Carboxylic Acid-containing Drugs Research Articles

Electrooxidative Ni-Catalyzed Decarboxylation of Arylacetic Acids Towards the Synthesis of Carbonyls under Air Conditions.

After systematic realization of decarboxylative functionalization of carboxylic acids under heating conditions in our group, we herein reported an electrochemical method for Ni-catalyzed decarboxylative oxygenation of arylacetic acids under open air conditions. The protocol provided corresponding carbonyls including aldehydes and ketones in moderate to satisfactory yields with good functional group tolerance, furthermore, the practicability and advantage of the method was highlighted through Ni-catalyzed oxidative decarboxylation of carboxylic acid-containing drugs and preformation of scalable transformation. Mechanistic studies demonstrated that the possible involvement of free radical intermediate in the conversion.

Pyridine-borane complex-catalysed thioesterification: the direct conversion of carboxylic acids to thioesters.

Thioesters are a common class of biologically active fragments and synthetically useful building blocks. An attractive synthetic approach would be to use simple and bench-stable carboxylic acids as a coupling partner. Herein, we present a 4-bromo pyridine-borane complex as a catalyst for the direct coupling of carboxylic acids with thiols. A wide range of thioesters with good functional group compatibility could be prepared via this metal-free approach. The merit of this strategy is exemplified by the modification of carboxylic acid-containing drugs.

Minimizing the DILI potential of carboxylic acid-containing drugs: a perspective

AbstractDrugs containing carboxylic acid moieties are associated with a range of toxicities, some related directly to their pharmacology and others to the metabolites that they produce on undergoing biotransformations that reduce biological activity and enhance excretion. The reactions involved in metabolism include a wide range of conjugations to the carboxylic acid moiety plus modifications to the spacers used to attach them to the main body of the drug. Here we provide a metabolic perspective on the biotransformations that have been found to occur with drugs that contain a carboxylic acid and discuss the potential of these to cause toxicity. Based on our current understanding of the metabolism of carboxylic acid-containing drugs we then consider approaches that may mitigate toxicity.

Acyl-CoA thioesters as chemically-reactive intermediates of carboxylic acid-containing drugs

Acyl-CoA thioesters as chemically-reactive intermediates of carboxylic acid-containing drugs

Copper-Catalyzed Borylation of Acyl Chlorides with an Alkoxy Diboron Reagent: A Facile Route to Acylboron Compounds.

Herein, the copper‐catalyzed borylation of readily available acyl chlorides with bis(pinacolato)diboron, (B2pin2) or bis(neopentane glycolato)diboron (B2neop2) is reported, which provides stable potassium acyltrifluoroborates (KATs) in good yields from the acylboronate esters. A variety of functional groups are tolerated under the mild reaction conditions (room temperature) and substrates containing different carbon‐skeletons, such as aryl, heteroaryl and primary, secondary, tertiary alkyl are applicable. Acyl N‐methyliminodiacetic acid (MIDA) boronates can also been accessed by modification of the workup procedures. This process is scalable and also amenable to the late‐stage conversion of carboxylic acid‐containing drugs into their acylboron analogues, which have been challenging to prepare previously. A catalytic mechanism is proposed based on in situ monitoring of the reaction between p‐toluoyl chloride and an NHC‐copper(I) boryl complex as well as the isolation of an unusual lithium acylBpinOBpin compound as a key intermediate.

Quantifying proton-induced membrane polarization in single biomimetic giant vesicles

