Interspecies comparison on the O-methylation metabolism of LJR003, a novel immunomodulator targeting acetyl-CoA acetyltransferase 1.

Catechol structures are essential for drug activity and can undergo meta- or para-methylation, which affects their pharmacological properties. The regioselectivity and species differences in O-methylation metabolism significantly influence drug efficacy and toxicity, requiring further study. LJR003, an immunomodulator with a catechol structure, targets acetyl-CoA acetyltransferase 1 (ACAT1), a potential target for cancer immunotherapy. This study investigated the activity, methylation regioselectivity, and species differences of LJR003 and its methylated metabolites. Pharmacokinetic studies were conducted in rats, mice, and dogs, and methylation regioselectivity was analyzed in liver, kidney, and erythrocytes from these species and humans after LJR003 incubation. Results showed that meta-methylated LJR003 had weaker ACAT1 inhibitory activity and higher systemic exposure than LJR003 in rats, mice, and dogs. Erythrocytes exhibited the lowest methylation activity in vitro, while liver catalytic efficiency in rats, mice, and dogs was at least twice that of the kidney. In humans, liver and kidney showed similar catalytic activity. LJR003 favored meta-methylation in mice, dogs, and humans in vitro, with consistent in vivo results in mice and dogs. Rats displayed a unique metabolic pattern, suggesting species-specific differences. In conclusion, LJR003 is predicted to undergo meta-methylation in humans, contributing to its pharmacological effects alongside the parent compound. These findings improve understanding of methylation metabolism and provide insights for developing catechol-based drugs, emphasizing the importance of species-specific metabolic pathways in drug development.