Antiviral Agents and Mechanisms
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Questions and Answers

What is a common major adverse effect associated with nucleoside and nucleotide reverse transcriptase inhibitors (NRTIs)?

  • Peripheral neuropathy (correct)
  • Gastrointestinal disturbances
  • Hemolytic anemia
  • Liver toxicity

    • Which class of antiviral drugs is known to primarily inhibit the reverse transcriptase enzyme?

  • Protease inhibitors
  • Non-nucleoside reverse transcriptase inhibitors (NNRTIs)
  • Nucleoside and nucleotide reverse transcriptase inhibitors (NRTIs) (correct)
  • Integrase strand transfer inhibitors

    • How might efavirenz, a non-nucleoside reverse transcriptase inhibitor, interact with drugs cleared by the CYP2B6 enzyme?

  • Decrease their effectiveness
  • Enhance their metabolism
  • Increase their clearance
  • Cause increased blood levels of these drugs (correct)

    • What is the primary mechanism by which direct-acting antivirals (DAAs) target hepatitis C virus (HCV)?

    <p>Inhibit RNA replication</p> Signup and view all the answers

    Which of the following strategies is NOT typically used in the treatment of HCV?

    <p>Targeting cell membranes</p> Signup and view all the answers

    Which of the following is true regarding the effect of antiretroviral therapy on HIV infection?

    <p>It prolongs life expectancy</p> Signup and view all the answers

    What is a potential side effect of protease inhibitors?

    <p>Insulin resistance</p> Signup and view all the answers

    Which of the following accurately describes a feature of antiviral drugs?

    <p>They selectively inhibit viral processes.</p> Signup and view all the answers

    Which side effect is commonly associated with the use of Efavirenz?

    <p>Skin rash</p> Signup and view all the answers

    What is the primary mechanism of action of NS5A inhibitors in HCV treatment?

    <p>Inhibit viral assembly</p> Signup and view all the answers

    Which is a significant drug-drug interaction associated with Atazanavir?

    <p>Metabolized by CYP3A4</p> Signup and view all the answers

    Which of the following antiviral medications is a guanosine analogue and is used for hepatic viral infections?

    <p>Ribavirin</p> Signup and view all the answers

    Which treatment strategy provides the best therapeutic outcome for Hepatitis C?

    <p>Direct-acting antivirals (DAAs)</p> Signup and view all the answers

    Which side effect is noted with the use of Zidovudine?

    <p>Lactic acidosis</p> Signup and view all the answers

    What distinguishes baloxavir from traditional antivirals?

    <p>It inhibits endonuclease activity</p> Signup and view all the answers

    In the treatment of HCV, which of the following combinations is considered optimal?

    <p>Sofosbuvir + Velpatasvir</p> Signup and view all the answers

    Maraviroc is effective only in which patient population?

    <p>Patients infected with the R5 strain</p> Signup and view all the answers

    Which direct-acting antiviral inhibit both NS3 and NS4A proteins in HCV?

    <p>Glecaprevir</p> Signup and view all the answers

    Which of the following regarding Acyclovir is true?

    <p>It is a DNA polymerase inhibitor</p> Signup and view all the answers

    Which protease inhibitor is associated with a characteristic side effect of a 'buffalo hump'?

    <p>Atazanavir</p> Signup and view all the answers

    What is the role of nucleoside and nucleotide reverse transcriptase inhibitors (NRTIs) in HIV treatment?

    <p>Inhibiting HIV reverse transcriptase</p> Signup and view all the answers

    What is a common side effect of protease inhibitors when used chronically?

    <p>Fat redistribution</p> Signup and view all the answers

    Which enzyme system is significantly involved in drug-drug interactions with protease inhibitors?

    <p>CYP450</p> Signup and view all the answers

    What mechanism do nucleoside/nucleotide reverse transcriptase inhibitors employ to inhibit HIV replication?

    <p>Act as false substrates leading to chain termination</p> Signup and view all the answers

    What prodrug is a nucleotide analogue used in HIV treatment?

    <p>Zidovudine</p> Signup and view all the answers

    What is a potential adverse effect of inhibiting mitochondrial DNA polymerase?

    <p>Toxicities in certain tissues</p> Signup and view all the answers

    What is the role of integrase strand transfer inhibitors in HIV therapy?

    <p>Inhibit integration of viral DNA into host genome</p> Signup and view all the answers

    Which of the following drugs is classified as a nucleoside analogue used in HIV treatment?

    <p>Tenofovir</p> Signup and view all the answers

    What is a major consideration when using direct-acting antivirals (DAAs) for HCV treatment?

