Thioxanthene psychopharmacological agents. I. 9-(3-aminopropyl)thioxanthene-2-sulfonamides.
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We have previously shown that phenothiazines sensitize multidrug resistant (MDR) cells to chemotherapeutic drugs in a manner related to specific structural features, and have identified structurally related thioxanthenes with increased anti-MDR activity. We have now studied the structure-activity relationships of 16 thioxanthenes in the human breast cancer line MCF-7 AdrR. trans-Thioxanthene stereoisomers were 2- to 7-fold more potent than cis-thioxanthenes for antagonizing MDR. The most potent thioxanthenes possessed a halogenated tricyclic ring connected by a 3-carbon alkyl bridge to a piperazinyl or piperadinyl side group. The chemosensitizing effects of the lead compound, trans-flupenthixol, its stereoisomer cis-flupenthixol, its phenothiazine homologue fluphenazine, and the calcium channel blocker verapamil, were further studied in a series of sensitive and MDR cell lines. trans-Flupenthixol caused a greater reversal of cellular resistance to doxorubicin, vinblastine, vincristine, and colchicine in MCF-7 AdrR, KB-V1, and P388/DOX MDR cells than the other chemosensitizers. In particular, trans-flupenthixol was 2- to 3-fold more potent for reversing MDR than equimolar concentrations of verapamil. Furthermore, trans-flupenthixol fully reversed resistance to doxorubicin, vincristine, and colchicine in MDR MCF-7 and NIH 3T3 cells transfected with the mdr1 gene. None of these agents altered MDR in a non-P-glycoprotein expressing MCF-7 cell line selected with mitoxantrone, nor in any of the parental cell lines. The stereoselective antagonism of the flupenthixol isomers on several putative cellular targets was studied to explore the mechanism of their chemosensitizing activity. cis- and trans-flupenthixol were equally active inhibitors of protein kinase C and calmodulin. Both cis- and trans-flupenthixol were also potent inhibitors of [3H]azidopine binding to P-glycoprotein. The apparent lack of clinical toxicity of trans-flupenthixol makes it an attractive drug for possible use in the modulation of tumor resistance in vivo if appropriate tissue concentrations can be achieved.
The aim of the present investigation was to illustrate the antibacterial effect of various phenothiazine and thioxanthene derivatives on mycobacteria in vitro. It was demonstrated that clopenthixol is about twice as potent as chlorpromazine (CPZ) and levomepromazine-maleate is about half as potent as CPZ, measured by the inhibitory effect on the growth of the mycobacterial strains. Measured in the same way the stereoisomeric compounds of flupenthixol are shown to be more potent than the stereo-isomeric compounds of clopenthixol and chlorprothixen. The two last-named compounds are equal in potency. The stereo-isomeric analogs of the thioxanthene derivatives are equal in antibacterial potency against the slow-growing mycobacteria. The mycobacterial strains investigated show no difference in sensitivity between the cis (Z)--and and trans (E)--compounds of the thioxanthenes. It seems particularly promising that also the more resistant mycobacteria other than Mycobacterium tuberculosis, e.g. M. avium and M. intracellulare, are sensitive in the concentration range investigated. Considered as a whole, these results might be a stimulus to investigate the antimicrobial effect of the thioxanthenes in vivo.
Some neuroleptic drugs of the phenothiazine and thioxanthene groups have an antimicrobial effect in vitro. This is also true for neuroleptically inactive stereo-isomeric analogs of the thioxanthenes e.g. trans(E)-clopenthixol (t-CPT). In a murine pneumococcus peritonitis model t-CPT demonstrated a slight, but non-significant antibacterial effect in doses of 0.3-0.9 mg per mouse, while higher doses seemed to enhance the bacterial virulence. If combined with subtherapeutic doses of penicillin, a significantly higher survival rate was obtained compared with either drug given alone. In vitro studies demonstrated a similar synergistic effect. These results indicate that at least one non-neuroleptic thioxanthene stereo-isomer has an antibiotic potential also in vivo. The mechanism of action is not known.
