Commentary M ini Focus I ssue: Tiered
approach to bioanalysis
For reprint orders, please contact [email protected]
Tiered approach: sense and sensibility “We need to have the freedom to use our judgment to apply scientific and logical arguments for the use of the tiered approach within a scientifically driven method validation strategy.” Keywords: exploratory IND n metabolites in safety testing n method characterization n tiered approach
Sense and Sensibility [1], a classic English novel by Jane Austen, is really about the dichotomy between ‘sense’ – reason, restraint, doing the right thing, acting correctly – and ‘sensibility’ – the ability to respond with appropriate sensitivity. So what does this have to do with bioanalysis? In developing and validating bioanalytical methods, the official process is documented in various guidelines, which clearly describe the regulatory expectations. This represents the status quo, the approach that can bring no reproach, as the guidelines are well known to all of us. However, there is also another possible approach, until recently not so clearly defined, which may be riskier, though perhaps more appropriate, simply because it is undersold in terms of guidance and documentation. For many applications, it may be more appropriate. Official bioanalytical method validation for molecules in full development and for which full regulatory standard assays are required are described in detail in multiple guidance documents including those of the US FDA [2,3], the European Medicines Agency [4], Japan [5] and Brazil [6]. These documents are required reading and should be clearly understood by all working in the field of bioanalysis. It was the proliferation of regulatory guidance documents in recent years that led to the formation of the Global Bioanalysis Consortium (GBC), a global industry group united behind the goal of distilling out the most important scientific aspects of the way we work and documenting these under the auspices of multiple harmonization teams. In 2010, the concept of the tiered approach to method validation was first described in a landmark European Bioanalysis Form (EBF) article [7], which focused on metabolite quantification, following the introduction of the metabolites in safety testing (MIST) guidance [8] and ICH M3 (R2) [9]. It is suggested that a scientific approach
to bioanalytical method validation is to adopt a tiered approach, where the degree of rigor within the validation process should be dependent on the stage of the project in the development process as well as the nature of the study being supported. Subsequently one of the GBC harmonization teams focused on Tiered Approaches to Method Validation [101] and their work is very well summarized in the referenced presentation. A number of points in this presentation ask some searching questions regarding the way we work: n Do all methods need to be validated to the ‘gold ’ standard required to support bioequivalence studies?
It is suggested that the ‘tiered approach’ should consist of 3 or 4 tiers. In this article, for simplicity 3 tiers will be described. In reality, the degree of assay characterisation will depend on specific project requirements. This is best represented diagrammatically (Figure 1). The details are described in the previously referenced documents [7,101]. In summary, the basic idea is that as the project moves from Discovery into the various Development stages, the degree of assay testing increases from very simple screening through to qualified and finally fully validated assays. This seems a very logical approach, one which could save considerable time and resources for both Pharma and CROs. Perhaps the widespread adoption of this practice is being held back by concern about potential negative reaction despite there being a very strong scientific rationale for it’s introduction. Further literature discussion and examples of the
10.4155/BIO.14.16 © 2014 Future Science Ltd
Bioanalysis (2014) 6(5), 611–616
Richard W Abbott Biosciences Department, Shire, Hampshire International Business Park, Basingstoke, Hampshire, RG24 8EP, UK [email protected]
Why do we over validate in early drug development when the end product is likely to be underutilized due to the high probability of project failure?
n
Do we over validate out of concern for possible regulatory consequences?
n
ISSN 1757-6180
611
Commentary |
Abbott
Discovery
Phase 0
Non-GLP
Screening or qualified methods
Phase 1
Phase 2
Phase 3
Phase 4
Non-GLP, GLP and clinical Qualified methods • Nonclinical PK, non-GLP TK, mechanistic PK/PD • Most nonstandard matrices (e.g., tissues) • Biomarkers • Early metabolite quantification • Early development clinical Validated methods • Nonclinical GLP toxicology studies • Clinical studies • Metabolites in plasma (late phase development)
Figure 1. Tiered approach to method validation dependent on project stage and compliance status. Adapted from [7] © Future Science Group (2010).
successful use of the tiered approach will help to convince the community that a sound scientific rationale can be justified in practice. The definition of the various ‘tiers’ is as follows [101]: n Screening method – limited characterization based on relative instrument analyte response and provides a relative analyte measurement. Appropriate for use in early discovery studies where a reference standard is not available; Qualified method – limited characterization with calibration standards and QC samples prepared using an authentic reference standard and provides absolute analyte concentration. Appropriate for use in late discovery studies, nonregulated development studies and studies where full validation is either not possible or inappropriate;
n
Validated method – full characterization as defined in regulatory guidelines and provides absolute analyte concentration. Required in all regulatory studies, except where not possible due to specific circumstances.
