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Can a mosquito change the world?
Posted on May 18th, 2016 by Joanna Aldred in Chemistry
It is night, you are trying to sleep and you hear a mosquito in your bedroom. Can you sleep?
This is a story often told about how even very small actions can have a large influence. It is used to persuade the reluctant listener that it is worthwhile clearing litter from the beach/writing to your member of parliament/helping your neighbour/or whatever cause is being promoted.
The mosquito seems to be one of those small organisms that are capable of energizing the world’s press and forcing NGOs into action. The case of the Zika virus is the newest example of the power of the mosquito. In the past months the media has been full of pictures of mosquitoes and descriptions of the problems this virus is causing to pregnant mothers. The World Health Organization (WHO) has now declared this outbreak an emergency.
Beginning with its identification in 1947 in Uganda, there has been approximately 1 publication a year on the zika virus. Since an outbreak of this disease on Yap Island in the Pacific in 2009 (the first known outside Africa) the number of publications has risen rapidly, as you would expect in response to what is now seen as a major health threat; in comparison, research papers about the common cold average about 200 a year. Research into the disease, and understanding the mechanisms of the disease, is only the first step leading to the discovery of drugs that will help cure or prevent this disease. It is to be hoped that the interest and money now being diverted to the zika virus will quickly lead to finding a cure or a vaccination.
If a relatively unknown virus originally from a forest in Uganda can spread across the Americas and, if the media are to be believed, to most of the rest of the world; how many other, better known but neglected diseases are capable of doing the same? Should there be more research into these neglected diseases? And how do we treat them?
The WHO has a list of 17 neglected tropical diseases (NTDs) “a diverse group of communicable diseases that prevail in tropical and subtropical conditions” which would benefit, as the name suggests, from more attention. These include dengue, rabies, human African trypanosomiasis (sleeping sickness) and leprosy. The major factor which links these diseases is poverty; a fact that means research companies are less inclined to invest. This, despite the fact that over 1 billion people in 149 countries suffer from one or more NTD, with millions of others at risk, and the economic repercussions of these diseases can be just as damaging as their health effects.
A new review in Bioorganic & Medicinal Chemistry Letters looks at one possible, relatively low-cost route to finding drugs to tackle these neglected tropical diseases. This involves repurposing existing chemical matter as new drugs or new starting points for optimization. Due to the lack of financing, research on possible drugs for these NTDs is usually carried out not in pharmaceutical companies but in academia. Academic groups lack the finance of larger concerns so tend to concentrate on developing existing research.
There are several different approaches to using this existing research as the starting point for new drugs. This review categorises these various methods: drug repurposing; target repurposing; target class repurposing and lead repurposing and provides examples of when they have been effective.
Drug repurposing is one of the most cost-effective methods since this involves using an existing drug, which has been tested and whose doses are known. Eflornithine, developed as a cancer treatment, is now being used to combat sleeping sickness. Combining this with another drug nifurtimox, which was developed to combat Chagas disease, has proved even more effective. Not only is this a relatively cheap method but, since the testing has already been carried out, it is relatively quick.
All the approaches described in this paper make it more possible to find new drugs relatively quickly and cheaply. We can only hope for many successes.
It is night somewhere in the Americas, you are a pregnant woman trying to sleep. You hear a mosquito in your bedroom. Can you sleep? Unfortunately, I think the answer at the moment is probably “no”.
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