    <p>Utilization of multiple drug classes concurrently</p> Signup and view all the answers

    Study Notes

    Objectives

    • Identify potential drug targets in viral infections
    • List antiviral agents for human viral infections (HIV, HSV, respiratory and hepatic viral infections)
    • For each drug:
      • Explain its mechanism of action
      • Describe clinically-relevant pharmacokinetics
      • Identify major adverse effects

    Viral Structure and Replication

    • Viruses are not cells; they lack cell walls and membranes
    • Viruses utilize the host cell's metabolic processes
    • Symptoms often appear when most viral particles have replicated

    Rise of Antivirals

    • Number of approved antiviral drugs has increased over time, particularly since the 1980s
    • Research into viral replication and better understanding of viruses drives development of new drugs

    Points of Attack

    • Block viral binding or entry to host cells
    • Prevent viruses from making new RNA copies
    • Interfere with the production of proteins required to form new viruses

    Antiretroviral Therapy for HIV Infection

    • Averts millions of HIV/AIDS deaths through treatment
    • Prolongs life expectancy by years
    • Decreases transmission risk

    Antiretroviral Therapy Classification

    • Nucleoside and nucleotide reverse transcriptase inhibitors (NRTIs)
    • Non-nucleoside reverse transcriptase inhibitors (NNRTIs)
    • Protease inhibitors
    • Integrase strand transfer inhibitors (INSTIs)
    • Chemokine receptor antagonists
    • Fusion inhibitors

    Non Nucleoside Reverse Transcriptase Inhibitors (NNRTIs)

    • Chemically diverse compounds that bind near the catalytic site of reverse transcriptase
    • Efavirenz (oral) is an example
    • Potential adverse effects include skin rash, gastrointestinal disturbances, and vivid dreams

    Effect on CYP450 Enzymes

    • Some antivirals are potent inhibitors of CYP2B6
    • This can lead to drug accumulation, potentially causing increased toxicity
    • Important to consider drug-drug interactions

    Enzyme Inhibition and Induction

    • Some antiviral drugs inhibit drug metabolism, resulting in drug accumulation
    • Some antivirals induce the expression of drug metabolism enzymes, leading to decreased drug effectiveness

    Nucleoside and Nucleotide Reverse Transcriptase Inhibitors (NRTIs)

    • Prodrugs activated by host cell phosphorylation
    • Lack a 3'-hydroxyl group
    • Incorporated into growing DNA chains, triggering premature chain termination
    • Examples include Zidovudine and Tenofovir

    Adverse Effects

    • La ctic acidosis, hepato-steatosis, and lipodystrophy are potential adverse effects of some antiretroviral therapies.
    • Mitochondrial DNA polymerase inhibition can cause toxicity

    Protease Inhibitors

    • Inhibit viral proteases, preventing the maturation of viral proteins into infectious virions
    • Atazanavir, Boceprevir, and Daclatasvir are examples

    Adverse Drug Reactions

    • Fat redistribution (buffalo hump, abdominal fat accumulation, limb wasting) can occur with some antivirals

    Integrase Strand Transfer Inhibitors (INSTIs)

    • Inhibit viral DNA insertion into host genome
    • Reduced bioavailability when taken with antacids

    Entry Inhibitors/CCR5 Antagonists

    • Block CCR5 coreceptor to prevent HIV entry
    • Effective only for R5 strains
    • Maraviroc is an example

    Fusion Inhibitors

    • Block the conformational change of gp41 to prevent HIV membrane fusion with CD4 cell membrane
    • Enfuvirtide is an example

    Treatment of Herpes Virus Infections

    • Acyclovir (oral, IV, topical)

    Treatment of Respiratory Viral Infections

    • Influenza A and B, respiratory syncytial virus, SARS-CoV-2, COVID-19

    Neuraminidase Inhibitors

    • Oseltamivir (prodrug), activated by metabolic processes
    • Inhibits viral neuraminidase enzyme
    • Prevents release of new virions and prevents spread

    Endonuclease Inhibitors

    • Baloxavir, Favipiravir
    • Inhibit endonuclease activity to prevent viral gene transcription and replication

    Ribavirin

    • Synthetic guanosine analog which inhibits RNA and DNA replication for various RNA and DNA viruses (RSV, Hep-C)
    • Contraindicated in pregnancy

    Treatment of Hepatic Viral Infections

    • Hepatitis B and Hepatitis C

    Treatment of Hepatitis B

    • Interferons, usually with NRTIs
    • Pegylated forms last longer

    Hepatitis C Treatment Strategy

    • Improved response to direct-acting antivirals (DAAs)
    • Effective in different genotypes

    Direct-Acting Antivirals

    • Target different parts of the HCV polyprotein
    • Prevent replication and assembly
    • Examples include Glecaprevir, Ledipasvir, Sofosbuvir
    • Drug-drug interactions with CYP450 enzymes need consideration

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    Lecture 21 Antiviral Therapy PDF

    Description

    This quiz focuses on identifying potential drug targets in viral infections, particularly for common human viral infections like HIV and HSV. You'll explore various antiviral agents, their mechanisms of action, pharmacokinetics, and major adverse effects. Test your knowledge on the rise of antiviral therapies and their points of attack against viruses.

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