Melissa Sykes

Griffith University · Eskitis Institute for Drug Discovery

The repurposing of approved drugs is an appealing method to fast-track the development of novel therapies for neglected diseases. Amiodarone and dronedarone, two approved antiarrhythmic agents, have been reported to have potential for the management of Chagas disease patients displaying symptomatic heart pathology. More recently, it has been sugges...

Giardia duodenalis is the causative agent of the neglected diarrhoeal disease giardiasis. While often self-limiting, giardiasis is ubiquitous and impacts hundreds of millions of people annually. It is also a common gastro-intestinal disease of domestic pets, wildlife, and livestock animals. However, despite this impact, there is no vaccine for Giar...

Chagas disease is caused by infection with the protozoan parasite, Trypanosoma cruzi. The disease causes ~12,000 deaths annually and is one of the world’s 20 neglected tropical diseases, as defined by the World Health Organisation. The drug discovery pipeline for Chagas disease currently has few new clinical candidates, with high attrition rates an...

Tuberculosis and parasitic infections continue to impose a significant threat to global public health and economic growth. There is an urgent need to develop new treatments to combat these diseases. Here, we report the in vitro and in vivo profiles of a new bicyclic nitroimidazole subclass, namely, nitroimidazopyrazinones, against mycobacteria and...

Chagas disease caused by the protozoan Trypanosoma cruzi is endemic to 21 countries in the Americas, effects approximately 6 million people and on average results in 12,000 deaths annually. Human African Trypanosomiasis (HAT) is caused by the Trypanosoma brucei sub-species, endemic to 36 countries within sub-Saharan Africa. Treatment regimens for t...

Tuberculosis remains one of the leading causes of death from a single infectious agent, surpassing both AIDS and malaria. In recent years, two bicyclic nitroimidazole drugs, delamanid and pretomanid have been approved to treat this airborne infection. This has spurred a renewed interest in developing new and improved nitroimidazole analogs. We have...

Following the approval of delamanid and pretomanid as new drugs to treat drug-resistant tuberculosis, there is now a renewed interest in bicyclic nitroimidazole scaffolds as a source of therapeutics against infectious diseases. We recently described a nitroimidazopyrazinone bicyclic subclass with promising antitubercular and antiparasitic activity,...

African sleeping sickness is a potentially fatal neglected disease affecting sub-Saharan Africa. High-throughput screening identified the thiazolyl–benzothiophenamide 1 to be active against the causative parasite, Trypanosoma brucei. This work establishes structure–activity relationships of 1, guiding the design of second generation derivatives. Af...

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 w...

Trypanosoma cruzi and Trypanosoma brucei are the parasitic causative agents of Chagas disease and human African trypanosomiasis (HAT), respectively. The drugs currently used to treat these diseases are not efficacious against all stages and/or parasite sub-species, often displaying side effects. Herein, we report the SAR exploration of a novel hit,...

Trypanosoma cruzi parasites utilise de novo pyrimidine biosynthesis to produce DNA and survive within mammalian host cells. This pathway can be hijacked to assess the replication of intracellular parasites with the exogenous addition of a DNA specific probe. To identify suitable probe compounds for this application, a collection of pyrimidine nucle...

Trypanosoma brucei (T. brucei) and Trypanosoma cruzi (T. cruzi) are causative agents of parasitic diseases known as human African trypanosomiasis and Chagas disease, respectively. Together, these diseases affect 68 million people around the world. Current treatments are unsatisfactory, frequently associated with intolerable side-effects, and genera...

The cubane phenyl ring bioisostere paradigm was further explored in an extensive study covering a wide range of pharmaceutical and agrochemical templates, which included antibiotics (cefaclor, penicillin G) and antihistamine (diphenhydramine), a smooth muscle relaxant (alverine), an anaesthetic (ketamine), an agrochemical instecticide (triflumuron)...

The first approaches to the 10'-anthronyl-2-anthraquinone skeleton have been devised, allowing two syntheses of the marine natural product albopunctatone. Both routes involve regioselective addition of a nucleophilic masked anthraquinone to a protected chrysazin derivative; the best affords albopunctatone in five steps and 35% overall yield. Albopu...

Tuberculosis and parasitic diseases, such as giardiasis, amebiasis, leishmaniasis and trypanosomiasis, all urgently require improved treatment options. Recently, it has been shown that anti-tubercular bicyclic nitroimidazoles such as pretomanid and delamanid have potential as repurposed therapeutics for the treatment of visceral leishmaniasis. Here...

Using high throughput, high-content imaging, a proprietary library was screened against intracellular Trypanosoma cruzi amastigotes to identify compounds with novel activity against the parasite. Five inhibitors were discovered, which did not clear all of the parasites from 3T3 host cells following 48 hours exposure, and were identified as putative...

Kinetoplastid parasites cause vector-borne parasitic diseases including leishmaniasis, human African trypanosomiasis (HAT) and Chagas disease. These Neglected Tropical Diseases (NTDs) impact on some of the world’s lowest socioeconomic communities. Current treatments for these diseases cause severe toxicity and have limited efficacy, highlighting th...

