Elizabeth Hewitt is senior scientist I, Elizabeth.Hewitt@mpi.com,at Millennium Pharmaceuticals, Inc., 40 Landsdowne St., Cambridge, MA 02144, USA.

Elizabeth Hewitt

Analytical quality by design (AQbD) has been a topic of interest as quality by design (QbD), risk-based pharmaceutical development, and manufacturing principles have been promoted over the past decade (1). It has been the topic of several publications and presentations (2–8), and goals have mirrored those outlined for general QbD-based regulatory submissions: the development of well-designed, understood, and controlled processes for manufacturing and testing pharmaceutical substances and products. An initially proposed AQbD framework outlined a goal toward delivering robust, well-understood analytical methods for effective process control in the delivery of high-quality, well-characterized, and controlled pharmaceuticals along with regulatory flexibility to suitably manage analytical methods over a product’s lifecycle (9). Introduction of that framework afforded a platform for discussion and development of practices toward achieving these goals. Several concepts associated with quality-risk management as outlined in International Council for Harmonization (ICH) guidelines (10–12) were adopted from the QbD lexicon. Design spaces, risk assessments, and criticality assessments are three such concepts. Analytical QbD also introduced concepts such as an analytical target profile (ATP) to define method expectations, and may be analogous to the quality target product profile that contains critical quality attributes (CQAs) as a QbD-based concept to define a method as “fit for purpose”. The following is an example of an ATP for a small-molecule drug product assay:

Assay: The procedure must be able to quantify [analyte] in [presence of X,Y,Z] over a range of A% to B% of the nominal concentration with an accuracy and uncertainty so that the reportable result falls within +/-C% of the true value with at least a 90% probability determined with 95% confidence (13).


	
	Based upon commonality with QbD-based principles, some of these concepts have even been discussed in US Pharmacopeial Convention (USP) stimuli articles as an opportunity to illustrate desired analytical method practices in support of the proposed 

 Chapter <1220> Lifecycle Management of Analytical Procedures (13-15).  These USP-based stimuli articles support the use of ATPs and quality-risk based assessments for managing methods through their lifecycles to ensure that methods remain fit for purpose.

	While these concepts are easy to discuss and perhaps describe when specifications have been defined, implementation of such concepts has posed challenges over the past decade for several reasons:

		Often the ATPs incorporate statistical language and may require enhanced statistical support when establishing ATPs.

		During development, specifications may change and consequently ATPs may change to ensure that methods remain suitable for intended purpose.

		It was proposed that as long as analytical methods favorably deliver against the defined ATP method expectations, methods should remain suitable and could be updated with enhanced regulatory flexibility. Industry feedback, however, has suggested that regulatory submissions that used AQbD concepts have been accepted but without, or perhaps with very limited, reduction in regulatory reporting for method changes (9,16).

	To assess the status of AQbD implementation approximately 10 years after introduction of QbD/AQbD concepts into pharmaceutical analysis (1, 2), the IQ Consortium’s Analytical Quality by Design Working Group (AQbD WG) submitted a survey to IQ member companies. The IQ Consortium’s mission is to advance science and technology by augmenting the capability of member companies to develop transformational solutions that benefit patients, regulators, and the broader R&D community. Eighteen responses from 16 member companies were received to the 34-question survey. The responses represent the use of AQbD in 12 large (>10,000 employees) pharmaceutical or biopharmaceutical companies and four smaller companies.

	More than two-thirds of the companies (69%, or 11 of the 16) had implemented AQbD in some way (

). Not surprisingly, the large pharma companies had a higher implementation ratio (83%, or 10 of 12 companies) than the smaller pharma companies (25%, or 1 of 4 companies). Stated differently, 91%, or 10 of the 11 companies, implementing AQbD concepts were from large companies (although the large companies had significantly more survey responses). Of the varied company responses, implementation of AQbD concepts occurred for both large and small molecules as many companies indicated application for both small and large molecules with very little difference in approach.

	For those companies that have implemented AQbD concepts, several business drivers were noted. Improved method performance was the most important driver. For those five companies that had not implemented AQbD efforts into their development programs, concerns regarding increased cost and/or resource investments with no or low benefit were the primary reasons.

