Pharmacokinetics and Safety of Cilofexor and Firsocostat in Healthy Japanese and Non-Japanese Participants

Cilofexor, an oral farnesoid X receptor agonist, and firsocostat, an oral, liver-targeted inhibitor of acetyl-coenzyme A carboxylase, are being investigated in combination with semaglutide for the treatment of metabolic dysfunction-associated steatohepatitis (previously known as nonalcoholic steatohepatitis; NCT04971785). The pharmacokinetics and safety profiles of cilofexor (100 mg) and firsocostat (20 mg) were separately investigated in two phase 1 studies, each of which included healthy Japanese participants (n = 20 in the cilofexor study and n = 21 in the firsocostat study) and non-Japanese participants (n = 20 in the cilofexor study and n = 21 in the firsocostat study). Intensive pharmacokinetic sampling was performed over 96 h following a single-dose administration of the study drug. Safety was monitored throughout the study. In total, 39 participants completed each study. The plasma exposures of cilofexor and firsocostat (area under the concentration–time curve [AUC] calculated from time 0 to infinity [AUC_inf]) in Japanese participants were 1.24-fold and 1.98-fold, respectively, of those in non-Japanese participants. Both study drugs were well tolerated with no clear differences in adverse events or laboratory abnormalities between Japanese and non-Japanese participants. The approximate 2-fold exposure difference of firsocostat between Japanese and non-Japanese participants at the 20 mg dose does not warrant dose reduction given the previously established safety and tolerability of once-daily doses of firsocostat up to 200 mg.