From structure to clinic: Design of a muscarinic M1 receptor agonist with potential to treatment of Alzheimer's disease.

Current therapies for Alzheimer's disease seek to correct for defective cholinergic transmission by preventing the breakdown of acetylcholine through inhibition of acetylcholinesterase, these however have limited clinical efficacy. An alternative approach is to directly activate cholinergic receptors responsible for learning and memory. The M1-muscarinic acetylcholine (M1) receptor is the target of choice but has been hampered by adverse effects. Here we aimed to design the drug properties needed for a well-tolerated M1-agonist with the potential to alleviate cognitive loss by taking a stepwise translational approach from atomic structure, cell/tissue-based assays, evaluation in preclinical species, clinical safety testing, and finally establishing activity in memory centers in humans. Through this approach, we rationally designed the optimal properties, including selectivity and partial agonism, into HTL9936-a potential candidate for the treatment of memory loss in Alzheimer's disease. More broadly, this demonstrates a strategy for targeting difficult GPCR targets from structure to clinic.

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.

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.

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.

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).

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).

Pharmacology of N-(3,5-dichloro-1-oxido-4-pyridinyl)-8-methoxy-2-(trifluoromethyl)-5-quinoline carboxamide (SCH 351591), a novel, orally active phosphodiesterase 4 inhibitor.

N-(3,5-Dichloro-1-oxido-4-pyridinyl)-8-methoxy-2-(trifluoromethyl)-5-quinoline carboxamide (SCH 351591) has been identified as a potent (IC(50) = 58 nM) and highly selective type 4 phosphodiesterase (PDE4) inhibitor with oral bioactivity in several animal models of lung inflammation. N-(3,5-Dichloro-4-pyridinyl)-8-methoxy-2-(trifluoromethyl)-5-quinoline carboxamide (SCH 365351), the only significant in vivo metabolite, is also a potent and highly selective PDE4 inhibitor (IC(50) = 20 nM). Both SCH 351591 and SCH 365351 inhibited cytokine production in human blood mononuclear cell preparations. Oral SCH 351591 significantly attenuated allergen-induced eosinophilia and airway hyperreactivity in allergic guinea pigs at doses as low as 1 mg/kg. In this model, oral SCH 365351 showed similar potency. When SCH 351591 was administered orally to allergic cynomolgus monkeys at 3 mg/kg, Ascaris suum-induced lung eosinophilia was blocked. Hyperventilation-induced bronchospasm in nonallergic guinea pigs, a model for exercise-induced asthma, was also suppressed significantly by oral SCH 351591 at 0.3 mg/kg. Cilomilast (SB 207499; Ariflo), a PDE4 inhibitor currently being developed for asthma and chronic obstructive pulmonary disease (COPD), was 10- to 30-fold less potent than SCH 351591 at inhibiting guinea pig lung eosinophilia and hyperventilation-induced bronchospasm. In a ferret model of emesis, maximum nonemetic oral doses of SCH 351591 and cilomilast were 5 and 1 mg/kg, respectively. Comparison of plasma levels at these nonemetic doses in ferrets to those at doses inhibiting hyperventilation-induced bronchospasm in guinea pigs gave a therapeutic ratio of 16 for SCH 351591 and 4 for cilomilast. Thus, SCH 351591 exhibits a promising preclinical profile as a treatment for asthma and COPD.

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).