nifurtimox and Trypanosomiasis

In our search for new protein farnesyltransferase inhibitors with improved antiparasitic activities, we modified our previously developed 3-arylthiophene series of inhibitors by replacing the thioisopropyl group by different substituted imidazolylmethanamino moieties. Twenty four new derivatives were synthesized and evaluated against human and parasite farnesyltransferases, and their anti-parasitic activity was determined against Plasmodium falciparum, Trypanosoma brucei, Trypanosoma cruzi, and Leishmania donovani. Introduction of a N-p-substituted-benzylimidazole led to significantly increase the inhibition of parasite proliferation in the submicromolar range. The structure of the best inhibitors was parasite dependent. Three compounds possess IC50 values at the same range as the reference miltefosine against L. donovani proliferation and other new derivatives display high level of anti-trypanosomal activity against T. cruzi, higher or in the same order of magnitude as the reference compounds benznidazole and nifurtimox.

Topics: Alkyl and Aryl Transferases; Animals; Antiparasitic Agents; Cell Line; Enzyme Inhibitors; Humans; Imidazoles; Leishmania donovani; Leishmaniasis, Visceral; Malaria, Falciparum; Mice; Parasitic Sensitivity Tests; Plasmodium falciparum; Trypanosoma; Trypanosoma brucei brucei; Trypanosoma cruzi; Trypanosomiasis

Trypanosomes from animals are potential pathogens for humans. Several human cases infected by Trypanosoma lewisi, a parasite of rats, have been reported. The number of these infections is possibly underestimated. Some infections were self-cured, others required treatment with drugs used in human African trypanosomosis. An in vitro evaluation of these drugs and fexinidazole, a new oral drug candidate, has been performed against T. lewisi in comparison with T. brucei gambiense. All have comparable activities against the two parasites. Suramin was not effective. In vivo, drugs were tested in rats immunosuppressed by cyclophosphamide. The best efficacy was obtained for fexinidazole, and pentamidine (15 mg/kg): rats were cured in 7 and 10 days respectively. Rats receiving nifurtimox-eflornithine combination therapy (NECT) or pentamidine (4 mg/kg) were cured after 28 days, while melarsoprol was weakly active. The identification of efficient drugs with reduced toxicity will help in the management of new cases of atypical trypanosomosis.

Topics: Animals; Eflornithine; Female; Humans; Immunocompromised Host; Inhibitory Concentration 50; Melarsoprol; Mice; Nifurtimox; Nitroimidazoles; Parasitemia; Pentamidine; Rats; Rats, Wistar; Suramin; Trypanocidal Agents; Trypanosoma lewisi; Trypanosomiasis

The trypanocidal agents nifurtimox and benznidazole both function as prodrugs and must undergo enzyme-mediated activation, a reaction catalyzed by type I nitroreductase (NTR). In the search for new parasitic therapies, we have utilized this finding to investigate whether aziridinyl nitrobenzamide derivatives have activity against bloodstream-form Trypanosoma brucei and Trypanosoma cruzi amastigotes, parasite stages that replicate in the mammalian host. For T. cruzi drug screening, we generated trypanosomes that expressed the luciferase reporter gene and optimized a mammalian infection model in a 96-well plate format. A subset of compounds having a 5-(aziridin-1-yl)-2,4-dinitrobenzyl structure was shown to be metabolized by purified T. brucei NTR and when screened against both parasite life cycle stages displayed significant growth-inhibitory properties: the most potent compounds generated 50% inhibitory concentrations of <1 μM. The trypanocidal activity was shown to be NTR specific, since parasites overexpressing this enzyme were hypersensitive to the aziridinyl dinitrobenzyl agents. We conclude that members of the aziridinyl nitrobenzamide class of nitroheterocycles provide new lead structures that have the potential to treat trypanosomal infections.

Topics: Animals; Benzamides; Chlorocebus aethiops; Inhibitory Concentration 50; Trypanocidal Agents; Trypanosoma brucei brucei; Trypanosoma cruzi; Trypanosomiasis; Vero Cells

The trypanocidal activity of N-isopropyl oxamate (NIPOx) and the ethyl ester of N-isopropyl oxamate (Et-NIPOx) were tested on cultured epimastigotes (in vitro) and on murine trypanosomiasis (in vivo) using five different T. cruzi strains. When benznidazole and nifurtimox, used for comparison, were tested we found that only three of these T. cruzi strains were affected, whereas the other two strains, Miguz and Compostela, were resistant to the in vitro and the in vivo trypanocidal activity of these substances. In addition, when NIPOx was tested on cultured epimastigotes and on mice parasitaemia, trypanocidal activity was not obtained on either of these T. cruzi strains. Our experiments strongly suggest that NIPOx does not penetrate intact epimastigotes due to the polarity of its carboxylate whereas Et-NIPOx, acting as a prodrug, exhibited in vitro and in vivo trypanocidal activity in the five tested T. cruzi strains.

