Action of (R)-sila-venlafaxine and reboxetine to antagonize cisplatin-induced acute and delayed emesis in the ferret.

The chemotherapeutic drug cisplatin is associated with severe gastrointestinal toxicity that can last for several days. A recent strategy to treat the nausea and emesis includes the combination of a 5-HT3 receptor antagonist, a glucocorticoid, and an NK1 receptor antagonist. The present studies explore the use of the selective noradrenaline reuptake inhibitors, (R)-sila-venlafaxine, (R,R)-reboxetine and (S,S)-reboxetine to prevent cisplatin (5 mg/kg, i.p.)-induced acute (0-24 h) and delayed (24-72 h) emesis in ferrets. The positive control regimen of ondansetron and dexamethasone, both at 1 mg/kg/8 h, reduced acute and delayed emesis by 100 (P<0.001) and 61% (P<0.05). (R)-sila-venlafaxine at 5 and 15 mg/kg/4 h reduced acute emesis by 86 (P<0.01) and 66% (P<0.05), respectively and both enantiomers of reboxetine at 1 mg/kg/12 h also reduced the response by approximately 70-90% (P<0.05). Out of the reuptake inhibitors, only (R)-sila-venlafaxine at 15 mg/kg/4 h was active to reduce delayed emesis (a 57% reduction was observed (P<0.05)); its terminal plasma levels were positively correlated with an inhibition of emesis during the delayed phase (P<0.05). (R)-sila-venlafaxine was also examined against a higher dose of cisplatin 10 mg/kg, i.p. (3 h test) and it dose-dependently antagonized the response (maximum reduction was 94% at 10 mg/kg, p.o.; P<0.01) but it was ineffective against apomorphine (0.125 mg/kg, s.c.) and ipecacuanha (2 mg/kg, p.o.)-induced emesis (P>0.05). In conclusion, the studies provide the first evidence for an anti-emetic potential of noradrenaline reuptake inhibitors to reduce chemotherapy-induced acute and delayed emesis.

Update on the therapeutic potential of PDE4 inhibitors.

Phosphodiesterase (PDE) enzymes are responsible for the inactiviation of cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP). Phosphodiesterase 4 (PDE4) is a cAMP specific phosphodiesterase expressed in inflammatory cells such as eosinophils. Inhibition of PDE4 results in an elevation of cAMP in these cells, which in turn downregulates the inflammatory response. The anti-inflammatory effects of PDE4 inhibitors have been well documented both in vitro and in vivo in a range of animal models. The potential use of PDE4 inhibitors as anti-inflammatory agents for the treatment of diseases such as asthma, chronic obstructive pulmonary disease (COPD) and multiple sclerosis (MS), has received considerable attention from the pharmaceutical industry but to date, there are no selective PDE4 inhibitors on the market. Early PDE4 inhibitors, such as rolipram suffered from dose limiting side effects, including nausea and emesis, which severely restricted their therapeutic utility. Second generation compounds such as cilomilast have been identified with reduced side effect liability. Indeed, cilomilast is showing good therapeutic effects in clinical trials for asthma and COPD and represents the most advanced selective PDE4 inhibitor for any indication. The utility of this class of inhibitor in other inflammatory diseases is less well advanced. However, data in animal models of rheumatoid arthritis (RA) and MS suggests that there is also significant potential for PDE4 inhibitors as treatments for these diseases and the results of clinical trials in these disease areas are eagerly awaited.

Silicon analogues of the nonpeptidic GnRH antagonist AG-045572: syntheses, crystal structure analyses, and pharmacological characterization.

AG-045572 (CMPD1, 1 a) is a nonpeptidic gonadotropin-releasing hormone (GnRH) antagonist that has been investigated for the treatment of sex hormone-related diseases. In the context of systematic studies on sila-substituted drugs, the silicon analogue disila-AG-045572 (1 b) and its derivative 2 were prepared in multi-step syntheses and characterized by elemental analyses (C, H, N), NMR spectroscopic studies (1H, 13C, 29Si), and single-crystal X-ray diffraction. The pharmacological properties of compounds 1 a, 1 b, and 2 were compared in terms of their in vitro potency at cloned human and rat GnRH receptors. Compounds 1 a and 2 were also examined in regard to their pharmacokinetics and in vivo efficacy in both castrated rat (luteinizing hormone (LH) suppression) and intact rat (testosterone suppression) models. The efficacy and pharmacokinetic profiles of 1 a and its silicon-containing analogue 2 appear similar, indicating that replacement of the 5,6,7,8-tetrahydronaphthalene ring system by the 1,3-disilaindane skeleton led to retention of efficacy. Therefore, the silicon compound 2 represents a novel drug prototype for the design of potent, orally available GnRH antagonists suitable for once-daily dosing.

Trimethylsilylpyrazoles as novel inhibitors of p38 MAP kinase: a new use of silicon bioisosteres in medicinal chemistry.

The synthesis, physicochemical properties and pharmacological profiles of two novel silicon-containing p38 MAP kinase inhibitors are described.

(R)-sila-venlafaxine: a selective noradrenaline reuptake inhibitor for the treatment of emesis.

Sila-substitution of drugs (the carbon/silicon switch) is a concept that is being successfully used for the development of new chemical entities. The (R)-sila-analogue of the antidepressant venlafaxine is devoid of the serotonin reuptake inhibition observed with the marketed drug, leading to a selective noradrenaline reuptake inhibitor displaying anti-emetic properties.

Selecting screening candidates for kinase and G protein-coupled receptor targets using neural networks.

A series of neural networks has been trained, using consensus methods, to recognize compounds that act at biological targets belonging to specific gene families. The MDDR database was used to provide compounds targeted against gene families and sets of randomly selected molecules. BCUT parameters were employed as input descriptors that encode structural properties and information relevant to ligand-receptor interactions. In each case, the networks identified over 80% of the compounds targeting a gene family. The technique was applied to purchasing compounds from external suppliers, and results from screening against one gene family demonstrated impressive abilities to predict the activity of the majority of known hit compounds.

8-Methoxyquinoline-5-carboxamides as PDE4 inhibitors: a potential treatment for asthma.

A series of bicyclic heteroaryl ring systems was considered as a replacement for the 3-cyclopentyloxy-4-methoxyphenyl moiety in rolipram resulting in the discovery of 8-methoxyquinoline-5-carboxamides as potent inhibitors 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).

7-Methoxyfuro[2,3-c]pyridine-4-carboxamides as PDE4 inhibitors: a potential treatment for asthma.

The synthesis and pharmacological profile of a novel series of 7-methoxy-furo[2,3-c]pyridine-4-carboxamides is described. Some of these compounds were found to be potent inhibitors of phosphodiesterase type 4 (PDE4).

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).