Pharmacokinetic screening of soluble epoxide hydrolase inhibitors in dogs

Abstract

Epoxyeicosatrienoic acids that have anti-hypertensive and anti-inflammatory properties are mainly metabolized by soluble epoxide hydrolase (sEH, EC 3.3.2.3). Therefore, sEH has emerged as a therapeutic target for treating various cardiovascular diseases and inflammatory pain. N,N'-Disubstituted ureas are potent sEH inhibitors in vitro. However, in vivo usage of early sEH inhibitors has been limited by their low bioavailability and poor physiochemical properties. Therefore, a group of highly potent compounds with more drug-like physiochemical properties were evaluated by monitoring their plasma profiles in dogs treated orally with sEH inhibitors. Urea compounds with an adamantyl or a 4-trifluoromethoxyphenyl group on one side and a piperidyl or a cyclohexyl ether group on the other side of the urea function showed pharmacokinetic profiles with high plasma concentrations and long half lives. In particular, the inhibitor trans-4-[4-(3-adamantan-1-yl-ureido)-cyclohexyloxy]-benzoic acid (t-AUCB) not only is very potent with good physiochemical properties, but also shows high oral bioavailability for doses ranging from 0.01 to 1mg/kg. This compound is also very potent against the sEH of several mammals, suggesting that t-AUCB will be an excellent tool to evaluate the biology of sEH in multiple animal models. Such compounds may also be a valuable lead for the development of veterinary therapeutics.

Fig. 1

Plasma concentration-time profiles of sEH inhibitors with varied non-polar group (R₁) after an oral dose of 0.3 mg/kg body weight. (a) Alkyl acid and derivatives (AUDA series) (● 1, ○ 8, and ▼ 12). (b) Cyclohexyl ether linker with cis-ether polar group and para-fluorophenyl R₂ group (● 36, ○ 44, ▼ 48, and Δ 47). (c) Piperidyl linker with a sulfonamide group (● 17, ○ 27, and ▼ 32). Each curve represents data from one dog (n = 1).

Fig. 2

Plasma concentration-time profiles of sEH inhibitors with the adamantyl non-polar group and varied linker, polar group and R₂ group after an oral dose of 0.3 mg/kgbody weight (n = 1). (a) Polyethylene glycol derivatives (● 3, ○ 4, ▼ 33, Δ 53 and ■ 52). (b) Heterocylic R₂ group with varied linkers (● 34, ○ 64, and ▼ 65). (c) Phenyl linker with varied R₂ groups (● 56, ○ 57, ▼ 58, and Δ 62). Each curve represents data from one dog (n = 1).

Fig. 3

Plasma concentration-time profiles of sEH inhibitors with piperidyl linker after an oral dose of 0.3 mg/kgbody weight (n = 1). (a) Primary pharmacophore of urea (■ 14) or amide group (□ 72). (b) Urea with adamantyl R₁ group, a piperidyl linker and amides with varying chain lengths (● 14, ○ 15, and ▼ 19). (c) Urea with 4-trifluoromethoxyphenyl R₁ group, a piperidyl linker and amides with varying chain lengths (● 24(CH₃), ○ 25(C₂H₅), and ▼ 26(C₃H₇)). Each curve represents data from one dog (n = 1).

Fig. 4

Plasma concentration-time profiles of sEH inhibitors with cyclohexyl ether linker after an oral dose of 0.3 mg/kgbody weight (n = 1). Cyclohexyl ether linker with cis- or trans- ether polar group, para- or meta-benzoic acid and varying R₁ groups (● 39, ○ 40, ▼ 45, and Δ 41). Each curve represents data from one dog (n = 1).

Fig. 5

Plasma concentration-time profile of 3 AEPU (a), 14 APAU (b), and 39 t-AUCB (c) after an i.v. or p.o. dose of 0.3 mg/kgbody weight (n = 3) except AEPU after an i.v. dose of 0.1 mg/kg body weight. Data are shown as mean ± S.D. (n = 3). Insert figure: Log scale of plasma concentration-time profile following i.v. administration.

Fig. 6

Plasma concentration-time profile of 39 t-AUCB after an oral dose of 0.03, 0.1, 0.3, and 1 mg/kgbody weight. The AUC vs. dose relationship for t-AUCB approaches linearity (r² = 0.98). Data are shown as mean ± S.D among different dogs. (n=3).

Fig. 7

Comparison of exposure (plasma AUC) as a function of potency (IC₅₀) for a series of sEH inhibitors. (a) The log AUC/IC₅₀ ratio for humans using the canine AUC at 0.3 mg/kg body weight and the human IC₅₀ calculated based on the radioactive t-DPPO sEH assay. The y-axis represents the ratio of AUC/IC₅₀ normalized to AUDA (1) in log scale. (b) The log AUC/IC₅₀ ratio for dogs using the canine AUC at 0.3 mg/kg body weight and the canine IC₅₀ calculated based on the radioactive t-DPPO sEH assay.