Proton gradients are utilized by cells to power the transport activity of many membrane proteins. Synthetic cells, such as proteo-giant unilamellar vesicles, offer an advanced approach for studying the functionality of membrane proteins in isolation. However, understanding of protein-based transport in vitro requires accurate measurements of proton flux and its accompanying electrochemical gradient across the lipid bilayer. We present an approach to directly quantify the flux of protons across single cell-sized lipid vesicles under modulated electrochemical gradients. Our measurements reveal the corresponding association between proton permeation and transmembrane potential development and its relation to the chemical nature of the conjugated anion (base). In the case of formic acid, we showed that, out of the total amount of permeated protons, a fraction of ≈0.2 traverse the lipid bilayer as H+, with the rest (≈0.8) in the form of a neutral acid. For strong acids (HCl or HNO3), proton permeation was governed by translocation of H+. Accordingly, a larger proton motive force (pmf) was generated for strong acids (pmf=14.2 mV) relative to formic acid (pmf=1.3 mV). We anticipate that our approach will guide the development of protein-based transport driven by proton gradient in artificial cell models and enable a deeper understanding of how vital acids, such as fatty acids, amino acids, bile acids, and carboxylic acid-containing drugs, traverse the lipid bilayer.

Stereocontrolled 1,3-nitrogen migration to access chiral α-amino acids.

α-Amino acids are essential for life as building blocks of proteins and components of diverse natural molecules. In both industry and academia, the incorporation of unnatural amino acids is often desirable for modulating chemical, physical, and pharmaceutical properties. We here report a protocol for the economical and practical synthesis of optically active α-amino acids based on an unprecedented stereocontrolled 1,3-nitrogen shift. Our method employs abundant and easily accessible carboxylic acids as starting materials, which are first connected to a nitrogenation reagent, followed by a highly regio- and enantioselective ruthenium- or iron-catalyzed C(sp3)−H amination. This straightforward method displays a very broad scope, providing rapid access to optically active α-amino acids with aryl, allyl, propargyl, and alkyl side chains, and also permits stereocontrolled late-stage amination of carboxylic acid-containing drugs and natural products.

Recent Developments in the Practical Application of Novel Carboxylic Acid Bioisosteres.

The carboxylic acid moiety is an important functional group which features in the pharmacophore of some 450 drugs. Unfortunately, some carboxylic acid-containing drugs have been withdrawn from market due to unforeseen toxicity issues. Other issues associated with the carboxylate moiety include reduced metabolic stability or limited passive diffusion across biological membranes. Medicinal chemists often turn to bioisosteres to circumvent such obstacles. The aim of this review is to provide a summary of the various applications of novel carboxylic acid bioisosteres which have appeared in the literature since 2013. We have summarised the most recent developments in carboxylic acid bioisosterism. In particular, we focus on the changes in bioactivity, selectivity or physicochemical properties brought about by these substitutions, as well as the advantages and disadvantages of each isostere. The topics discussed herein highlight the continued interest in carboxylate bioisosteres. The development of novel carboxylic acid substitutes which display improved pharmacological profiles is a testament to the innovation and creativity required to overcome the challenges faced in modern drug design.

The chirality determination of amino acids by forming complexes with cyclodextrins and metal ions using ion mobility spectrometry, and a DFT calculation

Chiral recognition is of highly interest in the areas of chemistry, pharmaceuticals, and bioscience. An effective strategy of enantiomeric determination of amino acids (AAs) was developed in this work. All 19 natural AAs enantiomers can be easily distinguished by ion mobility-mass spectrometry of the non-covalent complexes of AAs with cyclodextrins (α-CD, β-CD and γ-CD) and Mg2+ without any chemical derivatization. Differences of the mobilities between the enantiomers’ complexes is from 0.006 to 0.058 V s/cm2. In addition, the complex of [β-CD + Phe + Mg]2+ was selected as an example to study the relative quantification by measuring L/D-Phe at different molar ratio of 10:1 to 1:10 in the μM range, resulting in a good linearity (R2 > 0.99) and high sensitivity at 2 μM. A DFT calculation was also performed to illustrate the detailed molecular structure of the complexes of CDs, Mg2+ and D- or L-Phe. Both experiment and theoretical calculation showed that Mg2+ plays an important role in host/guest interactions, which changed the molecular conformations by non-covalent interaction between Mg2+ and CDs, and resulted in the different collision cross-sections of the complex ions of CDs, Mg2+ and D- or L-AAs in the gas phase. This effective and convenient strategy could potentially be utilized in scientific research and industry for routine enantiomeric determination of natural AAs, peptides and some other small chiral biomolecules such as non-natural AAs and carboxylic acid-containing drugs.

