Bioluminescence imaging reveals enhanced SARS-CoV-2 clearance in mice with combinatorial regimens

Direct acting antivirals (DAAs) represent critical tools for combating severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants of concern (VOCs) that have escaped vaccine-elicited spike-based immunity and future coronaviruses with pandemic potential. Here, we used bioluminescence imaging to evaluate therapeutic efficacy of DAAs that target SARS-CoV-2 RNA-dependent RNA polymerase (favipiravir, molnupiravir) or main protease (nirmatrelvir) against Delta or Omicron VOCs in K18-hACE2 mice. Nirmatrelvir displayed the best efficacy followed by molnupiravir and favipiravir in suppressing viral loads in the lung. Unlike neutralizing antibody treatment, DAA monotherapy regimens did not eradicate SARS-CoV-2 in mice, but combining molnupiravir with nirmatrelvir exhibited superior additive efficacy and led to virus clearance. Furthermore, combining molnupiravir with caspase-1/4 inhibitor mitigated inflammation and lung pathology whereas combining molnupiravir with COVID-19 convalescent plasma demonstrated synergy, rapid virus clearance, and 100% survival. Thus, our study provides insights into in vivo treatment efficacies of DAAs and other effective combinations to bolster COVID-19 therapeutic arsenal.

Generation and evaluation of protease inhibitor-resistant SARS-CoV-2 strains

Since the start of the SARS-CoV-2 pandemic, the search for antiviral therapies has been at the forefront of medical research. To date, the 3CLpro inhibitor nirmatrelvir (Paxlovid®) has shown the best results in clinical trials and the greatest robustness against variants. A second SARS-CoV-2 protease inhibitor, ensitrelvir (Xocova®), has been developed. Ensitrelvir, currently in Phase 3, was approved in Japan under the emergency regulatory approval procedure in November 2022, and is available since March 31, 2023. One of the limitations for the use of antiviral monotherapies is the emergence of resistance mutations. Here, we experimentally generated mutants resistant to nirmatrelvir and ensitrelvir in vitro following repeating passages of SARS-CoV-2 in the presence of both antivirals. For both molecules, we demonstrated a loss of sensitivity for resistance mutants in vitro. Using a Syrian golden hamster infection model, we showed that the ensitrelvir M49L mutation, in the multi-passage strain, confers a high level of in vivo resistance. Finally, we identified a recent increase in the prevalence of M49L-carrying sequences, which appears to be associated with multiple repeated emergence events in Japan and may be related to the use of Xocova® in the country since November 2022. These results highlight the strategic importance of genetic monitoring of circulating SARS-CoV-2 strains to ensure that treatments administered retain their full effectiveness.

Lack of antiviral activity of probenecid in vitro and in Syrian golden hamsters

OBJECTIVES

Antiviral interventions are required to complement vaccination programmes and reduce the global burden of COVID-19. Prior to initiation of large-scale clinical trials, robust preclinical data to support candidate plausibility are required. This work sought to further investigate the putative antiviral activity of probenecid against SARS-CoV-2.

METHODS

Vero E6 cells were preincubated with probenecid, or control media for 2 h before infection (SARS-CoV-2/Human/Liverpool/REMRQ0001/2020). Probenecid or control media was reapplied, plates reincubated and cytopathic activity quantified by spectrophotometry after 48 h. In vitro human airway epithelial cell (HAEC) assays were performed for probenecid against SARS-CoV-2-VoC-B.1.1.7 (hCoV-19/Belgium/rega-12211513/2020; EPI_ISL_791333, 2020-12-21) using an optimized cell model for antiviral testing. Syrian golden hamsters were intranasally inoculated (SARS-CoV-2 Delta B.1.617.2) 24 h prior to treatment with probenecid or vehicle for four twice-daily doses.

RESULTS

No observable antiviral activity for probenecid was evident in Vero E6 or HAEC assays. No reduction in total or subgenomic RNA was observed in terminal lung samples (P > 0.05) from hamsters. Body weight of uninfected hamsters remained stable whereas both probenecid- and vehicle-treated infected hamsters lost body weight (P > 0.5).

CONCLUSIONS

These data do not support probenecid as a SARS-CoV-2 antiviral drug.

Short-course combination treatment for experimental chronic Chagas disease

Chagas disease, caused by the protozoan parasite Trypanosoma cruzi, affects millions of people in the Americas and across the world, leading to considerable morbidity and mortality. Current treatment options, benznidazole (BNZ) and nifurtimox, offer limited efficacy and often lead to adverse side effects because of long treatment durations. Better treatment options are therefore urgently required. Here, we describe a pyrrolopyrimidine series, identified through phenotypic screening, that offers an opportunity to improve on current treatments. In vitro cell-based washout assays demonstrate that compounds in the series are incapable of killing all parasites; however, combining these pyrrolopyrimidines with a subefficacious dose of BNZ can clear all parasites in vitro after 5 days. These findings were replicated in a clinically predictive in vivo model of chronic Chagas disease, where 5 days of treatment with the combination was sufficient to prevent parasite relapse. Comprehensive mechanism of action studies, supported by ligand-structure modeling, show that compounds from this pyrrolopyrimidine series inhibit the Qi active site of T. cruzi cytochrome b, part of the cytochrome bc1 complex of the electron transport chain. Knowledge of the molecular target enabled a cascade of assays to be assembled to evaluate selectivity over the human cytochrome b homolog. As a result, a highly selective and efficacious lead compound was identified. The combination of our lead compound with BNZ rapidly clears T. cruzi parasites, both in vitro and in vivo, and shows great potential to overcome key issues associated with currently available treatments.

DNDI-6174 is a preclinical candidate for visceral leishmaniasis that targets the cytochrome bc1

New drugs for visceral leishmaniasis that are safe, low cost, and adapted to the field are urgently required. Despite concerted efforts over the last several years, the number of new chemical entities that are suitable for clinical development for the treatment of Leishmania remains low. Here, we describe the discovery and preclinical development of DNDI-6174, an inhibitor of Leishmania cytochrome bc1 complex activity that originated from a phenotypically identified pyrrolopyrimidine series. This compound fulfills all target candidate profile criteria required for progression into preclinical development. In addition to good metabolic stability and pharmacokinetic properties, DNDI-6174 demonstrates potent in vitro activity against a variety of Leishmania species and can reduce parasite burden in animal models of infection, with the potential to approach sterile cure. No major flags were identified in preliminary safety studies, including an exploratory 14-day toxicology study in the rat. DNDI-6174 is a cytochrome bc1 complex inhibitor with acceptable development properties to enter preclinical development for visceral leishmaniasis.

State-of-the-Art in the Drug Discovery Pathway for Chagas Disease: A Framework for Drug Development and Target Validation

Chagas disease is the most important protozoan infection in the Americas, and constitutes a significant public health concern throughout the world. Development of new medications against its etiologic agent, Trypanosoma cruzi, has been traditionally slow and difficult, lagging in comparison with diseases caused by other kinetoplastid parasites. Among the factors that explain this are the incompletely understood mechanisms of pathogenesis of T. cruzi infection and its complex set of interactions with the host in the chronic stage of the disease. These demand the performance of a variety of in vitro and in vivo assays as part of any drug development effort. In this review, we discuss recent breakthroughs in the understanding of the parasite's life cycle and their implications in the search for new chemotherapeutics. For this, we present a framework to guide drug discovery efforts against Chagas disease, considering state-of-the-art preclinical models and recently developed tools for the identification and validation of molecular targets.

