Interactions of pluronic block copolymers on P‐gp efflux activity: Experience with HIV‐1 protease inhibitors

The objective was to examine the influence of Pluronic block‐copolymers on the interaction between the drug efflux transporter, P‐glycoprotein and HIV‐1 protease inhibitors (PIs). The ATPase assay determined the effect of various Pluronics on PI‐stimulated P‐gp ATPase activity. Cellular accumulation studies were conducted using MDCKII and LLC‐PK1 cells transfected with human MDR1 to assess Pluronic modulation of PI efflux. Pluronic P85 inhibited both basal and nelfinavir‐stimulated P‐gp ATPase activity, while Pluronic F127 had no effect. In cell accumulation studies, Pluronic P85 restored the accumulation of nelfinavir in MDCKII‐MDR1 cells while Pluronic F127 and F88 had no effect. Pluronic P85 increased saquinavir accumulation in wild‐type and MDR1‐transfected cells in both the MDCKII and LLC‐PK1 cell models, suggesting inhibition of multiple transporters, including MRPs. In conclusion, this study provides evidence that a block‐copolymer, Pluronic P85, effectively inhibits the interaction of P‐gp with nelfinavir and saquinavir. These data indicate that effective inhibition of HIV‐1 PI efflux by Pluronic P85 may influence the distribution of antiretroviral agents to sites protected by efflux mechanisms, such as the blood-brain barrier, and possibly increase the brain exposure of these drugs resulting in suppression of viral replication and reduction in the incidence of drug resistant mutants. © 2008 Wiley‐Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:5421-5433, 2008