Discovery of MK-0476, a potent and orally active leukotriene D4 receptor antagonist devoid of peroxisomal enxyme induction

Shortening Synthetic Routes to Small Molecule Active Pharmaceutical Ingredients Employing Biocatalytic Methods

Biocatalysis, using enzymes for organic synthesis, has emerged as powerful tool for the synthesis of active pharmaceutical ingredients (APIs). The first industrial biocatalytic processes launched in the first half of the last century exploited whole-cell microorganisms where the specific enzyme at work was not known. In the meantime, novel molecular biology methods, such as efficient gene sequencing and synthesis, triggered breakthroughs in directed evolution for the rapid development of process-stable enzymes with broad substrate scope and good selectivities tailored for specific substrates. To date, enzymes are employed to enable shorter, more efficient, and more sustainable alternative routes toward (established) small molecule APIs, and are additionally used to perform standard reactions in API synthesis more efficiently. Herein, large-scale synthetic routes containing biocatalytic key steps toward >130 APIs of approved drugs and drug candidates are compared with the corresponding chemical protocols (if available) regarding the steps, reaction conditions, and scale. The review is structured according to the functional group formed in the reaction.

Cyclopropyl Scaffold: A Generalist for Marketed Drugs

In recent decades, much attention has been given to cyclopropyl scaffolds, which commonly exist in natural products and synthetic organic molecules. Clinical drug molecules with cyclopropyl rings are an area of focus in therapeutic research due to their interesting chemical properties and unique pharmacology activity. These molecular drugs against different targets are applicable in some therapeutic treatment fields including cancer, infection, respiratory disorder, cardiovascular and cerebrovascular diseases, dysphrenia, nervous system disorders, endocrine and metabolic disorders, skin disease, digestive disorders, urogenital diseases, otolaryngological and dental diseases, and eye diseases. This review is a guide for pharmacologists who are in search of valid preclinical/clinical drug compounds where the progress, from 1961 to the present day, of approved marketed drugs containing cyclopropyl scaffold is examined.

Opportunities and Challenges for Fatty Acid Mimetics in Drug Discovery

Fatty acids beyond their role as an endogenous energy source and storage are increasingly considered as signaling molecules regulating various physiological effects in metabolism and inflammation. Accordingly, the molecular targets involved in formation and physiological activities of fatty acids hold significant therapeutic potential. A number of these fatty acid targets are addressed by some of the oldest and most widely used drugs such as cyclooxygenase inhibiting NSAIDs, whereas others remain unexploited. Compounds orthosterically binding to proteins that endogenously bind fatty acids are considered as fatty acid mimetics. On the basis of their structural resemblance, fatty acid mimetics constitute a family of bioactive compounds showing specific binding thermodynamics and following similar pharmacokinetic mechanisms. This perspective systematically evaluates targets for fatty acid mimetics, investigates their common structural characteristics, and highlights demands in their discovery and design. In summary, fatty acid mimetics share particularly favorable characteristics justifying the conclusion that their therapeutic potential vastly outweighs the challenges in their design.

Small structural changes of the imidazopyridine diacylglycerol acyltransferase 2 (DGAT2) inhibitors produce an improved safety profile

Small molecule DGAT2 inhibitors have shown promise for the treatment of metabolic diseases in preclinical models. Herein, we report the first toxicological evaluation of imidazopyridine-based DGAT2 inhibitors and show that the arteriopathy associated with imidazopyridine 1 can be mitigated with small structural modifications, and is thus not mechanism related.

The "Cyclopropyl Fragment" is a Versatile Player that Frequently Appears in Preclinical/Clinical Drug Molecules

Recently, there has been an increasing use of the cyclopropyl ring in drug development to transition drug candidates from the preclinical to clinical stage. Important features of the cyclopropane ring are, the (1) coplanarity of the three carbon atoms, (2) relatively shorter (1.51 Å) C-C bonds, (3) enhanced π-character of C-C bonds, and (4) C-H bonds are shorter and stronger than those in alkanes. The present review will focus on the contributions that a cyclopropyl ring makes to the properties of drugs containing it. Consequently, the cyclopropyl ring addresses multiple roadblocks that can occur during drug discovery such as (a) enhancing potency, (b) reducing off-target effects,

Iron catalyzed enantioselective sulfa-Michael addition: a four-step synthesis of the anti-asthma agent Montelukast

Asymmetric conjugate addition of thiols to acyclic α,β-unsaturated ketones catalyzed by an iron(iii)–salen complex gives β-thioketones in high enantiomeric excess.

