5-lipoxygenase (5-LO)

As the duration of incubation increases, IL-2 levels in zileuton-treated and untreated anti-CD3 cells drop. Zileuton probably lowers IL-2 levels by blocking 5-lipoxygenase, which in turn causes the synthesis of leukotriene B4, an IL-2 inducer[2].

The group exhibits a considerably reduced level of NF-κB staining, and zileuton (5 mg/kg, po) treated I/R rats show that zileuton's impact to reduce NF-κB expression does not change significantly in the presence of COX inhibitors. When administered intraperitoneally (5 mg/kg), zileuton dramatically reduces the apoptotic index in I/R rats. With regard to the elevated serum TNF-α levels in the I/R group, zileuton shows no discernible effect[1]. Zileuton (1,200 mg/kg) prevents the colon and small intestine of APCΔ468 from forming polyps. Treatment with zileuton decreases the rates of non-epithelial cell proliferation in polyps and raises the rates of apoptosis in rat polyps. Both in the colon and small intestine, the number of apoptotic cells in Zileuton-treated cells has significantly increased. In Zileuton-fed APCΔ468 mice, polyposis may be greatly reduced in the small intestine and colon due to the reduced proliferation rate[3].

---

Left ventricle MDA in I/R group was higher compared to sham group; however, it did not show significant change with zileuton. Although tissue injury in I/R group was less severe in all treatment groups, it was not statistically significant. NF-κB H-score and apoptotic index, which were higher in I/R group compared to sham I/R, were decreased with application of zileuton (H-score: p<0.01; apoptotic index: p<0.001). Zileuton had no significant effect on increased serum TNF-α levels in I/R group. Conclusion: 5-LOX inhibition in rat myocardial infarction model attenuated increased left ventricle NF-κB expression and apoptosis and these actions were not modulated by COX inhibitors.[1]

---

Zileuton-fed mice developed fewer polyps and displayed marked reduction in systemic and polyp-associated inflammation. Pro-inflammatory cytokines and pro-inflammatory innate and adaptive immunity cells were reduced both in the lesions and systemically. As part of tumor-associated inflammation Leukotriene B4 (LTB4), product of 5-LO activity, is increased focally in human dysplastic lesions. The 5-LO enzymatic activity was reduced in the serum of Zileuton treated polyposis mice. Conclusions: This study demonstrates that dietary administration of 5-LO specific inhibitor in the polyposis mouse model decreases polyp burden, and suggests that Zileuton may be a potential chemo-preventive agent in patients that are high-risk of developing colon cancer[3].

Spleen cells obtained from 11 4-month-old C57BL/6 female mice were incubated without and with 10 μg/mL HU or zileuton, 2.5 μg/mL concanavalin A (ConA), 20 μg/mL phytohemagglutinin (PHA), and 50 ng/mL anti-CD3 antibody for 12-48 h. IL-2 was measured in the supernatant by enzyme-linked immunosorbent assay and cell proliferation by (3)H-thymidine uptake[2].
Results: While HU reduced lymphocyte proliferation in response to mitogens (P<0.05), zileuton did not. Baseline IL-2 concentration and PHA-induced IL-2 were not significantly affected by either drug. Contrary to what we expected, while HU increased IL-2 supernatant levels 1.17-fold to 6.5-fold in anti-CD3 antibody-treated cells (P<0.05), zileuton decreased them 35%-65% (P<0.05). Zileuton likely reduced IL-2 levels by inhibiting 5-lipoxygenase, hence leukotriene B4 production, an IL-2 inducer. HU did not decrease IL-2 secretion likely because of its lack of effect on mRNA and protein synthesis[2].
Conclusion: Modulation of IL-2 secretion by zileuton and/or reduced lymphocyte proliferation by HU may impair the immune response of patients with sickle cell disease but may also be beneficial by attenuating inflammation independently of fetal hemoglobin induction[2].

Male Wistar rats (200-250 g; n=12 per group) were used in the study. I/R was performed by occluding the left coronary artery for 30 minutes and 2 hours of reperfusion of the heart. Experimental groups were I/R group, sham I/R group, zileuton (5 mg/kg orally, twice daily)+I/R group, zileuton+indomethacin (5 mg/kg intraperitoneally)+I/R group, zileuton+ketorolac (10 mg/kg subcutaneously)+I/R group, and zileuton+nimesulide (5 mg/kg subcutaneously)+I/R group. Following I/R, blood samples were collected to measure tumor necrosis factor alpha (TNF-α), and left ventricles were excised for evaluation of microscopic damage; malondialdehyde (MDA), glutathione, nuclear factor (NF)-κB assays; and evaluation of apoptosis.[1]

---

In the current study, we inhibited 5-LO by dietary administration of Zileuton in the APCΔ468 mouse model of polyposis and analyzed the effect of in vivo 5-LO inhibition on tumor-associated and systemic inflammation.[3]

