Combined treatment with benznidazole and allopurinol in mice infected with a virulent Trypanosoma cruzi isolate from Nicaragua

Drugs in preclinical and early clinical development for the treatment of Chagas´s disease: the current status

INTRODUCTION

Chagas disease is spreading faster than expected in different countries, and little progress has been reported in the discovery of new drugs to combat Trypanosoma cruzi infection in humans. Recent clinical trials have ended with small hope. The pathophysiology of this neglected disease and the genetic diversity of parasites are exceptionally complex. The only two drugs available to treat patients are far from being safe, and their efficacy in the chronic phase is still unsatisfactory.

AREAS COVERED

This review offers a comprehensive examination and critical review of data reported in the last 10 years, and it is focused on findings of clinical trials and data acquired in vivo in preclinical studies.

EXPERT OPINION

The in vivo investigations classically in mice and dog models are also challenging and time-consuming to attest cure for infection. Poorly standardized protocols, availability of diagnosis methods and disease progression markers, the use of different T. cruzi strains with variable benznidazole sensitivities, and animals in different acute and chronic phases of infection contribute to it. More synchronized efforts between research groups in this field are required to put in evidence new promising substances, drug combinations, repurposing strategies, and new pharmaceutical formulations to impact the therapy.

Combination therapy using nitro compounds improves the efficacy of experimental Chagas disease treatment

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.

In vitro studies and preclinical evaluation of benznidazole microparticles in the acute Trypanosoma cruzi murine model

Chagas disease is a serious parasitic infection caused by Trypanosoma cruzi. Unfortunately, the current chemotherapeutic tools are not enough to combat the infection. The aim of this study was to evaluate the trypanocidal activity of benznidazole-loaded microparticles during the acute phase of Chagas infection in an experimental murine model. Microparticles were prepared by spray-drying using copolymers derived from esters of acrylic and methacrylic acids as carriers. Dissolution efficiency of the formulations was up to 3.80-fold greater than that of raw benznidazole. Stability assay showed no significant difference (P > 0.05) in the loading capacity of microparticles for 3 years. Cell cultures showed no visible morphological changes or destabilization of the cell membrane nor haemolysis was observed in defibrinated human blood after microparticles treatment. Mice with acute lethal infection survived 100% after 30 days of treatment with benznidazole microparticles (50 mg kg-1 day-1). Furthermore, no detectable parasite load measured by quantitative polymerase chain reaction and lower levels of T. cruzi-specific antibodies by enzyme-linked immunosorbent assay were found in those mice. A significant decrease in the inflammation of heart tissue after treatment with these microparticles was observed, in comparison with the inflammatory damage observed in both infected mice treated with raw benznidazole and untreated infected mice. Therefore, these polymeric formulations are an attractive approach to treat Chagas disease.

Review on Experimental Treatment Strategies Against Trypanosoma cruzi

Chagas disease is a neglected tropical disease caused by the protozoan Trypanosoma cruzi. Currently, only nitroheterocyclic nifurtimox (NFX) and benznidazole (BNZ) are available for the treatment of Chagas disease, with limitations such as variable efficacy, long treatment regimens and toxicity. Different strategies have been used to discover new active molecules for the treatment of Chagas disease. Target-based and phenotypic screening led to thousands of compounds with anti-T. cruzi activity, notably the nitroheterocyclic compounds, fexinidazole and its metabolites. In addition, drug repurposing, drug combinations, re-dosing regimens and the development of new formulations have been evaluated. The CYP51 antifungal azoles, as posaconazole, ravuconazole and its prodrug fosravuconazole presented promising results in experimental Chagas disease. Drug combinations of nitroheterocyclic and azoles were able to induce cure in murine infection. New treatment schemes using BNZ showed efficacy in the experimental chronic stage, including against dormant forms of T. cruzi. And finally, sesquiterpene lactone formulated in nanocarriers displayed outstanding efficacy against different strains of T. cruzi, susceptible or resistant to BNZ, the reference drug. These pre-clinical results are encouraging and provide interesting evidence to improve the treatment of patients with Chagas disease.

