PK Assay Validation: Your Key to Regulatory Success in Drug Development
Accurate and precise determination of pharmacokinetic parameters depends on reliable bioanalytical methods such as digital PCR analysis and liquid chromatography-mass spectrometry assay. LC-MS bioanalysis employs liquid chromatography to separate components and mass spectrometry to determine them based on their mass-to-charge ratio. Today, LC-MS sample analysis is routine in bioanalytical testing. However, LC-MS method development and LC-MS method validation remain critical for ensuring reliable and accurate PK analysis. In addition, hyphenated approaches will also require LC-MS/MS method validation to support bioanalysis.
Bioanalytical assays should be thoroughly validated for pharmacokinetic analysis. However, the extent of method validation often depends on the intended application of a bioanalytical assay. Bioanalytical laboratories have expertise in PK assay validation and their application in clinical analysis. Besides, they perform PK assay validation according to current FDA and ICH guidelines. This article discusses the role of PK assay validation in the success of drug development and regulatory compliance.
PK assay validation for accelerating drug development
Validated pharmacokinetic assay ensures precise, accurate, and reliable results. Besides, it confirms that the assay is fit for its intended purpose. Therefore, researchers use patient samples, spiked serum samples, and quality control samples to assess the pharmacokinetic properties of a drug product. These evaluations include the calibration curve, sensitivity and quantification limit, accuracy and precision, dilution linearity and specificity, and selectivity. Let us explore each of these parameters and their role in successful regulatory compliance for PK assay.
Investigators use calibrated standards to prepare a calibration curve over different concentration ranges. A calibration curve is critical for describing the expected drug concentrations in study samples. The calibration standards are developed in the same biological material as the study samples.
The assay quantification range is a range of analytes where the analyte of interest can be determined with acceptable levels of precision and bias. It is described by the upper and lower limit of quantification.
QC samples determine the precision and accuracy of a PK assay. Accuracy is the relative closeness of the value to a true known value. It is calculated as a percent of recovery. On the other hand, precision is the closeness of data points in a series of measurements. It is determined as a coefficient of variation.
Reproducibility is the ability of an assay to deliver accurate results at different laboratories. This characteristic is particularly beneficial for method standardization or if a particular PK assay is used in different laboratories.
Highly specific assays distinguish between the target component and other similar structures present in the sample. These similar components may potentially cross-react with the target analyte. Samples are used to study assay specificity.
The selectivity of PK assay is its ability to identify the analyte in the presence of other sample components such as serum, proteins, and proteases. Scientists evaluate assay selectivity by spiking known drug concentrations into a blank matrix.
Generally, PK drug concentrations often span over a concentration range as they include through and peak levels in clinical testing. Hence, samples are often diluted before analysis. Dilution linearity shows that the PK assay can provide a precise and accurate analysis of these diluted samples.
