on a laboratory bench. A test unit using production parts under "worst case" conditions can fail if the effects of the tolerances are not considered.

A third way to resolve discrepancies is identifying assignable causes of failure — the protocol was not followed, there was a power failure, a test lead broke. However, there is a risk that these causes become a series of excuses that are applied until a passing result is obtained.

Validation tests. Validation tests are performed when it is not possible to objectively measure performance. They are applied, for example, to the ease of assembly of a device, the legibility of labels, and the instruction manual. A team of about 10 people is selected with the requirement that they are representative of the intended users and are not familiar with the product. This excludes the design team and many engineers and managers in the quality, production, and marketing departments. The team follows the validation protocols and their subjective assessments are recorded and compared with the pass limits. The criteria for deviations and discrepancies that apply to verification tests also apply to validation.

Post-market surveillance. Information from real users also must be collected, but it is not part of the formal design validation for most products. (Clinical trials are a different matter entirely.) Questionnaires and interviews provide the best feedback about ease of use and operability and are used to confirm that the verification and validation tests were an effective surrogate for actual use.

With some products, post-market surveillance includes reclaiming and testing units from users. These tests reveal early information about potential reliability problems that could have been missed in laboratory trials. Post-market surveillance is not a required part of design validation, but it reduces commercial risks and engineering costs.

The Development Process Product development can be conceived of in stages: concept feasibility, prototype development, pre-production, and pilot production. The time and relative effort expended at each stage depends on the type of product, but the design proceeds in parallel with the development of the manufacturing processes. In particular, some components, such as plastic injection moldings, often force the alignment of product, process, and validation schedules. Table 1 shows how design and process validation fit together.

Development trials may be part of the design validation, especially for reliability and when defining certain aspects of the performance specification. This is the time to finish writing the validation master plan and to perform the FMEA.

Development samples are used to check performance and set up assembly processes. These differ from the previous prototypes in that molded components are available and allow more realistic trials to be performed.

A pre-production batch is assembled from "final" components by operators under the guidance of engineers. Verification tests at this stage include the effects of natural variation from component tolerances and differences between operators. The batch is also used to complete design validation tests. After testing, the units often are used as demonstration samples, but they should not be used by customers as they were not produced using a fully validated process.

Later pre-production and pilot production batches can be sold and used by customers. Design validation is complete by this stage, but process validation is still underway. Final release tests may be needed if the units go to customers.

Components and Parameters The various types of components and manufacturing processes must be treated differently at each stage of development.

Different numbers of units are needed at each stage for a typical, assembled product. A simpler product like a skin patch could have many more samples at each stage. During early development there will be many components and sub-assemblies but often only one complete unit.

It typically takes several months before injection-molded parts are available in volume from a validated process. Hand-crafted samples or computer-made prototypes can be used in the beginning, followed by initial samples from a tool.

Mechanical parts include the clips, springs, and fixtures that are either custom built or standard, off-the-shelf items. Many of them do not change during design and development, and the initial parts are "substantially equivalent" to the final design.

Most electronic designs have standard components on a printed circuit board. As with mechanical parts, the initial design is often similar to the final version.

Software embedded in a product may be simple to change, but verification tests are long and need to be repeated each time, since changes to complex logic paths can have unexpected consequences.

Engineers who assemble the first prototypes know what they are doing, but the variation that arises from operators following their instructions can contribute to poor performance and must be considered in the design validation.

In the early stages, the product is tested by engineers using laboratory equipment. Units used in design verification trials should be tested using production equipment, especially if the equipment is used to adjust or calibrate the product and can affect performance. The equipment itself does not need to be validated at this stage. Typically, process engineers will not validate the tests until the design is complete and they have sufficient units to test.

