MICA: Modes of action and resistance mechanisms towards anti-trypanosomal benzoxaboroles

Lead Research Organisation: University of Glasgow
Department Name: College of Medical, Veterinary &Life Sci

Abstract

Human African trypanosomiasis (HAT), often known as sleeping sickness, is a disease found primarily in rural Africa. It is caused by tiny single celled parasites called trypanosomes. These organisms are transmitted by tsetse flies which suck human blood and can inject parasites while doing so. The parasites initially proliferate in blood but then invade the central nervous system. The presence of parasites proliferating in the brain causes a progressive breakdown in neurological functioning, including alterations in sleep-wake patterns which lend the disease its common name. Drugs that are currently available for HAT are unsatisfactory for a number of reasons. One compound, melarsoprol, is based on arsenic and is so toxic that one in every twenty people treated with the drug die as a result of its administration. Another compound, called eflornithine, has to be injected into veins through a drip several times a day for a fortnight (or a week if given in combination with another drug called nifurtimox (which itself is a potential cancer-causing agent!). New drugs are urgently needed and two compounds are currently in clinical trials. One, called fexinidazole, is being developed by the Drugs for Neglected Diseases initiative (DNDi) and is currently in phase II clinical trials. The second compound, now in Phase I trials is SCYX-7158, one of the benzoxaborole class of compound developed by DNDi in conjunction with Anacor and Scynexis. Whilst fexinidazole is what is known as a nitroheterocyclic compound, whose activity depends on its being activated by an enzyme found inside trypanosomes, little is known about how benzoxaboroles work. They are a very novel class of compound. What is clear, however, is that of the hundreds of variations on this theme that have been produced, they appear not to all work in the same way, based on the time it takes to kill parasites and some differences in the appearance of parasites targeted by these compounds. Here we propose to use a variety of state-of-the-art technologies to determine exactly how different members of the benzoxaborole class work. We will find enzymatic targets of these drugs which will then enable chemists to develop even more potent inhibitors. Moreover, we will also learn about mechanisms of resistance to the drugs which will allow us to classify them into groups where cross resistance is unlikely to occur. Our ultimate aim is to learn as much as possible about this class of compound with a view to fuelling the pipeline of anti-trypanosomal drug development during a period dedicated to the elimination and possibly even eradication of this fatal disease.

Technical Summary

Improvements in understanding how new chemical entities can be converted to effective drugs has underpinned development of new drugs for parasitic diseases, including human African trypanosomiasis. An effective series of compounds, the benzoxaborole class, was developed primarily through the implementation of pharmacokinetic and pharmacodynamic (PK/PD) standards. One of the series, SCYX-7158, has entered clinical trials. Less attention, however, was paid to mode of action against trypanosomes. Here we propose a systematic, multifaceted approach to understand the mode of action of the benzoxaborole series. This will be achieved by exploiting a sub-set of distinct members of the class that have demonstrated differential potency, time to kill and PK parameters. We will exploit several orthogonal approaches to answer the question of how these compounds interact with trypanosomes. To determine how the compounds interfere with cellular metabolism, each will be used over a range of concentrations and exposure times against bloodstream form trypanosomes, and metabolites extracted from lysates will be quantified to assess which pathways are impacted. Preliminary work suggests that SCYX-7158 perturbs S-adenosylmethionine metabolism, pointing to a methyltransferase target. The second powerful route to understanding drug mode of action involves selecting parasites for loss of function mutations, using RNA interference to elicit drug resistance. Again our preliminary data with selected compounds indicates that changes to cellular sumoylation and specific dehydrogenase enzymes stimulates resistance to the drugs. Finally we will also use a battery of microscopy based assays to determine alterations to cellular phenotype as cells die. Once data is collected across the series we will then use genetic approaches to validate the putative targets identified though these analyses.

Planned Impact

Essentially within this program of research we aim to identify modes of action and drug targets for the benzoxaborole class in Trypanosoma brucei, the causative agent of human African trypanosomiasis. The consortium lead by the Drugs for Neglected Diseases initiative (DNDi), including Scynexis and Anacor (the company who holds the IP on the benzoxaborole class) will benefit from the information provided in terms of leading their own synthetic chemistry programs in developing improved drugs for HAT. Given the same class has also provided candidates for clinical consideration for other conditions including Leishmaniasis, Chagas' disease, malaria and veterinary trypanosomiasis, the information we obtain on mode of action will also be of use in considering how other compounds in the series might work against other protozoan pathogens, as well as in a more broad context in understanding the full potential of these compounds. These benefits will emerge during and shortly after the tenure of the award.

The ultimate beneficiaries from this work will be the victims of sleeping sickness in Africa. Bringing new compounds forward to treat patients, particularly orally available compounds such as the benzoxaboroles, will be a major advance since current drugs are unsatisfactory given the need for dosing by injection, difficulties in availability and manufacture, cost and a risk of resistance. Medical practitioners involved in administering chemotherapy will benefit though improved dosing regiment compared to existing drugs. National Control Programs in sleeping sickness endemic areas will benefit from having safe, oral, optimized drugs for use in control campaigns. The World Health Organisation, who currently lead policy on treatment regimens for HAT and who are now implementing a program to eliminate HAT will equally benefit from having optimized compounds available.