Combinatorial Regimens Augment Drug Monotherapy for SARS-CoV-2 Clearance in Mice

Direct acting antivirals (DAAs) represent critical tools for combating SARS-CoV-2 variants of concern (VOCs) that evolve to escape spike-based immunity and future coronaviruses with pandemic potential. Here, we used bioluminescence imaging to evaluate therapeutic efficacy of DAAs that target SARS-CoV-2 RNA-dependent RNA polymerase (favipiravir, molnupiravir) or Main protease (nirmatrelvir) against Delta or Omicron VOCs in K18-hACE2 mice. Nirmatrelvir displayed the best efficacy followed by molnupiravir and favipiravir in suppressing viral loads in the lung. Unlike neutralizing antibody treatment, DAA monotherapy did not eliminate SARS-CoV-2 in mice. However, targeting two viral enzymes by combining molnupiravir with nirmatrelvir resulted in superior efficacy and virus clearance. Furthermore, combining molnupiravir with Caspase-1/4 inhibitor mitigated inflammation and lung pathology whereas combining molnupiravir with COVID-19 convalescent plasma yielded rapid virus clearance and 100% survival. Thus, our study provides insights into treatment efficacies of DAAs and other effective combinations to bolster COVID-19 therapeutic arsenal.

Long-term cardiology outcomes in children after early treatment for Chagas disease, an observational study

BACKGROUND

Parasite persistence after acute infection with Trypanosoma cruzi is an important factor in the development of Chagas disease (CD) cardiomyopathy. Few studies have investigated the clinical effectiveness of CD treatment through the evaluation of cardiological events by long term follow-up of treated children. Cardiological evaluation in children is challenging since features that would be diagnosed as abnormal in an adult's ECG may be normal, age-related findings in a pediatric ECG trace. The objective was to evaluate cardiac involvement in patients with Chagas disease with a minimum follow-up of 6 years post-treatment.

METHODOLOGY

A descriptive study of a cohort of pediatric patients with CD treated with benznidazole (Bz) or nifurtimox (Nf) was conducted. Children (N = 234) with at least 6 years post CD treatment followed at the Parasitology and Chagas Service, Buenos Aires Children's Hospital (Argentina) were enrolled. By convenience sampling, children who attended a clinical visit between August 2015 and November 2019 were also invited to participate for additional cardiovascular studies like 24-hour Holter monitoring and speckle-tracking 2D echocardiogram (STE). Benznidazole was prescribed in 171 patients and nifurtimox in 63 patients. Baseline parasitemia data was available for 168/234 patients. During the follow-up period, alterations in routine ECG were observed in 11/234 (4.7%, 95% CI [2-7.4%]) patients. In only four patients, with complete right bundle branch block (cRBBB) and left anterior fascicular block (LAFB), ECG alterations were considered probably related to CD. During follow-up, 129/130 (99%) treated patients achieved persistent negative parasitemia by qPCR. Also decrease in T.cruzi antibodies titers was observed in all patients and negative seroconversion occurred in 123/234 (52%) patients.

CONCLUSIONS

A low incidence of cardiological lesions related to CD was observed in patients treated early for pediatric CD. This suggests a protective effect of parasiticidal treatment on the development of cardiological lesions and highlights the importance of early treatment of infected children.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04090489.

New metabolic signature for Chagas disease reveals sex steroid perturbation in humans and mice

The causative agent of Chagas disease (CD), Trypanosoma cruzi, claims thousands of lives each year. Current diagnostic tools are insufficient to ensure parasitological detection in chronically infected patients has been achieved. A host-derived metabolic signature able to distinguish CD patients from uninfected individuals and assess antiparasitic treatment efficiency is introduced. Serum samples were collected from chronic CD patients, prior to and three years after treatment, and subjected to untargeted metabolomics analysis against demographically matched CD-negative controls. Five metabolites were confirmed by high-resolution tandem mass spectrometry. Several database matches for sex steroids were significantly altered in CD patients. A murine experiment corroborated sex steroid perturbation in T. cruzi-infected mice, particularly in male animals. Proteomics analysis also found increased steroidogenesis in the testes of infected mice. Metabolic alterations identified in this study shed light on the pathogenesis and provide the basis for developing novel assays for the diagnosis and screening of CD patients.

Comparing in vivo bioluminescence imaging and the Multi-Cruzi immunoassay platform to develop improved Chagas disease diagnostic procedures and biomarkers for monitoring parasitological cure

BACKGROUND

Chagas disease is caused by the protozoan parasite Trypanosoma cruzi and is a serious public health problem throughout Latin America. With 6 million people infected, there is a major international effort to develop new drugs. In the chronic phase of the disease, the parasite burden is extremely low, infections are highly focal at a tissue/organ level, and bloodstream parasites are only intermittently detectable. As a result, clinical trials are constrained by difficulties associated with determining parasitological cure. Even highly sensitive PCR methodologies can be unreliable, with a tendency to produce "false-cure" readouts. Improved diagnostic techniques and biomarkers for cure are therefore an important medical need.

METHODOLOGY/PRINCIPAL FINDINGS

Using an experimental mouse model, we have combined a multiplex assay system and highly sensitive bioluminescence imaging to evaluate serological procedures for diagnosis of T. cruzi infections and confirmation of parasitological cure. We identified a set of three antigens that in the context of the multiplex serology system, provide a rapid, reactive and highly accurate read-out of both acute and chronic T. cruzi infection. In addition, we describe specific antibody responses where down-regulation can be correlated with benznidazole-mediated parasite reduction and others where upregulation is associated with persistent infection. One specific antibody (IBAG39) highly correlated with the bioluminescence flux and represents a promising therapy monitoring biomarker in mice.

CONCLUSIONS/SIGNIFICANCE

Robust, high-throughput methodologies for monitoring the efficacy of anti-T. cruzi drug treatment are urgently required. Using our experimental systems, we have identified markers of infection or parasite reduction that merit assessing in a clinical setting for the longitudinal monitoring of drug-treated patients.

Need for a Standardized Translational Drug Development Platform: Lessons Learned from the Repurposing of Drugs for COVID-19

In the absence of drugs to treat or prevent COVID-19, drug repurposing can be a valuable strategy. Despite a substantial number of clinical trials, drug repurposing did not deliver on its promise. While success was observed with some repurposed drugs (e.g., remdesivir, dexamethasone, tocilizumab, baricitinib), others failed to show clinical efficacy. One reason is the lack of clear translational processes based on adequate preclinical profiling before clinical evaluation. Combined with limitations of existing in vitro and in vivo models, there is a need for a systematic approach to urgent antiviral drug development in the context of a global pandemic. We implemented a methodology to test repurposed and experimental drugs to generate robust preclinical evidence for further clinical development. This translational drug development platform comprises in vitro, ex vivo, and in vivo models of SARS-CoV-2, along with pharmacokinetic modeling and simulation approaches to evaluate exposure levels in plasma and target organs. Here, we provide examples of identified repurposed antiviral drugs tested within our multidisciplinary collaboration to highlight lessons learned in urgent antiviral drug development during the COVID-19 pandemic. Our data confirm the importance of assessing in vitro and in vivo potency in multiple assays to boost the translatability of pre-clinical data. The value of pharmacokinetic modeling and simulations for compound prioritization is also discussed. We advocate the need for a standardized translational drug development platform for mild-to-moderate COVID-19 to generate preclinical evidence in support of clinical trials. We propose clear prerequisites for progression of drug candidates for repurposing into clinical trials. Further research is needed to gain a deeper understanding of the scope and limitations of the presented translational drug development platform.