Final release tests are needed if there is insufficient data to show that the standard production tests can guarantee the performance of the product. This occurs when the standard tests measure a feature of the product, such as a running speed, pressure, or force, that predicts the amount of drug delivered, the delivery time, or other important factors. Development trials may have demonstrated a strong relationship, but variation in the product or the test may weaken the link. These tests show the form of the relationship and protect customers who receive early production units. As with production tests, this is not part of design validation, but it does show how design and process cannot always be cleanly separated.

George R Bandurek, Ph.D., is principal of GRB Solutions Ltd, 9 Cissbury Road, Worthing, West Sussex BN14 9LD, England, 44.1903.215175, george@grb.co.uk

The road to free validation

At first glance, the title of this article may bring a wry smile to the face of many an astute practitioner, but I can provide 'documentary evidence' that free validation is not a just a play on words, but a financial reality.

Flawed philosophies

As a seasoned lecturer in validation and compliance, I welcome novel ways of explaining what validation and, more generally, compliance are; how they affect a company; and how best to implement them. Fundamentally, as a pharmaceutical facility embarks on a validation initiative, or rather the overall pursuit of regulatory compliance, projects can easily become lost in the detail and, consequently, lose sight of their true objectives. All too often, personnel put their energies into 'doing things right' and, while this may seem commendable, on closer inspection it can be found wanting. I have found this embraced in companies as part of policy, but these flawed philosophies can manifest as problems almost anywhere in the business. Unless the company has the evidence to back up such claims, regulators will know exactly what to challenge and where to expose these shortcomings.

Doing things right is also often extolled as the rhetoric in training sessions and project meetings without consideration of the huge costs and burden of both the validation effort and the remedial tasks in the infrastructure required to support them. Often we find investment in both is disproportionate to any returns, making it no small wonder that validation is still regarded by many with great suspicion. Practitioners have also opined at conferences that it adds no tangible value to their business, but why is this misconception still prevalent? Why are there still so many misunderstandings surrounding validation and what constitutes full compliance with, for example, FDA and the Code of Federal Regulations (CFR)? One answer is that we should all ponder less about 'doing things right' and think more objectively about 'doing the right things', otherwise we may find that we have elevated the entire operating parameters of the business to a level it cannot afford, is ill equipped to develop and incapable of sustaining.

Conditions

There are conditions to achieve 'free validation'. First, financing a major validation project requires substantial capital outlay and is a daunting task for all concerned. When validation is placed alongside the daily running of the business, cultural resistance is inevitable and someone will invariably ask: "Why do we have to do this?" The point they should be making is that it is not part of their job description, contract of employment or day-to-day duties; in fact ,the extra work is more often a substantial departure from the daily continuity that keeps the business going.

As the intensity of a project builds, so too does the pressure on those in key positions, which contorts the point of compliance from one of substantive inconvenience to a general feeling of upheaval. Add to this the barbed comments between colleagues during monthly project budget reviews, where disparities between project outlay (finance) and progress become all too apparent, and validation becomes even more controversial. Management has every right to feel prickly as the costs and business risks are enormous — get it wrong and you compromise product quality, patients' health and the company.¹

As the funding dries up, corners are cut, strategies are reinterpreted, assumptions are made and the whole experience of striving for regulatory compliance begins to fall apart, if not overtly, covertly in private memos and closed door tête-à-têtes. In the end, the red ink is slashed all over what is left of the budgets, but what has really happened is that the business risk has risen and placed the company at the mercy of the thoroughness of regulatory bodies. But maybe the business will get lucky? Maybe they will not notice that policies and key procedures are not followed and that things have not always been documented. If there is a version of Russian roulette in the pharmaceutical business, this is it. Symptomatic of a business tumbling toward critical and major observations, the condition is known as 'quasi-validation.'²

Keeping it simple is key, but this is easier said than done. Keeping the costs of validation and compliance to a minimum would keep many happy as it would lessen the work load across the entire organization, freeing us to do what we do best — make the finest medicines and devices in the world.