n
Further details regarding the key elements of the various method ‘tiers’ are reproduced in Table 1 for clarity [7]. As I understand it, Table 1 is not intended to be a list of rigid element requirements, it is a suggested guide to be used and adapted as appropriate according to scientific judgment. The elements listed in Table 1 refer to LC–MS/MS-based assay support for PK/toxicological evaluation. The elements associated with ligand binding assay 612
Bioanalysis (2014) 6(5)
support would be similar but not completely the same. Figure 2 is a pictorial representation or road map that relates the proposed tiers to the stage of drug discovery/development and the intended use of the bioanalytical data generated [101]. In following such an approach, it should be possible to ensure that we use our resources wisely. Use of the tiered approach should enable us to support more studies and projects with the same resource as full validation will only be used when scientifically appropriate, as opposed to for most studies. Clearly, full validation should be used where appropriate in regulated development work but it should not be adopted as a blanket approach for all situations. Hence, in Figure 2, the assumption that a validated assay must be available in Phase I for parent drug is challenged. Certainly, a qualified assay should be available at this stage, but until the multiple ascending dose study is completed we have an incomplete picture of the potential effect of metabolites at steady state on assay performance. Any negative effect on the assay will be clearly apparent with a qualified assay in place. Robust internal discussion should be conducted prior to determining an assay characterization strategy to ensure agreement on the scientific rationale. The key question should always be, ‘What is the question we are trying to answer?’ How will the answer to the question be used in practice? Will it be used to enable internal decision making or to enable regulatory milestones? The article by Timmerman [7] uses the quantification of metabolites as an example for the future science group
Tiered approach: sense & sensibility
| Commentary
Table 1. Key elements of screening, qualified and validated methods. Element
Screening
Qualified
Validated
Reference standard Result Method validation Calibration curve Identical matrix standard Independent QCs Acceptance criteria Inter/intra assay variability Selectivity Extraction recovery IS Carryover Matrix effect Short term matrix stability F/T matrix stability Long term matrix stability Additional stability Bioanalytical reports QC data check
No Relative No Optional SE SE SE No SE No No No No SE No No SE No No
Yes/preferred Absolute No Yes Preferred Yes FFP No SE No Optional SE SE Yes Yes (limited) SE SE Abbreviated Yes (limited)
Yes Absolute Yes Yes As per guidance [2] Yes As per guidance [2] Yes As per guidance [2] As per guidance [2] Yes As per guidance [2] As per guidance [2] As per guidance [2] As per guidance [2] As per guidance [2] As per guidance [2] As per guidance [2] Yes
FFP: Fit-for-purpose; SE: Scientific evaluation. Adapted from [7] © Future Science Group (2010).
use of the tiered approach, to assess the (relative) abundance or absolute concentrations of circulating metabolites. Choice of the appropriate tier is dependent on the stage of development and the level of contribution to pharmacological activity or toxicity. There are however other situations where the tiered approach is extremely logical, for example, biomarker assays [10], tissue analysis [11] and accelerator MS [12] and I will give one example from my own experience where it should be used. A few years ago, my company wanted to progress one out of three similar candidate prodrugs into the clinic very rapidly. In order to facilitate early progression into the clinic, the investigational new drug (IND) enabling studies were minimized by the use of an Exploratory IND [13] approach followed by a microdosing study in human volunteers. The Exploratory IND approach allows a minimal toxicology package (extended [14 day] single-dose study in a single species). As you will be aware, a micro-dosing study is defined as one in which the exposure to the volunteers is either 100 µg or 1% of the pharmacological dose, whichever is less. PK modeling by our colleagues in clinical pharmacology projected a Cmax of approximately 60 pg/ml. Therefore, in order to pursue this strategy, we had to demonstrate that it was possible to develop a cold assay with an LLOQ of 5 pg/ml (based on approximately 4 × t1/2). This we did, the exciting aspect for us being the opportunity to future science group
play a key role in shaping the clinical development strategy, something that does not often happen within bioanalysis, and which was a first for our group. We then had to decide how to validate the assay for each of the three development candidate prodrugs. Given that a micro-dosing study for a specific molecule is only ever likely to be used Discovery Exploratory IND
Screening of qualified assay Qualified assay (animal and human)
Phase 0
Qualified assay (non-GLP/biomarkers) Validated assay (GLP Tox) for parent drug
Phase 1
Qualified assay
Phase 2 Validated assay for parent drug Phase 3
Phase 4
Post-MIST: Validated assay for metabolites requiring quantification based on ICH M3 (R2) guideline
Figure 2. Roadmap showing correlation of tiered assay with stage of drug discovery/development [101] . IND: Investigational new drug; MIST: Metabolites in safety testing.
