RBD5044 - a novel anti-ApoC3 GalNAc-siRNA drug resulted in sustained and profound reduction of triglycerides in mice and rhesus monkeys

Abstract

Introduction: Hypertriglyceridemia leads to endothelial dysfunction and contributes to the onset and progression of atherosclerosis as well as an increased risk of acute pancreatitis. Inhibition of Apolipoprotein-CIII (APOC3) via the RNA interference mechanism is supposed to reduce plasma Triglycerides (TG) levels with durable and high efficacy. RBD5044, which targets APOC3 mRNA in the liver, is a chemically-modified double-stranded small interfering RNA (siRNA) conjugated with N-acetylgalactosamine (Ribo-GalSTAR). Purpose: To investigate the preclinical efficacy and safety profile of RBD5044. Methods: Rhesus monkeys with spontaneously developed hypertriglyceridemia were given a single subcutaneous (sc) injection of RBD5044. Humanized APOC3 transgenic mice were treated with a single dose or repeated doses (once every two weeks for three doses, Q2W×3) of RBD5044. Plasma was collected to quantify APOC3 and lipid biomarkers to evaluate preclinical efficacy of RBD5044. SD rats and cynomolgus monkeys were used to evaluate the preclinical toxicology for subcutaneously injected RBD5044, including single-dose toxicity studies and 4-week repeat-dose pivotal toxicology studies. Results: In the rhesus monkeys with spontaneous hypertriglyceridemia, the maximum level of inhibition reached 61.2 % in APOC3 and resulted in a TG reduction by 53.3%. The levels of both APOC3 and TG were recovered to baseline till Day 85 after a single dose of 3 mg/kg RBD5044. In humanized APOC3 transgenic mice, RBD5044 achieved an average maximum inhibition level of over 90% for APOC3 and around 90% for TG after both single and repeated doses. The APOC3 and TG levels were recovered on Day 63 after a single dose of 3 mg/kg. On Day 63 after the last repeated dose at 3 mg/kg, the inhibition level remained at 41.6% for APOC3 and 49.4% for TG, hence did not recover to baseline within the study period. RBD5044 also showed reductions in total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) levels and elevations in high-density lipoprotein cholesterol (HDL-C) levels. Toxicology studies showed there is a sufficient therapeutic margin that supports the clinical development of RBD5044 with NOAEL of 40 mg/kg in rats and 300 mg/kg in monkeys. Conclusions: RBD5044 shows high efficacy, long duration and a good safety profile in preclinical studies. The Phase I trial of RBD5044 injection in healthy volunteers has been initiated in Australia.Figure 1Figure 2