Anti-Viral Therapy, September 8th Flashcards
Generally, how do Anti-virals work?
Some work by blocking the Ligand-Receptor binding
Done by either binding to the Ligand or the Receptor
Where can drugs interfere with the Viral Lifecycle
- Membrane Fusion
- DNA/RNA Replication
- Integrating DNA into Genome
- Translating Viral RNA to Proteins (Not always)
- Assembly/Maturation of Virions
- Escape from Host Cell
What diseases is Aciclovir effective against?
Herpes Simplex 1/2
Herpes Zoster
What is the composition of Aciclovir?
Guanosine Analogue (Acyclo-Guanosine) Partial Nucleoside Analogue
What is the MOA of Aciclovir?
- Converted by Viral Thymidine Kinase to Monophosphate Acyclo-GMP
- Converted to Triphosphate using a Cellular Enzyme
- Inhibits action of Viral DNAP by terminating chains
- High Therapeutic Ratio (Viral TK is 3000x more effective at converting A-G to Monophosphate, and Viral DNAP is better at incorporating Triphosphate into Growing DNA chain than Cellular DNAP)
How is Aciclovir/Valaciclovir administered?
Topically (To Cold Sores/Eyes)
Orally
IV
What are the main side effects of Aciclovir/Valaciclovir?
Psychiatric (Cotard’s Syndrome)
Toxicity in overdose (Lethargy, Confusion, Myoclonus)
How does Valaciclovir compare to Acyclovir?
Valaciclovir is Acyclovir that is ESTER-LINKED to Valine
Thus, Greater Oral Bioavailability
Why do viruses grow resistant to Aciclovir/Valaciclovir
Mutation of Viral Thymidine Kinase/DNAP
What is Idoxuridine?
NucleoSide Analogue
Modified form of Deoxyuridine containing Iodine
When is Idoxuridine used?
Topically for Herpes Keratitis
Too toxic for Systemic Use
What can Ganciclovir and Valganciclovir kill?
CMV
What is Ganciclovir made up of?
Synthetic Analogue of Deoxyguanine
What is the MOA of Ganciclovir?
- Phosphorylated to Monophosphate by CMV Thymidine Kinase
- Then made into Triphosphate by Cellular Kinases
- Inhibits Viral DNAP more than Cell DNAP
What is Valganciclovir compared to Ganciclovir?
Valganciclovir is a VALINE Ester with Greater Oral Bioavailability
What are the main side effects of Val/Ganciclovir
BM Suppression
What is Foscarnet?
Pyrophosphate Analogue
What is the MOA of Foscarnet?
Blocks Viral DNAP
What is Foscarnet used for?
Herpes Simplex Virus 1/2
Herpes Zoster
CMV (Especially Retinitis as an Intravitreous Injection, it can also be as an IV injection)
What are the main side effects of Foscarnet?
- Nephrotoxicity
- Electrolyte Disturbances (CaMg)
- Genital Ulceration
- CNS issues (Parasthesia, Irritability, Hallucinations)
What is Cidofovir used against?
DNA Viruses
- Herpes
- Papilloma
- Adenoviruses
- Poxviruses
- MOSTLY CMV
What is the MOA of Cidofovir?
Blocks Viral DNAP
What are the Adverse effects of Cidofovir?
- GI
- Haematological
- Iritis
- Headache
- Weakness
- Hair Loss
What is the MOA of Trifluridine?
Nucleoside Analogue from modified Deoxyuridine
What does Trifluridine kill?
Herpes Simplex
Zoster Keratitis
What are the adverse effects of Trifluridine?
Burning
Stinging Oedema
What is the MOA of Vidarabine?
Adenosine Analogue with Different sugar needing Triple Phosphorylation
What is Vidarabine used for?
Herpes Simplex
Herpes Zoster
What are the adverse effects of Vidarabine?
GI
Leukopenia
Thrombocytopenia
What drugs are generally effective against Retroviruses?
Reverse Transcriptase Inhibitors
What are the different types/analogues of RTI
Nucleoside and Nucleotide Analogues
What is the function of the NRTI analogues?
They inhibit Reverse Transcriptase by incorporating themselves into the growing DNA chain
This stops a linkage to the subsequent base
What are NucleoSide analogues?
They are molecules with a Ribose sugar and Base
Requires Three Phosphorylations to incorporate it
What are examples of NucleoSide analogues?
Lamivudine (Hep B)
Abacovir and Emtricitabine (first line)
Zidovudine (second line)
What are the side effects of Lamivudine?
Nausea Fatigue Headaches Diarrhoea Cough Pro-inflammatory response Autoimmunity
What are examples of NucleoTide analogues?
Tenofovir (HepB) and Adefovir
What are the side effects of Tenofovir?
Renal Insufficiency
Fanconi syndrome
What is Fanconi Syndrome?
Condition where normally absorbed products are excreted in urine
What is the MOA of NNRTIs?
They bind to RT away from the active site
Hampering its effect via distortion
What are the first-line choices of NNRTIs?
Efavirenz and Rilpivirine
What are the other less favourable NNRTIs?
Etravirine (Can cause CNS toxicity) and Doravirine
Nevirapine has more serious effects
What is the MOA of PIs?
Bind to Viral Proteases responsible for the viral precursor proteins that usually make up Virions
What are the main PIs?
Darunavir and Ritonavir
What suffix underlies all Integrase Inhibitor drugs?
-tegraVir
What suffix underlies most NNRTI drugs?
-INE or -VIRINE except Efavirenz
What suffix underlies most HCV PI drugs?
-preVir
What suffix underlies most NS5A inhibitor drugs?
-asVir
What suffix underlies most NS5B drugs?
-buVir
What suffix underlies most NRTI drugs?
-INE except Abacavir
What two drugs make up Truvada?
