pafuramidine and Disease-Models--Animal

Dicationic 2,6-diphenylpyrazines, aza-analogues and prodrugs were synthesized; evaluated for DNA affinity, activity against Trypanosoma brucei rhodesiense (T. b. r.) and Plasmodium falciparum (P. f.) in vitro, efficacy in T. b. r. STIB900 acute and T. b. brucei GVR35 CNS mouse models. Most diamidines gave poly(dA-dT)2 ΔTm values greater than pentamidine, IC50 values: T. b. r. (4.8-37nM) and P. f. (10-52nM). Most diamidines and prodrugs gave cures for STIB900 model (11, 19a and 24b 4/4 cures); 12 3/4 cures for GVR35 model. Metabolic stability half-life values for O-methylamidoxime prodrugs did not correlate with STIB900 results.

Topics: Animals; Antiprotozoal Agents; Aza Compounds; Cations; Cell Line; Cell Survival; Disease Models, Animal; Mice; Myoblasts; Parasitic Sensitivity Tests; Pentamidine; Plasmodium falciparum; Poly dA-dT; Prodrugs; Pyrazines; Rats; Structure-Activity Relationship; Transition Temperature; Trypanosoma brucei rhodesiense; Trypanosomiasis, African

Novel dicationic triazoles 1-60 were synthesized by the Pinner method from the corresponding dinitriles, prepared via the copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC). The type and the placement of cationic moieties as well as the nature of aromatic substituents influenced in vitro antiprotozoal activities of compounds 1-60 against Trypanosoma brucei rhodesiense, Plasmodium falciparum, and Leishmania donovani and their cytotoxicity for mammalian cells. Eight congeners displayed antitrypanosomal IC(50) values below 10 nM. Thirty-nine dications were more potent against P. falciparum than pentamidine (IC(50) = 58 nM), and eight analogues were more active than artemisinin (IC(50) = 6 nM). Diimidazoline 60 exhibited antiplasmodial IC(50) value of 0.6 nM. Seven congeners administered at 4 x 5 mg/kg by the intraperitoneal route cured at least three out of four animals in the acute mouse model of African trypanosomiasis. At 4 x 1 mg/kg, diamidine 46 displayed better antitrypanosomal efficacy than melarsoprol, curing all infected mice.

Topics: Amidines; Animals; Antiprotozoal Agents; Cell Line; Cell Survival; Disease Models, Animal; Female; Leishmania donovani; Mice; Molecular Structure; Parasitic Sensitivity Tests; Plasmodium falciparum; Rats; Stereoisomerism; Structure-Activity Relationship; Triazoles; Trypanosoma brucei rhodesiense

Seven novel diamidino 2,5-bis(aryl)thiazoles (5a-g) were synthesized and evaluated against Trypanosoma brucei rhodensiense (T. b. r.) and Plasmodium falciparum (P. f.). The diamidines were obtained directly from the corresponding bis-nitriles (4a-g) by the action of lithium bis(trimethylsilyl)amide. The bis-nitriles 4a-f were synthesized in four steps starting with the Stille coupling of 2-tributyltinthiazole with the appropriate cyanoaryl halide. The bis-nitrile 5g was obtained by the palladium facilitated coupling of the mixed tin-silyl reagent 2-trimethylsilyl-5-trimethyltinthiazole with 2-bromo-5-cyanopyridine. The amidoxime potential prodrugs 6a-e, 6g were obtained by the reaction of hydroxylamine with the bis-nitriles. O-Methylation of the amidoximes gave the corresponding N-methoxyamidines 7a-c, 7e, 7g. The diamidines showed strong DNA binding affinity as reflected by DeltaT(m) measurements. Four of the diamidines 5a, 5b, 5d and 5e were highly active in vitro against P. f. giving IC(50) values between 1.1 and 2.5nM. The same four diamidines showed IC(50) values between 4 and 6nM against T. b. r. The selectivity indices ranged from 233 to 9175. One diamidine 5a produced one of four cures at an ip dose of 4x5mg/kg in the STIB900 mouse model for acute African trypanosomiasis. The amidoxime and N-methoxyamidine of 5a were the only produgs to provide cures (1/4 cures) in the same mouse model on oral dosage at 4x25mg/kg.

Topics: Administration, Oral; Animals; Antimalarials; Antiprotozoal Agents; Disease Models, Animal; DNA, Protozoan; Drug Stability; Malaria, Falciparum; Mice; Parasitic Sensitivity Tests; Pentamidine; Plasmodium falciparum; Rats; Stereoisomerism; Structure-Activity Relationship; Thiazoles; Trypanocidal Agents; Trypanosoma brucei brucei; Trypanosomiasis, African