	Technical details and challenges with implementation

	Of the 11 companies that have implemented AQbD concepts, the respondents were almost equally split between implementation just recently started and those who have been practicing AQbD concepts for an extended time. Of the five companies not having implemented AQbD, three indicated that they are just beginning. Interestingly, and not surprisingly, most companies practice AQbD concepts during late-stage development (>80% in Phase III) and commercialization, versus earlier development stages, to obtain maximum value from their investment efforts. 

 shows a breakdown of AQbD implementation during the drug development lifecycle for the 18 respondents. This outcome is clearly consistent with the greatest value voiced from AQbD implementation: achieving robust methods, better validation packages, and much improved method knowledge during development. While not captured in 

, comments toward utilization indicate the application of subsets of AQbD tools (e.g., modeling) by some companies in earlier development stages (Phases I and II) but with less systematic rigor than in later phases for better knowledge development.

	The survey also clearly indicated that the primary focus for implementation of AQbD concepts is on drug substance and drug product methods with much lower application to the testing of other materials (

). Interestingly, and perhaps not surprisingly, respondents have applied AQbD concepts almost equally between chromatographic and non-chromatographic methods and clearly do not apply such concepts to compendial methods.

	Eight respondents stated that there was time saved in developing robust methods, while six respondents thought otherwise. Lifecycle management of methods was thought to take longer with a multivariate AQbD-based approach, therefore requiring additional resources. However, the developed methods were thought to be more robust, and hence fewer issues encountered during routine use.

	The majority of companies in the survey leveraged commonality amongst methods to gain AQbD implementation efficiencies. Two examples included the use of generic risk assessments based on method types (e.g., single risk assessment templates for reversed phase-high-performance liquid chromatography [RP-HPLC] assay methods) and the use of standardized approaches to method development, such as the use of standard chromatographic column screens. In addition, automated software systems were used to offset increased resource demand to develop methods. Thirteen out of 15 respondents developed methods using various commercially available software packages such as Fusion AE, DryLab, ChromSword, and ACD/AutoChrom. Respondents have applied statistics (92%) and experimental design (100%) to improve the efficiency AQbD implementation. This is consistent with numerous examples of models and logically designed experimental screens found in the literature in an effort to promote development of robust methods under an AQbD moniker (17–20). A simple design of experiment (DoE) approach was the most widely used experimental design tool, especially for robustness testing. Modeling and simulation tools were routinely used by some companies (64%) for AQbD application. Of note, most respondents have not leveraged any other approaches, other than the tools mentioned, to offset any potential increase in resource demand for AQbD implementation.

	Regarding technical guidance (e.g., the issuance of departmental guidelines or standard operating procedures [SOPs] for implementation of AQbD concepts), six of the 16 companies noted the existence of a departmental guideline or SOP on AQbD processes. Those six companies who had implemented AQbD guidance represent about half of the companies that have implemented AQbD concepts. The comments on this question suggested that some groups felt specific guidance on QbD implementation was not necessary.  In fact, some responses indicated that QbD aspects of analytical work were directly documented alongside or within those work packages (e.g., method development or validation) rather than as a separate entity.

	As companies consider implementation of AQbD concepts, most responders (13 of the 18 responses, or 11 of the 16 companies) have acknowledged practice of at least some AQbD concepts in their organization. As briefly mentioned above, there were several business drivers for companies to consider for implementation of AQbD concepts in their method development efforts. Of the member companies surveyed, 67% responded that the most important business driver was the expectation of improved performance of analytical methods and robustness of these methods, and 43% indicated this business driver produced the largest return on their investment of AQbD practices. Member companies also indicated other reasons that offer a business incentive: improved knowledge of analytical methodology, regulatory relief with operational flexibility, development of consistent processes for method management, and facilitating lab-to-lab transfers (see 

	However, 31% of the company responses (5 of 16 companies) had not yet implemented AQbD concepts as illustrated in 

 (though three were just beginning).  One of the appreciable concerns mentioned as a potential barrier to advancement involves additional investment cost (e.g., resource costs) with perceived limited value. Respondents were asked whether there was an additional resource requirement in their area associated with analytical QbD. The answer was predominantly yes (79% of respondents). These additional investments are often framed in terms of enhanced statistical support, enhanced infrastructure to support risk assessments and QbD programs, and lack of clear guidance for efficient implementation of new processes.

