nifurtimox and fexinidazole

Chagas disease and African sleeping sickness are trypanosomal infections that represent important public health problems in Latin America and Africa, respectively. The restriction of these diseases to the poorer parts of the world has meant that they have been largely neglected and limited progress has been made in their treatment. The nitroheterocyclic prodrugs nifurtimox and benznidazole, in use against Chagas disease for >40 years, remain the only agents available for this infection. In the case of African sleeping sickness, nifurtimox has recently been added to the arsenal of medicines, with the nitroheterocycle fexinidazole currently under evaluation. For a long time, the cytotoxic mechanism of these drugs was poorly understood: nifurtimox was thought to act via production of superoxide anions and nitro radicals, while the mode of benznidazole action was more obscure. The trypanocidal activity of nitroheterocyclic drugs is now known to depend on a parasite type I nitroreductase (NTR). This enzyme is absent from mammalian cells, a difference that forms the basis for the drug selectivity. The role of this enzyme in drug activation has been genetically and biochemically validated. It catalyses the 2-electron reduction of nitroheterocyclic compounds within the parasite, producing toxic metabolites without significant generation of superoxide. Recognition that this enzyme is responsible for activation of nitroheterocyclic prodrugs has allowed screening for compounds that preferentially target the parasite. This approach has led to the identification of two new classes of anti-trypanosomal agents, nitrobenzylphosphoramide mustards and aziridinyl nitrobenzamides, and promises to yield new, safer, more effective drugs.

Topics: Africa; Animals; Benzamides; Chagas Disease; Humans; Insect Vectors; Latin America; Nifurtimox; Nitro Compounds; Nitroimidazoles; Nitroreductases; Phosphoramide Mustards; Prodrugs; Protozoan Proteins; Trypanocidal Agents; Trypanosoma brucei brucei; Trypanosoma cruzi; Trypanosomiasis, African

This review covers recent developments towards novel treatments for human African trypanosomiasis (HAT).. Within the past decade, some important advances in the treatment of HAT have been made. One old drug, melarsoprol, previously administered over a period of a month or more, is now given in a 10-day regimen greatly reducing hospital costs. A combination chemotherapy, eflornithine alongside nifurtimox, has been introduced to decrease the time frame and overall dosing of eflornithine and reducing the risk of drug resistance emerging. One new, orally available diamidine prodrug, pafuramidine, that recently completed phase III clinical trials, disappointingly was halted in its progress to clinic when unforeseen toxicity issues emerged. The diamidine series, however, has recently yielded representatives that cure second-stage central nervous system (CNS)-involved infections in experimental animals while showing less tissue accumulation in mammals and thus offer considerable promise. A nitroheterocycle, fexinidazole, whose trypanocidal activity was first shown nearly 30 years ago, has entered clinical trials. Another approach, grounded in the use of pharmacokinetic data, has brought another new class of compound based on the oxaborole scaffold forward for clinical candidacy. Furthermore, several target-based and whole organism-based chemical compound screening campaigns have identified promising hits for lead development.. The new developments in trypanocidal drug discovery mean that new compounds could become available within the next 5 years to support the WHO declared campaign to eliminate HAT.

Topics: Animals; Benzamides; Boron Compounds; Drug Discovery; Drug Resistance; Drug Therapy, Combination; Eflornithine; Humans; Melarsoprol; Mice; Nifurtimox; Nitroimidazoles; Pentamidine; Trypanocidal Agents; Trypanosoma brucei brucei; Trypanosomiasis, African

