Lecture 6 - AntiViral Flashcards
Nucleoside vs nucleotide?
Nucleoside = sugar + base
Nucleotide = sugar + base + phosphate
All antivirals are ____ - no action against latent virus
virustatic
What is the MOA of anti-herpes drugs?
inhibit viral DNA polymerase
Acyclovir
topical, PO, IV
Indications: effective against HSV >> VZV shortens duration of HSV if given early IV First line: herpes simplex encephalitis neonatal HSV severe HSV VZV infection
ADME: acyclic guanasine derivative metabolically activated by 3 phosphorylations (the first one done by viral thymidine kinase) acyclovir triphosphate = active form renal clearance
SE:
N/D/HA
Toxicities:
renal toxic, neurotoxic
Resistance:
viral thymidine kinase mutation
can be treated with agents not requiring viral phosphorylation like Foscarnet
What are the indications for acyclovir?
topical, PO, IV
Indications: effective against HSV >> VZV shortens duration of HSV if given early IV First line: herpes simplex encephalitis neonatal HSV severe HSV VZV infection
What is the ADME of acyclovir?
ADME: acyclic guanasine derivative metabolically activated by 3 phosphorylations (the first one done by viral thymidine kinase) acyclovir triphosphate = active form renal clearance
What are the SE and toxicities of acyclovir?
SE:
N/D/HA
Toxicities:
renal toxic, neurotoxic
What resistance is present with acyclovir?
Resistance:
viral thymidine kinase mutation
can be treated with agents not requiring viral phosphorylation like Foscarnet
What is the MOA of acyclovir?
inhibit viral DNA polymerase
needs to be activated by 3 phosphorylations fist - the first one being done by the virus thymidine kinase
CMV meds
anti-cytomegalovirus drugs:
ganciclovir
foscarnet
When are CMV infections common?
HIV and organ transplant pts
Ganciclovir
Indications:
CMV infections
treatment/prophylaxis for CMV post-transplantation
MOA:
inhibit viral DNA polymerase, but first it must be activated by 3 polymerizations, the first one done by CMV kinase
ADME:
acyclic guanosine analog (same as acyclovir)
requires 3 phosphorylations (similar to acyclovir)
first phosphorylation done by CMV kinase
SE: toxicity: myelosuppression (major)
What are the indications for ganciclovir?
Indications:
CMV infections
treatment/prophylaxis for CMV post-transplantation
What is the MOA of ganciclovir?
MOA:
inhibit viral DNA polymerase, but first it must be activated by 3 polymerizations, the first one done by CMV kinase
What are the SE/toxicities for ganciclovir?
SE: toxicity: myelosuppression (major)
What is the ADME for ganciclovir?
ADME:
acyclic guanosine analog (same as acyclovir)
requires 3 phosphorylations (similar to acyclovir)
first phosphorylation done by CMV kinase
Foscarnet
IV only
Indications:
CMV
useful in strains resistant to acyclovir
MOA:
inhibits viral DNA polymerase, RNA polymerase, HIV RT
- no activation required
useful in strains resistant to acyclovir
SE/toxicity:
renal toxicity
hyperphosatemia, hypokalemia/calcemia/magnesemia
What are the indications for foscarnet?
IV only
Indications:
CMV
useful in strains resistant to acyclovir
What is the MOA for foscarnet?
MOA:
inhibits viral DNA polymerase, RNA polymerase, HIV RT
- no activation required
useful in strains resistant to acyclovir
What are the SE and toxicities seen with foscarnet?
SE/toxicity:
renal toxicity
hyperphosatemia, hypokalemia/calcemia/magnesemia
Which influenza causes mass infection?
only influenza A
When must anti-influenza medications be given in order to effective?
quickly after onset of sxs (~48hours)
What agents are available for anti-influenza?
amantidine
oseltamivir (tamiflu)
zanamivir (relenza)
Oseltamivir
(tamiflu, oral)
same for zanamivir (relenza, inhalation)
Indications:
influenza A, quickly given within 48 hours of symptom onset (activity against influenza B too)
Zanamivir is useful against oseltamivir - resistant strains
MOA:
neuraminidase inhibitors
What are the indications for oseltamivir?
(tamiflu, oral)
same for zanamivir (relenza, inhalation)
Indications:
influenza A, quickly given within 48 hours of symptom onset (activity against influenza B too)
Zanamivir is useful against oseltamivir - resistant strains
What are the indications for Zanamivir?
Zanamivir is useful against oseltamivir - resistant strains
influenza A, quickly given within 48 hours of symptom onset (activity against influenza B too)
What is the MOA of oseltamivir and zanamivir?
neuraminidase inhibitors
Why is there so much resistance seen with HIV drugs?
retroviral replication is ERROR PRONE which means a lot of mutations which means more resistance
NRTIs
nucleoSIde reverse transcriptase inhibitors
Abacavir
Lamivudine/Emtricitabine
(not on drug list: Zidovudine/AZT)
What is the MOA of NRTIs?
resembles nucleoside competitive inhibitor of RT –incorporates into DNA
What resistance is seen with NRTIs?
mutations in viral RT
What toxicities are seen with NRTIs?
lactic acidosis with hepatic steatosis
D/t NRTI mediated inhibition of mitochondrial function –build up of triglycerides –> hepatic steatosis
Abacavir
NRTI
ADME:
guanosine analog
administered in combo with lamivudine (or emtricitabine)
MOA: nucleoside analog (guanosine) competitive inhibitor of RT –incorporates into DNA
unique toxicities:
myocardial infarction
(caution in CV disease)
hypersensitivity reactions associated with HLAb5701 (Can be fatal)
Resistance:
slow. requires 2-3 RT mutations
What is the MOA of abacavir?
