Rapid assessment of metabolism and disposition of conjugated oligonucleotide Vutrisiran in rats using a sensitive LC-HRMS platform

Vutrisiran is a GalNAc-conjugated small interfering RNA (siRNA) therapeutic approved for targeted hepatic delivery and long-acting gene silencing; however, detailed in vitro and in vivo metabolism data have not been published. In this study, a sensitive LC–HRMS platform was established to systematically evaluate the metabolism and disposition of Vutrisiran in rats following administration of a low, pharmacologically relevant dose (3 mg/kg). Vutrisiran exhibited high systemic metabolic stability, with intact parent drug as the predominant species in plasma and urine. Tissue metabolite profiling revealed distinct organ-specific pathways, including hepatic GalNAc cleavage followed by slow 3′-exonuclease–mediated degradation, and a low abundant but unique kidney-specific 5′-truncation of the sense strand (SS 5′ n-4). Renal excretion was the primary route for elimination of intact drug, whereas biliary excretion was responsible for clearance of extensively catabolized fragments. The overall excretion pattern was consistent with that reported for other GalNAc-conjugated oligonucleotides. These rat metabolic profiling data provide insight into the disposition of Vutrisiran in humans and represent the first reported in vivo disposition characterization of Vutrisiran. The LC–HRMS platform developed in this study enabled highly sensitive metabolite profiling and identification. A semi-quantitative approach based on MS peak area integration was validated by demonstrating close numerical agreement with UV detection. This platform supports metabolite profiling in plasma and target tissues for PK/PD studies and rapid disposition characterization in animals and may serve as an alternative or pilot approach to inform the design and necessity of human radiolabeled mass-balance studies for oligonucleotide therapeutics.