Pre-clinical evaluation of antiviral activity of nitazoxanide against SARS-CoV-2

Background

To address the emergence of SARS-CoV-2, multiple clinical trials in humans were rapidly started, including those involving an oral treatment by nitazoxanide, despite no or limited pre-clinical evidence of antiviral efficacy.

Methods

In this work, we present a complete pre-clinical evaluation of the antiviral activity of nitazoxanide against SARS-CoV-2.

Findings

First, we confirmed the in vitro efficacy of nitazoxanide and tizoxanide (its active metabolite) against SARS-CoV-2. Then, we demonstrated nitazoxanide activity in a reconstructed bronchial human airway epithelium model. In a SARS-CoV-2 virus challenge model in hamsters, oral and intranasal treatment with nitazoxanide failed to impair viral replication in commonly affected organs. We hypothesized that this could be due to insufficient diffusion of the drug into organs of interest. Indeed, our pharmacokinetic study confirmed that concentrations of tizoxanide in organs of interest were always below the in vitro EC₅₀.

Interpretation

These preclinical results suggest, if directly applicable to humans, that the standard formulation and dosage of nitazoxanide is not effective in providing antiviral therapy for Covid-19.

Funding

This work was supported by the Fondation de France “call FLASH COVID-19”, project TAMAC, by “Institut national de la santé et de la recherche médicale” through the REACTing (REsearch and ACTion targeting emerging infectious diseases), by REACTING/ANRS MIE under the agreement No. 21180 (‘Activité des molécules antivirales dans le modèle hamster’), by European Virus Archive Global (EVA 213 GLOBAL) funded by the European Union's Horizon 2020 research and innovation program under grant agreement No. 871029 and DNDi under support by the Wellcome Trust Grant ref: 222489/Z/21/Z through the COVID-19 Therapeutics Accelerator”.

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.

The oral protease inhibitor (PF-07321332) protects Syrian hamsters against infection with SARS-CoV-2 variants of concern

There is an urgent need for potent and selective antivirals against SARS-CoV-2. Pfizer developed PF-07321332 (PF-332), a potent inhibitor of the viral main protease (Mpro, 3CLpro) that can be dosed orally and that is in clinical development. We here report that PF-332 exerts equipotent in vitro activity against the four SARS-CoV-2 variants of concerns (VoC) and that it can completely arrest replication of the alpha variant in primary human airway epithelial cells grown at the air-liquid interface. Treatment of Syrian Golden hamsters with PF-332 (250 mg/kg, twice daily) completely protected the animals against intranasal infection with the beta (B.1.351) and delta (B.1.617.2) SARS-CoV-2 variants. Moreover, treatment of SARS-CoV-2 (B.1.617.2) infected animals with PF-332 completely prevented transmission to untreated co-housed sentinels.

There is an urgent need for anti-virals targeting SARS-CoV-2. One of the most promising viral targets is the main protease of SARS-CoV-2, which is essential for viral replication and has no human analogue. Here, Abdelnabi et al. show that one of the most promising anti-virals (PF-07321332), currently in clinical trials, protects against SARS-CoV-2 alpha, beta and delta variant infection and provide evidence of reduced transmission.

Serological reactivity against T. cruzi-derived antigens: Evaluation of their suitability for the assessment of response to treatment in chronic Chagas disease

Chagas disease, caused by the protozoan Trypanosoma cruzi, affects more than 6 million people worldwide. Following a mostly asymptomatic acute phase, the disease progresses to a long-lasting chronic phase throughout which life-threatening disorders to the heart and/or gastrointestinal tract will manifest in about 30% of those chronically infected. During the chronic phase, the parasitemia is low and intermittent, while a high level of anti-T. cruzi antibodies persist for years. These two features hamper post-chemotherapeutic follow-up of patients with the tools available. The lack of biomarkers for timely assessment of therapeutic response discourages a greater use of the two available anti-parasitic drugs, and complicates the evaluation of new drugs in clinical trials. Herein, we investigated in a blinded case-control study the serological reactivity over time of a group of parasite-derived antigens to potentially address follow up of T. cruzi chronically infected subjects after treatment. We tested PFR2, KMP11, HSP70, 3973, F29 and the InfYnity multiplexed antigenic array, by means of serological assays on a multi-national retrospective collection of samples. Some of the antigens exhibited promising results, underscoring the need for further studies to determine their potential role as treatment response biomarkers.

Identification of Resistance Determinants for a Promising Antileishmanial Oxaborole Series

Current treatment options for visceral leishmaniasis have several drawbacks, and clinicians are confronted with an increasing number of treatment failures. To overcome this, the Drugs for Neglected Diseases initiative (DNDi) has invested in the development of novel antileishmanial leads, including a very promising class of oxaboroles. The mode of action/resistance of this series to Leishmania is still unknown and may be important for its further development and implementation. Repeated in vivo drug exposure and an in vitro selection procedure on both extracellular promastigote and intracellular amastigote stages were both unable to select for resistance. The use of specific inhibitors for ABC-transporters could not demonstrate the putative involvement of efflux pumps. Selection experiments and inhibitor studies, therefore, suggest that resistance to oxaboroles may not emerge readily in the field. The selection of a genome-wide cosmid library coupled to next-generation sequencing (Cos-seq) was used to identify resistance determinants and putative targets. This resulted in the identification of a highly enriched cosmid, harboring genes of chromosome 2 that confer a subtly increased resistance to the oxaboroles tested. Moderately enriched cosmids encompassing a region of chromosome 34 contained the cleavage and polyadenylation specificity factor (cpsf) gene, encoding the molecular target of several related benzoxaboroles in other organisms.

Prediction of parasitological cure in children infected with Trypanosoma cruzi using a novel multiplex serological approach: an observational, retrospective cohort study

BACKGROUND

Assessment of therapeutic response with standard serological diagnostic assays in patients with chronic Chagas disease is a major challenge due to the long persistence of parasite-specific antibodies. The current consensus for parasitological cure is to monitor conversion from positive to negative Trypanosoma cruzi serology (seroreversion). However, because of robust humoral immune response, seroreversion by standard serological tests can take years to decades. Developing novel tests of parasitological cure or surrogates is thus a priority in the Chagas disease field. We aimed to evaluate the MultiCruzi assay as a predictive tool for parasitological cure in a cohort of treated infants and children with acute and chronic Chagas disease enrolled in a long-term retrospective longitudinal study with clinical, serological, and parasitological follow-up, and to explore whether MultiCruzi could predict parasitological cure more quickly than the current reference method.

