| What is Tenofovir Alafenamide Fumarate?
- Tenofovir alafenamide fumarate (TAF), formerly known as GS 7340, is an HIV medication. It is in a category of HIV medicines called nucleotide reverse transcriptase inhibitors (NRTIs). TAF prevents HIV from entering the nucleus of healthy CD4 cells. This prevents the cells from producing new virus and decreases the amount of virus in the body.
- TAF is an experimental version of tenofovir and differs somewhat from tenofovir disoproxil fumarate (TDF), the active ingredient in Viread and a component of Truvada, Atripla, Complera and Stribild. TAF can be taken at a dose that is ten times lower than the amount of Viread that needs to be taken, which should make it even easier to combine in tablets with other HIV medications, while potentially reducing the risk of certain side effects associated with tenofovir treatment.
- TAF is being developed by Gilead Sciences. It is being studied as a part of fixed-dose combination tablets, including an experimental version of Stribild.
What is already known about TAF?
- Early research suggests that, like Viread, TAF only needs to be taken once a day. As a component of the experimental version of Stribild, the TAF dose is 10 mg (whereas the dose of TDF in the approved version of Stribild is 300 mg).
- Like TDF, TAF might interact with other medications, including those used to treat HIV. It is important that your personal physician and/or the research nurse or study investigator be aware of all drugs you are taking, including those you buy without a prescription.
- Because TAF contains tenofovir, it is not expected to be active against HIV resistant to Viread or the TDF component of Truvada, Atripla, Complera or Stribild.
- TAF is being studied in combination with other HIV medications, notably as a component of fixed-dose combination tablets.
- Like TDF, TAF is also likely to be active against the hepatitis B virus (HBV), the virus responsible for hepatitis B. This is potentially good news for people living with both HIV and HBV who require treatment for both infections. However, this will require careful planning with a health care provider; abruptly stopping regimens containing either TDF or TAF can cause liver disease to "flare" and damage the liver. Careful monitoring of liver enzymes during and after using this drug will be important.
What has been learned from clinical trials?
- In early Phase II studies, researchers identified a TAF dose that is ten times lower than TDF and provides greater antiviral efficacy. The smaller milligram size of TDF should enable the development of new fixed-dose combinations and single-tablet regimens for HIV therapy that are not feasible with Viread.
- Advanced Phase II and III clinical trials of TAF, as a part of fixed-dose combination tablets, are being conducted by the company. One such tablet, the experimental version of Stribild, contains TAF, Emtriva (emtricitabine), the novel booster cobicistat and the experimental integrase inhibitor elvitegravir. Early (24-week) data from one study of the experimental Stribild regimen suggests it is no less effective than the approved version of Stribild. A second tablet, being developed in conjunction with Janssen Therapeutics, contains TAF, emtricitabine, cobicistat and the protease inhibitor Prezista (darunavir).
What is known about side effects?
- TAF's side effect profile has not been fully determined. In Phase II studies, TAF was well tolerated. As a component of the experimental Stribild tablet, the side effect profile was no different after 24 weeks compared with the approved version of Stribild.
Who should not take TAF?
- It is not known whether TAF will harm an unborn baby. It is very important to treat HIV/AIDS during pregnancy to reduce the risk of infecting your baby. Talk to your doctor about your treatment options.
- It is not known whether TAF passes into breast milk and what effect it may have on a nursing baby. To prevent transmission of the virus to uninfected babies, it is recommended that HIV-positive mothers not breast-feed.
Where can I learn more about clinical trials of TAF?
- If you would like to find out if you are eligible for any clinical trials that include TAF, visit ClinicalTrials.gov, a site run by the U.S. National Institutes of Health. The site has information about all HIV-related clinical studies in the United States. For more info, you can call their toll-free number at 1-800-HIV-0440 (1-800-448-0440) or email firstname.lastname@example.org.