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Planer J.D.,University of Washington | Hulverson M.A.,University of Washington | Arif J.A.,University of Washington | Ranade R.M.,University of Washington | And 2 more authors.
PLoS Neglected Tropical Diseases | Year: 2014

An estimated 8 million persons, mainly in Latin America, are infected with Trypanosoma cruzi, the etiologic agent of Chagas disease. Existing antiparasitic drugs for Chagas disease have significant toxicities and suboptimal effectiveness, hence new therapeutic strategies need to be devised to address this neglected tropical disease. Due to the high research and development costs of bringing new chemical entities to the clinic, we and others have investigated the strategy of repurposing existing drugs for Chagas disease. Screens of FDA-approved drugs (described in this paper) have revealed a variety of chemical classes that have growth inhibitory activity against mammalian stage Trypanosoma cruzi parasites. Aside from azole antifungal drugs that have low or sub-nanomolar activity, most of the active compounds revealed in these screens have effective concentrations causing 50% inhibition (EC50's) in the low micromolar or high nanomolar range. For example, we have identified an antihistamine (clemastine, EC50 of 0.4 μM), a selective serotonin reuptake inhibitor (fluoxetine, EC50 of 4.4 μM), and an antifolate drug (pyrimethamine, EC50 of 3.8 μM) and others. When tested alone in the murine model of Trypanosoma cruzi infection, most compounds had insufficient efficacy to lower parasitemia thus we investigated using combinations of compounds for additive or synergistic activity. Twenty-four active compounds were screened in vitro in all possible combinations. Follow up isobologram studies showed at least 8 drug pairs to have synergistic activity on T. cruzi growth. The combination of the calcium channel blocker, amlodipine, plus the antifungal drug, posaconazole, was found to be more effective at lowering parasitemia in mice than either drug alone, as was the combination of clemastine and posaconazole. Using combinations of FDA-approved drugs is a promising strategy for developing new treatments for Chagas disease. © 2014 Planer et al. Source


Diniz L.F.,Federal University of Ouro Preto | Urbina J.A.,Venezuelan Institute for Scientific Research | de Andrade I.M.,Federal University of Ouro Preto | Mazzeti A.L.,Federal University of Ouro Preto | And 5 more authors.
PLoS Neglected Tropical Diseases | Year: 2013

Background:Current chemotherapy for Chagas disease is unsatisfactory due to its limited efficacy, particularly in the chronic phase, with frequent side effects that can lead to treatment discontinuation. Combined therapy is envisioned as an ideal approach since it may improve treatment efficacy whilst decreasing toxicity and the likelihood of resistance development. We evaluated the efficacy of posaconazole in combination with benznidazole on Trypanosoma cruzi infection in vivo.Methods and Findings:Benznidazole and posaconazole were administered individually or in combination in an experimental acute murine infection model. Using a rapid treatment protocol for 7 days, the combined treatments were more efficacious in reducing parasitemia levels than the drugs given alone, with the effects most evident in combinations of sub-optimal doses of the drugs. Subsequently, the curative action of these drug combinations was investigated, using the same infection model and 25, 50, 75 or 100 mg/kg/day (mpk) of benznidazole in combination with 5, 10 or 20 mpk of posaconazole, given alone or concomitantly for 20 days. The effects of the combination treatments on parasitological cures were higher than the sum of such effects when the drugs were administered separately at the same doses, indicating synergistic activity. Finally, sequential therapy experiments were carried out with benznidazole or posaconazole over a short interval (10 days), followed by the second drug administered for the same period of time. It was found that the sequence of benznidazole (100 mpk) followed by posaconazole (20 mpk) provided cure rates comparable to those obtained with the full (20 days) treatments with either drug alone, and no cure was observed for the short treatments with drugs given alone.Conclusions:Our data demonstrate the importance of investigating the potential beneficial effects of combination treatments with marketed compounds, and showed that combinations of benznidazole with posaconazole have a positive interaction in murine models of Chagas disease. © 2013 Diniz et al. Source