	For some companies, the value of well-designed method development studies to define and ensure robust methods for intended purpose has been accomplished without the formal implementation of many AQbD-associated concepts (e.g., definition of an analytical target profile and performing formal risk assessments). For those implementing AQbD approaches, focusing application of QbD principles to methods of high importance in the control strategy and/or to those that are particularly complex and therefore of higher risk are appropriate to manage resource investments. It is not felt that applying QbD to every analytical method in a control strategy is a sensible use of resources. The additional level of method understanding and control provided by QbD should be applied following a risk-based approach so that resources are not wasted on well-defined, general compendial methodology. Additionally, cultural barriers also can inhibit adoption of newer practices.

	One of the initially touted potential benefits of AQbD submissions included regulatory flexibility surrounding analytical controls and robustness of the control strategy based upon enhanced knowledge gained by QbD efforts. However, this regulatory driver has not materialized as initially proposed during the first several years of QbD-based submissions.  

 affords a summary of hurdles toward AQbD implementation.

	One of the benefits of adopting a QbD approach is highlighted in ICH guidance: “Areas where the demonstration of greater understanding of pharmaceutical and manufacturing sciences can create a basis for flexible regulatory approaches.  The degree of regulatory flexibility is predicated on the level of relevant scientific knowledge provided” (1). Following on from the adoption of this guidance, interested stakeholders began to think about the concept of regulatory flexibility as applied to analytical methods that have been designed, qualified, and continually verified using QbD-derived approaches. Survey responses related to implementation, filing practices, and regulatory responses are discussed below. While most survey responders concluded that the regulatory aspects were not the main benefit from adopting a QbD approach to analytical methods, other benefits included greater method understanding leading to better method controls. These benefits went some way to justifying the increased effort required. Overall, the survey concluded that benefits could be gained by using QbD tools and processes during the analytical method lifecycle and further discussions on experimental and statistical best practice culminating in the publication of examples, case studies, and ultimately industry guidance are warranted.

	There were four questions relating to regulatory implementation as part of the survey. Initially, the survey asked whether the company had filed analytical methods developed with an AQbD approach. Seven companies, representing both large and small companies, had indicated affirmatively and provided feedback on the questions regarding regulatory agency review of AQbD implementation. The experience of pharmaceutical companies in this area so far seems mixed but more negative than positive. Varied regulatory understanding and expectations as well as a lack of clarity on what level of detail should be gathered and provided was noted. Responding to whether the AQbD regulatory review was successful, three companies had successful reviews and three had either pending submissions or submissions not filed yet.

	There was a variety in the level of detail of AQbD filings. In increasing detail, responses ranged from:

		Outline of risk assessment approach and description of analytical studies

		Analytical target profiles, risk assessments, and statistical analyses.

	Companies are using various approaches, likely based on historical successes. This is inefficient because it leads to more work for the applicant to decide on the approach and to address questions during review. It also leads to more work for reviewers who must adjust to different approaches for presentation. One favorable approach has involved companies including a “change appendix” or protocol in the filing describing the criteria to allow changes outside of the validated operating range. Such protocols are advantageous in gaining prospective approval and assist in planning for additional resources.

	AQbD information was submitted to several countries and positive feedback was received with the exception of using ATP for greater operational flexibility. Regulators preferred the term Method Operable Design Region (MODR) to Analytical Design Space to avoid confusion with process and product design space. Some of the regulators commented on the lack of robustness testing. A few of the respondents indicated successful filing of AQbD methods in the United States, the European Union, Canada, and Switzerland mainly for marketing applications. Authorities responded, asking to clarify the information presented. For cases where AQbD methods were developed for drugs in early/mid stages of development, the method details were not presented in the submission documents, and therefore, no feedback was received.

	The regulatory concerns are best summarized in 

.  Five of eight respondents (62%) said they had not seen method flexibility/regulatory relief as a great value from the AQbD information they provided. The increased flexibility, which was supposed to be gained from the analytical target profile approach to method registration, has not been realized and is likely to be a continued area of negotiation. The use of method operable design regions to gain operational flexibility for an individual method is also an area that requires clarity around regulatory expectations.

