Multitarget drugs: synthesis and preliminary pharmacological characterization of zileuton analogues endowed with Dual 5-LO inhibitor and NO-dependent activities.

The leukotrienes (LTs) are a family of lipid-derived autacoids that originate from arachidonic acid (AA). 5-Lipooxygenase (5LO) is the key enzyme in this process. It transforms AA through a two-step process, first into 5-hydroperoxyeicosatetraenoic acid (5-HPETE), and then into unstable leukotriene A4 (LTA4). This intermediate can be transformed either by leukotriene B4 synthase into leukotriene B4 (LTB4), or by leukotriene C4 synthase, which is a specific glutathione transferase, into peptide– lipid leukotrienes C4, D4, and E4 (LTC4, LTD4, LTE4). [1–3] LTs are involved in a variety of inflammatory and allergic disorders, particularly rheumatoid arthritis and inflammatory skin and bowel diseases. They also display potent bronchoconstrictor activity. Consequently, the treatment of allergic disorders and asthma are the classical indications for 5-LO inhibitors. 5] Novel and interesting potential indications are emerging for these products; for example, an increasing amount of experimental evidence shows an involvement of the 5-LO pathway in tumor cell proliferation. In particular, inhibition of 5-LO was found to induce apoptosis in various cancer cell types. The evidence that LTs are involved in atherogenesis and arterial wall remodeling sets the stage for new strategies in treating the development and progression of atherosclerosis. 7, 8] 5-LO inhibitors can be classified into four different classes according to their mechanism of action: redox-active compounds, competitive reversible inhibitors, inhibitors of 5-LO activating protein (FLAP), and iron-chelating inhibitors. Many substances that belong to these classes were developed as potent 5-LO inhibitors, including natural products. Among them, only ( )-[1-(1-benzo[b]thien-2-yl)ethyl]-1-hydroxyurea (1, zileuton), a hydroxyurea derivative of the iron-ligand-type inhibitor class, entered into the market in 1996 as an anti-asthmatic drug. The commercially available product is a racemic mixture of R and S enantiomers, both of which display in vitro 5-LO inhibitor activity. A number of studies have been carried out in recent years to design 5-LO inhibitors with dual activity: 5-LO/cyclooxygenase (COX) inhibitors have received particular attention as antiinflammatory agents, and compounds either with dual 5-LO/ thromboxane A2 synthase inhibitory activity or with 5-LO inhibitor and platelet-activating factor (PAF) receptor antagonist mixed properties have also been developed. These are examples of multitarget drugs, which should be able to modulate more than one target simultaneously; their development represents an alternative approach to using drug cocktails especially in the treatment of complex diseases such as atherosclerosis and inflammation. The most common strategy to obtain these products is the combination of two appropriate drugs, or their crucial parts, into a single molecule. To our knowledge there has not yet been any documented examples of nitric oxide (NO) donor/5-LO inhibitor hybrids, despite the clear interest in such a combination. Indeed, NO is a physiological messenger that triggers a variety of actions in different systems. In particular, it plays very important roles in the cardiovascular system in maintaining a number of homeostatic responses: preservation of endothelial integrity, arterial blood vessel dilation including pulmonary arterial vasculature, inhibition of platelet adherence and aggregation, attenuation of leukocyte adherence, and activation and inhibition of vascular smooth muscle cell proliferation. NO also triggers relevant action in airways, inducing relaxation of airway smooth muscle, pro-inflammatory or anti-inflammatory effects, and regulation of mucociliary clearance. The use of NO donors in the treatment of cardiovascular disease (CD) is well known, while the therapeutic potential of these kinds of products in the field of respiratory disease is still under examination. Herein we propose new dual-action products, obtained by combining zileuton with NO donor nitrooxy or furoxan moieties. The synthesis of the final products required the preliminary preparation of a number of intermediates (Scheme 1). The substituted benzothiophene 3 was easily obtained by treating 6hydroxybenzothiophene (2) with n-butyllithium and anhydrous acetaldehyde in THF at 20 8C. The triflates 8–11 were prepared by the action of trifluoromethanesulfonyl anhydride in dichloromethane on the appropriate nitrooxy-substituted alcohols 4–7 in the presence of 2,6-lutidine at 40 8C and were immediately used. Treatment of 3 with sodium hydride in THF, followed by the appropriate triflates 8–11 in dichloromethane afforded the expected nitrates 14–17. The action of 37% hydrochloric acid on these products dissolved in THF/water in the presence of hydroxyurea at 50 8C afforded the target com[a] Prof. D. Boschi, Dr. M. Giorgis, Prof. C. Cena, Dr. N. C. Talniya, Prof. A. Di Stilo, Prof. R. Fruttero, Prof. A. Gasco Department of Drug Science and Technology University of Turin, Via Pietro Giuria 9, 10125 Torino (Italy) Fax: (+39)0116707286 E-mail : [email protected] [b] Dr. G. Morini, Prof. G. Coruzzi, Dr. E. Guaita Department of Human Anatomy, Pharmacology and Forensic Medicine Section of Pharmacology, University of Parma Via Volturno 39, 43100 Parma (Italy)