Synchrotron light proves the effectiveness of two new drugs against sleeping sickness
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3D structure obtained from the XALOC beamline, showing the kinetoplast DNA with three drug molecules perfectly linked (in blue, pink and phosphorescent green).
A team led by researchers from the UPC has unveiled the mechanism of action of two drugs, FR60 and JNI18, that cure 100% of mice with sleeping sickness, also called African trypanosomiasis. Using synchrotron light at the ALBA Synchrotron, the researchers observed how these drugs stacked perfectly on the DNA of Trypanosoma brucei, the parasite that causes the disease, blocking and damaging it specifically. The result is that the parasite cannot reproduce and finally dies after 4-5 days. Scientists conclude that the drugs are effective potential treatments against sleeping sickness, which threatens over 55 million people in sub-Saharan Africa countries. These drugs remain patent-free to attract the interest of pharmaceutical laboratories.
Nov 22, 2017
This study was performed by scientists from the Universitat Politècnica de Catalunya (UPC), the Spanish National Research Council (CSIC) and the University of Glasgow. Its main objective was to prove the effectiveness of two new chemical compounds (FR60 and JNI18) for combating the parasite Trypanosoma brucei, which causes African trypanosomiasis, or sleeping sickness. The researchers also wished to unveil the mechanism of action of these compounds to help in the design of new trypanocidal drugs. After carrying out a variety of analyses and techniques, including X-ray diffraction at the ALBA Synchrotron (which resolves the molecular structure), the scientists demonstrated how these compounds block Trypanosoma’s exclusive kind of DNA: the kinetoplast. The key finding is that the drugs bind to the DNA helix, so its interaction with essential proteins for DNA maintenance is disrupted. “We observe that the two drugs can displace these essential proteins from kinetoplast DNA (replace them) and alter the DNA and the parasite’s normal functions,” explains Lourdes Campos, the researcher in charge of the UPC’s Crystallography, Structure and Function of Biological Macromolecules (MACROM) group. Twenty-four hours after the drug binds to the DNA, the kinetoplast is severely affected and disintegrates. Therefore, the parasite cannot reproduce and dies after 4-5 days. In conclusion, both drugs have proven to be effective at combating both chronic and severe sleeping sickness, in addition to the veterinary form of the illness that affects cattle in Africa and causes serious economic losses.
A long search to find the best drug
This study is a result of collaborative work between international research centres. First, the Institute of Medical Chemistry (IQM-CSIC) designed and synthesised the new candidate drugs. The University of Glasgow, the College of Medical, Veterinary and Life Sciences and the Wellcome Centre for Molecular Parasitology carried out the in vitro culture assays: they tested the parasite survival against the drugs, in order to select those most effective at killing the parasite. Finally, the UPC’s MACROM group was able to obtain crystals of the drug-DNA complexes with the two chosen compounds: DNA-FR60 and DNA-JNI18. The crystals were analysed at the XALOC beamline of the ALBA Synchrotron. Using X-ray diffraction, researchers solved the 3D structure of all these complexes. This technique offers a high level of resolution, allowing the interaction between drugs and DNA to be determined at atomic scale. The final results were deposited in the public Protein Data Bank and confirmed that the target for both drugs is the kinetoplast DNA: it is clearly observed how the drugs cover the DNA minor groove. These results and the other tests performed in Glasgow and at the Swiss Tropical and Public Health Institute leads Dr Campos to state that “both drugs are 100% curative in mice affected by African trypanosomiasis”.
The research article published by the researchers in Nucleic Acid Research (which has a high impact factor in its field) has been selected as a highlight by the Spanish Biophysics Society.