Burrows J.N.,Medicines for Malaria Venture | Elliott R.L.,Bill and Melinda Gates Foundation | Kaneko T.,Global Alliance for TB Drug Development | Mowbray C.E.,Drugs for Neglected Diseases Initiative | Waterson D.,Medicines for Malaria Venture
MedChemComm | Year: 2014

Neglected and tropical diseases affect a large proportion of the world's population and impose a huge economic and health burden on developing countries. Despite this, there is a dearth of safe, effective, suitable medications for treatment of these diseases, largely as a result of an underinvestment in developing new drugs against these diseases by the majority of research-based pharmaceutical companies. In the past 12 years, the situation has begun to improve with the emergence of public-private product development partnerships (PDPs), which foster a collaborative approach to drug discovery and have established strong drug development pipelines for neglected and tropical diseases. Some large pharmaceutical companies have also now established dedicated research sites for developing world diseases and are working closely with PDPs on drug development activities. However, drug discovery in this field is still hampered by a lack of sufficient funding and technological investment, and there is a shortage of the tools, assays, and well-validated targets needed to ensure strong drug development pipelines in the future. The availability of high-quality chemically diverse compound libraries to enable lead discovery remains one of the critical bottlenecks. The pharmaceutical industry has much that it can share in terms of drug discovery capacity, know-how, and expertise, and in some cases has been moving towards new paradigms of collaborative pre-competitive research with the PDPs and partners. The future of drug discovery for neglected and tropical diseases will depend on the ability of those working in the area to collaborate together and will require sustained resourcing and focus. © 2014 the Partner Organisations. Source


van Griensven J.,Institute of Tropical Medicine | Balasegaram M.,Drugs for Neglected Diseases Initiative | Meheus F.,Institute of Tropical Medicine | Alvar J.,World Health Organization | And 2 more authors.
The Lancet Infectious Diseases | Year: 2010

Combination therapy for the treatment of visceral leishmaniasis has increasingly been advocated as a way to increase treatment efficacy and tolerance, reduce treatment duration and cost, and limit the emergence of drug resistance. We reviewed the evidence and potential for combination therapy, and the criteria for the choice of drugs in such regimens. The first phase 2 results of combination regimens are promising, and have identified effective and safe regimens as short as 8 days. Several phase 3 trials are underway or planned in the Indian subcontinent and east Africa. The limited data available suggest that combination therapy is more cost-effective and reduces indirect costs for patients. Additional advantages are reduced treatment duration (8-17 days), with potentially better patient compliance and lesser burden on the health system. Only limited data are available on how best to prevent acquired resistance. Patients who are coinfected with visceral leishmaniasis and HIV could be a reservoir for development and spread of drug-resistant strains, calling for special precautions. The identification of a short, cheap, well-tolerated combination regimen that can be given in ambulatory care and needs minimal clinical monitoring will most likely have important public health implications. Effective monitoring systems and close regulations and policy will be needed to ensure effective implementation. Whether combination therapy could indeed help delay resistance, and how this is best achieved, will only be known in the long term. © 2010 Elsevier Ltd. All rights reserved. Source


Brun R.,Swiss Tropical and Public Health Institute | Don R.,Drugs for Neglected Diseases Initiative | Jacobs R.T.,SCYNEXIS | Wang M.Z.,University of North Carolina at Chapel Hill | Barrett M.P.,University of Glasgow
Future Microbiology | Year: 2011

Human African trypanosomiasis (HAT) or 'sleeping sickness' is a neglected tropical disease caused by the parasite Trypanosoma brucei. Novel models for funding pharmaceutical development against HAT are beginning to yield results. The Drugs for Neglected Diseases initiative (DNDi) rediscovered a nitroimidazole, fexinidazole, which is currently in Phase I clinical trials. Novel benzoxaboroles, discovered by Anacor, Scynexis and DNDi, have good pharmacokinetic properties in plasma and in the brain and are curative in a murine model of stage two HAT with brain infection. The Consortium for Parasitic Drug Development (CPDD) has identified a series of dicationic compounds that can cure a monkey model of stage two HAT. With other screening programs yielding hits, the pipeline for new HAT drugs might finally begin to fill. © 2011 Future Medicine Ltd. Source

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