Cleaning validation the holistic way

The pharmaceutical industry has traditionally adopted a piecemeal approach to cleaning validation. The procedures involved are physical cleaning, analytical validation, detergent and disinfectant testing, and routine monitoring – and these are usually viewed in isolation.

This approach is undoubtedly the result of multiple publications from regulators as well as departmental responsibilities, which have resulted in a lack of harmonisation and uniformity throughout the industry.

By understanding each individual aspect of the testing regime, it is possible to develop a holistic approach, which encompasses all the areas in which it is necessary to demonstrate regulatory compliance. A robust cleaning validation programme will give consideration to product residue from the manufacturing process, detergent residue post cleaning and the microbiological activity that needs to be negated to protect product integrity.

The key to assessing these parameters and to validate the cleaning procedure, is to develop and validate an analytical method correctly.

There are strict regulatory requirements for equipment and facilities that are classified as a pharma manufacturing environment. This has led to a relatively small number of materials used in the construction of pharmaceutical equipment, which is a clear advantage when considering an acceptable approach to cleaning and the validation of the cleaning process method.

The active pharmaceutical committee advises that: “The Cleaning Validation should demonstrate that the procedure consistently removes residues of the substance previously manufactured down to levels that are acceptable. It also advises that the cleaning procedure itself does not contribute unacceptable levels of residual materials to the equipment. The limits set should be practical, achievable and justifiable”.1

Individuals performing analytical cleaning validation are usually different from those who perform the cleaning procedures. These people are likely to be those in a QC or technical support function and not operational. It is, therefore, essential that an analyst is familiar with the clearing procedures and thoroughly understands the manufacturing process in order to devise a robust validation protocol.

For those charged with developing analytical methodology for use in validating cleaning, Table 1 details some considerations that should be made when reviewing cleaning procedures.

The objective of a cleaning validation protocol should be to validate the analytical method and challenge the cleaning procedure in order to validate the process.

Analytical method validation

Regardless of which of the three key methods (product residue, detergent residue or microbiological activity) is being validated, the same principles apply. All of the methods must be fit for purpose; facilitate recovery of the analyte; challenge the cleaning procedure, and be suitable for routine monitoring.

In the case of the fit for purpose method, the end point of the validation exercise is to ensure that each method of development demonstrates the following six features of linearity, repeatability, reproducibility, quantified limit of detection (LOD) and limit of quantification (LOQ), stability, robustness.

With linearity, a standard curve should include a LOQ and be of a suitable range that samples fall within it. Repeatability means the procedures in any method should be repeated to confirm the consistency of results. The acceptable level of variation will depend on the method. Reproducibility refers to the variation of factors such as the analyte which should be assessed to confirm the method produces comparable results when in routine use. LOD and LOQ will depend on several factors including the sensitivity of the analytical method and analyte. Typically, an LOQ of 0.5µg/ml will be sufficient to detect small quantities of residue on large surface areas. It is important to note that the LOQ in the method will determine the lowest level of residue that can be claimed for a surface.

In the area of stability, sample composition can change over time particularly when in solution. It is necessary to assess that samples remain stable and produce consistent results over an acceptable time frame during which all testing can be completed.

Robustness refers to the varying of parameters that may change during analysis and continued application of a method should be challenged. Examples of these would include HPLC column, temperature and sample volume. The acceptable level of variation will depend on the end point requirements of the method. In addition to these parameters, all of the methods should be as simple and quick as possible.

In a manufacturing setting, time is money and whilst a particular method used may be supersensitive if it takes 24 hours to run and requires Maldi-TOF mass spectrometers, it may not be well received by production managers.

Potent starting point

A good starting point for a product residue may well be a specific method such as potency. If an assay method is available for the product involved, the following modification should be considered to quicken the turnaround time from sampling to result: gradient to isocratic conditions, shortening of run time, and simple cost effective column.

