anti-LT Therapy Research Articles

Discovery of Novel 5-Lipoxygenase-Activating Protein (FLAP) Inhibitors by Exploiting a Multistep Virtual Screening Protocol.

Leukotrienes (LTs) are proinflammatory mediators derived from arachidonic acid (AA), which play significant roles in inflammatory diseases. The 5-lipoxygenase-activating protein (FLAP) is an integral membrane protein, which is essential for the initial step in LT biosynthesis. The aim of this study was to discover novel and chemically diverse FLAP inhibitors for treatment of inflammatory diseases requiring anti-LT therapy. Both ligand- and structure-based approaches were applied to explain the activities of known FLAP inhibitors in relation to their predicted binding modes. We gained valuable insights into the binding modes of the inhibitors by molecular modeling and generated a multistep virtual screening (VS) workflow in which 6.2 million compounds were virtually screened, and the molecular hypotheses were validated by testing VS-hit compounds biologically. The most potent hit compounds showed significant inhibition of FLAP-dependent cellular LT biosynthesis with IC50 values in the range from 0.13 to 0.87 μM. Collectively, this study provided novel bioactive chemotypes with potential for further development as effective anti-inflammatory drugs.

Androgen-mediated sex bias impairs efficiency of leukotriene biosynthesis inhibitors in males.

Proinflammatory leukotrienes (LTs) are produced by 5-lipoxygenase (5-LO) aided by 5-LO-activating protein (FLAP). LT biosynthesis inhibitors are currently under clinical investigation as treatments for respiratory and cardiovascular diseases. Here, we have revealed a sex bias in the efficiency of clinically relevant LT biosynthesis inhibitors, showing that their effects are superior in females. We found that androgens cause these sex differences by impeding the LT-biosynthetic 5-LO/FLAP complex assembly. Lower doses of the FLAP inhibitor MK886 were required to reduce LTB4 levels in exudates of female versus male mice and rats. Following platelet-activating factor-induced shock, MK886 increased survival exclusively in female mice, and this effect was abolished by testosterone administration. FLAP inhibitors and the novel-type 5-LO inhibitors licofelone and sulindac sulfide exhibited higher potencies in human blood from females, and bioactive 5-LO/FLAP complexes were formed in female, but not male, human and murine leukocytes. Supplementation of female blood or leukocytes with 5α-dihydrotestosterone abolished the observed sex differences. Our data suggest that females may benefit from anti-LT therapy to a greater extent than males, prompting consideration of sex issues in LT modifier development.

A New Therapy for Human Endometriosis: The Therapeutic Value of Leukotriene Receptor Antagonist for Endometriosis

Some drugs that regulate estrogen are currently used as therapy for endometriosis. However, these medical treatments have significant side effects and patients who hope to become pregnant cannot overcome infertility. To compare morphological alterations and clinical symptoms, revised American Fertility Society (r-AFS) scores were compared between patients with and without leukotriene receptor antagonist (LTR-A) treatment. LTR-A-treated cases showed significantly decreased r-AFS score. Furthermore, a significant correlation was seen between r-AFS score and LTR-A treatment period. In treated cases, clinical symptoms decreased and some patients achieved pregnancy. Morphologically, lesions in LTR-A-treated cases showed apoptotic fibroblasts and degeneration of collagen fibers. Our findings revealed that LTR-As had significant therapeutic value for the treatment of human endometriosis. Anti-LT therapy appears efficacious not only in the treatment of clinical symptoms and lesions, but also in improving fertility.

Recent Advances in the Search for Novel 5‐Lipoxygenase Inhibitors

5-Lipoxygenase (5-LO) is an important enzyme of the arachidonic acid cascade and catalyses with the help of FLAP, the 5-LO-activating protein, the formation of bioactive leukotrienes (LTs). LTs are inflammatory mediators playing a pathophysiological role in different diseases such as asthma, allergic rhinitis as well as cardiovascular diseases and certain types of cancer. Up to now, only one 5-LO inhibitor is on the market, zileuton for the treatment of asthma. With the rising number of indications for anti-LT therapy, 5-LO inhibitor drug development becomes more and more important. This MiniReview gives an update on 5-LO inhibitors currently under clinical development. Furthermore, the recent advances in the search for novel 5-lipoxygenase inhibitors with a focus on computational methods are summarized. Currently, licofelone is the compound with the highest clinical development status (completed phase III trials). 5-LO inhibitor screening programmes based on computational methods could deliver several promising drug-like new molecules. These activities can be expected to be driven by the newly resolved structure of human 5-LO in the future, enabling structure-based drug design. For the prospective drugs in late-stage clinical development, the future will show their clinical safety and efficacy in the particular diseases.

