KW-6002 (Kyowa Hakko Kogyo).

Kyowa Hakko is developing KW-6002, an adenosine A2A receptor antagonist, for the potential treatment of Parkinson's disease (PD) [183211]. The company subsequently began evaluating the compound for depression, and in June 2000 initiated a phase II trial for this indication. Good results have been obtained in a preclinical depression model and Kyowa Hakko hopes that KW-6002 will be representative of a new class of antidepressants [376107]. KW-6002 is undergoing phase II trials for PD in Japan [343257] and in Europe, including the UK 1271929], [321641], [402754]. As expected, KW-6002 entered phase II trials for PD in the US in October 1999 [321640], [342643], [360980], [402754]. The drug is of particular interest due to the absence of the involuntary movement adverse effects characteristic of L-DOPA therapy [271929]. Roche was to codevelop KW-6002 with Kyowa in the US and Europe, but withdrew from the development of this drug in April 1999 [321640]. Kyowa will continue with the drug's development in the US [321640]. NDAs are estimated to be filed around the end of 2001 and the drug is expected to be launched in Western Europe during 2002. An NDA is expected to be filed in Japan approximately three to four years later than in Western Europe [271929].

Medicinal chemistry--16th international symposium. 18-22 September 2000, Bologna, Italy.

This meeting was part of a biennial series focusing upon topics at the forefront of medicinal chemistry. There was no single therapeutic focus for the meeting, instead, the lectures, arranged with main lectures taking place in three parallel sessions, were spread over a number of themes relevant to drug discovery. These are highlighted in order of presentation.

Synthesis of novel GABA uptake inhibitors. 4. Bioisosteric transformation and successive optimization of known GABA uptake inhibitors leading to a series of potent anticonvulsant drug candidates.

By bioisosteric transformations and successive optimization of known GABA uptake inhibitors, several series of novel GABA uptake inhibitors have been prepared by different synthetic approaches. These compounds are derivatives of nipecotic acid and guvacine, substituted at the nitrogen of these amino acids by various lipophilic moieties such as diarylaminoalkoxyalkyl or diarylalkoxyalkyl. The in vitro values for inhibition of [(3)H]GABA uptake in rat synaptosomes was determined for each compound, and it was found that the most potent compound from this series, (R)-1-(2-(3,3-diphenyl-1-propyloxy)ethyl)-3-piperidinecarboxyli c acid hydrochloride (29), is so far the most potent parent compound inhibiting GABA uptake into synaptosomes. Structure-activity results confirm our earlier observations, that an electronegative center in the chain connecting the amino acid and diaryl moiety is very critical in order to obtain high in vitro potency. Several of the novel compounds were also evaluated for their ability in vivo to inhibit clonic seizures induced by a 15 mg/kg (ip) dose of methyl 6, 7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate (DMCM). Some of the compounds tested show a high in vivo potency comparable with that of the recently launched anticonvulsant product 6 ((R)-1-(4, 4-bis(3-methyl-2-thienyl)-3-butenyl)-3-piperidinecarboxylic acid).

N-substituted adenosines as novel neuroprotective A(1) agonists with diminished hypotensive effects.