METHODS

Patients from two retrospective paediatric Chagas disease cohort studies with clinical, serological, and parasitological follow-up, diagnosed and treated at the parasitology service, Hospital de Niños Ricardo Gutierrez (Buenos Aires, Argentina) were included in this retrospective cohort study. Serum samples were collected every 6 months to 12 months between Oct 22, 1990, and June 3, 2019, for cohort 1 and 1 month after birth for cohort 2 and then every 3 months for a year between July 23, 2012, and April 19, 2016. We evaluated serological follow-up with the Chagatest ELISA (Wiener Lab, Rosario, Argentina) and used this as a clinical reference method for the evaluation of seroreversion. We compared Chagatest ELISA results with results of MultiCruzi (InfYnity Biomarkers, Lyon, France), a novel antibody profiling multiplex assay, investigating seroreversion events with both of the assays and prediction of seroreversion with MultiCruzi using an interpretation formula.

FINDINGS

Combining experimental data from discrete analysis of 15 T cruzi antigens efficiently predicted seroreversion at an early stage, which was later confirmed by conventional T cruzi serology. In cohort 1 (n=69), which included children of three different age groups, we observed differences 2 years after therapy. In the 27 individuals from cohort 1 who were treated within the first 12 months of age, MultiCruzi predicted early seroreversion in 21 (78%) patients whereas nine (33%) patients showed seroreversion with Chagatest ELISA (seroreversion difference 0·44, 95% CI 0·26-0·63; p=0·0005). In the 12 patients from cohort 1 treated between 1 year and 2 years of age, MultiCruzi predicted early seroreversion in six (50%) patients, whereas only one (8%) patient was confirmed to be seronegative with Chagatest ELISA (seroreversion difference 0·42, 95% CI 0·14-0·70; p=0·0253). In the 30 patients from cohort 1 who were treated between 2 years and 19 years of age, MultiCruzi predicted early seroreversion in five (6%) patients, whereas no patients were found to be seronegative with Chagatest ELISA (seroreversion difference 0·17, 0·03-0·30; p=0·0253). In cohort 2 (n=27), which included only children younger than 1 year of age and had a shorter follow up (between 5 months and 32 months), the proportion of reported events was significantly different 180 days after treatment for the T cruzi-positive group (early seroreversion predicted in nine [90%] of ten patients with MultiCruzi and confirmed seroreversion in four [40%] of ten patients with Chagatest ELISA; seroreversion difference 0·50, 95% CI 0·19-0·81; p=0·0253) and for the T cruzi-negative group 90 days (early seroreversion predicted in five [29%] of 17 patients with MultiCruzi and confirmed seroreversion in one [6%] of 17 patients with Chagatest ELISA; seroreversion difference 0·24, 0·03-0·44; p=0·0455) and 180 days (early seroreversion predicted in 17 [100%] of 17 patients with MultiCruzi and confirmed seroreversion only in seven [41%] of 17 patients with Chagatest ELISA; seroreversion difference 0·59, 0·35-0·82; p=0·0016) after treatment.

INTERPRETATION

The MultiCruzi assay can be used as a predictive monitoring tool to assess parasitological cure in children. This approach might be a solution to forecast forthcoming seroreversion in treated adults infected with T cruzi, but this requires further investigation.

FUNDING

Drugs for Neglected Diseases initiative.

TRANSLATIONS

For the Spanish, Portuguese and French translations of the abstract see Supplementary Materials section.

Novel Linker Variants of Antileishmanial/Antitubercular 7-Substituted 2-Nitroimidazooxazines Offer Enhanced Solubility

Antitubercular 7-substituted 2-nitroimidazo[2,1-b][1,3]oxazines were previously shown to exhibit potent antileishmanial and antitrypanosomal activities, culminating in a new clinical investigational drug for visceral leishmaniasis (DNDI-0690). To offset development risks, we continued to seek further leads with divergent candidate profiles, especially analogues possessing greater aqueous solubility. Starting from an efficacious monoaryl derivative, replacement of the side chain ether linkage by novel amine, amide, and urea functionality was first explored; the former substitution was well-tolerated in vitro and in vivo but elicited marginal alterations to solubility (except through a less stable benzylamine), whereas the latter groups resulted in significant solubility improvements (up to 53-fold) but an antileishmanial potency reduction of at least 10-fold. Ultimately, we discovered that O-carbamate 66 offered a more optimal balance of increased solubility, suitable metabolic stability, excellent oral bioavailability (100%), and strong in vivo efficacy in a visceral leishmaniasis mouse model (97% parasite load reduction at 25 mg/kg).

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.

Colon sparing resection versus extended colectomy for left-sided obstructing colon cancer with caecal ischaemia or perforation: a nationwide study from the French Surgical Association

AIM

It is not known whether patients with obstructive left colon cancer (OLCC) with caecal ischaemia or diastatic perforation (defined as a blowout of the caecal wall related to colonic overdistension) should undergo a (sub)total colectomy (STC) or an ileo-caecal resection with double-barrelled ileo-colostomy. We aimed to compare the results of these two strategies.

METHOD

From 2000 to 2015, 1220 patients with OLCC underwent surgery by clinicians who were members of the French Surgical Association. Of these cases, 201 (16%) were found to have caecal ischaemia or diastatic perforation intra-operatively: 174 patients (87%) underwent a STC (extended colectomy group) and 27 (13%) an ileo-caecal resection with double-end stoma (colon-sparing group). Outcomes were compared retrospectively.

RESULTS

In the extended colectomy group, 95 patients (55%) had primary anastomosis and 79 (45%) had a STC with an end ileostomy. In the colon-sparing group, 10 patients (37%) had simultaneous resection of their primary tumour with segmental colectomy and an anastomosis which was protected by a double-barrelled ileo-colostomy. The demographic data for the two groups were comparable. Median operative time was longer in the STC group (P = 0.0044). There was a decrease in postoperative mortality (7% vs 12%, P = 0.75) and overall morbidity (56% vs 67%, P = 0.37) including surgical (30% vs 40%, P = 0.29) and severe complications (17% vs 27%, P = 0.29) in the colon-sparing group, although these differences did not reach statistical significance. Cumulative morbidity included all surgical stages and the rate of permanent stoma was 66% and 37%, respectively, with no significant difference between the two groups. Overall survival and disease-free survival were similar between the two groups.

CONCLUSION

The colon-sparing strategy may represent a valid and safe alternative to STC in OLCC patients with caecal ischaemia or diastatic perforation.

Re-evaluating pretomanid analogues for Chagas disease: Hit-to-lead studies reveal both in vitro and in vivo trypanocidal efficacy

Phenotypic screening of a 900 compound library of antitubercular nitroimidazole derivatives related to pretomanid against the protozoan parasite Trypanosoma cruzi (the causative agent for Chagas disease) identified several structurally diverse hits with an unknown mode of action. Following initial profiling, a first proof-of-concept in vivo study was undertaken, in which once daily oral dosing of a 7-substituted 2-nitroimidazooxazine analogue suppressed blood parasitemia to low or undetectable levels, although sterile cure was not achieved. Limited hit expansion studies alongside counter-screening of new compounds targeted at visceral leishmaniasis laid the foundation for a more in-depth assessment of the best leads, focusing on both drug-like attributes (solubility, metabolic stability and safety) and maximal killing of the parasite in a shorter timeframe. Comparative appraisal of one preferred lead (58) in a chronic infection mouse model, monitored by highly sensitive bioluminescence imaging, provided the first definitive evidence of (partial) curative efficacy with this promising nitroimidazooxazine class.

