Bioequivalence and Bioavailability Forum 12:35 CET

Main page Policy/Terms of Use Abbreviations Latest Posts

 Log in |  Register |  Search

cakhatri
Regular

India,
2019-01-10 07:20

Posting: # 19764
Views: 352
 

 Interference from Deuterated IS [Bioanalytics]

Dear All,

Happy New year

I wish to have inputs on the following issue

1. We are currently working on a Drug-Drug Interaction study where Digoxin is the substrate & X is the Perpetrator.

2.During method development we observed around 12-16% interference from Digoxin deuterated (D3) IS at the RT of Digoxin drug. There seems to be no source for D5 or D7 or D11.

3. Inspite of this interference, all the QCs (100%) (Spiked with only Digoxin & Digoxin + X) are meeting the acceptance criteria.

4. Two different sources of Deuterated IS were tested and results are similar.

5. The LOQ that we have selected is 5% of reported Cmax and there is no possibility to increase the same considering guideline recommendations.

6. Digoxin forms an adduct with Ammonia.

7. The MRM pairs are Drug (798.4 / 651.4) & Digoxin D3 (801.4 / 654.4)

8. Mol.wt for Digoxin is 780.94.


My question

1. Would it be advisable to proceed with the validation and will this have impact during sample analysis since all the samples will be spiked with IS.

2. Is there an alternate approach to this scenario ?

Kind Regards
Chirag
VKB2207
Junior

2019-01-10 20:48

@ cakhatri
Posting: # 19767
Views: 293
 

 Interference from Deuterated IS

Hi,

Suggest you not to go with MV in this scenario as IS is contributing and you have no exact idea how much it is contributing. Hence measured concentrations would be inaccurate.

You can probably evaluate the % contribution from IS at RT of drug and then apply this factor in CC, QC nominal concentrations.

Hope it helps.

Regards


Edit: Full quote removed. Please delete everything from the text of the original poster which is not necessary in understanding your answer; see also this post! [Ohlbe]
Ohlbe
Hero

France,
2019-01-10 22:36

@ VKB2207
Posting: # 19769
Views: 294
 

 Interference from Deuterated IS

Dear VKB2207,

» You can probably evaluate the % contribution from IS at RT of drug

Sure. It's called the intercept :-D

» and then apply this factor in CC, QC nominal concentrations.

Certainly not. It is taken into consideration when calculating the calibration curve parameters, unless you are forcing the intercept through 0 (which is not to be done in bioanalysis).

» Hence measured concentrations would be inaccurate.

Not necessarily at high level of concentrations. Could indeed be problematic closer to the LLOQ.

Regards
Ohlbe
Ohlbe
Hero

France,
2019-01-10 23:41

@ cakhatri
Posting: # 19770
Views: 290
 

 Interference from Deuterated IS

Dear Chirag,

» 2.During method development we observed around 12-16% interference from Digoxin deuterated (D3) IS at the RT of Digoxin drug.

That's a rather high level of interference. I'm quite surprised, that's more than I would expect just from isotopic contribution. It does not look like it could be due to another type of adduct, figures do not really match, but I'm not expert enough. Did you check that the deuterium substitution was not done at a labile position, causing deuterium exchange ?

There are several papers describing the use of D3 digoxin as IS. Do the authors report similar levels of interference ? Was their IS marked at the same position ?

Did you try and modify your ion source parameters (e.g. declustering potential) ? Any influence on this % interference ?

Any improvement with an increased MS resolution ? I know it will spoil the LLOQ, but it could help to understand what's going on.

» 3. Inspite of this interference, all the QCs (100%) (Spiked with only Digoxin & Digoxin + X) are meeting the acceptance criteria.

Yes, the interference is compensated by the intercept in your calibration curve. But I would be worried regarding the ruggedness of the method and the reproducibility of the results at low levels of concentration, close to the LLOQ.

» My question
»
» 1. Would it be advisable to proceed with the validation and will this have impact during sample analysis since all the samples will be spiked with IS.

I would first try and understand what's happening, and reduce this % interference as much as possible.

» 2. Is there an alternate approach to this scenario ?

If the authors of published papers report the same issues and there is no possible correction, I would either:
- try and find a provider who would accept to manufacture digoxin marked with more deuterium, or C13,
- or try a structural analogue IS rather than stable-labelled,
- or decrease the interference by decreasing the amount of IS added to the samples.

Or you can try your luck, perform a full validation and see whether it passes, but there is always a risk that any Agency the results will be submitted to will not like it.

If you could keep us informed, it would be appreciated. That's an interesting topic :-)

Regards
Ohlbe
cakhatri
Regular

India,
2019-01-11 09:28

@ Ohlbe
Posting: # 19772
Views: 259
 

 Interference from Deuterated IS

Dear VKB2207 & Ohlbe,

Thanks for your comments.

I shall update on the outcome / resolution

Regards
Chirag
ElMaestro
Hero

Denmark,
2019-01-11 09:49

@ cakhatri
Posting: # 19773
Views: 255
 

 Interference from Deuterated IS

Hello chirag,

may I ask:

» 2.During method development we observed around 12-16% interference from Digoxin deuterated (D3) IS at the RT of Digoxin drug. There seems to be no source for D5 or D7 or D11.

Does the IS increase or decrease the area of the analyte?

» 4. Two different sources of Deuterated IS were tested and results are similar.

What is the purity expressed as DigD3 on your CoA's?

if (3) 4

x=c("Foo", "Bar")
b=data.frame(x)
typeof(b[,1]) ##aha, integer?
b[,1]+1 ##then let me add 1



Best regards,
ElMaestro

"(...) targeted cancer therapies will benefit fewer than 2 percent of the cancer patients they’re aimed at. That reality is often lost on consumers, who are being fed a steady diet of winning anecdotes about miracle cures." New York Times (ed.), June 9, 2018.
Activity
 Thread view
Bioequivalence and Bioavailability Forum |  Admin contact
19,032 posts in 4,059 threads, 1,299 registered users;
online 19 (1 registered, 18 guests [including 12 identified bots]).

When a distinguished but elderly scientist states that
something is possible, he is almost certainly right.
When he states that something is impossible,
he is very probably wrong.    Arthur C. Clarke

The BIOEQUIVALENCE / BIOAVAILABILITY FORUM is hosted by
BEBAC Ing. Helmut Schütz
HTML5 RSS Feed