Leukotriene A4 Hydrolase Inhibitors Research Articles

Application of Ensemble Machine Learning Methods for QSAR Classification of Leukotriene A4 Hydrolase Inhibitors in Drug Discovery

Inflammatory diseases such as asthma, rheumatoid arthritis, and cardiovascular conditions are driven by overproduction of leukotriene B4 (LTB4), a potent inflammatory mediator. Leukotriene A4 hydrolase (LTA4H) plays a critical role in converting leukotriene A4 into LTB4, making it a prime target for drug discovery. Despite ongoing efforts, developing effective LTA4H inhibitors has been challenging due to the complex binding properties of the enzyme and the structural diversity of potential inhibitors. Traditional drug discovery methods, like high-throughput screening (HTS), are often time-consuming and inefficient, prompting the need for more advanced approaches. Quantitative Structure-Activity Relationship (QSAR) modeling, enhanced by ensemble machine learning techniques, provides a promising solution by enabling accurate prediction of compound bioactivity based on molecular descriptors. In this study, six ensemble machine learning methods—AdaBoost, Extra Trees, Gradient Boosting, LightGBM, Random Forest, and XGBoost—were employed to classify LTA4H inhibitors. The dataset, comprising 636 compounds labeled as active or inactive based on pIC50 values, was processed to extract 450 molecular descriptors after feature engineering. The results show that the LightGBM model achieved the highest classification accuracy (83.59%) and Area Under the Curve (AUC) value (0.901), outperforming other models. XGBoost and Random Forest also demonstrated strong performance, with AUC values of 0.890 and 0.895, respectively. The high sensitivity (95.24%) of the XGBoost model highlights its ability to accurately identify active compounds, though it exhibited slightly lower specificity (61.36%), indicating a higher false-positive rate. These findings suggest that ensemble machine learning models, particularly LightGBM, are highly effective in predicting bioactivity, offering valuable tools for early-stage drug discovery. The results indicate that ensemble methods significantly enhance QSAR model accuracy, making them viable for identifying promising LTA4H inhibitors, potentially accelerating the development of anti-inflammatory therapies.

Structure-Guided Elaboration of a Fragment-Like Hit into an Orally Efficacious Leukotriene A4 Hydrolase Inhibitor.

Leukotriene A4 hydrolase (LTA4H) is the final and rate-limiting enzyme in the biosynthesis of pro-inflammatory leukotriene B4 (LTB4). Preclinical studies have provided strong evidence that LTA4H is an attractive drug target for the treatment of chronic inflammatory diseases. Here, we describe the transformation of compound 2, a fragment-like hit, into the potent inhibitor of LTA4H 3. Our strategy involved two key steps. First, we aimed to increase the polarity of fragment 2 to improve its drug-likeness, particularly its solubility, while preserving both its promising potency and low molecular weight. Second, we utilized structural information and incorporated a basic amino function, which allowed for the formation of an essential hydrogen bond with Q136 of LTA4H and consequently enhanced the potency. Compound 3 exhibited exceptional selectivity and showed oral efficacy in a KRN passive serum-induced arthritis model in mice. The anticipated human dose to achieve 90% target engagement at the trough concentration was determined to be 40 mg administered once daily.

Discovery of Amino Alcohols as Highly Potent, Selective, and Orally Efficacious Inhibitors of Leukotriene A4 Hydrolase.

The discovery of chiral amino alcohols derived from our previously disclosed clinical LTA4H inhibitor LYS006 is described. In a biochemical assay, their optical antipodes showed similar potencies, which could be rationalized by the cocrystal structures of these compounds bound to LTA4H. Despite comparable stabilities in liver microsomes, they showed distinct in vivo PK properties. Selective O-phosphorylation of the (R)-enantiomers in blood led to clearance values above the hepatic blood flow, whereas the (S)-enantiomers were unaffected and exhibited satisfactory metabolic stabilities in vivo. Introduction of two pyrazole rings led to compound (S)-2 with a more balanced distribution of polarity across the molecule, exhibiting high selectivity and excellent potency in vitro and in vivo. Furthermore, compound (S)-2 showed favorable profiles in 16-week IND-enabling toxicology studies in dogs and rats. Based on allometric scaling and potency in whole blood, compound (S)-2 has the potential for a low oral efficacious dose administered once daily.