African trypanosomiasis or sleeping sickness: a neglected tropical disease
Like many other tropical illnesses, sleeping sickness is not under the focus of the pharmaceutical industry. The bite of an infected tsetse fly introduces the parasite into the blood of the victim and, if the infection remains untreated, the result is usually fatal. Today, sleeping sickness threatens over 55 million people in 36 sub-Saharan African countries. Diagnosis and treatment is complicated by fact that most of the affected population live in remote areas with limited access to health services in Africa’s poorest countries. The drugs currently used are extremely toxic and sometimes ineffective because resistance strains are frequent. New, safe and efficient drugs are therefore urgently needed. FR60 and JNI18 have not been patented to encourage all interested laboratories to study them and, if they are approved by the European Medicines Agency in the future, they can be distributed easily at low cost among the needy people.
This is not the first time that Lourdes Campos’ group, IQM-CSIC and the University of Glasgow have studied a tropical disease together. Three years ago, they proved the effectiveness of a drug against malaria (CD27) using the same technique in the ALBA Synchrotron. FR60 and JNI18 are derivatives of this malaria drug and, in fact, without knowledge of the structure of CD27, they could have not been synthesised. In Dr Campos’s words “we investigate neglected diseases precisely for this reason, because there are few studies on them. Pharmaceutical companies don’t pay attention to diseases of this kind because they are not profitable in business terms. That’s why academic laboratories must get involved to find new treatments. There is still a lot of work to be done in this field”.
A long search to find the best drug
This study is a result of collaborative work between international research centres. First, the Institute of Medical Chemistry (IQM-CSIC) designed and synthesised the new candidate drugs. The University of Glasgow, the College of Medical, Veterinary and Life Sciences and the Wellcome Centre for Molecular Parasitology carried out the in vitro culture assays: they tested the parasite survival against the drugs, in order to select those most effective at killing the parasite. Finally, the UPC’s MACROM group was able to obtain crystals of the drug-DNA complexes with the two chosen compounds: DNA-FR60 and DNA-JNI18. The crystals were analysed at the XALOC beamline of the ALBA Synchrotron. Using X-ray diffraction, researchers solved the 3D structure of all these complexes. This technique offers a high level of resolution, allowing the interaction between drugs and DNA to be determined at atomic scale. The final results were deposited in the public Protein Data Bank and confirmed that the target for both drugs is the kinetoplast DNA: it is clearly observed how the drugs cover the DNA minor groove. These results and the other tests performed in Glasgow and at the Swiss Tropical and Public Health Institute leads Dr Campos to state that “both drugs are 100% curative in mice affected by African trypanosomiasis”.
The research article published by the researchers in Nucleic Acid Research (which has a high impact factor in its field) has been selected as a highlight by the Spanish Biophysics Society.
African trypanosomiasis or sleeping sickness: a neglected tropical disease
Like many other tropical illnesses, sleeping sickness is not under the focus of the pharmaceutical industry. The bite of an infected tsetse fly introduces the parasite into the blood of the victim and, if the infection remains untreated, the result is usually fatal. Today, sleeping sickness threatens over 55 million people in 36 sub-Saharan African countries. Diagnosis and treatment is complicated by fact that most of the affected population live in remote areas with limited access to health services in Africa’s poorest countries. The drugs currently used are extremely toxic and sometimes ineffective because resistance strains are frequent. New, safe and efficient drugs are therefore urgently needed. FR60 and JNI18 have not been patented to encourage all interested laboratories to study them and, if they are approved by the European Medicines Agency in the future, they can be distributed easily at low cost among the needy people.
This is not the first time that Lourdes Campos’ group, IQM-CSIC and the University of Glasgow have studied a tropical disease together. Three years ago, they proved the effectiveness of a drug against malaria (CD27) using the same technique in the ALBA Synchrotron. FR60 and JNI18 are derivatives of this malaria drug and, in fact, without knowledge of the structure of CD27, they could have not been synthesised. In Dr Campos’s words “we investigate neglected diseases precisely for this reason, because there are few studies on them. Pharmaceutical companies don’t pay attention to diseases of this kind because they are not profitable in business terms. That’s why academic laboratories must get involved to find new treatments. There is still a lot of work to be done in this field”.