Pulmonary delivery of forsythin-phospholipid complexes improves the lung anti-inflammatory efficacy in mice by enhancing dissolution and lung tissue affinity

Forsythin, currently in phase II clinical trials in China for the treatment of the common cold and influenza, faces challenges in achieving adequate lung drug exposure due to its limited dissolution and permeability, thereby restricting its therapeutic efficacy. The objective of this work was to formulate a forsythin-phospholipid complex (FPC) to enhance its dissolution properties and lung affinity with a particular view to improving pulmonary drug exposure and anti-inflammatory response. The results revealed that forsythin reacted with dipalmitoyl-phosphatidylcholine to form a stable, nanosized FPC suspension. This formulation significantly improved the in vitro drug's dissolution, cellular uptake, and lung affinity compared to its uncomplexed form. Intratracheal administration of FPC in a mouse model of acute lung injury induced by lipopolysaccharide (LPS) resulted in a substantial increase in drug exposure to lung tissues (39.6-fold) and immune cells in the epithelial lining fluid (198-fold) compared to intraperitoneal injection. In addition, FPC instillation exhibited superior local anti-inflammatory effects, leading to improved survival rates among mice with LPS-induced acute respiratory distress syndrome, outperforming both instilled forsythin and injected FPC. Overall, this work demonstrated the potential of phospholipid complexes as a viable option for developing inhalation products for drugs with limited solubility and permeability properties.