Animal models of Chagas disease and their translational value to drug development

INTRODUCTION

American trypanosomiasis, better known as Chagas disease, is a global public health issue. Current treatments targeting the causative parasite, Trypanosoma cruzi, are limited to two old nitroheterocyclic compounds; new, safer drugs are needed. New tools to identify compounds suitable for parasitological cure in humans have emerged through efforts in drug discovery.

AREAS COVERED

Animal disease models are an integral part of the drug discovery process. There are numerous experimental models of Chagas disease described and in use; rather than going through each of these and their specific features, the authors focus on developments in recent years, in particular the imaging technologies that have dramatically changed the Chagas R&D landscape, and provide a critical view on their value and limitations for moving compounds forward into further development.

EXPERT OPINION

The application of new technological advances to the field of drug development for Chagas disease has led to the implementation of new and robust/standardized in vivo models that contributed to a better understanding of host/parasite interactions. These new models should also build confidence in their translational value for moving compounds forward into clinical development.

Novel structural CYP51 mutation in Trypanosoma cruzi associated with multidrug resistance to CYP51 inhibitors and reduced infectivity

Ergosterol biosynthesis inhibitors, such as posaconazole and ravuconazole, have been proposed as drug candidates for Chagas disease, a neglected infectious tropical disease caused by the protozoan parasite Trypanosoma cruzi. To understand better the mechanism of action and resistance to these inhibitors, a clone of the T. cruzi Y strain was cultured under intermittent and increasing concentrations of ravuconazole until phenotypic stability was achieved. The ravuconazole-selected clone exhibited loss in fitness in vitro when compared to the wild-type parental clone, as observed in reduced invasion capacity and slowed population growth in both mammalian and insect stages of the parasite. In drug activity assays, the resistant clone was above 300-fold more tolerant to ravuconazole than the sensitive parental clone, when the half-maximum effective concentration (EC₅₀) was considered. The resistant clones also showed reduced virulence in vivo, when compared to parental sensitive clones. Cross-resistance to posaconazole and other CYP51 inhibitors, but not to other antichagasic drugs that act independently of CYP51, such as benznidazole and nifurtimox, was also observed. A novel amino acid residue change, T297M, was found in the TcCYP51 gene in the resistant but not in the sensitive clones. The structural effects of the T297M, and of the previously described P355S residue changes, were modelled to understand their impact on interaction with CYP51 inhibitors.

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A ravuconazole-resistant T. cruzi clone presented reduced in vitro and in vivo fitness.

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The ravuconazole-resistant clone presented cross-resistance to other CYP51 inhibitors.

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There was no cross-resistance to benznidazole and nifurtimox.

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Resistance is associated with a novel structural mutation in the TcCYP51 protein.

Do systemic treatments delivered after Nivolumab result in better outcomes? A bicentric case-control study

BACKGROUND

Immune checkpoint inhibitors (ICI) are now widely used at different stages of non-small cell lung cancers (NSCLC). Some clinical studies suggest that chemotherapy and immunotherapy have synergic activities, raising the question of the best therapeutic sequence. We studied the effect of chemotherapy in advanced NSCLC when administered after immunotherapy by nivolumab.

METHODS

We performed a bicentric, retrospective, case-control study in two French hospitals. Patients with NSCLC treated with chemotherapy after nivolumab between January 2015 and January 2016 were included. Each case was matched on age and number of previous lines to one lung cancer patient who had not received nivolumab. Each CT-scanner has been reviewed and the objective response to chemotherapy was assessed for each patient according to the RECIST 1.1 criteria.

RESULTS

Thirty-one patients with advanced NSCL who had at least received one cycle of chemotherapy after progression under nivolumab in the inclusion period were matched to 31 controls. The median age for cases was 59 yo and the predominant tumoral histology was adenocarcinoma (77%). The progression free survival (PFS) was 2.95 months in the studied group vs 2.69 months (P=0.18) in the control group. At best response, disease control (DC=partial response and stable disease) was better in the case group than in the control group (58% vs 39%, P=0.127). Cases were about five times more likely to get objective response to best evaluation than controls (OR=5.043 [95% CI: 0.975-26.086]; P=0.054). The overall survival (OS) was 7.3 months in the case group and 3.3 months in the control group (P=0.074). Patients who have been treated with targeted therapy instead of chemotherapy and patients with squamous lung cancer had worst PFS and OS.

CONCLUSION

In advanced NSCLC, the chemotherapy progression free survival does not seem higher when administered after nivolumab. However, when administered post-nivolumab, traditional chemotherapy has 5 times more chances to achieve objective response and seems to improve overall survival of cases. Pooled analysis with other similar studies might be interesting for a next step.

A Multi-Species Phenotypic Screening Assay for Leishmaniasis Drug Discovery Shows That Active Compounds Display a High Degree of Species-Specificity

High genetic and phenotypic variability between Leishmania species and strains within species make the development of broad-spectrum antileishmanial drugs challenging. Thus, screening panels consisting of several diverse Leishmania species can be useful in enabling compound prioritization based on their spectrum of activity. In this study, a robust and reproducible high content assay was developed, and 1280 small molecules were simultaneously screened against clinically relevant cutaneous and visceral species: L. amazonensis, L. braziliensis, and L. donovani. The assay is based on THP-1 macrophages infected with stationary phase promastigotes and posterior evaluation of both compound antileishmanial activity and host cell toxicity. The profile of compound activity was species-specific, and out of 51 active compounds, only 14 presented broad-spectrum activity against the three species, with activities ranging from 52% to 100%. Notably, the compounds CB1954, Clomipramine, Maprotiline, Protriptyline, and ML-9 presented pan-leishmanial activity, with efficacy greater than 70%. The results highlight the reduced number of compound classes with pan-leishmanial activity that might be available from diversity libraries, emphasizing the need to screen active compounds against a panel of species and strains. The assay reported here can be adapted to virtually any Leishmania species without the need for genetic modification of parasites, providing the basis for the discovery of broad spectrum anti-leishmanial agents.

The unmet medical need for Trypanosoma cruzi-infected patients: Monitoring the disease status

Patients infected by Trypanosoma cruzi are typically diagnosed by detecting specific antibodies in serological assays. Persistence of the parasitic infection increases the risk of morbidity and mortality. There are indications that anti-parasitic therapies help to reduce these risks when comparing treated and untreated populations. However, at present, treatment efficacy cannot be properly evaluated on an individual patient basis by available laboratory methods. To monitor parasite clearance, it is essential to change the paradigm of serological methods: analyzing the broad spectrum of antibody diversity is more informative about clinical status than conventional serology tests designed merely for global detection of antibodies.

Metabolomics, lipidomics and proteomics profiling of myoblasts infected with Trypanosoma cruzi after treatment with different drugs against Chagas disease

INTRODUCTION

Chagas disease, the most important parasitic infection in Latin America, is caused by the intracellular protozoan Trypanosoma cruzi. To treat this disease, only two nitroheterocyclic compounds with toxic side effects exist and frequent treatment failures are reported. Hence there is an urgent need to develop new drugs. Recently, metabolomics has become an efficient and cost-effective strategy for dissecting drug mode of action, which has been applied to bacteria as well as parasites, such as different Trypanosome species and forms.