A series of thioxanthenes was tested for cytotoxicity to isolated rat hepatocytes, as measured by the loss of an intracellular enzyme (GOT) to the surrounding medium. The relative order of potency was found to be: SKF 10812 greater than cis- = trans-chlorprothixene = N-756A greater than cis- = trans-flupenthixol greater than xanthiol greater than methixene = cis- = trans-clopenthixol = N-716 greater than N-710. The presence of an unsaturated exocyclic bond increased the apparent toxicity as did the presence of a substituent (trifluoromethyl, chlorine, bromine) at the two position of the tricyclic nucleus. The trifluoromethyl substituted thioxanthenes were three to four times more potent than their halogenated analogs, but there were no differences in potency among the halogenated (chlorine or bromine) thioxanthenes. Compounds which had a dimethylaminopropylidene side chain were five to six times stronger in causing enzyme leakage than were their analog which had a hydroxyethylpiperazinylpropylidene side chain. Although only the cis-isomers of each compound are highly active neuroleptics, both isomers were equipotent at causing the efflux of GOT from rat hepatocytes.
Benzamides or thioxanthenes were tested as potential antagonists of the cyclic AMP accumulation induced by 10(-4) M dopamine in intact rabbit retinae in vitro in the presence of 5 to 7 mM theophylline. The neuroleptic sulpiride (10(-4) M) was found to be totally inactive whereas a substituted benzamide (clebopride) had small but significant antagonist effect at the same concentration. Among thioxanthenes, isomers of cisconfiguration, which are potent neuroleptics, completely inhibit the cyclic AMP accumulation induced by dopamine, in contrast to trans-isomers which had no inhibitory effects. These data would confirm that retina in vitro is another suitable model for screening antipsychotic activity of classical neuroleptics and that the mechanism of action of sulpiride still needs further investigation.
The present study establishes correlations of in vivo growth inhibition of a solid tumor, pancreatic ductal adenocarcinoma (Panc03), of mice with the steric and electrostatic fields and the hydrophobic parameter log P of a series (32) of 1-[[2-(dialkylamino)alkyl]amino]- 9H-thioxanthen-9-ones by the 3D-QSAR method comparative molecular field analysis (CoMFA). The template molecular model was hycanthone methanesulfonate (19), the structure of which had been established previously by X-ray crystallography. The hycanthone base is protonated at the terminal nitrogen N(2), and an intramolecular hydrogen bond is present between the proximal nitrogen N(1) and carbonyl oxygen O(1) atoms. Crystallographic data also indicate a planar arrangement of bonds around N(1). However, the molecular geometry of 19, optimized by semiempirical molecular orbital methods (PM3, MNDO, AM1), showed the expected trigonal-pyramidal configuration for N(1). A comparison of MO and ab initio methods applied to a model compound, 1-amino-9H-thioxanthen-9-one, led to the selection of PM3 as the method for full geometry optimization of first the cationic and then the neutral forms of 1-32, whereas AM1 provided atomic charges for these same structures save those incorporating a sulfonamide moiety (5, 7, 20, 25, 26, 29, 31, and 32). Acceptable values for the latter were obtained from ab initio calculations. Structures were aligned by minimizing root-mean-square (rms) differences in the fitting of structures to 19 using the FIT option of SYBYL. An alternative strategy of alignment, steric and electrostatic alignment (SEAL), was invoked to provide a comparison of statistical data generated with the rms alignment. The rms-fit alignment of structures produced slightly better cross-validated and conventional r2 values than those generated with the SEAL method. In addition, the rms-fit data indicate that a shift in the lattice of one-half of its spacing has a much smaller effect on the CoMFA data for a lattice of 1 A than one of 2 A. Inclusion of log P in a CoMFA of the neutral structures effected a small (ca. 8-10%) but significant improvement in cross-validated r2 values. The relative contributions of the hydrophobic effects and the steric and electrostatic fields to the conventional r2 values were 16%, 42%, and 42%, respectively. By contrast, incorporation of frontier molecular orbital (HOMO and LUMO) energies or their gaps in the PLS analyses failed to enhance correlation coefficients derived for either the charged or uncharged compounds.(ABSTRACT TRUNCATED AT 400 WORDS)