Staff involved in the work will also in from close collaboration with Anacor, and also with the platforms in place in Dundee and Glasgow for drug development. The ability to communicate these findings, to use accurate statistical approaches and the appreciation of data driven projects are additional skills that the research staff will either gain or have reinforced.

Publications

10 25 50
 
Description Scottish Funding Council review of Research Pooling
Geographic Reach National 
Policy Influence Type Participation in a national consultation
URL https://www.universities-scotland.ac.uk/briefing-evidence/independent-review-scottish-funding-counci...
 
Description WHO guidelines for drug use against human African trypanosomiasis
Geographic Reach Africa 
Policy Influence Type Membership of a guideline committee
 
Description CIC The Tryp Chip
Amount £38,471 (GBP)
Organisation Medical Research Council (MRC) 
Sector Public
Country United Kingdom
Start 01/2018 
End 12/2020
 
Description GALVmed Drug resistance and cross-resistance in livestock trypanosomes.
Amount £117,482 (GBP)
Organisation GALVmed 
Sector Charity/Non Profit
Country United Kingdom
Start 04/2017 
End 06/2018
 
Description Wellcome Strategic Award Discovery of New Drug Candidate(s) for the Treatment of Human African Trypanosomiasis (HAT)
Amount £338,636 (GBP)
Funding ID 108517 
Organisation Wellcome Trust 
Sector Charity/Non Profit
Country United Kingdom
Start 01/2016 
End 12/2018
 
Description Wellcome Trust Strategic Award
Amount £239,423 (GBP)
Funding ID 108443/Z/15/Z 
Organisation Wellcome Trust 
Sector Charity/Non Profit
Country United Kingdom
Start 01/2016 
End 12/2020
 
Title Diagnostic biomarkers for African trypanosomiasis staging 
Description Metabolite profile that diagnoses patients with African trypanosomiasis and also stage 1 vs stage 2 disease 
Type Of Material Model of mechanisms or symptoms - human 
Year Produced 2016 
Provided To Others? Yes  
Impact Metabolomics characterisation of new biomarkers for human African trypanosomiasis diagnosis and staging 
URL http://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0005140
 
Description An integrated approach to tackling drug resistance in livestock trypanosomes 
Organisation University of Edinburgh
Department The Roslin Institute
Country United Kingdom 
Sector Academic/University 
PI Contribution University of Glasgow will test drug resistant parasites and seek mechanisms of resistance to veterinary trypanosomes (Barrett) and make mathematical models of drug resistance (Louise Matthews)
Collaborator Contribution Project only just started
Impact None to date
Start Year 2019
 
Description Colin Suckling: A new drug discovery pipeline for animal African trypanosomiasis 
Organisation University of Strathclyde
Department Strathclyde Institute of Pharmacy & Biomedical Sciences
Country United Kingdom 
Sector Academic/University 
PI Contribution Professor Colin Suckling is a partner on this grant and is generating new chemical entitities of the minor groove binder class in order for us to assess activity against veterinary trypanosomes
Collaborator Contribution Professor Suckling provides new chemical entities and intellectual input regarding structure activity relationships, also collating information from other sources to enrich this activity
Impact Collaboration between Suckling and Barrett has been ongoing in development of new drugs to treat parasitic diseases for over a decade. Suckling is a medicinal chemist, Barrett a Parasitologist, hence the synergy is around design and production of chemicals with activity against protozoa. Barrett tests compounds made by Suckling and together they seek new information to guide further development.
Start Year 2008
 
Description Combined research effort between University of Glasgow and University of Dundee and Anacor Pharmaceuticals 
Organisation Anacor Pharmaceuticals Inc.
Country United States 
Sector Private 
PI Contribution Anacor provide chemicals to screen. We use to determine effects on parastic trypanosomes
Collaborator Contribution Anacor provide compounds for us to screen. It is not correct to demand a value of the inkind contribution.
Impact None to date
Start Year 2014
 
Description Combined research effort between University of Glasgow and University of Dundee and Anacor Pharmaceuticals 
Organisation University of Dundee
Department College of Life Sciences
Country United Kingdom 
Sector Academic/University 
PI Contribution This grant is a collaborative grant between the University of Glasgow and University of Dundee
Collaborator Contribution The Dundee team and we, are using orthologous and complementary approaches to investigate mode of action of drugs against trypanosomes
Impact None to date
Start Year 2015
 