Lipoxin receptor agonist and inhibition of LTA4 hydrolase prevent tight junction disruption caused by P. aeruginosa filtrate in airway epithelial cells.

Airway diseases can disrupt tight junction proteins, compromising the epithelial barrier and making it more permeable to pathogens. In people with pulmonary disease who are prone to infection with Pseudomonas aeruginosa, pro-inflammatory leukotrienes are increased and anti-inflammatory lipoxins are decreased. Upregulation of lipoxins is effective in counteracting inflammation and infection. However, whether combining a lipoxin receptor agonist with a specific leukotriene A4 hydrolase (LTA4H) inhibitor could enhance these protective effects has not to our knowledge been investigated. Therefore, we explored the effect of lipoxin receptor agonist BML-111 and JNJ26993135 a specific LTA4H inhibitor that prevents the production of pro-inflammatory LTB4 on tight junction proteins disrupted by P. aeruginosa filtrate (PAF) in human airway epithelial cell lines H441 and 16HBE-14o. Pre-treatment with BML-111 prevented an increase in epithelial permeability induced by PAF and conserved ZO-1 and claudin-1 at the cell junctions. JNJ26993135 similarly prevented the increased permeability induced by PAF, restored ZO-1 and E-cadherin and reduced IL-8 but not IL-6. Cells pre-treated with BML-111 plus JNJ26993135 restored TEER and permeability, ZO-1 and claudin-1 to the cell junctions. Taken together, these data indicate that the combination of a lipoxin receptor agonist with a LTA4H inhibitor could provide a more potent therapy.

A general organophotoredox strategy to difluoroalkyl bicyclo-alkane (CF2-BCA) hybrid bioisosteres.

Here, we report a general approach to the synthesis of the difluoroalkyl bicycloalcanes (CF2-BCAs), as structural surrogates of aryl ketones and ethers. The chemistry is driven by a dihydrobenzoacridine photocatalyst, that engages in a catalytic electron-donor acceptor (EDA) complex, or directly single-electron reduce the fluorinated substrate. These two convergent manifolds lead to the generation of the R-CF2 radical, that reacts with the [1.1.1]- or [3.1.1.]-propellane. The method is extremely general, and extendable to complex bioactive molecules (30 examples, up to 87% yield). The structural features of the CF2-BCP hybrid bioisostere were investigated by single crystal X-ray. Finally, we synthesised a CF2-BCP analogue of a Leukotriene A4 hydrolase inhibitor, replacing the original aryl ether motif. In-silico docking studies indicated that this new analogue maintains the same arrangement within the enzyme pocket, profiling the use of the CF2-BCA hybrid bioisostere in medicinal chemistry settings.

A General Organophotoredox Strategy to Difluoroalkyl Bicycloalkane (CF2‐BCA) Hybrid Bioisosteres**

AbstractHere, we report a general approach to the synthesis of the difluoroalkyl bicycloalkanes (CF2‐BCAs), as structural surrogates of aryl ketones and ethers. The chemistry is driven by a dihydrobenzoacridine photocatalyst, that engages in a catalytic electron‐donor acceptor (EDA) complex, or directly reduces the fluorinated substrate. These two convergent manifolds lead to the generation of the R‐CF2 radical, that reacts with the [1.1.1]‐ or [3.1.1.]‐propellane. The method is extremely general, and extendable to complex bioactive molecules (30 examples, up to 87 % yield). The structural features of the CF2‐BCP hybrid bioisostere were investigated by single crystal X‐ray. Finally, we synthesised a CF2‐BCP analogue of a Leukotriene A4 hydrolase inhibitor, replacing the original aryl ether motif. In silico docking studies indicated that this new analogue maintains the same arrangement within the enzyme pocket, profiling the use of the CF2‐BCA hybrid bioisostere in medicinal chemistry settings.

Modulation of the 5-Lipoxygenase Pathway by Chalcogen-Containing Inhibitors of Leukotriene A4 Hydrolase.

