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.

Discovery of a highly potent, selective, orally bioavailable inhibitor of KAT6A/B histone acetyltransferases with efficacy against KAT6A-high ER+ breast cancer

KAT6A, and its paralog KAT6B, are histone lysine acetyltransferases (HAT) that acetylate histone H3K23 and exert an oncogenic role in several tumor types including breast cancer where KAT6A is frequently amplified/overexpressed. However, pharmacologic targeting of KAT6A to achieve therapeutic benefit has been a challenge. Here we describe identification of a highly potent, selective, and orally bioavailable KAT6A/KAT6B inhibitor CTx-648 (PF-9363), derived from a benzisoxazole series, which demonstrates anti-tumor activity in correlation with H3K23Ac inhibition in KAT6A over-expressing breast cancer. Transcriptional and epigenetic profiling studies show reduced RNA Pol II binding and downregulation of genes involved in estrogen signaling, cell cycle, Myc and stem cell pathways associated with CTx-648 anti-tumor activity in ER-positive (ER+) breast cancer. CTx-648 treatment leads to potent tumor growth inhibition in ER+ breast cancer in vivo models, including models refractory to endocrine therapy, highlighting the potential for targeting KAT6A in ER+ breast cancer.

Discovery and Structure-Activity Relationships of Quinazolinone-2-carboxamide Derivatives as Novel Orally Efficacious Antimalarials

A phenotypic high-throughput screen allowed discovery of quinazolinone-2-carboxamide derivatives as a novel antimalarial scaffold. Structure-activity relationship studies led to identification of a potent inhibitor 19f, 95-fold more potent than the original hit compound, active against laboratory-resistant strains of malaria. Profiling of 19f suggested a fast in vitro killing profile. In vivo activity in a murine model of human malaria in a dose-dependent manner constitutes a concomitant benefit.

Abstract 1130: First-in-class KAT6A/KAT6B inhibitor CTx-648 (PF-9363) demonstrates potent anti-tumor activity in ER+ breast cancer with KAT6A dysregulation

KAT6A is a lysine histone acetyltransferase (HAT) of the MYST family of HATs. KAT6A, and its paralog KAT6B, have been shown to acetylate histone H3K23Ac and regulate diverse biological processes, including transcription, cell-cycle progression, stem cell maintenance and development. Molecular dysregulation of KAT6A has been observed in several cancers, including amplifications in breast, lung, ovarian cancer along with oncogenic fusions in AML. In breast cancer, KAT6A is amplified as part of the 8p11 amplicon in 10-15% of the patient population, which correlates with a worse clinical outcome in the estrogen receptor+ (ER+) subtype. Here we present identification of a first-in-class potent KAT6A/KAT6B tool inhibitor CTx-648 (PF-9363), that possesses high selectivity versus other MYST family members (KAT7, KAT5, KAT8) and other KATs, demonstrating anti-tumor activity in breast cancer. Using genetic and pharmacological approaches, we have demonstrated several ER+ breast cancer cell lines including KAT6A amplified and over-expressing models, are dependent on KAT6A enzymatic function. Epigenomic profiling studies using bulk and nascent RNA-seq combined with ATAC-seq revealed CTx-648 leads to downregulation of a specific set of genes involved in ESR1 pathway, cell cycle and stem cell pathways. In vivo target validation studies showed strong anti-tumor activity of CTx-648 in several ER+ breast cancer cell line and patient-derived xenograft models, including models harboring endocrine therapy resistance ESR1 mutations, highlighting promise for this novel therapy in ER+ breast cancer population. Based on the strength of the pre-clinical data, a selective KAT6 inhibitor (PF-07248144) is now commencing a Phase 1 clinical study in Advanced or Metastatic Solid Tumors.

Citation Format: Shikhar Sharma, Jay Chung, Sean Uryu, Amanda Rickard, Natalie Nady, Showkhin Khan, Zhenxiong Wang, Yong Zhang, Haikuo Zhang, Pei-Pei Kung, Eric Greenwald, Karen Maegley, Patrick Bingham, Hieu Lam, Ylva E. Bozikis, Hendrik Falk, Elizabeth Allan, Vicky M. Avery, Miriam S. Butler, Michelle A. Camerino, Catalina Carrasco-Pozo, Susan A. Charman, Melissa J. Davis, Mark A. Dawson, Dawson Sarah-Jane, Melanie de Silva, Matthew L. Dennis, Olan Dolezal, Rachel Lagiakos, Geoffrey J. Lindeman, Laura MacPherson, Stewart Nuttall, Thomas S. Peat, Bin Ren, Alexandra E. Stupple, Elliot Surgenor, Chin Wee Tan, Tim Thomas, Jane E. Visvader, Anne K. Voss, Francois Vaillant, Karen L. White, James Whittle, Yuqing Yang, Soroor Hediyeh-Zadeh, Paul A. Stupple, Ian P. Street, Brendon J. Monahan, Thomas Paul. First-in-class KAT6A/KAT6B inhibitor CTx-648 (PF-9363) demonstrates potent anti-tumor activity in ER+ breast cancer with KAT6A dysregulation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1130.

Repositioning and Characterization of 1-(Pyridin-4-yl)pyrrolidin-2-one Derivatives as Plasmodium Cytoplasmic Prolyl-tRNA Synthetase Inhibitors

Prolyl-tRNA synthetase (PRS) is a clinically validated antimalarial target. Screening of a set of PRS ATP-site binders, initially designed for human indications, led to identification of 1-(pyridin-4-yl)pyrrolidin-2-one derivatives representing a novel antimalarial scaffold. Evidence designates cytoplasmic PRS as the drug target. The frontrunner 1 and its active enantiomer 1-S exhibited low-double-digit nanomolar activity against resistant Plasmodium falciparum (Pf) laboratory strains and development of liver schizonts. No cross-resistance with strains resistant to other known antimalarials was noted. In addition, a similar level of growth inhibition was observed against clinical field isolates of Pf and P. vivax. The slow killing profile and the relative high propensity to develop resistance in vitro (minimum inoculum resistance of 8 × 10⁵ parasites at a selection pressure of 3 × IC₅₀) constitute unfavorable features for treatment of malaria. However, potent blood stage and antischizontal activity are compelling for causal prophylaxis which does not require fast onset of action. Achieving sufficient on-target selectivity appears to be particularly challenging and should be the primary focus during the next steps of optimization of this chemical series. Encouraging preliminary off-target profile and oral efficacy in a humanized murine model of Pf malaria allowed us to conclude that 1-(pyridin-4-yl)pyrrolidin-2-one derivatives represent a promising starting point for the identification of novel antimalarial prophylactic agents that selectively target Plasmodium PRS.