Driving to a Better Understanding of Acyl Glucuronide Transformations Using NMR and Molecular Modeling.

Acyl glucuronide (AG) metabolites of carboxylic acid-containing drugs and products of their transformations have long been implicated in drug-induced liver injury (DILI). To inform on the DILI risk arising from AG reactive intermediates, a comprehensive mechanistic study of enzyme-independent AG rearrangements using nuclear magnetic resonance (NMR) and density functional theory (DFT) was undertaken. NMR spectroscopy was utilized for structure elucidation and kinetics measurements of nine rearrangement and hydrolysis products of 1β-O-acyl glucuronide of ibufenac. To extract rate constants of rearrangement, mutarotation, and hydrolysis from kinetic data, 11 different kinetic models were examined. Model selection and estimated rate constant verification were supported by measurements of H/D kinetic isotope effects. DFT calculations of ground and transition states supported the proposed kinetic mechanisms and helped to explain the unusually fast intramolecular transacylation rates found for some of the intermediates. The findings of the current study reinforce the notion that the short half-life of parent AG and slow hydrolysis rates of AG rearrangement products are the two key factors that can influence the in vivo toxicity of AGs.

Increasing membrane permeability of carboxylic acid-containing drugs using synthetic transmembrane anion transporters.

In this manuscript, we show that small-molecule-based anion transporters can significantly increase the permeability of carboxylic acid containing drugs across lipid bilayers of model vesicles. Due to the drug-like characteristics of the transporters, this finding could not only have implications for drug delivery, but also hints towards potential drug-drug and drug-food interactions.

A CNS-Targeting Prodrug Strategy for Nuclear Receptor Modulators.

The blood-brain barrier is a major impediment for targeted central nervous system (CNS) therapeutics, especially with carboxylic acid-containing drugs. Nuclear receptor modulators, which often feature carboxylic acid motifs for target engagement, have emerged as a class of potentially powerful therapeutics for neurodegenerative CNS diseases. Herein is described a prodrug strategy that directs the biodistribution of parent drug nuclear receptor modulators into the CNS while masking them as functional receptor ligands in the periphery. This prodrug strategy targets a specific amidase, fatty acid amide hydrolase (FAAH), an enzyme with enriched expression in the CNS. Our results demonstrate that this prodrug strategy can be generalized to a variety of carboxylic acid-containing drug structures that satisfy the structural requirements of blood-brain barrier diffusion and FAAH substrate recognition.

Quantitative Evaluation of Reactivity and Toxicity of Acyl Glucuronides by [35S]Cysteine Trapping.

Acyl glucuronides (AGs) are reactive metabolites of carboxylic acid-containing drugs, which are associated with idiosyncratic toxicity (IDT) such as anaphylaxis, drug-induced liver injury, and so on. In this study, we developed a new in vitro approach for the quantitative assessment of the reactivity of AGs and their toxicity risk. Thirteen test drugs were incubated with human liver microsomes and uridine 5'-diphospho-glucuronic acid in the presence of cysteine (Cys) as a trapping agent. Both acylation and glycation Cys adducts formed from the AGs of the test drugs and were analyzed by ultraperformance liquid chromatography-quadrupole time-of-flight mass spectrometry. Acylation Cys adduct formation can closely reflect the reactivity of AGs to predict their IDT risk. Subsequently, we performed a quantitative trapping assay using radiometric analysis, with [35S]-labeled Cys ([35S]Cys) as the trapping agent, and the results showed that the test drugs associated with IDT resulted in a high product formation of [35S]Cys adducts. In conclusion, this approach can be used for the easy and quantitative evaluation of the reactivity of AGs without the need for authentic AG standards and to screen the potential IDT of new chemical entities during the early drug discovery phase.

