New tenofovir formulation equally effective but safer

Paul Sax presenting at CROI 2015. Photo by Liz Highleyman, hivandhepatitis.com.

Paul Sax presenting at CROI 2015. Photo by Liz Highleyman, hivandhepatitis.com.

Story via NAM (@aidsmap)

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NAM is an award-winning, community-based organisation, which works from the UK. They deliver reliable and accurate HIV information across the world to HIV-positive people and to the professionals who treat, support and care for them.

Tenofovir alafenamide (TAF), a new formulation that has lower concentrations in the blood but reaches higher levels in cells, is as effective as the currently available version, tenofovir disoproxil fumarate (TDF). Furthermore, it has less detrimental effects on the kidneys and bones compared with TDF.

Tenofovir disoproxil fumarate (Viread) is one of the most widely used antiretroviral drugs. It is a component of the Truvada coformulation and the single-tablet regimens Atripla, Eviplera/Complera and Stribild. TDF is highly potent and generally safe and well-tolerated, but can cause kidney and bone problems in some patients.

TAF is a new pro-drug that delivers the active agent, tenofovir diphosphate, more efficiently to cells infected with HIV. TAF produces adequate intracellular 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.

Whereas cheaper, generic versions of tenofovir disoproxil fumarate will be available in many Western markets soon, TAF will be a new product exclusive to Gilead and protected by patent.

Data were presented comparing the Stribild coforumulation (elvitegravir, cobicistat, emtricitabine and TDF) with an alternative coformulation replacing TDF with TAF. Around 1700 previously untreated people took part in the studies in Europe, North America, Latin America and Asia.

After 48 weeks, the two regimens had similar high efficacy, showing that the TAF coformulation is non-inferior. Rates of viral suppression were over 90% in both arms of the study, irrespective of age, sex, race, HIV-1 RNA and CD4 cell count. Fewer than 1% had evidence of primary resistance mutations in either arm.

Overall rates of side-effects and serious adverse events did not differ.

Kidney-related adverse events were examined in more detail. Compared with TDF, TAF had no discontinuations due to renal adverse events, significantly smaller decreases in eGFR and significantly less proteinuria, albuminuria and tubular proteinuria.

In relation to bone health, TAF has significantly less impact on spine bone mineral density (26% lost at least 3%, compared to 45% in the TDF group) and on hip bone mineral density (17% lost at least 3%, compared to 50% in the TDF group).

The coformulation studied here has been submitted to regulators in the USA and Europe for licensing.

Gilead is also developing a coformulation of TAF and emtricitabine, to replace Truvada. This may also be considered for use as pre-exposure prophylaxis (PrEP).

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