Revisiting Pyrazolo[3,4-d]pyrimidine Nucleosides as Anti-Trypanosoma cruzi and Antileishmanial Agents

Chagas disease and visceral leishmaniasis are two neglected tropical diseases responsible for numerous deaths around the world. For both, current treatments are largely inadequate, resulting in a continued need for new drug discovery. As both kinetoplastid parasites are incapable of de novo purine synthesis, they depend on purine salvage pathways that allow them to acquire and process purines from the host to meet their demands. Purine nucleoside analogues therefore constitute a logical source of potential antiparasitic agents. Earlier optimization efforts of the natural product tubercidin (7-deazaadenosine) involving modifications to the nucleobase 7-position and the ribofuranose 3'-position led to analogues with potent anti-Trypanosoma brucei and anti-Trypanosoma cruzi activities. In this work, we report the design and synthesis of pyrazolo[3,4-d]pyrimidine nucleosides with 3'- and 7-modifications and assess their potential as anti-Trypanosoma cruzi and antileishmanial agents. One compound was selected for in vivo evaluation in an acute Chagas disease mouse model.

Efficacy of continuous versus intermittent administration of nanoformulated benznidazole during the chronic phase of Trypanosoma cruzi Nicaragua infection in mice

Background

Benznidazole and nifurtimox are effective drugs used to treat Chagas’ disease; however, their administration in patients in the chronic phase of the disease is still limited, mainly due to their limited efficacy in the later chronic stage of the disease and to the adverse effects related to these drugs.

Objectives

To evaluate the effect of low doses of nanoformulated benznidazole using a chronic model of Trypanosoma cruzi Nicaragua infection in C57BL/6J mice.

Methods

Nanoformulations were administered in two different schemes: one daily dose for 30 days or one dose every 7 days, 13 times.

Results

Both treatment schemes showed promising outcomes, such as the elimination of parasitaemia, a reduction in the levels of T. cruzi-specific antibodies and a reduction in T. cruzi-specific IFN-γ-producing cells, as well as an improvement in electrocardiographic alterations and a reduction in inflammation and fibrosis in the heart compared with untreated T. cruzi-infected animals. These results were also compared with those from our previous work on benznidazole administration, which was shown to be effective in the same chronic model.

Conclusions

In this experimental model, intermittently administered benznidazole nanoformulations were as effective as those administered continuously; however, the total dose administered in the intermittent scheme was lower, indicating a promising therapeutic approach to Chagas’ disease.

Synergic Effect of Allopurinol in Combination with Nitroheterocyclic Compounds against Trypanosoma cruzi

Combination therapy has gained attention as a possible strategy for overcoming the limitations of the present therapeutic arsenal for Chagas disease. The aim of this study was to evaluate the effect of allopurinol in association with nitroheterocyclic compounds on infection with the Y strain of Trypanosoma cruzi The in vitro effect of allopurinol plus benznidazole or nifurtimox on intracellular amastigotes in infected H9c2 cells was assessed in a 72-h assay. The interactions were classified as synergic for both allopurinol-nifurtimox (sums of fractional inhibitory concentrations [∑FICs] = 0.49 ± 0.08) and allopurinol-benznidazole (∑FICs = 0.48 ± 0.09). In the next step, infected Swiss mice were treated with allopurinol at 30, 60, and 90 mg/kg of body weight and with benznidazole at 25, 50, and 75 mg/kg in monotherapy and in combination at the same doses; as a reference treatment, another group of animals received benznidazole at 100 mg/kg. Allopurinol in monotherapy led to a smaller or nil effect in the reduction of parasite load and mortality rate. Treatment with benznidazole at suboptimal doses induced a transient suppression of parasitaemia with subsequent relapse in all animals treated with 25 and 50 mg/kg and in 80% of those that received 75 mg/kg. Administration of the drugs in combination significantly increased the cure rate to 60 to 100% among mice treated with benznidazole at 75 mg/kg plus 30, 60, or 90 mg/kg of allopurinol. These results show a positive interaction between allopurinol and benznidazole, and since both drugs are commercially available, their use in combination may be considered for the assessment in the treatment of Chagas disease patients.

Experimental combination therapy using low doses of benznidazole and allopurinol in mouse models of Trypanosoma cruzi chronic infection

This study evaluated the effectiveness of low doses of benznidazole (BNZ) on continuous administration (BNZc), combined with allopurinol (ALO), in C57BL/6J and C3H/HeN mice infected with Trypanosoma cruzi Nicaragua strain and T. cruzi Sylvio-X10/4 clone. TcN-C57BL/6J was also treated with intermittent doses of BNZ (BNZit). The drug therapy started 3 months post infection (pi) in the chronic phase of mice with heart disease progression, followed-up at 6 months pi. TcN-C57BL/6J treated with BNZc was also monitored up to 12 months pi by serology and electrocardiogram. These mice showed severe electrical abnormalities, which were not observed after BNZc or BNZit. ALO only showed positive interaction with the lowest dose of BNZ. A clear parasitic effect, with significant reductions in antibody titres and parasitic loads, was achieved in all models with low doses of BNZ, and a 25% reduction of the conventional dose showed more efficacy to inhibit the development of the pathology. However, BNZ 75 showed partial efficacy in the TcSylvio-X10/4-C3H/HeN model. In our experimental designs, C57BL/6J allowed to clearly define a chronic phase, and through reproducible efficacy indicators, it can be considered a good preclinical model.