www.future-science.com
613
Commentary |
Abbott once, it should have been a logical decision to use a qualified assay for this work. However, there was nothing in the official guidance documents to provide assistance in developing the most appropriate strategy for the extent of assay validation and also neither the EBF nor GBC had discussed the concept of tiered approach at the time. Given that we were also dealing with instability issues associated with prodrugs we did not feel comfortable in taking any approach other than full validation. This position was also adopted by our clinical PK colleagues, a position that re-inforced the decision to perform a full validation. However, it must be stated that the concept of a qualified assay was very new to them and that they felt uneasy about taking what was regarded as an abbreviated, lower quality approach. As it turned out, this was far from the case as demonstrated in Tables 2 & 3. Summary data from one of these assay validations is shown below in Table 2 and Table 3 shows data from the first precision and accuracy batch from the same validation work. Clearly, a comparison of data in Tables 2 & 3 demonstrates that a single precision and accuracy batch, following the qualified method approach advocated in Table 1, would have been sufficient to enable the internal decision making following the micro-dosing studies. If a similar situation arose now, I would strongly advocate for the use of the tiered approach and, specifically, the qualified assay, to support a micro-dosing study. Hopefully this example has demonstrated a situation where regulatory concern took precedent over scientific logic. As more is published on the usefulness of the tiered approach, we shold all feel more confident about applying it in practice and defending it during regulatory review.
Looking outside the conventional bioanalytical arena, new diagnostic measurements [14] are being applied in the form of point-of-care devices for personalized medicine [15]. These diagnostic tools often incorporate sophisticated analytical chemistry though the interpretation of the results can pose significant challenges and requires close communication between clinical laboratory scientists and physicians [16]. It would be useful to have a debate about this. How are the diagnostic test results being used, what is the importance of the absolute values being generated, what do we know about their reliability and reproducibility and what is the impact on the patient? At the very least perhaps, some consideration should be given to the use of the tiered approach in validating the data generated in diagnostic investigations. Are the data fully quantitative or semi-quantitative? If a threshold value is important in the subsequent clinical decision making, how well has the diagnostic test been characterized? Finally, a few concluding remarks. We understand the importance of full bioanalytical validation to support regulatory studies where appropriate. However, we can see from this brief commentary article that there are situations in drug development where full validation may not be required, is not necessary, and may divert resources from where they are truly needed. We need to have the freedom to use our judgment to apply scientific and logical arguments for the use of the tiered approach within a scientifically driven method validation strategy. Of course, we should bear in mind the phase of drug development and the nature of the studies being performed as well as any associated risks. Bioanalysis is a quantitative discipline in which we all take great pride.
Table 2. Headline human plasma assay validation study data for active drug X and prodrug (Y). Analyte and statistical parameter
Intraday P&A data (n=3)
Interday P&A data (n=3)
LLOQ
Other QCs
LLOQ
Other QCs
Active drug X (%CV) Active drug X (% bias) Prodrug Y (%CV) Prodrug Y (% bias)
9.5 to 14.5 -8.6 to 8.2 6.0 to 9.2 -0.6 to 12.0
1.3 to 10.5 -12.5 to -2.7 1.4 to 14.3 -11.6 to 5.2
12.8 1.0 9.2 3.8
2.7 to 8.2 -10.5 to -3.5 5.0 to 11.5 -10.0 to -1.2
Stability Bench top Freeze–thaw Long-term frozen Extract reproducibility
At least 4 h acidified plasma stability (ice/water) At least 3 × F/T cycles (-70°C) At least 31 days frozen acidified plasma (-70°C) At least 72 h extract reproducibility (4°C)
Comparison of the full validation data with the data from the first precision and accuracy batch from the same work is shown in Table 3. P&A: Precision and accuracy.
614
Bioanalysis (2014) 6(5)
future science group
Tiered approach: sense & sensibility
| Commentary
Table 3. Single precision and accuracy batch for active drug X and prodrug Y (‘qualification’ batch). Analyte and statistical parameter Active drug X (% CV) Active drug X (% bias) Prodrug Y (% CV) Prodrug Y (% bias)
Intra-day P&A (n = 1) LLOQ
Other QCs
9.7 8.2 9.2 12.0
3.3 to 10.5 -12.5 to -3.5 2.0 to 6.7 -10.0 to –5.2
P&A: Precision and accuracy.