Tenofovir and Emtricitabine
What is the MOA of Integrase Inhibitors?
Inhibits Integrase which usually mediates integration of the HIV DNA (made by Reverse transcription) into the host genome
What are some examples of Integrase Inhibitors?
Raltegravir
Dolutegravir
Bictegravir
What is the MOA of Fusion Inhibitors?
Blocking GP41 on the surface of HIV Virions
GP41 usually mediates fusion between HIV envelope and Cell membrane?
What is an example of Fusion Inhibitors
Enfuvirtide
What is the MOA of Entry Inhibitors?
Blocking CCR5 on the Cell surface
Together with CD4 can enable GP120 to bind to HIV and allow Cellular entry
What is an example of Entry Inhibitors?
Maraviroc
What is the usual combination of Anti-retroviral therapies?
Two NRTI + something else
- Tenofovir + Emtricitabine
- Abacovir + Lamivudine
Either of these PLUS a Third
- *3. Integrase Inhibitor (Raltegravir)
4. Protease Inhibitor (Darunavir)
5. NNRTI (Doravirine, Rilpivirine
For Anti-retroviral therapy, what do you use if you cannot use Tenofovir or Abacovir?
Usually a combination of:
- Integrase + Protease
- Integrase + Lamivudine
- Boosted Protease + Lamivudine
When is PrEP given?
To people with sexual practices that could expose them to HIV
Truvada into a single daily pill
What do you do during a Post-exposure to body fluids/needlestick injury?
Wash with antiseptic/fluid on part
Truvada combo + Dolutegravir/Raltegravir for TWENTY EIGHT DAYS
What is Ribavirin?
Guanosine Analogue
What can Ribavirin do?
Inhibits Viral RNA-dependent RNAP
Incorporates to new RNA chain and terminates it
What is Ribavirin effective against?
Hepatitic C Viral Haemorrhagic Fever RSV Flu (Sometimes) Herpes (Mystery but true)
What are the adverse effects of Ribavirin?
Haemolytic Anaemia
BM Suppression
Psychiatric effects (Depression)
Cough
What are the main classes of drugs to treat Influenza?
- Neuraminidase Inhibitors
- M2 Inhibitors
- Ribavirin
What does Neuraminidase do and how do Neuraminidase Inhibitors stop this?
- Viral Neuominidase cleaves Sialic Acid from Glycoprotein
- This will release Virions from the host
- Virions will stop aggregating
- Reduction of inactivation of Virions by Host mucus
- NI will stop all of this lol
What are examples of Neuraminidase Inhibitors?
OseltAMIVIR
ZanAMIVIR
What is the suffix that underlies Neuraminidase inhibitors
-AMIVIR
What is the MOA of M2 Inhibitors?
Inhibits M2 protein of the Virus from decreasing H+ influx
This will STOP uncoating/recoating
What are the main drugs of the M2 Inhibitor class?
Amantidine
Rimantidine (Less neuro side effects)
What is the suffix that underlies M2 inhibitors?
-TIDINE
What drugs do we usually use to treat Hepatitis C?
Ribavirin Pegylated IFN (Though usually B)
What is Pegylated IFN?
Alpha or Beta
Cytokines enhancing immune response
Pegylated so they are linked to Polyethylene-Glycol to prolong Half Life
Given by Injection
What are the side effects of Pegylated IFN?
Malaise
Fever
What are the new Treatments for Hepatitis C?
Direct Acting Agents (DAAs) ------------------------------- Protease Inhibitors NS (Non-structural) inhibitors - NS5A, NS5B
Give examples for Protease Inhibitors against Hepatitis C
Glecaprevir
Grazoprevir
Tenofovir (Not active against Hep C Protease but boosts the drugs via blocking metabolism)
What is the function of Protease inhibitors?
Inhibition of Viral NS3/4A serine protease
What is the function of NS5A inhibitors?
Inhibits NS5A which is a viral protein promoting Assembly
Give examples of NS5A inhibitor drugs
Daclatasvir
Elbeasvir
Ledipasvir
What is the function of NS5B inhibitors?
Inhibits NS5B which is a viral RNA-dependent RNA polymerase
Give examples of NS5B inhibitors
Sofosbuvir (NucleoT/Side analogue)
Dasabuvir (Non-NucleoT/Side analogue)
Can Hepatitis C be cured?
Yes
It is an RNA virus so it cannot integrate itself into the genome
What is SVR?
Relating to Hep C, Cure
After Antiretroviral therapy, it is defined as the presence of no HCV RNA in the blood after 6 months
When do we typically give Ribavirin for Hep C cases?
When first line fails
How many different genotypes of Hep C are there?
6 (1 and 3 are the most common)
What is the main disadvantage of DAA
Expensive and takes a 12 week course
When considering elimination therapy for Hep C, what must you consider?
- Liver damage? (Cirrhosis/Fibrosis/Carcinoma)
- Transplant or Consideration?
- Manifestations OUTSIDE Liver (Cryoglobulinemia, Glomulonephritis)
- Positive for HepB/HIV
- Alcohol/Recreational Drugs
- Which Genotype
- Previous failed treatment with other drugs?
What types of drug types are commonly used to treat against Hep B?
RTIs (Lamivudine and Tenofovir)
Interferon (Peg IFN)
What is Hepatitis B?
Hepadnavirus: DNA virus using RT to integrate its genome into host cell cycles
What is the big issue regarding Hep B for relapsing?
Patients with both Hep B and C whilst being treated for C may cause relapsing of Hep B
How is RSV usually treated?
Palivizumab: mAb against RSV Fusion glycoprotein
Ribavirine via inhalation
How is Ebola usually treated?
mAb blocking the docking
How is Coronavirus generally treated?
Remdesavir: Inhibitor of RNA-dependent RNAP