Modulation of leukotriene D4 attenuates the development of seizures in mice

The present study has been designed to pharmacologically investigate the effect of Montelukast sodium, a leukotriene D(4) receptor antagonist, and 1,2,3,4, tetrahydroisoquinoline, a leukotriene D(4) synthetic pathway inhibitor, on the pathophysiological progression of seizures using mouse models of kindled epilepsy and status epilepticus induced spontaneous recurrent seizures. Pentylenetetrazole (40 mg kg(-1)) (PTZ) administration every second day for a period of 15 d was used to elicit chemically induced kindled seizure activity in mice. In a separate set of groups, fifty consecutive electroshocks were delivered to mice using corneal electrodes with continuously increasing intensity with an inter-shock interval of 40s. Severity of kindled seizures was assessed in terms of a composite kindled seizure severity score (KSSS). Pilocarpine (100 mg kg(-1)) was injected every twenty minutes until the onset of status epilepticus. A spontaneous recurrent seizure severity score (SRSSS) was recorded as a measure of quantitative assessment of the progressive development of spontaneous recurrent seizures induced after pilocarpine status epilepticus. Sub-acute PTZ administration and electroshock induced the development of severe form of kindled seizures in mice. Severity of kindled seizures was assessed in terms of a composite kindled seizure severity score. Further, pharmacological status epilepticus elicited a progressive evolution of spontaneous recurrent seizures in the animals. However, Montelukast sodium, a leukotriene D(4) receptor antagonist, as well as 1,2,3,4, tetrahydroisoquinoline, a leukotriene D(4) synthetic pathway inhibitor, markedly and dose dependently suppressed the development of kindled seizures as well as pilocarpine induced spontaneous recurrent seizures. Therefore, leukotriene D(4) may be implicated in the pathogenesis of seizures.

Transition metal catalyzed synthesis of aryl sulfides

The presence of aryl sulfides in biologically active compounds has resulted in the development of new methods to form carbon-sulfur bonds. The synthesis of aryl sulfides via metal catalysis has significantly increased in recent years. Historically, thiolates and sulfides have been thought to plague catalyst activity in the presence of transition metals. Indeed, strong coordination of thiolates and thioethers to transition metals can often hinder catalytic activity; however, various catalysts are able to withstand catalyst deactivation and form aryl carbon-sulfur bonds in high-yielding transformations. This review discusses the metal-catalyzed arylation of thiols and the use of disulfides as metal-thiolate precursors for the formation of C-S bonds.

Pharmacophore identification, synthesis, and biological evaluation of carboxylated chalcone derivatives as CysLT1 antagonists

The pharmacophore model (Hypo1) with a well prediction capacity for CysLT(1) antagonists was developed using Catalyst/HypoGen program. Virtual screening against an in-house database consisted of carboxylated chalcones using Hypo1 was performed. Retrieved hits 26a, 26b, 27a, and 27b were synthesized and biological evaluated, the results of which demonstrated that these compounds showed moderate to good CysLT(1) antagonistic activities. This study indicated that the generated model (Hypo1) is a reliable and useful tool in lead optimization for novel CysLT(1) antagonists.

Discovery of 4-[(2S)-2-{[4-(4-chlorophenoxy)phenoxy]methyl}-1-pyrrolidinyl]butanoic acid (DG-051) as a novel leukotriene A4 hydrolase inhibitor of leukotriene B4 biosynthesis

Both in-house human genetic and literature data have converged on the identification of leukotriene 4 hydrolase (LTA(4)H) as a key target for the treatment of cardiovascular disease. We combined fragment-based crystallography screening with an iterative medicinal chemistry effort to optimize inhibitors of LTA(4)H. Ligand efficiency was followed throughout our structure-activity studies. As applied within the context of LTA(4)H inhibitor design, the chemistry team was able to design a potent compound 20 (DG-051) (K(d) = 26 nM) with high aqueous solubility (>30 mg/mL) and high oral bioavailability (>80% across species) that is currently undergoing clinical evaluation for the treatment of myocardial infarction and stroke. The structural biology-chemistry interaction described in this paper provides a sound alternative to conventional screening techniques. This is the first example of a gene-to-clinic paradigm enabled by a fragment-based drug discovery effort.

