Benznidazole, itraconazole and their combination in the treatment of acute experimental chagas disease in dogs

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.

Positive clinical outcome using a modified dosing regimen of benznidazole in dogs at high risk for infection or acutely infected with Trypanosoma cruzi

Trypanosoma cruzi infection in dogs can cause heart failure and sudden death with few treatment options available. A litter of 4 dogs living in a T cruzi endemic area were randomized to prophylaxis and nonprophylaxis groups as part of a study evaluating a modified benznidazole dosing regimen administered twice weekly to prevent T cruzi infection during a vector transmission season. The 2 dogs that received prophylaxis remained healthy without T cruzi infection or cardiac disease for >2 years. One dog that did not receive prophylaxis died unexpectedly with acute T cruzi-induced pancarditis, and the second dog tested positive for T cruzi and developed complex arrhythmias with markedly increased cardiac troponin I and improved with a higher benznidazole treatment dose. Although the small sample size precludes definitive conclusions, we describe the potential clinical benefit of prophylactic and early treatment with modified benznidazole dosing regimens for dogs with T cruzi infection.

Chagas Disease: A Silent Threat for Dogs and Humans

Chagas disease (CD) is a vector-borne Neglected Zoonotic Disease (NZD) caused by a flagellate protozoan, Trypanosoma cruzi, that affects various mammalian species across America, including humans and domestic animals. However, due to an increase in population movements and new routes of transmission, T. cruzi infection is presently considered a worldwide health concern, no longer restricted to endemic countries. Dogs play a major role in the domestic cycle by acting very efficiently as reservoirs and allowing the perpetuation of parasite transmission in endemic areas. Despite the significant progress made in recent years, still there is no vaccine against human and animal disease, there are few drugs available for the treatment of human CD, and there is no standard protocol for the treatment of canine CD. In this review, we highlight human and canine Chagas Disease in its different dimensions and interconnections. Dogs, which are considered to be the most important peridomestic reservoir and sentinel for the transmission of T. cruzi infection in a community, develop CD that is clinically similar to human CD. Therefore, an integrative approach, based on the One Health concept, bringing together the advances in genomics, immunology, and epidemiology can lead to the effective development of vaccines, new treatments, and innovative control strategies to tackle CD.

Prophylactic low-dose, bi-weekly benznidazole treatment fails to prevent Trypanosoma cruzi infection in dogs under intense transmission pressure

Trypanosoma cruzi naturally infects a wide variety of wild and domesticated mammals, in addition to humans. Depending on the infection dose and other factors, the acute infection can be life-threatening, and in all cases, the risk of chagasic heart disease is high in persistently infected hosts. Domestic, working, and semi-feral dogs in the Americas are at significant risk of T. cruzi infection and in certain settings in the southern United States, the risk of new infections can exceed 30% per year, even with the use of vector control protocols. In this study, we explored whether intermittent low-dose treatment with the trypanocidal compound benznidazole (BNZ) during the transmission season, could alter the number of new infections in dogs in an area of known, intense transmission pressure. Preliminary studies in mice suggested that twice-weekly administration of BNZ could prevent or truncate infections when parasites were delivered at the mid-point between BNZ doses. Pre-transmission season screening of 126 dogs identified 53 dogs (42.1%) as T. cruzi infection positive, based upon blood PCR and Luminex-based serology. Serial monitoring of the 67 uninfected dogs during the high transmission season (May to October) revealed 15 (22.4%) new infections, 6 in the untreated control group and 9 in the group receiving BNZ prophylaxis, indicating no impact of this prophylaxis regimen on the incidence of new infections. Although these studies suggest that rigorously timed and more potent dosing regimen may be needed to achieve an immediate benefit of prophylaxis, additional studies would be needed to determine if drug prophylaxis reduced disease severity despite this failure to prevent new infections.

Benznidazole, itraconazole, and their combination for the treatment of chronic experimental Chagas disease in dogs

Treatment for Chagas disease has limited efficacy in the chronic phase. We evaluated benznidazole (BZ) and itraconazole (ITZ) individually and in association in dogs 16 months after infection with a BZ-resistant Trypanosoma cruzi strain. Four study groups (20 animals) were evaluated and treated for 60 days with BZ, ITZ, or BZ + ITZ, and maintained in parallel to control group infected and not treated (INT). All dogs were evaluated in the first, sixth, 12th, 18th and 24th months of study. Polymerase chain reaction (PCR) was negative in 2 of 3 animals in the BZ + ITZ group, 2 of 5 in the BZ group, and 4 of 5 in the ITZ group. Hemoculture performed in the 24th month was negative in all groups. Enzyme-linked immunoassay remained reactive in all treated animals. Echocardiography differentiated treated animals from control animals. Quantitative PCR analysis of cardiac tissue was negative in the BZ + ITZ and BZ groups, positive in 2 of 5 dogs in the ITZ group and in 2 of 3 dogs in the control group, but negative in colon tissue in all groups. Inflammation was significantly reduced in the right atrium and left ventricle of dogs treated with BZ + ITZ and BZ compared with those receiving ITZ alone. Fibrosis was absent in most dogs treated with BZ + ITZ, mild in those treated with BZ or ITZ alone, and intense in the control group. Parasitological and histopathological evaluations showed that BZ + ITZ treatment improved or stabilized the clinical condition of the dogs.

Antiparasitic treatment with itraconazole and amiodarone in 2 dogs with severe, symptomatic Chagas cardiomyopathy

Chagas cardiomyopathy, caused by the protozoal parasite Trypanosoma cruzi, is characterized by arrhythmias, myocardial damage, heart failure, and sudden death. We describe 2 dogs with severe, symptomatic Chagas cardiomyopathy characterized by myocardial dysfunction and electrocardiographic abnormalities that were managed with a combination of cardiac medications and antiparasitic treatment with itraconazole and amiodarone. Both dogs died suddenly within 6 months of diagnosis. These cases highlight the need for early detection of Chagas disease in dogs and continued research to develop effective antiparasitic treatment protocols.