Neutrophil depletion protects against zomepirac-induced acute kidney injury in mice

Acyl glucuronide (AG) metabolites of carboxylic acid-containing drugs have been implicated in drug toxicity. Zomepirac (ZP) is a non-steroidal anti-inflammatory drug that was withdrawn from the market because of anaphylactic reactions and renal injury. We recently established a novel mouse model of ZP-induced kidney injury by increasing zomepirac acyl-glucuronide (ZP-AG) concentration via pretreatment with tri-O-tolyl phosphate, a nonselective esterase inhibitor, and l-buthionine-(S,R)-sulfoximine, a glutathione synthesis inhibitor. Although we have shown that ZP-AG is responsible for ZP-induced kidney injury in mice, the exact pathogenic mechanisms of ZP-induced kidney injury have not been investigated yet. In this study, we aimed to investigate the role of immune cells in the pathogenesis of ZP-induced kidney injury, as a representative of AG toxicity. We found that the counts of neutrophils and inflammatory monocytes increased in the blood of mice with ZP-induced kidney injury. However, clodronate liposome- or GdCl3-induced monocyte and/or macrophage depletion did not affect blood urea nitrogen and plasma creatinine levels in mice with ZP-induced kidney injury. Neutrophil infiltration into the kidneys was observed in mice with ZP-induced kidney injury, whereas anti-lymphocyte antigen 6 complex, locus G (Ly6G) antibody pretreatment prevented the renal neutrophil infiltration and partially protected against ZP-induced kidney injury. The mRNA expression of neutrophil-infiltrating cytokines and chemokines, interleukin-1α and macrophage inflammatory protein-2α, increased in mice with ZP-induced kidney injury, whereas pretreatment with anti-Ly6G antibody resulted in a marked reduction of their expression. These results suggest that ZP-AG might be involved in kidney injury, partly via induction of neutrophil infiltration. Therefore, this study may provide an important understanding on toxicological role of ZP-AG in vivo that helps to understand toxicity of AG metabolites.

Toxicological role of an acyl glucuronide metabolite in diclofenac-induced acute liver injury in mice.

The acyl glucuronide (AG) metabolites of carboxylic acid-containing drugs are potentially chemically reactive and are suggested to be implicated in toxicity, including hepatotoxicity, nephrotoxicity and drug hypersensitivity reactions. However, it remains unknown whether AG formation is related to toxicity in vivo. In this study, we sought to determine whether AG is involved in the pathogenesis of liver injury using a mouse model of diclofenac (DIC)-induced liver injury. Mice that were administered DIC alone exhibited significantly increased plasma alanine aminotransferase levels, whereas mice that were pretreated with the UDP-glucuronosyltransferase inhibitor (-)-borneol (BOR) exhibited suppressed alanine aminotransferase levels at 3 and 6 h after DIC administration although not significant at 12 h. The plasma DIC-AG concentrations were significantly lower in BOR- and DIC-treated mice than in mice treated with DIC alone. The mRNA expression levels of chemokine (C-X-C motif) ligand 1 (CXCL1), CXCL2 and the neutrophil marker CD11b were reduced in the livers of mice that had been pretreated with BOR compared to those that had been administered DIC alone, whereas mRNA expression of the macrophage marker F4/80 was not altered. An immunohistochemical analysis at 12 h samples revealed that the numbers of myeloperoxidase- and lymphocyte antigen 6 complex-positive cells that infiltrated the liver were significantly reduced in BOR- and DIC-treated mice compared to mice that were treated with DIC alone. These results indicate that DIC-AG is partly involved in the pathogenesis of DIC-induced acute liver injury in mice by activating innate immunity and neutrophils. Copyright © 2016 John Wiley & Sons, Ltd.

Toxicity of Carboxylic Acid-Containing Drugs: The Role of Acyl Migration and CoA Conjugation Investigated.

