Intracellular Drug Delivery Process of Am80-Encapsulated Lipid Nanoparticles Aiming for Alveolar Regeneration

Chronic obstructive pulmonary disease (COPD) results in obstructive ventilatory impairment caused by emphysema, and current treatment is limited to symptomatic therapy or lung transplantation. Therefore, the development of new treatments to repair alveolar destruction is especially urgent. Our previous study revealed that 1.0 mg/kg of synthetic retinoid Am80 had a repair effect on collapsed alveoli in a mouse model of elastase-induced emphysema. From these results, however, the clinical dose calculated in accordance with FDA guidance is estimated to be 5.0 mg/60 kg, and it is desirable to further reduce the dose to allow the formulation of a powder inhaler for clinical application. To efficiently deliver Am80 to the retinoic acid receptor in the cell nucleus, which is the site of action, we focused on SS-cleavable proton-activated lipid-like material O-Phentyl-P4C2COATSOME^®SS-OP, hereinafter referred to as "SS-OP"). In this study, we investigated the cellular uptake and intracellular drug delivery process of Am80-encapsulated SS-OP nanoparticles to elucidate the mechanism of Am80 by nanoparticulation. Am80-encapsulated SS-OP nanoparticles were taken up into the cells via ApoE, and then Am80 was efficiently delivered into the nucleus via RARα. These results indicated the usefulness of SS-OP nanoparticles as drug delivery system carriers of Am80 for COPD treatment.