Airway epithelial cell differentiation in Air–Liquid Interface (ALI) condition closely mimics physiological environment of the human airway system, promoting enhanced oxygen availability and cellular differentiation. These conditions are valuable for toxicity screening, drug transport studies, and exploring molecular pathways. Human Challenge Studies are pivotal in understanding interactions between viruses and the human body, leading to discoveries of immune mechanism and providing key outcomes about promising investigational medicinal products (mechanism of action, most appropriate dose and dosage regimen), which can then be applied to designing Phase IIb and Phase III studies.
