Receptor-mediated removal of lipoproteins by the liver is predominantly mediated by apolipoproteinE (apoE). Recent data show that a novel dual domain peptide (hE-18A) containing the 10-residue receptor-binding domain of human apoE, and a model class A amphipathic helix (18A), can associate with low density and very low density lipoproteins (LDL and VLDL) and enhance their uptake and degradation by HepG2 cells in vitro, and further, causes a dramatic reduction in plasma cholesterol levels in apoE-null mice. The in vivo cholesterol lowering effect, however, is short-lived because of rapid clearance of the peptide from the circulation. These results indicate that a therapeutic benefit may be achieved by sustained-delivery of this novel peptide as an alternate form of treatment for hypercholesterolemia and hypertriglyceridemia. In this report we describe the encapsulation of this peptide in a multivesicular liposome (MVL) depot-delivery system (DepoFoam™). An in vitro plasma release assay showed sustained release of the peptide from the DepoFoam particles and its subsequent association with LDL and VLDL. Furthermore, a single subcutaneous dose of the DepohE-18A formulation in apoE-null mice, yielded a mean, cumulative 18% decrease in serum cholesterol levels after 6 days, and the cholesterol levels remained low at 8 days. Whereas, an equivalent dose of free peptide showed maximal cholesterol decrease by 4 h, followed by a rapid decline in efficacy by 24-48 h. Fractionation of the different lipoprotein fractions from serum showed that the majority of the serum cholesterol decrease was associated with the VLDL fraction, followed by LDL. These results indicate that the apoE peptidomimetic encapsulated in DepoFoam has potential as an alternative therapeutic treatment of hyperlipidemia. © 2002 Elsevier Science B.V. All rights reserved.