Species-Dependent Metabolism of a Covalent nsP2 Protease Inhibitor with In Vivo Antialphaviral Activity

RA-0002034 (1) is a potent covalent inhibitor
targeting
the nsP2 cysteine protease. The species-dependent pharmacokinetics
and metabolism of 1 were investigated to evaluate its
therapeutic potential. Pharmacokinetic profiling revealed rapid clearance
in mice, predominantly mediated by glutathione S-transferase
(GST)-catalyzed conjugation. This metabolic liability contrasted with
slower clearance observed in human hepatocytes and preclinical species,
such as rats, dogs, and monkeys. Cross-species studies confirmed the
dominance of GST-driven metabolism in mice, whereas oxidative pathways
were more pronounced in dogs. Despite rapid systemic clearance, 1 achieved antiviral efficacy in mice, reducing chikungunya
(CHIKV) viral loads in multiple tissues. These cross-species pharmacokinetic
and metabolism studies support the continued evaluation of 1 as a potential antialphaviral therapeutic to further define the
contribution of hepatic and non-hepatic GST metabolism to its clearance
in humans.