Bioequivalence and Bioavailability Forum

Hi Outlaw & all!

❝ On a side note, does anyone have actual experience with the authorities concerning lack of ISR justifications?

Last Friday (today is day 100): Line extension of an MR formulation (racemate), two studies (single & multiple dose), stable-isotope IS chiral GC/MS method (BE based on the active enan­tio­mer d-█████).

• SD: analytical part finished April 2010, 558 samples, no ISR
  
• MD: finished June 2011, 656 samples, 5% ISR, d-enantiomer deviation -2.75% (±6.80 [-15.58%, +11.13%]) and l-enantiomer +1.19% (±7.61 [-14.04%, +12.89%]).
  100% of both enantiomers’ ISR within ±20%.

So far accepted by RMS Germany¹ and CMSs Austria, Denmark, Sweden, Spain.
But The Netherlands:

PSRPH:
Bioequivalence is considered not demonstrated in the single-dose study due to the absence of incurred sample reanalysis (ISR). The Applicant should discuss the vali­di­ty of the bio­­analytical method in the absence of ISR, taking into account the dis­cus­sion points in the PKWP Q&A document (EMA/618604/2008 Rev. 7).
Rationale:
The Applicant did not provide justification for the absence of ISR. According to the RMS, the absence of ISR is acceptable as the PK data is robust, back conversion of meta­bolites is not a significant issue for █████ and the study has been conducted in 2010. This is not agreed. The current guideline of bioanalytical method [sic] (EMEA/CHMP/EWP/192217/2009)² came into effect on February 1, 2012. All app­li­ca­tions submitted after this date should comply to the guideline, irrespective of the time of study. The Applicant should discuss, in the absence of ISR, the validity of the bioanalytical method concerning the precision and accuracy of the study samples during processing and storage taking into account the discussion points in the PKWP Q&A document (EMA/618604/2008 Rev. 6).
Additional points for clarification:
[Study #2] Only 5% of the samples were used for ISR. The Guideline on bio­analyti­cal method validation requires³ 10% of the samples. The Applicant should therefore provide a justification that the number of reanalysed samples used sufficiently re­flects the accuracy and precision of the analyte in all the samples during processing and storage.

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1. From the RMS’s PAR: Regarding the standard pharmacokinetic variables bioequivalence has undisputably [sic] been shown. The results are rather robust and statistical analysis indicate no significant difference.
   Moreover the shape of the plasma profiles are similar and the statistical evaluation of the advanced pharmacokinetic variables which reflect the biphasic drug liberation of the dosage form (e.g. AUC_0-4, AUC_4-t, C_max(0-4) and C_max(4-t)) are […] well within con­ven­tio­nal acceptance criteria.
   The applicant performed no Incurred Sample Reanalysis. This [is] considered accept­able due to the robust PK data, the convincing results of pre- and in-study validation, the fact that the study has been conducted in 2010 and that back conversion of metab­olites is not a significant issue for █████.
   
2. Dated 21 July 2011 and published by EMA on 1 August 2011. A f**ing time machine would have been required for writing the analytical protocol back in April 2011. No per­cent­age at all was suggested in the 2009 draft.
   
3. Requires?? WTF? I only read “The extent of testing depends on the analyte and the study samples, and should be based upon in-depth understanding of the analytical method and analyte. However, as a guide, 10% of the samples should be reanalysed in case the number of samples is less than 1000 samples and 5% of the number of samples exceeding 1000 samples.”
   The method is robust (used in ~20 studies in many thousands of samples; not a single batch ever repeated). A back-conversion of the main metabolite in sample pro­cessing is not possible (selective chiral derivatization step). The CV_intra of the API (in­de­pen­dent from the formulation – various IRs and MRs) is very – very! – low.
   With such a mean & SD it is improbable to get even a single repeat with a deviation >20% (6σ ) and almost impossible to get more than ⅓ repeats outside…
   
   Do I really have to come up with a simulation (~10% repeats) showing the probability of ISR outside the acceptance range (>20% deviation in ⅓ of samples) based on the observed x -2.75% and SD 6.80%?
   data   <- c(-1.05,  -6.38, -5.30,  -5.55,  -2.99,  -2.24, +10.75, +0.90,
            -6.66,  -5.01, -2.74, -10.98,  +4.43,  -3.53,  -8.85, -7.38,
            -8.35, +11.13, -4.07, -15.58,  +2.05, -14.86,  -3.34, +2.66,
            -6.80,  +5.60, -2.48,  +5.61, -11.71, +10.61,  -4.00, -1.73)
                            # Observed deviations
mean   <- mean(data)/100    # Mean deviation
sd     <- sd(data)/100      # SD of deviations
size   <- 656               # No. of samples in a study
ifelse(size < 1000,         # EMA: 10% if <1000; +5% for >1000
  ISR.no <- ceiling(size*0.1),
  ISR.no <- 100 + ceiling((size-1000)*0.05))
sims   <- 1e6               # No. of simulated studies
failed <- 0                 # ISR failed criterion (≤1/3 of repeats >20% dev.)
for (i in 1:sims) {
  x      <- 100*rnorm(n=ISR.no, mean=mean, sd=sd)
  y      <- length(x[abs(x)>20]) # No. of abs. deviations > 20%
  y      <- y/ISR.no        # Fraction of repeats with > 20% deviation
  if (y > 1/3) failed <- failed + 1
}
cat(formatC(sims, format="d", big.mark=","), "simulated studies with",
  size, "samples:\n",
  "Method: Pseudorandom (Mersenne-Twister) samples from normal distribution\n",
  sprintf("%i", ISR.no), "ISR repeats based on the observed mean of",
  sprintf("%.2f%%", 100*mean), "with a standard deviation of",
  sprintf("%.2f%%%s%i%s", 100*sd, " (n=", length(data),").\n"),
  "Failed criterion (deviations >20% in >1/3 of repeats) seen in",
  sprintf("%.2f%% %s", 100*failed, "of studies.\n"))
   
   Which – as expected – tells me:
   1,000,000 simulated studies with 656 samples:
 Method: Pseudorandom (Mersenne-Twister) samples from normal distribution
 66 ISR repeats based on the observed mean of -2.75% with a standard deviation
 of 6.80% (n=32).
 Failed criterion (deviations >20% in >1/3 of repeats) seen in 0.00% of
 studies.