SIGN-ON this week – community letter to Gilead on new version of tenofovir

UPDATE (July 2013): Approximately 300 organisations and individuals signed this letter, even though the side on period was short. i-Base will post an update on this issue shortly.


Please could community organisations and individuals consider signing on to this letter to Gilead Sciences, the company developing this compound.


A new version of tenofovir (called tenofovir alafenamide, abbreviated to TAF) is already looking very promising compared to the current version (TDF – tenofovir disoproxil fumerate). It looks more effective (with an additional 0.5 log viral load reduction in treatment naive patients) and it does this using a lower dose.

The new version gets higher concentrations of the active drug inside cells where it is really needed and does this with much lower levels circulating in the blood – so may reduce concerns about kidney and bone toxicity.

Last week we reported the first resistance data on TAF which was important for showing that these higher intracellular drug levels have the potential to overcome some common resistance mutations associated with the current tenofovir (TDF).

However, Gilead are currently priorising research into TAF in coformulations with other ARVs – and this will limit access to use that involves other drugs manufactured by Gilead or their partners. Although this is still early days, TAF is already included in coformulations that are in phase 3 studies, so it is important to influence this process as early as possible.

The option to use TAF as an individual drug for people with existing drug resistance is important for wealthy and resource-limited countries and settings.

This is a compound that Gilead may already have been sitting on for many years for commercial reasons, only kick-starting development as tenofovir approached the end of its patent license.

Current trials including TAF are listed at this link to the clinicaltrials.gov registry.


Forward: Sign-on request for community letter to Gilead

HIV i-Base, Treatment Action Group (TAG) and Project Inform, have drafted a  letter urging Gilead Sciences to develop a stand-alone formulation of tenofovir alafenamide fumarate (TAF), an experimental prodrug of the nucleotide reverse transcriptase inhibitor tenofovir.  We are asking organisations and individuals to sign-on to this if they agree.

We are concerned that Gilead’s current development plans, as we understand them, might limit TAF to a component of fixed-dose combinations (FDCs) only. Though this exemplifies Gilead’s leadership in manufacturing simplified and convenient innovator company antiretroviral (ARV) regimens, it overlooks the potential importance of a stand-alone TAF formulation for use in combination with a variety of non-Gilead agents—notably low-cost generic ARVs in low-, middle-, and high-income countries—and as a component of tailored regimens for treatment-experienced people living with HIV, including those with mutated strains conferring resistance to tenofovoir disoproxil fumarate (TDF).

To read the full letter and join this effort, please go to:
To sign on please go to:

Further information

For further information about TAF see these reports from early studies.

Higher intracellular concentrations with tenofovir alafenamide (TAF) overcomes K65R and other key NRTI resistance in vitro – HTB July/August 2013, pre-press draft

ARV pipeline: dolutegravir, TAF (GS-7340), MK-1439 and cenicriviroc: reports from CROI 2013 – Report from CROI 2013 in HTB March/April 2013

The antiretroviral pipeline 2012 – i-Base/TAG pipeline report, July 2012

Tenofovir prodrug: 10 day monotherapy study sets dose at 25 mg for easier coformulation – Report from CROI 2012 in HTB March/April 2012

New antiretrovirals: dolutegravir, entry inhibitor (BMS-663068) and tenofovir pro-drug (GS-7340) – Report from CROI 2011 in HTB March April 2011