Pharmacological effect of TRK-380, a novel selective human ß3-adrenoceptor agonist, on mammalian detrusor strips.

OBJECTIVE: To clarify the potential of TRK-380 as a drug for overactive bladder in humans by evaluating the agonistic activities for human ß-adrenergic receptors (ß-ARs) and the relaxing effects on isolated detrusor strips. METHODS: The agonistic activities for human ß-ARs were evaluated in SK-N-MC cells (for human ß(3)-ARs) and Chinese hamster ovary cells expressing human ß(1)- or human ß(2)-ARs using the cyclic adenosine monophosphate accumulation assay. The relaxing effects on the resting tension in isolated detrusor strips from humans, monkeys, dogs, and rats and on carbachol- or KCl-induced contractions in human detrusor strips were evaluated. RESULTS: In the cyclic adenosine monophosphate accumulation assay, the agonistic activity of TRK-380 for human ß(3)-ARs was potent and equivalent to that of the potent nonselective ß-AR agonist isoproterenol and superior to that of selective ß(3)-AR agonists, such as BRL-37344 and CL316,243. TRK-380 showed no agonistic activity for human ß(1)-ARs and a weak agonistic effect on human ß(2)-ARs. In isolated detrusor strips, the concentration-dependent relaxing effects of TRK-380 on the resting tension were equivalent to those of isoproterenol in humans, monkeys, and dogs but weaker than the effects in rats. The selective ß(3)-AR antagonist SR59230A shifted the concentration-response curve in a concentration-dependent manner to TRK-380 for the resting tension of human detrusor strips to the right. TRK-380 had a concentration-dependent relaxing effect on the contractile responses to carbachol and KCl in human detrusor strips. CONCLUSION: TRK-380 was a potent and selective human ß(3)-AR agonist, and the isolated human detrusor relaxation was mainly mediated by activation of the ß(3)-AR. Consequently, TRK-380 might be a promising compound for the treatment of overactive bladder.

Synthesis of novel triplet drugs with 1,3,5-trioxazatriquinane skeletons and their pharmacologies. 1: Synthesis of triplet drugs with morphinan skeletons.

We synthesized symmetrical and nonsymmetrical triplet drugs with 1,3,5-trioxazatriquinane skeletons. The isolation of key intermediates, oxazoline dimers, made it possible to effectively produce nonsymmetrical triplets. Among the synthesized triplets, KNT-93, composed of three identical opioid µ receptor agonists, showed dose-dependent antinociception via the µ receptor. The effect was 56-fold more potent than that of morphine, a representative µ agonist. The profound analgesic effect induced by KNT-93 might result from simultaneous occupation of three µ opioid receptors.

Synthesis of new opioid derivatives with a propellane skeleton and their pharmacology: part 1.

The observation that 17-cyclopropylmethylmorphinan derivatives without the 4,5-epoxy ring showed more κ selectivity than those with a 4,5-epoxy ring led us to develop a working hypothesis: the position of the plane composed of the A and B rings would influence the opioid receptor type selectivity and that the decrease in the torsion angle C11-C12-C13-C14 could improve the κ selectivity. Consistent with our hypothesis, KNT-42 with an N-cyclopropylmethyl propellane structure, whose A and B rings were fixed in a torsion angle of approximately 0°, showed κ selective agonist activity.

Synthesis of 6,14-epoxymorphinan derivatives and their pharmacologies.

A novel 6,14-epoxymorphinan benzamide derivative (NS22) that was previously reported showed opioid κ receptor agonistic activity and analgesic activity. The unsatisfactory κ selectivity of NS22 led us to synthesize its derivatives to improve the opioid κ receptor selectivity and the agonist activity. In the course of SAR of the various derivatives, 17-benzyl-6,14-epoxymorphinan derivatives (KNT-33, 53, 55, 80, 90, 133) were found to show high selectivities and affinities for the opioid κ receptor. In addition, KNT-33, 53, 55 showed dose-dependent analgesic effects in acetic acid writhing tests. Therefore, 17-benzyl substituents may play an important role for developing κ selectivity.

Synthesis of pyrrolomorphinan derivatives as kappa opioid agonists.

We synthesized pyrrolomorphinan derivatives 6, 7, and 9 to examine whether the pyrrole ring would be an accessory site in the kappa opioid receptor selective antagonist, nor-binaltorphimine. Derivative 6 had an alpha,beta-unsaturated ketone substituent that strongly bound to the kappa receptor. The compound with the highest kappa receptor selectivity, 6e, produced a dose-dependent antinociceptive effect in the mouse acetic acid writhing test. However, derivatives 7 and 9, which did not have alpha,beta-unsaturated ketone substituents, showed less kappa receptor selectivity than compound 6. Based on structure-activity relationships, we proposed that these compounds adopted active structures for kappa selective agonist activity. The pyrrole ring would not function as an accessory site, but the ability of the side chain on the pyrrole ring to localize above the C-ring appeared to confer kappa selective agonist activity. These results will promote the design of novel kappa agonists.

