Response from Dr. Sherer
Unfortunately, most people on ENF (enfurvitide or Fuzeon) do develop resistance that renders the drug less effective after 1-3 years, but this has more to do with the multi-drug resistant virus and the timing of the introduction of this drug than any particular weakness of this drug.
If that sounds like a complicated answer to a simple question, that's because it is. A person living with HIV who is on ENF has a complicated medical treatment history and some ART resistance. The answer to how long your current regimen remains effective, and whether or not you have developed ENF resistance, is complex, and much better answered by your doctor. I can offer some general observations to you, and suggest that you take them to your doctor to discuss.
First of all, the evidence is pretty good that ENF continues to add benefit to your treatment, even if you have developed some resistance and viremia, and even if you have been on ENF for a number of years, as in your case. In one study looking at the impact of stopping ENF in patients on failing ART regimens and with detectable viremia, there was a further increase in the viral load and fall in the CD4 cell count after ENF was discontinued.
On the other hand, ENF can be a difficult drug to take for 4 months due to twice daily injections and the itchy bumps that some patients experience. Many patients have asked their doctors to switch them to an alternative when one becomes available, and there are now many alternatives that are FDA approved. Their names are raltegravir, the new integrase inhibitor, miraviroc, the new entry inhibitor, and etravirine, the new second generation NNRTI.
Whether a switch would be a good idea for you is for you and your doctor to decide. In one recent study from Canada, 36 patients who were well suppressed on ENF for over 2 years were switched to the same regimen without ENF but with raltegravir, and 35/36 maintained full viral suppression, and the 36th patient had a viral load of 60 copies/ml. So if you are currently fully suppressed, that strategy might be an option for you.
But if you are not fully suppressed, a single drug switch would NOT be an option for you. If a change in your regimen were to be needed (as determined by you and your doctor), you would need a whole new regimen with three active drugs and one new class of drugs.
Whether either of the other two drugs would be useful in such a combination for you depends on the results of past resistance tests and the result of a new (and expensive) tropism assay - and again, only you and your doctor can make that determination. Unless you were part of the raltegravir or elvitegravir clinical trials, raltegravir is likely to be an active drug in your next regimen.
So, as you can hear, your next options are complicated, but there are many more options than just one year ago. Talk to your doctor about them.
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