Background and Purpose: ATP‐sensitive K + channels (K ATP ) play a pivotal role in contractility of urinary bladder smooth muscle. This study reports the characterization of 4‐methyl‐N‐(2,2,2‐trichloro‐1‐(3‐pyridin‐3‐ylthioureido)ethyl)benzamide (A‐251179) as a K ATP channel opener. Experimental Approach: Glyburide‐sensitive membrane potential, patch clamp and tension assays were employed to study the effect of A‐251179 in vitro . The in vivo efficacy of A‐251179 was characterized by suppression of spontaneous contractions in obstructed rat bladder and by measuring urodynamic function of urethane‐anesthetized rat models. Key Results: A‐251179 was about 4‐fold more selective in activating SUR2B‐Kir6.2 derived K ATP channels compared to those derived from SUR2A‐Kir6.2. In pig bladder smooth muscle strips, A‐251179 suppressed spontaneous contractions, about 27‐ and 71‐fold more potently compared to suppression of contractions evoked by low‐frequency electrical stimulation and carbachol, respectively. In vivo , A‐251179 suppressed spontaneous non‐voiding bladder contractions from partial outlet‐obstructed rats. Interestingly, in the neurogenic model where isovolumetric contractions were measured by continuous transvesical cystometry, A‐251179 at a dose of 0.3 μmol kg ‐1 , but not higher, was found to increase bladder capacity without affecting either the voiding efficiency or changes in mean arterial blood pressure. Conclusions and Implications: The thioureabenzamide analog, A‐251179 is a potent novel K ATP channel opener with selectivity for SUR2B/Kir6.2 containing K ATP channels relative to pinacidil. The pharmacological profile of A‐251179 is to increase bladder capacity and to prolong the time between voids without affecting voiding efficiency and represents an interesting characteristic to be explored for further investigations of K ATP channel openers for the treatment of overactive bladder. British Journal of Pharmacology (2007) 151 , 467–475; doi: 10.1038/sj.bjp.0707249

Background and Purpose:The large‐conductance Ca2+‐activated K+ channel (BKCa, KCa1.1) links membrane excitability with intracellular Ca2+ signaling and plays important roles in smooth muscle contraction, neuronal firing, and neuroendocrine secretion. This study reports the characterization of a novel BKCa channel blocker, 2,4‐dimethoxy‐N‐naphthalen‐2‐yl‐benzamide (A‐272651).Experimental Approach:86Rb+ efflux in HEK‐293 cells expressing BKCa was measured. Effects of A‐272651 on BKCa α‐ and BKCa αβ1‐mediated currents were evaluated by patch‐clamp. Effects on contractility were assessed using low‐frequency electrical field stimulated pig detrusor and spontaneously contracting guinea pig detrusor. Effects of A‐272651 on neuronal activity were determined in rat small diameter dorsal root ganglia (DRG).Key Results:A‐272651 (10 μM) inhibited 86Rb+ efflux evoked by NS‐1608 in HEK‐293 cells expressing BKCa currents. A‐272651 concentration‐dependently inhibited BKCa currents with IC50 values of 4.59 μM (Hill coefficient 1.04, measured at +40 mV), and 2.82 μM (Hill coefficient 0.89), respectively, for BKCa α and BKCa αβ1‐mediated currents. Like iberiotoxin, A‐272651 enhanced field stimulated twitch responses in pig detrusor and spontaneous contractions in guinea pig detrusor with EC50 values of 4.05±0.05 and 37.95±0.12 μM, respectively. In capsaicin‐sensitive DRG neurons, application of A‐272651 increased action potential firing and prolonged action potential duration.Conclusions and Implications:These data demonstrate that A‐272651 modulates smooth muscle contractility and neuronal firing properties. Unlike previously reported peptide BKCa blockers, A‐272651 represents one of the first small molecule BKCa channel blockers that could serve as a useful tool for further characterization of BKCa channels in physiological and pathological states.British Journal of Pharmacology (2007) 151, 798–806; doi:10.1038/sj.bjp.0707278

A series of novel cyanoguanidine derivatives was designed and synthesized. Condensation of N-(1-benzotriazol-1-yl-2,2-dichloropropyl)-substituted benzamides with N-(substituted-pyridin-3-yl)-N'-cyanoguanidines furnished N-{2,2-dichloro-1-[N'-(substituted-pyridin-3-yl)-N''-cyanoguanidino]propyl}-substituted benzamide derivatives. These agents were glyburide-reversible potassium channel openers and hyperpolarized human bladder cells as assessed by the FLIPR membrane potential dye (KATP-FMP). These compounds were also potent full agonists in relaxing electrically stimulated pig bladder strips, an in vitro model of overactive bladder. The most active compound 9 was evaluated for in vivo efficacy and selectivity in a pig model of bladder instability. Preliminary pharmacokinetic studies in dog demonstrated excellent oral bioavailability and a t1/2 of 15 h. The synthesis, SAR studies, and biological properties of these agents are discussed.