Few therapeutic options are available to treat the late-stage of human African trypanosomiasis, a neglected tropical disease, caused by Trypanosoma brucei gambiense (g-HAT). The firstline treatment is a combination therapy of oral nifurtimox and intravenous eflornithine that needs to be administered in a hospital setting by trained personnel, which is not optimal given that patients often live in remote areas with few health resources. Therefore, we aimed to assess the safety and efficacy of an oral regimen of fexinidazole (a 2-substituted 5-nitroimidazole with proven trypanocidal activity) versus nifurtimox eflornithine combination therapy in patients with late-stage g-HAT.. In this randomised, phase 2/3, open-label, non-inferiority trial, we recruited patients aged 15 years and older with late-stage g-HAT from g-HAT treatment centres in the Democratic Republic of the Congo (n=9) and the Central African Republic (n=1). Patients were randomly assigned (2:1) to receive either fexinidazole or nifurtimox eflornithine combination therapy according to a predefined randomisation list (block size six). The funder, data management personnel, and study statisticians were masked to treatment. Oral fexinidazole was given once a day (days 1-4: 1800 mg, days 5-10: 1200 mg). Oral nifurtimox was given three times a day (days 1-10: 15 mg/kg per day) with eflornithine twice a day as 2 h infusions (days 1-7: 400 mg/kg per day). The primary endpoint was success at 18 months (ie, deemed as patients being alive, having no evidence of trypanosomes in any body fluid, not requiring rescue medication, and having a cerebrospinal fluid white blood cell count ≤20 cells per μL). Safety was assessed through routine monitoring. Primary efficacy analysis was done in the modified intention-to-treat population and safety analyses in the intention-to-treat population. The acceptable margin for the difference in success rates was defined as 13%. This study has been completed and is registered with ClinicalTrials.gov, number NCT01685827.. Between October, 2012, and November, 2016, 419 patients were pre-screened. Of the 409 eligible patients, 14 were not included because they did not meet all inclusion criteria (n=12) or for another reason (n=2). Therefore, 394 patients were randomly assigned, 264 to receive fexinidazole and 130 to receive nifurtimox eflornithine combination therapy. Success at 18 months was recorded in 239 (91%) patients given fexinidazole and 124 (98%) patients given nifurtimox eflornithine combination therapy, within the margin of acceptable difference of -6·4% (97·06% CI -11·2 to -1·6; p=0·0029). We noted no difference in the proportion of patients who experienced treatment-related adverse events (215 [81%] in the fexinidazole group vs 102 [79%] in the nifurtimox eflornithine combination therapy group). Treatment discontinuations were unrelated to treatment (n=2 [1%] in the fexinidazole group). Temporary nifurtimox eflornithine combination therapy interruption occurred in three (2%) patients. 11 patients died during the study (nine [3%] in the fexinidazole group vs two [2%] in the nifurtimox eflornithine combination therapy group).. Our findings show that oral fexinidazole is effective and safe for the treatment of T b gambiense infection compared with nifurtimox eflornithine combination therapy in late-stage HAT patients. Fexinidazole could be a key asset in the elimination of this fatal neglected disease.. Drugs for Neglected Diseases initiative.

Topics: Administration, Oral; Adult; Democratic Republic of the Congo; Drug Administration Schedule; Drug Therapy, Combination; Female; Humans; Male; Middle Aged; Nifurtimox; Nitroimidazoles; Treatment Outcome; Trypanocidal Agents; Trypanosoma brucei gambiense; Trypanosomiasis, African

Drug combinations have been evaluated for Chagas disease in an attempt to improve efficacy and safety. In this line, the objective of this work is to assess the effects of treatment with nitro drugs combinations using benznidazole (BZ) or nifurtimox (NFX) plus the sulfone metabolite of fexinidazole (fex-SFN) in vitro and in vivo on Trypanosoma cruzi infection. The in vitro interaction of fex-SFN and BZ or NFX against infected H9c2 cells by the Y strain was classified as an additive (0.5⩾ΣFIC<4), suggesting the possibility of a dose reduction in the in vivo T. cruzi infection. Next, the effect of combining suboptimal doses was assessed in an acute model of murine T. cruzi infection. Drug combinations led to a faster suppression of parasitemia than monotherapies. Also, the associations led to higher cure levels than those in the reference treatment BZ 100 mg day−1 (57.1%) (i.e. 83.3% with BZ/fex-SFN and 75% with NFX/fex-SFN). Importantly, toxic effects resulting from the associations were not observed, according to weight gain and hepatic enzyme levels in the serum of experimental animals. Taken together, this study is a starting point to explore the potential effects of nitro drugs combinations in preclinical models of kinetoplastid-related infections.