Absorption, Distribution and Excretion
Rapidly and almost completely absorbed. The absolute bioavailability is unknown.
Elimination of zileuton is predominantly via metabolism with a mean terminal half-life of 2.5 hours. The urinary excretion of the inactive N-dehydroxylated metabolite and unchanged zileuton each accounted for less than 0.5% of the dose.
1.2 L/kg
Apparent oral cl=7 mL/min/kg

---

Metabolism / Metabolites
Hepatic. Zileuton and its N-dehydroxylated metabolite are oxidatively metabolized by the cytochrome P450 isoenzymes 1A2, 2C9 and 3A4.
Zileuton has known human metabolites that include Zileuton O-glucuronide.

---

Biological Half-Life
2.5 hours

Hepatotoxicity
In premarketing studies, zileuton therapy was found to be associated with mild-to-moderate serum aminotransferase elevations. In large prospective studies, ALT elevations above 3 times the upper limit of the normal range occurred in 1.9% of patients treated with zileuton for at least one year, compared to 0.2% of placebo recipients. These elevations were usually transient, asymptomatic and rapidly reversible. However, some patients with ALT elevations reported symptoms suggestive of hepatic injury (fatigue, nausea, abdominal pain) and individual cases of clinically apparent, frank liver injury with jaundice were seen. The typical onset of liver enzyme elevations was within 4 to 8 weeks of starting zileuton, but cases arising after 6 months were also reported. In cases with jaundice, the pattern of serum enzyme elevations was hepatocellular. Immunoallergic and autoimmune features were not prominent. Recovery was rapid, usually within 1 to 2 months. Overall, however, only isolated cases of zileuton related liver injury with jaundice have been reported, and clinically apparent hepatotoxicity from it must be very rare. Results of rechallenge have not been reported. Because of the frequency of serum enzyme elevations during zileuton therapy, monitoring of serum aminotransferase levels is recommended and its use is considered contraindicated in patients with active liver disease. The lack of published reports of zileuton hepatotoxicity may be due to active monitoring for liver test abnormalities and prompt discontinuation if they persist or continue to rise. In addition, zileuton has not been as widely used clinically as montelukast or zafirlukast.
Likelihood score: D (possible rare cause of clinically apparent liver injury).

---

Effects During Pregnancy and Lactation
◉ Summary of Use during Lactation
No published information is available on the use of zileuton during breastfeeding; however, manufacturer's data indicate that the dose in milk is low. An expert guideline considers that leukotriene receptor antagonists can be used during breastfeeding.
◉ Effects in Breastfed Infants
Relevant published information was not found as of the revision date.
◉ Effects on Lactation and Breastmilk
Relevant published information was not found as of the revision date.

---

Protein Binding
93% bound to plasma proteins, primarily to albumin.

[1]. Inhibition of 5-lipoxygenase by zileuton in a rat model of myocardial infarction. Anatol J Cardiol. 2017 Apr;17(4):269-275.
[2]. Hydroxyurea and Zileuton Differentially Modulate Cell Proliferation and Interleukin-2 Secretion by Murine Spleen Cells: Possible Implication on the Immune Function and Risk of Pain Crisis in Patients with Sickle Cell Disease. Ochsner J. 2015 Fall;15(3):241-7.
[3]. Zileuton, 5-lipoxygenase inhibitor, acts as a chemopreventive agent in intestinal polyposis, by modulating polyp and systemic inflammation. PLoS One. 2015 Mar 6;10(3):e0121402.

Zileuton can cause cancer, developmental toxicity and female reproductive toxicity according to state or federal government labeling requirements.
Zileuton is a member of the class of 1-benzothiophenes that is 1-benzothiophene in which the hydrogen at position 2 is replaced by a 1-[carbamoyl(hydroxy)amino]ethyl group. A selective 5-lipoxygenase inhibitor, it inhibits the formation of leukotrienes LTB4, LTC4, LDT4, and LTE4. It is used for the management of chronic asthma. It has a role as an EC 1.13.11.34 (arachidonate 5-lipoxygenase) inhibitor, a non-steroidal anti-inflammatory drug, an anti-asthmatic drug, a leukotriene antagonist and a ferroptosis inhibitor. It is a member of ureas and a member of 1-benzothiophenes. It derives from a hydride of a 1-benzothiophene.
Leukotrienes are substances that induce numerous biological effects including augmentation of neutrophil and eosinophil migration, neutrophil and monocyte aggregation, leukocyte adhesion, increased capillary permeability, and smooth muscle contraction. These effects contribute to inflammation, edema, mucus secretion, and bronchoconstriction in the airways of asthmatic patients. Zileuton relieves such symptoms through its selective inhibition of 5-lipoxygenase, the enzyme that catalyzes the formation of leukotrienes from arachidonic acid. Specifically, it inhibits leukotriene LTB4, LTC4, LTD4, and LTE4 formation. Both the R(+) and S(-) enantiomers are pharmacologically active as 5-lipoxygenase inhibitors in in vitro systems. The immediate release tablet of Zileuton has been withdrawn from the US market.
Zileuton is a 5-Lipoxygenase Inhibitor. The mechanism of action of zileuton is as a 5-Lipoxygenase Inhibitor. The physiologic effect of zileuton is by means of Decreased Leukotriene Production.
Zileuton is an antiinflammatory leukotriene pathway inhibitor classified as an inhibitor of the enzyme 5-lipoxygenase that is used in the treatment of asthma and allergic rhinitis. Zileuton has been linked to rare cases of drug induced liver disease and is considered to be contraindicated in patients with active liver disease.
Zileuton is a synthetic derivative of hydroxyurea with antiasthmatic properties. The leukotriene inhibitor zileuton blocks 5-lipoxygenase, which catalyzes the formation of leukotrienes from arachidonic acid; causes bronchodilation; decreases bronchial mucous secretion and edema; and may prevent or decrease the symptoms of asthma. (NCI04)