The synthesis and pharmacological profile of a series of neuroprotective adenosine agonists are described. Novel A(1) agonists with potent central nervous system effects and diminished influence on the cardiovascular system are reported and compared to selected reference adenosine agonists. The novel compounds featured are derived structurally from two key lead structures: 2-chloro-N-(1-phenoxy-2-propyl)adenosine (NNC 21-0041, 9) and 2-chloro-N-(1-piperidinyl)adenosine (NNC 90-1515, 4). The agonists are characterized in terms of their in vitro profiles, both binding and functional, and in vivo activity in relevant animal models. Neuroprotective properties assessed after postischemic dosing in a Mongolian gerbil severe temporary forebrain ischemia paradigm, using hippocampal CA1 damage endpoints, and the efficacy of these agonists in an A(1) functional assay show similarities to some reference adenosine agonists. However, the new compounds we describe exhibit diminished cardiovascular effects in both anesthetized and awake rats when compared to reference A(1) agonists such as (R)-phenylisopropyladenosine (R-PIA, 5), N-cyclopentyladenosine (CPA, 2), 4, N-[(1S,trans)-2-hydroxycyclopentyl]adenosine (GR 79236, 26), N-cyclohexyl-2'-O-methyladenosine (SDZ WAG 994, 27), and N-[(2-methylphenyl)methyl]adenosine (Metrifudil, 28). In mouse permanent middle cerebral artery occlusion focal ischemia, 2-chloro-N-[(R)-[(2-benzothiazolyl)thio]-2-propyl]adenosine (NNC 21-0136, 12) exhibited significant neuroprotection at the remarkably low total intraperitoneal dose of 0.1 mg/kg, a dose at which no cardiovascular effects are observed in conscious rats. The novel agonists described inhibit 6, 7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate-induced seizures, and in mouse locomotor activity higher doses are required to reach ED(50) values than for reference A(1) agonists. We conclude that two of the novel adenosine derivatives revealed herein, 12 and 5'-deoxy-5'-chloro-N-[4-(phenylthio)-1-piperidinyl]adenosine (NNC 21-0147, 13), representatives of a new series of P(1) ligands, reinforce the fact that novel selective adenosine A(1) agonists have potential in the treatment of cerebral ischemia in humans.

Synthesis of novel GABA uptake inhibitors. 3. Diaryloxime and diarylvinyl ether derivatives of nipecotic acid and guvacine as anticonvulsant agents.

(3R)-1-[4,4-bis(3-methyl-2-thienyl)-3-butenyl]-3-piperidinecarboxylic acid 1 (tiagabine, Gabitril) is a potent and selective gamma-aminobutyric acid (GABA) uptake inhibitor with proven anticonvulsant efficacy in humans. This drug, which has a unique mechanism of action among marketed anticonvulsant agents, has been launched for add-on treatment of partial seizures with or without secondary generalization in patients >12 years of age. Using this new agent as a benchmark, we have designed two series of novel GABA uptake inhibitors of remarkable potency, using a putative new model of ligand interaction at the GABA transporter type 1 (GAT-1) uptake site. This model involves the postulated interaction of an electronegative region in the GABA uptake inhibitor with a positively charged domain in the protein structure of the GAT-1 site. These two novel series of anticonvulsant agents contain diaryloxime or diarylvinyl ether functionalities linked to cyclic amino acid moieties and were derived utilizing the new model, via a series of design steps from the known 4,4-diarylbutenyl GABA uptake inhibitors. The new compounds are potent inhibitors of [(3)H]-GABA uptake in rat brain synaptosomes in vitro, and their antiepileptic potential was demonstrated in vivo by their ability to protect against seizures induced by the benzodiazepine receptor inverse agonist methyl 4-ethyl-6,7-dimethoxy-beta-carboline-3-carboxylate (DMCM) in mice. From structure-activity studies of these new GABA uptake inhibitors, we have shown that insertion of an ether oxygen in conjugation with the double bond in tiagabine (K(i) = 67 nM) improves in vitro potency by 5-fold to 14 nM.

RSC-SCI--tenth medicinal chemistry symposium. 5-8 September 1999, Churchill College, Cambridge, UK.

This meeting was part of a biennial series focusing upon topics at the forefront of medicinal chemistry. There was no single therapeutic focus for the meeting, but the 24 lectures were spread between various themes: enzyme inhibitors; drug-receptor/ion channel interactions; enabling technologies; and, new topics in drug research. Several of the lectures featured structure-activity relationships of new drugs, outlining the rationale for the selection of drug candidates. It was clear that many pharmaceutical companies now routinely employ in vivo studies of distribution and pharmacokinetics early in the drug discovery process, thereby adding to the traditional criteria of affinity, selectivity and in vivo effect when potential drugs are selected for development. Likelihood of success during later clinical investigation phases is thereby enhanced.