The targeted oral, once-daily phosphodiesterase 4 inhibitor roflumilast and the leukotriene receptor antagonist montelukast do not exhibit significant pharmacokinetic interactions

This nonrandomized, fixed-sequence, 3-period study investigated potential pharmacokinetic interactions between the leukotriene receptor antagonist montelukast, approved for the treatment of asthma, and roflumilast, an oral, once-daily phosphodiesterase 4 inhibitor in clinical development for asthma and chronic obstructive pulmonary disease. Pharmacokinetic interactions are of interest because both drugs may be coadministered and share a common metabolic pathway via cytochrome P450 3A. Single-dose montelukast (10 mg, po) was administered alone in period 1, followed by repeated once-daily roflumilast alone (500 microg, po) for 12 days (period 2). In period 3, 500 microg qd roflumilast was coadministered with 10 mg qd montelukast for 8 days. Different pharmacokinetic parameters were evaluated for montelukast alone, for steady-state roflumilast and its pharmacologically active metabolite roflumilast N-oxide alone, for single-dose montelukast when coadministered with steady-state roflumilast, and for steady-state roflumilast and its N-oxide metabolite when coadministered with steady-state montelukast. The AUC and Cmax of montelukast were modestly increased by 9% and 8%, respectively, when single-dose montelukast was coadministered with steady-state roflumilast. The pharmacokinetics of roflumilast and roflumilast N-oxide in steady state remained unchanged when repeat-dose montelukast was coadministered at steady-state. Concomitant administration of both drugs was well tolerated. These findings suggest that no dose adjustment is warranted for either drug when roflumilast and montelukast are coadministered.

Determination of montelukast sodium by capillary electrophoresis

This work verifies the potential of CE in the analysis of significant impurities of montelukast sodium - an active ingredient for the treatment of bronchial asthma. Using 20 mM borate buffer pH 9.2 with 10 mM SDS and 10 mM (2-hydroxypropyl)-gamma-CD (2HP-gamma-CD) it was possible to separate montelukast and several impurities, including its cis-isomer, after exposure to light and oxygen. The obtained method surpasses a chromatographic method for montelukast sodium in terms of time of analysis (9 min of CE analysis vs. 35 min HPLC) and efficiency (CE offered over 900 000 theoretical plates for montelukast). Good repeatability of the method was supported by the low % RSD for the migration time of montelukast (0.53%). For the first time, the capillary electrophoretic method was employed for temporal study of the degradation of montelukast. The results showed that degradation of montelukast and the formation of the cis-isomer mainly occurred during the first 2 days of exposure, and occurred to a higher degree when there was no contact with the air (oxygen) in the exposed sample.

Montelukast in the treatment of allergic rhinitis: an evidence-based review

Cysteinyl-leukotrienes (CysLTs) are endogenous mediators of inflammation and play an important role in allergic airway disease by stimulating bronchoconstriction, mucus production, mucosal oedema and inflammation, airway infiltration by eosinophils, and dendritic cell maturation that prepares for future allergic response. Montelukast inhibits these actions by blocking type 1 CysLT receptors found on immunocytes, smooth muscle and endothelium in the respiratory mucosa. Initially developed as a treatment for asthma, montelukast has more recently found use in the treatment of allergic rhinitis (AR). We conducted a systematic review of studies that have evaluated montelukast in the treatment of seasonal AR (SAR) and perennial AR (PAR), with and without concomitant asthma. Primary consideration was given to large, randomised, placebo-controlled, double-blind clinical trials in which AR endpoints were assessed and the use of concurrent treatments for AR was excluded. Eight such studies were found in the literature. The primary endpoint in these was daytime nasal symptom severity represented by a composite score derived from individual self-ratings of nasal congestion, rhinorrhoea, nasal pruritus and sneezing. Secondary endpoints have included these individual nasal symptom scores, additional scores for eye, ear and throat symptoms, the impact of rhinitis on quality of sleep, global evaluations of outcome by patients and physicians, and measures of the severity of concomitant asthma. A general outcome was that patients treated with montelukast had significantly greater improvements in their symptoms of SAR and PAR than did patients who were given a placebo. As monotherapy, montelukast exhibited efficacy similar to that of loratadine, but less than that of the intranasally administered corticosteroid fluticasone propionate. The use of montelukast in combination with antihistamines such as loratadine or cetirizine has generally resulted in greater efficacy than when these agents were used alone, and in some studies has produced results comparable with intranasally applied corticosteroids. In patients with AR comorbid with asthma, montelukast treatment has resulted in significant improvements in both, compared with placebo. Montelukast is well tolerated and has a favourable safety profile; adverse events have occurred at similar frequencies in patients taking either montelukast or placebo. Montelukast provides an effective and well tolerated oral treatment for allergic airway inflammation in patients with SAR or PAR without asthma, and in patients in whom AR is comorbid with asthma.

