Commentary For reprint orders, please contact [email protected]
Bioanalysis Zone: DBS survey results Bioanalysis Zone carried out a survey to evaluate the use of and attitudes to DBS analysis among our readership in the bioanalytical community. DBS analysis has generated a huge amount of interest in recent years. We wanted to take a snapshot of the field and determine whether a consensus is emerging on the future of DBS. We asked you for your honest opinions and you delivered! You can view the full results at www.bioanalysis-zone.com. We have a selection of short opinion articles below, giving a range of viewpoints on the current and future use of DBS, alongside some of the survey results. Is the future bright for DBS? Philip Denniff (GlaxoSmithKline) E-mail: [email protected]
I am convinced that microsampling, particularly for small animal and pediatric studies, is here to stay. The advantages in animal welfare are too great to be ignored and this coupled with the resulting improvement in data quality are an added bonus. DBS ticks all the boxes for a microsampling technique, but it also has a number of drawbacks when operated in its optimal sub-punch, rather than whole-spot elution mode. The sub-punch elution approach has the advantage that there is no need to apply an accurate volume of blood to the card at the time of sampling, but it suffers from the fact that variations in sample hematocrit introduce an assay bias. Although this assay bias would be considerable if the samples had a hematocrit at one end of the scale and were assayed against standards at the other end, the bias can be limited to manageable levels by preparing standards at the center of the expected sample hematocrit range.
advantage that it compensates for any possible variability in homogeneity within the spot itself. On that point, the homogeneity of the spot is a contributor to the overall precision of the process. Thus, if the within run CV is acceptable, so is the homogeneity. It is heartening to see that a number of substrates and techniques have recently appeared that compensate for the bias caused by changes in hematocrit, and it may well be one of these that drives the next generation of dried sample analysis. Pharmacokinetics Clinical Animal studies Preclinical studies Neonatal screening Pediatrics Toxicology Drug discovery Drug monitoring Sample preparation Non-clinical
“The advantages in animal welfare are too great to be ignored and this coupled with the resulting improvement in data quality are an added bonus.”
Biomarker ID/quantification Protein detection Proteomics None Other
Furthermore, a typical hematocrit range within a particular sample set is unlikely to be that wide, and seldom will it cover more than half the theoretical hematocrit range. Alternatively, the assay bias can be compensated for by applying an accurate volume of blood to the sample card at the time the sample is generated and extracting the whole of the dried sample. The whole spot approach also has the 10.4155/BIO.13.327 © 2014 Future Science Ltd
Reducing the use of animals was a key factor in using DBS in preclinical studies.
Primary APPLICATION Respondents indicated a wide range of applications for DBS; the most common being pharmacokinetic studies (22%) but there were many other applications, including pediatrics, clinical studies and therapeutic drug monitoring.
Bioanalysis (2014) 6(3), 287–291
ISSN 1757-6180
287
Denniff, Holliman, Svensson, Weng & Patel
“As the Bioanalysis Zone survey affirms, the
Gathering information
I do not think so. I do not believe the advantages of DBS are compelling to the clinical organization. As the Bioanalysis Zone survey affirms, the bioanalytical community sees the primary advantages of DBS sampling as a cost-saving measure for the clinic. DBS sampling offers improved subject recruitment, ease of sampling, reduced collection volume, and ambient-temperature shipping and storage. Combined, these would result in significant savings for a large-scale, multi-site, clinical program. So why then is not the clinic not increasing pressure on the regulatory agencies and bioanalytical laboratories to accelerate the implementation of DBS sampling? I believe it is because cost savings during human trials is not the primary economic driver for the clinic in the current environment of increased regulatory and healthcare system scrutiny.
Evaluating technique
Chris Holliman (Pfizer) E-mail: [email protected]
Even if timelines from first dose to submission are not impacted by the DBS approach, it is unlikely the human clinic will on a routine basis be willing to take on the additional regulatory uncertainty and scrutiny introduced by DBS sampling solely for the sake of cost savings. Especially given that the clinical organization is typically the most risk-adverse function in a company. If we build it will the clinic come? I sincerely doubt it. The economic benefits of DBS for regulated preclinical and human trials are uncertain, while the bioanalytical shortcomings and regulatory risks are clear. While potentially useful for specific applications (e.g. pediatric studies), it’s unlikely that DBS will ever be the routine sampling strategy of choice in a clinical PK setting.
