Pharmacokinetic testing assesses drug absorption, distribution, metabolism, and excretion profiles. It employs bioanalytical and biochemical assays to evaluate drug movement through the body. Hence, pharmacokinetic services and PK CROs are crucial for determining the efficacy and safety of drug compounds. During pre-clinical assessments, pharmacokinetic testing includes evaluating ADME properties in animal models. On the other hand, PK analysis in clinical trials involves ADME assessment in human subjects.
Pharmacokinetic clinical trials are a core component of clinical testing. It helps identify drug efficacy and safety and enables scientists to tailor the correct dosage for the patient population. Irrespective of pre-clinical or PK clinical trials, pharmacokinetic testing requires robust bioanalytical methods to generate reliable, accurate, and reproducible data. The current article highlights bioanalytical strategies for pre-clinical and PK samples in clinical trials.
Bioanalytical strategies for pharmacokinetic testing
Compound detection and sample preparation are the two primary elements of a bioanalytical method. Liquid-liquid extraction, solid-phase extraction, and plasma protein precipitation are the most routinely employed sample preparation methods for pharmacokinetic studies. Protein precipitation has a fast and simple clean-up process and hence, is used to extract compounds from biological matrices. However, solid-phase extraction is employed for a more selective removal of compounds from matrix interferences. Solid-phase extraction has higher recovery and is integrated easily into automated systems.
Turbulent flow chromatography is another robust technique for on-line extraction. This approach reduces sample preparation time and improves method sensitivity, two elements that are crucial in drug discovery studies. Today, LC-MS systems are used in quantitative bioanalysis due to their selectivity and sensitivity, while triple quadrupole MS systems are used to analyze PK samples in clinical trials. However, newer generations of high-resolution MS systems offer efficient alternatives for quantitating compounds in biological samples. Besides, LC-MS systems have also emerged as a complementary tool for traditional methods such as ligand binding assays for bioanalysis of macromolecules.
Must Read: Regulatory Considerations in PK ADA Analysis for Drug Development
Today, pharmaceutical development requires stringent regulations in terms of sensitivity, reliability, sample throughput, and speed of analysis. This increased demand has raised the challenges to develop robust bioanalytical methods for pharmacokinetic testing. These requirements can influence the sample preparation approaches and instruments. The primary step of bioanalytical method development is to identify a highly sensitive method to detect and estimate drug compounds present in low concentrations and determine the PK properties of the drug compound of interest. This step is very challenging, particularly for studies including microdosing PK assessments.
Often, the sample is preconcentrated to increase assay sensitivity even when this approach increases the target analyte concentration and sample matrix interference, both posing a significant issue for bioanalysis using LC-MS systems. Sample matrix interference may influence target analyte ionization, resulting in ion enhancement or suppression in LC-MS response, dramatically compromising bioanalysis. Hence, selecting a highly selective sample preparation approach is crucial for developing analytical strategies for PK sample analysis. Besides, scientists increase assay throughput in pharmacokinetic testing by adopting strategies such as cassette analysis and cassette dosing to minimize the total number of study samples in bioanalysis. In cassette dosing, scientists dose the same animals with multiple compounds. This approach reduces the test animals and provides a comprehensive pharmacokinetic profile of each drug compound in individual test animals.