The 5-lipoxygenase (5-LOX) pathway gives rise to bioactive inflammatory lipid mediators, such as leukotrienes (LTs). 5-LOX carries out the oxygenation of arachidonic acid to the 5-hydroperoxy derivative and then to the leukotriene A4 epoxide which is converted to a chemotactic leukotriene B4 (LTB4) by leukotriene A4 hydrolase (LTA4H). In addition, LTA4H possesses aminopeptidase activity to cleave the N-terminal proline of a pro-inflammatory tripeptide, prolyl-glycyl-proline (PGP). Based on the structural characteristics of LTA4H, it is possible to selectively inhibit the epoxide hydrolase activity while sparing the inactivating, peptidolytic, cleavage of PGP. In the current study, chalcogen-containing compounds, 4-(4-benzylphenyl) thiazol-2-amine (ARM1) and its selenazole (TTSe) and oxazole (TTO) derivatives were characterized regarding their inhibitory and binding properties. All three compounds selectively inhibit the epoxide hydrolase activity of LTA4H at low micromolar concentrations, while sparing the aminopeptidase activity. These inhibitors also block the 5-LOX activity in leukocytes and have distinct inhibition constants with recombinant 5-LOX. Furthermore, high-resolution structures of LTA4H with inhibitors were determined and potential binding sites to 5-LOX were proposed. In conclusion, we present chalcogen-containing inhibitors which differentially target essential steps in the biosynthetic route for LTB4 and can potentially be used as modulators of inflammatory response by the 5-LOX pathway.

Multi-walled carbon nanotubes induce arachidonate 5-lipoxygenase expression and enhance the polarization and function of M1 macrophages in vitro

Fibrogenic carbon nanotubes (CNTs) induce the polarization of M1 and M2 macrophages in mouse lungs. Polarization of the macrophages regulates the production of proinflammatory and pro-resolving lipid mediators (LMs) to mediate acute inflammation and its resolution in a time-dependent manner. Here we examined the molecular mechanism by which multi-walled CNTs (MWCNTs, Mitsui-7) induce M1 polarization in vitro. Treatment of murine macrophages (J774A.1) with Mitsui-7 MWCNTs increased the expression of Alox5 mRNA and protein in a concentration- and time-dependent manner. The MWCNTs induced the expression of CD68 and that induction persisted for up to 3 days post-exposure. The expression and activity of inducible nitric oxide synthase, an intracellular marker of M1, were increased by MWCNTs. Consistent with M1 polarization, the MWCNTs induced the production and secretion of proinflammatory cytokines tumor necrosis factor-α and interleukin-1β, and proinflammatory LMs leukotriene B4 (LTB4) and prostaglandin E2 (PGE2). The cell-free media from MWCNT-polarized macrophages induced the migration of neutrophilic cells (differentiated from HL-60), which was blocked by Acebilustat, a specific leukotriene A4 hydrolase inhibitor, or LY239111, an LTB4 receptor antagonist, but not NS-398, a cyclooxygenase 2 inhibitor, revealing LTB4 as a major mediator of neutrophil chemotaxis from MWCNT-polarized macrophages. Knockdown of Alox5 using specific small hairpin-RNA suppressed MWCNT-induced M1 polarization, LTB4 secretion, and migration of neutrophils. Taken together, these findings demonstrate the polarization of M1 macrophages by Mitsui-7 MWCNTs in vitro and that induction of Alox5 is an important mechanism by which the MWCNTs promote proinflammatory responses by boosting M1 polarization and production of proinflammatory LMs.

Design of benzimidazoles, benzoxazoles, benzothiazoles and thiazolopyridines as leukotriene A4 hydrolase inhibitors through 3D-QSAR, docking and molecular dynamics

Human leukotriene A4 hydrolase enzyme (LTA4H) catalyses the biotransformation of the inactive precursor leukotriene A4 (LTA4) to the bioactive Leukotriene B4 (LTB4), which causes many inflammatory responses in the human body. Therefore, the selective inhibition of this enzyme becomes a useful strategy for the treatment of several illnesses such as asthma, allergic rhinitis, cardiovascular diseases, and cancer. Herein we report a 3D-QSAR/ /CoMFA and CoMSIA study on a series of 47 benzimidazoles, benzoxazoles, benzothiazoles and thiazolopyridines reported as potent LTA4H inhibitors. Good statistical parameters were obtained for the best model (q2 = 0.568, r2 ncv = 0.891 and r2 test = 0.851). A new series of 10 compounds capable of inhibiting leukotriene A4 hydrolase with high potency was presented. All designed inhibitors showed low IC50 in nano- and sub-nanomolar ranges, when they were evaluated in 3D-QSAR models. Subsequently, the designed molecules, as well as the least and most active compounds were subjected to docking and molecular dynamics studies into LTA4H. In conclusion, we summarised a thorough structure?activity relationship (SAR) of LTA4H inhibitors of heterocyclic structure. These models can be used for the rational proposal of new inhibitors.

