Community request Gilead to study and develop separate formulation of new tenofovir prodrug

Polly Clayden, HIV i-Base

In June of this year close to 300 organisations and individuals signed on to a letter to Gilead Sciences raising the importance of developing a stand-alone formulation of tenofovir alafenamide fumarate (TAF).

TAF is a prodrug of the tenofovir disoproxil fumarate (TDF) and is currently under development by the company. The letter was drafted by HIV i-Base, Treatment Action Group (TAG) and Project Inform who asked organisations and individuals to sign-on to this letter if they agreed. Many did and within a week the letter that went to Gilead included almost 300 signatures.

We are concerned that Gilead’s investigation plan will limit TAF to a component of fixed dose combinations (FDCs) only. Based on our communications with senior Gilead staff, and current trial listings on the registry, we understand that the regulatory plans for TAF are:

  • FDC: elvitegravir/cobicistat/FTC/TAF; (10 mg TAF)
  • FDC: darunavir/cobicistat/FTC/TAF; (10 mg TAF)
  • a dual formulation of FTC/TAF (possibly, but not yet decided).

It seems that a stand-alone formulation of TAF is not part of the plan for the drug. This approach overlooks the importance of a stand-alone TAF for use in combination with a variety of non-Gilead drugs – notably low-cost generic ARVs in low-, middle-, and high-income countries. It also ignores the needs of people who have resistance to tenofovir TDF and other NRTI mutations that the new formulation may be able to overcome.

The authors of the letter met with representatives from Gilead at IAS but we remain disappointed by the company’s lack of commitment to developing a stand-alone version of TAF and lack of clarity as to what dose of TAF the combination product with FTC will include.

An interaction with the booster cobicistat means TAF can be used at 10 mg. In order to have enough information to use it in other regimens – including generic FDCs with non-boosted ARVs – TAF also needs to be investigated and approved at a dose of 25 mg.

As we go to press we are once again writing to Gilead and will also issue a public statement with the progress of our discussions.

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