Systematic evaluation of structure-property relationships and pharmacokinetics in 6-(hetero)aryl-substituted matched pair analogs of amiloride and 5-(N,N-hexamethylene)amiloride

The K+-sparing diuretic amiloride elicits anticancer activities in multiple animal models. During our recent medicinal chemistry campaign aiming to identify amiloride analogs with improved properties for potential use in cancer, we discovered novel 6-(hetero)aryl-substituted amiloride and 5-(N,N-hexamethylene)amiloride (HMA) analogs with up to 100-fold higher potencies than the parent compounds against urokinase plasminogen activator (uPA), one of amiloride's putative anticancer targets, and no diuretic or antikaliuretic effects. Here, we report the systematic evaluation of structure-property relationships (lipophilicity, aqueous solubility and in vitro metabolic stability in human and mouse liver microsomes) in twelve matched pair analogs selected from our 6-substituted amiloride and HMA libraries. Mouse plasma stability, plasma protein binding, Caco-2 cell permeability, cardiac ion channel activity and pharmacokinetics in mice (PO and IV) and rats (IV) are described alongside amiloride and HMA comparators for a subset of the four most promising matched-pair analogs. The findings combined with earlier uPA activity/selectivity and other data ultimately drove selection of two analogs (AA1-39 and AA1-41) that showed efficacy in separate mouse cancer metastasis studies.

Potent Antimalarials with Development Potential Identified by Structure-Guided Computational Optimization of a Pyrrole-Based Dihydroorotate Dehydrogenase Inhibitor Series

Dihydroorotate dehydrogenase (DHODH) has been clinically validated as a target for the development of new antimalarials. Experience with clinical candidate triazolopyrimidine DSM265 (1) suggested that DHODH inhibitors have great potential for use in prophylaxis, which represents an unmet need in the malaria drug discovery portfolio for endemic countries, particularly in areas of high transmission in Africa. We describe a structure-based computationally driven lead optimization program of a pyrrole-based series of DHODH inhibitors, leading to the discovery of two candidates for potential advancement to preclinical development. These compounds have improved physicochemical properties over prior series frontrunners and they show no time-dependent CYP inhibition, characteristic of earlier compounds. Frontrunners have potent antimalarial activity in vitro against blood and liver schizont stages and show good efficacy in Plasmodium falciparum SCID mouse models. They are equally active against P. falciparum and Plasmodium vivax field isolates and are selective for Plasmodium DHODHs versus mammalian enzymes.

Discovery of Potent and Fast-Acting Antimalarial Bis-1,2,4-triazines

Novel 3,3'-disubstituted-5,5'-bi(1,2,4-triazine) compounds with potent in vitro activity against Plasmodium falciparum parasites were recently discovered. To improve the pharmacokinetic properties of the triazine derivatives, a new structure-activity relationship (SAR) investigation was initiated with a focus on enhancing the metabolic stability of lead compounds. These efforts led to the identification of second-generation highly potent antimalarial bis-triazines, exemplified by triazine 23, which exhibited significantly improved in vitro metabolic stability (8 and 42 μL/min/mg protein in human and mouse liver microsomes). The disubstituted triazine dimer 23 was also observed to suppress parasitemia in the Peters 4-day test with a mean ED50 value of 1.85 mg/kg/day and exhibited a fast-killing profile, revealing a new class of orally available antimalarial compounds of considerable interest.

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.

Lead Optimization of a Pyrrole-Based Dihydroorotate Dehydrogenase Inhibitor Series for the Treatment of Malaria

Malaria puts at risk nearly half the world's population and causes high mortality in sub-Saharan Africa, while drug resistance threatens current therapies. The pyrimidine biosynthetic enzyme dihydroorotate dehydrogenase (DHODH) is a validated target for malaria treatment based on our finding that triazolopyrimidine DSM265 (1) showed efficacy in clinical studies. Herein, we describe optimization of a pyrrole-based series identified using a target-based DHODH screen. Compounds with nanomolar potency versus Plasmodium DHODH and Plasmodium parasites were identified with good pharmacological properties. X-ray studies showed that the pyrroles bind an alternative enzyme conformation from 1 leading to improved species selectivity versus mammalian enzymes and equivalent activity on Plasmodium falciparum and Plasmodium vivax DHODH. The best lead DSM502 (37) showed in vivo efficacy at similar levels of blood exposure to 1, although metabolic stability was reduced. Overall, the pyrrole-based DHODH inhibitors provide an attractive alternative scaffold for the development of new antimalarial compounds.

Discovery of Acylsulfonohydrazide-Derived Inhibitors of the Lysine Acetyltransferase, KAT6A, as Potent Senescence-Inducing Anti-Cancer Agents

A high-throughput screen designed to discover new inhibitors of histone acetyltransferase KAT6A uncovered CTX-0124143 (1), a unique aryl acylsulfonohydrazide with an IC₅₀ of 1.0 μM. Using this acylsulfonohydrazide as a template, we herein disclose the results of our extensive structure-activity relationship investigations, which resulted in the discovery of advanced compounds such as 55 and 80. These two compounds represent significant improvements on our recently reported prototypical lead WM-8014 (3) as they are not only equivalently potent as inhibitors of KAT6A but are less lipophilic and significantly more stable to microsomal degradation. Furthermore, during this process, we discovered a distinct structural subclass that contains key 2-fluorobenzenesulfonyl and phenylpyridine motifs, culminating in the discovery of WM-1119 (4). This compound is a highly potent KAT6A inhibitor (IC₅₀ = 6.3 nM; K_D = 0.002 μM), competes with Ac-CoA by binding to the Ac-CoA binding site, and has an oral bioavailability of 56% in rats.

