Polymeric micelles for the solubilization and delivery of cyclosporine A: pharmacokinetics and biodistribution

The aim of this study was to assess the potential of polymeric micelles to modify the pharmacokinetics and tissue distribution of cyclosporine A (CsA). Drug-loaded methoxy poly(ethylene oxide)-b-poly(epsilon-caprolactone) (PEO-b-PCL) micellar solutions in isotonic medium were prepared and administered intravenously to healthy Sprague-Dawley rats. Blood and tissues were harvested and assayed for CsA, and resultant pharmacokinetic parameters and tissue distribution of CsA in its polymeric micellar formulation were compared to its commercially available intravenous formulation (Sandimmune). In the pharmacokinetic assessment, a 6.1 fold increase in the area under the blood concentration versus time curve (AUC) was observed for CsA when given as polymeric micellar formulation as compared to Sandimmune. The volume of distribution and clearance of CsA as PEO-b-PCL formulation were observed to be 10.0 and 7.6 fold lower, respectively, compared to the commercial formulation. No significant differences in t(1/2) or MRT could be detected. In the biodistribution study, analysis of tissue samples indicated that the mean AUC of CsA in polymeric micelles was lower in liver, spleen and kidney (1.5, 2.1 and 1.4-fold, respectively). Similar to the pharmacokinetic study in these rats, the polymeric micellar formulation gave rise to 5.7 and 4.9-fold increase in the AUC of CsA in blood and plasma, respectively. Our results show that PEO-b-PCL micelles can effectively solubilize CsA, at the same time confining CsA to the blood circulation and restricting its access to tissues such as kidney, perhaps limiting the onset of toxicity.