Abstract

Pulmonary aerosolized delivery of drugs incorporated into nanocarriers (nanodrugs) by inhalation is a promising route for the prolonged treatment of lung diseases such as pulmonary hypertension or lung rejection after transplantation. Due to the lack of validated in vitro testing systems, the PK and efficacy of nanodrugs during the preclinical phase of drug testing has to be measured in animal models. This work investigates the particokinetics of two nanodrugs, Ptx-NP and L-CsA, which incorporate the active drug Paclitaxel (Ptx) and Cyclosporine A (CsA) into polymeric or liposomal nanocarriers, respectively. The goal of the study was to evaluate the potential of aerosolized drug delivery combined with physiological in vitro cell culture models of the lung to predict the clinical outcome with a focus on PK. The VITROCELL® Cloud 6 system was used to deliver the nanodrugs in aerosolized form to in vitro models of the healthy and diseased human alveolar air-blood barrier cultured at air-liquid interface (ALI) conditions, and to analyze the transbarrier transport of the incorporated drugs. ALI conditions showed a direct cell-nanodrug interaction, which allowed clarifying cellular uptake mechanisms (caveolae-mediated endocytosis and passive diffusion) and mirroring real cellular transport rates. In a direct comparison between the healthy and diseased models, no significant differences in the transbarrier transport rates were found, which highlight the prolonged tissue-association of drugs incorporated in nanocarriers. The obtained particokinetics were further combined with physiological-based PK (PBPK) modeling to predict the PK profile of CsA and Ptx (e.g. maximum drug concentration cmax in the blood; time until cmax is reached (tmax)) after inhalation. This confirmed that cmax levels after inhalation were achieved fast (< 0.25 h). Moreover, the modeling revealed that cmax levels after inhalation are typically low, which highlights the advantage of targeting lung diseases by inhalation therapy as this avoids high drug levels in the blood that could lead to systemic toxicities. Besides the PK, the efficacy of Ptx-NP was investigated. The analysis of Ptx doses in different compartments of the in vitro model demonstrated a cell-association of 30% of the initial dose 24 h after the aerosolized delivery of Ptx-NP. Accordingly, the potential of prolonged drug interaction with the diseased tissue in vitro could be highlighted. Moreover, a dose of 0.7 μg Ptx/cm² increased FoxO1 transcription – a hallmark of pulmonary hypertension - by a factor of 3 as compared to untreated control. Consequently, the aerosolized drug delivery to ALI cell culture models of the alveolar tissue barrier combined with PBPK modeling can support the development of drug formulations with a beneficial PK profile in the clinical settings. Moreover, these types of in vitro models are well suited to study cellular uptake and transport mechanisms.