Phosphodiesterase 4 inhibitors for the treatment of asthma

Synthesis of PDE IVb Inhibitors. 3. Synthesis of (+)-, (-)-, and (±)-7-[3-(cyclopentyloxy)-4-methoxyphenyl]hexahydro-3H-pyrrolizin-3-one via reductive domino transformations of 3-β-carbomethoxyethyl-substituted six-membered cyclic nitronates

Simple three-step asymmetric and racemic syntheses of GlaxoSmithKline's highly potent PDE IVb inhibitor 1 were developed. The suggested approach is based on reductive domino transformations of 3-β-carbomethoxyethyl-substituted six-membered cyclic nitronates, which are easily accessed by a stereoselective [4 + 2] cycloaddition of an appropriate nitroalkene to vinyl ethers. In vitro studies of PDE IVb inhibition by enantiomeric pyrrolizidinones (+)-1 and (-)-1 were performed.

Synthesis and profile of SCH351591, a novel PDE4 inhibitor

The syntheses and pharmacological profiles of some 2-trifluoromethyl-8-methoxyquinoline-5-carboxamides are described. SCH351591 is a potent selective inhibitor of phosphodiesterase type 4 (PDE4).

8-Methoxyquinolines as PDE4 inhibitors

The synthesis and pharmacological profile of a novel series of 2-substituted 8-methoxyquinolines is described. The 2-trifluoromethyl compound was found to be a potent inhibitor of phosphodiesterase type 4 (PDE4).

PDE4 inhibitors induce emesis in ferrets via a noradrenergic pathway

The objective of this work was to assess the role of alpha(2)-adrenoceptors in emesis induced by inhibitors of type 4 phosphodiesterase (PDE4) in ferrets. Pre-treatment with yohimbine, MK-912 or MK-467 (alpha(2)-adrenoceptor antagonists) caused sudden and unexpected vomiting. In contrast, clonidine (alpha(2)-adrenoceptor agonist) did not induce emesis at doses ranging from 62.5-250 microg/kg s.c. At the dose of 250 microg/kg, clonidine also provided protection against emesis induced by the PDE4 inhibitors, PMNPQ (i.e. 6-(4-pyridylmethyl)-8-(3-nitrophenyl)quinoline, CT-2450 and R-rolipram. It was postulated that PDE4 inhibitors trigger emesis by mimicking the pharmacological actions of alpha(2)-adrenoceptor antagonists. This hypothesis was strengthened by the demonstration that PDE4 inhibitors can reverse the hypnotic effect of an alpha(2)-adrenoceptor mediated anaesthetic regimen in rats and ferrets. Similar to alpha(2)-adrenoceptor antagonists, PMNPQ, R-rolipram and S-rolipram dose-dependently decreased the duration of anaesthesia in rats injected with the combination xylazine/ketamine. While subcutaneous injections of CT-2450 (3-30 mg/kg) were without effect, a central infusion (6 microg i.c.v.) decreased the duration of anaesthesia. These studies suggest that the ferret is an appropriate model to study emesis induced by PDE4 inhibitors and that these compounds trigger the emetic reflex via a noradrenergic pathway, mimicking the pharmacological actions of a pre-synaptic alpha(2)-adrenoceptor inhibition.

Phosphodiesterase 4 inhibitors, structurally unrelated to rolipram, as promising agents for the treatment of asthma and other pathologies

An increase of cyclic adenosine and guanosine monophosphate (cAMP and cGMP) level can be achieved by inhibition of phosphodiesterases (PDEs), which are the enzymes responsible for the conversion of these second messengers into the corresponding 5-monophosphate inactive counterparts. The high heterogeneity in PDE families and in their tissue distribution, as well as their different functional role, make these enzymes very attractive targets for medicinal chemists. The PDE 4 family is particularly abundant in immunocompetent cells, where an increase of cAMP leads to the inhibition of the synthesis and release of pro-inflammatory mediators, cytokines and active oxygen species. Moreover PDE 4 inhibitors are able to reduce bronchial smooth muscle tone in vitro and show bronchodilatory effects in vivo. Thus, the current therapy for asthma, which is based on a combination of beta(2) agonists and corticosteroids, could be replaced by treatment with PDE 4 inhibitors. This review mainly covers PDE 4 inhibitors structurally related to xanthines and Nitraquazone, which appear to be very attractive models for the synthesis of novel PDE 4 inhibitors potentially useful for the treatment of asthma, chronic pulmonary obstructive disease and some autoimmune diseases. These compounds could be devoid of the central side-effects (nausea, vomiting, headache) of the archetypal Rolipram, which hampered its development as a drug. The review also highlights the novel structural classes of PDE 4 inhibitors recently reported in the literature.

Phosphodiesterase 4 (PDE4) inhibitors in asthma and chronic obstructive pulmonary disease (COPD)

Phosphodiesterases (PDE) are a family of enzymes responsible for the metabolism of the intracellular second messengers cyclic AMP and cyclic GMP. PDE4 is a cyclic AMP specific PDE that is the major if not sole cyclic AMP metabolizing enzymes found in inflammatory and immune cells, and contributes significantly to cyclic AMP metabolism in smooth muscles. Based on its cellular and tissue distribution and the demonstration that selective inhibitors of this isozyme reduce bronchoconstriction in animals and suppress the activation of inflammatory cells, PDE4 has become an important molecular target for the development of novel therapies for asthma and COPD. This chapter will review the evidence demonstrating the ability of PDE4 inhibitors to modify airway obstruction, airway inflammation and airway remodelling and hyperreactivity, will present some preliminary findings obtained with theses compounds in clinical trials and and will discuss experimental approaches designed to identify novel compounds that maintain the beneficial activity of the initial selective PDE4 inhibitors but with a reduced tendency of elicit the gastrointestinal side effects observed with this class of compounds.

Chemotherapeutic potential of phosphodiesterase inhibitors

The application of molecular cloning has revealed the phenomenal diversity and complexity of the phosphodiesterase isoenzyme family. Thus, more than 30 human phosphodiesterases are now known; all are apparently necessary for the seemingly simple task of hydrolysing the 3'-ester bond of either cyclic adenosine monophosphate or cyclic guanosine monophosphate. The availability of phosphodiesterase isoenzymes as pure recombinant proteins has greatly facilitated the identification of potent, selective inhibitors. The potential of these inhibitors to therapeutically exploit the molecular diversity of the phosphodiesterases has progressed significantly. A number of drugs are in clinical trials for asthma, and Viagra has become the first selective phosphodiesterase inhibitor to be approved by the US Food and Drug Administration.