Description Drugs for Neglected Diseases initiative Mode of Action network 
Organisation Drugs for Neglected Diseases initiative (DNDi)
Country Switzerland 
Sector Charity/Non Profit 
PI Contribution DNDi have established a network of researchers interested in elucidating drug mode of action against Kinetoplastid protozoa and we are part of that network (including University of Glasgow, University of York, University of Dundee and University of Antwerp
Collaborator Contribution In Glasgow we are using our metabolomics platform to seek modes of action of new chemical entities in the DNDi portfolio for Leishmaniasis
Impact Identification of mode of action of benzoxaborole drugs in trypanosomiasis (see publications: Wall, R et al. (2018). & Begolo et al. (2018)
Start Year 2018
 
Description GalvMed Boerhinger Ingelheim development of benzoxaboroles for animal African trypanosomiasis 
Organisation Boehringer Ingelheim
Country Germany 
Sector Private 
PI Contribution We have continued working on mode of action and resistance mechanisms of the benzoxaboroles considered for clinical veterinary development by BI.
Collaborator Contribution We identified a serine carboxypeptidase involved in activating prodrugs in T. brucei and T. congolense. The compounds target the CPSF3 protein. Resistance emerges either when the peptidase genes are lost, or else when the target (CPSF3) gene copy number is increased.
Impact Drug under development.
Start Year 2019
 
Description Glavmed - A new drug discovery pipeline for animal African trypanosomiasis 
Organisation GALVmed
Country United Kingdom 
Sector Charity/Non Profit 
PI Contribution We are testing a new series of compounds for trypanocidal activity with a long term aspiration of passing this on to Galvmed for clinical development as veterinary trypanocides. We are also creating new culture media to assist in drug screening against veterinary trypanosomes. Also new genomic and metabolomic information to assist in culture medium development and also identify novel drug targets.
Collaborator Contribution Galvmed provide financial assistance to our IPA award to the tune of 160,000 GBP. They also proovide some chemicals to test (cross resistance studies) and parasite strains for analysis
Impact We have developed new, improved culture media for Trypanosoma congolense. We have (through Professor Suckling) identified a series of compounds with high potency against T. confolense and T. vivax, now awaiting further toxicity and PK testing for consideration towards further development.
Start Year 2012
 
Description Liam Morrison: A new drug discovery pipeline for animal African trypanosomiasis 
Organisation University of Edinburgh
Department The Roslin Institute
Country United Kingdom 
Sector Academic/University 
PI Contribution Liam Morrison is a veterinary Parasitologist with expertise in the biology of veterinary trypanosomes. He is adding expertise in cultivation of trypanosomes of veterinary significance and understanding their genomic and metabolomic profiles with a view to drug discovery
Collaborator Contribution Dr Morrison is adding expertise in cultivation of trypanosomes of veterinary significance and understanding their genomic and metabolomic profiles with a view to drug discovery
Impact We have recently developed a new medium for the cultivation of Trypanosoma congolense to assist in drug screening. New genomic information is also assisting identification of drug targets
Start Year 2008
 
Description Lecture to School on Neglected Tropical Diseases 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Schools
Results and Impact A lecture to Lomond School in Helensburgh (20th Feb 2017)
Year(s) Of Engagement Activity 2017
 
Description Presentation on Neglected Tropical Disease 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Schools
Results and Impact High School of Glasgow talk
Year(s) Of Engagement Activity 2017
 
Description Prison Visit 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Other audiences
Results and Impact I presented two lectures about Neglected Tropical Diseases and parasitism to Prisoners at Low Moss Prison (9 March 2017)
Year(s) Of Engagement Activity 2017
URL https://www.st-andrews.ac.uk/news/archive/2016/title,680046,en.php
 
Description Public Engagement talk to Schools 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Schools
Results and Impact Talk to local schools around Durham during British Society of Parasitology Meeting (14th Sep 2016)
Year(s) Of Engagement Activity 2016
URL http://bsp.uk.net/2016/10/10/blog-report-septembers-autumn-symposium/
 
Description School visit 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact I lectured on Neglected Tropical Diseases as the Dallachy lecture at the Glasgow Academy, to current and former pupil;s, teachers and parents
Year(s) Of Engagement Activity 2017
URL https://www.facebook.com/glasgowacademy/posts/2288676024604646
 
Description Schools talk on Neglected Tropical Diseases 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Schools
Results and Impact Lecture on Neglected Tropical Diseases to High School of Glasgow (28 Oct 2017)
Year(s) Of Engagement Activity 2016
 
Description The Conversation - Leishmaniasis in Syria 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Online article discussing Leishmaniasis with respect to refugees. Accessed nearly 1 million times within a week of its appearance.
Year(s) Of Engagement Activity 2016
URL https://theconversation.com/explainer-what-is-the-flesh-eating-disease-thats-spreading-across-syria-...
 
Description lecture on Drug resistance and development in parasitic disease 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Undergraduate students
Results and Impact Lecture to the Glasgow University Medical Infection and Immunobiology Society. Glasgow. 5th Nov 2016
Year(s) Of Engagement Activity 2016
URL https://www.facebook.com/GUMIIC/?ref=page_internal