Plozasiran

Familial chylomicronemia syndrome (FCS) is a condition characterized by dangerously elevated triglyceride-rich lipoproteins (TRLs) and an increased risk of acute pancreatitis and cardiovascular disease. The pathophysiology of lipid disorders such as FCS is often driven or exacerbated by Apolipoprotein C-III (APOC3), a glycoprotein primarily produced in the liver. APOC3 acts as a key regulator of lipid metabolism by inhibiting lipoprotein lipase (LPL) and slowing the hepatic clearance of TRLs, thereby elevating circulating triglyceride levels.

Plozasiran is a double-stranded small interfering RNA (siRNA) conjugated with N-acetylgalactosamine (GalNAc). The GalNAc conjugation facilitates targeted uptake by hepatocytes, where the drug leverages the endogenous RNA interference (RNAi) pathway. Once intracellular, plozasiran incorporates into the RNA-induced silencing complex (RISC) and selectively targets the messenger RNA (mRNA) coding for APOC3. This interaction leads to the catalytic degradation of the APOC3 mRNA, effectively preventing the translation and production of the APOC3 protein. The pharmacological reduction of APOC3 protein levels removes the inhibitory brake on lipoprotein lipase and enhances LPL-independent hepatic clearance mechanisms. This restoration of normal lipid metabolism results in deep and sustained reductions in fasting triglycerides and triglyceride-rich lipoproteins, including VLDL and chylomicrons. This mechanism is supported by genetic evidence showing that naturally occurring loss-of-function variants in the APOC3 gene are associated with reduced triglycerides and a lowered risk of ischemic cardiovascular disease.