ABSTRACT: AIMS:Elevated apolipoprotein C-III (apoC-III) levels are associated with hypertriglyceridaemia and coronary heart disease. AKCEA-APOCIII-LRx is an N-acetyl galactosamine-conjugated antisense oligonucleotide targeted to the liver that selectively inhibits apoC-III protein synthesis. METHODS AND RESULTS:The safety, tolerability, and efficacy of AKCEA-APOCIII-LRx was assessed in a double-blind, placebo-controlled, dose-escalation Phase 1/2a study in healthy volunteers (ages 18-65) with triglyceride levels ?90 or ?200?mg/dL. Single-dose cohorts were treated with 10, 30, 60, 90, and 120?mg subcutaneously (sc) and multiple-dose cohorts were treated with 15 and 30?mg weekly sc for 6?weeks or 60?mg every 4?weeks sc for 3?months. In the single-dose cohorts treated with 10, 30, 60, 90, or 120?mg of AKCEA-APOCIII-LRx, median reductions of 0, -42%, -73%, -81%, and -92% in apoC-III, and -12%, -7%, -42%, -73%, and -77% in triglycerides were observed 14?days after dosing. In multiple-dose cohorts of 15 and 30?mg weekly and 60?mg every 4?weeks, median reductions of -66%, -84%, and -89% in apoC-III, and -59%, -73%, and -66% in triglycerides were observed 1?week after the last dose. Significant reductions in total cholesterol, apolipoprotein B, non-high-density lipoprotein cholesterol (HDL-C), very low-density lipoprotein cholesterol, and increases in HDL-C were also observed. AKCEA-APOCIII-LRx was well tolerated with one injection site reaction of mild erythema, and no flu-like reactions, platelet count reductions, liver, or renal safety signals. CONCLUSION:Treatment of hypertriglyceridaemic subjects with AKCEA-APOCIII-LRx results in a broad improvement in the atherogenic lipid profile with a favourable safety and tolerability profile. ClinicalTrials.gov Identifier: NCT02900027.