Many carboxylic acid-containing drugs are associated with idiosyncratic drug toxicity (IDT), which may be caused by reactive acyl glucuronide metabolites. The rate of acyl migration has been earlier suggested as a predictor of acyl glucuronide reactivity. Additionally, acyl Coenzyme A (CoA) conjugates are known to be reactive. Here, 13 drugs with a carboxylic acid moiety were incubated with human liver microsomes to produce acyl glucuronide conjugates for the determination of acyl glucuronide half-lives by acyl migration and with HepaRG cells to monitor the formation of acyl CoA conjugates, their further conjugate metabolites, and trans-acylation products with glutathione. Additionally, in vitro cytotoxicity and mitochondrial toxicity experiments were performed with HepaRG cells to compare the predictability of toxicity. Clearly, longer acyl glucuronide half-lives were observed for safe drugs compared to drugs that can cause IDT. Correlation between half-lives and toxicity classification increased when "relative half-lives," taking into account the formation of isomeric AG-forms due to acyl migration and eliminating the effect of hydrolysis, were used instead of plain disappearance of the initial 1-O-β-AG-form. Correlation was improved further when a daily dose of the drug was taken into account. CoA and related conjugates were detected primarily for the drugs that have the capability to cause IDT, although some exceptions to this were observed. Cytotoxicity and mitochondrial toxicity did not correlate to drug safety. On the basis of the results, the short relative half-life of the acyl glucuronide (high acyl migration rate), high daily dose and detection of acyl CoA conjugates, or further metabolites derived from acyl CoA together seem to indicate that carboxylic acid-containing drugs have a higher probability to cause drug-induced liver injury (DILI).

Toxicological evaluation of acyl glucuronides utilizing half-lives, peptide adducts, and immunostimulation assays

Chemical reactivity of acyl glucuronides (AGs) is believed to be involved in the toxicity of carboxylic acid-containing drugs. Both direct and immune-mediated toxicity have been suggested as possible mechanisms of toxicity; however, it remains unclear. In the present study, we performed assays of half-lives, peptide adducts, and immunostimulation to evaluate the potential risk of AGs of 21 drugs and analyzed the relationship to the toxic category. AGs of all withdrawn drugs tested in this study showed short half-lives and peptide adducts formation, but so did those of several safe drugs. In contrast, only AGs of withdrawn and warning drugs induced interleukin-8 (IL-8) in human peripheral blood mononuclear cells (hPBMCs). Using a DNA microarray assay, we found that zomepirac AG induced the mRNAs of 5 genes, including IL-8 in hPBMCs. In addition, withdrawn and warning drugs were distinguished from safe drugs by an integrated score of relative mRNA expression levels of 5 genes. The immunostimulation assay showed higher sensitivity, specificity, and accuracy compared with other methods. In preclinical drug development, the evaluation of the reactivity of AGs using half-lives and peptide adducts assays followed by the evaluation of immunostimulation by highly reactive AGs using hPBMCs can contribute to improved drug safety.

The Effects of 1-Aminobenzotriazole Inhibition on the Formation of Acyl-Glucuronide and Acyl-Glutathione Metabolites in Rat Hepatocytes

The Effects of 1-Aminobenzotriazole Inhibition on the Formation of Acyl-Glucuronide and Acyl-Glutathione Metabolites in Rat Hepatocytes 1-Aminobenzotriaole (ABT) is a commonly used non-selective mechanism based human and non-human cytochrome P450 (P450) inactivator. However, the direct effects of ABT mediated P450 inhibition on conjugative metabolism, specifically acyl-glucuronide and acyl-glutathione formation has not been previously investigated. In the present study, we evaluated the in vitro effects of ABT induced inhibition of P450 metabolism on the formation of 1-O-acyl-glucuronides of the carboxylic acid-containing drugs gemfibrozil (GEM), tolmetin (TOL), mefenamic acid (MFA), and diclofenac (DCF), and the S-acyl-glutathione formation of MFA and DCF in rat hepatocytes. In vitro incubations of each carboxylic acid-containing drug (100 μM) separately in rat hepatocytes preincubated (30 min) with ABT (500 μM), resulted in 12.7%, 30%, 37%, and 40% increases in the formation of 1-O-acyl-glucuronides at the 30 min time point for GEM, TOL, MFA, and DCF, respectively. However, in the same incubations, MFA and DCF resulted in little to no difference in maximum glutathione concentrations formed in the presence of ABT, suggesting that the mefenamic acid-S-acyl-glutathione (MFA-GSH) and diclofenac-S-acyl-glutathione (DCF-GSH) formation was not the direct result of their corresponding acyl-glucuronides inherent reactivity.

