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ID Week 2 > LM 1.18: Antivirals I > Flashcards

LM 1.18: Antivirals I Flashcards

1
Q

what virus family is HIV?

A

retroviridae

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2
Q

how does HIV replicate?

A
  1. fusion of HIV to the host cell surface
  2. HIV RNA reverse transcriptase, integrase, and other viral proteins enter the host cell
  3. viral DNA is formed by reverse transcription
  4. viral DNA is transported across the nucleus and integrates into the host DNA
  5. new viral RNA is used as genomic RNA and to make viral proteins
  6. new viral RNA and proteins move to the cell surface and a new, immature, HIV forms
  7. the virus matures by protease releasing individual HIV proteins
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3
Q

what does HAART stand for?

A

highly active anti-retroviral therapy

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4
Q

what is HAART?

A

combination drugs to treat HIV/AIDS

a combination of drugs which act on different targets is required because HIV rapidly develops resistance if only one drug was given

  1. NRTI = nucleoside reverse transcriptase inhibitor
  2. NNRTI = non-nucleoside reverse transcriptase inhibitor
  3. protease inhibitors
  4. entry inhibitors
  5. integrase inhibitors
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5
Q

how do you determine is HAART is effective?

A

monitor viral genome load in blood by RT-PCR to determine if treatment is effective

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6
Q

which drugs are NRTIs?

A
  1. lamivudine (3TC)
  2. zidovudine (AZT/ZDV)
  3. abacavir (ABC)
  4. tenofovir (TDF)
  5. stavudine (d4t)
  6. zalcitavine (ddC)
  7. didanosine
  8. emtricitabine (FTC)
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7
Q

which drugs are NNRTIs?

A
  1. efavirenz
  2. nevirapine
  3. rilpivirine
  4. etavirine
  5. doravirine
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8
Q

which drugs are entry/fusion?

A
  1. maraviroc
  2. enfuvirtide
  3. ibalizumab
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9
Q

which drugs are integrase inhibitors?

A
  1. raltegravir
  2. dolutegravir
  3. elvitegravir
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10
Q

which drugs are protease inhibitors?

A
  1. saquinavir
  2. ritonavir
  3. fosamprenavir
  4. darunavir
  5. tipranavir
  6. atazanavir
  7. lopinavir
  8. nelfinavir
  9. indinavir
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11
Q

how do NRTIs work?

A

nucleoside analogs that mimic adenosine (TDF), guanosine (ABC), cytodine (3TC), or thymidine (AZT)

they are activated by phosphorylation and then incorporated into DNA which leads to chain termination

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12
Q

what are NRTIs used to treat?

A

they were the first HIV drugs developed

but some NRTI used to treat HBV infections (3TC, TDF)

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13
Q

how do NNRTIs work?

A

NNRTI act by directly binding to RT and allosterically inhibiting nucleoside binding

they bind to the same “NNRTI pocket”, so in general, virus strains resistant to one will be resistant to other NNRTIs

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14
Q

what’s the problem with using NNRTIs?

A

they bind to the same “NNRTI pocket”, so in general, virus strains resistant to one will be resistant to other NNRTIs

HIV develops resistance rapidly when used alone, combination use with HAART recommended

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15
Q

what are the side effects of NNRTIs?

A

common and severe side effects include: hepatotoxicity and potentially fatal rash

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16
Q

how do protease inhibitors work?

A

multiple steps of the HIV replication cycle depends on a viral-encoded protease, including viral polyprotein processing and infectious virion maturation

they are used in combination with other drugs to prevent rapid HIV mutation and resistance

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17
Q

what are some side effects of protease inhibitors?

A

common and severe side effects include: lipodystrophy (fat loss and abnormal fat accumulation) and may induce/worsen diabetes

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18
Q

how does enfuvirtide work?

A

it’s an entry and fusion inhibitor

it binds to HIV-1 glycoprotein (GP41) and prevents fusion

**not effective on HIV2

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19
Q

how does ibalizumab work?