	With respect to including AQbD information in filings, respondents were evenly split between those who do and do not include AQbD information. It was commented that the approach was well received in the United States, Europe, and Japan, perhaps in line with the fact that these regions adopt new regulatory practices more quickly.  However, global method changes remain challenging as part of an efficient overall method lifecycle management strategy at the moment.

	In summary, results from a 34-question survey indicate that a majority of responding companies have adopted AQbD concepts over the past decade.  About half of the companies were just starting implementation. A clear driver for adoption of AQbD principles has involved the development of more robust analytical methods, and adoption of varied tools that enhance experimental design and modeling are evidence of commitment toward that goal. Furthermore, most value is found with implementation in the late-development stages and commercialization portions of an asset for best return on investment. The results of this survey were consistent with a separate informal AQbD adoption survey in 2015 of pharmaceutical colleagues (21). In that November 2015 meeting of representatives from approximately 25 biopharmaceutical companies that spanned small-molecule, large-molecule, and vaccine-related organizations, clear interest was shown for advanced discussions of AQbD principles.  More robust analytical methods and enhanced regulatory flexibility (average score of 4.7 out of 5, with 5 being the highest rating) were identified as drivers for interest in the development of AQbD case studies to advance discussions on the topic.

	There have been certainly technical, business, and regulatory hurdles toward implementation. While reduced regulatory reporting requirements were desired by some survey respondents for streamlined analytical method changes through commitment of ATPs in a QbD-based submission, that benefit generally has not been realized. Current guidance from regulatory authorities on mechanism and requirements for changing analytical methods and divergent regulatory requirements between regulatory authorities continue to challenge efficient analytical method lifecycle management. Lengthy and cumbersome processes exist to globally change analytical methods post-licensure, and foster lack of adoption of modern methods/technologies even as analytical technologies/instrumentation become old and obsolete. Despite this obstacle, implementation of AQbD principles offers a potential operational benefit that encourages further interest and application.

	1. FDA, Pharmaceutical CGMPs for the 21st Century-A Risk Based Approach, 2004.
	2. P. Borman, et al., 

., 31 (10) (October 2007).
	3. J. Ermer and P. Nethercote, 

, 36 (10) (October 2012).
	4. S. Colgan, et al., 

, 38 (9) (September 2014).
	5. T. Graul et al., “Quality by Design for Analytical Methods,” in 

 D. Am Ende, editor (2011), 545-562.
	6. M. Pohl et al., 

(Aug 27, 2013).
	8. S. Chatterjee, “QbD Considerations for Analytical Methods-FDA Perspective,” presentation at IFPAC Annual Meeting Baltimore, January, 25, 2013.
	9. M. Schweitzer et al., 

, 34(2), 52- 59,(Feb 2010).
	10. ICH, Quality Guideline Q8(R2) 

 (ICH, August 2009).
	11. ICH, Quality Guideline Q9 

(ICH, November 2005).
	12. ICH, Quality Guideline Q10 

 (ICH, June 2008).
	13. G. Martin et al., “USP Stimuli to the Revision Process on Lifecycle Management of Analytical Procedures: Method Development, Procedure Performance Qualification, and Procedure Performance Verification,” USP-PF, 39 (5) (2013).
	14. K. Barnett, et al., “Analytical Target Profile: Structure and Application Throughout the Analytical Lifecycle,” Stimuli to the Revision Process, 

42 (5), (2016).
	15. G. Martin, et al., Proposed New USP General Chapter <1220>: The Analytical Procedure Lifecycle, USP  website, 2016 (http://www.usp.org/usp-nf/notices/stimuli-revision-process-proposed-new-usp-general-chapter-analytical-procedure-lifecycle), to also be published in 

 43(1), (2017).
	16. EMA, “EMA-FDA pilot program for parallel assessment of Quality-by-Design applications: lessons learnt and Q&A resulting from the first parallel assessment,” Aug. 20, 2013, EMA/430501/2013.
	17. C. Hubert et al., 

, 1395, 88-98 (2015).
	18. G. Reid et al., 

36 (18), 2612-2638 (2013).
	19. Miller et al., 

, 52(35), 12269-12284 (2013).
	20. J. Kochling et al.,

, 125, 130-139, (2016).
	21. T. Schofield et al., “AQbD Industry Teleconference Meeting 06-Oct-2015” and associated “AQbD Case Study Industry Telecon Meeting Minutes 10-6-2015” with informal survey responses from >25 companies interested in AQbD and representing large and small-molecule product offerings as well as vaccines. 

