Published: 18 August 2015
People with HIV and hepatitis B virus (HBV) co-infection maintained HIV viral suppression, maintained or achieved HBV suppression and showed improvements in kidney and bone markers when they switched to a single-tablet regimen containing the integrase inhibitor elvitegravir and a new safer formulation of tenofovir. These findings were presented on a late-breaking poster at the Eighth International AIDS Society Conference on HIV Pathogenesis, Treatment, and Prevention (IAS 2015) last month in Vancouver.
Gilead Sciences’ tenofovir disoproxil fumarate (TDF, Viread) is one of the most widely used antiretroviral drugs for HIV and is a highly effective antiviral therapy for hepatitis B. It is a component of the Truvada coformulation – used for both HIV treatment and pre-exposure prophylaxis (PrEP) – and of the single-tablet regimens Atripla, Eviplera and Stribild. TDF is generally considered safe and well tolerated, but it causes a small amount of bone loss soon after starting treatment and can lead to kidney problems in susceptible people.
Tenofovir alafenamide (TAF) is a new pro-drug that delivers the active agent, tenofovir diphosphate, more efficiently to cells. TAF produces adequate intracellular drug levels with lower doses, which means lower concentrations in the blood plasma and less drug exposure for the kidneys, bones and other organs and tissues.
Phase 3 clinical trials presented at this year’s Conference on Retroviruses and Opportunistic Infections showed that TAF is as effective as TDF for previously untreated people, but has less detrimental effects on the kidneys and bones. Another phase 3 study presented at IAS 2015 showed that people who switched from a TDF-containing combo to a single-tablet regimen consisting of cobicistat-boosted elvitegravir, emtricitabine and TAF – essentially a new version of Stribild that replaces TDF with TAF – maintained undetectable viral load and saw improvements in kidney function and bone density.
Because tenofovir is active against HBV as well as HIV, it is important to test whether TAF and its co-formulations are safe and effective for people with both viruses.
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