Structure-activity relationships were investigated on the tricyclic dihydropyridine ( DHP) K-ATP openers 9-(3-bromo-4-fluorophenyl)-5,9- dihydro-3H, 4H-2,6-dioxa-4-azacyclopenta[ b] naphthalene-1,8-dione ( 6) and 10( 3-bromo-4-fluorophenyl)-9,10-dihydro-1H, 8H-2,7-dioxa-9-azaanthracene-4,5-dione ( 65). Substitution off the core of the DHP, absolute stereochemistry, and aromatic substitution were evaluated for KATP channel activity using Ltk-cells stably transfected with the Kir6.2/SUR2B exon 17- splice variant and in an electrically stimulated pig bladder strip assay. A select group of compounds was evaluated for in vitro inhibition of spontaneous bladder contractions. Several compounds were found to have the unique characteristic of partial efficacy in both the cell-based and electrically stimulated bladder strip assays but full efficacy in inhibiting spontaneous bladder strip contractions. For compound 23b, this profile was mirrored in vivo where it was fully efficacious in inhibiting spontaneous myogenic bladder contractions but only partially able to reduce neurogenically mediated reflex bladder contractions.

Structure-activity studies were performed on the alpha(1A)-adrenoceptor (AR) selective agonist N-[5-(1H-imidazol-4-yl)-5,6,7,8-tetrahydro-1-naphthalenyl]methanesulfonamide (4). Compounds were evaluated for binding activity at the alpha(1A), alpha(1b), alpha(1d), alpha(2a), and alpha(2B) subtypes. Functional activity in tissues containing the alpha(1A) (rabbit urethra), alpha(1B) (rat spleen), alpha(1D) (rat aorta), and alpha(2A) (rat prostatic vas deferens) was also evaluated. A dog in vivo model simultaneously measuring intraurethral pressure (IUP) and mean arterial pressure (ALAP) was used to assess the uroselectivity of the compounds. Many of the compounds that were highly selective in vitro for the alpha(1A)-AR subtype were also more uroselective in vivo for increasing IUP over MAP than the nonselective alpha(1)-agonists phenylpropanolamine (PPA) (1) and ST-1059 (2, the active metabolite of midodrine), supporting the hypothesis that greater alpha(1A) selectivity would reduce cardiovascular side effects. However, the data also support a prominent role of the alpha(1A)-AR subtype in the control of MAP.

SAR studies were conducted around a series of arylalkylimidazoles and arylalkylimidazolines based upon the core structure of A-61603. Changes in ring size, the heterocyclic appendage, aromatic substitution and absolute stereochemistry were examined. Compounds were evaluated for subtype selectivity in vitro using radioligand binding and functional tissue strip assays. In vivo, selectivity for effects on intraurethral pressure (IUP) versus mean arterial pressure (MAP) was determined in anesthetized dogs. Compounds were identified that displayed selectivity in vitro for the alpha(1A) subtype and that also showed enhanced urethral selectivity relative to non-subtype selective agents.

In search of a novel chemotype of KATP channel openers a series of tricyclic dihydropyridopyrazolones and dihydropyridoisoxazolones was synthesized. It was found that cyclopentanone in the left hand portion of the molecule was 4-fold more potent than cyclohexanone. Introduction of gem-dimethyl groups as well as incorporation of oxygen in the cyclohexanone ring in the left hand portion of the molecule increased the potency 10-fold. In the right hand portion of the molecule, the NH-group of the pyrazolone can be effectively substituted by oxygen increasing the activity 5-fold. Incorporation of a methyl group adjacent to the dihydropyridine (DHP) nitrogen not only significantly boosted activity, but also provided an additional benefit of increased metabolic stability. In vitro tests on the tissue from pig bladder strips provided further confirmation of KATP activity of these compounds.

