Abstract
This is the fourth paper in a series describing an inhalation biopharmaceutics classification system (iBCS), an initiative supported by the Product Quality Research Institute. The paper examines the application of the inhalation Biopharmaceutics Classification System (iBCS) through the drug discovery, development, and postapproval phases for orally inhaled drug products (OIDP) and for the development of generic OIDPs. We consider the implication of the iBCS class in terms of product performance and identify the practical gaps that must be filled to enable the classification system to be adopted into day-to-day practice. Consideration is given to the critical experimental data required and the methods for their generation with a focus on: (i) dose to the lungs, (ii) drug solubility in relevant media and methods to model the dissolution of respirable formulations, and (iii) pulmonary drug permeability. As described in three prior publications, the iBCS was developed to classify inhaled drugs based on physicochemical and biorelevant product attributes in a manner that will allow formulators and discovery chemists to identify and mitigate product development risks. It was not established to enable in vitro determination of bioequivalence between orally inhaled drug products. However, once analytical methods are in place to correctly classify inhaled drugs, the system has the potential to provide an understanding of the development risks associated with both establishing bioequivalence between two drug products and enabling postapproval changes based on product iBCS class.