Complexation study of cinalukast and montelukast with cyclodextrines

A fluorimetric study on the spectral characteristics of two antileukotrienes, cinalukast and montelukast, has been performed. Ionization constants of both of them have been photometrically calculated. Cinalukast pK(a) in ethanol:water 50:50 (v/v) medium resulted to be 2.2+/-0.1. Because the spectral characteristics of montelukast are widely affected by the solvent nature, pK(a) was estimated in two different ethanol:water media, 70:30 (v/v) and 10:90 (v/v) and the values calculated were pK(a)=2.9+/-0.1, and pK(a1)=2.0+/-0.1 and pK(a2)=6.5+/-0.1, respectively. It has been proven that the fluorescence of both, cinalukast and montelukast, is significantly intensified in the presence of cyclodextrins (CyDs). The host-guest complexation processes between cinalukast and alpha-CyD or heptakis-(2,6-di-O-methyl)-beta-cyclodextrin (DIMEB) and between montelukast and DIMEB have been investigated by fluorescence spectroscopy. A 1:1 stoichiometric ratio was established for the three studied inclusion complexes. The changes produced on the fluorescence of cinalukast or montelukast, when they are included on the hydrophobic CyD cavity are used to calculate their association constants by a non-linear regression method. Semiempirical MO calculations using AM1 method were performed in order to characterize the studied inclusion complexes. A new method for cinalukast determination in human serum, based on the fluorescence of the complex cinalukast-DIMEB exhibiting limit of detection of 7.95 ng mL(-1) has been proposed with satisfactory results. Adequate recovery values between 95 and 103% were calculated at five different concentration levels.

Palladium-catalyzed cross-coupling reactions in total synthesis

In studying the evolution of organic chemistry and grasping its essence, one comes quickly to the conclusion that no other type of reaction plays as large a role in shaping this domain of science than carbon-carbon bond-forming reactions. The Grignard, Diels-Alder, and Wittig reactions are but three prominent examples of such processes, and are among those which have undeniably exercised decisive roles in the last century in the emergence of chemical synthesis as we know it today. In the last quarter of the 20th century, a new family of carbon-carbon bond-forming reactions based on transition-metal catalysts evolved as powerful tools in synthesis. Among them, the palladium-catalyzed cross-coupling reactions are the most prominent. In this Review, highlights of a number of selected syntheses are discussed. The examples chosen demonstrate the enormous power of these processes in the art of total synthesis and underscore their future potential in chemical synthesis.

Copper(I) hydride-catalyzed asymmetric hydrosilylation of heteroaromatic ketones

In situ generation of CuH ligated by Takasago's new nonracemic ligand, DTBM-SEGPHOS, leads to an especially reactive reagent capable of effecting asymmetric hydrosilylation of heteroaromatic (H) ketones under very mild conditions. PMHS serves as an inexpensive source of hydride. Substrate-to-ligand ratios on the order of 2000:1 are employed. [reaction: see text]