On the inhibition of 5‐lipoxygenase product formation by tryptanthrin: mechanistic studies and efficacy in vivo

Leukotrienes (LTs) are pro-inflammatory mediators produced by 5-lipoxygenase (5-LO). Currently available 5-LO inhibitors either lack efficacy or are toxic and novel approaches are required to establish a successful anti-LT therapy. Here we provide a detailed evaluation of the effectiveness of the plant-derived alkaloid tryptanthrin as an inhibitor of LT biosynthesis. We analysed LT formation and performed mechanistic studies in human neutrophils stimulated with pathophysiologically relevant stimuli (LPS and formyl peptide), as well as in cell-free assays (neutrophil homogenates or recombinant human 5-LO) and in human whole blood. The in vivo effectiveness of tryptanthrin was evaluated in the rat model of carrageenan-induced pleurisy. Tryptanthrin potently reduced LT-formation in human neutrophils (IC(50) = 0.6µM). However, tryptanthrin is not a redox-active compound and did not directly interfere with 5-LO activity in cell-free assays. Similarly, tryptanthrin did not inhibit the release of arachidonic acid, the activation of MAPKs, or the increase in [Ca(2+) ](i) , but it modified the subcellular localization of 5-LO. Moreover, tryptanthrin potently suppressed LT formation in human whole blood (IC(50) = 10µM) and reduced LTB(4) levels in the rat pleurisy model after a single oral dose of 10mg·kg(-1) . Our data reveal that tryptanthrin is a potent natural inhibitor of cellular LT biosynthesis with proven efficacy in whole blood and is effective in vivo after oral administration. Its unique pharmacological profile supports further analysis to exploit its pharmacological potential.

5-Lipoxygenase inhibitors: a review of recent developments and patents

Importance to the field: Leukotrienes (LTs) are pivotal lipid mediators of inflammation and allergy and results from recent studies also suggest roles of LTs in cardiovascular diseases, cancer and osteoporosis. 5-Lipoxygenase (5-LO) catalyzes the first step in the biosynthesis of LTs from arachidonic acid, and based on the multiple potent pathophysiological actions of LTs, the pharmacological intervention with 5-LO is a challenge in the development of therapeutics.Areas covered in this review: We first summarize the biochemical regulation of 5-LO and the general pharmacological concepts in 5-LO inhibition by currently available compounds, and subsequently we report recent developments deduced from recent scientific publications and patents.What the reader will gain: A comprehensive overview about the different molecular pharmacological strategies to inhibit 5-LO and the most successful previous 5-LO inhibitors. The review also gives insights into novel concepts, for example, dual prostaglandin/LT synthesis inhibition and reveals novel compounds patented or developed within the past 5 years.Take home message: Despite the increasing therapeutic indications of anti-LT therapy, the progress in the development of novel 5-LO inhibitors is moderate. However, novel molecular concepts in the intervention with LT biosynthesis seem promising.

Regulation of leukotrienes in the management of asthma: biology and clinical therapy.

Leukotrienes (LTs) are the ultimate synthetic product resulting from the intracellular hydrolysis of membrane phospholipid at the nuclear envelope in inflammatory cells. Activated cytosolic phospholipase (cPLA2) catalyzes the production of arachidonic acid, which is converted by cyclooxygenases into leukotriene A4 (LTA4) and subsequently into the chemotaxin LTB4, which has no direct bronchoconstrictor activity. In certain inflammatory cells, LTA4 is converted into the cysteinyl leukotriene (cysLT) LTC4, which is converted into LTD4 and finally to LTE4 after extracellular transport. All cysLTs occupy the same receptors and are extremely potent bronchoconstricting agents that are pathogenetic in both asthma and allergy. With the identification of the structure of the cysLT receptor, antileukotriene therapies have been developed that either (a) inhibit synthesis of leukotriene (through 5-lipoxygenase inhibition) or (b) block the cysLT receptor. Preliminary investigations indicate that corticosteroids also may partially block the synthesis of cysLT and that cysLTs may be chemotactic for other inflammatory cells, e.g. eosinophils, by a mechanism that has not yet been defined. Currently, anti-LT therapies are approved by the US Food and Drug Administration (FDA) only for patients with asthma. These drugs generally are moderately efficacious agents, although they are highly efficacious in aspirin-induced asthma (AIA). In other forms of asthma, inhaled corticosteroid (ICS) therapy has been more effective than anti-LT therapy in improving air flow obstruction. However, anti-LT agents are additive to beta-adrenoceptor and ICS in their effects. Accordingly, anti-LT therapies are used frequently as supplemental treatments in asthmatic patients whose asthma is not optimally controlled by a combination of other drugs, including long-acting beta-adrenoceptor drugs and ICS agents. The growth of leukotriene receptor antagonists (LTRAs) has been extraordinary in the United States. The exceptional safety of these agents and their ease of administration as tablets taken once or twice daily has spurred this growth. In the past year, the high-affinity cysLT receptor has been cloned. This holds forth the promise of a second generation of LTRA agents of even greater efficacy and possibly greater duration of action.

Design of inhibitors of leukotriene biosynthesis and their therapeutic potential

Abstract