emtricitabine/tenofovir alafenamide
Descovy combines emtricitabine with tenofovir alafenamide into a single daily tablet from Gilead for HIV-1 infection and for pre-exposure prophylaxis (PrEP) in people at risk. Both drugs block the viral reverse transcriptase enzyme, stopping HIV from copying its genetic material into new virus particles.
This page is based on FDA prescribing information for emtricitabine/tenofovir alafenamide (DESCOVY) and MedlinePlus patient guidance for the emtricitabine–tenofovir alafenamide combination; the mechanism is explained in plain language, and analogies are used only where they stay accurate.
How it works
Explains what the medicine does in the body, not dosing, side effects, or safety.
An analogy
HIV is a burglar that needs to copy its blueprint before it can hide inside your cells. Emtricitabine and tenofovir alafenamide are like fake ink cartridges: when the virus tries to use them to photocopy its plans, the copies come out garbled and the burglary fails.
In simple terms
Emtricitabine and tenofovir alafenamide are two medicines that work together against HIV. Both are building-block look-alikes that the virus mistakes for the raw materials it needs to copy its own genetic material. Once the virus inserts one of these fake building blocks into its new DNA, the copy process stops. Taken together with other HIV medicines, the combination keeps the amount of virus in the blood very low, helping the immune system recover and reducing the chance of passing HIV to others. When used for PrEP in HIV-negative people at risk, the same mechanism blocks the virus before it can establish an infection.
In depth
Emtricitabine is a cytosine nucleoside analogue and tenofovir alafenamide (TAF) is a prodrug of tenofovir, an acyclic nucleotide analogue of adenosine monophosphate. Inside the cell, both are phosphorylated to their active diphosphate and diphosphate-like forms, which compete with the natural substrates deoxycytidine triphosphate and deoxyadenosine triphosphate for incorporation by HIV-1 reverse transcriptase. Once incorporated, they cause chain termination because they lack the 3'-hydroxyl group needed for the next phosphodiester bond. TAF achieves higher intracellular tenofovir diphosphate concentrations than tenofovir disoproxil fumarate at a lower dose, reducing systemic tenofovir exposure and associated renal and bone toxicity. The combination does not cure HIV but suppresses viral replication when used as part of combination antiretroviral therapy.
See it in motion
A schematic animation of the mechanism — simplified for clarity, not drawn to scale.
Both drugs block the viral reverse transcriptase enzyme, stopping HIV from copying its genetic material into new virus particles.
- Emtricitabine and tenofovir alafenamide are two medicines that work together against HIV.
- Both are building-block look-alikes that the virus mistakes for the raw materials it needs to copy its own genetic material.
- Once the virus inserts one of these fake building blocks into its new DNA, the copy process stops.
- Taken together with other HIV medicines, the combination keeps the amount of virus in the blood very low, helping the immune system recover and reducing the chance of passing HIV to others.
Target: HIV-1 reverse transcriptase
The viral enzyme that converts HIV's single-stranded RNA genome into double-stranded DNA, a step required for the virus to insert its genes into the host cell's chromosomes and make new virus particles.
Approved uses
Approved uses differ by country and change over time. Always follow your local prescribing information.
Approved uses in United States
FDA- DESCOVY is indicated in combination with other antiretroviral agents for the treatment of HIV-1 infection in adults and adolescent patients weighing at least 35 kg
Approved uses in United States
MedlinePlus- The combination of emtricitabine and tenofovir alafenamide is used to treat human immunodeficiency virus (HIV) infection
- Also used along with practicing safer sex to reduce the risk of HIV infection (pre-exposure prophylaxis)
Official sources
The statements on this page trace back to these records.
- U.S. Food and Drug Administration: emtricitabine/tenofovir alafenamide prescribing information
U.S. Food and Drug Administration
- MedlinePlus: emtricitabine and tenofovir alafenamide
MedlinePlus, U.S. National Library of Medicine
This page explains how the medicine works — it isn’t the patient leaflet. For anything that applies to you, read the leaflet that came with your medicine or ask your pharmacist.
MedUnfold provides educational content and is not medical advice. Always follow your local prescribing information and healthcare professional.