Development of a new drug (either a biological or a chemical entity) is a complicated process which goes on for long durations and costs a lot to the developer. Besides, there are various complex challenges involved throughout this drug discovery and development process. Right from the identification of the raw materials to the different experimental models to the final drug marketing, the process is too long and tedious.
Almost all the phases involved in drug discovery and development includes successful implementation of useful pharmacokinetic or pharmacodynamic studies. PK testing is considered to be a valuable approach for evaluating the pharmacological properties of a drug candidate under analysis. The rational study design involved here assumes a linear relationship between drug exposure and its therapeutic efficacy.
As such relations are generally complex in origin, robust pre-clinical trials have become the need of the hour. With its application, one can reduce animal model usage, cut-short the development time, help in the easy estimation of the therapeutic index, and assist the prediction index.
Pharmacokinetic and ADME characterization offers useful feedback for drug formulation development. PK assays yield essential information on critical parameters such as AUC, Cmax, and Tmax. Later, the study data obtained here is compared with the data generated in the previous studies and establish the predictive power of the pre-clinical trials.
Before the start of any PK analysis, it is always important to define its objectives correctly. This leads to the identification of the strengths and weaknesses associated with the Pk testing results. Further, the scientists should provide the correlation between in vitro and in vivo efficacy studies so that the PK parameters can be understood in animal test species.
To conclude on the pre-clinical and clinical studies, it is essential that the scientist understands and agrees on the protocol details related to the route of administration, duration of the study, and sampling frequency. It is here, where they can benefit from the existing Pk and efficacy data and design further experiments accordingly.
Ideally, the same animal is used to collect samples for both Pd and pk analysis. In case if the animal sample to be collected is limited, a satellite group of animals may be preferred. Here, all the parameters must be matched appropriately – gender, species, strains, dose administration, dose, dosing schedules, state of the disease, and sampling times.
Pk behaviours recorded in humans provides valuable data about both the drug exposure and plasma concentration-time profile. This prediction is fundamental and plays a vital role in the estimation of the human therapeutic dose and its expected therapeutic window.
This prediction of such pk study in humans is a complicated exercise and involves – generation of in vitro ADME characteristics; in vivo PK analysis results (at least in two to three species); and data integration into a suitable framework for allowing ease in the prediction of the PK profile in human subjects.
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