A

it’s an entry and fusion inhibitor

it’s a humanized monoclonal antibody that binds CD4, the primary HIV receptor, and prevents HIV entry

It blocks HIV from binding to co-receptors CCR5/CXCR4 after binding to CD4

this is considered a “post-attachment inhibitor”

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20
Q

how does maraviroc work?

A

it binds to co-receptor CCR5 and prevents HIV entry

it only prevents virus strains that use CCR5

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21
Q

how do integrase inhibitors work?

A

the HIV replication cycle depends integration of RT-derived genomic DNA into the host cell chromosome

this step is accomplished by the viral integrase enzyme

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22
Q

what are the important HCV proteins?

A

STRUCTURAL
E1 and E2

NON-STRUCTURAL
P7
NS2
NS3
NS4A
NS4B
NS5A
NS5B
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23
Q

what is the function of NS3/4A in HCV?

A

they’re serine proteases

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24
Q

what is the function of NS5A in HCV?

A

viral replication or assembly

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25
Q

what is the function of NS5B in HCV?

A

it’s an RNA dependent RNA polymerase

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26
Q

which drug classes are used to inhibit HCV?

A
  1. direct acting antivirals (DAA)

2. non-DAA

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27
Q

which drugs are non-specific HCV inhibitors?

A
  1. ribavirin

2. interferon

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28
Q

which drugs are protease NS3/4A inhibitors used to treat HCV?

A
  1. paritaprevir
  2. simeprevir
  3. gravoprevir
  4. telaprevir
  5. boceprevir
  6. ritonavir
  7. glecaprevir
  8. voxillaprevir
29
Q

which drugs are NS5b polymerase inhibitors used to treat HCV?

A
  1. sofosbuvir

2. dasabuvir

30
Q

how does pregylated interferon work? which disease is it used for?

A

it’s a non-specific HCV drug

when attached to IFN it delays clearance of IFN from blood, effectively causing a 20-fold increase in the concentration of IFN

this is good because IFN has anti-viral properties!

31
Q

how does ribavirin work? which disease is it used for?

A

it’s a non-specific HCV drug

active against some RNA and DNA viruses

it’s a nucleoside (guanosine) analog that prevents RNA synthesis and viral mRNA capping, among other proposed mechanisms

32
Q

what are the side effects of ribavirin?

A

it’s a non-specific HCV drug

  1. birth defects and fetal death
  2. hemolytic anemia

**never use with zidovudine

33
Q

how do DAAs for HCV work?

A

DAA = direct acting antiviral

there are many DAAs available to target viral enzymes and replication

many are genotype specific

treatment options heavily dependent on virus genotype and prior exposure/treatment

genotypes 1a/1b are most prevalent in North America

usually, DAAs are used in combination with other DAAs of IFN/ribavirin

34
Q

which two major virus proteins are targets for anti-herpes drugs?

A
  1. thymidine kinase (TK)
  2. DNA polymerase

anti-herpesvirus drugs target both of these enzymes!!

35
Q

what does thymidine kinase do during herpesvirus replication?

A

it phosphorylates deoxythymidine

(Thy) Thy + ATP → TMP + ADP

then there are other enzymes that phosphorylate TMP to di- and tri-phosphates

TTP is a precursor for DNA synthesis

36
Q

what does DNA polymerase do during herpesvirus replication?

A

it’s the enzyme that incorporates nucleotide triphosphates (TTP, dGTP, dCTP and dATP) into a DNA copy of the template

37
Q

what are the two kinds of inhibitors of nucleic acid synthesis used to treat herpesvirus?