Molecular and biological characterization of a highly pathogenic Trypanosoma cruzi strain isolated from a patient with congenital infection

Although many Trypanosoma cruzi (T. cruzi) strains isolated from a wide range of hosts have been characterized, there is a lack of information about biological features from vertically transmitted strains. We describe the molecular and biological characteristics of the T. cruzi VD strain isolated from a congenital Chagas disease patient. The VD strain was typified as DTU TcVI; in vitro sensitivity to nifurtimox (NFX) and beznidazole (BZ) were 2.88 μM and 6.19 μM respectively, while inhibitory concentrations for intracellular amastigotes were 0.24 μM for BZ, and 0.66 μM for NFX. Biological behavior of VD strain was studied in a mouse model of acute infection, resulting in high levels of parasitemia and mortality with a rapid clearence of bloodstream trypomastigotes when treated with BZ or NFX, preventing mortality and reducing parasitic load and intensity of inflammatory infiltrate in skeletal and cardiac muscle. Treatment-induced parasitological cure, evaluated after immunossupression were 41% and 35% for BZ and NFX treatment respectively, suggesting a partial response to these drugs in elimination of parasite burden. This exhaustive characterization of this T. cruzi strain provides the basis for inclusion of this strain in a panel of reference strains for drug screening and adds a new valuable tool for the study of experimental T. cruzi infection.

Elucidating the impact of low doses of nano-formulated benznidazole in acute experimental Chagas disease

Background

Chagas disease is a neglected parasitic infection caused by the protozoan Trypanosoma cruzi (T. cruzi) that affects more than 6 million people, mainly in Latin America. Benznidazole is still the drug of choice in many countries to treat it in spite of its dosage regimen and adverse side effects such as such as allergic dermatitis, peripheral neuropathy and anorexia. Thus, novel, safer, and more efficacious treatments for such neglected infection are urgently required.

Methodology

In this study, the efficacy of orally administered low doses of benznidazole (BNZ) nanoparticles was evaluated during the acute phase in mice infected with T. cruzi Nicaragua (TcN) that were immunosuppressed during the chronic stage of the disease. Moreover, the production of T. cruzi-specific antibodies, cardiac tissue inflammation and reactive oxygen species generation by Vero cells treated with both BNZ nanoparticles (BNZ-nps) and raw BNZ (R-BNZ) were also evaluated.

Principal findings

T. cruzi infected mice treated with 10, 25 or 50 mg/kg/day of BNZ-nps survived until euthanasia (92 days post infection (dpi)), while only 15% of infected untreated mice survived until the end of the experiment. PCR analysis of blood samples taken after induction of immunosuppression showed that a dosage of 25 mg/kg/day rendered 40% of the mice PCR-negative. The histological analysis of heart tissue showed a significant decrease in inflammation after treatments with 25 and 50 mg/kg/day, while a similar inflammatory damage was observed in both infected mice treated with R-BNZ (50 mg/kg/day) and untreated mice. In addition, only BNZ-nps treated mice led to lower levels of T. cruzi-specific antibodies to 50–100%. Finally, mammalian Vero cells treated with BNZ-nps or R-BNZ lead to a significant increase in ROS production.

Conclusions

Based on these findings, this research highlights the in-vitro/in-vivo efficacy of nanoformulated BNZ against T. cruzi acute infections in immunosuppressed and non-immunosuppressed mice and provides further evidence for the optimization of dosage regimens to treat Chagas disease.