Structure-Activity Relationship of Antischistosomal Ozonide Carboxylic Acids

Semisynthetic artemisinins and other bioactive peroxides are best known for their powerful antimalarial activities, and they also show substantial activity against schistosomes-another hemoglobin-degrading pathogen. Building on this discovery, we now describe the initial structure-activity relationship (SAR) of antischistosomal ozonide carboxylic acids OZ418 (2) and OZ165 (3). Irrespective of lipophilicity, these ozonide weak acids have relatively low aqueous solubilities and high protein binding values. Ozonides with para-substituted carboxymethoxy and N-benzylglycine substituents had high antischistosomal efficacies. It was possible to increase solubility, decrease protein binding, and maintain the high antischistosomal activity in mice infected with juvenile and adult Schistosoma mansoni by incorporating a weak base functional group in these compounds. In some cases, adding polar functional groups and heteroatoms to the spiroadamantane substructure increased the solubility and metabolic stability, but in all cases decreased the antischistosomal activity.

An in vitro toolbox to accelerate anti-malarial drug discovery and development

Background

Modelling and simulation are being increasingly utilized to support the discovery and development of new anti-malarial drugs. These approaches require reliable in vitro data for physicochemical properties, permeability, binding, intrinsic clearance and cytochrome P450 inhibition. This work was conducted to generate an in vitro data toolbox using standardized methods for a set of 45 anti-malarial drugs and to assess changes in physicochemical properties in relation to changing target product and candidate profiles.

Methods

Ionization constants were determined by potentiometric titration and partition coefficients were measured using a shake-flask method. Solubility was assessed in biorelevant media and permeability coefficients and efflux ratios were determined using Caco-2 cell monolayers. Binding to plasma and media proteins was measured using either ultracentrifugation or rapid equilibrium dialysis. Metabolic stability and cytochrome P450 inhibition were assessed using human liver microsomes. Sample analysis was conducted by LC–MS/MS.

Results

Both solubility and fraction unbound decreased, and permeability and unbound intrinsic clearance increased, with increasing Log D_7.4. In general, development compounds were somewhat more lipophilic than legacy drugs. For many compounds, permeability and protein binding were challenging to assess and both required the use of experimental conditions that minimized the impact of non-specific binding. Intrinsic clearance in human liver microsomes was varied across the data set and several compounds exhibited no measurable substrate loss under the conditions used. Inhibition of cytochrome P450 enzymes was minimal for most compounds.

Conclusions

This is the first data set to describe in vitro properties for 45 legacy and development anti-malarial drugs. The studies identified several practical methodological issues common to many of the more lipophilic compounds and highlighted areas which require more work to customize experimental conditions for compounds being designed to meet the new target product profiles. The dataset will be a valuable tool for malaria researchers aiming to develop PBPK models for the prediction of human PK properties and/or drug–drug interactions. Furthermore, generation of this comprehensive data set within a single laboratory allows direct comparison of properties across a large dataset and evaluation of changing property trends that have occurred over time with changing target product and candidate profiles.

Falcipain Inhibitors Based on the Natural Product Gallinamide A Are Potent in Vitro and in Vivo Antimalarials

A library of analogues of the cyanobacterium-derived depsipeptide natural product gallinamide A were designed and prepared using a highly efficient and convergent synthetic route. Analogues were shown to exhibit potent inhibitory activity against the Plasmodium falciparum cysteine proteases falcipain 2 and falcipain 3 and against cultured chloroquine-sensitive (3D7) and chloroquine-resistant (W2) strains of P. falciparum. Three lead compounds were selected for evaluation of in vivo efficacy against Plasmodium berghei infection in mice on the basis of their improved blood, plasma, and microsomal stability profiles compared with the parent natural product. One of the lead analogues cured P. berghei-infected mice in the Peters 4 day-suppressive test when administered 25 mg kg^-1 intraperitoneally daily for 4 days. The compound was also capable of clearing parasites in established infections at 50 mg kg^-1 intraperitoneally daily for 4 days and exhibited moderate activity when administered as four oral doses of 100 mg kg^-1.

SAR of a new antischistosomal urea carboxylic acid

Urea carboxylic acids, products of aryl hydantoin hydrolysis, were recently identified as a new antischistosomal chemotype. We now describe a baseline structure-activity relationship (SAR) for this compound series. With one exception, analogs of lead urea carboxylic acid 2 were quite polar with Log D_7.4 values ranging from -1.9 to 1.8, had high aqueous solubilities in the range of 25-100 µg/mL, and were metabolically stable. None of the compounds had measurable in vitro antischistosomal activity or cytotoxicity, but four of these had moderate worm burden reduction (WBR) values of 42-70% when they were administered as single 100 mg/kg oral doses to S. mansoni-infected mice. These data indicate that with the exception of the gem-dimethyl substructure and the distal nitrogen atom of the urea functional group, the rest of the structure of 2 is required for in vivo antischistosomal activity.

Using Human Plasma as an Assay Medium in Caco-2 Studies Improves Mass Balance for Lipophilic Compounds

PURPOSE

To examine the utility of human plasma as an assay medium in Caco-2 permeability studies to overcome poor mass balance and inadequate sink conditions frequently encountered with lipophilic compounds.

METHODS

Caco-2 permeability was assessed for reference compounds with known transport mechanisms using either pH 7.4 buffer or human plasma as the assay medium in both the apical and basolateral chambers. When using plasma, P_app values were corrected for the unbound fraction in the donor chamber. The utility of the approach was assessed by measuring the permeability of selected antimalarial compounds using the two assay media.

