Prediction of V(ss) from in vitro tissue-binding studies

Area of Science:

• Pharmacokinetics
• Drug Distribution
• Physicochemical Properties

Background:

• Accurate prediction of volume of distribution at steady-state (V(ss)) is crucial for drug development.
• Current empirical and mechanistic methods often fail to predict V(ss) accurately across diverse drug classes.

Purpose of the Study:

• To evaluate the utility of in vitro nonspecific tissue-binding measurements for predicting V(ss) in rats.
• To compare the accuracy of this approach with existing mechanistic methods.

Main Methods:

• Utilized in vitro nonspecific tissue-binding measurements.
• Incorporated calculated effects of the pH partition hypothesis.
• Studied a range of literature and proprietary compounds in rats.

Main Results:

• In vitro tissue binding combined with pH partition hypothesis predicted V(ss) more accurately than other mechanistic methods for many drugs.
• This approach complements existing V(ss) prediction strategies.
• Some drug V(ss) values were not accurately predicted, suggesting involvement of specific distribution mechanisms.

Conclusions:

• In vitro nonspecific tissue binding and pH partition hypothesis show promise for improving V(ss) prediction.
• Further investigation into specific drug distribution mechanisms (e.g., lysosomal uptake, active transport) is needed for challenging cases.
• This approach can enhance mechanistic V(ss) prediction models.