It is likely that in most cases, it will only be necessary to identify the product and therefore the chromatography can be simple, as no complex separation of multiple analytes is required. The goal of these modifications is to produce a sensitive short method with the peak of interest eluting within five minutes. It is important that the analytical time is as short as possible as equipment and facility will remain idle until analysis is complete. Delays here can easily impact on production and the efficiency of the whole production process. This can be achieved by running an isocratic method due to rapid equilibration.

For detergent residue, a non-specific method such as TOC, may be used and the guidelines for validating the method are common to those detailed above.

Detergent manufacturers may be able to provide methods for their products and possible modifications to the manufacturer’s method, such as interference from product and interference from swabs may be required.

The accepted method for validating the cleaning of microbiological organisms from the process is disinfectant efficacy testing, for which the guidance comes in the form of British and European standards. The principle is to establish that post application of the disinfectant any biofilms of known micro-organisms are removed. Disinfectant testing follows a tiered approach as presented in Table 2.

US guidance

Similar to European CEN methods, the US Association of Analytical Chemists (AOAC) disinfectant methods have been generalised to apply across a range of industries. The general information chapter in the United States Pharmacopoeia (USP)-NF 29, ‘Disinfectants and Antiseptics’4 states that the current US process for the registration of a disinfectant does not address how disinfectants are used in the pharmaceutical industry. However, the chapter does offer guidance and background on disinfectant efficacy testing with information relevant to the pharmaceutical industry.

Within the EU, it is not uncommon that disinfectant manufacturers will have performed Phase 1 and Phase 2 step 1 (Table 2), usually following the BS EN 1276 guidance – ‘Chemical disinfectants and antiseptics. Quantitative suspension test for the evaluation of bactericidal activity of chemical disinfectants and antiseptics used in food, industrial, domestic, and institutional areas’.

It is, however, the responsibility of the end user to perform the surface testing on all surface types present within the pharmaceutical manufacturing environ-ment. The ‘BS EN 13697 guidance – ‘Chemical disinfectants and antiseptics. Quantitative non-porous surface test for the evaluation of bactericidal and/or fungicidal activity of chemical disinfectants used in food, industrial, domestic and institutional areas’ helps to achieve this.

Validation process

Validation of your process is the first stage of the BS EN method and therefore completion of the method and satisfying the acceptance criteria for a valid method is sufficient. These standards are not specific to the pharma industry and as such, it is necessary to modify the methods to be fit for purpose.

There is scope within the standards to test any surface that is present within your equipment or facility and to expand the number and species of the bacterial and fungal organisms used. However, modifications to the methods are often also necessary to obtain a fit for purpose method for a pharmamanufacturing environment.

Any modifications to the BS EN Methods should serve to mimic those conditions found at the facility. In addition to choice of surfaces and organisms, further modifications that should be considered are surface contact time, grade of water and dirty conditions. Further consideration to these modifications is presented in reference 2.

All product contact surfaces must be included in a cleaning method validation protocol, with the most common surfaces being stainless steel and inert plastics. In most cases, it is necessary to combine sampling techniques into the validation in order to successfully analyse residue on equipment and surfaces in routine monitoring. These techniques need to be assessed to establish that the process, as a whole, facilitates recovery of the analyte/organism within the required levels.

It is generally not practical to use operational equipment for the method validation. It is, therefore, a widely accepted practice to use coupons of known surface area, constructed of the same material as your equipment or facility.

Technique of choice

Regardless of the method, recovery is assessed in the same manner. The coupons are spiked with a known concentration of the analyte/organism. This usually involves the analyte dissolved in a solution, which is allowed to dry on the surface. The surface is then rubbed, swabbed or rinsed to recover the analyte/organism.

The techniques that will be used for obtaining samples from the equipment or facility during routine monitoring should be mimicked and challenged here.

