Drugs and Health Products
The purpose of this notice is to clarify Health Canada’s interpretation and expectations for all matrix-based stability experiments [that is (i.e.) Long term, Freeze-thaw and Bench top] conducted during bioanalytical method validation.
It has come to the attention of Health Canada that some companies conducting the analysis of bioanalytical samples have used unacceptable procedures during the validation of the analytical method. Specifically, during tests of the stability of drug in biological matrix, some companies have employed the procedure of subjecting only one bulk Quality Control (QC) sample at each concentration to the stability conditions and taking multiple aliquots from that sample. This practice produces repeated measurements from a single replicate, but does not produce multiple replicates of the storage conditions. Therefore, it provides limited (i.e., N = 1) information regarding the effects of the storage conditions on accuracy and no information on the effects of the conditions on the variability of the drug concentration. Any variability in the repeated measurements of a single sample results not from the storage conditions, but from observational error (i.e., variability inherent to the analytical method). This is not considered to be sufficient evidence of stability.
Any scientific study of the effects of an independent variable on a given outcome requires appropriate replication to determine a precise estimate of the effect. In analytical method validation, the purpose of stability studies is to evaluate the effect of storage conditions on the accuracy and variability of the drug concentrations in biological samples. This assessment requires multiple replicates of the storage conditions (i.e., separate tubes each containing a pre-specified concentration of drug in relevant biological matrix). Therefore, in the case of stability experiments, sets of low and high QC samples, consisting of multiple replicates at each concentration, should be aliquoted prior to the stability experiment and a minimum of three samples should be subjected independently to the stability conditions that are to be evaluated.
The Health Canada Guidance for Industry Conduct and Analysis of Comparative Bioavailability Studies (2012) stipulates that the principles and procedures for bioanalytical method validation and analysis of study samples described in the European Medicines Agency Guideline on bioanalytical method validation should be followed. While guidance documents such as these are not intended to and cannot enumerate all important aspects of good scientific practices, Health Canada nevertheless expects sound scientific practices and experimental design to be applied in studies submitted in support of drug submissions.
For all method validations where only one tube of test QC samples at each concentration was subjected to the stability conditions, the validation is considered deficient. In these cases, an amendment to the validation report will be requested that includes stability experiments conducted using sets of low and high QC samples aliquoted prior to the stability experiment and all samples subjected to the given stability conditions independently prior to processing.