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Dear all,
I am working on a NCE, validated a LC-MS/MS method in human plasma
for phase I studies with a calibration range of (5 ng - 2 ug/mL),
where we have performed dilution integrity upto 100X.
Using this method SAD samples have been analysed and found that at
higher doses almost 50% of actual samples were diluted by 10X and
some of them were upto 100X, where we have used the appropriate
dilution QCs along with normal set of QCs. All the QCs were passing
the acceptance criteria as per the FDA guide lines.
Here my concern is whether regulatory authorities will have any
objection regarding the dilution of this many samples.
Are there any guide lines on the percentage of samples to be diluted
under a particular calibration curve or in a study.
I am planning to use the same method for analysing MAD samples where
I have to dilute almost 50% of the samples to bring the
concentrations into calibration range.Wether can i go with the same
method or do i need to validate a higher range method.
I request expert comments on this.
Thanks in Advance
Ranjith kumar
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The following message was posted to: PharmPK
Dear ranjith,
As long as the dilution process is appropriately validated
(especially, make sure that the starting concentration of the
"dilution QC" is above the upper limit of quantification), you should
be ok.
However, it could be wise to change the range of the assay to not
waste time diluting samples from your coming studies.
Hope this helps
Gilles
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Dear Ranjith,
In October 2006, I attended a conference in Budapest on Regulatory
Workshop on bioequivalence and dissolution and one of the speaker was
Dr. Vinod Shaw (former Senior Research Scientist with the FDA and
well know for his involvement in bioanalytical community).
After his presentation, I talked with him of a few topics which I had
encountered in various bioanalytical projects previously. One of
those question was regarding "how to approach samples which are
outside your validated method and more precisely, if most of the
samples 50-100% are outside the validated range.
Dr. Shaw mentioned that while diluting your samples and QC (which
have a concentration which is higher that your validated range) is
acceptable, your validated method is from 5 ng/mL to 2000 ng/nL) and
all your stability data (i.e. bench-top, freeze-thaw, recovery,
processed, etc.) obtained for your validation is within that range.
Thus, you have no validation data (except dilution integrity) for
samples which have higher concentration.
Dr. Shaw recommended strongly to revalidate the method with a range
which was adequate with the sample concentration.
I hope this may clarify any doubt you may have regarding your problem.
Best regards,
Sylvain Mandeville, Ph.D.
Lab Research
www.labresearch.com
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Dear Ranjith,
In October 2006, I attended a conference in Budapest on Regulatory
Workshop on bioequivalence and dissolution and one of the speaker was
Dr. Vinod Shaw (former Senior Research Scientist with the FDA and
well know for his involvement in bioanalytical community).
After his presentation, I talked with him of a few topics which I had
encountered in various bioanalytical projects previously. One of
those question was regarding "how to approach samples which are
outside your validated method and more precisely, if most of the
samples 50-100% are outside the validated range.
Dr. Shaw mentioned that while diluting your samples and QC (which
have a concentration which is higher that your validated range) is
acceptable, your validated method is from 5 ng/mL to 2000 ng/nL) and
all your stability data (i.e. bench-top, freeze-thaw, recovery,
processed, etc.) obtained for your validation is within that range.
Thus, you have no validation data (except dilution integrity) for
samples which have higher concentration.
Dr. Shaw recommended strongly to revalidate the method with a range
which was adequate with the sample concentration.
I hope this may clarify any doubt you may have regarding your problem.
Best regards,
Sylvain Mandeville, Ph.D.
Lab Research
www.labresearch.com
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Dear group,
This is a related query for sample dilution. What is the acceptable
way of diluting the sample? I think guideline states same matrix be
used for dilution.
Please consider this scenario: Sample was extracted as such and then
diluted the processed sample with mobile phase. Dilution QC's
similarly processed passes acceptance criteria. Whether this data is
accepted by agencies? If this is acceptable, then one can save lot of
matrix , especially when matrix is unavailable.
Thanks for your comments.
Vinayak
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The following message was posted to: PharmPK
1) You should be able to get an idea of the expected cMax from your PK
driver. It would be conservative to increase this by 10 to 20% as a
hedge,
and generate your Dilutional QC from this.
2) If you validate the dilutional linearity during the method
validation you
would not need to include a dilutional QC in subsequent analytical
batches
unless your required dilution exceeded that which was validated.
3)I agree with Gilles that you should modify the assay dilution to
better
fit the range of values expected for samples. This would require less
sample dilution and lower the cost associated with dilution of the
sample
with matrix.
Ed O'Connor, Ph.D.
Laboratory Director
Matrix BioAnalytical Laboratories
25 Science Park at Yale
New Haven, CT 06511
Web: www.matrixbioanalytical.com
Email: eoconnor.-at-.matrixbioanalytical.com
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The following message was posted to: PharmPK
Dera Ranjith
I suggest you must revalidate the method with new CC range because
more than 50% samples are outside range.
Regards
Vanita
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