Use occasionally
DBS sampling: if we build it will the clinic come?
Use routinely
Commentary |
15%
20%
24%
11%
288
Bioanalysis (2014) 6(3)
17%
13%
No interest
The primary economic driver for the design of a human clinical program is extending market exclusivity by reducing the timeline from first dose to regulatory submission, review and approval. The clinic values confidence in execution, confidence in bioanalysis, regulatory certainty and speed. As noted in the survey, questions regarding sample integrity and spot homogeneity based on permutations of hematocrit, humidity, temperature variations and so on, continue to produce a level of uncertainty for the clinic. Even if the entire spot is analyzed, respondents recognize that the difficulty or inability to create a homogenous addition of an IS, a homogeneous matrix dilution and the inability to perform a true incurred reanalysis are bioanalytical shortcomings and will always induce regulatory discomfort and increased scrutiny. For these reasons I don’t believe DBS sampling will ever achieve the confidence that the clinic and regulatory agencies have acquired for liquid samples. As a result, I believe that DBSbased submissions will always carry a higher risk of post-submission regulatory requests for additional data, comparative studies, and longer approval times than traditional plasma-based submissions.
Stopped using
bioanalytical community sees the primary advantages of DBS sampling as a cost-saving measure for the clinic.”
70% of respondents use DBS in some way or were considering doing so
Level of INTEREST Filtered by company sector: Clinical diagnostics companies were most likely to be using the technique routinely. 50% of respondents in biotechnology were evaluating the technique. CROs were most likely to have stopped using DBS altogether.
future science group
Bioanalysis Zone: DBS survey results
future science group
When we compare the routines for collecting plasma samples versus DBS, we notice that the DBS routine is far simpler. The routine for collecting plasma starts with sampling whole blood in a heparin test tube. The plasma is then separated by means of centrifugation and put on dry ice, awaiting transfer to a deep freezer. In this routine there are several opportunities to make mistakes, for example, the sample identity labeling from whole blood to plasma is corrupted,
MOST people use DBS for preclinical work
32%
DMPK 48%
ADME
33% 21%
28%
22%
19%
Phase III Phase II Phase I
Discovery
DBS is a very promising approach for collecting exposure samples for a clinical study. The main obstacle today seems to be that we do not know if relevant authorities will understand and accept the approach of DBS, even in a fully validated application. Whether DBS can be the future standard approach in sample handling, depends of course, on the physicochemical properties of DBS. Ever since I joined the bioanalytical community in the mid-1970s, there has been an issue of how to handle plasma samples i.e. how to secure the dispatch of samples, how to store samples, how to thaw samples, how to evaluate hemolytic samples, how to dispose of sample surplus etc. We do not yet know the end of the DBS story, but what has been reported so far looks very promising. It seems that this ‘novel’ approach matches deep frozen plasma, in most respects. Today, we have a limited experience of DBS compared with frozen plasma, but from what I have seen in the laboratory so far I am full of expectation when it comes to future DBS applications. When we consider sample collection and sample dispatch to a central bioanalytical laboratory, DBS minimizes the costs, and the simplicity gives increased quality. Let us for example assume a clinical Phase III study comprising 1200 subjects. It would be reasonable to collect five samples per subject on average, from 200 clinical sites. Additionally, we cannot put the bioanalysis on hold until the study is complete (i.e., we must at least dispatch samples at three occasions). This means 6000 samples divided into 600 dispatches. If we assume that every dispatch of deep frozen plasma on dry ice with a temperature log costs €1000, this totals €600,000. If we assume that one target analysis at a CRO costs €70, the bioanalytical cost totals €420,000 This means that in an ordinary clinical Phase III study, the
approach is fully accepted and understood by quality assurance departments and regulatory authorities, and that the scientific rational holds, it will simplify life in the bioanalytical community and increase data quality.”