Topics: Animals; Chagas Disease; Drug Therapy, Combination; Female; Humans; Inhibitory Concentration 50; Mice; Neglected Diseases; Nifurtimox; Nitro Compounds; Nitroimidazoles; Real-Time Polymerase Chain Reaction; Sulfones

Human African trypanosomiasis caused by Trypanosoma brucei gambiense is a parasitic infection that usually progresses to coma and death unless treated. WHO has updated its guidelines for the treatment of this infection on the basis of independent literature reviews and using the Grading of Recommendations Assessment, Development and Evaluation methodology. The first-line treatment options, pentamidine and nifurtimox-eflornithine combination therapy, have been expanded to include fexinidazole, an oral monotherapy given a positive opinion from the European Medicines Agency. Fexinidazole is recommended for individuals who are aged 6 years and older with a bodyweight of 20 kg or more, who have first-stage or second-stage gambiense human African trypanosomiasis and a cerebrospinal fluid leucocyte count less than 100 per μL. Nifurtimox-eflornithine combination therapy remains recommended for patients with 100 leucocytes per μL or more. Without clinical suspicion of severe second-stage disease, lumbar puncture can be avoided and fexinidazole can be given. Fexinidazole should only be administered under supervision of trained health staff. Because these recommendations are expected to change clinical practice considerably, health professionals should consult the detailed WHO guidelines. These guidelines will be updated as evidence accrues.

Topics: Adolescent; Adult; Aged; Aged, 80 and over; Antiprotozoal Agents; Child; Child, Preschool; Eflornithine; Female; Humans; Infant; Infant, Newborn; Male; Middle Aged; Nifurtimox; Nitroimidazoles; Practice Guidelines as Topic; Trypanosoma brucei gambiense; Trypanosomiasis, African; World Health Organization; Young Adult

The objective of this study was to identify the mechanisms of resistance to nifurtimox and fexinidazole in African trypanosomes.. Bloodstream-form Trypanosoma brucei were selected for resistance to nifurtimox and fexinidazole by stepwise exposure to increasing drug concentrations. Clones were subjected to WGS to identify putative resistance genes. Transgenic parasites modulating expression of genes of interest were generated and drug susceptibility phenotypes determined.. Nifurtimox-resistant (NfxR) and fexinidazole-resistant (FxR) parasites shared reciprocal cross-resistance suggestive of a common mechanism of action. Previously, a type I nitroreductase (NTR) has been implicated in nitro drug activation. WGS of resistant clones revealed that NfxR parasites had lost >100 kb from one copy of chromosome 7, rendering them hemizygous for NTR as well as over 30 other genes. FxR parasites retained both copies of NTR, but lost >70 kb downstream of one NTR allele, decreasing NTR transcription by half. A single knockout line of NTR displayed 1.6- and 1.9-fold resistance to nifurtimox and fexinidazole, respectively. Since NfxR and FxR parasites are ∼6- and 20-fold resistant to nifurtimox and fexinidazole, respectively, additional factors must be involved. Overexpression and knockout studies ruled out a role for a putative oxidoreductase (Tb927.7.7410) and a hypothetical gene (Tb927.1.1050), previously identified in a genome-scale RNAi screen.. NTR was confirmed as a key resistance determinant, either by loss of one gene copy or loss of gene expression. Further work is required to identify which of the many dozens of SNPs identified in the drug-resistant cell lines contribute to the overall resistance phenotype.