Chagas disease is a neglected parasitic infection caused by the protozoan Trypanosoma cruzi (T. cruzi) that affects more than 6 million people, mainly in Latin America. Benznidazole is still the drug of choice in many countries to treat it in spite of its dosage regimen and adverse side effects such as such as allergic dermatitis, peripheral neuropathy and anorexia. In this study, the efficacy of low doses of benznidazole, formulated as nanoparticles, against T. cruzi acute infections in immunosuppressed and non-immunosuppressed mice was investigated in order to establish future treatment strategies. In-vivo experiments showed that all infected mice treated with low doses of nanoformulated benznidazole survived until the end of the assay (92 dpi), while only 15% of infected untreated mice survived to the end of the same period of time. Moreover, such novel formulation was able to decrease the parasite burden and, consequently, heart inflammation and lesions were significantly reduced. Clearly, low doses of benznidazole exhibited, at least, the same efficacy in infected mice as the usual dose, confirming the usefulness of nanoformulated benznidazole for an improved treatment of Chagas disease.

Carbonic anhydrases from Trypanosoma and Leishmania as anti-protozoan drug targets

Trypanosoma cruzi and Leishmania spp. are protozoa of the Trypanosomatidae family, being the etiological agents of two widespread parasitic diseases, Chagas disease and leishmaniasis, respectively. Both parasites are the focus of worldwide research with the aim to find effective and less toxic drugs than the few ones available so far, and for controlling the spread of the diseases. Carbonic anhydrases (CAs, EC 4.2.1.1) belonging to the α- and β-class were recently identified in these protozoans and several studies suggested that they could be new targets for drug development. Sulfonamide, thiol and hydroxamate inhibitors effectively inhibited the α-CA from T. cruzi (TcCA) and the β-CA from L. donovani chagasi (LdccCA) in vitro, and some of them also showed in vivo efficacy in inhibiting the growth of the parasites in animal models of Chagas disease and leishmaniasis. As few therapeutic options are presently available for these orphan diseases, protozoan CA inhibition may represent a novel strategy to address this stringent health problem.

Promising Efficacy of Benznidazole Nanoparticles in Acute Trypanosoma cruzi Murine Model: In-Vitro and In-Vivo Studies

The aim of this study was to evaluate the effectiveness of benznidazole nanoparticles (BNZ-nps) on trypomastigote forms and on intracellular infection in mammalian cells and primary cardiac myocyte cells. Its effectiveness was also evaluated on acute Trypanosoma cruzi Nicaragua mice infection. Trypomastigotes from culture were treated with different concentrations of BNZ-nps to determine the drug concentration that lyses 50% of trypomastigotes (LC50). Infected mammalian cells were incubated with different concentrations of BNZ-nps to determine the percentage of amastigote inhibition. C3H/HeN mice with lethal acute infection were treated with 10, 25, and 50 mg/kg/day of BNZ-nps for 30 and 15 days to control the survival rate of animals. BNZ-nps having a mean particle size of 63.3 nm, a size distribution of 3.35, and a zeta potential of -18.30 were successfully prepared using poloxamer 188 as a stabilizer. BNZ-nps 25 and 50 μg/mL showed no significant differences in the percentage of inhibition of infected mammalian cells. Infected mice treated with BNZ-nps (50, 25, and 10 mg/kg/day) for 30 days and with BNZ-nps (50 and 25 mg/kg/day) for 15 days presented a 100% survival, whereas the animals treated with 10 mg/kg/day for 15 days of BNZ-nps showed a 70% survival rate. The results obtained demonstrate, for the first time, that benznidazole nanoparticles are a useful and attractive approach to treat Chagas disease in infected mice.

Chagas disease in solid organ and heart transplantation

PURPOSE OF REVIEW

The diagnosis and management of acute and chronic infections with the microorganism Trypanosoma cruzi, which causes Chagas disease, is important in solid organ transplantation in both endemic and nonendemic countries. In this review, we examine recently published data on the topic of Chagas disease in solid organ transplantation, with an emphasis on data relevant to heart transplantation.

RECENT FINDINGS

Most people with chronic T. cruzi infection have the intermediate form of disease, but approximately 2% of infected persons will progress to Chagas cardiomyopathy per year. The risk of T. cruzi transmission with liver or kidney transplantation appears to be substantially less than that with heart transplantation. For patients with Chagas cardiomyopathy undergoing heart transplant, a structured clinical and laboratory monitoring protocol is necessary to monitor for T. cruzi reactivation. Recent data indicate that laboratory monitoring of peripheral blood with polymerase chain reaction testing can identify reactivation prior to the occurrence of symptoms and allograft injury.

SUMMARY

Transplant clinicians should exercise vigilance in surveillance for Chagas disease in both organ donors and recipients. Although Chagas disease may seem uncommon, it is pervasive in endemic and several nonendemic countries, including the United States and Spain.