Inhibitors of Viral Nucleic Acid Synthesis
This broad category includes drugs that block the key enzymes responsible for copying viral genetic material.
- Viral DNA polymerase inhibitors. This is the main group of drugs disrupting viral DNA synthesis using a DNA template. A classic representative is acyclovir, a guanosine structural analogue that incorporates directly into herpesvirus DNA, terminating its elongation. Another important drug, foscarnet, inhibits DNA polymerase in both herpesviruses and HIV.
- Reverse transcriptase inhibitors. Reverse transcriptase is essentially an RNA-dependent DNA polymerase. Drugs in this group block a unique process: DNA synthesis using a viral RNA template. This property makes them the foundation of HIV therapy. The group is subdivided into nucleoside reverse transcriptase inhibitors (NRTIs, such as zidovudine and lamivudine) and non-nucleoside reverse transcriptase inhibitors (NNRTIs, such as efavirenz).
Note: Although reverse transcriptase is biologically a type of DNA polymerase, educational classifications often treat these two groups separately as distinct classes.
Drugs Acting on Other Replication Stages
If therapy requires a drug that is not a polymerase inhibitor, logical alternatives include medications that block viral entry or particle assembly.
- HIV protease inhibitors. This distinct group of drugs does not affect DNA synthesis. They act at a later stage: post-translational processing. By blocking the protease enzyme, drugs such as ritonavir disrupt the proper maturation of viral proteins.
- Fusion inhibitors. These target the earliest stage of infection. A representative of this group, enfuvirtide, specifically blocks HIV entry into the target cell. It is crucial to remember that these drugs are highly specific and completely ineffective against other pathogens, such as influenza viruses.
Spectrum of Activity in Influenza A Treatment
For rational pharmacotherapy, it is essential to differentiate specific anti-influenza agents from other drug classes (such as antiretrovirals, which are ineffective against influenza).
Agents with proven clinical efficacy against the influenza virus include:
- Neuraminidase inhibitors. The primary representative is oseltamivir. Its mechanism of action involves disrupting the release of newly formed virions from the infected host cell.
- M2 channel blockers. This group includes rimantadine. It acts inside the cell by disrupting viral uncoating. The drug is specific exclusively to influenza A, though high resistance rates are noted in modern clinical practice.
- Interferon inducers. Agents such as kagocel stimulate the production of endogenous interferons in the patient's body. They are successfully used for both treatment and prophylaxis.
- Broad-spectrum agents. A prime example is ribavirin. It inhibits both viral RNA and DNA synthesis. It exhibits high activity against the influenza virus, but its clinical use is limited by marked toxicity.