Open access drug discovery provides a substantial resource for diseases primarily affecting the poor and disadvantaged. The open access Pathogen Box is comprised of a collection of compounds with demonstrated biological activity against specific pathogenic organisms. The supply of this resource by the Medicines for Malaria Venture has the potential...

Background In the fight against malaria, the discovery of chemical compounds with a novel mode of action and/or chemistry distinct from currently used drugs is vital to counteract the parasite’s known ability to develop drug resistance. Another desirable aspect is efficacy against gametocytes, the sexual developmental stage of the parasite which en...

We have developed a high content 384- well, image-based assay to estimate the effect of compound treatment on Trypanosoma cruzi amastigotes in 3T3 fibroblasts. In the same well, the effect of compound activity on host cells can also be determined, as an initial indicator of cytotoxicity. This assay has been used to identify active compounds from an...

From a whole-organism high throughput screen of approximately 87,000 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...

The supply of (-)-hopeaphenol (1) was achieved via enzymatic biotransformation in order to provide material for preclinical investigation. High-throughput screening of a prefractionated natural product library aimed to identify compounds that inhibit the bacterial virulence type III secretion system (T3SS) identified several fractions derived from...

The synthesis and anti-trypanosomal activity of a compound library based on a phenoxymethylbenzamide hit discovered in a high throughput screen is described. Several of the analogues exhibited potent activity against Trypanosoma brucei rhodesiense, a human infective strain of the trypanosome parasite, that serve as lead compounds for further optimi...

A whole-organism screen of approximately 87,000 compounds against Trypanosoma brucei brucei identified a number of promising compounds for medicinal chemistry optimization. One of these classes of compounds we termed the pyridyl benzamides. While the initial hit had an IC50 of 12 µM, it was small enough to be attractive for further optimization and...

Marine natural products are a diverse, unique collection of compounds with immense therapeutic potential. This has resulted in these molecules being evaluated for a number of different disease indications including the neglected protozoan diseases, human African trypanosomiasis and Chagas disease, for which very few drugs are currently available. T...

Determining the activity of a compound and the potential impact on a diseased state is frequently undertaken using phenotypic or target based approaches. Phenotypic based screens have the added advantage of the whole organism being exposed to the compound, thus all the targets and biological pathways associated with it (polypharmacology). Cell pene...

Tables S1, S2, S3 and S4: Analogues of the top 6 hit compounds. SAR mining revealed those compounds in the library that was screened that were structurally related to the 6 hit compounds. Tables show structure and activities of these compounds over the T.b. brucei primary screening and retest campaigns. Table S1 = compounds 1 and 2; Table S2 = comp...

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Human African Trypanosomiasis (HAT) is caused by two trypanosome sub-species, Trypanosoma brucei rhodesiense and Trypanosoma brucei gambiense. Drugs available for the treatment of HAT have significant issues related to difficult administration regimes and limited efficacy across species and disease stages. Hence, there is considerable need to find...

Bioassay-guided isolation of the CH(2)Cl(2)/MeOH extract from the Australian sponge Iotrochota sp. resulted in the purification of two new N-cinnamoyl-amino acids, iotrochamides A (1) and B (2). The chemical structures of 1 and 2 were determined by 1D/2D NMR and MS data analyses. Compounds 1 and 2 were shown to inhibit Trypanosoma brucei brucei wit...

A high-throughput screening campaign using a prefractionated natural product library and an in vitro Pseudomonas aeruginosa (PAO200 strain) assay identified two antibacterial fractions derived from the marine sponge Suberea ianthelliformis. Mass-directed isolation of the CH(2)Cl(2)/CH(3)OH extract from S. ianthelliformis resulted in the purificatio...

During a high-throughput screening campaign of a prefractionated natural product library, fractions from the Chinese vine Gnetum montanum showed in vitro activity against Pseudomonas aeruginosa wild-type strain, PAO1. UV-directed isolation of the organic extract from the vine leaves resulted in the purification of the new natural products N-methyll...

Ethanolic extracts prepared from the leaves of Psidium guajava were evaluated for anti-trypanosoma and cytotoxicity activity in the bloodstream species of Trypanosoma brucei brucei (BS427) and HEK293 in 384-well Alamar Blue assays respectively. Cytotoxicity activity in HEK293 cells was subsequently used to estimate the selectivity index of the extr...

Bioassay-guided fractionation of the CH(2)Cl(2)/MeOH extract of the Australian marine sponge Pseudoceratina sp. resulted in the purification of four new bromotyrosine alkaloids, pseudoceramines A-D (1-4), along with a known natural product, spermatinamine (5). The structures of 1-5 were determined by spectroscopic methods. Pseudoceramines A (1) and...

