Rate of Drug Coating Dissolution Determines In-Tissue Drug Retention and Durability of Biological Efficacy

Abstract

Two different drug-coated balloons (DCBs) possessing different coating formulations were compared for rate of coating dissolution in vitro, in addition to tissue drug concentration and histological responses of treated vascular tissue in vivo, to determine if the rate of drug bioavailability to vascular tissue can impact the degree and duration of the observed pharmacological response to locally delivered drug. In vitro dissolution comparison demonstrated that a urea/paclitaxel-based coating formulation (IN.PACT™ Admiral™) released drug from solid to soluble phase at a slower and constant rate, yielding approximately 7% solubilized drug in 24 h. In contrast, a coating formulated from polysorbate/sorbitol/paclitaxel (Lutonix™) released 51% of solid phase drug to soluble phase in 1 h of dissolution with the remainder solubilizing in 24 h. In vivo evaluation of tissue drug concentration of both products showed significantly different tissue pharmacokinetic profile, with a higher concentration of paclitaxel in tissue at 90 days with a urea-based formulation excipient. Histological comparison of smooth muscle cell loss in response to drug exposure revealed contrasting trends of smooth muscle cell loss from 28 to 90 days with significantly higher response to drug observed at 90 days with the urea-based formulation. Rapid dissolution of drug from the polysorbate/sorbitol coating formulation was associated with an early increase in local cellular response to drug which diminished over 90 days with clearance of local drug from tissue. Sustained long-term drug-in-tissue concentration associated with the urea-based formulation demonstrated sustained pharmacological activity at 90 days, suggesting that slow coating dissolution provides a sustainable long-term tissue response.