Owing to the lack of oral drugs for human African trypanosomiasis, patients have to be hospitalized for 10 to 30 days to facilitate treatment with parenterally administered medicines. The efficacy of a novel orally administered prodrug, 2,5-bis(4-amidinophenyl)-furan-bis-O-methlylamidoxime (pafuramidine, DB289), was tested in the vervet monkey (Chlorocebus [Cercopithecus] aethiops) model of sleeping sickness. Five groups of three animals each were infected intravenously with 10(4) Trypanosoma brucei rhodesiense KETRI 2537 cells. On the seventh day postinfection (p.i.) in an early-stage infection, animals in groups 1, 2, and 3 were treated orally with pafuramidine at dose rates of 1, 3, or 10 mg/kg of body weight, respectively, for five consecutive days. The animals in groups 4 and 5 were treated with 10 mg/kg for 10 consecutive days starting on the 14th day p.i. (group 4) or on the 28th day p.i. (group 5), when these animals were in the late stage of the disease. In the groups treated in the early stage, 10 mg/kg of pafuramidine completely cured all three monkeys, whereas lower doses of 3 mg/kg and 1 mg/kg cured only one of three and zero of three monkeys, respectively. Treatment of late-stage infections resulted in cure rates of one of three (group 4) and zero of three (group 5) monkeys. These studies demonstrated that pafuramidine was orally active in monkeys with early-stage T. brucei rhodesiense infections at dose rates above 3 mg/kg for 5 days. It was also evident that the drug attained only minimal efficacy against late-stage infections, indicating the limited ability of the molecule to cross the blood-brain barrier. This study has shown that oral diamidines have potential for the treatment of early-stage sleeping sickness.

Topics: Administration, Oral; Animals; Benzamidines; Chlorocebus aethiops; Disease Models, Animal; Dose-Response Relationship, Drug; Female; Male; Pentamidine; Prodrugs; Random Allocation; Time Factors; Treatment Outcome; Trypanocidal Agents; Trypanosoma brucei rhodesiense; Trypanosomiasis, African

The synthesis and evaluation of 2,5-bis[4-(N-ethoxycarbonyl-N'-isopropyl)amidinophenyl]furan, 2,5-bis[4-(N-2,2,2-trichloroethoxycarbonyl-N'-isopropyl)amidinophenyl]furan and 2,5-bis[4-(N-cyclopentyl-N'-2,2,2-trichloroethoxycarbonyl)amidinophenyl]furan as prodrugs of bis-N-alkylamidines are reported. The results show that the bis-2,2,2-trichloroethyl carbamates function effectively in a rat model for Pneumocystis pneumonia.

Topics: Animals; Benzamidines; Carbamates; Cysts; Disease Models, Animal; Furans; Lung; Pneumocystis carinii; Pneumonia, Pneumocystis; Prodrugs; Rats

The key dinitrile intermediates 4a-d were synthesized by reaction of phenacyl bromide 1 and the appropriate 2-amino-5-bromopyridines to yield 3a-d. Suzuki coupling of 3a-d with 4-cyanophenylboronic acid yielded the 2,6-bis(4-cyanophenyl)-imidazo[1,2-a]pyridine derivatives 4a-d. The bis-amidoximes 5a-d, obtained from 4a-d by the action of hydroxylamine, were converted to the bis-O-acetoxyamidoximes which on catalytic hydrogenation in a mixture of ethanol/ethyl acetate gave the acetate salts of 2,6-bis[4-(amidinophenyl)]-imidazo[1,2-a]pyridines 7a-d. In contrast, catalytic hydrogenation of the bis-O-acetoxyamidoxime of 5a in glacial acetic acid gave the saturated analogue 2,6-bis[4-(amidinophenyl)]-5,6,7,8-tetrahydro-imidazo[1,2-a]pyridine 8. O-Methylation of the amidoximes 5a-d gave the N-methoxyamidines 6a-d. The diamidines showed strong DNA binding affinity, were very active in vitro against T. b. r. exhibiting IC(50) values between 7 and 38nM, but were less effective against P. f. with IC(50) values between 23 and 92nM. Two of the diamidines 7c and 7d were slightly more active than furamidine but less active than azafuramidine in the T. b. r. STIB900 mouse model. Only one prodrug 6b showed moderate activity in the same mouse model.

Topics: Animals; Antimalarials; Antiprotozoal Agents; Combinatorial Chemistry Techniques; Disease Models, Animal; Inhibitory Concentration 50; Mice; Molecular Structure; Plasmodium falciparum; Prodrugs; Pyridines; Trypanosoma brucei rhodesiense

Five O-alkoxyamidine analogues of the prodrug 2,5-bis[4-methoxyamidinophenyl]furan were synthesized and evaluated against Trypanosoma brucei rhodesiense in the STIB900 mouse model by oral administration. The observed in vivo activity of these prodrugs demonstrates that compounds with an O-methoxyamidine or O-ethoxyamidine group effectively cured all trypanosome-infected mice, whereas prodrugs with larger side-chains did not completely cure the mice. Permeability across Caco-2 cell monolayers and microsomal metabolism were used to identify the underlying mechanisms of prodrug efficacy.

Topics: Administration, Oral; Animals; Benzamidines; Biological Transport; Caco-2 Cells; Disease Models, Animal; Humans; In Vitro Techniques; Mice; Microsomes, Liver; Permeability; Prodrugs; Structure-Activity Relationship; Trypanocidal Agents; Trypanosoma brucei rhodesiense; Trypanosomiasis, African