Mohammad Anwar Hossain, Abigail K. Mayo, Anirban Ghoshal, Sharon A. Taft-Benz, Elizabeth J. Anderson, Noah L. Morales, Katia D. Pressey, Ava M. Vargason, Kim L. R. Brouwer, Nathaniel J. Moorman, Mark T. Heise, Timothy M. Willson
bioRxiv 2025.01.13.632788;
doi: https://doi.org/10.1101/2025.01.13.632788
RA-0002034 (1) is a potent covalent inhibitor targeting the alphavirus 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 CHIKV viral loads in multiple tissues. Initial estimations of human hepatic clearance and half-life extrapolated from animal data indicate that b.i.d. dosing of 1 will be possible to maintain concentrations sufficient for antiviral activity in humans. These cross-species pharmacokinetic and metabolism studies support the continued evaluation of 1 as a promising anti-alphaviral therapeutic.
