3-[[(Aryloxy)alkyl]piperidinyl]-1,2-benzisoxazoles as D2/5-HT2 antagonists with potential atypical antipsychotic activity: antipsychotic profile of iloperidone (HP 873).

A series of 3-[[(aryloxy)alkyl]piperidinyl]-1,2-benzisoxazoles was synthesized and evaluated as potential antipsychotic D2/5-HT2 antagonists. Most of these compounds showed potent antipsychotic-like activity in an apomorphine-induced climbing mouse paradigm, with many also showing preferential mesolimbic activity, as indicated by their weaker effects in an apomorphine-induced stereotypy model. In receptor binding assays, many displayed a moderate affinity for the D2 receptor coupled with a significantly greater affinity for the 5-HT2 receptor: a property that has been suggested as necessary for atypicality. From this series, compound 45, 1-[4-[3-[4-(6-fluoro-1,2-benzisoxazol-3-yl)-1- piperidinyl]propoxy]-3-methoxyphenyl]ethanone (iloperidone, HP 873), was further evaluated in a battery of in vivo and in vitro assays. This compound showed a 300-fold greater potency in inhibition of climbing than in inhibition of stereotypy or induction of catalepsy, and when evaluated chronically in an electrophysiological model, 45 caused a depolarization blockade of dopamine neurons in the A10 area of the rat brain but not in the A9 area. Additionally, it showed positive activity in a social interaction paradigm, suggesting potential efficacy against asociality, a component of the negative symptoms of schizophrenia. In chronic ex vivo studies, 45, similar to clozapine, caused a down regulation of 5-HT2 receptors but had no effect on the number of D2 receptors. Compound 45 is currently undergoing clinical evaluation.

Synthesis and neuroleptic activity of 3-(1-substituted-4-piperidinyl)-1,2-benzisoxazoles.

The synthesis of a series of 3-(1-substituted-4-piperidinyl)-1,2-benzisoxazoles is described. The neuroleptic activity of the series was evaluated by utilizing the climbing mice assay and inhibition of [3H]spiroperidol binding. Structure-activity relationships were studied by variation of the substituent on the benzisoxazole ring with concomitant variation of four different 1-piperidinyl substituents. Maximum neuroleptic activity was realized when there was a 6-fluoro substituent on the benzisoxazole ring. The 1-piperidinyl substituent appeared less significant, although in most cases, the (1,3-dihydro-2-oxo-2H-benzimidazol-1-yl)propyl group imparted maximum potency. The most potent compound in both assays was 6-fluoro-3-[1-[3-(1,3-dihydro-2-oxo-2H-benzimidazol-1-yl) propyl]-4-piperidinyl]-1,2-benzisoxazole (11b).

3-(1-Indolinyl)benzylamines: a new class of analgesic agents.

An extensive series of 3-(1-indolinyl)benzylamines and related compounds was synthesized and tested for analgesic activity. After a detailed study of structure-activity relationships, 3-(1-indolinyl)benzylamine (2b) was selected for further investigation as the most interesting member of this novel class of compounds. It was active in both the phenylquinone writhing and tail-flick assays for analgesic activity. No motor deficits were observed in the rotorod test, and 2b was found to be free of any other effects on the central nervous system. The compound did not bind to opiate receptors, since it was inactive in inhibiting the stereospecific binding of [3H]naloxone in rat brain homogenates. Thus, 3-(1-indolinyl)benzylamine represents a novel analgesic with an unusual chemical structure and biological profile.

Novel tetracyclic spiropiperidines. 4. Synthesis and pharmacological evaluation of spiro- and 6,7-dihydrospiro[benzo[b]pyrrolo[3,2,1-jk][1,4]benzodiazepine-2 (1H),4'-piperidine]s.

A previously described series of 1-arylspiro[indoline-3,4'-piperidine]s was reported by us to possess significant antidepressant properties. This biological activity was found to be at a maximum among those compounds bearing an ortho substituent (e.g., NH2 as in 1) in the pendant aryl ring. In order to explore further this "ortho effect", we synthesized cyclic analogues of type 3 and 4 in which the position of the o-NH2-substituted aryl group is conformationally restricted and defined. When tested for antidepressant activity by tetrabenazine ptosis prevention in mice, it was found that restriction of rotation of the pendant o-aminophenyl group in these rigid analogues resulted in a loss of antidepressant properties. However, analgesic activity was retained and even improved by this molecular constraint.

Novel tetracyclic spiropiperidines. 3. 1-arylspiro[indoline-3,4'-piperidine]s as potential antidepressants.

A series of 1-arylspiro[indoline-3,4'-piperidine]s was synthesized and evaluated for potential antidepressant activity by tetrabenazine (TBZ) ptosis prevention and potentiation of 5-hydroxytryptophan (5-HTP) induced head twitching in pargyline-pretreated rats. Marked TBZ activity was observed with analogues bearing an ortho substituent on the pendant aromatic ring, as exemplified by lead compound 25a, 1-(2-chlorophenyl)spiro[indoline-3,4'-piperidine], which was also very active in potentiating 5-HTP stereotypy and yohimbine toxicity, as well as in inhibiting the muricidal behavior in rats. The potent in vivo activity of 25a, coupled with weak to moderate in vitro activity with respect to the blockade of neuronal reuptake of biogenic amines, seems to suggest a profile atypical of tricyclic antidepressants.

7-(Aminoacyl) and 7-(aminoalkyl) derivatives of 1,2,6,7-tetrahydroindolo[1,7-ab][1,5]benzodiazepines as potential antidepressant agents.

The synthesis of 7-(aminoacyl) and 7-(aminoalkyl) derivatives of 1,2,6,7-tetrahydroindolo[1,7-ab][1,5]benzodiazepines is described. These compounds were evaluated for antidepressant activity by their ability to inhibit tetrabenazine-induced ptosis in mice. Many compounds were found to be active in this animal model, and structure-activity relationships are discussed. Two analogues in particular, one from the 7-(aminoacyl) series (13) and one from the 7-(aminoalkyl) series (26), were of comparable potency to the antidepressant drugs desipramine and amitriptyline.

Synthesis and evaluation for diuretic activity of 1-substituted 6-chloro-5-sulfamylindolines.

The synthesis of a series of 1-substituted 6-chloro-5-sulfamylindolines is described. In the Lipschitz test for diuretic activity, two of the compounds showed significant excretion of urine and sodium and were approximately equivalent in potency to chlorothiazide but with a later onset of activity.

Synthesis and evaluation of 3-substituted 1-[4-(2-indol-3-ylethyl)piperazinyl]ureas as potential antihypertensive agents.

A series of 3-substituted 1-[4-(2-indol-3-ylethyl)piperazinyl]ureas was synthesized and screened for antihypertensive activity in spontaneously hypertensive rats. Two compounds with aryl urea substituents were very potent and lowered blood pressure 55 mm or more at oral doses of 100 mg/kg. However, both compounds failed to produce a cardiovascular response in the normotensive dog.

Synthesis of 3-(4-acylaminopiperazin-1-ylalkyl)indoles as potential antihypertensive agents.

A series of 3-(4-acylaminopiperazin-1-ylalkyl)indoles was synthesized and tested for antihypertensive activity. Compounds with no substituents in the indole portion of the molecule were generally most effective in lowering blood pressure in the spontaneous hypertensive rat model. Of these several analogues were very potent and lowered blood pressure more than 55 mmHg at oral doses of 100 mg/kg.