[Pharmacological effects of nalfurafine hydrochloride, a kappa-opioid receptor agonist].

Nalfurafine hydrochloride, a kappa-opioid receptor agonist, was approved in January 2009 and released to the market on March 2009 for the indication of "Improvement of pruritus in hemodialysis patients (only for cases resistant to conventional treatments)" in Japan (Brand Name: REMITCH CAPSULES 2.5 microg, Marketing Authorization Holder: Toray Industries, Inc., Distributed by Torii Pharmaceutical Co., Ltd., Co-developed by Japan Tobacco Inc.). In addition to antipruritic effect, nalfurafine hydrochloride showed ameliorating effects on pain, neuropathic pain, drug dependence, schizophrenia and dyskinesia in non-clinical studies. Therefore, nalfurafine hydrochloride may become a useful therapeutic agent for their diseases.

Drug design and synthesis of a novel kappa opioid receptor agonist with an oxabicyclo[2.2.2]octane skeleton and its pharmacology.

A conformational analysis of kappa opioid receptor agonists, TRK-820 and U-50,488H indicated an active conformation of TRK-820 in which the C-ring was in the boat form with the 14-OH interacting with the amide nitrogen. Based on the obtained active conformation of TRK-820, we designed and synthesized a novel kappa agonist KNT-63 with oxabicyclo[2.2.2]octane skeleton. KNT-63 showed profound antinociceptive effects via the kappa receptor which were as potent as that of TRK-820.

Aerobic oxidation of indolomorphinan without the 4,5-epoxy bridge and subsequent rearrangement of the oxidation product to spiroindolinonyl-C-normorphinan derivative.

Aerobic oxidation of indolomorphinan 1 without a 4,5-epoxy bridge proceeded in the presence of platinum catalyst to give indoleninomorphinan 2 or quinolono-C-normorphinan 5. The 4-hydroxy group would play an important role in deciding the course of the reaction. Treatment of 2a with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) gave spiroindolinonyl-C-normorphinan 3a whose structure resembles that of delta opioid receptor agonist spiroindanyloxymorphone (SIOM). Boron trichloride was effective for the reverse reaction from 3a to 2a without side reaction. This practical interconversion method between hydroxyindolenine and spiroindolinone would be useful for the design and construction of drug-like compound libraries. Although the compound 3b was expected to show the selectivity for delta opioid receptor because of the structural resemblance to SIOM, it was rather selective for 1 opioid receptor (1: K(i)=0.75nM; delta: K(i)=2.90nM; kappa: K(i)=13.4nM). The result suggests that the slight difference of the spatial location of the benzene rings in these compounds may definitively affect the binding affinity for delta opioid receptor.

Synthesis of a new opioid ligand having the oxabicyclo[3.2.1]octane skeleton using a new rearrangement reaction.

An attempt to prepare a trimer having the 1,3,5-trioxazatriquinane skeleton led to discovery of a novel rearrangement reaction that afforded a compound with an oxabicyclo[3.2.1]octane skeleton whose reaction mechanism was proposed. On the basis of this mechanism, we synthesized the rearranged product from a dimethyl acetal intermediate in excellent yield. The compound with an oxabicyclo[3.2.1]octane skeleton showed high affinity for mu and kappa but not delta opioid receptor types. The compound expected to be a key intermediate for novel kappa selective ligands.

Novel synthesis of a 1,3,5-trioxazatriquinane skeleton using a nitrogen clamp.

An alpha-hydroxyaldehyde derived from naltrexone was converted to an oxazoline dimer with ammonium chloride and sodium acetate in MeOH under reflux. The resulting dimer was treated with dl-camphorsulfonic acid in CHCl(3) to give the trimer. The method for trimer synthesis was also applied to general alpha-hydroxyaldehydes to afford trimers in good yield.

Synthesis of a stable iminium salt and propellane derivatives.

The treatment of morphinan 1 with NaH and MsCl provided very stable iminium salt 7 possessing propellane skeleton. One of the synthesized iminium salts 7, isobutyl derivative 7b, was crystallized and its structure was determined by X-ray crystallography. The natural bond orbital analysis suggested that the stability of the iminium should result from the stereoelectronic effect (hyperconjugation) attributed to their own structures.

Synthesis of N-isobutylnoroxymorphone from naltrexone by a selective cyclopropane ring opening reaction.