RESULTS

Caco-2 cell monolayer integrity and P-gp transporter function were unaffected by the presence of human plasma in the donor and acceptor chambers. For many of the reference compounds having good mass balance with buffer as the medium, higher P_app values were observed with plasma, likely due to improved acceptor sink conditions. The lipophilic antimalarial compounds exhibited low mass balance with buffer, however the use of plasma markedly improved mass balance allowing the determination of more reliable P_app values.

CONCLUSIONS

The results support the utility of human plasma as an alternate Caco-2 assay medium to improve mass balance and permeability measurements for lipophilic compounds.

Isoxazolopyrimidine-Based Inhibitors of Plasmodium falciparum Dihydroorotate Dehydrogenase with Antimalarial Activity

Malaria kills nearly 0.5 million people yearly and impacts the lives of those living in over 90 countries where it is endemic. The current treatment programs are threatened by increasing drug resistance. Dihydroorotate dehydrogenase (DHODH) is now clinically validated as a target for antimalarial drug discovery as a triazolopyrimidine class inhibitor (DSM265) is currently undergoing clinical development. We discovered a related isoxazolopyrimidine series in a phenotypic screen, later determining that it targeted DHODH. To determine if the isoxazolopyrimidines could yield a drug candidate, we initiated hit-to-lead medicinal chemistry. Several potent analogues were identified, including a compound that showed in vivo antimalarial activity. The isoxazolopyrimidines were more rapidly metabolized than their triazolopyrimidine counterparts, and the pharmacokinetic data were not consistent with the goal of a single-dose treatment for malaria.

Inhibitors of histone acetyltransferases KAT6A/B induce senescence and arrest tumour growth

Acetylation of histones by lysine acetyltransferases (KATs) is essential for chromatin organization and function¹. Among the genes coding for the MYST family of KATs (KAT5-KAT8) are the oncogenes KAT6A (also known as MOZ) and KAT6B (also known as MORF and QKF)^2,3. KAT6A has essential roles in normal haematopoietic stem cells^4-6 and is the target of recurrent chromosomal translocations, causing acute myeloid leukaemia^7,8. Similarly, chromosomal translocations in KAT6B have been identified in diverse cancers⁸. KAT6A suppresses cellular senescence through the regulation of suppressors of the CDKN2A locus^9,10, a function that requires its KAT activity¹⁰. Loss of one allele of KAT6A extends the median survival of mice with MYC-induced lymphoma from 105 to 413 days¹¹. These findings suggest that inhibition of KAT6A and KAT6B may provide a therapeutic benefit in cancer. Here we present highly potent, selective inhibitors of KAT6A and KAT6B, denoted WM-8014 and WM-1119. Biochemical and structural studies demonstrate that these compounds are reversible competitors of acetyl coenzyme A and inhibit MYST-catalysed histone acetylation. WM-8014 and WM-1119 induce cell cycle exit and cellular senescence without causing DNA damage. Senescence is INK4A/ARF-dependent and is accompanied by changes in gene expression that are typical of loss of KAT6A function. WM-8014 potentiates oncogene-induced senescence in vitro and in a zebrafish model of hepatocellular carcinoma. WM-1119, which has increased bioavailability, arrests the progression of lymphoma in mice. We anticipate that this class of inhibitors will help to accelerate the development of therapeutics that target gene transcription regulated by histone acetylation.

Antimalarial efficacy of MMV390048, an inhibitor of Plasmodium phosphatidylinositol 4-kinase

As part of the global effort toward malaria eradication, phenotypic whole-cell screening revealed the 2-aminopyridine class of small molecules as a good starting point to develop new antimalarial drugs. Stemming from this series, we found that the derivative, MMV390048, lacked cross-resistance with current drugs used to treat malaria. This compound was efficacious against all Plasmodium life cycle stages, apart from late hypnozoites in the liver. Efficacy was shown in the humanized Plasmodium falciparum mouse model, and modest reductions in mouse-to-mouse transmission were achieved in the Plasmodium berghei mouse model. Experiments in monkeys revealed the ability of MMV390048 to be used for full chemoprotection. Although MMV390048 was not able to eliminate liver hypnozoites, it delayed relapse in a Plasmodium cynomolgi monkey model. Both genomic and chemoproteomic studies identified a kinase of the Plasmodium parasite, phosphatidylinositol 4-kinase, as the molecular target of MMV390048. The ability of MMV390048 to block all life cycle stages of the malaria parasite suggests that this compound should be further developed and may contribute to malaria control and eradication as part of a single-dose combination treatment.

Progress in antischistosomal N,N'-diaryl urea SAR

N,N'-Diaryl ureas have recently emerged as a new antischistosomal chemotype. We now describe physicochemical profiling, in vitro ADME, plasma exposure, and ex vivo and in vivo activities against Schistosoma mansoni for twenty new N,N'-diaryl ureas designed primarily to increase aqueous solubility, but also to maximize structural diversity. Replacement of one of the 4-fluoro-3-trifluoromethylphenyl substructures of lead N,N'-diaryl urea 1 with azaheterocycles and benzoic acids, benzamides, or benzonitriles decreased lipophilicity, and in most cases, increased aqueous solubility. There was no clear relationship between lipophilicity and metabolic stability, although all compounds with 3-trifluoromethyl-4-pyridyl substructures were metabolically stable. N,N'-diaryl ureas containing 4-fluoro-3-trifluoromethylphenyl, 3-trifluoromethyl-4-pyridyl, 2,2-difluorobenzodioxole, or 4-benzonitrile substructures had high activity against ex vivo S. mansoni and relatively low cytotoxicity. N,N-diaryl ureas with 3-trifluoromethyl-4-pyridyl and 2,2-difluorobenzodioxole substructures had the highest exposures whereas those with 4-fluoro-3-trifluoromethylphenyl substructures had the best in vivo antischistosomal activities. There was no direct correlation between compound exposure and in vivo activity.

