In Vivo Bioluminescence Imaging Reveals Differences in Leishmania infantum Parasite Killing Kinetics by Antileishmanial Reference Drugs.

The bioluminescent Leishmania infantum BALB/c mouse model was used to evaluate the parasiticidal drug action kinetics of the reference drugs miltefosine, paromomycin, sodium stibogluconate, and liposomal amphotericin B. Infected mice were treated for 5 days starting from 7 days post-infection, and parasite burdens were monitored over time via bioluminescence imaging (BLI). Using nonlinear regression analyses of the BLI signal, the parasite elimination half-life (t1/2) in the liver, bone marrow, and whole body was determined and compared for the different treatment regimens. Significant differences in parasiticidal kinetics were recorded. A single intravenous dose of 0.5 mg/kg liposomal amphotericin B was the fastest acting with a t1/2 of less than 1 day. Intraperitoneal injection of paromomycin at 320 mg/kg for 5 days proved to be the slowest with a t1/2 of about 5 days in the liver and 16 days in the bone marrow. To conclude, evaluation of the cidal kinetics of the different antileishmanial reference drugs revealed striking differences in their parasite elimination half-lives. This BLI approach also enables an in-depth pharmacodynamic comparison between novel drug leads and may constitute an essential tool for the design of potential drug combinations.

The translational challenge in Chagas disease drug development

Chagas disease is a neglected tropical disease caused by the protozoan parasite Trypanosoma cruzi. There is an urgent need for safe, effective, and accessible new treatments since the currently approved drugs have serious limitations. Drug development for Chagas disease has historically been hampered by the complexity of the disease, critical knowledge gaps, and lack of coordinated R&D efforts. This review covers some of the translational challenges associated with the progression of new chemical entities from preclinical to clinical phases of development, and discusses how recent technological advances might allow the research community to answer key questions relevant to the disease and to overcome hurdles in R&D for Chagas disease.

Heteroaryl ether analogues of an antileishmanial 7-substituted 2-nitroimidazooxazine lead afford attenuated hERG risk: In vitro and in vivo appraisal.

Previous investigation of the potent antileishmanial properties of antitubercular 7-substituted 2-nitroimidazo[2,1-b][1,3]oxazines with biaryl side chains led to our development of a new clinical candidate for visceral leishmaniasis (DNDI-0690). Within a collaborative backup program, a racemic monoaryl lead (3) possessing comparable activity in mice but a greater hERG liability formed the starting point for our pursuit of efficacious second generation analogues having good solubility and safety. Asymmetric synthesis and appraisal of its enantiomers first established that chiral preferences for in vivo efficacy were species dependent and that neither form afforded a reduced hERG risk. However, in line with our findings in a structurally related series, less lipophilic heteroaryl ethers provided significant solubility enhancements (up to 16-fold) and concomitantly attenuated hERG inhibition. One promising pyridine derivative (49) displayed 100% oral bioavailability in mice and delivered a 96% parasite burden reduction when dosed at 50 mg/kg in a Leishmania donovani mouse model of visceral leishmaniasis.

A Spontaneous Regression of an Isolated Lymph Node Metastasis from a Primary Unknown Merkel Cell Carcinoma in a Patient with an Idiopathic Hyper-Eosinophilic Syndrome.

BACKGROUND Merkel cell carcinoma (MCC) is a rare, aggressive primary cutaneous neuroendocrine tumor frequently associated with Merkel cell polyomavirus infection. Despite its aggressiveness, a few reports of spontaneous MCC regression have been described in the literature, most of them following incisional biopsy supporting a hypothetical role of surgery-induced inflammation in the process of regression. CASE REPORT We report a case of 69-year-old Caucasian male who was followed for an idiopathic hyper-eosinophilic syndrome. A positron emission tomography (PET) scan documented a hyper-metabolic, left, inguinal adenopathy, histologically corresponding to a metastasis of a poorly differentiated neuroendocrine carcinoma. This lesion spontaneously regressed at clinical examination and radiological imaging. After its excisional dissection, histology was negative. Five months later, a nearby adenopathy reappeared. The patient underwent another excisional biopsy. Histology and immunohistochemistry were compatible with a lymph node metastasis of a MCC. As the patient refused radical surgery, a regional radiotherapy was performed. As of a follow-up at 10 months, he was alive and free of tumor recurrence. The hyper-eosinophilic syndrome was stable; however, the serum levels of chromogranin-A were inexplicably elevated in the absence of any tumor evidence at the PET scan. CONCLUSIONS The particularity of this case relies on the rarity of MCC complete spontaneous regression in a patient without a primary tumor and with a synchronous, idiopathic hyper-eosinophilic syndrome.

Peritoneal Myeloid Sarcoma in a Patient Treated for a Testicular Seminoma.

BACKGROUND Myeloid sarcoma is a rare extramedullary soft tissue neoplasm composed of myeloblastic cells, usually associated to hematologic tumor disorders and a poor prognosis. Its diagnosis is very difficult as radiological images are not specific. Histology and immunohistochemistry are necessary for an accurate diagnosis. CASE REPORT We report the case of 46-year-old, Caucasian, non-smoker male, treated in 2014 by orchiectomy and systemic chemotherapy for a stage IIB testicular seminoma. Considering the rapid increase of lactate dehydrogenase (LDH) levels without any evident medical reason, a computed tomography/positron emission tomography (CT/PET) scan was performed and revealing a diffuse, nodular, peritoneal tumor infiltration associated with multiple mesenteric and mediastinal adenopathies. Laparoscopy confirmed a diffuse tumor infiltration of the peritoneum. Histology and immunohistochemistry were consisted with the diagnosis of a myeloid monoblastic sarcoma. Cytology of bone marrow documented an monocytic acute myeloid leukemia. The patient started a systemic induction chemotherapy with high dose cytarabine and idarubicin that was complicated by an infectious pneumonia and colitis, and a grade IV thrombocytopenia leading to a brain subdural hemorrhage and quickly to patient's death. CONCLUSIONS We describe a rare, peritoneal, myeloid sarcoma in a young patient who had been treated by systemic chemotherapy for testicular seminoma 4 years earlier. The patient was clinically asymptomatic and presented only elevated LDH levels without any evident clinical reason. Considering the persistence of this biochemical abnormality, more investigations were performed leading to a diagnosis of peritoneal myeloid sarcoma associated with monocytic acute myeloid leukemia, probably secondary to the past chemotherapy.