Selective ring opening reaction of the N-cyclopropylmethyl group in naltrexone (1d) was effected in the presence of platinum (IV) oxide and hydrobromic acid under a hydrogen atmosphere at rt to selectively afford N-isobutyl derivative 10. The binding affinity of N-i-Bu derivative 10 for opioid receptors was 11-17 times less than that of the corresponding N-CPM compound, naltrexone (1d). However, compound 10 showed dose-dependent analgesic effects. Contrary to expectations based on previous structure-activity relationship studies for a series of N-substituted naltrexone derivatives that compound 10 would be an opioid antagonist, 10 showed dose-dependent analgesia in the mouse acetic acid writhing test (ED(50): 5.05 mg/kg, sc), indicating it was an opioid agonist. This finding may have a great influence on the drug design of opioid agonists.

Structure-antitussive activity relationships of naltrindole derivatives. Identification of novel and potent antitussive agents.

We have previously reported antitussive effects of naltrindole (NTI), a typical delta opioid receptor antagonist, in a rat model. The ED50 values of NTI by intraperitoneal and peroral injections were 104 microg/kg and 1840 microg/kg, respectively, comparable to those of codeine. Codeine, one of the most reliable centrally acting antitussive drugs, has micro agonist activity and thus the same side effects as morphine, e.g., constipation, dependency, and respiratory depression. Because NTI is a delta opioid antagonist, its derivatives have potential as highly potent antitussives, free from the mu opioid agonist side effects. We attempted to optimize the NTI derivatives to develop novel antitussive agents. On the basis of the studies of structure-antitussive activity relationships of alkyl substituted NTI derivatives, we designed NTI derivatives with extra ring fused structures. As a clinical candidate, we identified a highly potent new compound, (5R,9R,13S,14S)-17-cyclopropylmethyl-6,7-didehydro-4,5-epoxy-5',6'-dihydro-3-methoxy-4'H-pyrrolo[3,2,1-ij]quinolino[2',1':6,7]morphinan-14-ol (5b) methanesulfonate (TRK-850) which was effective even by oral administration (ED50 6.40 microg/kg).

Effects of a novel beta(3)-adrenoceptor agonist, AJ-9677, on relaxation of the detrusor muscle: an in vitro study.

OBJECTIVES: To examine the relaxant effects of AJ-9677, a novel beta(3)-adrenoceptor agonist, on the isolated rat, monkey and human detrusor muscle. METHODS: The isolated detrusor strips of rats, monkeys and humans were mounted in organ baths containing Krebs solution. By the cumulative addition of beta-adrenoceptor agonists (isoproterenol, AJ-9677, CL 316,243 and salbutamol in rats; isoproterenol, AJ-9677 and CL 316,243 in monkeys and humans), concentration-relaxation curves were obtained. The maximal relaxation responses and pEC(50) values were calculated. In rats, concentration-relaxation curves to isoproterenol and AJ-9677 were obtained in the presence and absence of propranolol or SR 59230A. RESULTS: Isoproterenol, AJ-9677, CL 316,243 and salbutamol induced concentration-dependent relaxation in rats. The rank order of their relaxing potency in the rat detrusor muscle was AJ-9677 > isoproterenol > CL 316,243 > salbutamol. Isoproterenol and AJ-9677 also produced a concentration-dependent relaxation with high potency in monkeys and humans, whilst CL 316,243 had low relaxing potency. According to the antagonist studies in rats, propranolol and SR 59230A caused a rightward shift of the concentration-relaxation curves to isoproterenol or AJ-9677, respectively. CONCLUSIONS: AJ-9677 has a high relaxant potency on the rat, monkey and human detrusor smooth muscle, and it may have the potential to treat overactive bladder.

Catalytic aerobic oxidation of nor-binaltorphimine (nor-BNI) analogs without 4,5-epoxy bridge affords a more selective ligand for kappa opioid receptor than the representative kappa antagonist nor-BNI.

An analog of nor-binaltorphimine (nor-BNI) without the 4,5-epoxy bridge, 17,17'-bis(cyclopropylmethyl)-6,6',7,7'-tetrahydro-6,6'-imino-14beta,14'alpha-dihydroxy-3,3'-dimethoxy-7,7'-bimorphinan (4), which was the precursor of the designed compound 1 as a selective kappa(3) opioid receptor antagonist, was catalytically oxidized with oxygen in the presence of platinum to give the 5'-oxo derivative 3 with some other oxidized products. Morphinan derivatives without the 4,5-epoxy moiety were labile to oxygen, although the corresponding 4,5-epoxymorphinan derivatives resisted aerobic oxidation. One of the oxidized nor-BNI analogs without 4,5-epoxy bridge, compound 18, showed high affinity and selectivity for kappa opioid receptor.