The FDA’s preferred technique is the swabbing technique, where a small volume of solvent is applied to a swab and the surface swabbed. The less favoured rinse technique becomes useful for the awkward product contact components that have been identified during the review of the cleaning procedures. In such instances, a known volume of a suitable solvent is passed over the surface and the rinse is collected. The risk with the rinse method being that the biofilm or analyte are readily solubilised within the rinse otherwise there is the possibility of a lower count or recovery of organism/analyte. In the case of disinfectant testing the BS EN surface test method uses a rubbing technique to assess recovery.

Recovery is calculated as follows:

A recovery of 70 – 110% of nominal is usually acceptable to demonstrate a suitable method and validate the swabbing/rinsing method. A recovery within this range is then suitable for use in calculating the detergent residue and also in calculating product residues in routine monitoring. For disinfectant testing, recovery is acceptable at between 50 and 300 CFU per plate as a mean count of duplicate plates.

Challenge tests

Challenging the cleaning procedure is the final phase in the cleaning validation process and quite possibly the most important aspect of the validation, as it will establish any potential weakness in the process. Generally, it involves exposing spiked coupons to the cleaning procedure and then assessing the suitability of the cleaning process and materials in a real time holistic simulation. The coupons should be treated in the same way that operational surfaces are cleaned.

The effectiveness of the cleaning procedure will be validated through the assessment of either product residue remaining on the coupon, reduction in micro-organism presence either completely or to within the acceptable limits, and the presence of any residue from the cleaning detergent. For product residue, the maximum allowable carry over calculation is used:.

LTD = Lowest therapeutics dose (mg) or LD50 for cleaning agent (mg/kg)

D = Highest maximal daily dose (dose units)

Wb = Smallest batch size (g)

Wt = Highest unit dose weight (g)

Ss = Swab area (cm2 or in2 )

Se = Equipment product contact surface area (cm2 or in2 )

R = Recovery factor of active ingredient or cleaning agent

LD50 = Lethal dose of 50% of animal population3

For detergent residues, the FDA has repeatedly stated that it is the pharmaceutical manufacturer’s responsibility to establish acceptance limits and be prepared to provide the basis for those limits to the FDA. In all instances, it must be remembered that residues must not adversely alter drug product safety, efficacy, quality, or stability.

For disinfectant testing, a log3 reduction in micro-organisms must be achieved to comply with the BS EN method.

Routine monitoring

The expectations for continued testing beyond the cleaning validation vary for the three methods discussed here and ultimately, the type of use of the equipment and/or facility. However, good manufacturing practices and continued vigilance on the quality of production would dictate that a programme of routine monitoring to pre-prescribed criteria should be undertaken.

As an indicator for equipment and facilities that are used for the manufacture of multiple products, it is appropriate to swab the surfaces after cleaning and to use the validated method and recovery calculation to assess any product residue against the Maximum Allowable Carryover criteria.

Once the detergent residue has been validated and assessed, annual revalidation would be appropriate unless changes are made to the detergent formulation or the cleaning procedure is changed.

Annual revalidation of disinfectant efficacy would be time consuming and costly. It, therefore, it is proposed that only a change in formulation or a significant change to the cleaning procedure would warrant a revalidation. It must be noted however, that this does not negate the need to monitor micro-organisms on equipment or facility surfaces on an ongoing basis. Microbiological contact plates and swabs should form part of the routine environmental monitoring programme.

The final element of any routine monitoring programme where samples are obtained from equipment and facility surfaces, should be the impact of the sampling procedure on the cleanliness of the surface. A repeat of the final step in the cleaning process should be sufficient treatment after sampling.

The individual analytical methods used to validate a cleaning procedure share common parameters. Applying a holistic approach to these methods will help achieve clear and focussed cleaning validation.

By thoroughly understanding the manufacturing process, the cleaning procedures and the impact of routine monitoring, it is possible to produce a robust cleaning validation programme, demonstrate compliance and minimise disruption to the manufacturing activities.