A
  1. chain terminators = are incorporated stopping DNA elongation
  2. competitive inhibitors = inhibit polymerase activity, but do not get incorporated

they are usually modified nucleosides = nucleic acid base + sugar w/o phosphate

they must be phosphorylated to nucleoside triphosphate to be incorporated into the growing DNA chain

they act as chain terminators and stop chain elongation

their sugar portion lacks a 3’-OH onto which incoming 5’-P esterifies to add the next base in 3’-5’ linkage so when they’re incorporated into a growing DNA chain, they cause premature termination because next base cannot be added

38
Q

does CMV encode a thymidine kinase?

A

no

39
Q

which drugs are anti-herpes drugs?

A
  1. Vidarabine
  2. Acyclovir
  3. Valacyclovir
  4. Penciclovir/famciclovir
  5. Triflurouridine and
    Idoxuridine
  6. Ganciclovir and Valganciclovir
  7. Cidofovir
  8. Foscarnet
  9. Fomivirsen
40
Q

what is vidarabine?

A

an anti-herpes drug that’s an adenosine analog

it’s considered the first antiviral drug to take advantage of the differences between viral and cellular TK and DNA polymerase

it had dramatic ability to prevent death from HSV encephalitis, which was previously, always fatal

it’s active against HSV-1, HSV-2, and VZV

41
Q

what is acyclovir?

A

anti-herpes drug that’s a guanosine analog

often effective in treating or preventing primary or reactivated oral or labial herpes in immunocompetent patients

in immunocompromised patients can be life-saving

it does NOT prevent recurrence of herpes and it only partially supresses viral shedding

it reduces HSV encephalitis by 50%

42
Q

which herpesvirus strains does acyclovir work best against?

A

HSV-1 = HSV-2 > VZV > CMV/HHV-6

43
Q

what’s the difference between valacyclovir and acyclovir?

A

both used to treat herpes

but valacyclovir has an oral bioavailability of about 55% which is 3-5 X greater oral bioavailability than acyclovir

but IV acyclovir generates higher peak levels than oral Valacyclovir, which may confer more potent activity

44
Q

what is a potential complication of acyclovir?

A

IV acyclovir generates higher peak levels which may increase the risk of renal toxicity due to precipitation of acyclovir crystals in the renal tubules

45
Q

how does penciclovir work?

A

herpesvirus drug

it’s a guanosine analogue

poor oral absorption so instead topical creams are used for herpes labialis

46
Q

how does famciclovir work?

A

herpesvirus drug

it’s a prodrug of penciclovir with improved oral bioavailability

it’s used to treat recurrent genital herpes and herpes zoster

also there is more rapid resolution of zoster-associated pain vs. acyclovir

47
Q

how do the drugs used to treat herpes keratitis work?

A

they’re nucleoside analogues of deoxyuridine which are similar enough to be incorporated into viral DNA during DNA synthesis

***they are toxic if administered systematically so you have to give them topically!!!

48
Q

which drugs are used to treat herpes keratitis?

A
  1. trifluridine opthalmic solution
  2. Idoxuridine opthalmic solution
  3. Vidarabine opthalmic ointment
49
Q

which drugs are used to treat CMV?

A
  1. ganciclovir
  2. valganciclovir
  3. cidofovir
  4. foscarnet
  5. fomivirsen
50
Q

what is cidofovir used to treat?

A

CMV

specifically CMV retinitis in AIDS patients

51
Q

when is foscarnet used?

A

it’s used to treat CMV but specifically acyclovir and ganciclovir-resistant infections

it’s also used to treat CMV retinitis

however it’s only used in life-threatening cases because it has a ton of bad side effects

52
Q

how does ganciclovir work?

A

drug used to treat CMV that’s a guanosine analog

it’s phosphorylated by the UL97 protein kinase of CMV

the phosphorylated drug competitively inhibits incorporation of dGTP into growing DNA chains by viral DNA polymerase terminating elongation of viral DNA

53
Q

when would you use valganciclovir?

A

it’s a CMV drug that’s super similar to ganciclovir but it just has better oral absorption

54
Q

how does foscarnet work?