Stimulatory effects of endogenous and exogenous nitric oxide on gastric acid secretion in anesthetized rats.

We previously reported the stimulatory effect of endogenous nitric oxide (NO) on gastric acid secretion in the isolated mouse whole stomach and histamine release from gastric histamine-containing cells. In the present study, we investigated the effects of endogenous and exogenous NO on gastric acid secretion in urethane-anesthetized rats. Acid secretion was studied in gastric-cannulated rats stimulated with several secretagogues under urethane anesthesia. The acid secretory response to the muscarinic receptor agonist bethanechol (2 mg/kg, s.c.), the cholecystokinin(2) receptor agonist pentagastrin (20 microg/kg, s.c.) or the centrally acting secretagogue 2-deoxy-D-glucose (200 mg/kg, i.v.) was dose-dependently inhibited by the NO synthase inhibitor N(omega)-nitro-L-arginine (L-NNA, 10 or 50 mg/kg, i.v.). This inhibitory effect of L-NNA was reversed by a substrate of NO synthase, L-arginine (200 mg/kg, i.v.), but not by D-arginine. The histamine H(2) receptor antagonist famotidine (1 mg/kg, i.v.) completely inhibited the acid secretory response to bethanechol, pentagastrin or 2-deoxy-D-glucose, showing that all of these secretagogues induced gastric acid secretion mainly through histamine release from gastric enterochromaffin-like cells (ECL cells). On the other hand, histamine (10 mg/kg, s.c.)-induced gastric acid secretion was not inhibited by pretreatment with L-NNA. The NO donor sodium nitroprusside (0.3-3 mg/kg, i.v.) also dose-dependently induced an increase in acid secretion. The sodium nitroprusside-induced gastric acid secretion was significantly inhibited by famotidine or by the soluble guanylate cyclase inhibitor methylene blue (50 mg/kg, i.v.). These results suggest that NO is involved in the gastric acid secretion mediated by histamine release from gastric ECL cells.

Possible pharmacotherapy of the opioid kappa receptor agonist for drug dependence.

Because there are few efficacious medications for drug dependence, many clinical trials are being conducted in earnest to find such medications. Considerable evidence has shown that opioid kappa receptor agonists attenuate several behavioral responses induced by drugs of abuse. Although this raises the possibility that opioid kappa receptor agonists may be useful for the treatment of drug dependence on drugs of abuse, it has been previously reported that treatment with selective opioid kappa receptor agonists causes a psychotomimetic effect and dysphoria both in clinical studies and experimental animal models. As a result, we found the novel opioid kappa receptor agonist TRK-820, another chemical class of opioid kappa receptor agonist that has a morphinan scaffold unlike prototypical opioid kappa receptor agonists, by application of a modified message-address concept. TRK-820 showed high selectivity for an opioid kappa receptor, and strong agonistic activity in both in vitro and in vivo experiments. Like other opioid kappa receptor agonists, TRK-820 could markedly suppress the rewarding effects induced by morphine and cocaine and the discriminative stimulus effect of cocaine. Furthermore, TRK-820 attenuated the mecamylamine-precipitated nicotine-withdrawal aversion in a conditioned place preference paradigm. It is worthwhile to note that unlike prototypical opioid kappa receptor agonists, TRK-820 failed to produce a significant place aversion in rodents at doses that were sufficient to produce significant antinociception. Taken together, these findings indicate that TRK-820 may be useful for the treatment of drug dependence without any aversive effects.

Stimulatory effects of nitric oxide donors on histamine release in isolated rat gastric mucosal cells.

We previously reported stimulatory effects of endogenous and exogenous nitric oxide (NO) on gastric acid secretion. In the present study, we investigated effects of NO donors on release of histamine, which is related to acid secretion, in isolated rat gastric mucosal cells. NO donors such as (+/-)-(E)-4-methyl-2-[(E)-hydroxyimino]-5-nitro-6-methoxy-3-hexanamide (NOR 1) and sodium nitroprusside significantly augmented the histamine release. It was inhibited by 2-(4-carboxyphenyl)-4,4,5,5,-tetramethylimidazoline-1-oxyl-3-amide (carboxy-PTIO), a NO scavenger, and 6-(phenylamino)-5,8-quinolinedione (LY83583), a soluble guanylate cyclase inhibitor. Dibutyryl cyclic GMP also stimulated histamine release. These results suggest that NO donors act on cyclic GMP pathway in isolated gastric mucosal cells, resulting in facilitation of histamine release. NO may stimulate gastric acid secretion through histamine release from the histamine-containing cells, possibly enterochromaffin-like cells.