Topics: Alcohol Oxidoreductases; Animals; Disease Models, Animal; Dose-Response Relationship, Drug; Enzyme Inhibitors; Kinetics; Mice; Models, Chemical; NAD; Nifurtimox; Nitroimidazoles; Oxamic Acid; Species Specificity; Time Factors; Trypanocidal Agents; Trypanosoma cruzi; Trypanosomiasis

In rats infected with Trypanosoma lewisi, parasitaemia normally resolves by day 32; thereafter, the rodents become solidly immune to re-infection. Rats treated on day 5 of infection with a single i.m. dose of 35 mg/kg of the trypanocidal drug ethidium bromide (EB) had recovered from parasitaemia by day 12, whereas berenil (BE) given at 100 mg/kg, more than twice the recommended dose, had no effect on parasitaemia. However, rats treated for 4 consecutive days beginning on day 5 of infection with Lampit (LA) and Radanil (RA) at 350 mg/kg showed no parasitaemia on days 16 and 20, respectively. EB was the most effective drug in lowering the total IgG antibody as compared with the control animals, whose specific IgG titres remained elevated for over 200 days after the parasitaemia had been cleared. LA also significantly reduced the antibody levels through day 240, whereas RA only transitorily depressed the antibody levels on days 20 and 30. BE, which had no effect on parasitaemia, correspondingly failed to depress the total IgG levels. Re-challenge infection of the drug-treated, recovered animals on day 240 (208 days after the normal resolution of the infection) revealed that except for the EB group, which displayed transitory parasitaemia for 4 days, other treated and control rats completely resisted the challenge; pre-challenge antibody titres were lower than 1:160 in EB-treated animals in contrast to the levels of 1:320 or higher measured in the other drug-treated and control animals, which resisted the infection.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Antibodies, Protozoan; Diminazene; Ethidium; Female; Immunoglobulin G; Nifurtimox; Nitroimidazoles; Rats; Rats, Inbred F344; Trypanocidal Agents; Trypanosoma lewisi; Trypanosomiasis

A comparative study showed that 5 laboratory strains of Trypanosoma cruzi could be divided into a non-responsive group (Sonya clone and Colombiana) and a responsive group (Tulahuén, Y and Peru), based on long-term treatment of mouse infections with nifurtimox and benznidazole. In vitro sensitivity of epimastigotes and blood-stream trypomastigotes in macrophage cultures did not distinguish the strains, nor did the rate of development of nifurtimox resistance by epimastigote cultures. 7 novel anti-T. cruzi compounds also behaved similarly with respect to the 2 groups. A small decrease in sensitivity was observed in vitro by non-responsive strains of T. cruzi after re-isolation from treated mice. It is postulated that there could be an immunological component involved in successful treatment of T. cruzi infection.

Topics: Animals; Dose-Response Relationship, Drug; Drug Resistance; Macrophages; Male; Mice; Nifurtimox; Nitroimidazoles; Trypanocidal Agents; Trypanosoma cruzi; Trypanosomiasis

Adrenals, hearts, kidneys, livers, lungs, and spleens were removed from C3H/Anf mice which had been inoculated with Trypanosoma (Herpetosoma) musculi and no longer exhibited parasitemias. Imprints of each organ were examined microscopically, and each was homogenized and injected into recipient mice. It was confirmed that trypanosomes could be detected only in the donor kidneys. Lampit or Ethidium treatment eliminated bloodstream and kidney forms when administration was initiated after the development of patent parasitemias. However, mice treated with Lampit on the same day they were inoculated with T. musculi developed parasitemias later than animals injected with drug after parasites had appeared in their blood. Both Lampit and Ethidium depressed antibody production as detected in enzyme-linked immunosorbent assays of antisera from animals having parasitemias at the time of treatment. The elimination of kidney forms by Lampit or Ethidium treatment did not reduce the resistance of mice to reinfection by T. musculi 12 weeks or 15 and 22 weeks, respectively, after the initial inoculation of these animals with the parasites. Kidney forms were not required for the sustained protective immunity of the mice against reinfection during the intervals of these experiments.

Topics: Animals; Antibody Formation; Blood; Ethidium; Female; Immunity; Kidney; Mice; Mice, Inbred Strains; Nifurtimox; Nitrofurans; Species Specificity; Time Factors; Trypanosoma; Trypanosomiasis

The ability of a range of trypanocidal drugs, including a number known to be active in Trypanosoma cruzi infections were tested against Trypanosoma musculi infections in the mouse. The ability of these drugs, particularly in their ability to eliminate the "cryptic phase" of T. musculi infections remaining in the kidneys, was investigated and their activity against this phase of T. musculi largely paralleled their known activity against T. cruzi infections. It is suggested that this could be used as a preliminary screening test for potential T. cruzi-active drugs.

Topics: Animals; Chagas Disease; Diminazene; Drug Evaluation, Preclinical; Ethidium; Female; Kidney; Mice; Nifurtimox; Nitroimidazoles; Phenanthridines; Trypanocidal Agents; Trypanosomiasis