This part-1 includes: 1. General structural features of viruses 2. Life cycle of virus, in general 3. Stages of life cycle of viruses at which antiviral drugs act 4. Classification of antiviral drugs on the basis of  Viruses against which they act  MOA of Antiviral drugs and  Chemical structure

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Antiviral Drugs- Part 1
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2. This part-1 includes:
1. General structural features of viruses
2. Life cycle of viruses, in general
3. Stages of life cycle of viruses at which antiviral
drugs act
4. Classification of antiviral drugs on the basis of
Viruses against which they act
MOA of Antiviral drugs and
Chemical structure

3. VIRUSES
Viruses are obligate intracellular pathogens.
Capsid
Capsomeres
DNA or RNA
Envelope
Spike
Tegument
General Structural Features of Virus:

4. The life cycle of viruses differs greatly between species but there are six common
basic stages. These are:
Virus life cycle
1. Attachment to a host cell
2. Viral entry into host cell (Viral penetration)
3. Release of viral genes and possibly enzymes into the host cell (Uncoating)
4. Replication of viral components using host-cell machinery (involve Reverse
transcription for some RNA viruses) (Reverse transcription is the synthesis of DNA
from RNA).
5. Assembly of viral components into virions (Maturation) (A virion is an intact
viral particle that has ability to infect a new host cell).
6. Release of virions to infect new host cells:
The newly formed virions are released from the cell by:
1) sudden breaking of the cell membrane (cell lysis), or
2) budding through the membrane to form virus envelope
The released virions are now ready to infect the other host cells.

5. Antiviral Drugs
Antiviral drugs are used to treat viral infections
Antiviral drugs act by arresting the viral life cycle at various
stages such as:
1. virus attachment to host cell receptors, penetration, or uncoating.
Uncoating is the release of viral genome in the host cell.
2. inhibiting virus-associated enzymes such as Reverse transcriptase and
others.
3. inhibiting viral transcription and translation
4. interfering with viral regulatory proteins.
5. interfering with glycosylation, phosphorylation, sulfation, and so on.
6. interfering with the assembly and release of virions

6. Classification of Antiviral Drugs
Based on viruses against which a drug act:
1. Anti-Herpes virus: Acyclovir, Valacyclovir, Famciclovir, Ganciclovir,
Penciclovir, Cidofovir, Valganciclovir, Idoxuridine, Trifluridine, Foscarnet,
Fomivirsen
2. Anti-Influenza virus: Amantadine, Rimantadine, Oseltamivir, Zanamivir
3. Anti-Hepatitis virus/Nonselective antiviral drugs:
Pegylated interferon alfa 2A, Pegylated interferon alfa 2B
Primarily for hepatitis B: Tenofovir, Entecavir, Lamivudine, Adefovir dipivoxil
Primarily for hepatitis C: Ribavirin, Sofosbuvir
4. Anti-Retrovirus (Anti-HIV)
CCR5 receptor inhibitor: Maraviroc
Entry (Fusion) inhibitor: Enfuvirtide
Integrase inhibitor: Raltegravir
Nucleoside reverse transcriptase inhibitors (NRTIs): Zidovudine (AZT),
Didanosine, Stavudine, Lamivudine, Abacavir, Emtricitabine, Tenofovir (Nt RTI)
Nonnucleoside reverse transcriptase inhibitors (NNRTIs): Nevirapine,
Efavirenz, Delavirdine
Protease inhibitors: Ritonavir, Atazanavir, Indinavir, Nelfinavir, Saquinavir,
Amprenavir, Lopinavir, Darunavir, Tipranavir, Fosamprenavir.

7. Classification of Antiviral Drugs According to MOA
1. Agents Inhibiting Virus Attachment, Penetration, and Early Viral Replication:
Amantadine, Rimantadine, Interferon
2. Neuraminidase Inhibitors: Oseltamivir, Zanamivir
3. Agents Interfering with Viral Nucleic Acid Replication:
Acyclic Nucleoside Analogs: Acyclovir, Valacyclovir, Cidofovir, Famciclovir,
Ganciclovir, Adefovir dipivoxil,
Conventional Nucleoside Analogs: Idoxuridine, Ribavirin, Trifluorothymidine,
Vidarabine, Cytarabine
Nonnucleoside Analogs: Fomivirsen Sodium, Foscarnet Sodium, Boceprevir and
Telaprevir
4. Agents Affecting Translation by the Ribosome: Methisazone
5. Antiretroviral (Anti-HIV) Agents Including Protease Inhibitors
(a) Nucleoside reverse transcriptase inhibitors (NRTIs): Zidovudine (AZT),
Didanosine, Stavudine, Lamivudine, Abacavir, Emtricitabine, Tenofovir (Nt RTI)
(b) Nonnucleoside reverse transcriptase inhibitors (NNRTIs): Nevirapine,
Efavirenz, Delavirdine
(c) Protease inhibitors: Ritonavir, Atazanavir, Indinavir, Nelfinavir, Saquinavir,
Amprenavir, Lopinavir, Darunavir
(d) Entry (Fusion) inhibitor: Enfuvirtide
(e) CCR5 receptor inhibitor (Chemokine Receptor Binders): Maraviroc
(f) Integrase inhibitor: Raltegravir

8. Chemical classification of antiviral agents
Purine nucleoside analogue: Acyclovir, Ganciclovir, Famciclovir, Valacyclovir, etc
Pyrimidine nucleoside analogue: Cidofovir, Vidarabine, Idoxuridine, Trifluridine,
Cytarabine, Zalcitabine, Zidovudine, Stavudine
Adamantane amines: Amantadine, Rimantadine
Thiosemicarbazide: Methisazone
Peptide analogue: Saquinavir, Ritonavir, Indinavir
Triazole carboxamide: Ribavirin
Sialic acid mimetic: Oseltamivir, Zanamivir
Interferons: Pegylated interferon alfa 2a, Pegylated interferon alfa 2b
Miscellaneous: Gamma globulin, Rifamycin

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Antiviral Drugs- Part 2