Catechol pyrazolinones as trypanocidals: fragment-based design, synthesis, and pharmacological evaluation of nanomolar inhibitors of trypanosomal phosphodiesterase B1.

Trypanosomal phosphodiesterases B1 and B2 (TbrPDEB1 and TbrPDEB2) play an important role in the life cycle of Trypanosoma brucei, the causative parasite of human African trypanosomiasis (HAT), also known as African sleeping sickness. We used homology modeling and docking studies to guide fragment growing into the parasite-specific P-pocket in the enzyme binding site. The resulting catechol pyrazolinones act as potent TbrPDEB1 inhibitors with IC50 values down to 49 nM. The compounds also block parasite proliferation (e.g., VUF13525 (20b): T. brucei rhodesiense IC50 = 60 nM, T. brucei brucei IC50 = 520 nM, T. cruzi = 7.6 µM), inducing a typical multiple nuclei and kinetoplast phenotype without being generally cytotoxic. The mode of action of 20b was investigated with recombinantly engineered trypanosomes expressing a cAMP-sensitive FRET sensor, confirming a dose-response related increase of intracellular cAMP levels in trypanosomes. Our findings further validate the TbrPDEB family as antitrypanosomal target.

An image-based high-content screening assay for compounds targeting intracellular Leishmania donovani amastigotes in human macrophages.

Leishmaniasis is a tropical disease threatening 350 million people from endemic regions. The available drugs for treatment are inadequate, with limitations such as serious side effects, parasite resistance or high cost. Driven by this need for new drugs, we developed a high-content, high-throughput image-based screening assay targeting the intracellular amastigote stage of different species of Leishmania in infected human macrophages. The in vitro infection protocol was adapted to a 384-well-plate format, enabling acquisition of a large amount of readouts by automated confocal microscopy. The reading method was based on DNA staining and required the development of a customized algorithm to analyze the images, which enabled the use of non-modified parasites. The automated analysis generated parameters used to quantify compound activity, including infection ratio as well as the number of intracellular amastigote parasites and yielded cytotoxicity information based on the number of host cells. Comparison of this assay with one that used the promastigote form to screen 26,500 compounds showed that 50% of the hits selected against the intracellular amastigote were not selected in the promastigote screening. These data corroborate the idea that the intracellular amastigote form of the parasite is the most appropriate to be used in primary screening assay for Leishmania.

Antileishmanial high-throughput drug screening reveals drug candidates with new scaffolds.

Drugs currently available for leishmaniasis treatment often show parasite resistance, highly toxic side effects and prohibitive costs commonly incompatible with patients from the tropical endemic countries. In this sense, there is an urgent need for new drugs as a treatment solution for this neglected disease. Here we show the development and implementation of an automated high-throughput viability screening assay for the discovery of new drugs against Leishmania. Assay validation was done with Leishmania promastigote forms, including the screening of 4,000 compounds with known pharmacological properties. In an attempt to find new compounds with leishmanicidal properties, 26,500 structurally diverse chemical compounds were screened. A cut-off of 70% growth inhibition in the primary screening led to the identification of 567 active compounds. Cellular toxicity and selectivity were responsible for the exclusion of 78% of the pre-selected compounds. The activity of the remaining 124 compounds was confirmed against the intramacrophagic amastigote form of the parasite. In vitro microsomal stability and cytochrome P450 (CYP) inhibition of the two most active compounds from this screening effort were assessed to obtain preliminary information on their metabolism in the host. The HTS approach employed here resulted in the discovery of two new antileishmanial compounds, bringing promising candidates to the leishmaniasis drug discovery pipeline.

In vitro and in vivo experimental models for drug screening and development for Chagas disease

Chagas disease, a neglected illness, affects nearly 12-14 million people in endemic areas of Latin America. Although the occurrence of acute cases sharply has declined due to Southern Cone Initiative efforts to control vector transmission, there still remain serious challenges, including the maintenance of sustainable public policies for Chagas disease control and the urgent need for better drugs to treat chagasic patients. Since the introduction of benznidazole and nifurtimox approximately 40 years ago, many natural and synthetic compounds have been assayed against Trypanosoma cruzi, yet only a few compounds have advanced to clinical trials. This reflects, at least in part, the lack of consensus regarding appropriate in vitro and in vivo screening protocols as well as the lack of biomarkers for treating parasitaemia. The development of more effective drugs requires (i) the identification and validation of parasite targets, (ii) compounds to be screened against the targets or the whole parasite and (iii) a panel of minimum standardised procedures to advance leading compounds to clinical trials. This third aim was the topic of the workshop entitled Experimental Models in Drug Screening and Development for Chagas Disease, held in Rio de Janeiro, Brazil, on the 25th and 26th of November 2008 by the Fiocruz Program for Research and Technological Development on Chagas Disease and Drugs for Neglected Diseases Initiative. During the meeting, the minimum steps, requirements and decision gates for the determination of the efficacy of novel drugs for T. cruzi control were evaluated by interdisciplinary experts and an in vitro and in vivo flowchart was designed to serve as a general and standardised protocol for screening potential drugs for the treatment of Chagas disease.