Does the Use of Volumetric Modulated Arc Therapy Reduce Gastrointestinal Symptoms after Pelvic Radiotherapy?

AIMS

Growing numbers of patients with cancer are surviving after treatment with pelvic radiotherapy. We evaluated the technique of volumetric modulated arc therapy (VMAT), which delivers a decreased dose to the organs at risk. We aimed to determine outcomes of this technique in terms of patient-reported acute toxicity and late effects and correlate the frequency of gastrointestinal symptoms with the volume of bowel receiving radiation dose.

MATERIALS AND METHODS

Patients who were to receive VMAT for gynaecological malignancy completed patient-reported outcomes at baseline, the end of treatment, 8 weeks and 1 year. The rates of patient-reported toxicity were correlated with the volume of bowel irradiated.

RESULTS

The frequencies of patient-reported gastrointestinal symptoms increased in the acute toxicity phase and tended to improve at 1 year, with the exception of faecal incontinence and rectal bleeding (P < 0.05). There was not a strong association between the volume of small bowel that was irradiated (P > 0.05 at all dose levels) and reported toxicity, suggesting that other factors are involved in the development of toxicity.

CONCLUSION

Although VMAT decreases the dose delivered to the small bowel, this does not translate into a reduction in patient-reported toxicity.

A Triazolopyrimidine-Based Dihydroorotate Dehydrogenase Inhibitor with Improved Drug-like Properties for Treatment and Prevention of Malaria

The emergence of drug-resistant malaria parasites continues to hamper efforts to control this lethal disease. Dihydroorotate dehydrogenase has recently been validated as a new target for the treatment of malaria, and a selective inhibitor (DSM265) of the Plasmodium enzyme is currently in clinical development. With the goal of identifying a backup compound to DSM265, we explored replacement of the SF₅-aniline moiety of DSM265 with a series of CF₃-pyridinyls while maintaining the core triazolopyrimidine scaffold. This effort led to the identification of DSM421, which has improved solubility, lower intrinsic clearance, and increased plasma exposure after oral dosing compared to DSM265, while maintaining a long predicted human half-life. Its improved physical and chemical properties will allow it to be formulated more readily than DSM265. DSM421 showed excellent efficacy in the SCID mouse model of P. falciparum malaria that supports the prediction of a low human dose (<200 mg). Importantly DSM421 showed equal activity against both P. falciparum and P. vivax field isolates, while DSM265 was more active on P. falciparum. DSM421 has the potential to be developed as a single-dose cure or once-weekly chemopreventative for both P. falciparum and P. vivax malaria, leading to its advancement as a preclinical development candidate.

Revisiting the SAR of the Antischistosomal Aryl Hydantoin (Ro 13-3978)

The aryl hydantoin 1 (Ro 13-3978) was identified in the early 1980s as a promising antischistosomal lead compound. However, this series of aryl hydantoins produced antiandrogenic side effects in the host, a not unexpected outcome given their close structural similarity to the antiandrogenic drug nilutamide. Building on the known SAR of this compound series, we now describe a number of analogs of 1 designed to maximize structural diversity guided by incorporation of substructures and functional groups known to diminish ligand–androgen receptor interactions. These analogs had calculated polar surface area (PSA), measured LogD_7.4, aqueous kinetic solubility, and estimated plasma protein binding values in ranges predictive of good ADME profiles. The principal SAR insight was that the hydantoin core of 1 is required for high antischistosomal activity. We identified several compounds with high antischistosomal efficacy that were less antiandrogenic than 1. These data provide direction for the ongoing optimization of antischistosomal hydantoins.

Identification of a Potential Antimalarial Drug Candidate from a Series of 2-Aminopyrazines by Optimization of Aqueous Solubility and Potency across the Parasite Life Cycle

Introduction of water-solubilizing groups on the 5-phenyl ring of a 2-aminopyrazine series led to the identification of highly potent compounds against the blood life-cycle stage of the human malaria parasite Plasmodium falciparum. Several compounds displayed high in vivo efficacy in two different mouse models for malaria, P. berghei-infected mice and P. falciparum-infected NOD-scid IL-2Rγ^null mice. One of the frontrunners, compound 3, was identified to also have good pharmacokinetics and additionally very potent activity against the liver and gametocyte parasite life-cycle stages.

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.

Tetrahydro-2-naphthyl and 2-Indanyl Triazolopyrimidines Targeting Plasmodium falciparum Dihydroorotate Dehydrogenase Display Potent and Selective Antimalarial Activity

Malaria persists as one of the most devastating global infectious diseases. The pyrimidine biosynthetic enzyme dihydroorotate dehydrogenase (DHODH) has been identified as a new malaria drug target, and a triazolopyrimidine-based DHODH inhibitor 1 (DSM265) is in clinical development. We sought to identify compounds with higher potency against Plasmodium DHODH while showing greater selectivity toward animal DHODHs. Herein we describe a series of novel triazolopyrimidines wherein the p-SF5-aniline was replaced with substituted 1,2,3,4-tetrahydro-2-naphthyl or 2-indanyl amines. These compounds showed strong species selectivity, and several highly potent tetrahydro-2-naphthyl derivatives were identified. Compounds with halogen substitutions displayed sustained plasma levels after oral dosing in rodents leading to efficacy in the P. falciparum SCID mouse malaria model. These data suggest that tetrahydro-2-naphthyl derivatives have the potential to be efficacious for the treatment of malaria, but due to higher metabolic clearance than 1, they most likely would need to be part of a multidose regimen.