But how does one go about 'doing the right things,' bringing down costs and providing validation for free? There are ways and means via a collection of informed perceptions on well-worn industry maxims, such as, there is little difference between 'process development' (PD) and 'process validation' (PV).³

With the right investment in PD, specifically the optimization of manufacture using a 'corrected business framework (CBF),' validation is achieved in unison and paid for out of the profits from increased yield and heightened efficiencies in manufacture and the infrastructure that supports it. Such a strategy places validation in a whole new light and makes pursuing it good business sense, but only when it is done well and fully integrated.

The epithets used earlier in the context of this article, such as 'remedial actions' and 'CBF', are the terms I prefer when citing the problems inherent within a company. 'Remedial actions' pertains to company infrastructure, namely the short-comings in engineering, maintenance, calibration, analytical methods, utilities, manufacturing, personnel, training, the quality management system, IT and batch records. If there are problems in any of these business units (departments), they will manifest as failings within validation; not failings of validation, per se, but failings of infrastructure — shortcomings that support the undisputed truth that you cannot validate bad practice.

Conversely, a 'CBF' is one that has commercial terms and conditions, and regulatory compliance at its core. Therefore, there must be a clear distinction and balance between business risk (loosing money) and regulatory risk (compliance). For example, within any validation project, only systems, equipment components and instrumentation that have a direct impact on product quality should have a place in the validation scope. Anything deemed to be business risk should be placed among regulatory risk as a function of informed judgments, never out of ignorance.

It is time to abandon the ill-conceived quasi approaches to validation and compliance, not least because the subjects have moved on and become more complex and expensive, but with the advent of electronic records and signatures, the demand for full process and product characterizations, and the growing use of statistics to demonstrate compliance, validation concepts continue to challenge the best of the best. However, the fundamentals of the subject are as true today as they were when Theodore E. Byers introduced PV to the pharmaceutical industry on 11 October 1974.⁴ As validation continues to mature, it also seems to have acquired a quantum state whereby the more we look the more we see. With this comes a heightened awareness of companies' imperfections, shortcomings that make everybody nervous as there is always someone responsible.

The mechanics of validation are very simple. Validation is the pursuit of exactitudes (yes/no, pass/fail, critical/noncritical, compliant/noncompliant). Unfortunately, these are then applied to inexact sciences meaning that a greater degree of realism and rationalization is no longer an option, but a serious business need, especially when one considers that business and compliance risk equate to degrees of business exposure that increase exponentially within the project. This is amplified when a company forms the aforementioned quasi approaches to validation and compliance from a platform of false economies.

How to achieve free validation

So, what are the means by which free validation can be achieved? The following ten categories, in no particular order, show the way and outline a more enlightened and lean approach to validation and compliance. These savings will, collectively, offset the capital outlay, if not immediately then in a realistic pay-back period.

Planning. It's all in the planning as they say. Plan the work and work the plan — validation and the uniform state of compliance are no exceptions to this rule. Reduce the project to the basics and marry these to the existing business model. While it may seem like trying to get a square peg in a round hole at times, there is sound reasoning behind the need to straddle such obstacles. There is no sense in trying to change too much too soon as continuity is key. Maintain all the basic tenants of quality assurance (QA) and quality control (QC) at all times and ensure that the business units are configured collectively, aligned with regulators' GMP requirements. Also remember that regulators have little interest in business efficiency; they are only concerned with whether you have control over both the good and bad elements of manufacture and the facility that supports it.

Gap analysis. Perform a gap analysis against each business unit to determine in real time how healthy the infrastructure is in relation to compliance with regulations and use the findings (the gaps) as the outline scope of a remedial plan. Apply to this process a proceduralized approach to impact assessment, such as methods penned by ISPE, to rationalize and differentiate between business and regulatory risks (modular differentiation).

The process will, effectively, reduce the validation scope. A simple method of achieving this is to obtain the asset registers for all systems, equipment, components and instrumentation and then analyse them in a committee type forum to designate their GMP impact (direct, indirect and no impact). For computer systems, we follow the risk-based approach. Remember, only those with direct impact should figure in the validation plan, but you should log all rationales and the reasons for their respective designations as these will later help explaining any distinction given. They also provide an important source of reference material that supports change control and batch record.⁵ Simply put, check you have all the pieces in each department and ensure that they are compliant with each respective part of the regulation.