Preclinical
Leif Svensson (Active Biotech AB) E-mail: [email protected]
“Let us be optimistic and assume that the DBS
Clinical
DBS is sound science but also sound economics
cost for the bioanalysis is lesser than the cost for the dispatches of the samples. If we apply the DBS approach, we could simply put the samples in the mailbox at no cost at all.
Approval
Nevertheless, the Bioanalysis Zone DBS survey respondents are optimistic that DBS will remain a viable bioanalytical sampling strategy, especially in the nonregulated study space. Here, the impressive body of DBS research and characterization will serve the bioanalytical community well for the application of dried matrix spots as a ‘fit-for-purpose’ microsampling strategy.
| Commentary
Too many issues need to be addressed before it can enter mainstream bioanalysis Therapeutic drug monitoring 29%
11%
8%
Bioequivalence Post-marketing support
Stage of DRUG DEVELOPMENT
www.future-science.com
289
Commentary |
Denniff, Holliman, Svensson, Weng & Patel there is hemolysis in the whole blood, the drug is degraded during centrifugation, the test tube is forgotten in the centrifuge for a period of time or the labeling is not resistant to condensed humidity. It is much simpler to put a drop of blood on a paper that is properly labeled with subject, date and time. A procedure simplification like this will almost by definition increase quality of end data. I have fully investigated DBS in one application (to be published) and found that DBS in this application fully matches frozen plasma when it comes to: n Method development and validation; Method yield and LOD;
most practitioners are either at learning/early adoption or selective use stages, or some even at a skeptical phase of this technology. DBS is being recognized and is also included as an example in the new technology section of the recent US FDA draft guidance for bioanalytical method validation. It calls for comparative studies with plasma, performed for DBS and other established technologies, as stated by the FDA in several previous meetings. This added burden of conducting comparative studies makes many hesitant to adopt this technology. The survey certainly reflects the confusing and conflicting messages that the bioanalytical community received from the various regulatory bodies.
n
Sample throughput;
n
Storage stability of spiked samples;
n
Reanalysis of incurred samples;
n
Stability of incurred samples. And I also recognize that DBS overthrow frozen plasma when it comes to: n The collecting and the labeling of samples;
“This survey, quite timely, accurately reflects the current diversified and sometimes confused views of DBS in the bioanalytical community.”
n
The dispatch and reception of samples;
n
Sample preparation to an analytical extract;
n
Matrix simplicity (LC–MS/MS analysis). Let us be optimistic and assume that the DBS approach is fully accepted and understood by quality assurance departments and regulatory authorities, and that the scientific rational holds, it will simplify life in the bioanalytical community and increase data quality. n
What is the future of DBS? Naidong Weng* & Shefali Patel (Janssen Pharmaceutical R&D) *Author for correspondence: E-mail: [email protected]
DBS, though having been used for infant screening for many years in the clinical diagnostics area, is an available tool and is only being recently explored by the bioanalytical community. Yet, in the last few years, it has generated much debate, not only among the pharmaceutical companies, but also within the regulatory bodies. This survey, quite timely, accurately reflects the current diversified and sometimes confused views of DBS in the bioanalytical community. While a few brave pioneers applied DBS for regulated GLP and bioequivalence studies, 290
Bioanalysis (2014) 6(3)
The merits of using DBS are well-documented in the literature, however so are clear scientific issues such as impact of hematocrit, changes to spot homogeneity, extraction recovery, long term stability/recovery and so on. Some more technical challenges include addition of IS, drying process, dilution integrity, incurred sample reanalysis, just to name a few, which are never concerns for conventional plasma assays. The nature of paper-based cards, along with dried matrix, presents some unique challenges for DBS-based bioanalysis. None of these technical or scientific issues are unresolvable, although longer time may be needed in comparison with plasma assays. Therefore, careful planning would be needed to avoid shifting bioanalysis back to the critical path of the program development. In our laboratory, we have observed the time-dependent extraction recovery upon the storage of the DBS cards. A method that was optimized and validated using relatively fresh QCs (within a few days) was no longer appropriate to be used for analyzing incurred samples. There are certainly other parameters that need to be carefully considered, evaluated and mitigated if they posed negative impacts to the DBS methods. Otherwise, method-development timelines could be shifted upstream significantly, a task not easy to implement at today’s resource-tight bioanalytical laboratories. The last comment we would like to make is that, in our opinions, DBS attracted unnecessary attentions from the bioanalytical community, future science group
Bioanalysis Zone: DBS survey results
9% 91%
Not required Concerns about acceptibility for regulatory agencies Technology not validated Client/sponsor decision FDA does not have Still evaluating much confidence Other in DBS
30% of respondents from the UK used DBS in a regulatory submission, compared with only 6% in the USA
REGULATORY BODIES
a regulatory submission?
