Antisense Oligonucleotide Lowers Plasma Levels of Apolipoprotein (a) and Lipoprotein (a) in Transgenic Mice

Objectives This study sought to assess whether an antisense oligonucleotide (ASO) directed to apolipoprotein (a) [apo(a)] reduces apo(a) and lipoprotein (a) [Lp(a)] levels in transgenic mouse models. Background Elevated Lp(a) is a causal, independent, genetic risk factor for cardiovascular disease and myocardial infarction. Effective therapies to specifically lower plasma Lp(a) levels are lacking. Methods Three transgenic mouse models were utilized: 8K-apo(a) mice expressing 8 kringle IV (KIV) repeats with a single copy of KIV-2; 8K-Lp(a) mice expressing both the 8K apo(a) plus human apolipoprotein B-100; and 12K-apo(a) mice expressing a 12K apo(a) with 3 KIV-2 repeats. The mice were treated intraperitoneally with saline, a control ASO, or ASO 144367 directed to KIV-2 for 4 to 6 weeks. Apo(a), Lp(a), and oxidized phospholipids present on human apoB (OxPL/h-apoB) or apo(a) [OxPL/apo(a)] were measured at baseline and on and off therapy. Results ASO 144367 significantly reduced Lp(a) by 24.8% in 8K-Lp(a) mice, and reduced apo(a) levels by 19.2% in 8K-Lp(a) mice, 30.0% in 8K-apo(a) mice, and 86% in 12K-apo(a) mice; ASO 144367 also significantly reduced OxPL/apoB 22.4% in 8K-Lp(a) mice, and OxPL/apo(a) levels by 19.9% in 8K-Lp(a) mice, 22.1% in 8K-apo(a) mice, and 92.5% in 12K-apo(a) mice (p < 0.004, or less, for all). No significant changes occurred in Lp(a), apo(a), OxPL/apoB, or OxPL/apo(a) levels with control ASO or saline. Conclusions This study documents the first specific therapy, to our knowledge, for lowering apo(a)/Lp(a) levels and their associated OxPL. A more potent effect was documented in mice expressing apo(a) with multiple KIV-2 repeats. Targeting liver expression of apo(a) with ASOs directed to KIV-2 repeats may provide an effective approach to lower elevated Lp(a) levels in humans. (J Am Coll Cardiol 2011;57:1611-21) (C) 2011 by the American College of Cardiology Foundation