Remedial plan. A remedial plan is a recent, but essential, concept. If a company does not address the compliance gap across departments then problems will later manifest in validation, along with all the problems evoked by having to open countless numbers of change controls and deviations. As suggested earlier, the infrastructure is the backbone of the organization, and must be sufficiently robust to support validation and compliance, otherwise there is no business.

In reality, the remedial plan is a collection of smaller plans that outline the patches and fixes required in each business unit. The plan will include a list of deliverables, such as those found in the matrix of a validation master plan (VMP), but in a remedial plan they are deliverables required to correct the infrastructure, and the necessary upgrades to plant and equipment. Once the business unit has been corrected and configured within itself, work can begin to configure it to each of the other departments, providing a robust and compliant infrastructure (modular integration).

Documentation. Simplify the validation suite of documents with lean approaches that rationalize procedures, guidelines and templates. Use these as the basis to form validation plans. The production of these is simplified further still by the prior development of a validation policy and strategy document. While this is not a mandatory document, it is one that includes the statements and details of the strategies pertaining to all aspects of validation and compliance, including cleaning and analytical methods; test methods validation; computer systems; utilities; equipment; and process facilities. By these means, VMPs can be written succinctly and concisely, rendering it much easier to understand and implement the 'policy and strategy' document. This then leads into any programming Gantt charts that are required. Some of the more tried and trusted methods of streamlining validation include:

• Family protocols — master protocols used to validate generic groupings of equipment.
• Integrate Factory Acceptance Test (FAT)/Site Acceptance Test and commissioning with validation as far as possible, placing more emphasis on QC in the engineering sequence.
• Design engineering with validation as part of the design criteria.
• Macro-driven validation templates (these also support QA/Part 11).
• Training — plan the work and work the plan!⁶

Resources. Commit resource and funding to optimize manufacture. As stated earlier, there is little difference between PD and PV. The commitment to PD calls in to play the very mechanics found in PV, resulting in greater efficiency, visibility and control in manufacture, leading to less scrap, more yield and increased profit margins. Essentially, a full commitment to PD should provide PV for free.³

One of the primary functions in PD is 'process characterization' of the process steps: the system of documenting the capabilities of process steps all the way to the edge of failure to establish the 'worse case scenario'. This provides a fuller understanding of the process and a juncture to document process capability. It also doubles as operational qualification and provides some of the obligatory documentary evidence. A secondary function of characterization for validation and compliance is in the use of statistics and statistical sampling. There has always been sampling, but the concept of statistical sampling is relatively new in validation and is now attracting greater interest in other areas within regulatory bodies. Statistics and statistical solutions (sampling plans) are the portal between PD and PV (Figure 1). By examining the process through statistics, using statistical analysis tools and programmes (e.g., Six Sigma and Minitab software), and using information garnered from process/product characterization and making adjustments to process equipment, instruments and components, and so forth, the process performance can be optimized. This will also provide the savings needed to soften the initial capital investment required to support both validation and compliance (Figure 1).

Reviews and approvals. Simplifying the review and approvals process may not, initially, take long to develop. The real-time constraints are often found in the facilitation of the document through the review and approvals process, and this problem is exacerbated where electronic approval is used. Reluctance to let go of the 'hard copy' means that old and new ways of document approvals live alongside each other. The difficulties are complicated by the routing of documents for 'unofficial' preapproval to smooth their eventual passage through the electronic system. This route seems to have invited far more reviewers and approvers than is required to achieve compliance. All the above lengthen the time it takes to complete the cycle from blank paper to approved document.