However, we do need to challenge the expectation that every assay we develop will be fully validated, whether necessary or not. Sense and sensibility. Future perspective Assay validation is an integral part of regulatory drug development. For GLP studies and late-phase clinical studies, it is imperative that bioanalytical methods are completely characterized. However, in discovery studies, nonregulated work and other specific cases, as highlighted, it is often neither possible nor necessary to undertake full assay validation. This article has attempted to demonstrate that a tiered approach to method characterization is both reasonable and practical. It does not seek to diminish quality, but provides a strong scientific basis on which to justify the appropriateness of the extent of assay
characterization. In the past, full assay validation has perhaps been attempted when not always necessary because of potential negative consequences. This should not be the major rationale for full assay validation if there is a strong scientific argument for an alternative, such as a qualified or a screening assay. Hopefully as there is greater awareness of the alternatives, along with further regulatory acceptance, the tiered approach will become more common in the future. Financial & competing interests disclosure RW Abbott is an employee of Shire. The author has no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed. No writing assistance was utilized in the production of this manuscript.
References Papers of special note have been highlighted as: n of interest nn of considerable interest 1
A Lady. Sense and Sensibility, Thomas Egerton (1811).
2
US Department of Health and Human Services, US FDA, Center for Drug Evaluation and Research, Center for Veterinary Medicine. Guidance for Industry Bioanalytical Method Validation. Rockville, MD, USA (2001).
3
4
5
US Department of Health and Human services, US FDA, Center for Drug Evaluation and Research, Center for Veterinary Medicine. Guidance for Industry Bioanalytical Method Validation, Draft Guidance, Rockville, MD, USA (2013). Committee for Medicinal Products for Human Use. EMA. Guideline on Bioanalytical Method Validation. London, UK (2011). Ministry of Health, Labour and Welfare. Guideline on Bioanalytical Method Validation in Pharmaceutical Development, Japan (2013).
future science group
6
Agencia Nacional de Vigilancia Sanitaria. Bioanalytical Guidance. RDC27 (2012).
7
Timmerman P, Kall MA, Gordon B, Laakso S, Freisleben A, Hucker RS. Best Practices in a tiered approach to metabolite quantification: views and recommendations of the European Bioanalysis Forum. Bioanalysis 2(7), 1185–1194 (2010).
nn
Contains extremely relevant information for use of the tiered approach.
8
US Department of Health and Human Services, US FDA, Center for Drug Evaluation and Research. Guidance for Industry Safety Testing of Drug Metabolites. Rockville, MD, USA (2008).
9
CPMP/ICH/286/95 – ICH Topic M3 (R2). Non-clinical Safety Studies for the Conduct of Human Clinical Trials and Marketing Authorisation for Pharmaceuticals (2009).
10 Timmerman P, Herling C, Stoellner D et al.
European Bioanalysis Forum recommendation on establishment and bioanalysis of biomarkers in support of drug development. Bioanalysis 4(15), 1883–1894 (2012).
www.future-science.com
n
Provides example of bioanalytical situations where the use of the tiered approach is very logical.
11 Xue Y-J, Gao H, Ji QC et al. Bioanalysis of
drug in tissue: current status and challenges. Bioanalysis 4(21), 2637–2653 (2012). n
Provides example of bioanalytical situations where the use of the tiered approach is very logical.
12 Higton D, Young G, Timmerman P, Abbott
R, Knutsson M, Svensson LD. European Bioanalysis Forum recommendation: scientific validation of quantification by accelerator mass spectrometry. Bioanalysis 4(22), 2669–2679 (2012). n
Provides example of bioanalytical situations where the use of the tiered approach is very logical.
13 US Department of Health and Human
Services, US FDA, Center for Drug Evaluation and Research. Guidance for Industry, Investigators and Reviewers: Exploratory IND Studies, Rockville MD, USA (2006).
615
Commentary |
Abbott
14 Philip R, Carrington L, Chan M. US FDA
perspective on challenges in co-developing in-vitro companion diagnostics and targeted cancer therapeutics. Bioanalysis 3(4), 383–389 (2011). 15 Gomez FA. The future of microfluidic
point-of-care diagnostic devices, Bioanalysis 5(1), 1–3 (2013).
616
16 Reisfield GM, Goldberger BA, Bertholf RL,
‘False-positive’ and ‘false-negative’ test results in clinical urine drug testing, Bioanalysis, 1(5), 937–952 (2009).
www.globalbioanalysisconsortium.org/A2/ final deck for public discussion and input nn
Contains extremely relevant information for use of the tiered approach.
Website 101 Global Bioanalysis Consortium on
harmonization of bioanalytical guidance.