The synthesis of new adenosine A3 selective ligands containing bioisosteric isoxazoles.

The synthesis and purinergic receptor binding of novel adenosine A3 ligands is described. Many selective A3 receptor agonists e.g. N-(3-iodobenzyl)adenosine-5'-methyluronamide (IB-MECA) contain a 4'-ribosylalkylamide moiety. We found that this amide and other 4'-functional groups could be replaced with an isosteric isoxazole, and the target molecules retained potent binding to the recombinant human A3 receptor.

Contrasting effects of adenosine A1 and A2 receptor ligands in different chemoconvulsive rodent models.

The pro- and anticonvulsive properties of selective adenosine A1 and A2 receptor agonists and antagonists were investigated in mice using seizure models involving a specific blockade of adenosine A1 and A2 receptors, modulation of the gamma-aminobutyric acid/benzodiazepine receptor complex or activation with the excitatory amino acid glutamate. The selective adenosine A1 receptor agonists N-cyclopentyladenosine (CPA) and R-N-(phenylisopropyl) adenosine (R-PIA) in doses of 1 and 10 mg/kg i.p. potentiated seizures induced by the selective adenosine A1 receptor antagonist 8-[4-[[[[(2-aminoethyl)amino]carbonyl]methyl]oxy]-phenyl]- 1,3-dipropylxanthine (XAC). Likewise, the selective adenosine A2 receptor agonists N-[(2-methylphenyl)methyl]adenosine (metrifudil) and N-[2-(3,5-dimethoxyphenyl)-2-(2-methylphenyl)ethyl]adenosine (DPMA), in doses of 30 and 100 mg/kg i.p., respectively, potentiated seizures induced by the selective adenosine A2 receptor antagonist 3,7-dimethyl-1-propargylxanthine (DMPX). In contrast, the adenosine A1 and A2 receptor agonists both antagonized seizures induced by methyl-6,7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate (DMCM--an inverse agonist at benzodiazepine receptors) and the adenosine A1 receptor agonists also protected against seizures induced by glutamate. Paradoxically, the selective adenosine A1 receptor antagonist 8-cyclopentyl-1,3-dimethylxanthine (CPT) antagonized DMCM- and pentylenetetrazole-induced seizures. Thus, it appears that adenosine A1 and A2 receptor agonists can be both pro- and anticonvulsive depending on the mechanism of action of the chemoconvulsant used in the seizure model. The findings with CPT suggest that other types of adenosine analogues than agonists may possess anticonvulsive properties.

The synthesis of novel GABA uptake inhibitors. 1. Elucidation of the structure-activity studies leading to the choice of (R)-1-[4,4-bis(3-methyl-2-thienyl)-3-butenyl]-3-piperidinecarboxylic acid (tiagabine) as an anticonvulsant drug candidate.

A series of different synthetic approaches to novel GABA uptake inhibitors are described, leading to examples which are derivatives of nipecotic acid and guvacine, substituted at nitrogen by 4,4-diaryl-3-butenyl or 2-(diphenylmethoxy)ethyl moieties. The in vitro value for inhibition of [3H]-GABA uptake in rat synaptosomes was determined for each compound. It was found that the most potent examples are those having a substituent in an "ortho" position in one or both aromatic/heteroaromatic groups. The majority of the compounds described are structurally related to tiagabine, (R)-1-[4,4-bis(3-methyl-2-thienyl)-3-butenyl]-3- piperidinecarboxylic acid hydrochloride (NNC 05-0328) and some of the reasoning behind the selection of this compound as a drug candidate is summarized.

NNC-711, a novel potent and selective gamma-aminobutyric acid uptake inhibitor: pharmacological characterization.