OBJECTIVES

We assessed if the metabolomics approach can be applied to study drug action of the intracellular amastigote form of T. cruzi in a parasite-host cell system.

METHODS

We applied a metabolic fingerprinting approach (DI-MS and NMR) to evaluate metabolic changes induced by six different (candidate) drugs in a parasite-host cell system. In a second part of our study, we analyzed the impact of two drugs on polar metabolites, lipid and proteins to evaluate if affected pathways can be identified.

RESULTS

Metabolic signatures, obtained by the fingerprinting approach, resulted in three different clusters. Two can be explained by already known of mode actions, whereas the three experimental drugs formed a separate cluster. Significant changes induced by drug action were observed in all the three metabolic fractions (polar metabolites, lipids and proteins). We identified a general impact on the TCA cycle, but no specific pathways could be attributed to drug action, which might be caused by a high percentage of common metabolome between a eukaryotic host cell and a eukaryotic parasite. Additionally, ion suppression effects due to differences in abundance between host cells and parasites may have occurred.

CONCLUSION

We validated the metabolic fingerprinting approach to a complex host-cell parasite system. This technique can potentially be applied in the early stage of drug discovery and could help to prioritize early leads or reconfirmed hits for further development.

Thirty-day mortality after emergency surgery for obstructing colon cancer: survey and dedicated score from the French Surgical Association

AIM

The aim was to define risk factors for postoperative mortality in patients undergoing emergency surgery for obstructing colon cancer (OCC) and to propose a dedicated score.

METHOD

From 2000 to 2015, 2325 patients were treated for OCC in French surgical centres by members of the French National Surgical Association. A multivariate analysis was performed for variables with P value ≤ 0.20 in the univariate analysis for 30-day mortality. Predictive performance was assessed by the area under the receiver operating characteristic curve.

RESULTS

A total of 1983 patients were included. Thirty-day postoperative mortality was 7%. Multivariate analysis found five significant independent risk factors: age ≥ 75 (P = 0.013), American Society of Anesthesiologists (ASA) score ≥ III (P = 0.027), pulmonary comorbidity (P = 0.0002), right-sided cancer (P = 0.047) and haemodynamic failure (P < 0.0001). The odds ratio for risk of postoperative death was 3.42 with one factor, 5.80 with two factors, 15.73 with three factors, 29.23 with four factors and 77.25 with five factors. The discriminating capacity in predicting 30-day postoperative mortality was 0.80.

CONCLUSION

Thirty-day postoperative mortality after emergency surgery for OCC is correlated with age, ASA score, pulmonary comorbidity, site of tumour and haemodynamic failure, with a specific score ranging from 0 to 5.

Drug Discovery for Chagas Disease: Impact of Different Host Cell Lines on Assay Performance and Hit Compound Selection

Cell-based screening has become the major compound interrogation strategy in Chagas disease drug discovery. Several different cell lines have been deployed as host cells in screening assays. However, host cell characteristics and host-parasite interactions may play an important role when assessing anti-T. cruzi compound activity, ultimately impacting on hit discovery. To verify this hypothesis, four distinct mammalian cell lines (U2OS, THP-1, Vero and L6) were used as T. cruzi host cells in High Content Screening assays. Rates of infection varied greatly between different host cells. Susceptibility to benznidazole also varied, depending on the host cell and parasite strain. A library of 1,280 compounds was screened against the four different cell lines infected with T. cruzi, resulting in the selection of a total of 82 distinct compounds as hits. From these, only two hits were common to all four cell lines assays (2.4%) and 51 were exclusively selected from a single assay (62.2%). Infected U2OS cells were the most sensitive assay, as 55 compounds in total were identified as hits; infected THP-1 yielded the lowest hit rates, with only 16 hit compounds. Of the selected hits, compound FPL64176 presented selective anti-T. cruzi activity and could serve as a starting point for the discovery of new anti-chagasic drugs.

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

Patient: Male, 69

Final Diagnosis: Spontaneous regression of a Lymph node metastasis

Symptoms: Hypereosinophilia • inguinal mass

Medication: —

Clinical Procedure: —

Specialty: Oncology

Validation of Apolipoprotein A-1 and Fibronectin Fragments as Markers of Parasitological Cure for Congenital Chagas Disease in Children Treated With Benznidazole

Background

No reliable tests or validated biomarkers exist to ensure parasitological cure following treatment of Chagas disease (CD) patients chronically infected with Trypanosoma cruzi. As seroreversion, the only marker of cure, happens more quickly in children, we investigated the correlation between previously identified biomarkers and seroreversion in children.

Methods

Thirty CD children (age 1 month to 10 years) diagnosed as T. cruzi positive (time point S0) were treated with benznidazole (BZ) 5–8 mg/kg/d for 60 days. At least 2 serological tests were used to evaluate treatment efficacy from the end of treatment (S1) until seroreversion (S2). Thirty children (age 1 month to 10 years) and 15 adults were used as healthy controls (HCs). Immunoblot and a proteomic-based assay were used to validate previously identified fragments of apolipoprotein A-1 (ApoA1) and fibronectin (FBN) as CD biomarkers.

Results

Correlation between seroreversion and absence of ApoA1 and FBN fragments by immunoblot was observed in 30/30 (100%) and 29/30 (96.6%) CD children, respectively. ApoA1 and FBN fragments were absent at the end of BZ treatment in 20/30 (66.6%) and 16/30 (53.3%) children, respectively. Absence of fragments in serum profiles was confirmed by mass spectrometry. Using intact protein analysis, a 28 109-Da protein identified as full-length ApoA1 by tandem mass spectrometry was detected in HC serum samples.

Conclusions

These data confirm that ApoA1 and FBN fragments can discriminate between healthy and T. cruzi–infected samples. Correlation with seroreversion was shown for the first time; results suggest predictive capacity potentially superior to serology, making them potentially useful as surrogate biomarkers.

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.

Development of (6 R)-2-Nitro-6-[4-(trifluoromethoxy)phenoxy]-6,7-dihydro-5 H-imidazo[2,1- b][1,3]oxazine (DNDI-8219): A New Lead for Visceral Leishmaniasis

Discovery of the potent antileishmanial effects of antitubercular 6-nitro-2,3-dihydroimidazo[2,1-b][1,3]oxazoles and 7-substituted 2-nitro-5,6-dihydroimidazo[2,1-b][1,3]oxazines stimulated the examination of further scaffolds (e.g., 2-nitro-5,6,7,8-tetrahydroimidazo[2,1-b][1,3]oxazepines), but the results for these seemed less attractive. Following the screening of a 900-compound pretomanid analogue library, several hits with more suitable potency, solubility, and microsomal stability were identified, and the superior efficacy of newly synthesized 6R enantiomers with phenylpyridine-based side chains was established through head-to-head assessments in a Leishmania donovani mouse model. Two such leads (R-84 and R-89) displayed promising activity in the more stringent Leishmania infantum hamster model but were unexpectedly found to be potent inhibitors of hERG. An extensive structure–activity relationship investigation pinpointed two compounds (R-6 and pyridine R-136) with better solubility and pharmacokinetic properties that also provided excellent oral efficacy in the same hamster model (>97% parasite clearance at 25 mg/kg, twice daily) and exhibited minimal hERG inhibition. Additional profiling earmarked R-6 as the favored backup development candidate.

