Until the method has been stressed to the point where a problem occurs, you don’t know what the true boundaries are. Don’t just assume that by modifying a mobile phase by 2% or varying a pump speed by 0.1 mL that you have demonstrated that the method is sufficiently robust. Issues may not develop until a larger change has been made. The goal in method validation isn’t just to document that the method is suitable for use. It should be to truly confirm that it would work as expected, regardless of the analyst, the lab, and within reason, the environmental conditions. It may take longer to incorporate ‘real-world’ parameters into the process, but there will be more value in the day-to-day use after validation is complete and the method is transferred.
Smith (Agilent): The application of QbD principles to analytical method development and validation will have a significant positive impact. Fundamentally, analytical QbD requires that the analytical target profile (ATP) is identified before the analytical technology is considered. This means that fundamental requirements of the methodology are identified ‘up front.’ For HPLC methods, systems are available that integrate experimental design software with the chromatography data system (CDS) and analytical instrument, so that analytical method screening can be performed in an automated manner to identify a lead column, gradient, and mobile phase combination. This ‘Lead’ system is then subject to additional optimization experiments and final verification of the analytical design space. This approach has the potential to significantly speed up analytical method development and result in HPLC methods that are more robust, and therefore, analytical transfer problems are reduced.
Deviations and Variations
BioPharm: What deviations or variations may occur during analytical method validation in biopharmaceutical manufacturing?
Krause (MedImmune): We should distinguish a validation deviation from a validation failure. Both can occur, but the frequency of these events should be low so that the manufacturer can maintain a state of control. In general, an unplanned deviation is typically easier to resolve and may not hold up the completion of the validation study. For example, the use of an incorrect analyte spike or a confirmed sample mix-up may require an execution repetition but may not need to be treated like a (potential) validation failure once the deviation has been confirmed. Often, a lack of clarity in the validation protocol, poor preparation and planning, and/or insufficient analyst training can result in unplanned deviations.
A validation failure results from failing to pass the protocol acceptance criteria (or test method performance specifications). Validation failures are always serious and difficult to deal with under current interpretation of regulatory compliance. PDA TR 57 provides good ideas and suggestions on how to systematically deal with such events and to set up an appropriate quality system (similar to dealing with out-of-specification results).
Method Transfer
BioPharm: What are the challenges in method transfer?
Krause (MedImmune): Like method validation deviations and failures (see ‘Deviations and Variations’), similar root causes may also exist for method transfers (validation extensions). The readiness of the receiving laboratory should be evaluated. Consideration should be given to the availability of required analytical and supporting equipment, software, critical reagents, standards, controls, and analysts who are skilled in the relevant analytical techniques as well as the qualification status of all materials, equipment, and analysts.
If gaps are identified (e.g., the receiving laboratory has a similar analytical instrument), a risk assessment should be performed before execution of the formal transfer studies. Shipment and receiving procedures are needed to allow transfer of critical reagents, standards, and samples between laboratories. Incorporation of the test method procedure into the receiving laboratories quality system is also part of the transfer process.
The sending laboratory should provide hands-on training in the specific test method to analysts at the receiving laboratory, if needed. The type and amount of training needed will vary depending on the analytical method transferred and the existing experience of the receiving lab and its personnel. The evaluation of the capability of the receiving laboratory to execute the system suitability requirements of the method successfully during the training is recommended. It is important that all responsibilities between sending and receiving laboratories are established. PDA TR 57 provides additional practical tips on what to consider for analytical method transfers.
Guo (FDU): Method transfer is a very challenging exercise and can become more challenging if the receiving laboratories are in different countries/continents. Planning is definitely the key to a successful method transfer. The timelines for method transfer need to be discussed and clearly understood by both the originating and receiving labs. The methods transfer protocols should be carefully reviewed and approved by both labs. Logistics should be well coordinated especially when shipping the reference standards and samples overseas. Proper documentation including import licenses, if necessary, should be obtained in advance. To ensure the success of method transfer, the analytical methods should be evaluated by the receiving laboratory before the initiation of method transfer. The samples for method transfer should also be carefully selected. The new FDA draft guidance recommends that forced degradation samples or samples containing pertinent product-related impurities should be analyzed at both labs for a stability indicating method. For biopharmaceuticals, it might be difficult to ship the forced degradation samples to the receiving lab. A suitable protocol may be needed to guide the receiving labs to generate similar forced degradation samples themselves.
Krumenaker (West-Ward): When transfers are being done between sites, or with contract facilities, issues may arise with different makes of instruments. While an HPLC has the same basic components, regardless of manufacturer, there may be subtle differences in performance. For example, the construction of the optics in the detector may be just different enough to present unexpected issues with linearity or sensitivity. In some cases, older models from the same manufacturer may have differences in construction that will challenge a method in ways that will prevent a successful transfer. Some exploratory testing may be valuable, prior to transfer, to determine the compatibility of the instruments in the receiving lab and the method.
Smith (Agilent): Method transfer can go smoothly or can result in significant problems. The robustness of the analytical methodology being transferred and the experience of the ‘receiving’ laboratory have a significant impact on the success of the transfer. Differences in instrumentation, culture, and ways of working also contribute to possible challenges, and therefore, need to be considered. The analytical technology transfer (ATT) usually follows an analytical protocol, where results obtained between the ‘receiving’ laboratory are compared to those obtained by the ‘donor’ laboratory transferring the technology. Subjective tests such as color and appearance can cause disproportionate problems unless the specification is carefully worded. Tests with low level impurities require careful evaluation using % absolute differences, rather than student’s t-tests in the ATT protocol. In part, cultural and ‘ways of working’ differences can be overcome through training and short-term secondment, so that analysts in the ‘receiving’ laboratory acquire as much knowledge of the methodology as possible.
For transfer of HPLC methods, generally, fewer problems are experienced where both laboratories have the same analytical equipment. However, this is not always possible and ‘hidden’ differences in instrumentation (such as gradient formation, delay volume, or signal to noise) can contribute towards problems with transfer. Testing or qualifying the equipment in the same way can help identify differences in performance between analytical equipment.
References
1. FDA, Guidance for Industry, Analytical Procedures and Methods Validation for Drugs and Biologics, Draft Guidance (CDER, Rockville, Md., February 2014).
2. PDA, Technical Report 57 (PDA, 2012).
3. ICH, Q2(R1): Validation of Analytical Procedures: Text and Methodology (ICH, November 2005).
About the Author
Susan Haigney is the Managing Editor for BioPharm International.