Mass-directed isolation of the CH(2)Cl(2)/CH(3)OH extract from the marine bryozoan Amathia tortusa resulted in the purification of two new brominated alkaloids, convolutamines I (1) and J (2). The structures of 1 and 2 were determined following spectroscopic data analysis. Both compounds were isolated during a drug discovery program aimed at identi...

isolation together with amathamide H (III)

Three polyvalent Streptomyces phages were used to isolate four Micromonospora species (M. carbonacea, M. chalcea, M. purpureochromogenes, and M. inositola) from mine-site rhizosphere soils in Western Australia. Streptomyces violascens was isolated using selective isolation techniques from the same soils. The Micromonspora spp. were examined for the...

Mass-directed fractionation based on a Trypanosoma brucei brucei active fraction from the Australian sponge Pseudoceratina sp. led to the isolation of a novel bromotyrosine alkaloid, pseudoceratinazole A (1). Compound 1 is the first dimeric bromotyrosine alkaloid containing an imidazole-bridging moiety. Yes Yes

Isolation and structure elucidation of the novel secondary metabolite α-pyrone (I), named 7′,8′-dihydroobolactone, are reported.

Bioassay-guided fractionation of the CH(2)Cl(2)/MeOH extract from the Australian plant Glochidion sumatranum resulted in the isolation of four new galloylated flavanonols, (2R,3R)-dihydromyricetin-4'-O-(3''-O-methyl)-gallate (1), (2R,3R)-dihydromyricetin-3'-O-(3''-O-methyl)-gallate (2), (2R,3R)-dihydromyricetin-4'-O-gallate (3), and (2R,3R)-dihydro...

Two novel alkaloids, wilsoniamines A and B, both possessing a hexahydropyrrolo[1,2-c]imidazol-1-one ring system that has not previously been found in nature, together with a new alkaloid, amathamide H and a known alkaloid, amathamide C were isolated from the temperate Australian bryozoan, Amathia wilsoni. MS and NMR analysis established the structu...

New drugs are needed to help overcome the increasing problem of drug resistance in parasites that cause diseases such as malaria and trypanosomiasis. In this study, alkaloid compounds isolated from extracts of the plants Flindersia amboinensis, Stephania zippeliana and Voacanga papuana from Papua New Guinea and Flindersia acuminata from Australia w...

A novel pyridoacridine alkaloid 12-deoxyascididemin (I) is isolated together with the known ascididemin (II) and eilatin and their biological evaluation shows potent antitrypanosomal activity.

Mass-directed isolation of the CH(2)Cl(2)/MeOH extract from the leaves of Cryptocarya obovata resulted in the purification of a new trypanocidal alpha-pyrone, 7',8'-dihydroobolactone (1). The chemical structure of 1 was determined by 1D/2D NMR, MS and CD data analysis. 7',8'-Dihydroobolactone was shown to inhibit Trypanosoma brucei brucei with an I...

Bioassay-guided fractionation of the crude CH2Cl2/MeOH extract from the Australian ascidian Polysyncraton echinatum led to the isolation of a new pyridoacridine alkaloid, 12-deoxyascididemin (1), along with two known analogues, ascididemin (2) and eilatin (3). The structure of 1 was determined following extensive analysis of 1D/2D NMR and MS data....

Bioassay-guided fractionation of the crude extract from the Australian marine sponge Plakortis sp. led to the isolation of two new cyclic polyketide peroxides, 11,12-didehydro-13-oxo-plakortide Q (1) and 10-carboxy-11,12,13,14-tetranor-plakortide Q (2). Antitrypanosomal studies showed that compound 1 had an IC(50) value of 49 nM against Trypanosoma...

Human African Trypanosomiasis (HAT) is caused by two trypanosome species, Trypanosoma brucei rhodesiense and Trypanosoma brucei gambiense. Current drugs available for the treatment of HAT have significant issues related to toxicity, administration regimes with limited effectiveness across species and disease stages, thus there is a considerable nee...

There is an urgent need for new compounds for the drug development pipeline for treatment of patients with African sleeping sickness. One approach for identifying such compounds is by high throughput screening (HTS) of compound collections. For time and cost considerations, there is a need for the development of an assay that uses at least 384-well...

Bioassay-guided fractionation of the organic extract from the marine sponge Acanthella costata resulted in the isolation of the known natural product, (-)-dibromophakellin (1). Using a fluorescence imaging plate reader (FLIPR) based assay, compound 1 was identified as displaying agonist activity against the alpha(2B) adrenoceptor, with an EC(50) of...

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

A new natural product, lysianadioic acid, was isolated from the plant Lysiana subfalcata as a carboxypeptidase B (CPB) inhibitor. It is a potent inhibitor of CPB with an IC(50) of 0.36 microM. This is the first known example of a small molecule CPB inhibitor isolated from plant origin. Its structure was determined by NMR spectroscopy.

Three polyvalent Streptomyces phages were used to isolate four Micromonospora species (M. carbonacea, M. chalcea, M. purpureochromogenes, and M. inositola) from mine-site rhizosphere soils in Western Australia. Streptomyces violascens was isolated using selective isolation techniques from the same soils. The Micromonspora spp. were examined for the...

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