Antivirals Flashcards
What is required by a good antiviral?
- High therapeutic index
- Easy to administer
- Easy to store
- Cheap to produce
- Broad scale use
What is a high therapeutic index?
This is an antiviral which has a high antiviral activity but low cellular toxicity
What is helping us to develop new anti-viral drugs?
Rational drug design
3D structures of molecules
Crystal structures
What are the nucleoside analogue chain terminators you must know?
- HSV: Ganciclovir and acyclovir
- HCV: Ribavarin
- HIV: AZT: Azidothymidine
What nucleoside analogues can be used to treat HSV infection?
Acyclovir and ganciclovir
Acyclovir is a?
Prodrug
Acyclovir action?
It is phosphorylated by the viral thymidine kinase to become acyclovirir-monophosphate
It is then phosphorylated into acycloviur-triphosphate by cellular kinases and can act as a chain terminator during DNA synthesis
How does acyclovir prevent cellular toxicity?
It has a higher affinity for viral polymerase than for host polymerase
What is the main difference between ganciclovir and acylclovir?
Ganciclovir has an additional hydroxymethyl group
Ganciclovir must be injected and cannot be applied topically like acyclovir
Why is acyclovir easier to administer?
Topical application is possible
What is the nucleoside analogue used to treat HCV hepatitis C infection?
Ribavirin which is a chain terminator
It is a guanosine analogue
What nucleoside analogue can be used for HIV treatment?
Azidothymidine = AZT
Azidothymidine is what class of drug?
NRTI
What is an NRTI?
Nucleoside reverse transcriptase inhibitor
How can resistance to AZT develop?
Via mutations in the gene encoding the reverse transcriptase
What therapy is used in HIV treatment?
HAART
What does HAART stand for?
Highly active anti retroviral therapy
What does HAART therapy involve?
It involves the use of multiple antivirals which when used in combination should reduce resistance developing
What is used in combination therapy for HIV?
Integrase inhibitors Protease inhibitors NRTI nucleoside RT inhibitors NNRTI non-nucleoside RT inhibitors Entry inhibitors Anti-fusion class of drugs
What is an example of a HIV entry inhibitor?
Maraviroc
What does Maraviroc do?
It binds to CCR5 and prevents HIV binding
What homozygous mutation makes individuals resistant to HIV?
CCR5-delta 32
The first man cured of HIV?
Timothy Brown- 2007
How was Timothy Brown cured of HIV?
He has leukaemia and was given a haematopoietic stem cell transplant from a donor who was homozygous for the CCR5 delta 32 mutation
Why are so many drugs against HIV required?
So they can be used in combination to reduce the likelihood that resistance will develop
What is the name of the HIV combination therapy?
HAART
HAART stands for?
Highly active anti retroviral therapy
The CCR5 delta 32 mutation is most common in?
Caucasians
Drugs against rhinovirus include?
Pocket factor lipid mimics
IMP-1088
Which drugs target the host?
Maraviroc targeting host CCR5
Imp-1088 targeting the host N-myrostoyltransferase
Which drug can mimic the pocket factor lipid?
Pleconaril
What is the host N-myristoyltransferase used for?
To N’ myristoylate the VP0. This allows assembly of the capsid
What drugs can be used against HCV?
- Ribaravin nucleoside chain terminator
- Drugs targeting NS5B polymerase
- Anti-protease drugs targeting NS3/4A
- NS5A inhibitors
NS5A is involved in?
Formation of the membranous web
Ribaravin is what?
A nucleoside chain terminator, guanosine analogue
What drugs can target the NS5B polymerase?
Sofosbuvir
What drugs can target the NS3/4A?
Telaprevir
Sofosbuvir targets?
The NS5B polymerase of HCV
Telaprevir targets?
the NS3/4A protease of HCV
Which drug targets the M2 ion channel of influenza?
Amantadine
Which drugs target the neuraminidase?
Tamiflu and Relenza
Tamiflu can also be known as?
Oseltamivir
Relenza can also be known as?
Zanamivir
Resistance against amantadine has been seen in?