are intended for developing countries where classic blood drawing may be a challenge, drugs/metabolites that are labile in plasma matrix but stable in DBS, and many of the early nonclinical studies. As a supplementary tool and with appropriate method validation, DBS may have the potential to reduce the study cost and facilitate a healthy dialogue with the regulatory bodies.
ATTITUDES OF
Have you used DBS for
WHY NOT?
with a high but unrealistic hope it would replace plasma as the PK sampling matrix. Unfortunately, even with many merits of DBS, this technology would be much better off today to be positioned as a supplementary tool, but not as a replacement technology. DBS can find its niche and can be very valuable for some studies. Examples may include pediatric studies with limited sample volumes, drug candidates that
| Commentary
Over confident 1% Appropriate to technology 49% Over cautious 31%
REGULATORY issues Very few respondents had used DBS for a regulatory submission, although reasons for this varied. Most felt that regulatory attitudes are appropriate to the current level of technology, although 31% felt that they were over-cautious.
Disclaimer The opinions expressed in this article are those of the authors and do not necessarily reflect the views of Future Science Ltd.
Financial & competing interests disclosure The authors have no 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. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties. No writing assistance was utilized in the production of this manuscript.
future science group
www.future-science.com
291
Bioanalysis Zone: DBS survey results Bioanalysis Zone carried out a survey to evaluate the use of and attitudes to DBS analysis among our readership in the bioanalytical community. DBS analysis has generated a huge amount of interest in recent years. We wanted to take a snapshot of the field and determine whether a consensus is emerging on the future of DBS. We asked you for your honest opinions and you delivered! You can view the full results at www.bioanalysis-zone.com. We have a selection of short opinion articles below, giving a range of viewpoints on the current and future use of DBS, alongside some of the survey results. Is the future bright for DBS? Philip Denniff (GlaxoSmithKline) E-mail: [email protected]
I am convinced that microsampling, particularly for small animal and pediatric studies, is here to stay. The advantages in animal welfare are too great to be ignored and this coupled with the resulting improvement in data quality are an added bonus. DBS ticks all the boxes for a microsampling technique, but it also has a number of drawbacks when operated in its optimal sub-punch, rather than whole-spot elution mode. The sub-punch elution approach has the advantage that there is no need to apply an accurate volume of blood to the card at the time of sampling, but it suffers from the fact that variations in sample hematocrit introduce an assay bias. Although this assay bias would be considerable if the samples had a hematocrit at one end of the scale and were assayed against standards at the other end, the bias can be limited to manageable levels by preparing standards at the center of the expected sample hematocrit range.
advantage that it compensates for any possible variability in homogeneity within the spot itself. On that point, the homogeneity of the spot is a contributor to the overall precision of the process. Thus, if the within run CV is acceptable, so is the homogeneity. It is heartening to see that a number of substrates and techniques have recently appeared that compensate for the bias caused by changes in hematocrit, and it may well be one of these that drives the next generation of dried sample analysis. Pharmacokinetics Clinical Animal studies Preclinical studies Neonatal screening Pediatrics Toxicology Drug discovery Drug monitoring Sample preparation Non-clinical
“The advantages in animal welfare are too great to be ignored and this coupled with the resulting improvement in data quality are an added bonus.”