In vitro and in vivo pharmacodynamics of three novel antileishmanial lead series

Objectives

Three new chemical series (bicyclic nitroimidazoles, aminopyrazoles and oxaboroles) were selected by Drugs for Neglected Diseases initiative as potential new drug leads for leishmaniasis. Pharmacodynamics studies included both in vitro and in vivo efficacy, cross-resistance profiling against the current antileishmanial reference drugs and evaluation of their cidal activity potential.

Methods

Efficacy against the reference laboratory strains of Leishmania infantum (MHOM/MA(BE)/67/ITMAP263) and L. donovani (MHOM/ET/67/L82) was evaluated in vitro on intracellular amastigotes and in vivo in the early curative hamster model. Cidal activity was assessed over a period of 15 days in an in vitro ‘time-to-kill’ assay. Cross-resistance was assessed in vitro on a panel of L. infantum strains with different degrees of resistance to either antimony, miltefosine or paromomycin.

Results

All lead compounds showed potent and selective in vitro activity against the Leishmania strains tested and no cross-resistance could be demonstrated against any of the current antileishmanial drugs. Cidal activity was obtained in vitro for all series within 15 days of exposure with some differences noted between L. donovani and L. infantum. When evaluated in vivo, all lead compounds showed high efficacy and no adverse effects were observed.

Conclusions

The new lead series were shown to have cidal pharmacodynamic activity. The absence of cross-resistance with any of the current antileishmanial drugs opens possibilities for combination treatment to reduce the likelihood of treatment failures and drug resistance.

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Good efficacy was evaluated for all series in vitro and in vivo.

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No cross-resistance towards current anti-leishmanial drugs was observed.

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Cidal activity was obtained in vitro for all series within 15 days of exposure.

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Some differences were observed between L. infantum and L. donovani.

Phenotypic screening approaches for Chagas disease drug discovery

INTRODUCTION

Chagas disease, caused by the parasite Trypanosoma cruzi, is a global public health issue. Current treatments targeting the parasite are limited to two old nitroheterocyclic drugs with serious side effects. The need for new and safer drugs has prompted numerous drug discovery efforts to identify compounds suitable for parasitological cure in the last decade. Areas covered: Target-based drug discovery has been limited by the small number of well-validated targets - the latest example being the failure of azoles, T. cruzi CYP51 inhibitors, in proof-of-concept clinical trials; instead phenotypic-based drug discovery has become the main pillar of Chagas R&D. Rather than focusing on the technical features of these screening assays, the authors describe the different assays developed and available in the field, and provide a critical view on their values and limitations in the screening cascade for Chagas drug development. Expert opinion: The application of technological advances to the field of Chagas disease has led to a variety of phenotypic assays that have not only changed the disease discovery landscape but have also helped us to gain a better understanding of parasite/host interactions. Recent examples of target resolution from phenotypic hits will uncover new opportunities for drug discovery for Chagas disease.

Assessment of a pretomanid analogue library for African trypanosomiasis: Hit-to-lead studies on 6-substituted 2-nitro-6,7-dihydro-5H-imidazo[2,1-b][1,3]thiazine 8-oxides

A 900 compound nitroimidazole-based library derived from our pretomanid backup program with TB Alliance was screened for utility against human African trypanosomiasis (HAT) by the Drugs for Neglected Diseases initiative. Potent hits included 2-nitro-6,7-dihydro-5H-imidazo[2,1-b][1,3]thiazine 8-oxides, which surprisingly displayed good metabolic stability and excellent cell permeability. Following comprehensive mouse pharmacokinetic assessments on four hits and determination of the most active chiral form, a thiazine oxide counterpart of pretomanid (24) was identified as the best lead. With once daily oral dosing, this compound delivered complete cures in an acute infection mouse model of HAT and increased survival times in a stage 2 model, implying the need for more prolonged CNS exposure. In preliminary SAR findings, antitrypanosomal activity was reduced by removal of the benzylic methylene but enhanced through a phenylpyridine-based side chain, providing important direction for future studies.

7-Substituted 2-Nitro-5,6-dihydroimidazo[2,1-b][1,3]oxazines: Novel Antitubercular Agents Lead to a New Preclinical Candidate for Visceral Leishmaniasis

Within a backup program for the clinical investigational agent pretomanid (PA-824), scaffold hopping from delamanid inspired the discovery of a novel class of potent antitubercular agents that unexpectedly possessed notable utility against the kinetoplastid disease visceral leishmaniasis (VL). Following the identification of delamanid analogue DNDI-VL-2098 as a VL preclinical candidate, this structurally related 7-substituted 2-nitro-5,6-dihydroimidazo[2,1-b][1,3]oxazine class was further explored, seeking efficacious backup compounds with improved solubility and safety. Commencing with a biphenyl lead, bioisosteres formed by replacing one phenyl by pyridine or pyrimidine showed improved solubility and potency, whereas more hydrophilic side chains reduced VL activity. In a Leishmania donovani mouse model, two racemic phenylpyridines (71 and 93) were superior, with the former providing >99% inhibition at 12.5 mg/kg (b.i.d., orally) in the Leishmania infantum hamster model. Overall, the 7R enantiomer of 71 (79) displayed more optimal efficacy, pharmacokinetics, and safety, leading to its selection as the preferred development candidate.

Chagas disease research and development: Is there light at the end of the tunnel?

Chagas disease, or American trypanosomiasis, is the result of infection by the parasite Trypanosoma cruzi. It is endemic in Latin America, and spreading around the globe due to human migration. Although it was first identified more than a century ago, only two old drugs are available for treatment and a lot of questions related to the disease progression, its pathologies, and not to mention the assessment of treatment efficacy, are subject to debate and remain to be answered. Indeed, the current status of evidence and data available does not allow any absolute statement related to treatment needs and outcome for Chagas patients to be made. Although there has been some new impetus in Research and Development for Chagas disease following recent new clinical trials, there is a scientific requirement to review and challenge the current status of evidence and define basic and clinical research priorities and next steps in the field. This should ensure that the best drugs for Chagas disease are developed, but will require a focused and collaborative effort of the entire Chagas disease research community.

Nitroheterocyclic drugs cure experimental Trypanosoma cruzi infections more effectively in the chronic stage than in the acute stage

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.

Synthesis and evaluation of analogs of the phenylpyridazinone NPD-001 as potent trypanosomal TbrPDEB1 phosphodiesterase inhibitors and in vitro trypanocidals

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. Knock down of both enzymes leads to cell cycle arrest and is lethal to the parasite. Recently, we reported the phenylpyridazinone, NPD-001, with low nanomolar IC50 values on both TbrPDEB1 (IC50: 4nM) and TbrPDEB2 (IC50: 3nM) (J. Infect. Dis.2012, 206, 229). In this study, we now report on the first structure activity relationships of a series of phenylpyridazinone analogs as TbrPDEB1 inhibitors. A selection of compounds was also shown to be anti-parasitic. Importantly, a good correlation between TbrPDEB1 IC50 and EC50 against the whole parasite was observed. Preliminary analysis of the SAR of selected compounds on TbrPDEB1 and human PDEs shows large differences which shows the potential for obtaining parasite selective PDE inhibitors. The results of these studies support the pharmacological validation of the Trypanosome PDEB family as novel therapeutic approach for HAT and provide as well valuable information for the design of potent TbrPDEB1 inhibitors that could be used for the treatment of this disease.