Differential Multimolecule Fingerprint for Similarity Search─Making Use of Active and Inactive Compound Sets in Virtual Screening.

In conventional fingerprint methods, the similarity between two molecules is calculated using the Tanimoto index as a numerical criterion. Thus, the query molecules in virtual screening should be most representative of the wanted compound class at hand. In the concept introduced here, all available active molecules form a multimolecule fingerprint in which the appearing features are weighted according to their respective frequency. The features of inactive molecules are treated likewise and the resulting values are subtracted from those of the active ones. The obtained differential multimolecule fingerprint (DMMFP) is thus specific for the respective class of compounds. To account for the noninteger representation within this fingerprint, a modified Sørensen-Dice coefficient is used to compute the similarity. Potentially active molecules yield positive scores, whereas presumably inactive ones are denoted by negative values. The concept was applied to Angiotensin-converting enzyme (ACE) inhibitors, β2-adrenoceptor ligands, leukotriene A4 hydrolase inhibitors, dopamine D3 antagonists, and cytochrome CYP2C9 substrates, for which experimental binding affinities are known and was tested against decoys from DUD-E and a further background database consisting of molecules from the dark chemical matter, which comprises compounds that appear as frequent hitters across multiple assays. Using the 166 publicly available keys of the MACCS fingerprint and the larger PubChem fingerprint, actives were recovered with very high sensitivity. Furthermore, three marketed ACE inhibitors as well as the carbonic anhydrase II inhibitor dorzolamide were detected in the dark chemical matter data set. For comparison, the DMMFP was also used with a Bayesian classifier, for which the specificity (correctly classified inactives) and likewise the accuracy was superior. Conversely, the similarity score produced by the Sørensen-Dice coefficient showed its potential for the early recognition of (potentially) active molecules.

An inhibitor of leukotriene-A4 hydrolase from bat salivary glands facilitates virus infection

SignificanceAn immunosuppressant protein (MTX), which facilitates virus infection by inhibiting leukotriene A4 hydrolase (LTA4H) to produce the lipid chemoattractant leukotriene B4 (LTB4), was identified and characterized from the submandibular salivary glands of the bat Myotis pilosus. To the best of our knowledge, this is a report of an endogenous LTA4H inhibitor in animals. MTX was highly concentrated in the bat salivary glands, suggesting a mechanism for the generation of immunological privilege and immune tolerance and providing evidence of viral shedding through oral secretions. Moreover, given that the immunosuppressant MTX selectively inhibited the proinflammatory activity of LTA4H, without affecting its antiinflammatory activity, MTX might be a potential candidate for the development of antiinflammatory drugs by targeting the LTA4-LTA4H-LTB4 inflammatory axis.

Empire-CF study: A phase 2 clinical trial of leukotriene A4 hydrolase inhibitor acebilustat in adult subjects with cystic fibrosis

BackgroundCystic fibrosis (CF) is characterized by neutrophilic inflammation in the airways. Leukotriene B4 (LTB4) is a neutrophil chemoattractant and has been implicated in CF pathogenesis. Acebilustat, a novel, synthetic, small-molecule leukotriene A4 hydrolase inhibitor, reduces LTB4 production. We report findings from a randomized placebo-controlled trial of acebilustat in adult subjects with mild-to-moderate lung disease. MethodsSubjects were randomized (1:1:1) to once-daily acebilustat 50 mg, 100 mg or placebo for 48 weeks, concomitantly with their current therapeutic regimen. Subjects were stratified by use of concomitant CF transmembrane conductance regulator (CFTR) modulators, baseline percent predicted forced expiratory volume in 1 second (ppFEV1) 50-75 and >75, and number of pulmonary exacerbations in the past year (1 or >1). Primary endpoints were the change from baseline in ppFEV1 and safety. Secondary endpoints included the rate of pulmonary exacerbations. ResultsOverall, 199 subjects were randomized and dosed (acebilustat 50 mg, n=67; acebilustat 100 mg, n=66; placebo, n=66). Baseline demographics and disease profile were well balanced among treatment groups. Acebilustat had no statistically significant effect on the primary endpoint of change in ppFEV1 at week 48 or the secondary endpoint pulmonary exacerbations. There was a trend towards reduced pulmonary exacerbations in subjects receiving acebilustat in pre-specified populations with ppFEV1>75 (35% rate reduction) and those on concomitant CFTR modulator therapy (20% rate reduction). Acebilustat was well tolerated. ConclusionsAcebilustat did not improve lung function. A trend towards reduced pulmonary exacerbations in subjects with an earlier stage of lung disease suggests a potential effect in this population.