Biomarker ID/quantification Protein detection Proteomics None Other
Furthermore, a typical hematocrit range within a particular sample set is unlikely to be that wide, and seldom will it cover more than half the theoretical hematocrit range. Alternatively, the assay bias can be compensated for by applying an accurate volume of blood to the sample card at the time the sample is generated and extracting the whole of the dried sample. The whole spot approach also has the 10.4155/BIO.13.327 © 2014 Future Science Ltd
Reducing the use of animals was a key factor in using DBS in preclinical studies.
Primary APPLICATION Respondents indicated a wide range of applications for DBS; the most common being pharmacokinetic studies (22%) but there were many other applications, including pediatrics, clinical studies and therapeutic drug monitoring.
Bioanalysis (2014) 6(3), 287–291
ISSN 1757-6180
287
Denniff, Holliman, Svensson, Weng & Patel
“As the Bioanalysis Zone survey affirms, the
Gathering information
I do not think so. I do not believe the advantages of DBS are compelling to the clinical organization. As the Bioanalysis Zone survey affirms, the bioanalytical community sees the primary advantages of DBS sampling as a cost-saving measure for the clinic. DBS sampling offers improved subject recruitment, ease of sampling, reduced collection volume, and ambient-temperature shipping and storage. Combined, these would result in significant savings for a large-scale, multi-site, clinical program. So why then is not the clinic not increasing pressure on the regulatory agencies and bioanalytical laboratories to accelerate the implementation of DBS sampling? I believe it is because cost savings during human trials is not the primary economic driver for the clinic in the current environment of increased regulatory and healthcare system scrutiny.
Evaluating technique
Chris Holliman (Pfizer) E-mail: [email protected]
Even if timelines from first dose to submission are not impacted by the DBS approach, it is unlikely the human clinic will on a routine basis be willing to take on the additional regulatory uncertainty and scrutiny introduced by DBS sampling solely for the sake of cost savings. Especially given that the clinical organization is typically the most risk-adverse function in a company. If we build it will the clinic come? I sincerely doubt it. The economic benefits of DBS for regulated preclinical and human trials are uncertain, while the bioanalytical shortcomings and regulatory risks are clear. While potentially useful for specific applications (e.g. pediatric studies), it’s unlikely that DBS will ever be the routine sampling strategy of choice in a clinical PK setting.
Use occasionally
DBS sampling: if we build it will the clinic come?
Use routinely
Commentary |
15%
20%
24%
11%
288
Bioanalysis (2014) 6(3)
17%
13%
No interest
The primary economic driver for the design of a human clinical program is extending market exclusivity by reducing the timeline from first dose to regulatory submission, review and approval. The clinic values confidence in execution, confidence in bioanalysis, regulatory certainty and speed. As noted in the survey, questions regarding sample integrity and spot homogeneity based on permutations of hematocrit, humidity, temperature variations and so on, continue to produce a level of uncertainty for the clinic. Even if the entire spot is analyzed, respondents recognize that the difficulty or inability to create a homogenous addition of an IS, a homogeneous matrix dilution and the inability to perform a true incurred reanalysis are bioanalytical shortcomings and will always induce regulatory discomfort and increased scrutiny. For these reasons I don’t believe DBS sampling will ever achieve the confidence that the clinic and regulatory agencies have acquired for liquid samples. As a result, I believe that DBSbased submissions will always carry a higher risk of post-submission regulatory requests for additional data, comparative studies, and longer approval times than traditional plasma-based submissions.
Stopped using
bioanalytical community sees the primary advantages of DBS sampling as a cost-saving measure for the clinic.”
