Novel Metabolic Bioactivation Mechanism for a Series of Anti-Inflammatory Agents (2,5-Diaminothiophene Derivatives) Mediated by Cytochrome P450 Enzymes

Abstract

ABSTRACT:The thiophene moiety is considered a structural alert in molecular design in drug discovery, largely because several thiophene-containing drugs, including tienilic acid and suprofen, have been withdrawn from the market because of toxicities. Reactive thiophene intermediates, activated via sulfur oxidation or ring epoxidation, are possible culprits for these adverse side effects. In this work, the metabolic activation of an anti-inflammatory agent, 1-(3-carbamoyl-5-(2,3,5-trichlorobenzamido)thiophen-2-yl)urea), containing a 2,5-diaminothiophene structure, was studied in liver microsomes in the presence of glutathione or N-acetylcysteine as trapping agents. In addition, the glutathione conjugate was detected in bile from a bile duct-cannulated rat study. The structure of the glutathione conjugate was identified by mass spectrometry and 1 H NMR. The glutathione molecule was attached to the thiophene ring, replacing the existing proton. Metabolic phenotyping experiments, using chemical inhibitors or recombinant cytochromes P450 (P450), demonstrated that CYP3A4 was the major P450 enzyme responsible for the metabolic activation, followed by CYP1A2, 2Cs, and 2D6. A novel metabolic activation mechanism is proposed whereby the 2,5-diaminothiophene moiety undergoes oxidation to a 2,5-diimine thiophene reactive intermediate. This mechanism was used to support efforts to eliminate reactive metabolite generation via structural modification of ring substituents using structure-activity relationships. The disruption of formation of the 2,5-diimine reactive intermediate resulted in the elimination of glutathione conjugate formation both in vitro and in vivo and provided a rational approach to mitigating potential safety risks associated with this class of thiophenes in drug research and development.

Potent and Orally Bioavailable GPR142 Agonists as Novel Insulin Secretagogues for the Treatment of Type 2 Diabetes

“…Introduction of the ethoxymethyl side chain instead of the butyl side chain gave compound 23, which showed comparable GPR142 agonistic activity and metabolic stability to 13; moreover, its hydrophobicity (LogD = 2.2) was in an optimal range (Table 3). 12 Thiophene is known to give reactive metabolite in vivo and have potential of idiosyncratic toxicity, 13 in that we investigated substitution of thiophene ring particularly with a nonaromatic saturated group. To facilitate the exploration of replacements for the thiophene, an efficient synthesis was developed to allow the introduction of this moiety at the last step, as shown in Scheme 2.…”

Mechanistic Approaches for Modifying the Coordination Sphere of Metal–Amyloid-β Complexes: Covalent Adduct Formation and Oxidation

“…A second nucleophilic attack on thiophene, after possible epoxidation of thiophene in the Aβ covalently bound to 2-methylthiophene, 37,38 could afford a covalent adduct with Aβ as the final product with the addition of 94 Da to native Aβ [Scheme 1 (i)]. 39 To support whether the fragmentation of L1 to TM is necessary for its covalent linkage Ag/AgCl in H2O). 29,40,41 Cu(I)-Ab then reacts with O2 forming Cu(II)(Ab40)(O2 •-) and Cu(II)(Ab40)(O2 2-) intermediates under aerobic conditions [Scheme 1 (iii), top], which could lead to Ab oxidation.…”

Gauging Reactive Metabolites in Drug-Induced Toxicity

“…While there are several compounds that have been utilized as trapping agents for detection of reactive metabolites, some of the most common are glutathione [1,[113][114][115][116], Nacetylcysteine [117][118][119][120], cyanide [121][122][123][124], semicarbazide [125], methoxylamine [126,127], N-acetyllysine [128,129], and N-acetyltyrosine [130][131][132]. Glutathione and Nacetylcysteine are used to trap soft electrophiles such as quinones.…”