Amiloride (1), the prototypical epithelial sodium channel (ENaC) blocker, has been administered with limited success as aerosol therapy for improving pulmonary function in patients with the genetic disorder cystic fibrosis. This study was conducted to synthesize and identify more potent, less reversible ENaC blockers, targeted for aerosol therapy and possessing minimal systemic renal activity. A series of novel 2-substituted acylguanidine analogues of amiloride were synthesized and evaluated for potency and reversibility on bronchial ENaC. All compounds tested were more potent and less reversible at blocking sodium-dependent short-circuit current than amiloride. Compounds 30-34 showed the greatest potency on ENaC with IC(50) values below 10 nM. A regioselective difference in potency was found (compounds 30, 39, and 40), whereas no stereospecific (compounds 33, 34) difference in potency on ENaC was displayed. Lead compound 32 was 102-fold more potent and 5-fold less reversible than amiloride and displayed the lowest IC(50) value ever reported for an ENaC blocker.

The review focuses on the central neuronal circuits involved in energy homeostasis and the opportunities these offer for pharmacological intervention to decrease feeding behaviour and reduce weight. This article is based on the presentation 'New central targets for the treatment of obesity ' (Sargent, British Pharmacological society, Clinical Section Symposium, December 2008). Central neuronal substrates controlling weight offer numerous opportunities for pharmacological intervention. These opportunities range from non-specific enhancement of monoamine signalling (triple reuptake inhibitors) to targeting specific monoamine receptor subtypes (5-HT2c and 5-HT6). The data reviewed suggest that these approaches will lead to weight loss; whether this is sufficient to produce clinically meaningful effect remains to be determined. Combination therapy targeting more than one mechanism may be a means of increasing the magnitude of the response. Preclinical studies also suggest that novel approaches targeting specific neuronal pathways within the hypothalamus, e.g. MCH1 receptor antagonism, offer an opportunity for weight reduction. However, these approaches are at an early stage and clinical studies will be needed to determine if these novel approaches lead to clinically meaningful weight loss and improvements in co-morbid conditions such as diabetes and cardiovascular disorders. The obesity problemObesity is a major global health problem and rates of obesity [body mass index (BMI) >30 kg m -2 ] have risen steadily year on year. Recent figures show an incidence of obesity of more than 1 in 4 in many parts of the USA [1]. These high rates are similar in other developed countries and the incidence of weight gain is increasing in less developed regions. Obesity is not just a cosmetic or lifestyle illness but leads to many life-threatening health complications. As the BMI increases the incidence of metabolic disorders (Type 2 diabetes), hypertension, cancer and musculoskeletal problems increases [1][2][3]. In 1999, Calle et al. reported mortality rates for all causes doubled when the BMI increased from 25 to >35 [4].The annual direct healthcare costs associated with obesity in the USA are in excess of $93 billion [5]. Particularly worrying is the fact that the incidence of obesity in children and young adults is on the increase, with some reports suggesting that up to 25% of children may be obese. The long-term health implications of these findings are far reaching and suggest that for the first time intergenerational increase in life expectancy will not occur and these children will have a shorter life span than their parents because of health complications associated with weight gain [6] (Figure 1).Obesity occurs when the balance between energy input (food intake) and energy expenditure (exercise, activity) is disrupted, i.e. more food is consumed than utilized, leading to excess fat stores being laid down. Although for some people a calorie-restricted diet and exercise can lead to a reduction in weight gain, for many peop...

No abstract