---

Drug Indication
For the prophylaxis and chronic treatment of asthma in adults and children 12 years of age and older.
FDA Label

---

Mechanism of Action
Leukotrienes are substances that induce numerous biological effects including augmentation of neutrophil and eosinophil migration, neutrophil and monocyte aggregation, leukocyte adhesion, increased capillary permeability, and smooth muscle contraction. These effects contribute to inflammation, edema, mucus secretion, and bronchoconstriction in the airways of asthmatic patients. Zileuton relieves such symptoms through its selective inhibition of 5-lipoxygenase, the enzyme that catalyzes the formation of leukotrienes from arachidonic acid. Specifically, it inhibits leukotriene LTB4, LTC4, LTD4, and LTE4 formation. Both the R(+) and S(-) enantiomers are pharmacologically active as 5-lipoxygenase inhibitors in in vitro systems. Due to the role of leukotrienes in the pathogenesis of asthma, modulation of leukotriene formation by interruption of 5-lipoxygenase activity may reduce airway symptoms, decrease bronchial smooth muscle tone, and improve asthma control.

---

Pharmacodynamics
Zileuton is an asthma drug that differs chemically and pharmacologically from other antiasthmatic agents. It blocks leukotriene synthesis by inhibiting 5-lipoxygenase, an enzyme of the eicosanoid synthesis pathway. Current data indicates that asthma is a chronic inflammatory disorder of the airways involving the production and activity of several endogenous inflammatory mediators, including leukotrienes. Sulfido-peptide leukotrienes (LTC4, LTD4, LTE4, also known as the slow-releasing substances of anaphylaxis) and LTB4, a chemoattractant for neutrophils and eosinophils, are derived from the initial unstable product of arachidonic acid metabolism, leukotriene A4 (LTA4), and can be measured in a number of biological fluids including bronchoalveolar lavage fluid (BALF) from asthmatic patients. In humans, pretreatment with zileuton attenuated bronchoconstriction caused by cold air challenge in patients with asthma.

C11H12N2O2S

236.29

236.061

C, 55.92; H, 5.12; N, 11.86; O, 13.54; S, 13.57

111406-87-2

Zileuton sodium;118569-21-4;Zileuton-d4;1189878-76-9

60490

Typically exists as White to off-white solid at room temperature

1.4±0.1 g/cm3

449.4±47.0 °C at 760 mmHg

157-158°C

225.6±29.3 °C

0.0±1.2 mmHg at 25°C

1.704

3.74

2

3

2

16

275

0

S1C2=C([H])C([H])=C([H])C([H])=C2C([H])=C1C([H])(C([H])([H])[H])N(C(N([H])[H])=O)O[H]

MWLSOWXNZPKENC-UHFFFAOYSA-N

InChI=1S/C11H12N2O2S/c1-7(13(15)11(12)14)10-6-8-4-2-3-5-9(8)16-10/h2-7,15H,1H3,(H2,12,14)

1-(1-(benzo[b]thiophen-2-yl)ethyl)-1-hydroxyurea

A64077; A-64077; A64077; A 64077; Zyflo; Leutrol; 1-(1-(Benzo[b]thiophen-2-yl)ethyl)-1-hydroxyurea; Zyflo CR; Zileutonum; Zileutonum [INN-Latin]; trade name ZYFLO; ZYFLO CR.

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

Solubility in Formulation 1: ≥ 10 mg/mL (42.32 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 100.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

---

Solubility in Formulation 2: ≥ 10 mg/mL (42.32 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 100.0 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

---

View More

Solubility in Formulation 3: ≥ 10 mg/mL (42.32 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 100.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

---

 (Please use freshly prepared in vivo formulations for optimal results.)