Drug discovery strategies for novel leukotriene A4 hydrolase inhibitors

ABSTRACT Introduction Leukotriene A4 hydrolase (LTA4H) is the final and rate limiting enzyme regulating the biosynthesis of leukotriene B4 (LTB4), a pro-inflammatory lipid mediator implicated in a large number of inflammatory pathologies. Inhibition of LTA4H not only prevents LTB4 biosynthesis but also induces a lipid mediator class-switch within the 5-lipoxygenase pathway, elevating biosynthesis of the anti-inflammatory lipid mediator Lipoxin A4. Ample preclinical evidence advocates LTA4H as attractive drug target for the treatment of chronic inflammatory diseases. Areas covered This review covers details about the biochemistry of LTA4H and describes its role in regulating pro- and anti-inflammatory mediator generation. It summarizes recent efforts in medicinal chemistry toward novel LTA4H inhibitors, recent clinical trials testing LTA4H inhibitors in pulmonary inflammatory diseases, and potential reasons for the discontinuation of former development programs. Expert opinion Given the prominent role of LTB4 in initiating and perpetuating inflammation, LTA4H remains an appealing drug target. The reason former attempts targeting this enzyme have not met with success in the clinic can be attributed to compound-specific liabilities of first-generation inhibitors and/or choice of target indications to test this mode of action. A new generation of highly potent and selective LTA4H inhibitors is currently undergoing clinical testing in indications with a strong link to LTB4 biology.

Bestatin Cream Impairs Solar Simulated Light‒Driven Skin Inflammation and Skin Carcinogenesis in Mice

Leukotriene A4 hydrolase (LTA4H) is an enzyme that catalyzes the production of the inflammatory mediator leukotriene B4, which is involved in inflammatory responses mediated through the leukotriene B4/leukotriene B4 receptor type 1 (BLT1) signaling pathway. In this study, we investigated whether bestatin, an LTA4H inhibitor, could suppress skin acute inflammation and carcinogenesis. In the clinical sample, BLT1 was significantly induced in human skin tissues after acute solar simulated light (SSL) exposure. BLT1 and NF-κB p65 expressions were also increased in acute SSL‒induced mouse skin tissue. Furthermore, LTA4H and BLT1 were highly expressed in skin chronic inflammation and squamous cell carcinomas. More importantly, topical administration of bestatin cream dramatically inhibited BLT1 expression in acute SSL‒induced human skin tissues. BLT1 and NF-κB p65 expressions were also suppressed in acute SSL‒induced Lta4h-knockout and bestatin-treated mice skin tissues. Moreover, we conducted long-term prevention and therapeutic studies, which showed that bestatin significantly attenuated SSL-induced skin carcinogenesis. Mechanistic studies showed that bestatin inhibited skin carcinogenesis by suppressing cell proliferation and inducing cell apoptosis through LTA4H‒BLT1‒protein kinase B‒NF-κB p65 pathway. Overall, our results suggest that topical application of novel cream containing bestatin might open a helpful avenue for SSL-induced skin carcinogenesis.

Classification and QSAR models of leukotriene A4 hydrolase (LTA4H) inhibitors by machine learning methods

ABSTRACT Leukotriene A4 hydrolase (LTA4H) is an important anti-inflammatory target which can convert leukotriene A4 (LTA4) into pro-inflammatory substance leukotriene B4 (LTB4). In this paper, we built 18 classification models for 463 LTA4H inhibitors by using support vector machine (SVM), random forest (RF) and K-Nearest Neighbour (KNN). The best classification model (Model 2A) was built from RF and MACCS fingerprints. The prediction accuracy of 88.96% and the Matthews correlation coefficient (MCC) of 0.74 had been achieved on the test set. We also divided the 463 LTA4H inhibitors into six subsets using K-Means. We found that the highly active LTA4H inhibitors mostly contained diphenylmethane or diphenyl ether as the scaffold and pyridine or piperidine as the side chain. In addition, six quantitative structure–activity relationship (QSAR) models for 172 LTA4H inhibitors were built by multiple linear regression (MLR) and SVM. The best QSAR model (Model 6A) was built by using SVM and CORINA Symphony descriptors. The coefficients of determination of the training set and the test set were equal to 0.81 and 0.79, respectively. Classification and QSAR models could be used for subsequent virtual screening, and the obtained fragments that were important for highly active inhibitors would be helpful for designing new LTA4H inhibitors.

