Antiviral drugs (non-HIV)

Published on April 30, 2018   36 min

A selection of talks on Clinical Practice

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Hello I'm Megan Shaw. I'm from the Icahn School of medicine at Mount Sinai in New York. I'm going to be talking to you today about antiviral drugs, and specifically non-HIV antiviral drugs.
So why do we need antiviral drugs? Antiviral drugs can stop the infection, after it has started i.e., they can be used therapeutically; unlike vaccines which you use prophylactically. Also drugs are important for viral diseases where preventable vaccines are unavailable. Another reason is that drugs are important for viral diseases, where vaccines may not always afford protection. An example of this is the influenza virus, which the vaccine has to be changed every year, and sometimes there's a mismatch; or a new virus may emerge and there's not enough time to make the vaccine; and therefore antiviral drugs become very important. Finally drugs can be used as prophylaxis to prevent disease spread to close contact.
On this graph, there are illustrated the drugs that have been approved for viral diseases until, the present day. So right now we have approximately 90 drugs approved to treat nine viral diseases in humans. Some of these drugs I should note, include antibodies and immunoglobulin therapy - which I'm not going to cover in the lecture today. But you will note that these drugs are dominated by HIV drugs. So these take up the majority of the approved drugs that we have today. We have had a number of drugs approved recently for HCV, and this has dramatically changed the treatment of HCV patients. I will be covering this in detail today.
Why do we have so few non-HIV antiviral drugs?
Some of the reasons include the following. Firstly viruses only express a small number of proteins, this is particularly true of RNA viruses which are very small. Not all of these proteins can be inhibited by a compound - because normally a drug of a protein is one that has an enzymatic function; and a small virus may only encode one or maybe two of such proteins. Each virus has unique proteins, so drugs are normally very specific for that virus. So one has to question sometimes, is it worth it to go through the development process for such a rare disease? Drugs must be potent, and they must completely block virus growth, and they must also be safe, not adversely affect the host. Especially as drugs maybe given to healthy people for prophylaxis. Also with acute infections, the timing of drug administration is very important; as it has to be given early to be beneficial. This is because symptoms are often actually due to the immune response, so the virus may not even be replicated by the time the patient feels ill. It also relies on the availability of rapid diagnostic test to know which drug to administer. Finally the pharmaceutical industry has to consider potential market for the drug. They tend to focus on viral diseases that are easily diagnosed; cause chronic infections, so this means that there's long term use of the drug; and finally are widespread in developed countries, which would be able to afford the drug. So this probably explains why the majority of our drugs are against HIV and HCV.