Abstract 10357: ARO-APOC3, an Investigational RNAi Therapeutic, Shows Similar Efficacy and Safety in Genetically Confirmed FCS and Non-FCS Participants with Severe Hypertriglyceridemia

Background: Familial chylomicronemia syndrome (FCS) is an ultrarare condition caused by biallelic pathogenic DNA variants in lipolysis-associated genes, resulting in severe hypertriglyceridemia (HTG) and associated with high risk of acute pancreatitis with few therapeutic options. In a 16-week Phase 1 study (NCT03783377), subcutaneously administered ARO-APOC3 reduced serum apolipoprotein C3 (APOC3) and TG in healthy volunteers and participants (pts) with HTG and was well tolerated. Purpose: To report on the safety/pharmacodynamic (PD) effects of ARO-APOC3 in both FCS pts with biallelic pathogenic variants and pts with severely elevated TG at screening (>880 mg/dL) but without biallelic pathogenic variants (chylomicronemia (MCM)). Methods: Four genetically confirmed FCS pts received 50 mg ARO-APOC3 and 26 MCM pts received 10, 25, 50, or 100 mg ARO-APOC3 on Days 1 and 29. Since similar PD responses were observed among MCM pts, results were pooled across dose levels. Safety and PD responses were examined. Maximal mean/median changes from baseline for APOC3, TG, non-HDL-C, and HDL-C were reported. Results: Baseline/demographics were comparable between groups, except for mean BMI (22.1 [FCS] and 30.5 [MCM] kg/m 2 ), and mean baseline HDL-C , which were lower in FCS pts (Table 1) (p<0.0001 for both). Mean APOC3 was reduced by 98% and 96% in FCS and MCM pts, respectively. Both groups also showed similar maximum median reductions in TG of 91% and 90%, respectively. Similar to the full study, non-HDL-C was reduced and HDL-C increased with treatment in both groups (Table 1). AEs were similar between groups, suggesting a comparable safety profile. Conclusions: In patients with severe HTG, ARO-APOC3 was safe, and consistently decreased APOC3, TG, and non-HDL-C, and increased HDL-C, regardless of underlying genetic cause of HTG, and may represent a promising RNAi therapeutic for the treatment of severe HTG.