All PrEP is not the same - know what you're taking

[ErosWired]

PrEP, or Pre-Exposure Prophylaxis, is usually accomplished via a prescription for Truvada (tenofovir). But not all Truvada is the same. A 2015 study funded by Gilead, the makers of Truvada, compared the safety and effectiveness of tenofovir disoproxil fumarate (the standard formulation for Truvada) and the newer tenofovir alafenamide. The results found that Tenofovir alafenamide showed equal or slightly better results in viral control and significantly less risk of renal and bone toxic effects. tenofovir disoproxil fumarate, taken over the long term, predisposes the user to the possibility of kidney disease, and bone loss that can result in more frequent breaks.

If you're on PrEP, take a close look at the formulation of the version you're taking. If it contains tenofovir disoproxil fumarate, ask your doctor if there's an alternative available containing tenofovir alafenamide. Both should be coformulated with other drugs like cobicstat, elvitigravir, and emtricitabine, but it's the tenofovir you need to look at.

 

Which all just goes to prove that there ain't no free lunch, men.

 

If you want to read the study yourself, you can find it at: http://www.natap.org/2015/HIV/PIIS014067361560616X.pdf

[fillmyholeftl]

4 hours ago, ErosWired said:

PrEP, or Pre-Exposure Prophylaxis, is usually accomplished via a prescription for Truvada (tenofovir). But not all Truvada is the same. A 2015 study funded by Gilead, the makers of Truvada, compared the safety and effectiveness of tenofovir disoproxil fumarate (the standard formulation for Truvada) and the newer tenofovir alafenamide. The results found that Tenofovir alafenamide showed equal or slightly better results in viral control and significantly less risk of renal and bone toxic effects. tenofovir disoproxil fumarate, taken over the long term, predisposes the user to the possibility of kidney disease, and bone loss that can result in more frequent breaks.

If you're on PrEP, take a close look at the formulation of the version you're taking. If it contains tenofovir disoproxil fumarate, ask your doctor if there's an alternative available containing tenofovir alafenamide. Both should be coformulated with other drugs like cobicstat, elvitigravir, and emtricitabine, but it's the tenofovir you need to look at.

 

Which all just goes to prove that there ain't no free lunch, men.

 

If you want to read the study yourself, you can find it at: http://www.natap.org/2015/HIV/PIIS014067361560616X.pdf

If I am not mistaken... tenofovir alafenamide (the new formulation) is not yet approved by FDA/CDC for PrEP. It is used in various treatment regimens 

[barecub85]

6 hours ago, fillmyholeftl said:

If I am not mistaken... tenofovir alafenamide (the new formulation) is not yet approved by FDA/CDC for PrEP. It is used in various treatment regimens 

This is correct. The new version of Truvada that contains tenofovir alafenamide fumarate (TAF) is called Descovy, and hasn’t been FDA approved for use as PrEP yet. The clinical trial looking to show the real-world efficacy of Descovy as PrEP is still ongoing (source: I’m working on the trial).

The study linked by OP is of a four-drug combo pill being used as a single-tablet regimen for treatment of HIV, not as PrEP. The brand name of that drug is Genvoya.

Edited October 4, 2018 by barecub85

[ErosWired]

Sorry for the confusion - My error was in assuming that the Truvada used for PrEP would be, or could be, the same formulation as in the Genvoya I’ve been taking for two years. Which begs the question: If the FDA considers it safe and effective enough for patients to take as ART, why isn’t it considered safe and effective for use as PrEP? Perhaps @barecub85 could shed some light on this?

[Usccocksucker]

41 minutes ago, ErosWired said:

Sorry for the confusion - My error was in assuming that the Truvada used for PrEP would be, or could be, the same formulation as in the Genvoya I’ve been taking for two years. Which begs the question: If the FDA considers it safe and effective enough for patients to take as ART, why isn’t it considered safe and effective for use as PrEP? Perhaps @barecub85 could shed some light on this?

It’s because it’s not said to be effective until it’s shown to be effective in clinical trial for that specific use. It helps to understand the chemistry a bit.

 

Tenofovir alafenamide (TAF) is slightly different from tenofovir disoproxil fumarate (TDF). Both of them have tenofovir, the main active part, bound to another molecule. But that other molecule is different in both cases. Why is tenofovir bound to another molecule anyway? Well, tenofovir by itself doesn’t get absorbed well. By adding these extra bits to the tenofovir molecule, the absorption of tenofovir is increased. And when TDF and TAF get inside the cells, they both get converted to the active form of plain, old tenofovir. We call TAF and TDF “prodrugs” — drugs that aren’t active until they’re converted in the body to their active form.

 

Okay, so we’ve established that tenofovir doesn’t get absorbed as well as TDF and TAF, so that’s your first clue that, despite them all having the same main active bit, they don’t all have the same efficacy and safety. If the drug can’t get to where it needs to work, it’s not going to be very effective.

 

Now what’s the difference between TAF and TDF? Compared to TDF, TAF prefers to go into cells instead of staying in your plasma. This is potentially good for a couple of reasons. (1) That’s where the action happens — more drug in the cells can be good because the step in the viral lifecycle that tenofovir interferes with happens inside of cells. (2) Tenofovir can be tough on the kidneys and can have effects on bone mineral density. If the tenofovir is in the cell as opposed to in the plasma, there is less chance for the tenofovir to hurt your kidneys or bones. Clinical trials in the setting of HIV treatment showed that TAF was just as good at achieving viral control as TDF (showing efficacy), but it also had fewer adverse effects (showing this improved safety).

 

So why can’t we use TAF for PrEP if it’s so great? Well, because there isn’t enough data on it’s use in prevention. In prevention, you’re blocking the virus from being able to establish an infection, so you want to be sure that TAF gets to the specific tissues (genital tissues/mucosal tissues) where HIV infection starts as good or better than TDF. This is the part that’s not as clear yet, though there are studies being done that look promising.

 

But until there’s sufficient data to gain FDA approval for TAF to be used for PrEP (in combination with emtricitabine), no provider will write for Descovy for PrEP, and perhaps more importantly, no insurance company will reimburse for Descovy for PrEP.

[punaman]

My husband takes Genvoya. Much better than the previous meds he took for years.