Rationalization of procedures and the document system. Each business unit will have a plethora of dedicated standard operating procedures that have evolved with little or no regard to how they are best configured to the business sector they are designed to service, and with no regard to how they link (directly and indirectly) with procedures in other departments/sectors. Ostensibly, the coverage of procedures carry overlaps, conflicts, misalignments, gaps and a degree of duplicated effort. The number of procedures should be reduced through rationalization, retirement, amalgamation and redesignation. However, there should never be a procedure when a guideline, work instruction or routine will suffice.

'Active' current good manufacturing practice (AcGMP). GMPs are required by law where cGMPs are the current interpretations of these laws and AcGMPs are the 'active' real-time interpretations of GMPs. cGMPs are penned by peer-review groups, such as the Pharmaceutical Inspection Convention, ICH and the Parental Drug Association, but these take time to filter through industry as they require drafts consultations, seminars, papers and, ultimately, publication. Therefore, GMPs and cGMPs are, by nature, retrospective when used by industry. Real-time interpretation of AcGMP is derived from a company's study of regulatory trends, citations and warning letters. These observations eventually find their way into the peer-review route and, ultimately, into amendments and additions to guidelines, before much later finding their way into actual GMP. But these current interpretations find their way into a company through policy, procedures and training.

There is also the pressure brought to bare on regulators by peer-review groups over elements of legislation, such as 21CFR Part 11 compliance, where industry was not convinced or prepared to foot the bill that, in the case of Part 11, was once estimated to be in excess of US$100 billion (€64.4 billion) globally. Remembering too that this is all about interpretation, the GMPs are written ambiguously so that this interpretation resides with the manufacturer, seemingly leaving no avenue for litigation with the regulators. Additionally, there is no chance of litigation regarding cGMPs published by the peer-review groups as they are only guidelines. There is no escaping that culpability resides fairly and squarely on the shoulders of the manufacturer. Therefore, to service a validation project well, a company must remain vigilant, and nurture a real-time awareness of industry and regulatory trends. Essentially, this creates a ratcheting effect spawned in regulatory audits, whereby companies A, B and C are inspected and have all found similar approaches to solving complex compliance issues. The regulators embrace these solutions and use them in later inspections within companies that have failed to conform to such field standards. Thus, a real-time interpretation is essential; one that is serviced through events, such as the trend in warning letters, to gauge the mindset of the regulators in 'real time' and in an 'active sense'.

Training, culture and management. Excellent procedures, slick strategies and the best will in the world are ineffective without lots of training, cultural buy-in and strong management.

Akin to the property maxim "location, location, location", the pharmaceutical industry's is "training, training, training", which must ensure that everyone sees the same big picture and understands the proscriptive elements of procedures in the same way. Having it written down does not guarantee it will be understood and followed in the same way by all, so unless one is prepared to train, test the training and monitor the outcome of the training thereafter, there is a risk that we are creating more trouble than we are trying to solve.

Cultural resistance is one of the biggest obstacles in the run-up to an inspection. In engineering, for example, validation is not part of the culture engineers have grown up with. On many occasions I have been asked by engineers: "Why try and fix something that is not broken?" It's a valid question. The answer I give is this: engineering has evolved primarily to satisfy commercial terms and conditions, but there are certain elements of engineering by way of their regulatory significance, distinction and application (discussed earlier as impact assessment) that single them out as part of a validation scope, not to satisfy commercial terms and conditions, but the regulatory exactitudes they are measured for success against. This includes testing, traceability (audit trails) and other documentary evidence.

Figure 2

Management is another area of great concern as many managers frequently lack the skill, experience or aptitude to do what is required. Usually, managers are the victim of the Peter principle:⁷ promoting someone to their level of incompetence. A good knowledge of validation, with a wide skill set, is essential for a validation and compliance manager if the job is to be managed on time, in budget and fit for purpose. There is no room for compromise either regarding this latter point as 'quality is King!' However, even those in validation frequently do not understand the big picture, and those outside do not understand any of the correlations, causations and commonality that validation engenders. All too often a project is doomed, and what is at fault? If one spent time conducting a simple trend analysis of warning letters, it would be seen that most problems emanate from management, procedures, training or a combination of all three. Ultimately though, the project is won and lost in the planning and the general assumption that the process already has capability, accuracy, precision and full characterization.