70% of respondents use DBS in some way or were considering doing so
Level of INTEREST Filtered by company sector: Clinical diagnostics companies were most likely to be using the technique routinely. 50% of respondents in biotechnology were evaluating the technique. CROs were most likely to have stopped using DBS altogether.
future science group
Bioanalysis Zone: DBS survey results
future science group
When we compare the routines for collecting plasma samples versus DBS, we notice that the DBS routine is far simpler. The routine for collecting plasma starts with sampling whole blood in a heparin test tube. The plasma is then separated by means of centrifugation and put on dry ice, awaiting transfer to a deep freezer. In this routine there are several opportunities to make mistakes, for example, the sample identity labeling from whole blood to plasma is corrupted,
MOST people use DBS for preclinical work
32%
DMPK 48%
ADME
33% 21%
28%
22%
19%
Phase III Phase II Phase I
Discovery
DBS is a very promising approach for collecting exposure samples for a clinical study. The main obstacle today seems to be that we do not know if relevant authorities will understand and accept the approach of DBS, even in a fully validated application. Whether DBS can be the future standard approach in sample handling, depends of course, on the physicochemical properties of DBS. Ever since I joined the bioanalytical community in the mid-1970s, there has been an issue of how to handle plasma samples i.e. how to secure the dispatch of samples, how to store samples, how to thaw samples, how to evaluate hemolytic samples, how to dispose of sample surplus etc. We do not yet know the end of the DBS story, but what has been reported so far looks very promising. It seems that this ‘novel’ approach matches deep frozen plasma, in most respects. Today, we have a limited experience of DBS compared with frozen plasma, but from what I have seen in the laboratory so far I am full of expectation when it comes to future DBS applications. When we consider sample collection and sample dispatch to a central bioanalytical laboratory, DBS minimizes the costs, and the simplicity gives increased quality. Let us for example assume a clinical Phase III study comprising 1200 subjects. It would be reasonable to collect five samples per subject on average, from 200 clinical sites. Additionally, we cannot put the bioanalysis on hold until the study is complete (i.e., we must at least dispatch samples at three occasions). This means 6000 samples divided into 600 dispatches. If we assume that every dispatch of deep frozen plasma on dry ice with a temperature log costs €1000, this totals €600,000. If we assume that one target analysis at a CRO costs €70, the bioanalytical cost totals €420,000 This means that in an ordinary clinical Phase III study, the
approach is fully accepted and understood by quality assurance departments and regulatory authorities, and that the scientific rational holds, it will simplify life in the bioanalytical community and increase data quality.”
Preclinical
Leif Svensson (Active Biotech AB) E-mail: [email protected]
“Let us be optimistic and assume that the DBS
Clinical
DBS is sound science but also sound economics
cost for the bioanalysis is lesser than the cost for the dispatches of the samples. If we apply the DBS approach, we could simply put the samples in the mailbox at no cost at all.
Approval
Nevertheless, the Bioanalysis Zone DBS survey respondents are optimistic that DBS will remain a viable bioanalytical sampling strategy, especially in the nonregulated study space. Here, the impressive body of DBS research and characterization will serve the bioanalytical community well for the application of dried matrix spots as a ‘fit-for-purpose’ microsampling strategy.
| Commentary
Too many issues need to be addressed before it can enter mainstream bioanalysis Therapeutic drug monitoring 29%
11%
8%
Bioequivalence Post-marketing support
Stage of DRUG DEVELOPMENT
www.future-science.com
289
Commentary |
Denniff, Holliman, Svensson, Weng & Patel there is hemolysis in the whole blood, the drug is degraded during centrifugation, the test tube is forgotten in the centrifuge for a period of time or the labeling is not resistant to condensed humidity. It is much simpler to put a drop of blood on a paper that is properly labeled with subject, date and time. A procedure simplification like this will almost by definition increase quality of end data. I have fully investigated DBS in one application (to be published) and found that DBS in this application fully matches frozen plasma when it comes to: n Method development and validation; Method yield and LOD;
most practitioners are either at learning/early adoption or selective use stages, or some even at a skeptical phase of this technology. DBS is being recognized and is also included as an example in the new technology section of the recent US FDA draft guidance for bioanalytical method validation. It calls for comparative studies with plasma, performed for DBS and other established technologies, as stated by the FDA in several previous meetings. This added burden of conducting comparative studies makes many hesitant to adopt this technology. The survey certainly reflects the confusing and conflicting messages that the bioanalytical community received from the various regulatory bodies.