Bioanalysis (2014) 6(5)
future science group
approach to bioanalysis
For reprint orders, please contact [email protected]
Tiered approach: sense and sensibility “We need to have the freedom to use our judgment to apply scientific and logical arguments for the use of the tiered approach within a scientifically driven method validation strategy.” Keywords: exploratory IND n metabolites in safety testing n method characterization n tiered approach
Sense and Sensibility [1], a classic English novel by Jane Austen, is really about the dichotomy between ‘sense’ – reason, restraint, doing the right thing, acting correctly – and ‘sensibility’ – the ability to respond with appropriate sensitivity. So what does this have to do with bioanalysis? In developing and validating bioanalytical methods, the official process is documented in various guidelines, which clearly describe the regulatory expectations. This represents the status quo, the approach that can bring no reproach, as the guidelines are well known to all of us. However, there is also another possible approach, until recently not so clearly defined, which may be riskier, though perhaps more appropriate, simply because it is undersold in terms of guidance and documentation. For many applications, it may be more appropriate. Official bioanalytical method validation for molecules in full development and for which full regulatory standard assays are required are described in detail in multiple guidance documents including those of the US FDA [2,3], the European Medicines Agency [4], Japan [5] and Brazil [6]. These documents are required reading and should be clearly understood by all working in the field of bioanalysis. It was the proliferation of regulatory guidance documents in recent years that led to the formation of the Global Bioanalysis Consortium (GBC), a global industry group united behind the goal of distilling out the most important scientific aspects of the way we work and documenting these under the auspices of multiple harmonization teams. In 2010, the concept of the tiered approach to method validation was first described in a landmark European Bioanalysis Form (EBF) article [7], which focused on metabolite quantification, following the introduction of the metabolites in safety testing (MIST) guidance [8] and ICH M3 (R2) [9]. It is suggested that a scientific approach
to bioanalytical method validation is to adopt a tiered approach, where the degree of rigor within the validation process should be dependent on the stage of the project in the development process as well as the nature of the study being supported. Subsequently one of the GBC harmonization teams focused on Tiered Approaches to Method Validation [101] and their work is very well summarized in the referenced presentation. A number of points in this presentation ask some searching questions regarding the way we work: n Do all methods need to be validated to the ‘gold ’ standard required to support bioequivalence studies?
It is suggested that the ‘tiered approach’ should consist of 3 or 4 tiers. In this article, for simplicity 3 tiers will be described. In reality, the degree of assay characterisation will depend on specific project requirements. This is best represented diagrammatically (Figure 1). The details are described in the previously referenced documents [7,101]. In summary, the basic idea is that as the project moves from Discovery into the various Development stages, the degree of assay testing increases from very simple screening through to qualified and finally fully validated assays. This seems a very logical approach, one which could save considerable time and resources for both Pharma and CROs. Perhaps the widespread adoption of this practice is being held back by concern about potential negative reaction despite there being a very strong scientific rationale for it’s introduction. Further literature discussion and examples of the
10.4155/BIO.14.16 © 2014 Future Science Ltd
Bioanalysis (2014) 6(5), 611–616
Richard W Abbott Biosciences Department, Shire, Hampshire International Business Park, Basingstoke, Hampshire, RG24 8EP, UK [email protected]
Why do we over validate in early drug development when the end product is likely to be underutilized due to the high probability of project failure?
n
Do we over validate out of concern for possible regulatory consequences?
n
ISSN 1757-6180
611
Commentary |
Abbott
Discovery
Phase 0
Non-GLP
Screening or qualified methods
Phase 1
Phase 2
Phase 3
Phase 4
Non-GLP, GLP and clinical Qualified methods • Nonclinical PK, non-GLP TK, mechanistic PK/PD • Most nonstandard matrices (e.g., tissues) • Biomarkers • Early metabolite quantification • Early development clinical Validated methods • Nonclinical GLP toxicology studies • Clinical studies • Metabolites in plasma (late phase development)
Figure 1. Tiered approach to method validation dependent on project stage and compliance status. Adapted from [7] © Future Science Group (2010).
successful use of the tiered approach will help to convince the community that a sound scientific rationale can be justified in practice. The definition of the various ‘tiers’ is as follows [101]: n Screening method – limited characterization based on relative instrument analyte response and provides a relative analyte measurement. Appropriate for use in early discovery studies where a reference standard is not available; Qualified method – limited characterization with calibration standards and QC samples prepared using an authentic reference standard and provides absolute analyte concentration. Appropriate for use in late discovery studies, nonregulated development studies and studies where full validation is either not possible or inappropriate;
n
Validated method – full characterization as defined in regulatory guidelines and provides absolute analyte concentration. Required in all regulatory studies, except where not possible due to specific circumstances.
