Pharmacokinetics (PK) defines the absorption, distribution, metabolism, and excretion of a drug by an organism. PK assessment requires the quantitative evaluation of an analyte within a biological matrix. Development and validation of such analytical methods are critical to the successful outcome of a clinical study. In addition, validated methods ensure that the data obtained is reliable. Reliable data is obtained from methods that quantify the analyte of interest, with acceptable variability over a suitable range from samples that are obtained in a controlled/set manner.

Synexa develops and validates bioanalytical methods for PK analysis according to the guidelines laid out by the following regulatory bodies:

European Medicines Agency (EMA):

Guideline on bioanalytical method validation (2011)

Food and Drug Administration (FDA):

Bioanalytical Method Validation Guidance for Industry (2018)

Method development:

The purpose of method development is to define and test the design of a method under a variety of conditions, before subjecting it to validation. Whilst no specific regulatory guidance or acceptance criteria is assigned to method development, basic assay parameters need to be optimized prior to method validation. Such parameters include but are not limited to the assay platform, suitable reference standard, quality controls, matrix type, minimum required dilution, assay quantification range, sample collection processes, storage conditions, incubation temperatures and duration, capture and detection molecule pairs and concentrations and number of wash cycles.


Bioanalytical method validation illustrates that an optimised method is suitable for the intended analysis of study samples. Synexa performs method validation according to the FDA and EMA guidelines mentioned above. The extent of method validation (custom or full validation) is agreed upon with the sponsor and is outlined in a validation phase plan to suit the needs of the study (e.g. exploratory or primary endpoint). Bioanalytical method validation includes the following key assessments.


Accuracy and Precision (A&P):

Accuracy and Precision (A&P):

Accuracy and precision (A&P) defines the closeness of measured values to each other (precision) and the closeness to an expected nominal (accuracy). The A&P of a method needs to be illustrated across the quantification range. A&P assessments aim to include quality control (QC) levels at low, mid and high levels, as well as at the lower (LLOQ) and upper limit of quantification (ULOQ). A&P is determined by cumulative data from at least six independent experiments conducted over several days by more than one analyst.


Dilution linearity:

Dilution linearity:

Dilution linearity assessments will confirm that if a sample’s concentration exceeds the upper quantification limit (ULOQ), that it can it be diluted using blank matrix to bring the concentration level of the sample within the quantification range of the method without losing accuracy. In addition, dilution linearity assists to detect a possible “hook effect” where concentrated samples suppress the signal of a sample.




Parallelism is assessed to detect possible matrix effects or differing affinities for metabolites by comparing the calibration standard curve to serially diluted samples.


Spike and recovery:

Spike and recovery:

The spike and recovery assessment quantifies the degree of matrix interference which can be tolerated for analyte recovery to be consistent, precise, and reproducible.




Stability assessment verifies the conditions that samples can be subjected to, wherein analyte concentrations remain stable. Such assessments are used to confirm the duration and temperature that samples can be stored and thawed at.




This is a measure of the ability of the assay to perform reliably during routine performance of the method from day to day. Analysis investigates the sensitivity of the assay to small and deliberate alterations in assay conditions including incubation times and temperatures.


Following validation and acceptance of a method validation report, clinical sample analysis (production phase) can commence. All analytical assessments are conducted as guided by the FDA and EMA guidelines and as per validated method.


Synexa Life Sciences has over 17 years of experience in developing and validating experiments used in the support of clinical drug trials. For PK analysis, these experiments include but are not limited to the following technologies:

  • ECL
  • ELISA (Absorbance, Fluorescence and Luminescence)
  • AlphaLISA
  • Flow Cytometry