Translational challenges of animal models in Chagas disease drug development: a review

Chagas disease, or American trypanosomiasis, caused by Trypanosoma cruzi parasite infection is endemic in Latin America and presents an increasing clinical challenge due to migrating populations. Despite being first identified over a century ago, only two drugs are available for its treatment, and recent outcomes from the first clinical trials in 40 years were lackluster. There is a critical need to develop new drugs to treat Chagas disease. This requires a better understanding of the progression of parasite infection, and standardization of animal models designed for Chagas disease drug discovery. Such measures would improve comparison of generated data and the predictability of test hypotheses and models designed for translation to human disease. Existing animal models address both disease pathology and treatment efficacy. Available models have limited predictive value for the preclinical evaluation of novel therapies and need to more confidently predict the efficacy of new drug candidates in clinical trials. This review highlights the overall lack of standardized methodology and assessment tools, which has hampered the development of efficacious compounds to treat Chagas disease. We provide an overview of animal models for Chagas disease, and propose steps that could be undertaken to reduce variability and improve predictability of drug candidate efficacy. New technological developments and tools may contribute to a much needed boost in the drug discovery process.

Novel 3-nitrotriazole-based amides and carbinols as bifunctional antichagasic agents

3-Nitro-1H-1,2,4-triazole-based amides with a linear, rigid core and 3-nitrotriazole-based fluconazole analogues were synthesized as dual functioning antitrypanosomal agents. Such compounds are excellent substrates for type I nitroreductase (NTR) located in the mitochondrion of trypanosomatids and, at the same time, act as inhibitors of the sterol 14α-demethylase (T. cruzi CYP51) enzyme. Because combination treatments against parasites are often superior to monotherapy, we believe that this emerging class of bifunctional compounds may introduce a new generation of antitrypanosomal drugs. In the present work, the synthesis and in vitro and in vivo evaluation of such compounds is discussed.

Chagas Disease Drug Discovery

American trypanosomiasis, or Chagas disease, is the result of infection by the Trypanosoma cruzi parasite. Endemic in Latin America where it is the major cause of death from cardiomyopathy, the impact of the disease is reaching global proportions through migrating populations. New drugs that are safe, efficacious, low cost, and adapted to the field are critically needed. Over the past five years, there has been increased interest in the disease and a surge in activities within various organizations. However, recent clinical trials with azoles, specifically posaconazole and the ravuconazole prodrug E1224, were disappointing, with treatment failure in Chagas patients reaching 70% to 90%, as opposed to 6% to 30% failure for benznidazole-treated patients. The lack of translation from in vitro and in vivo models to the clinic observed for the azoles raises several questions. There is a scientific requirement to review and challenge whether we are indeed using the right tools and decision-making processes to progress compounds forward for the treatment of this disease. New developments in the Chagas field, including new technologies and tools now available, will be discussed, and a redesign of the current screening strategy during the discovery process is proposed.

Serum biomarkers predictive of cure in Chagas disease patients after nifurtimox treatment

BACKGROUND

Chagas disease (CD), caused by the protozoan Trypanosoma cruzi, remains an important public health issue in many Central and South American countries, as well as non-endemic areas with high rates of immigration from these countries. Existing treatment options for CD are limited and often unsatisfactory. Moreover the lack of post-treatment tests of cure limits the development of new drugs. To address this issue, we sought to identify serum biomarkers following nifurtimox (Nfx) treatment that could be used as an early test of cure and/or markers of a therapeutic response.

METHODS

Human sera from Chagas patients pre- and post-treatment with Nfx (n = 37) were compared to samples from healthy subjects (n = 37) using a range of proteomic and immunologic techniques. Biomarker peaks with the best discriminatory power were further characterized.

RESULTS

Using serum samples (n = 111), we validated the presence of five key biomarkers identified in our previous study, namely human apolipoprotein A-I (APOA1) and specific fragments thereof and one fragment of human fibronectin (FN1). In chagasic serum samples all biomarkers except full-length APOA1 were upregulated. These five biomarkers returned to normal in 43% (16/37) of the patients treated with Nfx at three years after treatment.

CONCLUSIONS

The normalization of biomarker patterns strongly associated with CD suggests that these markers can be used to identify patients in whom Nfx treatment is successful. We believe that these are the first biomarkers predictive of cure in CD patients.

Two analogues of fenarimol show curative activity in an experimental model of Chagas disease

Chagas disease, caused by the protozoan parasite Trypanosoma cruzi (T. cruzi), is an increasing threat to global health. Available medicines were introduced over 40 years ago, have undesirable side effects, and give equivocal results of cure in the chronic stage of the disease. We report the development of two compounds, 6 and (S)-7, with PCR-confirmed curative activity in a mouse model of established T. cruzi infection after once daily oral dosing for 20 days at 20 mg/kg 6 and 10 mg/kg (S)-7. Compounds 6 and (S)-7 have potent in vitro activity, are noncytotoxic, show no adverse effects in vivo following repeat dosing, are prepared by a short synthetic route, and have druglike properties suitable for preclinical development.

Complexes of Trypanosoma cruzi sterol 14α-demethylase (CYP51) with two pyridine-based drug candidates for Chagas disease: structural basis for pathogen selectivity

Chagas disease, caused by the eukaryotic (protozoan) parasite Trypanosoma cruzi, is an alarming emerging global health problem with no clinical drugs available to treat the chronic stage. Azole inhibitors of sterol 14α-demethylase (CYP51) were proven effective against Chagas, and antifungal drugs posaconazole and ravuconazole have entered clinical trials in Spain, Bolivia, and Argentina. Here we present the x-ray structures of T. cruzi CYP51 in complexes with two alternative drug candidates, pyridine derivatives (S)-(4-chlorophenyl)-1-(4-(4-(trifluoromethyl)phenyl)-piperazin-1-yl)-2-(pyridin-3-yl)ethanone (UDO; Protein Data Bank code 3ZG2) and N-[4-(trifluoromethyl)phenyl]-N-[1-[5-(trifluoromethyl)-2-pyridyl]-4-piperi-dyl]pyridin-3-amine (UDD; Protein Data Bank code 3ZG3). These compounds have been developed by the Drugs for Neglected Diseases initiative (DNDi) and are highly promising antichagasic agents in both cellular and in vivo experiments. The binding parameters and inhibitory effects on sterol 14α-demethylase activity in reconstituted enzyme reactions confirmed UDO and UDD as potent and selective T. cruzi CYP51 inhibitors. Comparative analysis of the pyridine- and azole-bound CYP51 structures uncovered the features that make UDO and UDD T. cruzi CYP51-specific. The structures suggest that although a precise fit between the shape of the inhibitor molecules and T. cruzi CYP51 active site topology underlies their high inhibitory potency, a longer coordination bond between the catalytic heme iron and the pyridine nitrogen implies a weaker influence of pyridines on the iron reduction potential, which may be the basis for the observed selectivity of these compounds toward the target enzyme versus other cytochrome P450s, including human drug-metabolizing P450s. These findings may pave the way for the development of novel CYP51-targeted drugs with optimized metabolic properties that are very much needed for the treatment of human infections caused by eukaryotic microbial pathogens.