n
Further details regarding the key elements of the various method ‘tiers’ are reproduced in Table 1 for clarity [7]. As I understand it, Table 1 is not intended to be a list of rigid element requirements, it is a suggested guide to be used and adapted as appropriate according to scientific judgment. The elements listed in Table 1 refer to LC–MS/MS-based assay support for PK/toxicological evaluation. The elements associated with ligand binding assay 612
Bioanalysis (2014) 6(5)
support would be similar but not completely the same. Figure 2 is a pictorial representation or road map that relates the proposed tiers to the stage of drug discovery/development and the intended use of the bioanalytical data generated [101]. In following such an approach, it should be possible to ensure that we use our resources wisely. Use of the tiered approach should enable us to support more studies and projects with the same resource as full validation will only be used when scientifically appropriate, as opposed to for most studies. Clearly, full validation should be used where appropriate in regulated development work but it should not be adopted as a blanket approach for all situations. Hence, in Figure 2, the assumption that a validated assay must be available in Phase I for parent drug is challenged. Certainly, a qualified assay should be available at this stage, but until the multiple ascending dose study is completed we have an incomplete picture of the potential effect of metabolites at steady state on assay performance. Any negative effect on the assay will be clearly apparent with a qualified assay in place. Robust internal discussion should be conducted prior to determining an assay characterization strategy to ensure agreement on the scientific rationale. The key question should always be, ‘What is the question we are trying to answer?’ How will the answer to the question be used in practice? Will it be used to enable internal decision making or to enable regulatory milestones? The article by Timmerman [7] uses the quantification of metabolites as an example for the future science group
Tiered approach: sense & sensibility
| Commentary
Table 1. Key elements of screening, qualified and validated methods. Element
Screening
Qualified
Validated
Reference standard Result Method validation Calibration curve Identical matrix standard Independent QCs Acceptance criteria Inter/intra assay variability Selectivity Extraction recovery IS Carryover Matrix effect Short term matrix stability F/T matrix stability Long term matrix stability Additional stability Bioanalytical reports QC data check
No Relative No Optional SE SE SE No SE No No No No SE No No SE No No
Yes/preferred Absolute No Yes Preferred Yes FFP No SE No Optional SE SE Yes Yes (limited) SE SE Abbreviated Yes (limited)
Yes Absolute Yes Yes As per guidance [2] Yes As per guidance [2] Yes As per guidance [2] As per guidance [2] Yes As per guidance [2] As per guidance [2] As per guidance [2] As per guidance [2] As per guidance [2] As per guidance [2] As per guidance [2] Yes
FFP: Fit-for-purpose; SE: Scientific evaluation. Adapted from [7] © Future Science Group (2010).
use of the tiered approach, to assess the (relative) abundance or absolute concentrations of circulating metabolites. Choice of the appropriate tier is dependent on the stage of development and the level of contribution to pharmacological activity or toxicity. There are however other situations where the tiered approach is extremely logical, for example, biomarker assays [10], tissue analysis [11] and accelerator MS [12] and I will give one example from my own experience where it should be used. A few years ago, my company wanted to progress one out of three similar candidate prodrugs into the clinic very rapidly. In order to facilitate early progression into the clinic, the investigational new drug (IND) enabling studies were minimized by the use of an Exploratory IND [13] approach followed by a microdosing study in human volunteers. The Exploratory IND approach allows a minimal toxicology package (extended [14 day] single-dose study in a single species). As you will be aware, a micro-dosing study is defined as one in which the exposure to the volunteers is either 100 µg or 1% of the pharmacological dose, whichever is less. PK modeling by our colleagues in clinical pharmacology projected a Cmax of approximately 60 pg/ml. Therefore, in order to pursue this strategy, we had to demonstrate that it was possible to develop a cold assay with an LLOQ of 5 pg/ml (based on approximately 4 × t1/2). This we did, the exciting aspect for us being the opportunity to future science group
play a key role in shaping the clinical development strategy, something that does not often happen within bioanalysis, and which was a first for our group. We then had to decide how to validate the assay for each of the three development candidate prodrugs. Given that a micro-dosing study for a specific molecule is only ever likely to be used Discovery Exploratory IND
Screening of qualified assay Qualified assay (animal and human)
Phase 0
Qualified assay (non-GLP/biomarkers) Validated assay (GLP Tox) for parent drug
Phase 1
Qualified assay
Phase 2 Validated assay for parent drug Phase 3
Phase 4
Post-MIST: Validated assay for metabolites requiring quantification based on ICH M3 (R2) guideline
Figure 2. Roadmap showing correlation of tiered assay with stage of drug discovery/development [101] . IND: Investigational new drug; MIST: Metabolites in safety testing.