Figure 3

To keep the management of a validation and compliance project simple, it must be planned in four distinct phases:

• Phase A is where project status is established, gaps identified, plans formed and project tools (including training) generated and communicated to all concerned.
• Phase B takes the corrected modules and, first, configures them by department before linking each department to every other in a way that supports project objectives and compliance with the CFRs.
• Phase C validates the various processes, systems and practices against the CFRs.
• Phase D includes departmental auditing and project audits; FDA training for inspection; a dummy audit by an external company (to mimic an FDA audit) and, finally, FDA's proper inspection (Figures 2 and 3).

Commissioning material. A refined approach in the use of commissioning material in validation. The following statements should be considered when regarding both subject matters in one context:

• Commissioning is incomplete until validation has been successfully completed.
• The criteria for commissioning and validation are different. The former satisfies commercial arrangements, the latter regulatory compliance.
• The acceptance criteria for commissioning is often different to that for validation, and vice versa.
• The type and methodology used to document both events (commissioning and validation) can differ considerably or, occasionally, be the same.
• Test scripts for both events are usually a mixture of generic tests — those exclusively for validation and those exclusively for commissioning.
• The parameters set against the acceptance criteria for test results can differ greatly for both disciplines.
• Commissioning and validation can, theoretically, happen in any sequence. Moreover, the tests can seem the same, but success in validating pivots on subtle yet fundamental differences, such as those discussed earlier. While the two events have distinctly different agendas, they complement each other, as the above bullets emphasize.

Commissioning is undoubtedly a great precursor for validation. An inspection of the equipment is a necessary part of commissioning work as it exposes defects that are not detected at FAT or manifested through transit. Both will be corrected at the commissioning stage to prove conformity with the specification and conclude contractual arrangements. Ordinarily, this would be sufficient if it were not for subsequent validation. Even when commissioning is successful (modular differentiation), it does not guarantee that any associated qualifications will turn out likewise. The conclusion of a validation study (the configured performance of the equipment) may expose previously hidden flaws in:

• The design.
• Its application(s).
• Inadequacies inherent within commissioning.

One of the most important criteria is management. It is essential that the whole experience of commissioning, validation and overall compliance is managed properly, and by someone with all the requisite experience in all the disciplines mentioned. Without this, the programme will wander, costs will rise and confidence, as well as expectation, will rapidly fall away.

The right things

Call for papers

With the costs and complexity of validation and compliance rising, it is high time to focus on 'doing the right things'. With the right investment, savings can be achieved that offset the capital cost of a compliance and validation project, and provide significant savings within the revenue budget thereafter.

Validation is not there to police or find fault with the business, rather, it is a great business tool that provides both compliance and the assembly of a robust diagnostic tool. Good validation practice should save a lot of money, not cost a lot of money. Moreover, it should diminish regulatory risk. Done well, validation safeguards the company.

Keith Powell-Evans is Compliance and Validation Consultant at Altran (France) and Founder member of the Institute of Validation.

References

1. K. Powell-Evans, Pharm. Technol. Eur., 10(1) (1998).

2. K. Powell-Evans, Pharm. Technol. Eur., 14(9), 60–65 (2002).

3. GHTF (Global Harmonization Task Force) SG3/N99610:2004.

4. W. Gibson and K. Powell-Evans, Validation Fundamentals (Interpharm, Illinois, USA, 1998).

5. ISPE Commissioning and Qualification Baseline Guide (2000). http://www.ispe.org/

6. K. Powell-Evans, Pharm. Technol. Eur., 10(12), 48–52 (1998).

7. P.M. Senge, The Fifth Discipline, (Currency/Doubleday, New York, New York, USA, 1990).