Conformational analyses have been performed on several phenothiazine and thioxanthene dopamine antagonists using the MM2-87 program and parameter set. The compounds that were examined are thioridazine (2), methotrimeprazine (3), cis- and trans-chlorprothixene, and a piperidylidene derivative of chlorprothixene. In addition, (+)-2 and (-)-3 were determined by X-ray crystallography to have the R absolute configuration. The above compounds were superimposed onto loxapine, which was used as a template for the previously proposed dopamine D2 receptor ligand model. The conformational properties and receptor affinities of these compounds were found to be entirely consistent with the ligand model. For example, a conformer of (+)-R-2 that is consistent with the ligand model is lower in energy than a consistent conformer for (-)-S-2, which agrees with the higher D2 receptor affinity of the former. Similarly, in agreement with the much higher affinity of (-)-R-3 relative to (+)-S-3, only the former contains a low energy conformer consistent with the ligand model. The ligand model is also consistent with the greater potency of cis-thioxanthenes over the trans isomers. These results emphasize the importance of the correct orientation of the ammonium hydrogen for high affinity at the D2 receptor. The pharmacophore for D2 receptor ligands is compared with a recently proposed pharmacophore for D1 ligands.
The hitherto existing investigations on the placental transfer of psycholeptic drugs mostly do not answer the question whether the active compounds themselves or their metabolites or both get into the fetus. As published informations on this problem partly are contradictory the placental transfer of psycholeptic drugs was investigated with the thioxanthenes flupentixol and chlorprothixen for examples. After oral application to rats on the 15th and 20th days of gestation the intact thioxenthenes themselves as well as their sulfoxides and desalkylated metabolites were detectable in placenta, uterus and fetus. The last mentioned substances and the intact thioxanthenes were determined quantitatively. The concentration (mug/g tissue) in the fetus is lower than in uterus and placenta. The results are discussed.
Total fatty acids were analysed in thrombocytes of schizophrenic patients treated with a "high dose" or "low dose" monotherapy of neuroleptic drugs phenothiazine or thioxanthene. The ratio of the very long chain fatty acid hexacosanoic acid to the long chain fatty acid docosanoic acid (C26:0/C22:0) increased in the "high dose" and "low dose" groups as compared to healthy untreated controls (P less than 0.05). The polyunsaturated fatty acid arachidonic acid decreased in the "high" and "low dose" groups (P less than 0.01 and P less than 0.05). The polyunsaturated fatty acids alpha-linolenic acid, eicosapentaenoic acid and docosahexaenoic acid were not detectable in most of the "high dose" schizophrenic patients, however, they were found in the "low dose" group and in the controls. There was a negative correlation between the daily dosage of phenothiazine and the percentages of the polyunsaturated fatty acids arachidonic acid and alpha-linolenic acid+eicosapentaenoic acid+docosahexaenoic acid in thrombocytes (r = -0.87, P less than 0.01 and r = -0.81, P less than 0.01). Two patients of the "high dose" group with an especially high and long lasting monotherapy of neuroleptics were nearly devoid of polyunsaturated fatty acids in their thrombocytes. Untreated schizophrenic patients exhibited a fatty acid pattern in their thrombocytes not markedly different from that of the healthy untreated control group. We conclude that neuroleptic drugs phenothiazine or thioxanthene can alter the fatty acid pattern of thrombocytes.
A series of new N-(9H-xanthen-9-yl)aminoalkanamide and N-(9H-thioxanthen-9-yl)aminoalkanamide derivatives was synthesized and evaluated as potential intercalators by measuring their DNA binding affinity. They were also tested for cytotoxic activity against L1210. The results suggest that the cytotoxicity of these molecules was not due to an intercalating mechanism.