Topics: Antiprotozoal Agents; Drug Resistance; Genome, Protozoan; Nifurtimox; Nitroimidazoles; Nitroreductases; Parasitic Sensitivity Tests; Polymorphism, Single Nucleotide; Sequence Analysis, DNA; Trypanosoma brucei brucei

The insect-transmitted protozoan parasite Trypanosoma cruzi is the causative agent of Chagas disease, and infects 5-8 million people in Latin America. Chagas disease is characterised by an acute phase, which is partially resolved by the immune system, but then develops as a chronic life-long infection. There is a consensus that the front-line drugs benznidazole and nifurtimox are more effective against the acute stage in both clinical and experimental settings. However, confirmative studies have been restricted by difficulties in demonstrating sterile parasitological cure. Here, we describe a systematic study of nitroheterocyclic drug efficacy using highly sensitive bioluminescence imaging of murine infections. Unexpectedly, we find both drugs are more effective at curing chronic infections, judged by treatment duration and therapeutic dose. This was not associated with factors that differentially influence plasma drug concentrations in the two disease stages. We also observed that fexinidazole and fexinidazole sulfone are more effective than benznidazole and nifurtimox as curative treatments, particularly for acute stage infections, most likely as a result of the higher and more prolonged exposure of the sulfone derivative. If these findings are translatable to human patients, they will have important implications for treatment strategies.

Topics: Animals; Area Under Curve; Chagas Disease; Disease Models, Animal; Female; Male; Mice; Mice, Inbred BALB C; Mice, Inbred C3H; Nifurtimox; Nitroimidazoles; Treatment Outcome; Trypanocidal Agents; Trypanosoma cruzi

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

Screening of candidate trypanocidal compounds or factors affecting invasion of mammalian cells by the infective stages of Trypanosoma cruzi in tissue culture models has primarily involved labor-intensive microscopic counting of the parasites. A very efficient method for quantitating the inhibitory effect of antimicrobial agents or signaling pathways inhibitors on T. cruzi grown in L6E9 myoblasts was devised. This assay takes advantage of the selective incorporation of [3H]uracil into nucleic acids by replicating T. cruzi amastigotes. L6E9 rat myoblasts are submitted to gamma irradiation to inhibit their replication. Uracil uptake by uninfected cells is considerably decreased by this method. Nifurtimox, benznidazole, fexinidazole, MK-436, and megazol are drugs known to have activity against T. cruzi and were used in growth inhibition assays. The results demonstrated that [3H]uracil incorporation in the presence of different concentrations of nifurtimox and benznidazole closely correlated with the number of amastigotes per 100 myoblasts in Giemsa-stained monolayers under the conditions used. This method also has the advantage to differentiate between the effects of the compounds on the invasion and the replication steps of the infection with T. cruzi, as shown by the inhibitory effect of genistein when added in invasion assays.

Topics: Animals; Cells, Cultured; DNA Replication; DNA, Protozoan; Drug Evaluation, Preclinical; Drug Resistance; Gamma Rays; Muscle, Skeletal; Nifurtimox; Nitroimidazoles; Rats; Reproduction; Thiadiazoles; Trypanocidal Agents; Trypanosoma cruzi; Uracil

In trypanosomiasis chemotherapy the main mode of action of the nitro-compounds, including the 5-nitroimidazoles or nitrofurans (nifurtimox) is to increase the oxidative stress on the organism either directly by the production of peroxides or indirectly by "futile redox cycling". If this is the case, then these nitro-compounds and the arsenicals should act in combination on the trypanothione oxidation-reduction reaction of the trypanosome. In this paper this has been demonstrated to occur with all those nitro-compounds which have exhibited reasonable trypanocidal action in monotherapy or other combination chemotherapeutic regimens. A major advantage is the short treatment period of approximately 5 days. Pretreatment with a single dose of suramin increased the efficacy of the nitroimidazole-arsenical combination.

Topics: Animals; Antiprotozoal Agents; Arsenicals; Brain Diseases; Drug Synergism; Drug Therapy, Combination; Female; Ketoconazole; Metronidazole; Mice; Nifurtimox; Nitro Compounds; Nitroimidazoles; Oxidation-Reduction; Suramin; Trypanocidal Agents; Trypanosoma brucei brucei; Trypanosomiasis, African