www.future-science.com
613
Commentary |
Abbott once, it should have been a logical decision to use a qualified assay for this work. However, there was nothing in the official guidance documents to provide assistance in developing the most appropriate strategy for the extent of assay validation and also neither the EBF nor GBC had discussed the concept of tiered approach at the time. Given that we were also dealing with instability issues associated with prodrugs we did not feel comfortable in taking any approach other than full validation. This position was also adopted by our clinical PK colleagues, a position that re-inforced the decision to perform a full validation. However, it must be stated that the concept of a qualified assay was very new to them and that they felt uneasy about taking what was regarded as an abbreviated, lower quality approach. As it turned out, this was far from the case as demonstrated in Tables 2 & 3. Summary data from one of these assay validations is shown below in Table 2 and Table 3 shows data from the first precision and accuracy batch from the same validation work. Clearly, a comparison of data in Tables 2 & 3 demonstrates that a single precision and accuracy batch, following the qualified method approach advocated in Table 1, would have been sufficient to enable the internal decision making following the micro-dosing studies. If a similar situation arose now, I would strongly advocate for the use of the tiered approach and, specifically, the qualified assay, to support a micro-dosing study. Hopefully this example has demonstrated a situation where regulatory concern took precedent over scientific logic. As more is published on the usefulness of the tiered approach, we shold all feel more confident about applying it in practice and defending it during regulatory review.
Looking outside the conventional bioanalytical arena, new diagnostic measurements [14] are being applied in the form of point-of-care devices for personalized medicine [15]. These diagnostic tools often incorporate sophisticated analytical chemistry though the interpretation of the results can pose significant challenges and requires close communication between clinical laboratory scientists and physicians [16]. It would be useful to have a debate about this. How are the diagnostic test results being used, what is the importance of the absolute values being generated, what do we know about their reliability and reproducibility and what is the impact on the patient? At the very least perhaps, some consideration should be given to the use of the tiered approach in validating the data generated in diagnostic investigations. Are the data fully quantitative or semi-quantitative? If a threshold value is important in the subsequent clinical decision making, how well has the diagnostic test been characterized? Finally, a few concluding remarks. We understand the importance of full bioanalytical validation to support regulatory studies where appropriate. However, we can see from this brief commentary article that there are situations in drug development where full validation may not be required, is not necessary, and may divert resources from where they are truly needed. We need to have the freedom to use our judgment to apply scientific and logical arguments for the use of the tiered approach within a scientifically driven method validation strategy. Of course, we should bear in mind the phase of drug development and the nature of the studies being performed as well as any associated risks. Bioanalysis is a quantitative discipline in which we all take great pride.
Table 2. Headline human plasma assay validation study data for active drug X and prodrug (Y). Analyte and statistical parameter
Intraday P&A data (n=3)
Interday P&A data (n=3)
LLOQ
Other QCs
LLOQ
Other QCs
Active drug X (%CV) Active drug X (% bias) Prodrug Y (%CV) Prodrug Y (% bias)
9.5 to 14.5 -8.6 to 8.2 6.0 to 9.2 -0.6 to 12.0
1.3 to 10.5 -12.5 to -2.7 1.4 to 14.3 -11.6 to 5.2
12.8 1.0 9.2 3.8
2.7 to 8.2 -10.5 to -3.5 5.0 to 11.5 -10.0 to -1.2
Stability Bench top Freeze–thaw Long-term frozen Extract reproducibility
At least 4 h acidified plasma stability (ice/water) At least 3 × F/T cycles (-70°C) At least 31 days frozen acidified plasma (-70°C) At least 72 h extract reproducibility (4°C)
Comparison of the full validation data with the data from the first precision and accuracy batch from the same work is shown in Table 3. P&A: Precision and accuracy.
614
Bioanalysis (2014) 6(5)
future science group
Tiered approach: sense & sensibility
| Commentary
Table 3. Single precision and accuracy batch for active drug X and prodrug Y (‘qualification’ batch). Analyte and statistical parameter Active drug X (% CV) Active drug X (% bias) Prodrug Y (% CV) Prodrug Y (% bias)
Intra-day P&A (n = 1) LLOQ
Other QCs
9.7 8.2 9.2 12.0
3.3 to 10.5 -12.5 to -3.5 2.0 to 6.7 -10.0 to –5.2
P&A: Precision and accuracy.
