Efficacy of a New Pulmonary Cyclosporine A Powder Formulation for Prevention of Transplant Rejection in Rats

Background The aim of this pilot study was to determine the pharmacokinetics of cyclosporine A powder for inhalation (iCsA) and its rejection prevention efficacy in an experimental lung transplantation model in rats. Methods Single-dose pharmacokinetics (10 mg/kg) of pulmonary and orally administered cyclosporine A was determined in whole blood and in lung and kidney tissue. The efficacy of iCsA (2.5 and 5 mg/kg) in inhibiting rejection was determined in an orthotopic left-lung transplantation rat model and compared with orally administered CsA (5 and 10 mg/kg). The ventilation score of lung allografts was assessed with roentgenograms. At Day 10 post-operatively, the rats were terminated and lungs were prepared for histologic analysis. Results In the pharmacokinetics study, AUC0–48 values in blood for iCsA and oral CsA were similar (47,790 ± 1,739 and 46,987 ± 2,439 ng h ml−1 , respectively). In contrast, iCsA levels in lung tissue were much higher than oral CsA levels (AUC: 9,152,977 ± 698,920 vs 84,149 ± 8,134 ng h g−1 , respectively), showing the effectiveness of the pulmonary administration. In the rejection study, non-treated animals showed complete rejection after 8 days according to roentgenography. Treatment with 5 mg/kg iCsA reduced rejection on Day 10, whereas the 2.5-mg/kg dose did not inhibit rejection. Oral CsA at 10 mg/kg reduced rejection, whereas the 5-mg/kg dose showed hardly any effect on rejection. Conclusions We found that iCsA is an effective immunosuppressive formulation, and may become a valuable asset for clinical use in combination with systemic immunosuppression.