Montelukast: a review of its therapeutic potential in persistent asthma

Montelukast is a cysteinyl leukotriene receptor antagonist used to treat persistent asthma in patients aged > or = 6 years. The drug has a rapid onset of action. Improvements in lung function and reductions in as-needed beta2-agonist usage are apparent within 1 day of initiating montelukast treatment in adults and adolescents (aged > or = 15 years treated with 10 mg/day) or children (aged 6 to 14 years treated with 5 mg/day) with persistent asthma as shown in clinical trials. In two 12-week, multicentre, randomised, double-blind studies in adults and adolescents aged > or = 15 years with persistent asthma [forced expiratory volume in 1 second (FEV1) = 50 to 85% predicted] there was significantly (p < 0.05) greater improvement in FEV1, symptom scores, peak expiratory flow (PEF), as-needed beta2-agonist use, peripheral eosinophil counts and health-related quality of life (QOL) in patients treated with montelukast 10 mg/day than in recipients of placebo. Improvements were significantly greater in patients treated with inhaled beclomethasone 400 microg/day than in recipients of montelukast 10 mg/day in 1 of these studies. Nonetheless, 42% of montelukast recipients experienced > or = 11% improvement in FEV1, the median improvement in this parameter in beclomethasone-treated patients. In an 8-week multicentre, randomised, double-blind, study in children aged 6 to 14 years with persistent asthma (FEV1 50 to 85% predicted), montelukast 5 mg/day produced significantly greater improvements in FEV1, clinic PEF, as-needed beta2-agonist use, peripheral eosinophil counts, asthma exacerbations and QOL scores than placebo. The combination of montelukast 10 mg/day plus inhaled beclomethasone 200 microg twice daily provided significantly better asthma control than inhaled beclomethasone 200 microg twice daily in adults with poorly controlled asthma (mean FEV1 = 72% predicted) despite 4 weeks treatment with inhaled beclomethasone. Patients receiving the combination experienced significant improvements in FEV1 and morning PEF, significant reductions in daytime symptom scores, as-needed beta2 agonist usage and night-time awakenings with asthma, and had significantly lower peripheral blood eosinophil counts after 16 weeks in this multicentre, randomised, double-blind, placebo-controlled study. Among adults (FEV1 > or = 70%) treated with montelukast 10 mg/day for 12 weeks, inhaled corticosteroid dosages were titrated downward by 47% (vs 30% in placebo recipients), 40% of patients were tapered off of inhaled corticosteroids (vs 29%), and significantly fewer patients (16 vs 30%) experienced failed corticosteroid rescues in a multicentre, randomised, double-blind study. During clinical studies, the frequency of adverse events in montelukast-treated adults, adolescents and children was similar to that in placebo recipients. In conclusion, montelukast is well tolerated and effective in adults and children aged > or = 6 years with persistent asthma including those with exercise-induced bronchoconstriction and/or aspirin sensitivity. Furthermore, montelukast has glucocorticoid sparing properties. Hence, montelukast, as monotherapy in patients with mild persistent asthma, or as an adjunct to inhaled corticosteroids is useful across a broad spectrum of patients with persistent asthma.

Leukotrienes, leukotriene receptor antagonists and leukotriene synthesis inhibitors in asthma: an update. Part I: synthesis, receptors and role of leukotrienes in asthma

Asthma is a chronic inflammatory disease associated with airflow obstruction. Airflow obstruction results from contraction of airway smooth muscle, mucosal oedema, increased secretion of mucus and infiltration of the airway wall by inflammatory cells, particularly eosinophils. Leukotrienes are thought to contribute to the pathophysiology of asthma. Leukotrienes are synthesised from arachidonic acid by a specific synthesis pathway whose key enzyme is 5-lipoxygenase. Cysteinyl leukotrienes (leukotrienes C4, D4 and E4) have been shown to mimic all the pathologic changes that are characteristic of asthma, whereas leukotriene B4 does not appear to exert biological properties relevant to asthma. Cysteinyl leukotrienes bind to two receptor subtypes: CysLT1 and CysLT2. Most of the biological properties of cysteinyl leukotrienes relevant to asthma are mediated through CysLT1 receptor stimulation.

Leukotrienes, leukotriene receptor antagonists and leukotriene synthesis inhibitors in asthma: an update. Part II: clinical studies with leukotriene receptor antagonists and leukotriene synthesis inhibitors in asthma

The demonstration that leukotrienes, mainly cysteinyl leukotrienes, have biological properties relevant to the pathogenesis of asthma has stimulated the development of many therapeutic compounds to block these deleterious effects. Two main classes of leukotriene modulators have been developed: CysLT1 receptor antagonists and leukotriene synthesis inhibitors. This article reviews the pharmacodynamics, the effects on baseline airway function, the protective effects in airway challenges as well as the results in chronic asthma of the different leukotriene modulators. In addition, the complementary anti-inflammatory effect of leukotriene modulators to that of corticosteroids and H1-histamine receptor antagonists is reviewed. Finally, a concise overview of the clinical responsiveness to this new class of drug, the safety and the drug interactions as well as the place in the strategies of treatment for asthmatic patients of the leukotriene modulators is also provided.

N-carbamoyl analogs of Zafirlukast: potent receptor antagonists of leukotriene D4

Exploration of the indole nitrogen region of Zafirlukast (1) has uncovered a potent series of cysteinyl leukotriene D4 (LTD4) antagonists. These studies showed that a variety of functionality could be incorporated in this region of the molecule without sacrificing potency. Efforts to exploit this site in order to improve oral efficacy are discussed.