A long-duration dihydroorotate dehydrogenase inhibitor (DSM265) for prevention and treatment of malaria

Malaria is one of the most significant causes of childhood mortality, but disease control efforts are threatened by resistance of the Plasmodium parasite to current therapies. Continued progress in combating malaria requires development of new, easy to administer drug combinations with broad-ranging activity against all manifestations of the disease. DSM265, a triazolopyrimidine-based inhibitor of the pyrimidine biosynthetic enzyme dihydroorotate dehydrogenase (DHODH), is the first DHODH inhibitor to reach clinical development for treatment of malaria. We describe studies profiling the biological activity, pharmacological and pharmacokinetic properties, and safety of DSM265, which supported its advancement to human trials. DSM265 is highly selective toward DHODH of the malaria parasite Plasmodium, efficacious against both blood and liver stages of P. falciparum, and active against drug-resistant parasite isolates. Favorable pharmacokinetic properties of DSM265 are predicted to provide therapeutic concentrations for more than 8 days after a single oral dose in the range of 200 to 400 mg. DSM265 was well tolerated in repeat-dose and cardiovascular safety studies in mice and dogs, was not mutagenic, and was inactive against panels of human enzymes/receptors. The excellent safety profile, blood- and liver-stage activity, and predicted long half-life in humans position DSM265 as a new potential drug combination partner for either single-dose treatment or once-weekly chemoprevention. DSM265 has advantages over current treatment options that are dosed daily or are inactive against the parasite liver stage.

Phenotypic relationships between docility and reproduction in Angus heifers

The objective of this study was to elucidate the phenotypic relationships between docility and first-service AI conception rate in heifers. Data ( = 337) collected from 3 cooperator herds in Kansas at the start of synchronization protocol included exit velocity (EV), chute score (CS), fecal cortisol (FC), and blood serum cortisol (BC). Data were analyzed using logistic regression with 30-d pregnancy rate as the dependent variable. The model included the fixed effect of contemporary group and the covariates FC, BC, EV, CS, BW, and age. Correlation coefficients were calculated between all continuous traits. Pregnancy rate ranged from 34% to 60% between herds. Blood cortisol positively correlated with EV ( = 0.22, < 0.01), negatively correlated with age ( = -0.12, < 0.03), and tended to be negatively correlated with BW ( = -0.10, = 0.09). Exit velocity was positively correlated with CS ( = 0.24, < 0.01) and negatively correlated with BW ( = -0.15, < 0.01) and age ( = -0.12, < 0.03). Chute score negatively correlated with age ( = -0.14, < 0.01), and age and BW were moderately positively correlated ( = 0.42, < 0.01), as expected. Older, heavier animals generally had better temperament, as indicated by lower BC, EV, and CS. The power of our test could detect no significant predictors of 30-d pregnancy for the combined data from all ranches. When the data were divided by ranch, CS ( < 0.03) and BW ( < 0.01) were both significant predictors for 30-d pregnancy for ranch 1. The odds ratio estimate for CS has an inverse relationship with pregnancy, meaning that a 1-unit increase in average CS will reduce the probability of pregnancy at ranch 1 by 48.1%. Weight also has a negative impact on pregnancy because a 1-kg increase in BW will decrease the probability of pregnancy by 2.2%. Fertility is a complex trait that depends on many factors; our data suggest that docility is 1 factor that warrants further investigation.

6-Arylpyrazine-2-carboxamides: A New Core for Trypanosoma brucei Inhibitors

From a whole-organism high throughput screen of approximately 87000 compounds against Trypanosoma brucei brucei, we recently identified eight new unique compounds for the treatment of human African trypanosomiasis. In an effort to understand the structure-activity relationships around these compounds, we report for the first time our results on a new class of trypanocides, the pyrazine carboxamides. Attracted by the low molecular weight (270 g·mol(-1)) of our starting hit (9) and its potency (0.49 μM), the SAR around the core was explored, leading to compounds having an EC50 as low as 25 nM against T. b. brucei and being more than 1500 times less toxic against mammalian L6 and HEK293 cell lines. The most potent compounds in the series were exquisitely selective for T. brucei over a panel of other protozoan parasites, showing an excellent correlation with the human infective parasite Trypanosoma brucei rhodesiense, the most potent compound (65) having an EC50 of 24 nM. The compounds are highly drug-like and are able to penetrate the CNS, their only limitation currently being their rate of microsomal metabolism. To that effect, efforts to identify potential metabolites of selected compounds are also reported.

A multicentre, prospective, randomised, blinded clinical trial to compare some perioperative effects of buprenorphine or butorphanol premedication before equine elective general anaesthesia and surgery

Reasons for performing study

Buprenorphine, a μ‐agonist opioid, has recently been licensed for equine use, but butorphanol, a κ‐agonist opioid, is more commonly used in horses. The effect of the 2 opioids has not previously been compared in a large clinical study.

Objectives

To compare post operative analgesia and physiological variables in horses undergoing elective surgery following premedication with either buprenorphine or butorphanol in a conventional clinical setting.

Study design

Multicentre, prospective, randomised, blinded clinical investigation.

Methods

Eighty‐nine healthy horses admitted for elective surgery to one of 6 UK equine veterinary clinics were premedicated with acepromazine, a nonsteroidal anti‐inflammatory drug, and romifidine followed by intravenous (i.v.) buprenorphine or butorphanol. Anaesthesia was induced with diazepam/ketamine and maintained with isoflurane in oxygen. A range of surgical procedures were performed and supplementary anaesthetic agents given as required. Physiological variables were monitored during anaesthesia and pain, ataxia, sedation and vital function were assessed post operatively. Data were analysed using t‐tests, ANOVA, Mann–Whitney U‐test and Chi‐squared test as appropriate and P<0.05 was regarded as significant, except for multiple comparisons, when P<0.01 was used.

Results

Surgery was carried out successfully in all cases and no mortality or serious morbidity occurred. Physiological variables remained within normal limits and all horses recovered successfully, most standing within 1 h of ceasing anaesthesia. There were no significant differences between groups in any variable except post operative pain when scores (simple descriptive scale) between 3 and 6 h were significantly lower after buprenorphine than after butorphanol.

Conclusions

Horses experienced less post operative pain after buprenorphine than after butorphanol premedication. Compared with butorphanol, buprenorphine did not cause any different effects on vital function.