A simple and rapid colorimetric method for the quantitative determination of the thioxanthene derivatives, chlorprothixene, tiotixene and metixene has been performed either in their pure form or in tablets. The procedure is based upon the formation of charge transfer complexes with the pi-acceptor tetracyanoethylene. The spectra of the complex show maxima at 415, 410 and 390 nm with a high apparent molar absorptivity which facilitates the determination of 5-100 micrograms X ml-1 of the studied compounds. The mean recoveries are 100.1 +/- 1.4%, 99.8 +/- 0.8% and 100.2 +/- 1.1% for chlorprothixene, tiotixene and metixene, respectively. This procedure is applied to determine these drugs in certain formulations and the results compare favourably to compendial methods.
Antisera have been raised in rabbits to the immogen 2-trifluoromethylphenothiazine-10-beta-propionate bovine serum albumin. An [125I]-labelled tyrosine methyl ester derivative of the immunogen precursor has been synthesised and used with the antisera to develop a simple, precise and sensitive radioimmunoassay for phenothiazines and thioxanthenes bearing 2-trifluoromethyl substituents. The assay can detect 0.4 ng/ml of fluphenazine, trifluorperazine or (Z)-flupenthixol in 100 microliter of human serum without interference from their sulphoxide or 7-hydroxylated metabolites. An acceptable correlation between this assay and an established fluphenazine radioimmunoassay using commercial [3H]fluphenazine has been obtained for plasma samples.
An assay strategy for determining a wide range of phenothiazine, thioxanthene and butyrophenone neuroleptics and antihistamines both alone and in combination in blood and plasma is described. The general method employs liquid chromatography with both conventional and radial compression nitrile bonded columns. Detection is by ultraviolet absorption spectrophotometry or by amperometry depending on the concentrations to be measured. Ultraviolet absorption is suitable down to 10 ng/ml. Below this level amperometry is preferable. The various compounds are used as internal standards for each other. The lower limit of detection is approximately 0.1 ng ml-1 with 10-ml sample. The with-run coefficient of variation is a maximum of 7.3%.
A review with 92 references is presented that deals with the reported methods of analysis of the thioxanthene derivatives of pharmaceutical interest. The review includes the methods adopted in dosage forms and biological fluids. A brief discussion of the metabolism and pharmacokinetics of this class of compounds is also reported.
A new thioxanthene derivative, teflutixol (Lu 10-022) has been administered for 4 weeks to 21 patients [12 schizophrenics, 6 patients with obsessive, compulsive neurosis (OCN), 2 patients with affective psychosis (AP), and one patient with paranoic reactions (PR)]. The maximum daily dose varied between 0.5 mg and 4 mg administered once in the morning. Fifteen of the patients received 1 mg or less daily. Based upon weekly assessments by the BPRS as well as a global evaluation all 4 groups showed a clear amelioration of the scores, and for both the schizophrenics and the patients with OCN this was highly significant [student's t (p less than 0.001)].
Flupenthixol, a new thioxanthene derivative, was studied for its effects on gastric secretion and gastric ulcers in rats. The compound diminished the volume of gastric secretion, decreased total acid output and protected the glandular gastric mucosa. The observations may be of clinical significance.
This study was designed to evaluate some of the effects of a new thioxanthene, thiothixene (P-4657B), in 20 male schizophrenic patients recently admitted to Bellevue Hospital. The results of a dosage range trial indicated that at a dosage of approximately 50 mg per day, toxic and side effects as well as therapeutic effects were at their maximum. Parkinsonian reactions (in 17 of 20 patients) with restlessness and akathisia were the most prominent of these effects. Also, activation of psychopathology was observed in six of 20 subjects. Thiothixine did exhibit some antipsychotic activity, but it does not appear to be as valuable as it has been reported to be in chronic schizophrenic patients.