Calcium activated K(+) channels (K(Ca) channels) are found in a variety of smooth muscle tissues, the most characterized of which are the large conductance K(Ca) channels (BK(Ca) or maxi-K(+) channels). Recent medicinal chemistry efforts have identified novel BK(Ca) openers including 2-amino-5-(2-fluoro-phenyl)-4-methyl-1H-pyrrole-3-carbonitrile (NS-8), BMS-204352 and its analog 3-(5-chloro-2-hydroxy-phenyl)-3-hydroxy-6-trifluoromethyl-1,3-dihydro-indol-2-one (compound 1), and 5,7-dichloro-4-(5-chloro-2-hydroxy-phenyl)-3-hydroxy-1H-quinolin-2-one (compound 2). Although these compounds are effective BK(Ca) openers as shown by electrophysiological methods, little is known about their effects on smooth muscle contractility. In this study, the responsiveness of structurally diverse BK(Ca) openers-NS-8, compounds 1 and 2 and the well characterized nonselective NS-1619-was assessed using segments of endothelium denuded rat aorta, rat and guinea pig detrusor precontracted with extracellular K(+), and Landrace pig detrusor stimulated by electrical field. In all preparations, the compounds tested inhibited or completely abolished contractions with similar potencies (-logIC(50) values: 3.8 to 5.1). In rat aorta, in the presence of 80 mM K(+), the compounds significantly shifted the concentration-response curve to the right compared with those obtained in 30 mM K(+). These data are consistent with K(+) channel (BK(Ca) channel) activation as the underlying mechanism of relaxation by compounds that share the electrophysiological property of BK(Ca) current activation. The similar potencies at detrusor and vascular smooth muscle suggest that the achievement of smooth muscle selectivity in vitro with the representative compounds examined in this study may prove to be a challenge when targeting BK(Ca) channels for smooth muscle indications such as overactive bladder.

1. This study reports on the identification and characterization of a 1,4-dihydropyridine analogue, 9-(3,4-dichlorophenyl)-3,3,6,6-tetramethyl-3,4,6,7,9,10-hexahydro-1,8(2H,5H)-acridinedione (A-184209) as a novel inhibitor of ATP-sensitive K(+) channels. 2. A-184209 inhibited membrane potential changes evoked by the prototypical cyanoguanidine ATP-sensitive K(+) channel opener (KCO) P1075 in both vascular (A10) and urinary bladder smooth muscle cells with IC(50) values of 1.44 and 2.24 micro M respectively. 3. P1075-evoked relaxation of 25 mM K(+) stimulated aortic strips was inhibited by A-184209 in an apparently competitive fashion with a pA(2) value of 6.34. 4. The potencies of A-184209 to inhibit P1075-evoked decreases in membrane potential responses in cardiac myocytes (IC(50)=0.53 micro M) and to inhibit 2-deoxyglucose-evoked cation efflux pancreatic RINm5F cells (IC(50)=0.52 micro M) were comparable to the values for inhibition of smooth muscle K(ATP) channels. 5. On the other hand, a structural analogue of A-184209 that lacked the gem-dimethyl substituent, 9-(3,4-dichlorophenyl)-3,4,6,7,9,10-hexahydro-1,8(2H,5H)-acridinedione (A-184208), was found to be a K(ATP) channel opener, evoking membrane potential responses in A10 smooth muscle cells (EC(50)=385 nM) and relaxing aortic smooth muscle strips (IC(50)=101 nM) in a glyburide-sensitive manner. 6. Radioligand binding studies demonstrated that A-184209 displaced SUR1 binding defined by [(3)H]glyburide binding to RINm5F cell membranes with a K(i) value of 0.11 micro M whereas A-184208 was ineffective. On the other hand, both A-184209 (K(i)=1.34 micro M) and A-184208 (K(i)=1.14 micro M) displaced binding of the KCO radioligand, [(125)I]A-312110 in guinea-pig bladder membranes with similar affinities. 7. These studies demonstrate that A-184209 is a novel and structurally distinct compound that inhibits K(ATP) channels in smooth muscle with potencies comparable to glyburide. The structural overlap between DHP openers and blockers, together with their differential interaction with ligand binding sites, support the notion that both openers and blockers bind to similar or very closely coupled sites on the sulfonylurea receptor and that subtle changes in the pharmacophore itself could switch functional properties from K(ATP) channel activation to inhibition.