However, we do need to challenge the expectation that every assay we develop will be fully validated, whether necessary or not. Sense and sensibility. Future perspective Assay validation is an integral part of regulatory drug development. For GLP studies and late-phase clinical studies, it is imperative that bioanalytical methods are completely characterized. However, in discovery studies, nonregulated work and other specific cases, as highlighted, it is often neither possible nor necessary to undertake full assay validation. This article has attempted to demonstrate that a tiered approach to method characterization is both reasonable and practical. It does not seek to diminish quality, but provides a strong scientific basis on which to justify the appropriateness of the extent of assay
characterization. In the past, full assay validation has perhaps been attempted when not always necessary because of potential negative consequences. This should not be the major rationale for full assay validation if there is a strong scientific argument for an alternative, such as a qualified or a screening assay. Hopefully as there is greater awareness of the alternatives, along with further regulatory acceptance, the tiered approach will become more common in the future. Financial & competing interests disclosure RW Abbott is an employee of Shire. The author has no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed. No writing assistance was utilized in the production of this manuscript.
References Papers of special note have been highlighted as: n of interest nn of considerable interest 1
A Lady. Sense and Sensibility, Thomas Egerton (1811).
2
US Department of Health and Human Services, US FDA, Center for Drug Evaluation and Research, Center for Veterinary Medicine. Guidance for Industry Bioanalytical Method Validation. Rockville, MD, USA (2001).
3
4
5
US Department of Health and Human services, US FDA, Center for Drug Evaluation and Research, Center for Veterinary Medicine. Guidance for Industry Bioanalytical Method Validation, Draft Guidance, Rockville, MD, USA (2013). Committee for Medicinal Products for Human Use. EMA. Guideline on Bioanalytical Method Validation. London, UK (2011). Ministry of Health, Labour and Welfare. Guideline on Bioanalytical Method Validation in Pharmaceutical Development, Japan (2013).
future science group
6
Agencia Nacional de Vigilancia Sanitaria. Bioanalytical Guidance. RDC27 (2012).
7
Timmerman P, Kall MA, Gordon B, Laakso S, Freisleben A, Hucker RS. Best Practices in a tiered approach to metabolite quantification: views and recommendations of the European Bioanalysis Forum. Bioanalysis 2(7), 1185–1194 (2010).
nn
Contains extremely relevant information for use of the tiered approach.
8
US Department of Health and Human Services, US FDA, Center for Drug Evaluation and Research. Guidance for Industry Safety Testing of Drug Metabolites. Rockville, MD, USA (2008).
9
CPMP/ICH/286/95 – ICH Topic M3 (R2). Non-clinical Safety Studies for the Conduct of Human Clinical Trials and Marketing Authorisation for Pharmaceuticals (2009).
10 Timmerman P, Herling C, Stoellner D et al.
European Bioanalysis Forum recommendation on establishment and bioanalysis of biomarkers in support of drug development. Bioanalysis 4(15), 1883–1894 (2012).
www.future-science.com
n
Provides example of bioanalytical situations where the use of the tiered approach is very logical.
11 Xue Y-J, Gao H, Ji QC et al. Bioanalysis of
drug in tissue: current status and challenges. Bioanalysis 4(21), 2637–2653 (2012). n
Provides example of bioanalytical situations where the use of the tiered approach is very logical.
12 Higton D, Young G, Timmerman P, Abbott
R, Knutsson M, Svensson LD. European Bioanalysis Forum recommendation: scientific validation of quantification by accelerator mass spectrometry. Bioanalysis 4(22), 2669–2679 (2012). n
Provides example of bioanalytical situations where the use of the tiered approach is very logical.
13 US Department of Health and Human
Services, US FDA, Center for Drug Evaluation and Research. Guidance for Industry, Investigators and Reviewers: Exploratory IND Studies, Rockville MD, USA (2006).
615
Commentary |
Abbott
14 Philip R, Carrington L, Chan M. US FDA
perspective on challenges in co-developing in-vitro companion diagnostics and targeted cancer therapeutics. Bioanalysis 3(4), 383–389 (2011). 15 Gomez FA. The future of microfluidic
point-of-care diagnostic devices, Bioanalysis 5(1), 1–3 (2013).
616
16 Reisfield GM, Goldberger BA, Bertholf RL,
‘False-positive’ and ‘false-negative’ test results in clinical urine drug testing, Bioanalysis, 1(5), 937–952 (2009).
www.globalbioanalysisconsortium.org/A2/ final deck for public discussion and input nn
Contains extremely relevant information for use of the tiered approach.
Website 101 Global Bioanalysis Consortium on
harmonization of bioanalytical guidance.
Bioanalysis (2014) 6(5)
future science group