 This article was developed with the support of the 

International Consortium for Innovation and Quality in Pharmaceutical Development

 (IQ). IQ is a not-for-profit organization of pharmaceutical and biotechnology companies with a mission of advancing science and technology to augment the capability of member companies to develop transformational solutions that benefit patients, regulators and the broader research and development community.


	Vol. 41, No. 4
	April 2017
	Pages: 52–59

	When referring to this article, please cite it as M. Argentine et al.,"Evaluating Progress in Analytical Quality by Design," 

Articles

The authors present the results of a survey of small- and large-molecule pharmaceutical and biopharmaceutical companies on implementation of Analytical quality by design concepts.

Evaluating Progress in Analytical Quality by Design

Forced-degradation studies, or stress testing, of a drug substance are used to demonstrate the stability-indicating power of analytical procedures (1−5). While regulatory guidance documents emphasize the importance of these studies, the guidance does not specify pH, temperature ranges, specific oxidizing agents, or conditions to use. According to International Conference on Harmonization (ICH) Q1A (R2), the nature of the stress testing will depend on the individual drug substance (1). As such, the design of forced-degradation studies varies from company to company with general experimental designs focused on the four main pharmaceutically relevant degradation mechanisms: thermolytic, hydrolytic, oxidative, and photolytic (6−8). The choice of forced-degradation conditions is based on data from accelerated pharmaceutical studies and sound scientific understanding of the product’s decomposition mechanism (9−10). The experimental designs published to date, however, have only included entirely aqueous systems. The use of organic cosolvents is considered for cases where the drug substances are extremely insoluble, and inert organic cosolvents are selected to avoid reaction with the drug substance under a given set of stress conditions (5). In the case of a Type IIA prodrug (11), whereby water hydrolyzes the drug substance to give the active moiety, forced-degradation experiments using aqueous conditions will only give the degradation products for the active moiety. As a result, additional analytical methods must be used to characterize other potential degradants that could potentially form before hydrolysis of the drug substance to the active moiety. Alternatively, a single normal-phase chromatographic method could be employed where it was shown to be stability-indicating for the drug substance in the case of Type IIA prodrugs. The challenge for this approach is in demonstrating that the method is stability-indicating because traditional forced-degradation experiments, which use aqueous conditions, are incompatible. This article explores the technical challenges associated with conducting forced-degradation experiments under anhydrous conditions.

Anhydrous forced-degradation case study for C1


In this case study, drug substance C1 was used because it is classified as a Type IIA prodrug. The drug substance C1 hydrolyzes under aqueous conditions to give the biologically active species C2. When C1 is dissolved in anhydrous, aprotic solvents, the molecule remains in its original form. When dissolved in aqueous systems, however, C1 converts into C2 as described in 

As the assay and impurity analysis of C1 is dependent on the solvent system, various analytical methods were developed to provide a complete analysis of the drug substance C1 and the active species C2. Forced-degradation studies were conducted on C1 using traditional aqueous conditions and analyzed by reversed-phase high-performance liquid chromatography (RP–HPLC). The degradation products found using this approach were the degradants of C2, the active species, but not the drug substance. Therefore, a second forced degradation study was conducted using anhydrous, reactive organic solutions and analyzed by normal-phase HPLC. The degradation products using this approach were degradants of both C1 and C2. By using anhydrous forced-degradation conditions, a normal-phase HPLC method was demonstrated to be stability-indicating for the drug substance. 

 C1 and C2 were synthesized by Millennium Pharmaceuticals (Cambridge, MA). Solvents and reagents, including anhydrous tetrahydrofuran (THF), non-anhydrous THF, hexane, pyridine, and trifluoroacetic acid (TFA) were all HPLC grade. The acetic acid, diisopropylamine and 

-azobisisobutyronitrile (AIBN) used were analytical reagent grade. The cumene hydroperoxide used was technical grade (80%). 