NNC-711 (1-(2-(((diphenylmethylene)amino)oxy)ethyl)-1,2,5,6-tetrahydro-3- pyridinecarboxylic acid hydrochloride) is a novel, potent and selective gamma-aminobutyric acid (GABA) uptake inhibitor. NNC-711 inhibited synaptosomal (IC50 = 47 nM), neuronal (IC50 = 1238 nM) and glial (IC50 = 636 nM) GABA uptake in vitro NNC-711 lacked affinity for other neurotransmitter receptor binding sites, uptake sites and ion channels examined in vitro. In vivo, NNC-711 was a potent anticonvulsant compound against rodent seizures induced by methyl 6,7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate (DMCM) (ED50 (clonic) = 1.2 mg/kg i.p.), pentylenetetrazole (PTZ) (ED50 (tonic) = 0.72 mg/kg i.p., mouse; and ED50 (tonic) = 1.7 mg/kg, rat), or audiogenic (ED50 (clonic and tonic) = 0.23 mg/kg i.p.). At higher doses NNC-711 produced behavioral side effects characterized by inhibition of traction (ED50 = 23 mg/kg i.p.), rotarod (ED50 = 10 mg/kg i.p.) and exploratory locomotor activity (ED50 = 45 mg/kg i.p.) in the mouse. Following acute (3-h) in vivo pretreatment with NNC-711, behavioral tolerance developed to its motor impairing side effects (inhibition of traction, rotarod or exploratory locomotor activity) without corresponding tolerance to the anticonvulsant effects. These data suggest that NNC-711 will be useful for future in vitro and in vivo experiments to elucidate the role of the GABA uptake carrier in the central nervous system.

In vivo labeling of the central GABA uptake carrier with 3H-Tiagabine.

The in vivo binding of 3H-Tiagabine to the central GABA uptake carrier in mouse brain was characterized. 3H-Tiagabine in vivo bound to a single class of binding sites with a Kd = 72.5 nM and a Bmax = 640 pmol/g tissue. 3H-Tiagabine binding in vivo was regionally distributed within the CNS, and showed a good correlation with 3H-Tiagabine binding in vitro. Pharmacological characterization of 3H-Tiagabine binding in vivo revealed a binding site exhibiting specificity for GABA uptake inhibitors. Experiments examining the in vivo receptor occupancy of the GABA uptake carrier for a series of GABA uptake inhibitors revealed that 20-30% of the GABA uptake sites were occupied at the ED50 for inhibiting DMCM-induced clonic convulsions, while a 50-62% receptor occupancy in vivo was needed to inhibit rotarod performance. These data suggest that 3H-Tiagabine in vivo binding may be a useful method for assessing GABA uptake inhibitor penetration into the CNS, and may be a useful tool for studying the physiological regulation of the GABA uptake carrier.

Characterization of tiagabine (NO-328), a new potent and selective GABA uptake inhibitor.

Tiagabine (NO-328) (R(-)-N-[4,4-bis(3-methylthien-2-yl)but-3-enyl]nipecotic acid, hydrochloride) is a new centrally acting GABA uptake inhibitor. The anticonvulsant activity of tiagabine was evaluated against seizures induced by methyl 6,7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate (DMCM), pentylenetetrazol, bicuculline, maximal electrostimulation (MES), or high intensity sound. The sedative actions of tiagabine were evaluated in tests for traction, rotarod performance and exploratory behavior. Finally, interoceptive properties of tiagabine were assessed using diazepam-, CGS 9896-, pentylenetetrazol-, or amphetamine-discriminating rats. Tiagabine was an effective anticonvulsant in doses which did not produce sedation or motor debilitation, although it was not potent against MES. In a manner similar to other anti-epileptic drugs, tiagabine potentiated dopaminergic function (methylphenidate-induced gnawing in mice) although it did not substitute for amphetamine in amphetamine-trained animals. Furthermore, although tiagabine antagonized DMCM-induced convulsions, it exhibited neither CGS 9896 or diazepam-like interoceptive effects, nor did it block (or potentiate) pentylenetetrazol-discrimination. Thus, GABA uptake inhibition represents a novel rationale for a valproate-like anticonvulsant drug therapy.