A Novel Aromatic Carboxylic Acid Inactivates Luciferase by Acylation of an Enzymatically Active Regulatory Lysine Residue

Firefly luciferase (Luc) is widely used as a reporter enzyme in cell-based assays for gene expression. A novel aromatic carboxylic acid, F-53, reported here for the first time, substantially inhibited the enzymatic activity of Luc in a Luc reporter screening. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and tandem mass spectrometry (MS/MS) analyses showed that F-53 modifies Luc at lysine-529 via amidation of the F-53 carboxyl group. The lysine-529 residue of Luc, which plays a regulatory catalytic role, can be acetylated. Luc also has a long-chain fatty acyl-CoA synthase activity. An in vitro assay that involved both recombinant Luc and mouse liver microsomes identified F-53-CoA as the reactive form produced from F-53. However, whereas the inhibitory effect of F-53 is observed in Hela cells that transiently expressed Luc, it is not observed in an in vitro assay that involves recombinant Luc alone. Therefore, insights into the activities of certain mammalian transferases can be translated to better understand the acylation by F-53. The insights from this study about the novel inhibitory modification mechanism might help not only to avoid misinterpretation of the results of Luc-based reporter screening assays but also to explain the pharmacological and toxicological effects of carboxylic acid-containing drugs.

Drug-S-Acyl-Glutathione Thioesters: Synthesis, Bioanalytical Properties, Chemical Reactivity, Biological Formation and Degradation

Carboxylic acid-containing drugs can be metabolized to chemically-reactive acyl glucuronide, S-acyl-CoA thioester, and/or intermediate acyl-adenylate metabolites that are capable of transacylating the cysteinyl-thiol of glutathione (GSH) resulting in the formation of drug-S-acyl-GSH thioesters detected in-vivo in bile and in-vitro in hepatocytes. Authentic S-acyl-GSH thioesters of carboxylic acids can be readily synthesized by modifying the cysteinyl-thiol group of GSH with an applicable acylating reagent. Bionanalytical characterization of S-acyl-GSH derivatives has demonstrated enhanced extraction efficiency from biological samples when formic acid is included in appropriate extraction solvents, and that tandem mass spectrometry of S-acyl-GSH conjugates results in fragmentation producing a common MH+-147 Da product ion. Chemical reactivity comparisons have shown that S-acyl-CoA thioester and acyl-adenylate conjugates are more reactive than their corresponding 1-β-O-acyl glucuronides toward the transacylation of GSH forming S-acyl-GSH thioesters. S-Acyl-GSH thioester derivatives are also chemically-reactive electrophiles capable of transacylating biological nucleophiles. Glutathione S-transferases (GSTs) weakly catalyze S-acyl-GSH conjugate formation from S-acyl-CoA, acyl-adenylate, and 1-β-O-acyl glucuronide substrates; however purified-GSTs have also been shown to hydrolyze S-acyl-GSH thioesters. Mechanistic in vitro studies in hepatocytes have revealed the primary importance of the S-acyl-CoA formation pathway leading to S-acyl-GSH-adduct formation. In addition to being hydrolytically-unstable in hepatocytes and plasma, S-acyl-GSH thioesters undergo γ-glutamyltranspeptidase-mediated cleavage of the γ-glutamyl-group leading to N-acyl-cysteinylglycine amide-linked products. In summary, S-acyl GSH thioesters are indicators of reactive transacylating metabolite formation produced from the biotransformation of carboxylic acids, but since they are also chemically-reactive, perhaps these derivatives can contribute to covalent binding to tissue proteins and potential toxicity.