The equipment included an Agilent 1100 HPLC equipped with a diode-array detector, chilled autosampler, online degasser, quaternary pump, and high-performance liquid chromatography-mass spectrometry. Photo-UV stability samples were stressed in a Suntest CPS chamber using a xenon lamp. 

 The C1 drug substance and the active C2 species were separated by gradient using anhydrous (≤ 0.02% water) mobile phase on a cyano column. The sample was prepared by dissolving the C1 drug substance sample in an anhydrous (≤ 0.02% water) organic solvent mixture. The drug substance and active species were separated by the method and quantified by UV detection. The identity of C1 was confirmed by comparison of the C1 peak retention in the sample to that of the external C1 standard. 

 Degradation conditions evaluated included heat, acid, base, oxidation, and light. A stock solution of C1 was used to prepare each stressed solution. For each condition, a control without drug substance was included and treated the same way as the degraded samples. Photo controls included drug substance but were wrapped in aluminum foil to protect from light. The forced-degradation conditions used in this experiment (see 

Control solution: 1 mg/mL C1 in 40/60 (v/v) anhydrous THF/hexane

Heat solution: 1 mg/mL of C1 in 40/60 (v/v) anhydrous THF/hexane

Acid solution: 0.1 N acetic acid in 40/60 (v/v) anhydrous THF/hexane

Base solution: 0.0001 N diisopropylamine in 40/60 (v/v) anhydrous THF/hexane

Oxidation solution: 0.1% cumene hydroperoxide in 40/60 (v/v) anhydrous THF/hexane

Radical initiation solution: 10 mM AIBN in 40/60 (v/v) anhydrous THF/hexane

Photo solution: 1 mg/mL of C1 in 40/60 (v/v) anhydrous THF/hexane.     

Table I: Anhydrous forced-degradation results. THF is tetrahydrofuran, AIBN is 

1 mg/mL API in 40/60 (v/v) anhydrous   THF/hexane

1 mg/mL API and 0.1 N acetic acid in   40/60 (v/v) anhydrous THF/hexane

1 mg/mL API and 0.0001 N diisopropylamine   in 40/60 (v/v) anhydrous THF/hexane

1 mg/mL API and 10 mM AIBN in 40/60   (v/v) anhydrous THF/hexane

1 mg/mL API in 0.1% cumene   hydroperoxide in 40/60 (v/v) anhydrous THF/hexane

Analytical considerations for study execution


In the case of aqueous forced degradation studies, most companies follow a standardized approach with pre-set conditions such as 0.1 N HCl or NaOH and a target drug substance concentration (6). In the case of this non-aqueous forced-degradation study, stress conditions required careful consideration with regard to drug solubility, reactivity with the drug substance, safety, and compatibility with the separation method and detection technique. For the prodrug C1, organic reagents needed to have ≤ 0.02% water present to prevent hydrolysis and maintain the form of the molecule. Mixtures of organic and aqueous solvents were, therefore, not appropriate. 


The identification of reactive organic solvents/reagents with minimal water content included assessment of C1 solubility (see 

), compatibility, chemical reactivity with the drug substance, and safety handling (see 

). The criteria for good, fair, and poor was based on the feasibility of the experimentation. The drug substance solubility in the selected conditions was a crucial consideration because the drug substance was not soluble in many organic solvents. The drug substance was highly soluble in dimethyl sulfoxide (DMSO) and THF, which is why many of the systems considered contained these solvents. The normal-phase HPLC method diluent utilized a mixture of THF and hexane. As such, the HPLC diluent was a preferred solvent option for the anhydrous forced-degradation solution conditions. Another consideration was the miscibility of the solvent with the organic reactive reagent. In general, non-nucleophilic organic acids and bases were considered to avoid the potential hydrolysis of the drug substance. In addition, organic acids and bases that are commercially available, reasonably pure, and safe when heated were criteria used to select reagent candidates. 

Table II: Solubility of C1 in anhydrous, aprotic solvents.

In this article, the authors demonstrate that a normal-phase chromatographic method was stability-indicating for a water-sensitive prodrug. The stress conditions using aqueous and non-aqueous conditions were also compared to understand the information obtained with each approach.