(R)-N-[4,4-bis(3-methyl-2-thienyl)but-3-en-1-yl]nipecotic acid binds with high affinity to the brain gamma-aminobutyric acid uptake carrier.

(R)-N-[4,4-Bis(3-methyl-2-thienyl)but-3-en-1-yl]nipecotic acid (NO 328) has previously been shown to be a potent anticonvulsant in both mice and rats. Here, we report that NO 328 is a potent inhibitor of gamma-[3H]aminobutyric acid [( 3H]GABA) uptake in a rat forebrain synaptosomal preparation (IC50 = 67 nM) and in primary cultures of neurons and astrocytes. Inhibition of [3H]GABA uptake by NO 328 is apparently of a mixed type when NO 328 is preincubated before [3H]GABA uptake; the inhibition is apparently competitive without preincubation. NO 328 itself is not a substrate for the GABA uptake carrier, but NO 328 is a selective inhibitor of [3H]GABA uptake. Binding to benzodiazepine receptors, histamine H1 receptors, and 5-hydroxytryptamine1A receptors was inhibited by NO 328 at 5-30 microM, whereas several other receptors and uptake sites were unaffected. [3H]NO 328 showed saturable and reversible binding to rat brain membranes in the presence of NaCl. The specific binding of [3H]NO 328 was inhibited by known inhibitors of [3H]GABA uptake; GABA and the cyclic amino acid GABA uptake inhibitors were, however, less potent than expected. This indicates that the binding site is not identical to, but rather overlapping with, the GABA recognition site of the uptake carrier. The affinity constant for binding of [3H]NO 328 is 18 nM, and the Bmax is 669 pmol/g of original rat forebrain tissue. The regional distribution of NaCl-dependent [3H]NO 328 binding followed that of synaptosomal [3H]GABA uptake.(ABSTRACT TRUNCATED AT 250 WORDS)

Synthesis and antiviral properties of 5-(2-substituted vinyl)-6-aza-2'-deoxyuridines.

The following 5-(2-substituted vinyl)-6-aza-2'-deoxyuridines were synthesized: (E)-5-(2-bromovinyl) (2) (6-aza-BVDU), 5-(2-bromo-2-fluorovinyl) (a mixture of E and Z isomers) (3), (E)-5-(2-chlorovinyl) (4), (E)-5-[2-(methylthio)vinyl] (5), 5-(2,2-dibromovinyl) (6), and 5-(3-furyl) (7). The synthesis of 2-6 utilized Wittig-type reactions on 5-formyl-1-(2'-deoxy-3', 5'-di-O-p-toluoyl-beta-D-erythro-pentofuranosyl)-6-azauracil (16). 6-Aza-BVDU (and its alpha-anomer) was also synthesized from (E)-5-(2-bromovinyl)-6-azauracil (12) by using standard deoxyribosidation methodology. Compound 7 was prepared from 5-(3-furyl)-6-azauracil (33) via a ribosidation/deoxygenation sequence. An attempt to prepare the corresponding 5-(2,2-difluorovinyl) analogue afforded instead a mixture of the 5-[(2,2-difluoro-2-methoxy)ethyl] and 5-(2,2,2-trifluoroethyl) derivatives 29 and 30. Compounds 2-7, 29, and 30 were tested for in vitro activity against herpes simplex virus types 1 and 2 (HSV-1, HSV-2). 6-Aza-BVDU (2) exhibited ID50s of 8 micrograms/mL vs. HSV-1 and 190 micrograms/mL vs. HSV-2. BVDU (1) had ID50s of 0.015 and 1.6 micrograms/mL against HSV-1 and HSV-2, respectively. Compound 4 showed a similar profile of activity, but the other analogues were either weakly active or inactive.