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Implications of the iBCS on Molecule Design and Particle Engineering of Medicines for Inhalation

Weers JG.

Respiratory Drug Delivery 2026. Volume 1, 2026: 1-0.

Abstract:

The implications of the inhalation Biopharmaceutics Classification System (iBCS) on molecule and particle design is discussed. The importance of maximizing targeting to the lungs by reducing dissolution or permeability is highlighted. For bottom-up manufacturing methods like spray drying, the constraints of the iBCS highlight the need for designing processing methods that maintain the crystallinity of the API in the engineered powder. We discuss how advances in molecule design by medicinal chemists have created molecules with very different physicochemical properties than those approved for inhalation 25 years ago. Additional challenges associated with the design of formulations for pulmonary arterial hypertension (PAH), where the short distance from receptors in the pulmonary arteries to the systemic circulation necessitates a strategy to slow absorption (e.g., high affinity and prolonged binding to the receptor, increased binding to tissue) are also addressed. Sustaining levels of drug in the airways alone may be insufficient to achieve targeting. This necessitates the advancement of novel design strategies to achieve suitable formulations for inhalation (e.g., strategies to improve the solubility of the drug or to deliver amorphous solids).