Evaluation of the Absorption, Metabolism, and Excretion of a Single Oral 1-mg Dose of Tropifexor in Healthy Male Subjects and the Concentration Dependence of Tropifexor Metabolism

A Study to Evaluate Relative Bioavailability, Food Effect, and Pharmacodynamics of Tropifexor, a Farnesoid X Receptor Agonist, in Healthy Participants

This open-label, randomized, 3-treatment, 3-period, 6-sequence, crossover study in healthy subjects compared the pharmacokinetic and pharmacodynamic properties of a lipid-based (soft gelatin capsule) prototype final market image (pFMI) formulation of tropifexor (90-µg) to its clinical service form (CSF) and assessed the food effect for the pFMI formulation. In the fasted state, drug exposure was higher for the pFMI. The geometric mean ratios for pFMI versus CSF of peak concentration and area under the concentration-time curve were 2.0 and 1.5, respectively. No food effect was apparent for the pFMI formulation, and the geometric mean ratios for pFMI fed versus pFMI fasted of peak concentration and area under concentration-time curve were 1.0 and 1.0 respectively. Despite having lower systemic exposure, the CSF formulation provided a higher pharmacological response for the gut biomarker fibroblast growth factor 19. Under fasted conditions, fibroblast growth factor 19 maximum change from baseline serum concentration after drug administration and area under the change from baseline serum concentration-time curve from time 0 to 24 hours were 36% for CSF and 12% for FMI. For a second biomarker, serum 7-alpha hydroxy-4-cholest-3-one, the pharmacological activity was comparable between CSF (fasted) and pFMI (both fasted and fed states). The pFMI offers advantages over the CSF in terms of insensitivity to food effect, lower intersubject variability, and overcoming solubility limitations.

Drug-Drug Interaction Studies to Evaluate the Effect of Inhibition of UGT1A1 and CYP3A4 and Induction of CYP3A4 on the Pharmacokinetics of Tropifexor in Healthy Subjects

Tropifexor, a farnesoid X receptor agonist, is currently under clinical development for the treatment of nonalcoholic steatohepatitis. Tropifexor undergoes glucuronidation by uridine 5'-diphosphoglucuronosyltransferase (UGT) 1A1 and oxidation by cytochrome P450 (CYP) 3A4, as reported in in vitro studies. Here, we report the results from 2 drug-drug interaction studies. Study 1 enrolled 20 healthy subjects to investigate the effect of the UGT1A1 inhibitor atazanavir (ATZ) on tropifexor pharmacokinetics (PK). Study 2 had 2 cohorts with 16 healthy subjects each to investigate the effect of the strong CYP3A4 inhibitor itraconazole and strong CYP3A4 inducer rifampin on the PK of tropifexor. Coadministration of ATZ reduced the maximum plasma concentration (C_max ) of tropifexor by 40%; however, it did not lead to increased exposure of tropifexor (both area under the plasma concentration-time curve [AUC] from time 0 to the last quantifiable concentration [AUC_last ] and AUC from time 0 to infinity [AUC_inf ] reduced by only 10%), suggesting minor relevance of the UGT1A1 pathway for clearance of tropifexor and no expected drug-drug interactions based on UGT1A1 inhibition. Inhibition of CYP3A4 by itraconazole increased the C_max of tropifexor by only 9% and exposure (both AUC_last and AUC_inf ) by 47%, suggesting a weak effect of strong CYP3A4 inhibitors on tropifexor PK. Inducing CYP3A4 with rifampin decreased C_max (55%) and AUC (AUC_last by 79% and AUC_inf by 77%). Coadministration of tropifexor with either ATZ, itraconazole, or rifampin was well tolerated.

Pharmacokinetics of Tropifexor, a Potent Farnesoid X Receptor Agonist, in Participants With Varying Degrees of Hepatic Impairment

Tropifexor, a non-bile acid farnesoid X receptor (FXR) agonist, has dose-proportional pharmacokinetics (PK) and no obvious major enterohepatic circulation. This open-label study investigated the effect of hepatic impairment (HI), as determined by Child-Pugh grade, on tropifexor's PK, safety, and tolerability following a 200-μg dose in the fasted state. Blood samples were collected through 168 hours after dosing for quantification and plasma protein-binding determination. Total tropifexor exposure was comparable across participants with HI vs those with normal hepatic function. Tropifexor was highly protein bound (>99%) in human plasma across participants of all groups. The average unbound fractions (percent free) were 0.14% in participants with normal hepatic function and mild HI, which increased to 0.17% and 0.24% in participants with moderate and severe HI, respectively. Similar unbound drug exposure was noted in participants with mild HI and normal hepatic function. Participants with moderate HI (N = 8) had a 1.6-fold increase in unbound exposure (area under the plasma concentration-time curve from time 0 to infinity [AUC_{inf, u} ]) and a 1.3-fold increase in maximal exposure (C_max,u ) vs those with normal hepatic function (geometric mean ratio: AUC_{inf, u} = 1.64 [90% CI, 1.25-2.16]; C_max,u = 1.30 [0.96-1.76]). Participants with severe HI (N = 8) had a 1.6-fold increase in AUC_{inf, u} (1.61 [1.04-2.49]) and comparable C_max,u (1.02 [0.60-1.72]) compared to participants with normal hepatic function. Tropifexor was well tolerated. The relative insensitivity of tropifexor to HI offers the potential to treat patients with severe liver disease without dose adjustment. This article is protected by copyright. All rights reserved.