Drug associations as alternative and complementary therapy for neglected tropical diseases

The present paper aims to establish different treatments for neglected tropical disease by a survey on drug conjugations and possible fixed-dose combinations (FDC) used to obtain alternative, safer and more effective treatments. The source databases used were Science Direct and PubMed/Medline, in the intervals between 2015 and 2021 with the drugs key-words or diseases, like "schistosomiasis", "praziquantel", "malaria", "artesunate", "Chagas' disease", "benznidazole", "filariasis", diethylcarbamazine", "ivermectin", " albendazole". 118 works were the object of intense analysis, other articles and documents were used to increase the quality of the studies, such as consensuses for harmonizing therapeutics and historical articles. As a result, an effective NTD control can be achieved when different public health approaches are combined with interventions guided by the epidemiology of each location and the availability of appropriate measures to detect, prevent and control disease. It was also possible to verify that the FDCs promote a simplification of the therapeutic regimen, which promotes better patient compliance and enables a reduction in the development of parasitic resistance, requiring further studies aimed at resistant strains, since the combined APIs usually act by different mechanisms or at different target sites. In addition to eliminating the process of developing a new drug based on the identification and validation of active compounds, which is a complex, long process and requires a strong long-term investment, other advantages that FDCs have are related to productive gain and gain from the industrial plant, which can favor and encourage the R&D of new FDCs not only for NTDs but also for other diseases that require the use of more than one drug.

Dogs as a Model for Chemotherapy of Chagas Disease and Leishmaniasis

BACKGROUND

Dogs are natural reservoir of Chagas disease (CD) and leishmaniasis and have been used for studies of these infections as they develop different clinical forms of these diseases similar to humans.

OBJECTIVE

This article describes publications on the dog model relative to CD and leishmaniasis chemotherapy.

METHODS

The search of articles was based on PubMed, Scopus and MESH using the keywords: dog, Trypanosoma cruzi, treatment (T. cruzi chemotherapy analysis), Leishmania chagasi, Leishmania infantum, canine visceral leishmaniasis, treatment (Leishmania chemotherapy evaluation).

RESULTS

Benznidazole and nifurtimox were used as a reference in the treatment of CD and in combination with other compounds. Eleven out of the fifteen studies have authors from the same team, using similar protocols and post-treatment evaluations, which assured more reproducibility and credibility. Twenty leishmaniasis studies, especially on visceral leishmaniasis, presenting at least one parasitological analysis tested in distinct monochemotherapy and polychemotherapy approaches were accessed. Data demonstrated that polychemotherapy was more effective in improving the clinical signs and parasitism control.

CONCLUSION

The benefits of treatment in terms of reducing or eliminating lesions and/or cardiac dysfunctions were demonstrated at acute and/or chronic phases relative to parasite load and/or the T. cruzi strain resistance to treatment. BZ presented better therapeutic results than the two EBI compounds evaluated. Although treatment of the canine visceral leishmaniasis was not able to induce complete parasite clearance, it can improve clinical recovery. Thus, the dog is a good model for CD and leishmaniasis studies of chemotherapy and may be indicated for pre-clinical trials of new treatments.

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.

Anticancer and antitrypanosomal activities of trinuclear ruthenium compounds with orthometalated phenazine ligands

Trinuclear ruthenium complexes with orthometalated phenazines of general formula [Ru3(μ3-O)(μ2-OAc)5(L)(py)2]PF6 (L = dppn, benzo[i]dipyrido[3,2-a:2',3'-c]phenazine, 1; dppz, dipyrido[3,2-a:2',3'-c]phenazine, 2; CH3-dppz, 7-methyldipyrido[3,2-a:2',3'-c]phenazine, 3; Cl-dppz, 7-chlorodipyrido[3,2-a:2',3'-c]phenazine, 4) were investigated for their cytotoxic activity toward the B16F10 murine melanoma and the L929 non-cancer cell lines and against Trypanosoma cruzi (2-4). This study also reports a multi-technique investigation into how complexes 1-4 interact with DNA and human serum albumin, HSA. At concentrations ranging from 2 to 50 μM, all the complexes reduced B16F10 murine melanoma cell viability by over 50%. Complex 4 had the highest cytotoxic effect in the series, diminishing B16F10 cell viability to 38% at 2 μM, with an overall order for anticancer activity of 4 > 2 > 3 > 1. Complexes 2-4 showed remarkable activity in inhibiting epimastigote and amastigote forms of T. cruzi. Complex 2 showed better antitrypanosomal activity than the reference drug (IC50 = 1.19 μM and IC50 = 0.25 μM for epimastigote and amastigotes forms, respectivily). Ethidium bromide (EB) displacement assays showed that DNA intercalation progressively increases with the extension of the π-conjugation of the cyclometalating ligand and the presence of substituents in the phenazinic portion (1 > 4-3 > 2), showing that complex 1 is a stronger intercalator than EB itself (Kapp > 107 M-1). Viscosity measurements followed the same trend. Cytotoxicity against cancer cells and antitrypanosomal activity follow the same order, which is different to the tendency of DNA intercalation, suggesting DNA is not the main target of these complexes. Compound 1-4 showed very high affinity with HSA (Kb ∼109 M-1). Circular dichroism results also showed that the complexes alter significantly the secondary structure of the HSA, lowering the α-helix % from 86.2 (pure protein) to less than 5% for compounds 1, 2 and 4 at 2.8 μM. These findings demonstrated the important role of phenazines for the biological activity of triruthenium compounds.