NRTI
ADME:
guanosine analog
administered in combo with lamivudine (or emtricitabine)
MOA: nucleoside analog (guanosine) competitive inhibitor of RT –incorporates into DNA
What toxicities are seen with abacavir?
Unique toxicities:
myocardial infarction
(caution in CV disease)
hypersensitivity reactions associated with HLAb5701 (Can be fatal)
in addition to the overall class toxicity of lactic acidosis with hepatic steatosis
What resistance is seen with abacavir?
Resistance:
slow. requires 2-3 RT mutations
Lamivudine
NRTI
Emtricitabine is a fluorinated form of lamivudine –making it have a longer half life (once daily dosing)
MOA: nucleoside analog (cystine) competitive inhibitor of RT --incorporates into DNA
Indications:
HIV combo (administered with tenofovir called truvada)
HBV (inhibits HBV RT)
What are the indications for lamivudine/emtrictabine?
Indications:
HIV combo (administered with tenofovir called truvada)
HBV (inhibits HBV RT)
What is the difference between lamivudine and emtricitabine?
Emtricitabine is a fluorinated form of lamivudine –making it have a longer half life (once daily dosing)
What is the MOA of lamivudine/emtricitabine?
MOA: nucleoside analog (cystine) competitive inhibitor of RT --incorporates into DNA
NtRTIs
nucleoTide reverse transcriptase inhibitors
tenofovir
Tenofovir
NtRTI
ADME:
acyclic nucleoTide analog of adenosine
given as a pro-drug: disoproxil fumarate (DF) or alafenamide (AF)
MOA:
competitive inhibitor of HIV RT = chain termination after incorporation into DNA
Indication:
first line RTI therapy when combined with emtricitabine
Toxicities:
renal accumulation: tubular necrosis, renal failure, Fanconi’s syndrome (less with AF)
What is the MOA of tenofovir?
NtRTI
ADME:
acyclic nucleoTide analog of adenosine
given as a pro-drug: disoproxil fumarate (DF) or alafenamide (AF)
MOA:
competitive inhibitor of HIV RT = chain termination after incorporation into DNA
What is the indication for tenofovir?
Indication:
first line RTI therapy when combined with emtricitabine
What toxicities are seen with tenofovir?
Toxicities:
renal accumulation: tubular necrosis, renal failure, Fanconi’s syndrome (less with AF)
NNRTIs
non-nucleoside reverse transcriptase inhibitors
efavirenz
Efavirenz
NNRTI
MOA:
binds directly to HIV1 reverse transcriptase and inhibit RNA and DNA dependent DNA polymerase activity
no phosphorylation needed since it’s not a nucleoside
binding site of NNRTIs is distinct from that of NRTIs (allosteric)
Drug-drug interactions:
Extensive metabolism/induction via CYP3A4 pathway
Resistance: can occur rapidly with single mutation in RT
Toxicity: nightmares/psychiatric disturbances (at start of therapy, then resolve)
What is the MOA of efavirenz?
NNRTI
MOA:
binds directly to HIV1 reverse transcriptase and inhibit RNA and DNA dependent DNA polymerase activity
no phosphorylation needed since it’s not a nucleoside
binding site of NNRTIs is distinct from that of NRTIs (allosteric)
What drug drug interaction are present with efavirenz?
Drug-drug interactions:
Extensive metabolism/induction via CYP3A4 pathway
What toxicities are present with efavirenz?
Toxicity: nightmares/psychiatric disturbances (at start of therapy, then resolve)
What resistance is present with efavirenz?
Resistance: can occur rapidly with single mutation in RT
HIV protease inhibitors
Ritonavir
Darunavir
Atazanvir
ADME:
Pepitdomimetics
MOA:
Inhibits proteolytic cleavage of Gag and Gag-pol in HIV 1 and 2
Drug-drug interactions:
Metabolized by, inhibitors of CYP3A4
Toxicities as a class:
Redistribution and accumulation of body fat (lipodystrophy)
Increase triglycerides/LDL
Ritonavir
HIV Protease Inhibitor
Inhibitor of CYP3A4 — used with other PIs to increase their serum levels
Less frequent dosing (BOOSTER)
Taken with food
Toxicities:
Increase triglycerides/LDL
Elevated serum aminotransferase levels
Atazanavir
HIV protease inhibitor
Toxicities: Hyperbilirubinemia Rash Kidney stones Cholelithiasis
Only available as a fixed dose combo with ritonavir since ritonavir inhibits CYP3A4 and increases blood levels
Maraviroc
CCR5 receptor antagonist/Entry inhibitor
Not first line therapy
Binds selectively to CCR5 - one of the two co-receptors necessary for entrance of HIV into CD4+ cells
Enfuvirtide
Fusion inhibitors
Binds to gp41 subunit of the viral envelope glycoprotein, preventing the conformational changes required for the fusion of the viral and cellular membranes
NOT for HIV2
SubQ injection (peptide—long change)
Only for treatment experienced HIV pts with ongoing HIV replication
Dolutegravir
Integrase strand transfer inhibitors (INSTIs)
Inhibits viral DNA strang integration in host genome
Toxicities:
Hypersensitivity
Elevated liver enzymes with HCV/HBV co-infection
What is the latest recommendation for PEP?
Pre/pst exposure prophylaxis
Raltegravir/dolutegravir + TDF/emtricitabine for PEP
TDF/emtricitabine for pre-exposure