Discovery of LYS006, an Inhibitor of Leukotriene A4 Hydrolase for the Treatment of Inflammatory Diseases

Discovery of LYS006, an Inhibitor of Leukotriene A4 Hydrolase for the Treatment of Inflammatory Diseases

Discovery of LYS006, a Potent and Highly Selective Inhibitor of Leukotriene A4 Hydrolase.

The cytosolic metalloenzyme leukotriene A4 hydrolase (LTA4H) is the final and rate-limiting enzyme in the biosynthesis of pro-inflammatory leukotriene B4 (LTB4). Preclinical studies have validated this enzyme as an attractive drug target in chronic inflammatory diseases. Despite several attempts, no LTA4H inhibitor has reached the market, yet. Herein, we disclose the discovery and preclinical profile of LYS006, a highly potent and selective LTA4H inhibitor. A focused fragment screen identified hits that could be cocrystallized with LTA4H and inspired a fragment merging. Further optimization led to chiral amino acids and ultimately to LYS006, a picomolar LTA4H inhibitor with exquisite whole blood potency and long-lasting pharmacodynamic effects. Due to its high selectivity and its ability to fully suppress LTB4 generation at low exposures in vivo, LYS006 has the potential for a best-in-class LTA4H inhibitor and is currently investigated in phase II clinical trials in inflammatory acne, hidradenitis suppurativa, ulcerative colitis, and NASH.

Pathogenic role leukotriene B4 in lung injury induced by lung-protective mechanical ventilation in rabbits

To elucidate the pathogenic role of leukotriene B4 (LTB4) in pulmonary hyper-permeability and inflammation induced by lung-protective mechanical ventilation (LPMV) in rabbits. Thirty-two healthy Japanese white rabbits were randomized into 4 groups for treatment with vehicle or bestatin (a leukotriene A4 hydrolase inhibitor that inhibits LTB4 production) administered intragastrically at the daily dose of 8 mg/kg for 5 days, followed by sham operation (group S and group BS, respectively, in which the rabbits were anesthetized only) or LPMV (group PM and group BPM, respectively, in which the rabbits received ventilation with 50% oxygen at a tidal volume of 8 mL/kg for 5 h). The concentrations of LTB4 and cyclic adenosine monophosphate (cAMP) in the lung tissues were analyzed by ELISA. cAMP content, protein kinase A (PKA) protein expression and the Rap1-GTP protein to total Rap1 protein ratio were determined to assess the activities of cAMP/PKA and Rap1 signaling pathways. The lung injury was evaluated by assessing lung permeability index, lung wet/dry weight ratio, polymorphonuclear leukocyte (PMN) count in bronchoalveolar lavage fluid (BALF), pulmonary myeloperoxidase (MPO) activity and lung histological scores. None of the examined parameters differed significantly between group S and group BS. All the parameters with the exception of lung histological score increased significantly in group PM and group BPM as compared to those in group S (P < 0.05). Compared with those in PM group, the rabbits in group BPM showed significantly reduced LTB4 production in the lungs (P < 0.05), up-regulated cAMP/ PKA and Rap1 signaling pathway activities (P < 0.05), and alleviated lung hyper-permeability and inflammation (P < 0.05). LPMV can induce LTB4 overproduction to down-regulate cAMP/PKA and Rap1 signaling pathways in the lungs of rabbits, which results in lung hyper-permeability and inflammation. Bestatin can inhibit LTB4 production in the lungs to protect against LPMV-induced lung hyper-permeability and inflammation.

