Activation of pregnane X receptor-organic anion transporting polypeptide 1a/b /P-glycoprotein/multidrug resistance protein 2 axis mediates the accelerated blood and liver clearance of PEGylated liposomes.

Previous studies revealed that pregnane X receptor (PXR) was involved in the "accelerated blood clearance (ABC)" phenomenon induced by repeated injections of PEGylated liposomes, and observed the quickly reduced hepatic accumulation of the second dose in rats at 12 hours after the last injection, compared with the increased hepatic accumulation characteristic of the ABC phenomenon. Among the downstream target genes of PXR, organic anion transporting polypeptide 1a/b (Oatp1a/b), P-glycoprotein (P-gp), and multidrug resistance protein 2 (Mrp2) are responsible for regulating the absorption, distribution, and efflux processes of drugs. This study aimed to investigate the molecular mechanisms behind the accelerated blood and liver clearance of the second dose of PEGylated liposomes from the perspective of PXR-regulated transporters. This study demonstrated that PXR activation promoted the blood clearance and liver clearance of the second dose of PEGylated liposomes in rats via the upregulation of Oatp1a4/1b2 and P-gp/Mrp2, respectively. The long-circulation characteristic and intrahepatic disposition fate of PEGylated liposomes could be reconstructed by inhibition of the PXR-Oatp1a/b/P-gp/Mrp2 axis. Additionally, we found that the repeated injections of PEGylated liposomes could cause significant transporter-mediated drug-drug interactions in combination administration regimens due to the activation of Oatp1a/b and P-gp/Mrp2. This study identifies the PXR-Oatp1a/b/P-gp/Mrp2 axis as a critical molecular regulator of systemic clearance of PEGylated liposomes and provides a therapeutic strategy to mitigate the ABC phenomenon through targeted inhibition of the PXR-Oatp1a/b/P-gp/Mrp2 axis, which is instructive for promoting the development and translation of PEGylated nanoformulations and optimizing their dosing regimens. SIGNIFICANCE STATEMENT: This study reveals that pregnane X receptor activation mediates the accelerated blood and liver clearance of the second dose of PEGylated liposomes in rats via upregulating the organic anion transporting polypeptide 1a4/1b2 and P-glycoprotein/multidrug resistance protein 2, and that PEGylated liposomes can induce transporter-mediated drug-drug interactions in combination administration regimens. These findings advance the understanding for the mechanisms underlying the in vivo disposition fate of repeated injections of PEGylated liposomes, providing guidance and new clues for inhibiting accelerated blood clearance phenomenon and optimizing the dosing regimens of PEGylated formulations.