Effective cryopreservation of golden Syrian hamster embryos by open pulled straw vitrification

Golden Syrian hamster embryos are difficult to cryopreserve due to their high sensitivity to cryoprotectants and in vitro handling. The objective of this study is to develop a robust open pulled straw (OPS) vitrification technique for cryopreserving hamster embryos at various developmental stages. We first systematically tested the concentrations of cryoprotectants and the exposure times of two-cell embryos to various vitrification solutions. We identified pretreatment of two-cell embryos with 10% (v/v) ethylene glycol (EG) + 10% (v/v) dimethylsulfoxide (DMSO) for 30 s followed by exposure in the vitrification solution, EDFS30 (containing 15% EG + 15% DMSO), for 30 s before plunging into liquid nitrogen (two-step exposure method) as the optimal OPS vitrification protocol. We then investigated the resourcefulness of this protocol for vitrifying hamster embryos at different developmental stages. The results showed that high blastocyst rates from embryos vitrified at two-cell, four-cell, eight-cell, or morula stage (62%, 78%, 80%, or 72%, respectively), but not those verified at pronuclear (0%) or blastocyst stage (24%; P < 0.05), were achieved by this protocol. When embryos vitrified at the two-cell stage were recovered and then directly transferred to recipient females, 29% of them developed to term, a development rate not significantly different (P > 0.05) from the 40% birth rate of the unvitrified controls. In conclusion, we have developed an effective two-step OPS vitrification protocol for hamster embryos.

Interlayer structure and self-healing in suspensions of brush-stabilized nanoplatelets with smectic order

We have investigated the rheology of an uncured epoxy fluid containing high aspect ratio (length/thickness ≈ 160) α-zirconium phosphate (ZrP) nanoplatelets with smectic order. The nanoplatelets were exfoliated into monocrystalline sheets with uniform thickness using a monoamine-terminated oligomer. The oligomers were densely grafted to the plate surfaces and behave as a molecular brush. Suspensions containing ∼ 2 vol.% ZrP and above show liquid crystalline order with scattering peaks characteristic of a smectic (layered) mesophase. At much higher loading, ∼ 4 vol.% ZrP, there is a sharp transition in visual appearance, steady shear rheology, and linear and non-linear viscoelasticity that is attributed to the reversible interdigitation of oligomer chains between closely spaced layers. The oligomers are proposed to serve as inter-lamellar bridges that store elastic stresses for intermediate rates of deformation, but are able to relax on longer time scales. Under steady shearing conditions, the smectic suspensions with "overlapped" microstructure show a discontinuous flow curve characteristic of shear banding that is attributed to the dynamic pull-out of oligomer chains from the overlap region. At high shear rates, the limiting viscosity of the concentrated suspensions is on the same order of magnitude as the unfilled suspending fluid. When the rate of deformation is reduced below a critical time scale, the original network strength, and corresponding microstructure, is recovered through a passive self-healing process. The unique combination of concentration-dependent yield stress, low post-yield viscosity, and self-healing is potentially useful for various applications in the liquid state, and desirable for scalable processing of nanocomposite materials for structural applications.

Orally bioavailable 6-chloro-7-methoxy-4(1H)-quinolones efficacious against multiple stages of Plasmodium

The continued proliferation of malaria throughout temperate and tropical regions of the world has promoted a push for more efficacious treatments to combat the disease. Unfortunately, more recent remedies such as artemisinin combination therapies have been rendered less effective due to developing parasite resistance, and new drugs are required that target the parasite in the liver to support the disease elimination efforts. Research was initiated to revisit antimalarials developed in the 1940s and 1960s that were deemed unsuitable for use as therapeutic agents as a result of poor understanding of both physicochemical properties and parasitology. Structure–activity and structure–property relationship studies were conducted to generate a set of compounds with the general 6-chloro-7-methoxy-2-methyl-4(1H)-quinolone scaffold which were substituted at the 3-position with a variety of phenyl moieties possessing various properties. Extensive physicochemical evaluation of the quinolone series was carried out to downselect the most promising 4(1H)-quinolones, 7, 62, 66, and 67, which possessed low-nanomolar EC₅₀ values against W2 and TM90-C2B as well as improved microsomal stability. Additionally, in vivo Thompson test results using Plasmodium berghei in mice showed that these 4(1H)-quinolones were efficacious for the reduction of parasitemia at >99% after 6 days.

Discovery, synthesis, and optimization of antimalarial 4(1H)-quinolone-3-diarylethers

The historical antimalarial compound endochin served as a structural lead for optimization. Endochin-like quinolones (ELQ) were prepared by a novel chemical route and assessed for in vitro activity against multidrug resistant strains of Plasmodium falciparum and against malaria infections in mice. Here we describe the pathway to discovery of a potent class of orally active antimalarial 4(1H)-quinolone-3-diarylethers. The initial prototype, ELQ-233, exhibited low nanomolar IC₅₀ values against all tested strains including clinical isolates harboring resistance to atovaquone. ELQ-271 represented the next critical step in the iterative optimization process, as it was stable to metabolism and highly effective in vivo. Continued analoging revealed that the substitution pattern on the benzenoid ring of the quinolone core significantly influenced reactivity with the host enzyme. This finding led to the rational design of highly selective ELQs with outstanding oral efficacy against murine malaria that is superior to established antimalarials chloroquine and atovaquone.

Medicinal chemistry optimization of antiplasmodial imidazopyridazine hits from high throughput screening of a SoftFocus kinase library: part 1

A novel class of imidazopyridazines identified from whole cell screening of a SoftFocus kinase library was synthesized and evaluated for antiplasmodial activity against K1 (multidrug resistant strain) and NF54 (sensitive strain). Structure-activity relationship studies led to the identification of highly potent compounds against both strains. Compound 35 was highly active (IC50: K1 = 6.3 nM, NF54 = 7.3 nM) and comparable in potency to artesunate, and 35 exhibited 98% activity in the in vivo P. berghei mouse model (4-day test by Peters) at 4 × 50 mg/kg po. Compound 35 was also assessed against P. falciparum in the in vivo SCID mouse model where the efficacy was found to be more consistent with the in vitro activity. Furthermore, 35 displayed high (78%) rat oral bioavailability with good oral exposure and plasma half-life. Mice exposure at the same dose was 10-fold lower than in rat, suggesting lower oral absorption and/or higher metabolic clearance in mice.

