Bioequivalence and Bioavailability Forum

Dear Konkous,

❝ [...] The back calculated value is always between 83-87% of the nominal value. All weighting factors (1/x, 1/x2, 1/y, 1/y2) applied seem to have more or less the same problem.

Then the problem is not with weighting but with the model itself. A linear model is not always suitable in MS/MS, and a quadratic model can give a better fit and is well accepted. This being said, if you have real problems with the linearity of the detector and the response gets saturated you will have to decrease the ULOQ and dilute study samples.

❝ Assuming that someone has 2 or 3 consecutive runs establishing accepted linearity, accuracy and precision would it be acceptable to start analyzing study samples? Should the complete set of validation runs (consisting of about 8 or 9 runs) be completed prior to main study? Is it acceptable to perform the remaining validation runs after the main study?

You can start analysing your samples before you have the results of the long-term stability. You can also skip dilution integrity, if you think you won't need to dilute any samples in your study. All other parameters should be validated before you start analysing your study samples.

This was discussed at length last year in Brussels at the EBF/EUFEPS meeting with the members of the Writing Committee of EMA's bioanalytical guideline. Industry representatives argued that starting analysing the samples before all validation results are available would be their own risk. Regulators answered that it was not just industry's risk, but there were also some ethical considerations: if you realise after analysing your samples that the method is flawed, and you have no sample volume left to re-analyse, you will have to repeat the study and expose again subjects to the drug, or expose and kill more animals.

Regards
Ohlbe