A

it’s a CMV drug that’s a phosphonoacetic acid

it inhibits herpes polymerase by blocking its pyrophosphate binding site

55
Q

what are some of the side effects of foscarnet?

A
  1. myelosuppression
  2. teratogenicity
  3. renal toxicity
  4. hypocalcemia
  5. CNS effects

so because of all these bad side effects it’s only used in life-threatening cases

56
Q

how does fomivirsen work?

A

CMV drug that’s a 21-nt antisense oligonucleotide complementary to HCMV IE mRNA

it inhibits CMV replication by binding to the complementary sequence of the mRNA transcribed from the major IE gene of CMV

it inhibits the synthesis of proteins essential for production of infectious CMV

phosphorothioate coating of the oligonucleotide facilitates passage through the cell membrane

57
Q

what are are stages of viral replication?

A
  1. viral adsorption
  2. penetration
  3. uncoating
  4. early protein synthesis
  5. nucleic acid synthesis
  6. late protein synthesis
  7. packaging and assembly
  8. release
58
Q

what are the stages that antiviral drugs target to block viral replication?

A
  1. binding to free virus
  2. interference with adsorption
  3. inhibition of uncoating
  4. inhibition of transcription and replication
  5. interference with virus maturation/budding
59
Q

what are some of the challenges to antiviral drug use?

A
  1. viruses use host enzymes and machinery which eliminates those are potential antiviral targets
  2. it’s difficult to detect most viral infections in early stages
  3. viruses mutate readily
60
Q

what are the characteristics of the influenza virus?

A
  1. pleomorphic
  2. enveloped, segmented (-) sense ssRNA
  3. only types A and B infect humans
  4. they cause respiratory diseases
61
Q

what are the important proteins associated with the influenza virus?

A
  1. NA = surface protein
  2. HA = surface protein
  3. M2 = ion channel
  4. PB1, PB2, PA = RNA polymerase
  5. NP = nucleocapsid protein
62
Q

which drugs are antiviral influenza drugs?

A
  1. rimantadine and amantadine = M2 channel blockers

2. zanamivir and oseltamivir = NA inhibitors

63
Q

what do rimantadine and amantadine do?

A

influenza entry inhibitors because they block M2 channels

this prevents influx of H+ and prevents pH decrease in the endosome

this blocks the release of nucleocapsids from the matrix protein shell and ultimately prevents genome migration to the nucleus and viral replication

both drugs are used prophylactically

64
Q

what do zanamivir and oseltamivir do?

A

influenza NA inhibitors (only influenza A and B viruses)

they inhibit NA which is required for viral budding so they prevent the spread of the virus but do NOT prevent infection

so they block the release of virions

they’re currently no used because of viral mutants

must be administered during 48 hours of first symptoms

65
Q

what family is RSV?

A

RSV = respiratory syncytial virus

paramyxoviridae family = (-)ssRNA genome

same replication cycle as rabies

66
Q

what are the features of RSV?

A

forms syncytia! these are giant multinucleated cells during infection

clinical symptoms = low grade fever and wheezing!

RSV causes tissue damage in the lungs

67
Q

how does palivizumab work?

A

it’s a monoclonal antibody specific for RSV F-glycoprotein

this mAb binds to RSV fusion protein and inhibits virus entry into cell by preventing syncytia formation!

it’s used for prophylactiv treatment of infants <2 years with lun problems associated with chronic bronchopulmonary dysplasia or prematurity

68
Q

how does ribavirin work?

A

it’s a guanosine analog used to treat RSV

this guanosine analog is incorporated and causes mismatch and/or interferes with purine metabolism affecting GTP levels and prevents capping of mRNA

ribavirin is broad spectrum and inhibits many viruses! – for example, it’s used to treat HCV when combined with pegylated IFN drugs

it has to be administered very early in the infection

**may cause birth defects

69
Q

which drugs are used to treat RSV?

A
  1. palivizumab

2. ribavirin

ID Week 2 (20 decks)

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