2,4-Diaminothienopyrimidines as orally active antimalarial agents

A novel series of 2,4-diaminothienopyrimidines with potential as antimalarials was identified from whole-cell high-throughput screening of a SoftFocus ion channel library. Synthesis and structure-activity relationship studies identified compounds with potent antiplasmodial activity and low in vitro cytotoxicity. Several of these analogues exhibited in vivo activity in the Plasmodium berghei mouse model when administered orally. However, inhibition of the hERG potassium channel was identified as a liability for this series.

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.

In vitro and in vivo characterization of the antimalarial lead compound SSJ-183 in Plasmodium models

The objective of this work was to characterize the in vitro (Plasmodium falciparum) and in vivo (Plasmodium berghei) activity profile of the recently discovered lead compound SSJ-183. The molecule showed in vitro a fast and strong inhibitory effect on growth of all P. falciparum blood stages, with a tendency to a more pronounced stage-specific action on ring forms at low concentrations. Furthermore, the compound appeared to be equally efficacious on drug-resistant and drug-sensitive parasite strains. In vivo, SSJ-183 showed a rapid onset of action, comparable to that seen for the antimalarial drug artesunate. SSJ-183 exhibited a half-life of about 10 hours and no significant differences in absorption or exposure between noninfected and infected mice. SSJ-183 appears to be a promising new lead compound with an attractive antimalarial profile.

Quinolone-3-diarylethers: a new class of antimalarial drug

The goal for developing new antimalarial drugs is to find a molecule that can target multiple stages of the parasite's life cycle, thus impacting prevention, treatment, and transmission of the disease. The 4(1H)-quinolone-3-diarylethers are selective potent inhibitors of the parasite's mitochondrial cytochrome bc1 complex. These compounds are highly active against the human malaria parasites Plasmodium falciparum and Plasmodium vivax. They target both the liver and blood stages of the parasite as well as the forms that are crucial for disease transmission, that is, the gametocytes, the zygote, the ookinete, and the oocyst. Selected as a preclinical candidate, ELQ-300 has good oral bioavailability at efficacious doses in mice, is metabolically stable, and is highly active in blocking transmission in rodent models of malaria. Given its predicted low dose in patients and its predicted long half-life, ELQ-300 has potential as a new drug for the treatment, prevention, and, ultimately, eradication of human malaria.

Structure-activity relationship studies of pyrrolone antimalarial agents

Previously reported pyrrolones, such as TDR32570, exhibited potential as antimalarial agents; however, while these compounds have potent antimalarial activity, they suffer from poor aqueous solubility and metabolic instability. Here, further structure–activity relationship studies are described that aimed to solve the developability issues associated with this series of compounds. In particular, further modifications to the lead pyrrolone, involving replacement of a phenyl ring with a piperidine and removal of a potentially metabolically labile ester by a scaffold hop, gave rise to derivatives with improved in vitro antimalarial activities against Plasmodium falciparum K1, a chloroquine-and pyrimethamine-resistant parasite strain, with some derivatives exhibiting good selectivity for parasite over mammalian (L6) cells. Three representative compounds were selected for evaluation in a rodent model of malaria infection, and the best compound showed improved ability to decrease parasitaemia and a slight increase in survival.

3-(Oxazolo[4,5-b]pyridin-2-yl)anilides as a novel class of potent inhibitors for the kinetoplastid Trypanosoma brucei, the causative agent for human African trypanosomiasis

A whole organism high-throughput screen of approximately 87,000 compounds against Trypanosoma brucei brucei led to the recent discovery of several novel compound classes with low micromolar activity against this organism and without appreciable cytotoxicity to mammalian cells. Herein we report a structure-activity relationship (SAR) investigation around one of these hit classes, the 3-(oxazolo[4,5-b]pyridin-2-yl)anilides. Sharp SAR is revealed, with our most active compound (5) exhibiting an IC₅₀ of 91 nM against the human pathogenic strain T.b. rhodesiense and being more than 700 times less toxic towards the L6 mammalian cell line. Physicochemical properties are attractive for many compounds in this series. For the most potent representatives, we show that solubility and metabolic stability are key parameters to target during future optimisation.

Design, structure-activity relationship and in vivo efficacy of piperazine analogues of fenarimol as inhibitors of Trypanosoma cruzi

A scaffold hopping exercise undertaken to expand the structural diversity of the fenarimol series of anti-Trypanosoma cruzi (T. cruzi) compounds led to preparation of simple 1-[phenyl(pyridin-3-yl)methyl]piperazinyl analogues of fenarimol which were investigated for their ability to inhibit T. cruzi in vitro in a whole organism assay. A range of compounds bearing amide, sulfonamide, carbamate/carbonate and aryl moieties exhibited low nM activities and two analogues were further studied for in vivo efficacy in a mouse model of T. cruzi infection. One compound, the citrate salt of 37, was efficacious in a mouse model of acute T. cruzi infection after once daily oral dosing at 20, 50 and 100 mg/kg for 5 days.

Analogues of fenarimol are potent inhibitors of Trypanosoma cruzi and are efficacious in a murine model of Chagas disease

We report the discovery of nontoxic fungicide fenarimol (1) as an inhibitor of Trypanosoma cruzi ( T. cruzi ), the causative agent of Chagas disease, and the results of structure-activity investigations leading to potent analogues with low nM IC(50)s in a T. cruzi whole cell in vitro assay. Lead compounds suppressed blood parasitemia to virtually undetectable levels after once daily oral dosing in mouse models of T. cruzi infection. Compounds are chemically tractable, allowing rapid optimization of target biological activity and drug characteristics. Chemical and biological studies undertaken in the development of the fenarimol series toward the goal of delivering a new drug candidate for Chagas disease are reported.