br Introduction Farnesoid X receptor

Introduction Farnesoid X receptor (FXR) is a bile AS1842856 regulated nuclear receptor highly expressed in the liver, intestine, kidney and adrenal glands in rodents.1, 2, 3, 4 FXR regulates transport proteins, the bile salt export pump (BSEP) and the organic solute transporter α (OSTα) that are involved in hepatocellular excretion. FXR and the cholesterol-sensing liver X receptor (LXR) form an intricate regulatory network with other members of the nuclear receptor super-family, constitute androstane receptor (CAR) and pregnane X receptor (PXR). Chenodeoxycholic acid (CDCA) as an endogenous ligand of FXR, transcriptionally represses the expression of cholesterol 7α-hydroxylase (CYP7A1), the rate-limiting enzyme during bile acid synthesis, by inducing small heterodimer partner (SHP) in liver. FXR controls cholesterol, lipid, and glucose metabolism.8, 9 A growing number of studies suggest that FXR represents an attractive pharmacological target. Non-steroidal FXR agonists have been obtained from independent research groups.11, 12, 13, 14 The structure of isoxazole GW4064 (1) is the basis of subsequent agonists; however, 1 is not clinically used. (Fig. 1) Tropifexor (2) is undergoing clinical trials for nonalcoholic steatohepatitis (NASH). In contrast, various types of FXR antagonists have been reported including GW4064-derivatives (3), trisubstituted-pyrazol carboxamide analogs (4), trisubstituted-pyrazolone derivatives (5), NDB (6), N-phenylbenzamide analogs (7), oxadiazole analogs (8), T3 (9) and T1 (10). Compound T3 (9) has a pharmacological profile in a cynomolgus monkey model, suggesting that hepatic effects on the lipid metabolism are involved in the anti-dyslipidemic actions. Compound T1 (10), which contains the partial structure of T3 (9), reflects almost all of the clinical responses of non-statin chemicals, such as ezetimibe, cholestyramine and torcetrapib in dyslipidemic hamster model. We have previously disclosed the chemotype for FXR antagonist (11) given by a hit-to-lead approach. (Fig. 2) Preliminary structure-activity relationship (SAR) studies revealed that the combination of substituents on cyclohexyl and benzimidazole of 11 improved IC50 values of 12 (0.035 ± 0.002 μM and <0.001 nM) in the FXR time-resolved fluorescence resonance energy transfer (TR-FRET) binding assay and luciferase reporter assay, respectively. (Fig. 2) Computer-assisted modeling studies suggested that the acylated piperidine moiety of 12 would be involved in a hydrogen bonding with His298 of FXR. Additionally, analog 12 controls the target genes of FXR and lacks affinity with other nuclear receptors, and decreases lipid accumulation in 3T3-L1 cells. Based on these results, we considered 12 to be among the most promising candidates for studies on its in vivo biological activities; however, the pharmacokinetic (PK) profile of 12, which could influence in vivo results, has not yet been investigated. The PK profile is a critical aspect of the drug development process other than in vitro and cellular activities and has a great influence on in vivo results. A small modification of the compound, for instance, even the distinction between R and S-enantiomers affects the functions of metabolic enzymes such as cytochrome P450, which in turn affects the PK of the enantiomers. Additionally, not only is the PK important, but also the tissue distribution is one of the key elements affecting in vivo activity. The data given in previous reports underscores the importance of tissue distribution toward the target tissues. One example is that in vivo efficacy of cathepsin K inhibitors is accompanied by their high concentration of the inhibitors in the bone marrow. When heading into future in vivo studies, therefore, the candidates should preferably have highly potent FXR antagonistic activity in vitro, favorable PK profiles and distribution toward the target tissues. We describe herein a comprehensive understanding of how the building blocks in seven regions of 12 relate to the robust antagonistic activity against FXR in order to adjust the in vivo PK profile and the distribution toward the target tissues of 12 without causing the in vitro activity decline. Eventually, we developed our chemotype for FXR antagonists possessing better PK property without causing a decline in the in vitro activity by focusing on the building blocks constituting 12 and culminated in the identification of the compounds that preserved the equivalent activity of 12, but could improve the PK profile and tissue distribution in comparison to 12.