Engineering Lipid Spherulites for the Sustained Release of Highly Dosed Small Hydrophilic Compounds.

Currently, there is a lack of parenteral sustained release formulations for the delivery of highly-dosed small hydrophilic drugs. Hence, herein, we engineered parenteral lipid spherulites capable of entrapping large amounts of such compounds and spontaneously releasing them in a sustained fashion. A library of spherulites was prepared with a simple green process, using phosphatidylcholine (PC) and/or phosphatidylethanolamine (PE), nonionic surfactants and water. The vesicle formulations exhibiting appropriate size distribution and morphology were selected and loaded with 4,6-di-O-(methoxy-diethyleneglycol)-myo-inositol-1,2,3,5-tetrakis(phosphate), ((OEG 2 ) 2 -IP4), an inositol phosphate derivative currently under clinical evaluation for the treatment of aortic valve stenosis. (OEG 2 ) 2 -IP4 was chosen as a model active pharmaceutical ingredient (API). The loading efficiency of spherulites was up to 12.5-fold higher than that of liposomes produced with the same materials. While the PC-containing vesicles showed high stability, the PE spherulites gradually lost their multilayer organization upon dilution, triggering the API release over time. In vitro experiments and pharmacokinetic studies in rats demonstrated the ability of PE spherulites to increase the systemic exposure of (OEG 2 ) 2 -IP4 up to 3.1-fold after subcutaneous injection, and to completely release their payload within 3-4 days. In conclusion, PE spherulites represent a promising lipid platform for the extravascular parenteral administration of highly-dosed small hydrophilic drugs. This article is protected by copyright. All rights reserved.