Abstract 16: LTA4 hydrolase inhibitor bestatin prevents intestinal tumors in APC mutant rodent models of FAP

Abstract Colorectal cancer (CRC) is the third most common cancer in the United States with 145,600 new cases and 51,020 deaths estimated to occur in 2019. Leukotriene B4 (LTB4), the product of the enzyme leukotriene A4 hydrolase (LTA4H), reportedly plays a role in carcinogenesis. LTA4H over expression and increased LTB4 levels are found in CRC tissues and correlate with both disease stage and reduced survival. Thus, we used a preclinical rodent model to assess repurposing bestatin (Ubenimex), a potent orally-active reversible small molecule inhibitor of LTA4H, for prevention of CRC in high-risk FAP patients. Six week old Apcmin/+ male and female mice (n≥15) were assigned to control and treatment groups; groups received the same diet either with 1000 ppm bestatin (treatment) or no bestatin (control) for 14 weeks at which point mice were euthanized and intestines were evaluated for tumors. Control mice developed colonic tumors with multiplicity of 1.35±0.16 (Mean±SEM) in males and 0.86±0.13 in females. Colonic tumor incidence was 91% and 73% in the male and female mice respectively. Additionally, control mice developed 30.52±1.66 (male) and 29.57±2.74 (female) small intestinal polyps (SIP). Dietary bestatin significantly reduced colon tumor multiplicity. Bestatin treated male mice had 55% fewer colonic tumors (0.60±0.21; p&amp;lt;0.01) and female mice 59% fewer (0.35±0.12; p&amp;lt;0.008) compared to their respective controls. Importantly colonic tumor incidence was inhibited by &amp;gt;50% in both genders. Bestatin administration was reduced colonic tumor incidence by 56% (p&amp;lt;0.001) in male and 52% (p&amp;lt;0.026) in female mice. Small intestinal polyps were also significantly reduced in treated mice compared to controls. Male mice developed 29% less SIP (21.67±2.32; p&amp;lt;0.006) while female had 46% fewer SIP (16.00±1.98; p&amp;lt;0.0005) compared to controls. The polyposis in rat coli (PIRC) model replicates CRC in FAP patients. PIRC rats (n=6) at 8 weeks of age were assessed for polyp number by colonoscopy, and assigned to control and bestatin (1000 ppm) groups for 8 weeks. Colonic polyp inhibition in each rat was evaluated by colonoscopy after treatment. Bestatin treatment led to strong suppression of colonic polyps; significantly fewer (~72% less; p&amp;lt;0.005) colonic polyps were seen in bestatin-treated PIRC rats. Pharmacokinetic analysis demonstrated that dietary bestatin resulted in significant bestatin levels in both serum (15μg/mL) and colonic tissue (up to 250 μg/g). LTB4 levels in both plasma and colon tumors were also significantly lowered by ~70% (p&amp;lt;0.004) and ~26% (p&amp;lt;0.01) respectively. Colonic tumors from the treated animals also showed an increase in NK and NKT cells suggesting immune-modulatory effects of the agent. In summary, bestatin demonstrated excellent safety, pharmacokinetics, and chemopreventive effects against CRC in preclinical models and warrants further validation clinically. Citation Format: Venkateshwar Madka, Gopal Pathuri, Hariprasad Gali, Nandini Kumar, Nagendra Sastri Yarla, Anh Bao, Adam S. Asch, Chinthalapally V. Rao. LTA4 hydrolase inhibitor bestatin prevents intestinal tumors in APC mutant rodent models of FAP [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 16.

Design and synthesis of Leukotriene A4 hydrolase inhibitors to alleviate idiopathic pulmonary fibrosis and acute lung injury

Idiopathic pulmonary fibrosis (IPF) and acute lung injury (ALI) are considered two severe public health issues, attributed to malfunctions of neutrophils. They can cause chronic inflammation and have association with subsequent tissue damages. There have been rare drugs applying to the efficient treatment in clinical practice. Existing research revealed that Leukotriene B4 (LTB4) is the critical endogenous molecule to induce neutrophil inflammatory response. LTB4 blocking biosynthesis is the potential strategy treating IPF and ALI. In the present study, 45 hydroxamic acid derivatives were produced, and compound 26 was screened out as a highly selective Lead compound of Leukotriene A4 Hydrolase (LTA4H), i.e., an enzyme critical to the biosynthesis of LTB4. This compound is capable of relieving neutrophilic inflammation in an IPF mouse model at early stage, as well as mitigating LPS-induced acute lung injury via a mechanism of LTB4 blocking biosynthesis in vivo. Whether this compound acts as the potential lead compound for the treatment of IPF and ALI requires further verification.