N-[3-(1H-Imidazol-4-ylmethyl)phenyl]ethanesulfonamide, maleate (ABT-866) is a novel alpha(1)-adrenoceptor agent with mixed pharmacological properties in vitro. Compared to phenylephrine, ABT-866 demonstrates intrinsic activity at the alpha(1A)-adrenoceptor subtype present in the rabbit urethra (pD(2) = 6.22, with 80% of the phenylephrine response), reduced intrinsic activity at the alpha(1B)-adrenoceptor subtype in the rat spleen (pD(2)= 6.16, with 11% of the phenylephrine response), and no intrinsic activity at the rat aorta alpha(1D)-adrenoceptor subtype. ABT-866 also demonstrated antagonism at the rat spleen alpha(1B)-adrenoceptor (pA(2) = 5.39 +/- 0.08, slope = 1.20 +/- 0.12), and the rat aorta alpha(1D)-adrenoceptor (pA(2)= 6.18 +/- 0.09, slope = 0.96 +/- 0.13). This is in contrast to the weak non-selective activity seen with the alpha(1)-adrenoceptor agonist, phenylpropanolamine (2-amino-1-phenyl-1-propanol hydrochloride), and the alpha(1A/D)-adrenoceptor selective agonist 1-(2',5'-dimethoxyphenyl)-2-aminoethanol hydrochloride (ST-1059), the active metabolite of midodrine, that has been used clinically for the treatment of stress urinary incontinence. This study identifies a unique agent that may prove to be a valuable in vivo tool in testing the hypothesis that the alpha(1A)-adrenoceptor can be stimulated to contract the smooth muscle present in the urethra without evoking blood pressure elevations presumably caused by alpha(1B)- and alpha(1D)-adrenoceptor subtype involvements in the vasculature.

This meeting report summarizes advances and notable developments in the pharmaceutical management of urological diseases presented at various sessions during the Annual Meeting of the American Urological Association held in Anaheim, California, June 2-7, 2001. More than 10,000 attendees drawn from clinical and preclinical research deliberated on the latest trends in surgical and pharmacotherapeutic management in diverse areas of urology. In particular, several forums were dedicated to reviewing scientific trends, emerging concepts and therapies in urological diseases, such as overactive bladder, erectile dysfunction and lower urinary tract symptoms, which are the focus of this report.

The synthesis and in vitro characterization of A-119637 and A-123189, two novel, selective and potent alpha1D antagonists, are described.

A-80426 (N-[2-(benzofuran-6-yl)ethyl]-N-[(R)-(+)-5-methoxy-1,2,3,4-tetrahydronaphthalen-1-yl methyl]-N-methylamine) is a novel compound with potential antidepressant activity. A-80426 inhibits synaptosomal serotonin (5HT) uptake (IC50 = 13 nM) more potently than fluoxetine (IC50 = 308 nM), and blocks [H-3]-paroxetine binding (K-I = 3.8 nM) to 5HT uptake sites. A-80426 inhibits [H-3]-rauwolscine binding to alpha(2)-adrenoceptors (K-I = 2.0 nM), blocks alpha(2)-adrenoceptors (pEC(30) = 7.4-7.5) in electrically stimulated rat atria and vas deferens, and increases electrically stimulated [H-3]-NE overflow from brain slices. A-80426 lacks significant activity at isolated tissue models of alpha(1)- or beta-adrenergic sites or at M(3) muscarinic or H-1 histaminergic receptors. A-80426 has negligible radioligand binding activity at 5HT(1) and beta-adrenergic receptors, but exhibits a K-I value of 144 nM at 5HT(2) receptors. A-80426 interacts with both dopamine D-1 (K-I = 744 nM) and D-2 (K-I = 51.5 nM) receptors. Functionally, the compound antagonizes dopamine-induced changes in cyclic AMP formation with K-I values of 133 nM and 185 nM at D-1 and D-2 receptors, respectively. The potent alpha(2)-adrenoceptor blocking activity of A-80426 in radioligand binding assays is not reflected in isolated tissue bioassays, and may thus have less functional consequence in determining the in vivo profile of the compound. Accompanying behavioral data [Giardina et al., 1995], while indicating activity in the olfactory bulbectomized rat model of antidepressant action, shows a marked reduction in the alpha(2)-antagonistic properties of A-80426 in other in vivo models, suggesting that the antidepressant-like activity may be caused primarily by inhibition of 5HT uptake. (C) 1995 Wiley-Liss, Inc.