n
Sample throughput;
n
Storage stability of spiked samples;
n
Reanalysis of incurred samples;
n
Stability of incurred samples. And I also recognize that DBS overthrow frozen plasma when it comes to: n The collecting and the labeling of samples;
“This survey, quite timely, accurately reflects the current diversified and sometimes confused views of DBS in the bioanalytical community.”
n
The dispatch and reception of samples;
n
Sample preparation to an analytical extract;
n
Matrix simplicity (LC–MS/MS analysis). Let us be optimistic and assume that the DBS approach is fully accepted and understood by quality assurance departments and regulatory authorities, and that the scientific rational holds, it will simplify life in the bioanalytical community and increase data quality. n
What is the future of DBS? Naidong Weng* & Shefali Patel (Janssen Pharmaceutical R&D) *Author for correspondence: E-mail: [email protected]
DBS, though having been used for infant screening for many years in the clinical diagnostics area, is an available tool and is only being recently explored by the bioanalytical community. Yet, in the last few years, it has generated much debate, not only among the pharmaceutical companies, but also within the regulatory bodies. This survey, quite timely, accurately reflects the current diversified and sometimes confused views of DBS in the bioanalytical community. While a few brave pioneers applied DBS for regulated GLP and bioequivalence studies, 290
Bioanalysis (2014) 6(3)
The merits of using DBS are well-documented in the literature, however so are clear scientific issues such as impact of hematocrit, changes to spot homogeneity, extraction recovery, long term stability/recovery and so on. Some more technical challenges include addition of IS, drying process, dilution integrity, incurred sample reanalysis, just to name a few, which are never concerns for conventional plasma assays. The nature of paper-based cards, along with dried matrix, presents some unique challenges for DBS-based bioanalysis. None of these technical or scientific issues are unresolvable, although longer time may be needed in comparison with plasma assays. Therefore, careful planning would be needed to avoid shifting bioanalysis back to the critical path of the program development. In our laboratory, we have observed the time-dependent extraction recovery upon the storage of the DBS cards. A method that was optimized and validated using relatively fresh QCs (within a few days) was no longer appropriate to be used for analyzing incurred samples. There are certainly other parameters that need to be carefully considered, evaluated and mitigated if they posed negative impacts to the DBS methods. Otherwise, method-development timelines could be shifted upstream significantly, a task not easy to implement at today’s resource-tight bioanalytical laboratories. The last comment we would like to make is that, in our opinions, DBS attracted unnecessary attentions from the bioanalytical community, future science group
Bioanalysis Zone: DBS survey results
9% 91%
Not required Concerns about acceptibility for regulatory agencies Technology not validated Client/sponsor decision FDA does not have Still evaluating much confidence Other in DBS
30% of respondents from the UK used DBS in a regulatory submission, compared with only 6% in the USA
REGULATORY BODIES
a regulatory submission?
are intended for developing countries where classic blood drawing may be a challenge, drugs/metabolites that are labile in plasma matrix but stable in DBS, and many of the early nonclinical studies. As a supplementary tool and with appropriate method validation, DBS may have the potential to reduce the study cost and facilitate a healthy dialogue with the regulatory bodies.
ATTITUDES OF
Have you used DBS for
WHY NOT?
with a high but unrealistic hope it would replace plasma as the PK sampling matrix. Unfortunately, even with many merits of DBS, this technology would be much better off today to be positioned as a supplementary tool, but not as a replacement technology. DBS can find its niche and can be very valuable for some studies. Examples may include pediatric studies with limited sample volumes, drug candidates that
| Commentary
Over confident 1% Appropriate to technology 49% Over cautious 31%
REGULATORY issues Very few respondents had used DBS for a regulatory submission, although reasons for this varied. Most felt that regulatory attitudes are appropriate to the current level of technology, although 31% felt that they were over-cautious.
Disclaimer The opinions expressed in this article are those of the authors and do not necessarily reflect the views of Future Science Ltd.
Financial & competing interests disclosure The authors have no 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. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties. No writing assistance was utilized in the production of this manuscript.
future science group
www.future-science.com
291