In H5N1, due to overuse in poultry industry
In the pH1N1 of 2009, probably do to overuse in pig farming
Tamiflu/oseltamivir action?
It has a hydrophobic group which binds to the hydrophobic pocket
Relenza/zanamivir action?
Sialic-guanadine analogue
Blocks neuraminidase
What helped to create these two drugs?
Crystalline structure of neuraminidase allowed for rational drug design
Tamiflu was developed by?
Roche
Relenza was developed by?
GSK
Why is tamiflu used more frequently than relenza?
Relenza has to be inhaled using an inhalation device which the elderly often find difficult to use, it is also more difficult to store
Why is tamiflu better than amantadine?
Effective against influenza A and B
Amantadine is not effective against?
Influenza B
Which anti-influenza drug does the government tend to stockpile and why?
Tamiflu as it is in a pill form which makes it easy to store
The government will require something to give people in the event of a pandemic as vaccines usually take around 6 months to develop
Cochrane researchers did what?
They investigated the efficacy of Tamiflu and Relenza and wanted to evaluate whether stockpiling the drugs was worthwhile
Cochrane results?
4% associated nausea and vomiting
Reduces infection by 17 hours in adults and 29 hours in children
Revisiting the 2009 pandemic these drugs reduced death associated with infection by 50% when administered within 48 hours of developing symptoms
Tamiflu resistance has been observed in?
H5N1
Spontaneous tamiflu resistance was observed where?
H1N1
Norway
How did spontaneous tamiflu resistance develop?
Due to natural drift in gene encoding neuraminidase in response to the selection pressure imposed by the immune system
What replaced seasonal H1N1?
Pandemic H1N1 from the 2009 pandmeic
What mutation caused spontaneous tamiflu resistance in seasonal H1N1?
H274Y mutation
Which antivirals can target the polymerase of influenza?
Baloxavir
Favipiravir
Baloxavir targets?
PA endonuclease
Favipiravir targets?
PB1 polymerase
What mutation caused the spontaneous tamiflu resistance of seasonal H1N1?
H274Y
H274Y is from?
Histidine to tyrosine
E627K mutation is?
From glutamate to lysine
Allowing the shorter ANP32A to be used
H274Y mutation is from?
Histidine to tyrosine
H274Y mutation conferred resistance to?
Tamiflu
What are monoclonal antibodies?
Identical antibodies are antibodies produce by identical immune cells which are clones of a unique parent cell
What are monoclonal antibodies?
Identical antibodies which are produced by identical cells which are clones of a unique parent cell
What is passive immunotherapy?
Giving antibodies from an individual that was infected and survived to another individual
What was the first method of producing monoclonal antibodies?
Murine hybridoma
Hybridoma?
Fusing an antibody producing B cell line with a myeloma cell line
What was the issue with this method?
The humans injected with murine antibodies would produce antibodies against these as they were recognised as foreign
How was this circumenvented?
Chimeric antibodies and humanised antibodies
What are chimeric antibodies?
These are antibodies in which the the murine antibody constant regions have been replaced by human antibody constant regions
What are humanised antibodies?
These are antibodies in which only the CDR- complementary determining regions which bind the epitopes are of murine origin
What is an example of a humanised antibody?
Palivizumab
Palivizumab is given to?
Premature babies, children with special conditions to protect them against RSV infection
Palivizumab is given to children to protect them from developing?
Bronchiolitis
What does Palivizumab target?
F protein of RSV
Humanised antibodies used in the Ebola outbreak?
Cocktail of 3 humanised monoclonal antibodies targeting 3 epitopes of the Ebola glycoprotein
How was this humanised monoclonal antibody cocktail made?
It was produced in GM tobacco plants
What was this Ebola therapy known as?
Zmapp therapy
How can fully humanised antibodies be made?
GM mice
Or direct immortalisation of human B cells
Using GM mice?
Using GM mice which contain human genes encoding antibodies rather than mice genes… then fusion to a myeloma cell line
Direct immortalisation of human B cells?
Fusing B cell producing the desired antibodies with e.g. EBV
What is the modern method of monoclonal antibody production?
Phage display
Who came up with phage display?
Greg Winter